# Thread Mic and Internal Threading



## gun410 (Sep 10, 2019)

Hello,

I am a fairly new to machining and even newer to a lathe. I have a G0602 10x22 lathe and I need to machine an endcap to fit on to a previously made brake (for a forum 1 suppressor build). I have 2 brakes made so far, i checked the pitch diameter with wires while threading the brake but they were very difficult to hold and get a good reading. I have a thread mic coming tomorrow that i'll be able to get the exact pitch diameter. But I have not internal threaded before and i've heard people say opposite things and i just want to grasp it more before i try it. I've watched alot of videos and read though quite a few threads on internal threading, and i have a couple questions that may be simple but I'm a newbie

Is the cross slide better for controlling depth than the compound for internal threading?
Once my thread mic comes and i get the exact pitch diameter can that help me for cutting the internal thread?
For pitch diameters there is around .005 tolerance is it better to be on the tighter or looser side?
Also for bore diameter for threading i know to use the minor diameter of the threads but once again there is .012 range to the minor


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## mikey (Sep 10, 2019)

I'll start this off and the other guys can come in and correct me.

I prefer to use the cross slide for internal threading. It is much simpler to control my depths of cut that, quite often, are very light. I usually use either HSS or solid carbide threading tools that enable very light depths of cut. The reason this matters is when producing precision fits being able to cut what you dial in is important. Inserts can do precision work but you have to know how to use them. I usually only use inserts when I have to go deep.
A thread mic helps with internal threading in a round about way. The mic will allow you to cut the male thread with precision,  and this allows you to fit the female thread to that male thread. It otherwise does not help with internal threading directly.
With regard to going for tighter or looser in the tolerance range, let me try to clarify this another way. YOU determine the class of fit you desire. If you need a okay fit and can tolerate a bit of slop or slack then a class 2 fit will do. This is what you get from a hardware store nut and bolt; its that kind of fit. If you want a class 3 fit then you're talking about a precision fit; the nut threads on with no slop or play. It may be snug, depending on how good you are at cutting to fit. A really good class 3 fit nut will thread onto the male thread with a little effort but zero play; you can feel the thread engaging but it is NOT a free-running fit. This class 3 fit requires the male OD to be turned within a specific diameter tolerance range and it also requires the female ID to also be within a specific tolerance range. Then you turn the male thread so that the pitch diameter falls inside the pitch diameter range for a class 3 thread. Once you get that, you turn the female thread to produce the fit that you require. This is the practical way to do this and is the way I would suggest you proceed; it allows you to use the male part to fit the female part.
As to your final question, see above. You *bore* the female part *to the tolerance fits for the class thread you need.* When you do this, shoot for the middle of the range but as long as you are anywhere inside this range you should be okay.
I know this sounds straightforward but turning to tolerance ranges requires that you be able to hit specific inside and outside diameters. Class 2 fits are usually not too difficult; Class 3 fits require a fair amount of skill, especially boring. You will find that doing precision machining for close fits is going to be challenging with inserted carbide tooling. HSS turning and threading tools will enable you to work with greater precision at these levels of fits, and solid carbide boring and threading bars will really help on the inside; in my opinion, Micro 100 makes the finest tools for this kind of work.

My best advice is to focus on learning to turn and bore accurately. Obtain the tools you need to do this, including telescoping gauges and micrometers if you don't yet have them so you can learn to bore with control. If you can grind HSS turning and threading tools, that will help a lot. If you must use inserts then learn how to control your cuts to hit very tight tolerances.


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## gun410 (Sep 10, 2019)

My Brown and Sharp 153 14-20 tpi thread mic came in and my buddy brought over his Chinese screw mic with the changing anvils 0"-1" and for whatever reason the chinese mic was reading lower values. For my .9375 X 16 tpi brakes I measured them and got .897" and .900 for pitch diameters which is bigger than the chart above but the other thread mic had a little lower numbers that fit into the pitch diameters range.

I actually ordered a Micro 100 threading bar after breaking my other one a couple days ago. I have a small piece of 17-4 in the lathe that i have bored to .875 the size needed for 15/16" x 16tpi according to http://www.harveytool.com/secure/Content/Documents/Tap_Drill_Chart.pdf but the only ID threading tool i have is a left hand shars brazed carbide internal threading and im waiting for my micro 100 to show up.


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## mikey (Sep 10, 2019)

Okay, let's back up a little bit. I suggest that you not go with tap/drill charts for anything you do with cutting threads on a lathe. Use the chart I'm attaching below. Let's walk through this a little so I can show you how the chart is used. I'll assume we are cutting for a class 3, 15/16-16 thread.




The first  thing you notice is that the material you're working with is not listed. This is because thread form is thread form and they assume you know how to cut it.

For the male thread, note that you have to turn the OD to between 0.9375 - 0.9281". You have a 0.0094" range to hit this OD. Once you get the OD somewhere inside this range, cut your threads until the pitch diameter that you get with your thread mic falls inside the listed range, 0.8969 - 0.8932". You have a 0.0037" range that your thread pitch has to fall in to and this produces a class 3a (*a* is external thead, *b* is internal thread), 15/16-16 thread.

For the female class 3b thread, you must bore the work piece to an ID between 0.8700 - 0.8783". Since you cannot measure pitch diameter inside the female thread directly, you have to estimate your thread depth of cut and when you get close you will use the male thread you cut above to test the fit until you get what you need. You can get pretty close for estimating the total depth of cut with the formula: 0.750/tpi. So, 0.750/16 = 0.0469". You check for fits well before you hit this depth of cut and when you get the fit you need, stop, and you're done.

When cutting large threads like this, tolerance ranges are big. When you get down to threads in the 1/4" range, tolerances are in the tenths so you need to be up to that level of work.

This chart is the most practical and useful chart I've seen. It tells you exactly what you need to get the threads you want and nothing more. Hobby guys need simple stuff like this.

Insofar as thread mic accuracy, this is calibrated with a mic standard that is pointed on one end and has a V on the other end to match the anvils. The reading you need to hit will be engraved on the mic standard. 

*EDIT:* I forgot to add that thread micrometers are intolerant of any sloppy habits we hobby guys might have. Before measuring, clean the work of burrs, chips and oil. Make sure the mic is centered on the work diameter - if you are off by even a little bit, the reading will be off. When working to very tight tolerance ranges, this matters because once the work piece is taken out of the lathe it is usually too late to cut deeper on it. Work with care and you should be fine.


