# Threading away from the chuck on my lathe...



## schemer

I never tried it yet but see the potential and want to try threading a 60 degree thread on my lathe but use the carriage moving away from the chuck. My question is, if I have the compound set at 29.5 degrees when I thread the regular way, do I leave it set the same for the "away from" the chuck method? Or do I need to switch the compound to 30.5 degrees?
Thanks!


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## Cactus Farmer

You will have left handed threads! Good luck!


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## schemer

Cactus Farmer said:


> You will have left handed threads! Good luck!



No I won't. You have to put the cutting tool in upside down and run the chuck in reverse.


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## kd4gij

You would feed in with the cross slide so the compound won't matter. Or swing the compound with the dial on the head stock side. And run spindle in reverse.


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## Superburban

I have seen people do it on Youtube, and they make it look easy. I don't recall any ever mentioning how they set the compound. 

I don't think it matters for either way of threading, The theory is you take the heavy cut on one side of the thread, and the half degree is to keep the other side of the thread cut clean. Grab a scrap piece, and give it a shot both ways.


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## Wreck™Wreck

Ignore the compound, there is no good reason to worry about the approach angle.

On the rare occasion that I am called upon to modify a stock right hand threaded fastener I turn the spindle in reverse and cut on the backside, a boring bar works well for this. One must remember that all X axis moves are negative however.

Works a charm.


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## schemer

Wreck™Wreck said:


> Ignore the compound, there is no good reason to worry about the approach angle.
> 
> On the rare occasion that I am called upon to modify a stock right hand threaded fastener I turn the spindle in reverse and cut on the backside, a boring bar works well for this. One must remember that all X axis moves are negative however.
> 
> Works a charm.



Now that is an interesting way to do it. I may need to get a boring bar threading tool from Mesa Tool and try that.
Thanks for the info.


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## schemer

kd4gij said:


> You would feed in with the cross slide so the compound won't matter. Or swing the compound with the dial on the head stock side. And run spindle in reverse.



Yeah, I have always used the compound method but it seems I should try the cross slide as it sure does seem like it would be easier. I have a Grizzly G4003G so I think is will be stout enough to do what I need even if I have to take smaller cuts to do it. I just wanted to try higher speeds for better finish and use a carbide instead of HSS.


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## schemer

Superburban said:


> I have seen people do it on Youtube, and they make it look easy. I don't recall any ever mentioning how they set the compound.
> 
> I don't think it matters for either way of threading, The theory is you take the heavy cut on one side of the thread, and the half degree is to keep the other side of the thread cut clean. Grab a scrap piece, and give it a shot both ways.



Youtube always makes things look easy. I know you have to be focused when trying this reverse method as the brain is wired for always doing it the other way. I will definitely do some testing. My 2 1/4 - 8 TPI threads were a little rough so when I start on my 3rd attempt I wanted it to be "the charm".


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## Charles Spencer

What?  Nobody mentioned Joe Pie yet?


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## schemer

Charles Spencer said:


> What?  Nobody mentioned Joe Pie yet?



I fast forwarded through his video last night but realized he was cutting an ACME or square thread so I wanted to be sure I knew if the 60 degree single point would be the same or not.


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## Bob Korves

I have used a right side up tool on the back side of the work, spindle turning the opposite direction, feeding away from the chuck.  Same as WreckWreck  showed.  Even also used a boring bar.  It works fine, no fear of a crash during the cut.  It does the same thread that we usually do, but in a reverse path.


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## schemer

Bob Korves said:


> I have used a right side up tool on the back side of the work, spindle turning the opposite direction, feeding away from the chuck.  Same as WreckWreck  showed.  Even also used a boring bar.  It works fine, no fear of a crash during the cut.  It does the same thread that we usually do, but in a reverse path.



Bob,
  Do you feed with the cross feed only too? I need to buy a few more threading tools. In this case I need to cut an 8 TPI thread so I was just doing a quick crash course on finding a tool and proper inserts. Do the IR16 AG60 inserts sound like a good choice? Or go with the IR16 G60?


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## Bob Korves

I typically only feed with the compound.  As long as the thread is not too coarse, it works fine.  The cutting tool is ideally ground a bit differently for a compound cut than for a cross slide cut.  The only thread I have done from the back side was 32 TPI.  It turned out nice.  Here is a link to the work:
http://www.hobby-machinist.com/thre...th-starrett-196a-back-plunge-accessory.48595/


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## whitmore

schemer said:


> No I won't. You have to put the cutting tool in upside down and run the chuck in reverse.


Or (it'd work on some lathes) reverse the headstock so it's on your right, not your left.   Tool force still
bears down onto the bed, that way.


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## darkzero

Threading away from the chuck using the compound you'd want the compound at the 7:00 position rather than the 5:00 position (I'm not mentioning degrees as the markings vary on lathes but you get the idea). Doesn't matter if you are cutting a LH thread or spindle in reverse with the cutter upside down to cut a RH thread.

As for AG60 or G60, as you know both will cover 8 TPI. Choice really matters on how close to a shoulder you are threading to or how wide the thread relief is. G60 has a wider tip so it's more stout, in theory stronger, better for heavier DOC. If your thread relief is narrow or you are threading closer to a shoulder the AG60 would be the btter choice. Another factor is how usefull the insert will be. AG60 covers a wider range of threads. You have a 12x lathe, it's not likely you'll be taking heavy cuts. IMO the AG60 would be the better choice as it would be more useful for other thread pitches.

