# First Try at Metric Threading



## erikmannie (Feb 21, 2021)

I have done a bit of Imperial threading, but I will be doing a lot of metric threading now (for fun!).

I started out with 1” steel hex, wanting to do M16-2.0. I overshot the diameter because I was confused about how to read an analog metric micrometer. So on to M14-2.0, then.

I left the half nut engaged throughout the whole operation. This is also the first time that I have had my DRO on mm.

I won’t be able to get a nut to test it for about 6 hours.

Here are some pictures in case anybody has any constructive criticism, particularly with regard to the compound being set at the correct angle. I see some chatter.


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## erikmannie (Feb 21, 2021)

When I left the half nut engaged the whole time, I disengaged the power lever upon arriving at my safety groove. I then backed out on the cross slide, and then used the power lever to rotate the chuck in reverse which moved the carriage back out to get ready for another pass.


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## benmychree (Feb 21, 2021)

I think I see a built up chip edge on the tool, that will effect finish quality, what cutting fluid are you using?  The way the chips are turning black, I'm thinking perhaps too much speed, which would also tent to cause chip welding on the cutting edge.  A little undersize on the major diameter is generally not a problem; the OD of a thread is usually filed off to eliminate burrs, so the OD usually ends up under the nominal size anyway.
A 3 jaw chuck is much better than a 4 jaw for holding hex stock accurately centered with much less fiddling around.


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## Aukai (Feb 21, 2021)

Learned a bunch, thanks for posting....


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## erikmannie (Feb 21, 2021)

benmychree said:


> I think I see a built up chip edge on the tool, that will effect finish quality, what cutting fluid are you using?  The way the chips are turning black, I'm thinking perhaps too much speed, which would also tent to cause chip welding on the cutting edge.  A little undersize on the major diameter is generally not a problem; the OD of a thread is usually filed off to eliminate burrs, so the OD usually ends up under the nominal size anyway.
> A 3 jaw chuck is much better than a 4 jaw for holding hex stock accurately centered with much less fiddling around.



My CF is 70% Mobilmet 766 (Neat Cutting Fluid, an oil) and 30% Mobil DTE 24 (light hydraulic oil).

The RPM was about 70 to 100 RPM.

I never mind fiddling with a 4J chuck, but I will put the 8” 3J on there because I will be doing this for the next 7 days.

Thank you for the help. I did not notice the build up on the HSS threading blade, but I see it now.


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## erikmannie (Feb 21, 2021)

Question: why don’t people with inch pitch leadscrews leave the half nut engaged throughout the whole operation for Imperial threading as well, as we do with metric threading? It is no trouble at all, and there is no worry about missing the mark on the thread dial. It would coast the same distance if I used the E-stop button.

Second question: I’m curious to see what is going to happen when I try a much smaller safety groove and stop the threading pass with my foot brake. When I disengage my power lever to stop power, it coasts for about 8 mm as the chuck is spinning down.


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## Ischgl99 (Feb 21, 2021)

Looks good!  Most of what I do is metric.  I don’t mind keeping the half nuts engaged and reversing, it doesn’t seem any slower than using the threading dials once you get some practice.  

What kind of threading tool is that?  I already bought an Arthur Warner on edge holder, but that looks interesting.


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## Ischgl99 (Feb 21, 2021)

Are you running a VFD on your lathe?  If so, check your deceleration time and shorten it stop quicker.


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## mikey (Feb 21, 2021)

Erik, you're developing some tearing on the trailing edges of the threads. This might have to do with how the Aloris blade is ground; you may be at the limits of the helix angle that tool will allow. You might also check to see if the blade is level/horizontal; the bolts have some play so check to see if it is level.

The other thing is that your thread relief is a bit too shallow. When the tool runs off into that thread relief there should be no contact of the tool with the work. Typically, the depth of the thread relief is 0.003-0.005" deeper than the minor diameter of the thread. This will not affect the strength of the work piece.