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## gun410 (Sep 10, 2019)

mikey said:


> Okay, let's back up a little bit. I suggest that you not go with tap/drill charts for anything you do with cutting threads on a lathe. Use the chart I'm attaching below. Let's walk through this a little so I can show you how the chart is used. I'll assume we are cutting for a class 3, 15/16-16 thread.
> 
> View attachment 301933
> 
> ...


Thank you for all the info and the chart. For the brake thread i was originally planning on it being a class 2 thread but the brake i made has a pitch diameter in the class 3 tolerance about a thou over class b, the diameter before threading was .934” a little under nominal but still in the tolerance. I bored a hole .875" finish could've been better but i wasn't using cross feed because the lathe change gears were setup for threading. Anyways i attempted to single point thread it with a left hand tool lathe going in reverse and threading from inside to out. After the first couple passes the tip snapped and messed the threads up. I'll have to wait till my micro 100 boring bar comes until i can do anymore internal threading. I will also have to thread the tube and end cap but i hope that won't be to difficult, i have a Gold N DRO modified I-gaging dro that magnets to the lathe's ways and carriage for the x-axis. I'm planning on using the right hand micro 100 thread into the tube, zero the dro on the edge of the tube and thread towards headstock then disengage the half nut at .5". I saw this today and it looks like it would be a one all for Rh and Lh threading internal and external does anyone have experience with them? https://littlemachineshop.com/products/product_view.php?ProductID=3467&category=-147164245


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## jcp (Sep 10, 2019)

I use this insert for external threading (I don't have a holder for internal threading). Works fine.


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## mikey (Sep 10, 2019)

Okay. Screw cutting is not difficult once you understand what you are trying to achieve. Keep us posted on how it goes.

I have no experience with that LMS tool, sorry.


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## eeler1 (Sep 11, 2019)

One problem with threading stuff to go on the end of a barrel is that looser threads can work loose pretty quickly, recoil can be hard even on things that are tight.  If your brake wobbles it can really mess up accuracy.  Guess I'm suggesting the class 3 or thereabouts if you can do it.

Oh, and practice a few times on non-critical practice parts before you jump into the real deal.


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## higgite (Sep 11, 2019)

I’m not a gunsmith nor did I stay at a Holiday Inn last night, but I would think you would want as tight a thread as you can reasonably get for the sake of concentricity of brake and barrel. This seems like a good topic for the “Gunsmithing & Firearms” subforum in the “Weapons” forum. Might attract more attention from those who know about your specific application. And/or you might garner some good info from past threads, if you haven't already.

Edit: Will you be using a crush washer to align the brake and help prevent it from vibrating loose as eeler1 alluded to?

Tom


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## gun410 (Sep 12, 2019)

Concentrically is my main concern with threading the tube and endcaps. The muzzle comp was internally threaded with a 1/2-28 tap and fits on a threaded barrel, but the external threads were single point threaded, which I believe i did a good job on but i have concerns. Before i threaded the external 15/16 - 16 i turned it down to .934" a couple thousands below the nominal .9375" will that create slop in the threads? 

I wont use a crush washer on a suppressor because it will cause baffle strikes, I'll use a spacer toclock the brake and keep a flat area for the brake to tighten on.


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## mikey (Sep 12, 2019)

gun410 said:


> Before i threaded the external 15/16 - 16 i turned it down to .934" a couple thousands below the nominal .9375" will that create slop in the threads?



Should be okay. You are in the OD range for either a class 2 or 3 fit. It is good to know that the "fit" depends on both the OD and the pitch diameter being in your desired range. You can have a class 3a OD but if the pitch diameter you hit falls into the class 2a range, there may be some slop so I suggest you work carefully with the internal threading.


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## gun410 (Sep 13, 2019)

mikey said:


> Should be okay. You are in the OD range for either a class 2 or 3 fit. It is good to know that the "fit" depends on both the OD and the pitch diameter being in your desired range. You can have a class 3a OD but if the pitch diameter you hit falls into the class 2a range, there may be some slop so I suggest you work carefully with the internal threading.


Ok, I'm starting to catch on, the pitch diameter was .897 so on the high side of a class 3 fit, I'm just curious if having a pitch on the high side and the diameter on the lower side will negatively effect, but the pitch and od are still close to a class 3 fit. Since i still don't have the micro 100 threading bar I decided to work on the baffles. After putting a 2" long 1.5"D 17-4 blank in the 3 jaw, i center drilled, drilled the bore 1/4" and was going to drill 11/32" before reaming .375" but for some reason when i took the 1/4" bit out and tried drilling with the 11/32 bit it just wouldn't drill and was chattering quite a bit. I thought it was the drill bit but it seems sharp. My lathe is sittting on a tool cabinet that moves around a little so i know it's not leveled, I'm hoping that isn't causing the problem, because I would need to Re-make the break if the concentricy was off when drilling on my lathe.


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## mikey (Sep 13, 2019)

I'm not sure what is going on with your drill but if I had to guess, it is not sharpened well. The geometry may be off even if it is sharp. Are you using high quality drill bits?

I won't go into how to choose a reamer for a precision ID but I will tell you how I use one. I use a spotting drill, not a center drill. For my pre-reamer drill I choose the size carefully but it usually winds up pretty close to 0.003 - 0.005" under the reamer size. I spot the hole, drill with a drill that is one size smaller than the pre-reamer drill, then I use the pre-reamer drill. Then I use the reamer. The reason for this sequence is to debulk the hole with maximum accuracy and then skim cut it pretty straight with the pre-reamer drill; this then allows the reamer a decent chance of cutting evenly. Ideally, and especially on a critical work piece that must be concentric and true, I will pre-drill small, then bore the hole to the pre-reamer size before reaming. Drills make holes but they are not round and they are not straight. A reamer will follow that not straight hole and it will cut a bent hole that is on size. *Remember that if the reamed hole must be dead straight, you must bore it straight; you cannot drill it straight.*

Insofar as concentricity is concerned, as long as you do not remove the work piece from the 3 jaw you should be fine. Remove it and it will take a 4 jaw to get it realigned.