Which leads to another thing. I mentioned threading close to a shoulder or to a thread relief. If your threading away from the chuck, obviously you're not threading to a shoulder or into a thread relief so this doesn't matter right? And one of the advantages of threading away from the chuck is you can thread at a faster speed.

Yes but if your thread starts close to a should or your thread relief is narrow, this is where you are starting, you'll have a much smaller margin for error when engaging the half nuts. At 8 TPI the thread dial is already spinner faster than a finer thread. Then add the thought of wanting to thread at a high RPM. If your thread is starting close to a shoulder or in a small thread relief, better engage the half nuts with precision. Make a mistake & chances are you'll destroy your threads.

I thread close to a shoulder or into a very narrow thread relief often cause the stuff I make is small. Sometimes I don't make a thread relief at all. When threading conventionally (into the chuck) you don't have to worry about making a mistake when engaging the half nut. This is why I prefer to thread conventionally & not away from the chuck. It's much easier for me to disegage the half nuts at a mark than trying to catch the thread dial spot on when starting close to a shoulder or in a narrow thread relief if the thread dial is spinning at 10K rpm.

But if you're not starting close to a shoulder or in a narrow thread relief, then ya got nothing to worry about. 

My post is already long but I wanted to add anyway since the subject of cutter upside down came up. As said I always single point external threads with the compound feeding towards the chuck, that's how I was taught & is what I'm used to. But when I single point internal threads, I mount my cutter upside down the the spindle in reverse but it's not threading away from the chuck nor is it a LH thread. I'm still using a RH cutter & I'm threading on the backside of the internal bore. Allows me to actually see what I'm threading easier & I don't have to reposition my compound, it stays the same as for external threads.


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## RJSakowski

Cactus Farmer said:


> You will have left handed threads! Good luck!





schemer said:


> No I won't. You have to put the cutting tool in upside down and run the chuck in reverse.


Forward or reverse, tool in front or tool in back, right side up or upside down, you will not cut a left hand thread.  

In order to cut a left hand thread, you have to have a reversing gear which reverses the rotation of the lead screw in your gear train.  The reversing gear is an idler gear that reverses the direction of rotation of the lead screw relative to the spindle.  Each gear set (one or more gears locked together on the same shaft) rotates in the opposite direction to the gears it meshes with. If you have a RH  lead screw like my Atlas/Craftsman, the lead screw will turn in the same direction as the spindle to cut RH threads and in the opposite direction to cut LH threads.  My Grizzly 602 has a LH lead screw so it turns opposite to the spindle for RH threads and in the same direction for LH threads.

Lathes that are set up for this usually have a tumbler or banjo that moves the reversing gear in and out of the gear train.  The 602 doesn't come with one so I made my own.  

Cutting threads with the tool facing up and and in the front is essentially the same as turning the tool upside down and cutting from the rear.  If you think about it, you simply rotating the entire cutting mechanism 180º around the spindle axis. If you are cutting toward the tailstock by reversing the spindle rotation, the tool must be flipped so it is upside down at the front or right side up at the rear but you will still cut a RH thread.

As to whether the compound angle should remain at 29.5º.  The reason for setting the compound at 29.5º is that setting the compound at  an angle  and advancing the cutting depth with it will cut primarily on one side of the thread v.  This reduces the likelihood of chatter from cutting both side at once.  The effect is similar to what is experienced with a parting tool or a form tool.  The 29.5º angle is designed to primarily cut one face of the thread but take a very light skim cut on the second face.  

I expect that you will be OK leaving the compound angle set as for inboard threading.  You are still cutting primarily one side of the thread.  I would personally rotate the compound to 29.5º in the outboard direction if it didn't create an interference issue.  You wouldn't want to set the angle to 30.5º though.  A 30.5º angle can result in a step on the near face.

Concerning forgetting about the compound and advancing with the cross slide, here are my thoughts.  Using this method is fine for a rigid and tight lathe.  Problems can arise when threading with a smaller lathe or one which is not at tight as it should be.  These are the same issues we experience with parting.  Some people can part with no difficulty while others just can't seem to get the right technique.  My personal experience with threading is that once I started using the compound , set at 29.5º, my thread quality improved significantly.  

Additionally, by separating out the tool back out from the compound tool feed, I don't have to remember what my dial is set to.  On completion of a pass, I disengage the half nuts, back the cross feed out one full turn, move the carriage to the start of the next pass, return the cross feed to zero, advance the compound feed, and engage the half nuts.  The cross feed is always at zero for a pass and I know how much I have advanced my feed from the compound dial.

The only problem that I see with outboard threading is the amount of backlash in the lead screw gear train.  If the lathe is tight, it shouldn't be an issue.  My tired old Atlas has quite a bit of lash so I like to start a pass four or five threads before engaging the work.  For outboard threading, this may be an excessive amount of thread relief.The Grizzly has considerably less backlash so I should be OK with it.

Note: As I finish this, I see that a number of other posters have put forth similar thoughts.  I am posting this anyway because it bears repeating.


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## Bob Korves

The easier and safer but slower way to cut a thread from a shoulder is to cut to the right, leave the half nuts engaged for the entire job, and back the tool up under power to near the shoulder with the tool away from the work, and then move the tool up against the shoulder by rotating the chuck by hand.  Dial in the feed for the cut and run the cutter toward the tailstock.  Repeat as required.