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## benmychree (Feb 21, 2021)

For threading, I use TapMagic, it will give you a better finish, and yes, the tool should be adjusted  in the holder to approximate the helix angle of the thread being cut and ground parallel with the axis of the lathe on top; this does not mean that you need to adjust for every different pitch that you cut, one grind will work on nearly every thread that you cut.  I have used those Aloris threading tools since back in the 1970s and really like them, they also come in common acme thread pitches.  Note that the Aloris tools and tool holders are made so that they can be inverted in the holder and used to thread with the work rotating backwards and feeding from left to right for RH threads.


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## erikmannie (Feb 21, 2021)

Ischgl99 said:


> Looks good!  Most of what I do is metric.  I don’t mind keeping the half nuts engaged and reversing, it doesn’t seem any slower than using the threading dials once you get some practice.
> 
> What kind of threading tool is that?  I already bought an Arthur Warner on edge holder, but that looks interesting.



Here is the link to the threading tool:





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						Aloris CXA-8
					





					www.ajaxtoolsupply.com
				




and blade:





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						High Speed Threading Blade, 60º, P-6
					






					www.aloris.com


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## erikmannie (Feb 21, 2021)

Ischgl99 said:


> Are you running a VFD on your lathe?  If so, check your deceleration time and shorten it stop quicker.



No VFD. I have an RPC. Wiring is not one of my strengths.


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## erikmannie (Feb 21, 2021)

mikey said:


> Erik, you're developing some tearing on the trailing edges of the threads. This might have to do with how the Aloris blade is ground; you may be at the limits of the helix angle that tool will allow. You might also check to see if the blade is level/horizontal; the bolts have some play so check to see if it is level.
> 
> The other thing is that your thread relief is a bit too shallow. When the tool runs off into that thread relief there should be no contact of the tool with the work. Typically, the depth of the thread relief is 0.003-0.005" deeper than the minor diameter of the thread. This will not affect the strength of the work piece.



The (single, see photo) bolt was tight, and it is horizontal.

I’m glad you told me that about the thread relief (safety groove). I have been making it the minor diameter.

I have next week off, and I will be doing nothing but making metric nuts and bolts; I will get to see how all my HSS & carbide 60° tools work, being mindful of the previously unconsidered helix angle that you mentioned. 

I went to the hardware store and bought M4 through M18 nuts and bolts in both fine and coarse, where applicable. I am allowing myself 7 days to make one nut & one bolt of everything.


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## 7milesup (Feb 21, 2021)

mikey said:


> Erik, you're developing some tearing on the trailing edges of the threads. This might have to do with how the Aloris blade is ground; *you may be at the limits of the helix angle that tool will allow. *


I have done no threading on my lathe.  Yet.  
I am trying to understand the helix angle comment.  Is the angle (pitch) of the thread so great that the trailing portion of the thread is in interference with the trailing part of the cutter.  Just trying to wrap my head around this.  
As a side note, Martin Cleeve's book "Screwcutting in the Lathe" just arrived at my door two days ago.  Have only had a chance to look at the first few pages so far.


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## BGHansen (Feb 21, 2021)

erikmannie said:


> Question: why don’t people with inch pitch leadscrews leave the half nut engaged throughout the whole operation for Imperial threading as well, as we do with metric threading? It is no trouble at all, and there is no worry about missing the mark on the thread dial. It would coast the same distance if I used the E-stop button


That's generally how I thread. It goes faster for me since I don't have to wait for the thread dial number to come around. If I'm using the thread dial, I back the carriage up to my number, engage the half nuts, set the cross feed and compound, then fire up the lathe.

On the other hand, I am using the half nuts to back up the carriage so potentially some added wear to the nuts. But it isn't under load and I'm not a production shop.

Bruce


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## SLK001 (Feb 21, 2021)

erikmannie said:


> Question: why don’t people with inch pitch leadscrews leave the half nut engaged throughout the whole operation for Imperial threading as well, as we do with metric threading? It is no trouble at all, and there is no worry about missing the mark on the thread dial. It would coast the same distance if I used the E-stop button.
> 
> Second question: I’m curious to see what is going to happen when I try a much smaller safety groove and stop the threading pass with my foot brake. When I disengage my power lever to stop power, it coasts for about 8 mm as the chuck is spinning down.



