# Threading issues



## Leadfootsmurf92 (Jan 26, 2018)

Good evening, I'm new to the forum, and new to machining. I have a HF 7x10 lathe and the small HF mill. I've been working on threading on the lathe, and have so far not been successful. I am currently using a sandvik tool holder with a 16er ag60 insert. Compound is set at 29.5 degrees, and I've given up using the threading dial, and resorted to just backing off and reversing the lathe to restart the thread. I'm still having issues with the insert not following the existing thread. Any help would be greatly appreciated!

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## mikey (Jan 26, 2018)

Welcome to HM, Smurf!

The first thing that came to my mind here is to wonder if your compound is set to 29.5 or is it 60.5 degrees. The degree markings vary with the lathe and on my Emco lathe, I have to set the compound to 60.5 to get the right angle. Otherwise, the thread form is distorted.

When the compound angle is set correctly, your thread dial indicator will work properly. Why not give it a try or maybe show us a pic of your set up and the problems you are having.


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## Leadfootsmurf92 (Jan 26, 2018)

I just tightened a screw that pulled some of the slop out of what i assume would be the x axis. I think that will help (i will try again tomorrow). Here are some pics of my setup. 
	

		
			
		

		
	






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## mikey (Jan 26, 2018)

Yes, your cross slide movement is the X-axis.

Judging from the pics, you compound is set at the wrong angle. It should look like this:



Maybe this one will help:




See the difference in the angle? Try setting the index under the compound to 60.5 degrees and try again.


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## higgite (Jan 26, 2018)

In before someone says "plunge cut and forget all these silly angles". 

Mikey beat me to it with the angle analysis. I type too slow. If you don't already have one, you might want to pick up a protractor similar to this one. And don't fret, your mistake is a common one.

Tom


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## Leadfootsmurf92 (Jan 26, 2018)

Ok that makes sense. But my angle marks only go to 45, so I need to use a different method to calculate the angle? 

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## middle.road (Jan 26, 2018)

Hit up YouTube, search on threading videos. this is one of my favourites: 



I used it to get out of a bind threading some 7/8"-32 piece parts. 
@*mikey's *recommendations are on the mark and valid. Follow them. 
The whole 29.5° method is like discussing religion or politics. But it's been done that way for so long that it is
taken for granted as being the best and only method.


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## Leadfootsmurf92 (Jan 26, 2018)

Ha i just saw your response. Ok I will get one of those and give it a try! 

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## Leadfootsmurf92 (Jan 26, 2018)

7/8-32 was the thread I was just trying before I posted this! It started good, and then went down hill lol. 

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## mikey (Jan 26, 2018)

Leadfootsmurf92 said:


> Ok that makes sense. But my angle marks only go to 45, so I need to use a different method to calculate the angle?
> 
> Sent from my SM-G935P using Tapatalk



Use a protractor like Tom/@higgite said and set it once. Then make an angle gauge from plywood/plastic/aluminum/whatever and reference it off your chuck face and the side of your compound. Then its a snap to set the compound at the right angle whenever you thread something and away you go.


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## Z2V (Jan 26, 2018)

Smurf
I’ll throw this in the mix. It’s from the PM1236 owners manual.


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## middle.road (Jan 26, 2018)

An aquintance has an HF lathe that he wants me to repair. I'm going to have to see if it's a 7x10 and then I'm gong to figure out how
the bloody compound is laid out just to satisfy my curiosity... 
I would have thought that it was scribed to some sort of a standard. but then again....

BTW, just for the record, 7/8"-32 is not a 'fun' thread to start out on. Just in case you were wondering... 
There's no 'wiggle' room and of course one always messes up on the last pass....


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## Z2V (Jan 26, 2018)

middle.road said:


> BTW, just for the record, 7/8"-32 is not a 'fun' thread to start out on. Just in case you were wondering...
> There's no 'wiggle' room and of course one always messes up on the last pass....



I’ve felt that “last pass “ pain several times.


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## ddickey (Jan 26, 2018)

Leadfootsmurf92 said:


> Ok that makes sense. But my angle marks only go to 45, so I need to use a different method to calculate the angle?
> 
> Sent from my SM-G935P using Tapatalk


Make sure you check the front of the cross slide (facing the head stock). Most lathes have more than one spot to check angles.


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## Dave Paine (Jan 26, 2018)

This is a common problem for folks starting out.   I had the same issue.    The compound scale did not go far enough.    I made a simple jig to set the compound.   See my post #11 in this earlier thread.

Threading issue


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## Leadfootsmurf92 (Jan 26, 2018)

Thank you everyone for all of your help! I am going to adjust my compound tonight after work and try again, hopefully with better results!  