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## schemer

darkzero said:


> Threading away from the chuck using the compound you'd want the compound at the 7:00 position rather than the 5:00 position (I'm not mentioning degrees as the markings vary on lathes but you get the idea). Doesn't matter if you are cutting a LH thread or spindle in reverse with the cutter upside down to cut a RH thread.
> 
> As for AG60 or G60, as you know both will cover 8 TPI. Choice really matters on how close to a shoulder you are threading to or how wide the thread relief is. G60 has a wider tip so it's more stout, in theory stronger, better for heavier DOC. If your thread relief is narrow or you are threading closer to a shoulder the AG60 would be the btter choice. Another factor is how usefull the insert will be. AG60 covers a wider range of threads. You have a 12x lathe, it's not likely you'll be taking heavy cuts. IMO the AG60 would be the better choice as it would be more useful for other thread pitches.
> 
> Which leads to another thing. I mentioned threading close to a shoulder or to a thread relief. If your threading away from the chuck, obviously you're not threading to a shoulder or into a thread relief so this doesn't matter right? And one of the advantages of threading away from the chuck is you can thread at a faster speed.
> 
> Yes but if your thread starts close to a should or your thread relief is narrow, this is where you are starting, you'll have a much smaller margin for error when engaging the half nuts. At 8 TPI the thread dial is already spinner faster than a finer thread. Then add the thought of wanting to thread at a high RPM. If your thread is starting close to a shoulder or in a small thread relief, better engage the half nuts with precision. Make a mistake & chances are you'll destroy your threads.
> 
> I thread close to a shoulder or into a very narrow thread relief often cause the stuff I make is small. Sometimes I don't make a thread relief at all. When threading conventionally (into the chuck) you don't have to worry about making a mistake when engaging the half nut. This is why I prefer to thread conventionally & not away from the chuck. It's much easier for me to disegage the half nuts at a mark than trying to catch the thread dial spot on when starting close to a shoulder or in a narrow thread relief if the thread dial is spinning at 10K rpm.
> 
> But if you're not starting close to a shoulder or in a narrow thread relief, then ya got nothing to worry about.
> 
> My post is already long but I wanted to add anyway since the subject of cutter upside down came up. As said I always single point external threads with the compound feeding towards the chuck, that's how I was taught & is what I'm used to. But when I single point internal threads, I mount my cutter upside down the the spindle in reverse but it's not threading away from the chuck nor is it a LH thread. I'm still using a RH cutter & I'm threading on the backside of the internal bore. Allows me to actually see what I'm threading easier & I don't have to reposition my compound, it stays the same as for external threads.



Thanks for the explanation and thoughts on the carbide choices. The main reason I am trying to figure this out and test other methods is because I don't cut many threads in the first place although I would love to be really good at it, and because I am making an adapter for an important personal project. This requires a 2 1/4 - 8 tpi thread and that would be the largest thing I have ever threaded. I would think it would be easier but after 2 tries, the thread was looking pretty rough and not symmetrical. Of course it looked "ok" and it actually threaded into one of the 2 plates (back plate and face plate), but not the other. So I figured something was wrong with the threads on the ebay purchased faceplate although they looked great to me. I ordered a tap to clean up the threads and rechecked all my setting on the lathe to figure out why the threading looks so bad. I checked my compound angle which I have set at 60.5 which also checks out fine with a protractor and is actually 29.5 degrees. I counted the teeth on my thread dial as I read that Grizzly had been shipping the G4003 with the wrong gear (15t instead of the correct 16t) and that was fine. I checked for slop in the more than likely "like new" half nuts as they don't see a lot of action and that was fine. I was running at 70 RPM and the gearing and settings are all good too. So last night I went back out there to the shop and had a closer look at my threading tool and it looks like hell. So that is likely my main problem. The tool like mine is shown below. What is the best way to sharpen that style of tool? Just flat onto the face of the grinder and assume all other angles are built-in and correct? I will get and post a pic of my handy work on the adapter and post it here later.


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## schemer

RJSakowski said:


> Forward or reverse, tool in front or tool in back, right side up or upside down, you will not cut a left hand thread.
> 
> In order to cut a left hand thread, you have to have a reversing gear which reverses the rotation of the lead screw in your gear train.  The reversing gear is an idler gear that reverses the direction of rotation of the lead screw relative to the spindle.  Each gear set (one or more gears locked together on the same shaft) rotates in the opposite direction to the gears it meshes with. If you have a RH  lead screw like my Atlas/Craftsman, the lead screw will turn in the same direction as the spindle to cut RH threads and in the opposite direction to cut LH threads.  My Grizzly 602 has a LH lead screw so it turns opposite to the spindle for RH threads and in the same direction for LH threads.
> 
> Lathes that are set up for this usually have a tumbler or banjo that moves the reversing gear in and out of the gear train.  The 602 doesn't come with one so I made my own.
> 
> Cutting threads with the tool facing up and and in the front is essentially the same as turning the tool upside down and cutting from the rear.  If you think about it, you simply rotating the entire cutting mechanism 180º around the spindle axis. If you are cutting toward the tailstock by reversing the spindle rotation, the tool must be flipped so it is upside down at the front or right side up at the rear but you will still cut a RH thread.
> 
> As to whether the compound angle should remain at 29.5º.  The reason for setting the compound at 29.5º is that setting the compound at  an angle  and advancing the cutting depth with it will cut primarily on one side of the thread v.  This reduces the likelihood of chatter from cutting both side at once.  The effect is similar to what is experienced with a parting tool or a form tool.  The 29.5º angle is designed to primarily cut one face of the thread but take a very light skim cut on the second face.
> 
> I expect that you will be OK leaving the compound angle set as for inboard threading.  You are still cutting primarily one side of the thread.  I would personally rotate the compound to 29.5º in the outboard direction if it didn't create an interference issue.  You wouldn't want to set the angle to 30.5º though.  A 30.5º angle can result in a step on the near face.
> 
> Concerning forgetting about the compound and advancing with the cross slide, here are my thoughts.  Using this method is fine for a rigid and tight lathe.  Problems can arise when threading with a smaller lathe or one which is not at tight as it should be.  These are the same issues we experience with parting.  Some people can part with no difficulty while others just can't seem to get the right technique.  My personal experience with threading is that once I started using the compound , set at 29.5º, my thread quality improved significantly.
> 
> Additionally, by separating out the tool back out from the compound tool feed, I don't have to remember what my dial is set to.  On completion of a pass, I disengage the half nuts, back the cross feed out one full turn, move the carriage to the start of the next pass, return the cross feed to zero, advance the compound feed, and engage the half nuts.  The cross feed is always at zero for a pass and I know how much I have advanced my feed from the compound dial.
> 
> The only problem that I see with outboard threading is the amount of backlash in the lead screw gear train.  If the lathe is tight, it shouldn't be an issue.  My tired old Atlas has quite a bit of lash so I like to start a pass four or five threads before engaging the work.  For outboard threading, this may be an excessive amount of thread relief.The Grizzly has considerably less backlash so I should be OK with it.
> 
> Note: As I finish this, I see that a number of other posters have put forth similar thoughts.  I am posting this anyway because it bears repeating.