First question:  Because it is easier to just manually run the carriage back to the starting position.  Also, with a thread dial, you're sure to be able to pick up your sync.

Second question:  I don't really depend that much on a safely groove.  I rapidly pull back the cross slide once I hit my end-of-thread mark.


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## markba633csi (Feb 21, 2021)

The thread dial would save time if you were doing lots of repetitive threading jobs in a production shop like in the olden days, especially when using a slow spindle speed w/backgears
-M


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## Ischgl99 (Feb 21, 2021)

erikmannie said:


> Here is the link to the threading tool:
> 
> 
> 
> ...


Cool idea!

Sounds like you are doing the metric threading for your own knowledge.  The Germans have a standard for everything, so of course one for the thread relief.  You have to pay for the German standards and it’s a copyright violation to publicly post the standards, but the Indians decided to use many of them for their own.  This link shows how they do a thread relief to DIN 76-1 standards.



			https://law.resource.org/pub/in/bis/S01/is.1369.2.1993.pdf
		


And this is a link to how they do undercuts for bearings, gears, etc that butt up against a shoulder according to DIN 509



			https://law.resource.org/pub/in/bis/S01/is.3428.2009.pdf


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## mattthemuppet2 (Feb 21, 2021)

doesn't look like there's any back rake on the threading tool - I found I got a similar finish with a flat top HSS threading tool. I don't get the same problem with a carbide threading insert with back rake.

Having the runoff groove the same as the minor diameter of the thread is actually pretty useful as it gives a nice visual indicator for when you have reached full thread depth as you'll get a scratch pass in the runoff groove.

Plus side of the half nuts is that you can use a much shorter runoff groove as the carriage stops instantly (or thread at a higher rpm). You can even disengage the half nuts with metric threads as long as the carriage doesn't move far enough for a complete revolution of the threading dial. Then retract the tool, wind the carriage back to the threading dial mark, re-engage the halfnuts and reverse the lathe back to the start.


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## mikey (Feb 21, 2021)

7milesup said:


> I have done no threading on my lathe.  Yet.
> I am trying to understand the helix angle comment.  Is the angle (pitch) of the thread so great that the trailing portion of the thread is in interference with the trailing part of the cutter.  Just trying to wrap my head around this.
> As a side note, Martin Cleeve's book "Screwcutting in the Lathe" just arrived at my door two days ago.  Have only had a chance to look at the first few pages so far.



Have a look through this thread and see if it helps clarify helix angles for you.

Edit: I think Cleeve's book should be required reading for hobby guys.


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## mikey (Feb 21, 2021)

erikmannie said:


> The (single, see photo) bolt was tight, and it is horizontal.
> 
> I’m glad you told me that about the thread relief (safety groove). I have been making it the minor diameter.



Okay, the helix angle of your cutter can be adjusted with the set screws on the side. The Aloris blade has no relief angle under the cutting edge. It relies on the 12 degree angle it is held at for relief; this may not be enough. If this is really the issue on the torn trailing edge and flank then advancing the top set screw a fraction of a turn and retracting the lower one will tip the blade towards the chuck. That may clean up that trailing edge. 

One advantage of the deeper thread relief is that it cleans up the tail of the last thread for a very clean finish. This is good workmanship, Erik.


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## benmychree (Feb 21, 2021)

I think that introducing a back rake to a threading tool will change the thread flank angle, not a good idea.  The reason that we disengage the half nuts is to save time in running back to the right hand end to start a new pass, whether or not this saves time depends on the length of the thread, for short threads, it may make sense to leave the half nuts engaged in running back to the starting point, for long threads, decidedly not.


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## mattthemuppet2 (Feb 21, 2021)

benmychree said:


> I think that introducing a back rake to a threading tool will change the thread flank angle, not a good idea.



only if you don't take that into account when creating the angle of the tool to cut the thread. Maybe hard to do by hand (why I didn't do it) but presumably straight forward when creating carbide inserts, otherwise all those mass produced parts created using laydown threading inserts would have incorrect thread geometry, right?