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## gun410 (Sep 14, 2019)

mikey said:


> I'm not sure what is going on with your drill but if I had to guess, it is not sharpened well. The geometry may be off even if it is sharp. Are you using high quality drill bits?
> 
> I won't go into how to choose a reamer for a precision ID but I will tell you how I use one. I use a spotting drill, not a center drill. For my pre-reamer drill I choose the size carefully but it usually winds up pretty close to 0.003 - 0.005" under the reamer size. I spot the hole, drill with a drill that is one size smaller than the pre-reamer drill, then I use the pre-reamer drill. Then I use the reamer. The reason for this sequence is to debulk the hole with maximum accuracy and then skim cut it pretty straight with the pre-reamer drill; this then allows the reamer a decent chance of cutting evenly. Ideally, and especially on a critical work piece that must be concentric and true, I will pre-drill small, then bore the hole to the pre-reamer size before reaming. Drills make holes but they are not round and they are not straight. A reamer will follow that not straight hole and it will cut a bent hole that is on size. *Remember that if the reamed hole must be dead straight, you must bore it straight; you cannot drill it straight.*
> 
> Insofar as concentricity is concerned, as long as you do not remove the work piece from the 3 jaw you should be fine. Remove it and it will take a 4 jaw to get it realigned.


I guess it was the drill bit, I bought a 23/64 (.359”) drill bit and it cut just fine. I heard that your supposed to leave 1/64 for reaming, but i guess .016” is to much to ream. I don’t think I have a boring bar small enough to fit into bore. Is a spotting drill more accurate than a center drill? The muzzle breaks were held in a 3 jaw and turned and threaded in 1 setup.


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## mikey (Sep 14, 2019)

If you do it the right way, choosing a pre-reamer drill is almost as complicated as choosing a reamer to come in on a specific size because the material you are working with influences your choices. I'm attaching a doc that explains this statement.

I suspect most hobby guys buy a set of on-size reamers and expect to have holes of those sizes after reaming. The typical advice is to just pick a drill about 0.005" smaller than the reamer. This usually results in a hole that is off-size a few thou, depending on the pre-reamer drill, the reamer and the material. This is usually not a problem because we can make whatever fits in the hole to suit but if the hole *must* be a certain size then you have to go through a number of steps to choose the right drill and reamer and you have to know how to ream. This gets really expensive when you have to order a specific reamer for a critical hole.

Instead of buying specialty reamers, the best option for a hobby guy is to just bore the hole. Way cheaper and potentially more accurate because if you're really good at boring you can come in on size within the low tenths and you can often match or even beat the finish. I own multiple sets of reamers but I don't use them as often nowadays. It is so much faster and more accurate for me to just bore the stupid hole so I can get on with it. Nowadays, I mostly use a reamer in shallower through holes that I have to fit a pin into, and I can cut the pin to fit the hole I make. Otherwise, I bore it.

You are working with components that require good fits. If you plan to do a lot of this kind of work then it is going to be worth it to learn to bore a hole. This will mean spending money on good bars to fit the holes you require. It also requires that you spend the time to learn to bore accurately, which is not a bad skill to have if you ask me.

A spotting drill is not more accurate than a center drill but it does allow a drill to start more accurately so when you must optimize concentricity and accuracy, a spotter is preferred. I almost never use a center drill except on the end of a work piece to accept a live center. With that said, machinists have been using center drills for decades to start holes with and probably the majority feel this is the preferred tool. We had a good discussion on spotters here. I guess I should also emphasize that when using any drill, and especially when you're trying to maximize accuracy, start with a spotter and then peck and go slowly with your drill until the tips of the flutes are buried in the hole; then you can increase feed and pressure. Try it and you'll see that it is the most effective way to start a drill in a hole.

EDIT: almost forgot to add that you should make sure you put a 45 degree chamfer at the entrance to the hole before using a reamer. This will greatly reduce the chatter than can occur at the start.


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## gun410 (Sep 15, 2019)

mikey said:


> If you do it the right way, choosing a pre-reamer drill is almost as complicated as choosing a reamer to come in on a specific size because the material you are working with influences your choices. I'm attaching a doc that explains this statement.
> 
> I suspect most hobby guys buy a set of on-size reamers and expect to have holes of those sizes after reaming. The typical advice is to just pick a drill about 0.005" smaller than the reamer. This usually results in a hole that is off-size a few thou, depending on the pre-reamer drill, the reamer and the material. This is usually not a problem because we can make whatever fits in the hole to suit but if the hole *must* be a certain size then you have to go through a number of steps to choose the right drill and reamer and you have to know how to ream. This gets really expensive when you have to order a specific reamer for a critical hole.
> 
> ...


The best option diffidently sounds like boring vs buying a bunch of custom drill bits. I have bored before using a micro 100 bar but it broke and now all i have are Chinese carbide insert boring bars. I actually do have a small boring bar to fit the hole (4mm) but the when the insert is at a significant angle is that from it being a cheap chinese tool or is that how its supposed to be? Also with this small of a boring bar its too small to be able to use in my tool post holders, I guess i will have to make some sort of adapter. Also the micro 100 threading bar came in but I'll need to be able to bore before threading. When boring does it matter accuracy wise if you use the carriage feed vs turning the dial?

One of the youtubers i watch just came out with a review on these small carbide boring bars that seem to work good for pretty cheap. I'm thinking about picking some up, anyone else use these before? https://www.banggood.com/Drillpro-2...2931.html?rmmds=buy&ID=41227&cur_warehouse=CN




I appreciate the guide you've gave, will help a ton when drilling


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## mikey (Sep 15, 2019)

To save me time and typing, please review this thing.

The boring bar in pic#1 is a negative rake bar. The flat on top orients the bar. This is going to produce a nice finish but the cutting forces will be very high; personally, I avoid this type of bar.

You should invest in an Aloris AXA-4D and then make some adapters to hold smaller bars. See the article above for ideas. Alternatively, you can make something like this to fit your current holder and your smaller bars.


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## gun410 (Sep 16, 2019)

mikey said:


> To save me time and typing, please review this thing.
> 
> The boring bar in pic#1 is a negative rake bar. The flat on top orients the bar. This is going to produce a nice finish but the cutting forces will be very high; personally, I avoid this type of bar.
> 
> You should invest in an Aloris AXA-4D and then make some adapters to hold smaller bars. See the article above for ideas. Alternatively, you can make something like this to fit your current holder and your smaller bars.



Thank you for that link, I’ve looked for something like boring for beginners but have never found something that detailed. 

I don’t have an Aloris AXA-4d but my import QCTP came with a boring bar holder for 5/8 and 3/4. Are you suggesting the buying an new Aloris QCTP or just the boring bar holder because of its even clamping design, would it fit on my import QCTP? 

I actually do have a telescoping gauge set, I thought it was lost. I measured the 23/64 hole I previously drilled and it was .368” not sure why it came out oversized, but since that’s .007” away from my reamer size I decided to ream it.
The reamed hole came out .385”, .01 bigger than my reamer, not sure how that happened. That little extra room the reamer made won’t effect the suppressor’s performance but I would like to figure this problem out. I also should mention that my lathe isn’t leveled due to it being on a rolling tool cabinet.