RJ, Thanks for the detailed explanation. I also learned the compound way of doing it and it seems natural. It also has less backlash but that doesn't matter if you compensate for the backlash on the cross feed. I also have a DRO so I can really be sure and accurate. Still, I manage to cut ugly threads.  My G4403G seems to be a pretty tight machine other than the usual backlash. I Have never crashed my lathe yet and don't plan to so I was going with the regular way of threading and using a purchased 60 degree threading tool as pictured above. In the end I should just grind my own threading tool. But I will spend the money on a few threading tools that use the inserts just so I have them in my toolbox. I think my dull tool is causing most of my frustration but I didn't realize it was dull until after the fact. I likely too too big of a cut or maybe my tool got above center but I checked all of that when I set it up. I did find later though where the tool was above center when I tried to figure out the problem. I also have a BXA tool post that has the piston as opposed to the wedge design and I noticed when I tightened the tool holder in the TP, it cocks up on the front a little. That may have been what I noticed when the cut seemed to be deeper than I turned the compound at one time and made a thicker chip. Anyhow, I will learn as much as I can with all the good help here and be better for it and have more new tools too.


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## schemer

Bob Korves said:


> The easier and safer but slower way to cut a thread from a shoulder is to cut to the right, leave the half nuts engaged for the entire job, and back the tool up under power to near the shoulder with the tool away from the work, and then move the tool up against the shoulder by rotating the chuck by hand.  Dial in the feed for the cut and run the cutter toward the tailstock.  Repeat as required.



Bob, I checked out your thread in that link and those are some tiny threads but they turned out great. I have read about leaving the half nuts engaged for metric threads but this would be another good use as you have pointed out. On metric threads though, why can't the numbers be used anyhow?? And here are the pics of my rough looking threads as I mention a post or two above:


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## RJSakowski

Imperial lead screws are nice even tpi threads; 8, 12, 16.   My grizzly 602 has 12 tpi and 48 teeth on the threading indicator gear with 12 marks on the indicator.  Rotation of 1/4 turn means the position of the carriage relative to the lead screw has moved by exactly 1 inch.  The thread indicator has move exactly 3 marks.  All imperial threads have an integral number of threads in an inch so the pattern repeats every inch and moving 1 inch puts the cutting tool in the same relationship to the thread being cut as it was before moving.  For odd half integral tpi, the pattern repeats every 2 inches so I have to move the carriage by 6 marks or a half dial rotation. For thread pitches divisible by 3 (6, 9,12, etc.) the pattern repeats every 1/3 inch and I can engage on any mark.

My Atlas has a 16 tpi lead screw and 32 teeth on the the thread indicator gear.  One complete revolution of the thread dial moves the carriage exactly 2".  There are four marks on the the dial so moving 2 marks moves the carriage exactly 1 inch.  To cut even tpi, I can engage on any mark since the pattern repeats every half inch.  To cut odd tpi, I have to engage on every other mark, either even or odd.  To cut an odd half integral thread, I have to engage on the same mark for each pass.  8 tpi lead screw machines function in much the same manner as the Atlas.

Unfortunately, metric threads are not integral multiples of 1 inch.  For a 1mm pitch, the pattern doesn't repeat for 100m or 3,937 inches.  for .7mm, you would have to move 700m or 27,559".  You have to engage in exactly the same position  on the lead screw to ensure the cutting tool maintains its relationship to the thread.  This is why we are advised to not disengage the half nuts.  

Tom Lipton, OxTools has a good video on a method of cutting metric threads with a lathe with an Imperial lead screw where he does disengage the half nuts but then re-engages them in the same position.  The advantage is that you don't have to rely on the lathe coasting to a stop when threading to a shoulder.  There have been several references to this video on this forum and a quick search will pull it up.


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## mksj

There is a lot of technique to cutting a decent thread, and type, pitch and depth are all factors.  The material/diameter/cutter used also plays a significant part of the equation. So there is a bit of trial and error to figure out what works. I have my lathe setup with an electronic stop, so the half-nut is not disengaged until you have completed the threading process, which makes metric threading much easier. An electronic stop also allows you to thread up to a shoulder, as the repeatability exceeds 0.001".  Without this, there are some merits to threading away from the headstock as shown, but it takes some experience to hit the threading dial at the correct position when cutting something like a 8 TPI at 60 RPM. I usually thread steel at 120-150 RPM, and softer materials at 250 RPM. So each pass occurs in 1-2 seconds.