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## erikmannie (Feb 22, 2021)

Thanks for all the feedback. I am sure looking forward to 7 days of nothing but metric threading.

The past year, I have picked up 4 or 5 HSS preground 60° tool bits made from 3/8” and 1/2” import HSS. I also have import as well as Aloris laydown carbide inserts on threading bars which are best suited to interior threading.

For those who leave their half nuts engaged throughout the whole process and set their compound angle at 30°, please tell me that nobody is plowing through their threads backwards (i.e. not backing off the cross slide) on their way back to the tailstock end (and calling it a spring pass). Just because you can doesn’t mean you should.


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## Ischgl99 (Feb 22, 2021)

For smaller threads, you don’t need to use the compound and can feed straight in if you wanted to give that a try.  I’ve done that up to 1.5mm so far and it worked well.  Since you are doing this for fun, that might be something to see how you like it compared to the traditional method.

Some people have built flip up threading tool holders so that you don’t need to retract the cross slide when running the carriage backwards to the start position.  When you reverse the spindle direction, the tool holder lifts up and rides the thread back without doing any cutting.  I have one partially built that I will get around to one of these days to give it a try.


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## SLK001 (Feb 22, 2021)

erikmannie said:


> For those who leave their half nuts engaged throughout the whole process and set their compound angle at 30°, please tell me that nobody is plowing through their threads backwards (i.e. not backing off the cross slide) on their way back to the tailstock end (and calling it a spring pass). Just because you can doesn’t mean you should.



That's a terrible idea.  There is enough slack in the gearing to completely throw off the alignment when you shift it in reverse like that.  You can actually damage the threads you just cut when you do this.


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## erikmannie (Feb 22, 2021)

This morning I am doing an M10-1.25. My thread relief is 8.168 mm & the chart says “minimum Minor Diameter of 8.315 mm”, so there will be no cutting in the thread relief.

I turned the hex steel down to 9.94 mm & the chart says “Major Diameter between 9.760 mm and 9.972 mm”.

The tip on the threading blade is no longer new (see photo).




I recentered the tool (it required lowering the tip about .007”!).


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## erikmannie (Feb 22, 2021)

Scratch pass shows 1.25 mm pitch and no taper:


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## erikmannie (Feb 22, 2021)

What it looks like after 4-5 passes (dialing in the compound .004” each pass) and a spring pass. Hardware store bolt next to it.


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## erikmannie (Feb 22, 2021)

The pitch diameter of the hardware store bolt is 9.072 mm. The chart says that the pitch diameter range is 9.042 to 9.160 mm.

I just measured the pitch diameter of the one that I am cutting and I got 9.464 mm, so I have more passes to make.

I need to go in at least another .30 mm (about .012”). I will dial in .002” on the compound, do a spring pass and remeasure.





__





						External Metric Thread Table Chart and Fastener Sizes M1.6 - M18
					

Standard metric external thread size M1.6 to M18 per. ANSI/ASME B1.13M-1995



					www.engineersedge.com


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## Ischgl99 (Feb 22, 2021)

I’ve found the hardware from the store is a bit looser than the specs call for.  I made a table locking bolt for my mill and used a nut to test, it didn’t fit and needed to chase it with a die.


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## erikmannie (Feb 22, 2021)

My fat belly bumped the cross slide handwheel and moved the cross slide in .0006” right as the spring pass began. That’s not good.

I was watching to see how many chips I got on the spring pass. I should have looked at the DRO sooner rather than later.


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## erikmannie (Feb 22, 2021)

I used my Shars 0-1” screw thread mic, and measured the pitch diameter to be 9.329 mm.

I won’t even put a nut on there until I see 9.160 mm.

Here’s a picture of what it looks like after you dial in the cross slide .0006” too much on a spring pass.


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## Aukai (Feb 22, 2021)

OOOOH, the dreaded belly bump, I hate that, done it too....


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## erikmannie (Feb 22, 2021)

I got the pitch diameter down to 9.126 mm and I need to go to the hardware store to buy an M10-1.25 nut.