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## RJSakowski (Jan 26, 2018)

Here is my solution for setting the 29.5º angle for threading.  https://www.hobby-machinist.com/threads/29-5-deg-angle-tool-for-lathe.34541/  Another way would be to use a draftsman's 30-60-90 triangle to set the compound to set the angle between the side of the compound and the face of the chuck and just bump it slightly to reduce to less than 30º.  The actual angle isn't critical as long as it isn't more than 30º.


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## benmychree (Jan 26, 2018)

I was taught to use a 30 degree setting of the compound for threading in my high school machine shop class by the teacher who had taught in the apprentice school at Mare Island Navy Yard; the trick for cleaning up the backside of the thread was to slightly drag on the carriage handwheel on the last cleanup cut; this was also observed by all the machinists that I knew in the shop where I apprenticed.
In the instance of the lathe with no markings shown in this thread, I would establish the correct angle with a protractor or whatever means is at hand, then scribe a line on the cross slide against the compound for future reference.


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## higgite (Jan 26, 2018)

Concerning making a jig or template to quickly set the compound angle for threading, I kept saying I was going to make one but never got a round tuit. Instead, after using a protractor about a dozen times to set the angle (and being efficient at physical activity, which some who know me have erroneously called "lazy"), I did the same as benmychree and scribed a reference mark on the cross slide. But, my compound is slightly elevated above cross slide, so I marked the cross slide at the zero degrees mark on the compound degree scale when it was set for threading, much like the factory mark on the PM1236 in Z2V's post above.

Tom


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## mikey (Jan 26, 2018)

Hey Smurf, you can see all the guys who understand the issue, right? Guess how we know about it! You are not the first and won't be the last.  

Bet your thread dial indicator will work like a charm now!


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## TakeDeadAim (Jan 28, 2018)

Ok its 0600 and I have not been able to sleep due to back and leg pain.  So Ill throw this into the mix just to stir the pot.  It is NOT necessary to cut threads with the compound.  In fact I don't even have a compound on my lathe.  It was the weakest link in terms of chatter on mine and most lathes.  So I took it off and could not be happier.  Just square up your tool using the good old fish tail tool or in the case of most insert tools tram the shank with a dial indicator.  When you cut the thread just advance the tool straight into the work slowly, use a good cutting fluid for the type of material your cutting and viola decent threads.


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## Leadfootsmurf92 (Jan 28, 2018)

I would like to thank everyone for their help! It has been greatly appreciated. I have made ground on my thread cutting abilities, and i must say that I'm pretty excited. I currently changed my compound angle (for those recommending to not worry about angle and just dive straight in, I'm also going to try that), and I believe I found the key to getting my cheap lathe to repeat the same thread path. I found that if I disengage the half nut after a threading pass, turn off the spindle and hand crank it back to the starting point, re engage the half nut in the appropriate position, then restart the lathe, it will pick up the thread again. I still need to work on cleaning up the thread, and getting to the right depth (I am going to purchase a pitch Mic I think). I have attached a pic of the .375-24 thread i attempted. Not great, but it's better than before! 
	

		
			
		

		
	




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## TTD (Jan 29, 2018)

Hey, that doesn't look half bad at all!   If anything, I would just run a 3/8-24 die over it now to clean up the threads a bit & call it done.



Leadfootsmurf92 said:


> I found that if I disengage the half nut after a threading pass, turn off the spindle and hand crank it back to the starting point, *re engage the half nut in the appropriate position, then restart the lathe*, it will pick up the thread again.


Now, I am no single-point threading expert by a loooong shot, so I'm more "thinking out loud" here than giving advice, but I wonder if you could just leave the half nut engaged the entire time? When you're done a pass (threading tool in relief groove), shut the lathe off, flip the lead screw lever to "reverse" then turn lathe back on & let tool basically thread away from chuck until it clears the work....kinda like a spring pass but in reverse. Crank cross slide in to your desired DOC & repeat (I don't use compound when threading).


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## Dave Paine (Jan 29, 2018)

TTD said:


> Now, I am no single-point threading expert by a loooong shot, so I'm more "thinking out loud" here than giving advice, but I wonder if you could just leave the half nut engaged the entire time?



I often leave the half nut engaged but I back off the compound one full turn, or when making a deep thread like 8 tpi I will back off two full turns when I get close to the bottom of the thread.    I then put the lathe in reverse to get back to the starting point.

I do not want the cutting tool threading on the reverse step since backlash in the lead screw will widen the thread.

I have used the cross slide to plunge cut a thread for fine threads, but when I am making 8 tpi threads for wood lathe tools, I use the compound.  The chips get big for such a thread.  I do not want to risk breaking anything by plunge cutting such a thread.


