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Thread: Repeat Distance method
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9th Dec 2019, 02:07 PM #1Novice
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Repeat Distance method
Hello all, Does anyone know how to cut awkward pitch threads with the Repeat Distance method. Or any other method of tracking the thread when chasing dial won't do it or you cant reverse.
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9th Dec 2019, 02:44 PM #2Most Valued Member
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My method of solving this problem on a lathe that couldn't reverse was to make a handle for the far end of the headstock bore and just reverse it by hand. (Note you need to make the handle spring loaded or take it out between passes)
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9th Dec 2019, 06:26 PM #3Philomath in training
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What pitch are you trying to cut?
Michael
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9th Dec 2019, 09:24 PM #4Novice
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9th Dec 2019, 09:40 PM #5Novice
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repeat distance method
Hi, michael, it's actully 1.41 mm pitch . with drive gear 28 and leadscrew gear 60 on a 3mm lead screw. this is almost exactly 18 TPI which is what I need. I think there were two ways of cutting a thread without chasing dial or reversing the lathe though. will look into it further.
cheers.
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10th Dec 2019, 07:43 AM #6
Lathe winding handle !
Hi Brookerbj,
A lathe handle is quite an easy turning job ! These are pictures of mine. I made this quite some time ago and did a write up on this forum.
21022015-00.JPG 21022015-01.JPG
I had an old plastic washing machine drum pulley just kicking about and getting in the way so I pressed it into service for winding back the lathe spindle. It has come in very useful.
21022015-04.jpg
I made a fitting to go into the original rectangular hole in the middle of the pulley and welded a length of tube to it. The tube is a good sliding fit in the spindle bore and extends to about halfway down the headstock.
21022015-03.JPG 21022015-05.JPG
I cut four slits in the end of the tube and drilled holes through to stop the tube from permanently deforming when the cone shaped wedge forced the four tube sections against the inside of the spindle bore. I made no attempt to machine a taper in the end of the tube, I just ran a countersink bit on the end before slitting.
There is a rod running down the inside that is threaded at both ends. The cone is Loctited on one end and a nut and washer used at the other to pull the rod and expand the end of the tube in the spindle.
The brass ring is just a stop so that the pulley does not hit the gear cover. I added a handle to make turning the pulley wheel more convenient.Best Regards:
Baron J.
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10th Dec 2019, 06:22 PM #7Gear expert in training
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Found this in a old machine operation book, starts at the bottom of page 454 under the heading "Cutting a thread without the reverse belt" and refers to the "definite distance" method
IMG_20191210_180634.jpgIMG_20191210_180649.jpg
It does, however, seem to imply that the thread being cut must be in the same units as the leadscrew, so it might not help you. You could possibly calculate how far out you'd be, as it would be the same amount each pass, and compensate by moving the compound, but now it's starting to get way too complicated...
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11th Dec 2019, 01:59 AM #8Golden Member
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Some time ago I made a similar arrangement for the old Brackenbury and Austin lathe, but instead of the wheel and handle made a two pin coupling. One half is held in in the headstock spindle as you have shown. The other half is held in a portable drill's chuck - crude, but for occasional use it saves a lot of winding with a handle. Obviously there is a limit to the lathe size for this arrangement, but it works well on the 9x18 B&A lathe. I take the back gear out of engagement while rewinding. This means that the drill does not have to handle the extra resistance of the back gears, countershaft and motor.
Frank.
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11th Dec 2019, 07:45 AM #9
Hi Frank,
Thankyou for your post.
I went with a wheel in preference to using a power tool, because whilst I can reverse the lathe motor and wind the saddle back quite quickly, you have very little control when tapping a hole, particularly with a small straight flute tap that very often is easily broken. Using the lathe wheel gives you feel and control which you don't get under power.Best Regards:
Baron J.
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11th Dec 2019, 08:00 AM #10Golden Member
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Hi Baron,
Fair enough. My ten inch countershaft pulley is reasonably accessible: I use it for tapping in the same way as you describe.
Frank.
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