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## mikey (Feb 22, 2021)

So, what happened with the torn, chattering trailing edge?


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## erikmannie (Feb 22, 2021)

mikey said:


> So, what happened with the torn, chattering trailing edge?



That was for an M14-2.0. I did not have a nut to test it yesterday afternoon so I turned it down to this M10-1.25.

At this point, I have a full selection of M4 through M18 bolts, many in both fine and coarse. I will try to make it so this thread is not redundant.

The M10-1.25 nut fit:


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## mikey (Feb 22, 2021)

So, I ask again, what happened to the torn trailing edge? Is the issue resolved and if so, what did you do to resolve it?


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## erikmannie (Feb 22, 2021)

mikey said:


> So, I ask again, what happened to the torn trailing edge? Is the issue resolved and if so, what did you do to resolve it?



I did not resolve it. I turned it down to 10 mm. My afternoon blew up yesterday with family stuff, and by the time I was able to regroup the hardware store was closed and I just started over with M10-1.25.

I had chosen M14-2.0 without owning such a nut. Also, the first attempt was awful. I was dialing in .010” on the compound most of the time, and we wonder why it tore. Sometimes you just need a fresh start.


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## mikey (Feb 22, 2021)

Try angling your cutter like I mentioned and see what  happens. The other option is to grind a decent threading tool and give that a try. If you do this, use 15 degree relief angles and I bet you won't have any torn threads due to helix angle issues.


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## Ischgl99 (Feb 22, 2021)

Mikey may have found your problem with the larger thread.  If you go to the Dorian website and download their threading tooling catalog, page E20 has a helix angle chart for various pitches and diameters.  The M14x2 has an angle around 3 degrees, and the M10x1.25 looks to be about 2.5 degrees.  The angle you have your threading tool set to might be enough for the smaller thread, but not enough for the larger one.


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## erikmannie (Feb 22, 2021)

So now I am back to M14-2.0, starting with a female thread. Anything smaller than that (e.g. M12) & my boring bar wouldn’t fit in there. As it is, I had to use a boring bar from my smaller lathe.

Also, I put on the 3 jaw chuck for the hex bar.

This hole (Minor Diameter, from link) is 12.12 mm which is less than 12.210 mm so I can start to cut threads.





__





						Internal Metric Thread and Fastener Sizes M 9 - M 24
					

Metric internal thread sizes M 9 - M 24 per. ANSI/ASME B1.13M-1995. These thread sizes and classes represent bolts and screws, as well, as other standard internal threads.



					www.engineersedge.com


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## Bi11Hudson (Feb 22, 2021)

erikmannie said:


> Question: why don’t people with inch pitch leadscrews leave the half nut engaged throughout the whole operation for Imperial threading as well, as we do with metric threading? It is no trouble at all, and there is no worry about missing the mark on the thread dial. It would coast the same distance if I used the E-stop button.
> 
> Second question: I’m curious to see what is going to happen when I try a much smaller safety groove and stop the threading pass with my foot brake. When I disengage my power lever to stop power, it coasts for about 8 mm as the chuck is spinning down.


1)     I do reverse the machine after backing out the cross slide for both imperial and metric threading. Because my machine is loose *AND* I'm prone to lose track of what I'm doing. Cutting metric almost as often as imperial threads, it helps me to have a routine to follow.

2)     Once the tool is past the cut and power is switched off, braking should have little effect beyond wear and tear on the machine. And that will vary depending on the condition of the machine. Just be sure the switch is off. . .

One thing I noticed was your tool appeared to feed in at 90 degrees. If that is so, the tool is cutting on both sides. I was taught old school, where the feed in is at 30 degrees. Actually 29-1/2. . . So the tool only cuts on the one side.

.


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## erikmannie (Feb 23, 2021)

I have centered the tip of the 60° insert.




The most that I will be able to go in there is 1”:




I should have seen that coming and planned for a nut with a length less than 1” and used the open space behind it for a thread relief.

Now I am going to have to go in there with a boring bar and make a thread relief (safety groove).


