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  1. #21
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    No relief cut needed on a barrel w/recoil lug like R700's, but try that on a Mauser or any other rifle without it... need relief on either the barrel, or receiver.

  2. #22
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    Quote Originally Posted by tobnpr View Post
    No relief cut needed on a barrel w/recoil lug like R700's, but try that on a Mauser or any other rifle without it... need relief on either the barrel, or receiver.

    I will disagree with that. Most receivers have a thread relief in the front ring. If it doesn't I always cut a small relief when I have the receiver in the lathe to skim cut the front rig to square it up.

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  4. #23
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    Quote Originally Posted by Butch Lambert View Post
    I will disagree with that. Most receivers have a thread relief in the front ring. If it doesn't I always cut a small relief when I have the receiver in the lathe to skim cut the front rig to square it up.
    Did this with the Mauser I built in gunsmithing school. Fortunately I get to work on nicer stuff now.

    Sent from my Pixel 2 using Tapatalk

  5. #24
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    Quote Originally Posted by michiganbuck View Post
    Look at you chuck with a slip of tape on one jaw at 50 or 70 rpm and note how long it takes the tape to come around. That is a lot of time for you to pull out and drop the half nut / or shut the feed..threading should be easy with practicing.
    (60 seconds divided by a 20 thread)

    I knew a guy who put a sharpie line on his part and watched for it to come to a certain place. Turn of tape around the part with a sharpy line.. agree just looking at the thread can be harder than using a simple help device.

    Wooden broom stick is a good practice stock.. 1/2" wood dowel from the hardware store. 3/8 or 1/2 aluminum dowel..

    Yes soft wood does not lathe cut very will so don't expect the nice clean cut like yo might find on steel or aluminum, so this is mostly just for practice for pull out and ending to a shoulder.

    A very sharp HSS bit would do best , with it having a high amount if side rake angle of perhaps 15-20*
    https://littlemachineshop.com/images...ngToolBits.pdf
    I always recommend thick walled PVC pipe as a intro to single point threading.

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  7. #25
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    9a20f26b-ff85-4c6c-9bd9-9933f6a81690.jpgthis is one I did tonight. I don’t understand why it slopes more to one side than the other? I have the compound set at 29.5 like a machinist friend of mine told me to do. And I am using the compounds dial. Am I not supposed to use that dial to feed the tool in?

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    You need to be feeding 29.5* in from perpendicular to the carriage. If 9 o’clock is 0* you want to be at 11 o’clock not 10.

    There was a recent thread on threading that went on for pages I will see if I can find it.

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  10. #27
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    I agrees with Hazzart. I did one just like that way back. Had the 29.5 degrees measured from parallel, not perpendicular. Resulted in the cutting tool advancing at a roughly 60 degree angle and made funny ramps just like yours.

    If perpendicular, or 90 degrees from the barrel is considered zero, then its 29.5 degrees from that zero. IE, 29.5 degrees from plunging straight in is what you want. Likely doesn't correspond to the way the degrees are marked on your compound slide. Sure didn't on mine and it fooled me the first time I tried it.

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    I will say though that for most small threads just leave the compound at 0 and feed in with the apron not the cross slide it makes about zero difference for most every day threads.

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    as previously mentioned your lathe likely needs to have the compound set to about 61 degrees...your marks probably stop at 60 but it's not critical so just guesstimate 61 deg for now.....later you may want to make a new reference mark, and when/if you do, 27.5 deg(or 62.5 if your lathe is marked as I suspect) will cover both 60 degree threads and 55 deg Whitworth, and you will eventually run into Whitworth.

  14. #30
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    Quote Originally Posted by kenton View Post
    I always recommend thick walled PVC pipe as a intro to single point threading.
    Cool idea. I used lengths of aluminum and steel rods to learn, after a few it became second nature. Now I need better eyes to see the markings.

    Jeff

    Sent from my XT1254 using Tapatalk

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    I can't really take credit for the idea, I read it on this forum.