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## mikey (Sep 16, 2019)

gun410 said:


> Thank you for that link, I’ve looked for something like boring for beginners but have never found something that detailed.
> 
> I don’t have an Aloris AXA-4d but my import QCTP came with a boring bar holder for 5/8 and 3/4. Are you suggesting the buying an new Aloris QCTP or just the boring bar holder because of its even clamping design, would it fit on my import QCTP?



You're welcome. Hope it helps you to bore better.

I am not suggesting that you buy an Aloris tool post! I do, however, suggest you buy an Aloris AXA 4D if you plan to do a lot of boring. And yes, it will fit your import AXA tool post. The boring bar holder you show in your pics is the typical import type that pushes against the bar at just two points with cotters; those cotters contact a steel sleeve inside the bore of the holder. This is not a secure way to hold a boring bar and will contribute to chatter in the bore. In contrast, the Aloris 4D squeezes down on the entire bar so that it cannot move once it is locked down. The only way to get it more solid is to use a heat shrink bar holder. As I said in the article, the holder is more important than the bar and it is worth buying or making a really good one.

The 4D also allows you to make sleeves to fit your smaller bars into it, making it possible to use every boring bar you have in one holder. Not sure that its practical to do that for your really small bars and it might be better to make a tool holder out of aluminum with a smaller bore in the holder to fit smaller bars. I suggest a 3/8" bore if you do this.



gun410 said:


> I actually do have a telescoping gauge set, I thought it was lost. I measured the 23/64 hole I previously drilled and it was .368” not sure why it came out oversized, but since that’s .007” away from my reamer size I decided to ream it.
> The reamed hole came out .385”, .01 bigger than my reamer, not sure how that happened. That little extra room the reamer made won’t effect the suppressor’s performance but I would like to figure this problem out. I also should mention that my lathe isn’t leveled due to it being on a rolling tool cabinet.



There are a number of reasons why a drill will drill oversize. The main one is because the geometry is off. If you take a drill gauge to your drills you will find that many drills are not ground dead on symmetrical, especially imported sets. *What brand of drills are you using and are they jobber drills?* Other reasons include drills that are not sharp, have improper relief angles, excessive web thickness (required more feed pressure to cut, which can exacerbate any asymmetry in the geometry) and then there is the human factor.

One of the key human factors is improper feed. I know drilling a hole may not seem like a big deal but for all cutting tools, performance is enhanced when the tool cuts continuously but without being forced into the cut. This is a feel thing. You must feed so there is a slight positive resistance to the feed so the tool cuts as efficiently as it can. This also allows the chip clearance features of the tool to work as they should. I have seen so many guys crank on the feed pressure as much as they can, thinking that is the right way to go. The drill comes out of the hole smoking hot and they wonder why their drills don't last long. My drills are almost cool to the touch after drilling but they cut fast and they stay sharp. The trick is to slow down the speed a little bit and feed properly. This allows the drill to cut accurately and your hole sizes will be closer to what they should be. 

I'm not surprised your reamer produced an oversized hole but as to why, I can only guess. I suspect that your pre-reamer hole was not straight and not consistently sized for the reasons discussed above. The reamer will try to follow that hole and if it cannot follow precisely then it will cut oversized as it cuts off the bends in the hole.

Another reason for reaming oversize is improper speeds and technique. You will find that for reamers above about 3/8", it is best to slow down. I run my reamers at about 100 rpm and again, feed so that there is a slight positive resistance to feed. I do not bottom out the reamer and I stop the machine when I finish the infeed before withdrawing the reamer; I do not retract the reamer with the machine running. I have reamers that are nearly 30 years old and are still sharp and accurate so this works for me.

The level of the lathe can have an impact on boring but it will be minimal. Most of your results are so oversized that I suspect the quality of your tools and the way you're using them is having more of an impact. The good thing is that this is easy to fix ... buy good tools and learn to use them well. Please know that I'm not criticizing you or dissing your stuff. I'm simply pointing out that you are trying to do precision work and that requires a realistic approach.

Okay, tired of typing.


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## benmychree (Sep 16, 2019)

It is not at all necessary to use inserts to thread, internal or external, nor is micrograin carbide necessary for most materials to be cut; for nearly all work, HSS is all that one needs, for external, Aloris makes a tool that only needs to be sharpened on top and has a very long service life, and Bokum makes internal threading bars that are form relieved and are also only sharpened on top, also long lived,  These tools are much more durable and forgiving in terms of not being easily broken/damaged as carbide tools are.


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## gun410 (Sep 17, 2019)

mikey said:


> You're welcome. Hope it helps you to bore better.
> 
> I am not suggesting that you buy an Aloris tool post! I do, however, suggest you buy an Aloris AXA 4D if you plan to do a lot of boring. And yes, it will fit your import AXA tool post. The boring bar holder you show in your pics is the typical import type that pushes against the bar at just two points with cotters; those cotters contact a steel sleeve inside the bore of the holder. This is not a secure way to hold a boring bar and will contribute to chatter in the bore. In contrast, the Aloris 4D squeezes down on the entire bar so that it cannot move once it is locked down. The only way to get it more solid is to use a heat shrink bar holder. As I said in the article, the holder is more important than the bar and it is worth buying or making a really good one.
> 
> ...



Ok, it definitely seems like an Aloris AXA-4d will be my best option and from there I can make multiple adapters. The slowest my lathe goes is 150 rpms which sucks. I did run my reamer out with the lathe on but I don’t believe that would’ve taken another .012” of material. 

I believe my reamer is a pretty good one, it’s solid carbide as well. The drill bit used isn’t a jobber drill, it’s coated ti or something and I bought it the other day just for this from menards. It cut pretty well, and when drilling I always like to keep an even light pressure on the tailstock, and keep the feed rate slower but still continuously cutting. 

If the leveling doesn’t effect it much would tailstock alignment? I purchased a mt4 to mt3 adapter for my spindle so I can put identical dead center in the tail stock and spindle. Then I can use a dial indicator to check alignment.

I was going over your boring thread again (as I have many times lol) and I need a boring bar before I can finish profiling the inside of the baffle cones. But anyway I saw you suggested the CSBI-250, I like the fact that it is solid carbide and won’t deflect as much. Also it seems like the best all in one bar for smaller and even some larger holes. I’ve been looking at them on eBay but how do u tell the rake angle and lead angle?