The thread cutter/insert also plays a big part in cutting the thread and the final finish. Specific to threading inserts/cutters there is a specific TPI cutting range that is specified. I recently had to cut a M50-1.5 thread in 8620 steel, and had a few bobbles in getting it cut right.  I had not turned this steel before nor threaded it, and found that it did not take well to positive rake tooling. Also you need to be very methodical in the depth of cut on each pass, and look at the curls/finish on each pass. In this case, I got a little too aggressive on the depth of cut and the positive rake threading insert blew apart, the thread also got a bit mangled. I switched to a neutral rake threading insert and took smaller cuts and was able to come out with a decent final product. On smaller threads, I will often cut about 95% of the thread on the lathe and finish the final sizing with an adjustable die or tap, this gives a very precise and polished finish cut.

In your case, you need a sharp cutting tool, good cutting fluid, and to take progressively lighter cuts per pass the deeper the thread. Another common mistake, is that some threading dials may not be perfectly aligned with the indicator line. So one may think they are engaging it at the same mark, but in reality they are either just ahead or behind the indicator and do not perceive the difference. This can easily happen with the lower  TPI threads because of the dial speed.

M50-1.5 thread in 8620



In this case both internal and external 1" threads were cut, but required different threading inserts because the thread depth was >0.07". These where cut at around 250 RPM.


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## Doubleeboy

heard about turning upside down and left to right years ago but never tried it till I saw Joe P's Youtube video.  I am a believer, not only is drama free it is also a very easy way to pick up a thread to do repair work.


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## schemer

RJSakowski said:


> Imperial lead screws are nice even tpi threads; 8, 12, 16.   My grizzly 602 has 12 tpi and 48 teeth on the threading indicator gear with 12 marks on the indicator.  Rotation of 1/4 turn means the position of the carriage relative to the lead screw has moved by exactly 1 inch.  The thread indicator has move exactly 3 marks.  All imperial threads have an integral number of threads in an inch so the pattern repeats every inch and moving 1 inch puts the cutting tool in the same relationship to the thread being cut as it was before moving.  For odd half integral tpi, the pattern repeats every 2 inches so I have to move the carriage by 6 marks or a half dial rotation. For thread pitches divisible by 3 (6, 9,12, etc.) the pattern repeats every 1/3 inch and I can engage on any mark.
> 
> My Atlas has a 16 tpi lead screw and 32 teeth on the the thread indicator gear.  One complete revolution of the thread dial moves the carriage exactly 2".  There are four marks on the the dial so moving 2 marks moves the carriage exactly 1 inch.  To cut even tpi, I can engage on any mark since the pattern repeats every half inch.  To cut odd tpi, I have to engage on every other mark, either even or odd.  To cut an odd half integral thread, I have to engage on the same mark for each pass.  8 tpi lead screw machines function in much the same manner as the Atlas.
> 
> Unfortunately, metric threads are not integral multiples of 1 inch.  For a 1mm pitch, the pattern doesn't repeat for 100m or 3,937 inches.  for .7mm, you would have to move 700m or 27,559".  You have to engage in exactly the same position  on the lead screw to ensure the cutting tool maintains its relationship to the thread.  This is why we are advised to not disengage the half nuts.
> 
> Tom Lipton, OxTools has a good video on a method of cutting metric threads with a lathe with an Imperial lead screw where he does disengage the half nuts but then re-engages them in the same position.  The advantage is that you don't have to rely on the lathe coasting to a stop when threading to a shoulder.  There have been several references to this video on this forum and a quick search will pull it up.



Thanks RJ for the detailed explanation on the half nuts and metric threading. I will check out Tom Liptons video. I have watch some of his stuff in the past.


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## schemer

mksj said:


> There is a lot of technique to cutting a decent thread, and type, pitch and depth are all factors.  The material/diameter/cutter used also plays a significant part of the equation. So there is a bit of trial and error to figure out what works. I have my lathe setup with an electronic stop, so the half-nut is not disengaged until you have completed the threading process, which makes metric threading much easier. An electronic stop also allows you to thread up to a shoulder, as the repeatability exceeds 0.001".  Without this, there are some merits to threading away from the headstock as shown, but it takes some experience to hit the threading dial at the correct position when cutting something like a 8 TPI at 60 RPM. I usually thread steel at 120-150 RPM, and softer materials at 250 RPM. So each pass occurs in 1-2 seconds.
> 
> The thread cutter/insert also plays a big part in cutting the thread and the final finish. Specific to threading inserts/cutters there is a specific TPI cutting range that is specified. I recently had to cut a M50-1.5 thread in 8620 steel, and had a few bobbles in getting it cut right.  I had not turned this steel before nor threaded it, and found that it did not take well to positive rake tooling. Also you need to be very methodical in the depth of cut on each pass, and look at the curls/finish on each pass. In this case, I got a little too aggressive on the depth of cut and the positive rake threading insert blew apart, the thread also got a bit mangled. I switched to a neutral rake threading insert and took smaller cuts and was able to come out with a decent final product. On smaller threads, I will often cut about 95% of the thread on the lathe and finish the final sizing with an adjustable die or tap, this gives a very precise and polished finish cut.
> 
> In your case, you need a sharp cutting tool, good cutting fluid, and to take progressively lighter cuts per pass the deeper the thread. Another common mistake, is that some threading dials may not be perfectly aligned with the indicator line. So one may think they are engaging it at the same mark, but in reality they are either just ahead or behind the indicator and do not perceive the difference. This can easily happen with the lower  TPI threads because of the dial speed.
> 
> M50-1.5 thread in 8620
> View attachment 243561
> 
> 
> In this case both internal and external 1" threads were cut, but required different threading inserts because the thread depth was >0.07". These where cut at around 250 RPM.
> View attachment 243563