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    So in other words, the scale on my compound may be wrong? Or inaccurate? I will try and post some pictures after bit

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    QT:[So in other words, the scale on my compound may be wrong? Or inaccurate? I will try and post some pictures after bit]
    Perhaps not wrong or inaccurate but just that the lathe manufacture standards of where to put the zero and start off the protractor are not what you expected. So the compound set at 30* angle, the compound protractor number may not be at 30.

    To be safe and sensible on a lathe it seems one should be able to eye-ball visualize 90* 30* and 45* along with understanding why the 30* or about that relates to correct threading. I think we were taught that before allowed to run a lathe. The compound is set at about the same angle of the right-side of the tool bit, then you give it a half degree tweak back before that mark. That is so the right side of the tool bit just follows or skims along that (left) side of the thread being cut. and so only the lead side (left side) of the tool bit is doing the cutting. Yes the small tweak off 30* will give a tickle cut to the right side of the thread being cut.

    Or just leave it at the mark and in-feed at compound 30* angle (what ever number make that angle correct)and then for finish in-feed cross feed .001 on your last two passes.

    Cutting steel and aluminum the lead side (left edge) of the tool bit has some positive top rake angle...so the other edge (right edge) is negative to any cutting.

    Guess a new lathe guy should look over his hand held protractor to visualize the about 30* positioning of the compound so to know what 30* looks like. (and then look at what number is there on the compound protractor.)

    Yes this all relating to the lathe going forward and the tool bit traveling toward the head stock,

    To also note a burr or bug may rise up on your thread so a good idea hone or fine-file skim the OD before you last finishing passes.
    Last edited by michiganbuck; 04-23-2019 at 09:36 PM.

  18. #34
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    94b1b67b-99d7-4007-94c3-83713499784f.jpge760d20d-8d1c-4b04-9f76-0da00ea5b073.jpgThis is how I have it setup

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    f6905f5c-3e34-4106-90f4-19e14cd68668.jpghere is the other picture

  20. #36
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    again, you need to set to about 61 deg, which will be a hair off your scale.

    or just feed in with the cross slide, lay down style ER like you have will work fine that way too.

  21. #37
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    Looking at your photos in post 34..it seems using a fish tail gauge would tell you that you are way off the correct angle.

  22. #38
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    You do not use 31 degrees! 29 has been determined to be the standard compound angle. On those lathes with the scale for the compound shifted 90 degrees then use 61 degrees. Simply put the reason for 29 degrees is because the scale is only a reference. Slightly less is OK, 30 degrees is perfect but if the scale is slightly off a greater angle will result in steps on the right side of a right hand thread. Plunging the thread and not using the compound on very fine threads is OK but larger threads will result in a ripping appearance on the right side of a right hand thread. Think about it the cutting edge is pulling away from the right side. Cutter clearance is important, being a very fast feed rate on course threads the lower part of the right side of the right hand thread tool has to compensate for the thread lead. I don't cut below center, dies are ground with the cutting edges above center but when learning use center. What ever you do do not use a carriage stop if you don't have a lathe that will automatically Disengage the lead screw. That jerk Tubalcain how ever it's spelled is not a good source! His threading video shows him setting up on a South Bend lathe but he then is threading on A Clausing I think and is using a carriage stop that will disengage the lead screw on the lathe he's threading on. We had a few come here and ask how to set the carriage stop after viewing his video! Don't use it as you can damage your lathe!!

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  24. #39
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    Quote Originally Posted by Turner421 View Post
    94b1b67b-99d7-4007-94c3-83713499784f.jpge760d20d-8d1c-4b04-9f76-0da00ea5b073.jpgThis is how I have it setup
    Sir it appears you have it set up 29 degrees off of parallel. It should be 29 off of perpendicular. Your compound handle should be closer to your cross slide handle, if that makes any sense.

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  26. #40
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    Quote Originally Posted by Dieseldoc View Post
    Sir it appears you have it set up 29 degrees off of parallel. It should be 29 off of perpendicular. Your compound handle should be closer to your cross slide handle, if that makes any sense.
    +1. And I concur that 29-29.5 deg (or 61) is correct while 31 (which is what car2's diagram in post 37) is not.


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