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## mikey (Sep 17, 2019)

Yes, tailstock alingment can cause issues with drilling accuracy on the lathe. If you are not dead sure the lathe is level and the tailstock is aligned then its time to do some work. If you don't know how, raise it on the forum.

I recommended the CCBI-250-5R. This is a carbide bar. The CSBI is steel and I don't recommend that. The CCBI series are positive lead bars; the 5R part means it has a 5 degree positive lead angle and the R means it is a right hand bar. This bar can go about 2.5" deep so you need at least 2-4" to go into the holder so look for a 4-6" long bar. 

The reason I asked what brand of drill you were using is because import drills are often not ground accurately. The jobber query was because jobber drills are quite long and flexible; a screw machine drill might be better - look up the differences.


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## Latinrascalrg1 (Sep 17, 2019)

If you dont already use it, sch-40 PVC pipe works great as a practice material to help work out the process.  Its cheap and plentiful and cuts nice enough for semi-fine detail work and did i mention its easily acquired!


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## gun410 (Sep 18, 2019)

mikey said:


> Yes, tailstock alingment can cause issues with drilling accuracy on the lathe. If you are not dead sure the lathe is level and the tailstock is aligned then its time to do some work. If you don't know how, raise it on the forum.
> 
> I recommended the CCBI-250-5R. This is a carbide bar. The CSBI is steel and I don't recommend that. The CCBI series are positive lead bars; the 5R part means it has a 5 degree positive lead angle and the R means it is a right hand bar. This bar can go about 2.5" deep so you need at least 2-4" to go into the holder so look for a 4-6" long bar.
> 
> The reason I asked what brand of drill you were using is because import drills are often not ground accurately. The jobber query was because jobber drills are quite long and flexible; a screw machine drill might be better - look up the differences.


Well, I do know my lathe isn't leveled but that's because my lathe is sitting on a tool cabinet with rollers. I was either going to make leveling feet or eventually get a lathe stand from grizzly. The tailstock is pretty well aligned but not dead nutz.

I was looking on ebay and I couldn't find a CCBI 1/4" over 4", but i did find some other carbide shaft bars. It would be nice to have one that uses CCMT inserts because i already have alot of them and you can get em cheaper than CDCD inserts. These were the best ones that were on ebay
1/4" CARBIDE BAR 6" OAL
5/16" Carbide bar, takes CCMT Oal 5-3/8
Kennametal 5/16" Carbide bar CDCD Oal 6"
CCBI-250 Oal 4"
Solid carbide bar 7mm

The grind on the drill bit i used seemed to be good but its only an import. Its a smaller bit and isn't flexible at all.


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## gun410 (Sep 18, 2019)

Latinrascalrg1 said:


> If you dont already use it, sch-40 PVC pipe works great as a practice material to help work out the process. Its cheap and plentiful and cuts nice enough for semi-fine detail work and did i mention its easily acquired!



No I’ve never tried pipe in my lathe, I wouldn’t think it would turn well. If it does it would be nice to practice id threading before the suppressor tube.


Sent from my iPhone using Tapatalk


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## Latinrascalrg1 (Sep 18, 2019)

gun410 said:


> No I’ve never tried pipe in my lathe, I wouldn’t think it would turn well. If it does it would be nice to practice id threading before the suppressor tube.
> 
> 
> Sent from my iPhone using Tapatalk


Then you will find it a nice substitute.  Sch 80 is thicker walled but not as cheap nor as easily found but works just as well, maybe even better.


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## ttabbal (Sep 18, 2019)

Sch80 is available as electrical conduit in the local big box stores here. I like it for learning as it's easy on tools.


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## gun410 (Sep 18, 2019)

ttabbal said:


> Sch80 is available as electrical conduit in the local big box stores here. I like it for learning as it's easy on tools.


I went to home depot today and picked up some sch 40 black pipe they didn't have any sch 80.


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## Latinrascalrg1 (Sep 18, 2019)

I was referring to the PVC sch 40 *PLASTIC* pipe.  I am sure you could get some practice with the black pipe but its not nearly as forgiving which to me is very helpful when in "Learning" mode.


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## mikey (Sep 18, 2019)

gun410 said:


> Well, I do know my lathe isn't leveled but that's because my lathe is sitting on a tool cabinet with rollers. I was either going to make leveling feet or eventually get a lathe stand from grizzly. The tailstock is pretty well aligned but not dead nutz.
> 
> I was looking on ebay and I couldn't find a CCBI 1/4" over 4", but i did find some other carbide shaft bars. It would be nice to have one that uses CCMT inserts because i already have alot of them and you can get em cheaper than CDCD inserts. These were the best ones that were on ebay
> 1/4" CARBIDE BAR 6" OAL
> ...



You should level your lathe, period. I would suggest doubling or tripling the thickness of your current top, laminating the wood so you have a solid base. It needs to be inset inside the lip on top of the chest if there is a raised lip. Get it solid, then level the lathe on top of that. Even if you move the base cabinet it shouldn't alter the lathe level too much. Get it level, get the tailstock aligned, or you will not be able to do precision work.

This bar that you linked to is the one I use but his may have grinding marks on it. I would ask him to send you pics of the two he has on sale so you can decide if you want it. He started out with 9 of these exact bars, seems like he has sold 7 of them. The advantage to this bar is that it uses either 0.007" or 0.002" nose radius flat top inserts with positive axial rake. Of course, you have to wait until they show up on ebay or pay retail but this is an awesome geometry. The other thing to do is to be patient and wait; another will show up eventually. The hard thing is that since I published that boring article, you are now competing with all the other guys!

As for the other bars, read the article I wrote and think about the geometry a bit and then make your choice. I certainly cannot choose for you. You might also start a thread and ask the guys. I know the SCLCR boring bars are popular because there are a ton of cheap bars sold in sets. The guys will be able to tell you how well they work.

If your drill bit is small, it is flexible, especially a jobber drill. A screw machine drill of the same diameter will be shorter and, consequently, stiffer.


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## gun410 (Sep 18, 2019)

Latinrascalrg1 said:


> I was referring to the PVC sch 40 *PLASTIC* pipe.  I am sure you could get some practice with the black pipe but its not nearly as forgiving which to me is very helpful when in "Learning" mode.