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## erikmannie (Feb 23, 2021)

Bi11Hudson said:


> 1)     I do reverse the machine after backing out the cross slide for both imperial and metric threading. Because my machine is loose *AND* I'm prone to lose track of what I'm doing. Cutting metric almost as often as imperial threads, it helps me to have a routine to follow.
> 
> 2)     Once the tool is past the cut and power is switched off, braking should have little effect beyond wear and tear on the machine. And that will vary depending on the condition of the machine. Just be sure the switch is off. . .
> 
> ...



Thanks! 

For external threading, I am only feeding in using my compound hand wheel so I believe I am going in at 30°. I usually set mine to 29 1/2°, also.


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## mattthemuppet2 (Feb 23, 2021)

another tip Erik - chamfer the beginning and end of the piece you will be threading before you cut the threads. You can use the threading tool to do this or a dedicated chamfering cutter, doesn't really matter. Makes the finished product look and work better.


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## erikmannie (Feb 23, 2021)

I failed. The Aloris threading bar that I’m using specifies that the beginning hole must be a 1/2” or larger, and my beginning hole was just a hair over 12 mm.

It went down very badly. It would make a fine cut going in, and then there was not enough room to retract the threading bar, so the 60° tip did a little damage on its way out. Very ugly.


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## erikmannie (Feb 23, 2021)

I have an M20-2.5 nut & bolt. I am going to try to make a nut.

It looks like I start with a (chamfered!) hole (minor diameter from link) of between 17.244 and 17.744 mm. 

An 11/16” drill is 17.46 mm so that should work.





__





						Metric Internal Thread Dimensions Chart
					





					amesweb.info


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## erikmannie (Feb 23, 2021)

That was challenging. I busted an import HSS preground grooving/parting tool because I was feeding in too quickly; I may have also had too much tool stickout.

Then I got sidetracked & struggled to drill a hole in my MT drift so that it would hang on a hook on the wall. The material of the drift (tool steel?)  was harder than the material (HSS?) of the import drill.

I had not noticed until I did this that the interior of a nut this size does not have a crested V at the minor diameter. I will show my threads and a stock nut in the photos. I was expecting a crested V.

The interior threading went fine. I came out a radial .09275” on the DRO. I was getting almost as many chips on the spring passes that I was on the threading passes. I don’t know why that is, but it was frustrating.

Most of the passes were a radial .005”.


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## erikmannie (Feb 23, 2021)

The bolt fits fine, just like the nut from the store.




I’m going to make another one now just like it, and try to make no mistakes. I will post photos of any interesting steps.


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## Boswell (Feb 23, 2021)

Nice Nut !


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## erikmannie (Feb 23, 2021)

This is 1” steel hex, 3/4” long. I made my best effort for surface finish on the facing. See also the 30° chamfer. The center drill is for an 11/16” tapered shank drill.


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## erikmannie (Feb 23, 2021)

40° chamfer for the threading bar to head in:


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## erikmannie (Feb 23, 2021)

So this time I was not at all aggressive with the DOC. The most I ever did was .005” radial, but I noticed that I was getting so many chips on the spring passes that I just start doing radial cuts of .002” max. You wouldn’t believe how many chips I was getting even on a third or fourth spring pass: it’s a mystery.

Surprisingly, I tested the nut after coming out only .04275”, and the nut could be hand tightened (with difficulty) all the way in.

I was very generous with the oil-based CF.

I’m going to go back to where I was and just do spring passes. I wonder if the insert will ever come out clean.


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## erikmannie (Feb 23, 2021)

This is after 4 spring passes. A guy could overshoot it with spring passes.


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## mikey (Feb 23, 2021)

Try a Micro 100 bar. They have the stiffness of carbide but cut like HSS.


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## erikmannie (Feb 23, 2021)

This is what it looks like before I test fit the bolt:


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## erikmannie (Feb 23, 2021)

While I had the chance, I did a concentric 40° chamfer and faced off .014” with HSS. 380 RPM, .009”/rev feed.


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## Aukai (Feb 23, 2021)

Looks very nice.


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