MKSJ,
  Looking good. I thought about the threading dial and maybe me missing the mark one time but although the line doesn't line perfectly up with the mark, it has to move quite a bit before it locks in the next tooth. I am pretty sure I can adjust it by loosening the gear on the dial and lining it up when the half nuts are engaged and re-tightening it, or I could just make a new temporary mark. That electronic stop is nice but I do not have one. I hope it is reliable or...ouch. I am threading unknown DOM tubing drops from ebay for my part. I believe it can likely only be one of a handful of steel types like A513 in 1020-1026. So it should be able to be threaded ok. I was using that dark sulphur cutting fluid and have others to try too. I don't think I am going to buy a 2 1/4-8 die for my most likely one of project as in reality, the threads don't have to be perfect (although I want them to be). It is just to adapt a chuck and face plate to a welding positioner. But I believe I messed up my threading tool with too deep a cut although I don't think I moved the compound more than .005 but maybe that is too much once you are in the groove deeper than the start. The best teacher is experience but not with large diameter steel chunks for the scrap barrel. I am going to test on some 1214L but it is only 1 inch diameter. I am sure it will cut like butter and I will smile, but I want that same smile on the DOM @ 2 1/4-8.  Thanks for all the feedback.


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## RJSakowski

The OEM thread dial on my G0602 was not concentric with the shaft.  It was far enough out that it would be uncertain as to which tooth of the gear to engage.  I made a new dial for my lathe and everything line up perfac5tly now.  The sordid details are here:http://hobby-machinist.com/threads/threading-on-a-grizzly-g0602.34230/


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## mksj

The electronic stop in reality does not fail, it uses an electronic proximity sensor similar to what is used on CNC machines for homing and stops. If they fail the machine would brake to a stop, it is also backed up by a mechanical  limit switch which engages within 0.05" after the P sensor triggers. The hard stop is at 0.07".

The depth of cut you are taking is quite large, relative to my experience. I take a scribe pass, and at most will take a 0.002" cut, then 0.001", then back down to 0.0005" as I get closer to target and then a spring pass in particular on a smaller less rigid lathe. Depends on the material, thread and diameter.  With coolant and a bigger machine you can get away with deeper cuts. Some steels like 1018, at least for me seems to tear and chatter when cutting threads. Smaller thread cutters/inserts are easily damaged from too deep of cut, especially as you get deeper into the thread. If you need to do deeper threads on larger stock (over 1" diameter), you might consider a beefier threading tool, you will still run into problems with deep threads. The maximum depth for my threading inserts is ~0.07" and you are looking at twice this. Example below is the Carmex lay down inserts which I use for internal threads, and I am pushing them at 0.07" thread depth. I think most people would grind their own HSS thread cutter in this application.


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## woodchucker

schemer said:


> Yeah, I have always used the compound method but it seems I should try the cross slide as it sure does seem like it would be easier. I have a Grizzly G4003G so I think is will be stout enough to do what I need even if I have to take smaller cuts to do it. I just wanted to try higher speeds for better finish and use a carbide instead of HSS.


I prefer the compound method. And I have cut a couple of times with the tool upside down and running in reverse out toward the tailstock. Met a guy a few years ago who told me about it, that it was the way to go when you needed to get close and would crash if you didn't stop in time.. I told him I wouldn't be needing that, I don't think I'll have that problem... (NEVER SAY NEVER)... And when I had to do it, I clearly remembered his sage advice.  He obviously walked away shaking his head saying stupid guy you'll need it one day.


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## schemer

RJSakowski said:


> The OEM thread dial on my G0602 was not concentric with the shaft.  It was far enough out that it would be uncertain as to which tooth of the gear to engage.  I made a new dial for my lathe and everything line up perfac5tly now.  The sordid details are here:http://hobby-machinist.com/threads/threading-on-a-grizzly-g0602.34230/



You did a nice job on that. I think my problem is user error. I think my lathe is ok except the threading dial out of line by a smidge.


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## benmychree

schemer said:


> Thanks for the explanation and thoughts on the carbide choices. The main reason I am trying to figure this out and test other methods is because I don't cut many threads in the first place although I would love to be really good at it, and because I am making an adapter for an important personal project. This requires a 2 1/4 - 8 tpi thread and that would be the largest thing I have ever threaded. I would think it would be easier but after 2 tries, the thread was looking pretty rough and not symmetrical. Of course it looked "ok" and it actually threaded into one of the 2 plates (back plate and face plate), but not the other. So I figured something was wrong with the threads on the ebay purchased faceplate although they looked great to me. I ordered a tap to clean up the threads and rechecked all my setting on the lathe to figure out why the threading looks so bad. I checked my compound angle which I have set at 60.5 which also checks out fine with a protractor and is actually 29.5 degrees. I counted the teeth on my thread dial as I read that Grizzly had been shipping the G4003 with the wrong gear (15t instead of the correct 16t) and that was fine. I checked for slop in the more than likely "like new" half nuts as they don't see a lot of action and that was fine. I was running at 70 RPM and the gearing and settings are all good too. So last night I went back out there to the shop and had a closer look at my threading tool and it looks like hell. So that is likely my main problem. The tool like mine is shown below. What is the best way to sharpen that style of tool? Just flat onto the face of the grinder and assume all other angles are built-in and correct? I will get and post a pic of my handy work on the adapter and post it here later.
> View attachment 243555