I see, i guess my local home depot does have it. 


mikey said:


> You should level your lathe, period. I would suggest doubling or tripling the thickness of your current top, laminating the wood so you have a solid base. It needs to be inset inside the lip on top of the chest if there is a raised lip. Get it solid, then level the lathe on top of that. Even if you move the base cabinet it shouldn't alter the lathe level too much. Get it level, get the tailstock aligned, or you will not be able to do precision work.
> 
> This bar that you linked to is the one I use but his may have grinding marks on it. I would ask him to send you pics of the two he has on sale so you can decide if you want it. He started out with 9 of these exact bars, seems like he has sold 7 of them. The advantage to this bar is that it uses either 0.007" or 0.002" nose radius flat top inserts with positive axial rake. Of course, you have to wait until they show up on ebay or pay retail but this is an awesome geometry. The other thing to do is to be patient and wait; another will show up eventually. The hard thing is that since I published that boring article, you are now competing with all the other guys!
> 
> ...


Well if I'm going to level my lathe I'm tempted to weld up a steel bench for it but i'm open to changing the tool cabinet but i would have to take the rollers off. right now i have 2 1/4" steel plates sitting under the lathe and the wood top. I could buy a sheet of 3/4" plywood and screw down 2 layers of that to the wood top.

I offered $50 on that bar and he countered at $55 but I haven't accepted yet because i would rather have a longer bar than 4". I would rather get a carbide boring bar that takes ccmt inserts, i can only find CDCD 51 with a .015 nose radius.

I also have to buy a tool that will work for turning the outside of the baffles (60 deg). The picture is from Ecco Machine, but my parting tools sucks in this lathe, it wont even cut straight with a locked caraige. I'm not sure what tool what be best for this any suggestions?


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## mikey (Sep 18, 2019)

Okay, you have two 1/4" thick steel plates with one layer of 3/4" ply on top of that to which the lathe is mounted? If so, then that is enough. I would not change the cabinet. I would just level the lathe on top of that stack and it should be solid enough. Even if the cabinet moves a bit, it won't be able to warp two layers of plate steel bolted to a plywood top. I suggest you find a way to use leveling devices that attach to the steel through the wood, though. One of our guys did a nice job on his; I'll try to find his thread.

Your call on the boring bar. The problem I have with CCMT/CCGT inserts is that the smallest nose radius I am aware of is the 21.50 insert, which has a 0.008" nose radius. This is okay for general work but you cannot get down to 0.002-0.004" so you have to really know how to work with that larger nose radius. You can do it; I just personally prefer a smaller nose radius. The CM CCBI can use a 0.002" NR but you have to either wait for it to come up on ebay or buy it retail and they are not that cheap. Still worth it in my experience but its your money so you have to decide. 

As for the parting tool, I can tell you that inserted carbide works but cutting forces are higher. I much prefer HSS. In my experience, loose gibs or crappy tolerances in the carriage/compound assembly is responsible for most parting issues. You might consider making a solid plinth for your lathe; that will resolve most parting issues for you.


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## mikey (Sep 18, 2019)

Here is the thread by @TerryH that I was referring to.


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## gun410 (Sep 19, 2019)

mikey said:


> Okay, you have two 1/4" thick steel plates with one layer of 3/4" ply on top of that to which the lathe is mounted? If so, then that is enough. I would not change the cabinet. I would just level the lathe on top of that stack and it should be solid enough. Even if the cabinet moves a bit, it won't be able to warp two layers of plate steel bolted to a plywood top. I suggest you find a way to use leveling devices that attach to the steel through the wood, though. One of our guys did a nice job on his; I'll try to find his thread.
> 
> Your call on the boring bar. The problem I have with CCMT/CCGT inserts is that the smallest nose radius I am aware of is the 21.50 insert, which has a 0.008" nose radius. This is okay for general work but you cannot get down to 0.002-0.004" so you have to really know how to work with that larger nose radius. You can do it; I just personally prefer a smaller nose radius. The CM CCBI can use a 0.002" NR but you have to either wait for it to come up on ebay or buy it retail and they are not that cheap. Still worth it in my experience but its your money so you have to decide.
> 
> As for the parting tool, I can tell you that inserted carbide works but cutting forces are higher. I much prefer HSS. In my experience, loose gibs or crappy tolerances in the carriage/compound assembly is responsible for most parting issues. You might consider making a solid plinth for your lathe; that will resolve most parting issues for you.


I have 1 10"x10"x1/4" plate under each leg of the lathe, The wood top isn't super thick so I'm considering screwing 2 more layers of 3/4" plywood on top. Terry's way was cool, but i would rather swap the rollers for leveling feet so i know the lathe can't move around and it stays level.

I would prefer a boring bar with CDCD insert so i have the ability to use a .002" NR. The only thing preventing me from buying that 4" boring bar is the length of it, I would prefer a 6" oal bar, and the availability of the inserts. When i order a boring bar I want to be able to use it right away, but i'm a little confused on inserts. I went through ebay and found the only CDCD inserts, but I got quite confused with all the different variety and I don't know how to tell the insert's NR. There is CDCD-500, CDCD-15, CDCD-51 will they all work in that boring bar?
CDCD-500 .002 NR CDCD-15-CM2 CDCD-02-CM2  CDCD-15-CS2
If i can't find the right inserts for the CCBI-250 bar i'll probably buy a micro 100 bar so I can start turning as soon as i get it.

I have tried hss parting before and it worked ok on aluminum but i wouldn't cut 17-4 so i switched to carbide but when you advance the carbide parting tool and pressure on the part increases the tool shifts to the left (returns straight after cutting) not producing an even cut. The right side of the cut doesn't end up being square and the cut shifts to the left the deeper you go. It could be the gibs since i haven't done much with them, but i doubt it. So that why I asked for a suggestion for an alternative tool to profile the outside of the baffles.


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## mikey (Sep 19, 2019)

Correct me if I'm wrong, please. Are you under the impression that leveling the tool cabinet is somehow related to the leveling of the independently mounted lathe on top?

As for the CCBI boring bar, a 6" bar is nice but a 4" bar is adequate. Consider that the max extension of a 1/4" bar is only 2.5", which leaves you with 1.5" in the holder. You need 3-4 times the OD to hold a bar securely so at a minimum you need 1" to hold that bar. In addition, the vast majority of the time you will not be boring at max extension. Your call but my 1/4" and 3/16" CCBI bars are both 4" long and work fine.

The CDCD500 insert has a 0.002" NR. A CDCD505 insert has a 0.007" NR. A CDCD15 insert has a 0.015" NR; no bueno.