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## dtsh (Jan 29, 2018)

TTD said:


> When you're done a pass (threading tool in relief groove), shut the lathe off, flip the lead screw lever to "reverse" then turn lathe back on & let tool basically thread away from chuck until it clears the work....kinda like a spring pass but in reverse. Crank cross slide in to your desired DOC & repeat (I don't use compound when threading).



Assuming you had tight tolerances in your leadscrew, it might work, but I think for many of us, we'd just end up with mangled threads.


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## TTD (Jan 29, 2018)

Dave Paine said:


> I often leave the half nut engaged but I back off the compound one full turn, or when making a deep thread like 8 tpi I will back off two full turns when I get close to the bottom of the thread. I then put the lathe in reverse to get back to the starting point.
> 
> I do not want the cutting tool threading on the reverse step since backlash in the lead screw will widen the thread.




Very good points, Dave. Thanks for that little tidbit!


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## TTD (Jan 29, 2018)

dtsh said:


> Assuming you had tight tolerances in your leadscrew, it might work



LOL....I have a (Craftex) 7x12 Chinese mini lathe...."tight tolerances" are nowhere to be found!


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## royesses (Jan 31, 2018)

Maybe I'm overthinking this but you have a 30°, a zero° and a 30° marked on your compound already. Just scribe a line at both 30.5° marks when set to zero. Then you use either line you have scribed as zero and set 30° on the new zero line resulting in 29.5° set for threading. Or am I wrong?


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## mksj (Feb 1, 2018)

I was playing around with several ideas on trying to cut metric threads, disengaging the half-nut and then seeing if I could pick up the thread again on the next pass. Typicality you cannot use the threading dial with metric threads on an imperial lathe w/o some creative methods to get you back to the same starting alignment position. Bottom line, tried several methods and didn't work very well. In my opinion you are best leaving the half-nut engaged through the process when cutting metric treads. If you have a lathe that has electronic braking, it makes it very easy to stop in the relief grove, back the cutter out and reverse, then repeat your next pass without disengaging the half-nut. I tried it repeatedly at 100 RPM (not using any electronic stop), and I had no difficulty cutting a metric thread using this method. If you do not have some form of electronic braking then it can make this method more challenging because of the chuck spin down time. Whit electronic braking, I use 1 second braking when threading.

Since I use both electronic braking and an electronic stop, I cut all my threads (imperial and metric) with the half-nut engaged through the threading process. I have also reverted to using the cross slide to advance the cutter as this maintains the same stopping position of the cutter tip on every pass. I only cut a relief groove with my threading insert to slightly deeper than my expected maximum thread depth, the repeatably of the electronic stop system is 0.0002" so you can cut a thread to the relief groove/shoulder/blind cap internally easily with no drama.

I recently switched my threading holders to the lay down insert variety, both (external/internal) are made by Carmex (Iscar). I am using both Carmex 16IR AG60 BMA and Mitsubishi MMT16ER AG60 VP15TF threading inserts. The inserts have been much more durable than the TNMC/TPMC previously used and so far cut much cleaner complete threads. Example below is a M6 1.0 thread cut in O1 drill rod at 130 RPM to a shoulder and using the cross slide method.  I would have cut a wider relief grove if not using an electronic stop. As far a using the compound vs. cross slide, there are a number of different factors that come into play. Size/rigidity of your lathe and the robustness of the insert/cutting system are important factors. Smaller lathes would do better using the compound.  I do take shallower threading cuts using the cross slide, and for very coarse deep threads, using the compound can be easier on clearing the chip curl. When using the compound to cut  threads, I often do the final spring pass by slightly advancing the cross slide to clean both side of the thread groove evenly.







Quick method of setting your tool post parallel to the chuck using a 123 block. Just loosen the tool post nut bring it up against the chuck and holder using a 123 block as shown and tighten the nut. With inserts, once the holder is parallel to the chuck, the insert alignment will be true. There is no need to use a fish tail.


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## Tozguy (Feb 1, 2018)

TTD said:


> Hey, that doesn't look half bad at all!   If anything, I would just run a 3/8-24 die over it now to clean up the threads a bit & call it done.
> 
> *Is that not called cheating *
> 
> ...



*If you change the lead screw direction like that it will cut left hand threads on top of the right hand threads. Ask me how I know  *


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## Boris Ludwig (Feb 2, 2018)

This might help, it helped me with the technique


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## hss cutter (Feb 3, 2018)

On my atlas 10 lathe the dial is engaged at different start point for odd and even threads I can no longer remember what is what but I have done large metric and standard along with acme threads with pretty good success. so you may want to do a little bit of research on your dial.


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