I use that Aloris tool in all my threading (external); they are sharpened ONLY on top at an angle that is parallel to the centerline of the lathe; most come in a sharp vee style, and I usually stone a flat on the front face of the vee, and they hold up better; I keep one sharp for fine threads and others with varying width of flats to more or less match the national thread specs for truncation.  The tool should be inclined in the holder to more or less match the spiral angle of the thread being cut, then ground flat on the top in line with the centerline of the lathe.  Also, I always set the compound at 30 degrees, and have no problem with cleaning up the backside of the thread; this is as I was taught in school and in my apprenticeship also, and I am unaware of any journeymen in my apprenticeship shop that did otherwise.


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## schemer

mksj said:


> The electronic stop in reality does not fail, it uses an electronic proximity sensor similar to what is used on CNC machines for homing and stops. If they fail the machine would brake to a stop, it is also backed up by a mechanical  limit switch which engages within 0.05" after the P sensor triggers. The hard stop is at 0.07".
> 
> The depth of cut you are taking is quite large, relative to my experience. I take a scribe pass, and at most will take a 0.002" cut, then 0.001", then back down to 0.0005" as I get closer to target and then a spring pass in particular on a smaller less rigid lathe. Depends on the material, thread and diameter.  With coolant and a bigger machine you can get away with deeper cuts. Some steels like 1018, at least for me seems to tear and chatter when cutting threads. Smaller thread cutters/inserts are easily damaged from too deep of cut, especially as you get deeper into the thread. If you need to do deeper threads on larger stock (over 1" diameter), you might consider a beefier threading tool, you will still run into problems with deep threads. The maximum depth for my threading inserts is ~0.07" and you are looking at twice this. Example below is the Carmex lay down inserts which I use for internal threads, and I am pushing them at 0.07" thread depth. I think most people would grind their own HSS thread cutter in this application.
> 
> 
> View attachment 243567



I guess double redundancy on the safety is a great thing. Does your lathe have a clutch or can it coast after the motor is turned off?
I think you are correct on me taking too large a cut. I found this chart on a forum (maybe this one, not sure)-see below, and I didn't follow it exactly but used it as a guide as I thought it may/may not apply to my situation. My hss cutter is capable of 6 tpi and above so I am thinking I am good there but I am glad you brought this up as I didn't buy any threading tool holders or inserts yet and will have to study the specs real close before I do.


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## schemer

benmychree said:


> I use that Aloris tool in all my threading (external); they are sharpened ONLY on top at an angle that is parallel to the centerline of the lathe; most come in a sharp vee style, and I usually stone a flat on the front face of the vee, and they hold up better; I keep one sharp for fine threads and others with varying width of flats to more or less match the national thread specs for truncation.  The tool should be inclined in the holder to more or less match the spiral angle of the thread being cut, then ground flat on the top in line with the centerline of the lathe.  Also, I always set the compound at 30 degrees, and have no problem with cleaning up the backside of the thread; this is as I was taught in school and in my apprenticeship also, and I am unaware of any journeymen in my apprenticeship shop that did otherwise.



Thanks benmychree for the sharpening advice. I read on the Aloris site to "just grind the top" and they didn't mention a flat on the tip. I knew about the flat on the tip for other hss threading tools but I figure it is better to ask than to mess it up and then ask. I have many grinders and I assume the best wheel is still the white aluminum oxide for this?


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## woodchucker

schemer said:


> You did a nice job on that. I think my problem is user error. I think my lathe is ok except the threading dial out of line by a smidge.


Mine too, it doesn't matter, it's a reference mark


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## mksj

All good points, in particular on the HSS cutter sharpening/profile. I agree with the depth of cut probably being too much, and the tables you mentioned are often based on larger cutters in more rigid lathes. I would think that HSS cutter would do well/better in this application, I use carbide thread cutting inserts because they work decently in most of my applications and if they break (which happened when cutting the M50 1.5 thread), I pop a new one in and maintain the same cutter position. They also make HSS inserts, that I may try but they are more expensive then carbide ones.  There are also issues of rigidity/deflection with smaller stock and sometimes the stock may twist slightly if the cutter gets caught or chatters. I would think this would not be a issue with the larger stock/thread you are cutting, just need more smaller passes.



schemer said:


> I guess double redundancy on the safety is a great thing. Does your lathe have a clutch or can it coast after the motor is turned off?


The lathe stop system uses electronic braking, with 1 second stopping time. In reality it stops the cutter at the same exact position on every pass, the proximity sensor is triggered by the carriage position, with the P sensor attached to the micrometer stop. So one can adjust it with a high degree of resolution. No worries.  There are some variations as to threading with the cross slide vs. threading with the compound slide (there have been some recent posting on this). Internal/blind threads I only use the cross slide to maintain the same ending cutter position, I do not cut a relief, just a end grove with the my threading insert. The cutter will always finish in the grove. External threads, it varies. Usually just the cross slide, but there are some cases where using the compound slide produces better chip formation and finish. Since the P sensor is triggered by the carriage, changing the compound changes the cutter finish position and requires a wider landing relief. When threading with the cross slide, I just cut a relief groove and can thread to the shoulder (usually within 0.001"). The other significant advantage with this system is that the half-nut stays engaged through the whole process. Nice because my reflexes and eyesight suck as I get (am) older. I have also seen mechanical stop systems that disengage the half-nut, but this wouldn't help me when I do metric threads.