With regard to the parting tool, consider that a carbide insert is damned stiff. It takes a fair amount of pressure to bend an insert and typically a carbide insert will break before it bends much. Is it possible/likely that the structure of the lathe is moving? And why are you having to exert so much feed pressure? Are you absolutely positive your tool is on center? If you are, how are you setting that height - by eye? When a parting tool requires a great deal of feed pressure, it is almost always the case that it is set too high; the tool is contacting the work below the cutting edge. If tool height is correct, is it possible that there is enough slack in your carriage/compound to allow upward travel? This needs to be sorted.

We are getting way off topic (threading and thread mics) and it appears that your questions are not being viewed because they are buried in this thread. Might be better to start another thread regarding your choices for boring bars and perhaps another on lathe leveling and another on parting tools. The reason for suggesting this is so you have the entire forum weighing in on answering your questions. I'm sure there are many other guys who own a lathe like yours that would be able to give you better answers. Something to think about, maybe?


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## gun410 (Sep 20, 2019)

mikey said:


> Correct me if I'm wrong, please. Are you under the impression that leveling the tool cabinet is somehow related to the leveling of the independently mounted lathe on top?
> 
> As for the CCBI boring bar, a 6" bar is nice but a 4" bar is adequate. Consider that the max extension of a 1/4" bar is only 2.5", which leaves you with 1.5" in the holder. You need 3-4 times the OD to hold a bar securely so at a minimum you need 1" to hold that bar. In addition, the vast majority of the time you will not be boring at max extension. Your call but my 1/4" and 3/16" CCBI bars are both 4" long and work fine.
> 
> ...



Well my plan is to level the lathe by adjusting leveling feet (4-6) underneath the tool cabinet.

I ordered the 4” holder and the cdcd-500 .002 NR. I probably make a holder for it and get an Aloris axa-4d.

Yea it’s not the carbide bending something with the carriage, could it be the gibs?

I will make another thread but I will be doing some threading that I will post here. And I also received my dro so I can tell how deep I’m threading.
	

	
	
		
		

		
		
	


	





Sent from my iPhone using Tapatalk


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## mikey (Sep 21, 2019)

gun410 said:


> Well my plan is to level the lathe by adjusting leveling feet (4-6) underneath the tool cabinet.
> 
> I ordered the 4” holder and the cdcd-500 .002 NR. I probably make a holder for it and get an Aloris axa-4d.
> 
> ...



Let me clarify something that might help. If the lathe is mounted to a cabinet that directly supports the ends of the lathe, like a factory stand, then leveling feet on the cabinet can twist the bed and allow you to use those feet to level the lathe. If, on the other hand, the lathe is mounted to a substrate that is itself mounted on a cabinet then leveling the feet will not significantly alter the substrate the lathe is bolted to. It might have a little effect but not much because the lathe is effectively isolated from the cabinet by the substrate. Typically you level the lathe on the substrate and double check it if you have to re-site the lathe but it usually remains stable. 

I think the CCBI -250-4-5R is one of the finest small boring bars made, and the CDCD500 is an excellent flat topped insert that is capable of boring in the tenths. Provided the bar is in good shape, it should serve you well. He mentioned grind marks on the bar and I hope they do not affect function.

Provided your parting tool is truly on center, I am not sure why you are having so much trouble parting. Start a thread so the other G0602 can help.


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## WarrenP (Sep 21, 2019)

I have the GO752, same as the 602 except has adjustable speed. I had problems parting also until I got one of the "T" shaped parting tools. after that it works very well. You might try one of those and make sure the tool holder , etc is very ridgid.


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## gun410 (Sep 24, 2019)

mikey said:


> Let me clarify something that might help. If the lathe is mounted to a cabinet that directly supports the ends of the lathe, like a factory stand, then leveling feet on the cabinet can twist the bed and allow you to use those feet to level the lathe. If, on the other hand, the lathe is mounted to a substrate that is itself mounted on a cabinet then leveling the feet will not significantly alter the substrate the lathe is bolted to. It might have a little effect but not much because the lathe is effectively isolated from the cabinet by the substrate. Typically you level the lathe on the substrate and double check it if you have to re-site the lathe but it usually remains stable.
> 
> I think the CCBI -250-4-5R is one of the finest small boring bars made, and the CDCD500 is an excellent flat topped insert that is capable of boring in the tenths. Provided the bar is in good shape, it should serve you well. He mentioned grind marks on the bar and I hope they do not affect function.
> 
> Provided your parting tool is truly on center, I am not sure why you are having so much trouble parting. Start a thread so the other G0602 can help.



I haven’t got around to starting a g0602 thread for parting, but the next time I part I will take a good video of the tool shifting and start the thread.

I like the idea of mounting the lathe on the substrate, but either way I don’t have a machinist level. They are pretty expensive $150+ so it might be couples week till I get it. I hope the lathe isn’t being effected by a bad level.

The boring bar worked pretty well, I was running 300 rpms and hand feeding it by feel until I hit the desired depth on the dro. It took a while machining .01 DOC to get the .385” hole to 1.24” diameter. but it was pleasant cutting with the ccbi bar. 

The order I’m making these baffles is: boreing hole, profiling inside of cone, profiling outside of cone and parting off. The next step is to bore the inside of the cone with a boring bar or the 1” 60° countersink 1 flute. I will probably use the countersink for ease but I don’t know how to measure how deep to cut with the countersink.

This baffle is going to one of the 2 first blast baffles ( .006” thick vs normal baffle .004” thick). And the overall height of my bb’s is 1.25” and my metal stock only has 1.2” sticking out, can I losses the 3 jaw and pull it out a little or would that screw up concentricity too much?


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## mikey (Sep 24, 2019)

gun410 said:


> The boring bar worked pretty well, I was running 300 rpms and hand feeding it by feel until I hit the desired depth on the dro. It took a while machining .01 DOC to get the .385” hole to 1.24” diameter. but it was pleasant cutting with the ccbi bar.



Okay, cutting speed for 17-4 stainless is roughly 175-300 sfm, so you need to speed up the lathe. *RPM = Cutting speed in SFM X 3.82 / D*, where D = diameter of the work piece. So, say your work piece is 1.5" OD. The calculated speed would be somewhere near 764 rpm; this would be a good starting point for external turning. The problem is that we are not external turning; we're boring. Your boring bar is not seeing that 1.5" OD; it is seeing the size of the bore. So, say you started with that 0.385" hole. This would give us 300 X 3.82 / 0.385" = 2976 rpm. Note that as the bore size increases, rpm drops (EDIT: rpm is supposed to drop) until you reach your 1.24" ID, where lathe speed would be somewhere near 1000 rpm. Not only that but your feed is supposed to change with rpm as well. It gets complicated, and this is the stuff I left out of the boring article  because it confuses folks.

So, how do you bore a stupid hole? The way I do it is to start with the starting ID and calculate rpm; in this case our starting rpm would be near 3000. Since my lathe cannot go that fast, I would start at the max speed my lathe can run, which is 2400 rpm. I would manually feed the bar because the hole is shallow, blind and because I can feed at whatever feed rate I need to keep up with the speed to produce coiled chips. As the hole gets larger, I cut my speed down *IF* I have trouble producing the chips I want. Sometimes in harder materials it can be difficult to keep up with the speed and this will cause poor finishes and inaccuracies in the bore. If this is the case, slow the lathe down a gearing step or two and that will allow you to keep up with your feed.

As I keep saying, the lathe teaches us to respond to the cut and this is one example of that. If you cannot feed fast enough to produce the chips you need, slow down the speed until you can.

One thing you must do when boring to precise depths is to use a carriage stop. Do not rely on a DRO; it is not precise enough. Use a stop. If you do not have a stop, buy or make one but get one and use it. I'm not trying to seem draconic here; not only will a stop improve the accuracy and appearance of your bore; it will prevent you from damaging your bar.



gun410 said:


> The order I’m making these baffles is: boreing hole, profiling inside of cone, profiling outside of cone and parting off. The next step is to bore the inside of the cone with a boring bar or the 1” 60° countersink 1 flute. I will probably use the countersink for ease but I don’t know how to measure how deep to cut with the countersink.



Not sure how the gun guys do this. Maybe post this in that subforum?[/QUOTE]



gun410 said:


> This baffle is going to one of the 2 first blast baffles ( .006” thick vs normal baffle .004” thick). And the overall height of my bb’s is 1.25” and my metal stock only has 1.2” sticking out, can I losses the 3 jaw and pull it out a little or would that screw up concentricity too much?



Anytime you loosen the jaws of a 3 jaw chuck you lose your origin. However, if you part off a piece and are pulling out stock to make another piece from a longer piece of material then you'll be fine. The next part will be concentric with the spindle centerline.[/QUOTE]


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## mikey (Sep 24, 2019)

Forgot to respond about the level. I think the minimum accuracy for use on machine tools is about 0.0005"/foot. There are a lot of import levels that fit this criteria and they are pretty cheap. Here is one that might work, for $88.00. There are many levels that are better than this but not for the money.


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## gun410 (Sep 24, 2019)

mikey said:


> Okay, cutting speed for 17-4 stainless is roughly 175-300 sfm, so you need to speed up the lathe. *RPM = Cutting speed in SFM X 3.82 / D*, where D = diameter of the work piece. So, say your work piece is 1.5" OD. The calculated speed would be somewhere near 764 rpm; this would be a good starting point for external turning. The problem is that we are not external turning; we're boring. Your boring bar is not seeing that 1.5" OD; it is seeing the size of the bore. So, say you started with that 0.385" hole. This would give us 300 X 3.82 / 0.385" = 2976 rpm. Note that as the bore size increases, rpm drops (EDIT: rpm is supposed to drop) until you reach your 1.24" ID, where lathe speed would be somewhere near 1000 rpm. Not only that but your feed is supposed to change with rpm as well. It gets complicated, and this is the stuff I left out of the boring article  because it confuses folks.
> 
> So, how do you bore a stupid hole? The way I do it is to start with the starting ID and calculate rpm; in this case our starting rpm would be near 3000. Since my lathe cannot go that fast, I would start at the max speed my lathe can run, which is 2400 rpm. I would manually feed the bar because the hole is shallow, blind and because I can feed at whatever feed rate I need to keep up with the speed to produce coiled chips. As the hole gets larger, I cut my speed down *IF* I have trouble producing the chips I want. Sometimes in harder materials it can be difficult to keep up with the speed and this will cause poor finishes and inaccuracies in the bore. If this is the case, slow the lathe down a gearing step or two and that will allow you to keep up with your feed.
> 
> ...




That clears up surface speed for me thanks, but how about finding desired DOC based off NR? I currently don'y have a carriage stop, I thought my dro would do the same purpose. I would like to purchase a carriage stop for my lathe if i can find one, but what happens if the carriage's half nut is engaged and feeds into the stop?

This baffle is ready to be finished but I'm concerned about not having enough metal sticking out of the chuck. The height of the baffle is 1.25" and after measuring off the chuck jaws i have 1.285" sickout leaving me only .035" extra room for the parting tool and my  2mm parting tool is .07" wide, that's a problem... And I don't want to pull out the metal because even moving it a little will change the origin.

I could profile the inside of the cone, turn down outside of material to be concentric with the inside of cone, cut metal to 1.5" long, flip the jaws around in the chuck, grip inside of baffle and then i could profile the outside of cone, and machine OD of baffle to have a nice slip fit.
Usually baffles are made in 1 setup to ensure concentrically, the steps bellow are the common practice for machining baffles and which i was originally planning on. But the method i explains above is very similar to Practical Renaissance's method in the video bellow.

1-Drill the bore
2-Use a boring bar to profile the inside of the cone
3-Profile the outside of the cone
4-Part off cone


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## mikey (Sep 24, 2019)

Depth of cut when boring depends on a number of factors - material being cut, desired finish, horsepower and rigidity of the lathe and the cross slide/compound, etc. My lathe, with my CCBI bar, can easily take 0.020" deep cuts in 304 SS but I am not sure what your lathe can do. You will have to test it to see how big a roughing cut your lathe can handle with that bar in whatever material you're working with. While inserts can take big cuts, that is not what they are designed to do. They work best with a depth of cut that is just a bit larger than the NR. If you need to go deep, get a CDCD 505 insert with a 0.007" NR.

Ask Grizzly for a carriage stop. If one is not available, make one. For precision boring, it is almost a must have. A DRO will work for occasional bores but for a gunsmith doing precision boring, no, too slow. When you bore, you have to stay focused because you are moving really fast when using inserted carbide bars. If you are using power feed then you will mark your bar so you know when you're approaching your final depth, then you will kick the lathe out of power feed and feed manually into your carriage stop. If your lathe has a clutch on the feed rod then no problem if you run into the stop under power; if it does not have a clutch then something will break, like your feed gears. I don't recommend power feed for shallow blind bores unless you are experienced at boring under power and can stop in time. Most of the time it is just as fast to manually feed, especially in shallow bores.

For your baffles, please bring it to the gunsmithing subforum so the guys there can give you a hand.


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