Cutting internal blind thread and finished thread (sorry did not clean the chips out)




Threading with a proximity stop and electronic braking.


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## schemer

mksj said:


> All good points, in particular on the HSS cutter sharpening/profile. I agree with the depth of cut probably being too much, and the tables you mentioned are often based on larger cutters in more rigid lathes. I would think that HSS cutter would do well/better in this application, I use carbide thread cutting inserts because they work decently in most of my applications and if they break (which happened when cutting the M50 1.5 thread), I pop a new one in and maintain the same cutter position. They also make HSS inserts, that I may try but they are more expensive then carbide ones.  There are also issues of rigidity/deflection with smaller stock and sometimes the stock may twist slightly if the cutter gets caught or chatters. I would think this would not be a issue with the larger stock/thread you are cutting, just need more smaller passes.
> 
> 
> The lathe stop system uses electronic braking, with 1 second stopping time. In reality it stops the cutter at the same exact position on every pass, the proximity sensor is triggered by the carriage position, with the P sensor attached to the micrometer stop. So one can adjust it with a high degree of resolution. No worries.  There are some variations as to threading with the cross slide vs. threading with the compound slide (there have been some recent posting on this). Internal/blind threads I only use the cross slide to maintain the same ending cutter position, I do not cut a relief, just a end grove with the my threading insert. The cutter will always finish in the grove. External threads, it varies. Usually just the cross slide, but there are some cases where using the compound slide produces better chip formation and finish. Since the P sensor is triggered by the carriage, changing the compound changes the cutter finish position and requires a wider landing relief. When threading with the cross slide, I just cut a relief groove and can thread to the shoulder (usually within 0.001"). The other significant advantage with this system is that the half-nut stays engaged through the whole process. Nice because my reflexes and eyesight suck as I get (am) older. I have also seen mechanical stop systems that disengage the half-nut, but this wouldn't help me when I do metric threads.
> 
> Cutting internal blind thread and finished thread (sorry did not clean the chips out)
> View attachment 243581
> View attachment 243582
> 
> 
> Threading with a proximity stop and electronic braking.



Wow. Nice setup! What brand DRO is that? I had to go look up that lathe and realize it is actually affordable. Then add all the cool options and a little less affordable.  I have one on my wish list for when I win the lottery though. So when you added all the proximity stop and VFD drive etc, how much more money did that add to the lathe? Just curious. I am just a hobby lathe user so I guess I will have to just tweak my Grizzly and learn more tricks for now. You have a nice lathe and a very clean one too. I have to agree 100% that my eyesight is sucking too and I hate it. I also need new lights out in the shop. I think I will post another thread for some ideas on that.

So that chart I posted should be disregarded and I will cut my next set of those threads I need to finish using your recommendations and see if that does the trick. First I need to sharpen my existing tool or I may just try to grind my first 60 degree tool. You make many great points and I have learned a lot from your feedback. Thank you.

Edit: So are you are using a phase converter for the VFD?


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## Wreck™Wreck

Next week I have to turn 6 parts, 3 1/2"-4 internal threads in a blind hole 4 1/2" deep using a manual lathe, this should be entertaining at best.


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## Bamban

Here is another threading video using a proximity  sensor. The VFD system and Prox are both MKSJ's creation. This is my Jet 1024. 

Lately I've been threading with the cross slide after I set the compound to bore the same taper as the 223 Remington and I did not want to reset the compound back and forth.


Watch "Ken's Shilen # 2 Threading with Proximity Sensor" on YouTube






Repeatability 

Watch "Testing Proximity Sensor Stopping Repeatability" on YouTube


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## Silverbullet

Be a good way to try out using die head cutter blade. To cut threads.


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## schemer

Bamban said:


> Here is another threading video using a proximity  sensor. The VFD system and Prox are both MKSJ's creation. This is my Jet 1024.
> 
> Lately I've been threading with the cross slide after I set the compound to bore the same taper as the 223 Remington and I did not want to reset the compound back and forth.
> 
> 
> Watch "Ken's Shilen # 2 Threading with Proximity Sensor" on YouTube
> 
> 
> 
> 
> 
> 
> Repeatability
> 
> Watch "Testing Proximity Sensor Stopping Repeatability" on YouTube



Nice! You guys are making me jealous.


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## pstemari

What brand/model of proximity switch are you using?

I've thought about trying the backwards threading technique, but I use laydown inserts and would need to get a left-handed toolholder and seat shims to reverse the helix angle. Full-profile laydown inserts are a joy to use.

Sent from my Pixel XL using Tapatalk


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## TORQUIN

schemer said:


> I never tried it yet but see the potential and want to try threading a 60 degree thread on my lathe but use the carriage moving away from the chuck. My question is, if I have the compound set at 29.5 degrees when I thread the regular way, do I leave it set the same for the "away from" the chuck method? Or do I need to switch the compound to 30.5 degrees?
> Thanks!



The 29.5 degrees, either way, just makes the tool cut one side or the other, if the compound is used. When I went to inverted threading, with HSS, I left the compound in the regular position, 5 o'clock, and it works quite well. I have been very happy with my threads this way, left and right-handed. That might be why it hasn't been mentioned in the videos you've seen, because it is irrelevant and the author didn't think to says anything.

Chris


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