Very new to machining an absolutely new to the math associated with machining. My question is if I change the thread pitch of my lead screw currently 10 threads per inch. How does that affect my dial indication and my thread/change gears?
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Crossfeed screw and lead screw thread pitch change questions
- Thread starter mac1911
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- Jan 4, 2021
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It changes them completely. An analogy might be, if my boss changes my hourly rate, how does that affect my paycheck? If the government changes tha rate I am taxed, how does that affect my paycheck? You would have to come up with completely new gear combinations to calculate feed rates or thread pitches.
On a cross slide or compound, the thread pitch is directly related to the dials. 10 tpi on a compound means that for every rotation of the handwheel, you move .100". Changing the pitch and the existing dial is worthless.
On a cross slide or compound, the thread pitch is directly related to the dials. 10 tpi on a compound means that for every rotation of the handwheel, you move .100". Changing the pitch and the existing dial is worthless.
If you change the pitch to an integer multiple or division, you can come out somewhat reasonably: a 20TPI screw would feed half as fast, your knobs would read twice the value that you actually dialed on, and your thread pitches would be half those on the threading box - note that that means that you might come up with some weird (non-standard) thread pitches, and that your threading range would be reduced - your coursest pitch would be double your current coursest pitch.
The opposite would happen if you went with a 5TP screw - your feeds would be twice as fast, your knobs would read half the value you had applied, and your threads would be twice those indicated in your setup. And you'd have to be darn fast to thread course pitches, because that apron is gonna move!
Oddball sizes (7, 9, 12, etc) would require a lot more calculation, and anyway you slice it your threading adjustments will never be the same unless you can work out an appropriate gear change to compensate.
GsT
The opposite would happen if you went with a 5TP screw - your feeds would be twice as fast, your knobs would read half the value you had applied, and your threads would be twice those indicated in your setup. And you'd have to be darn fast to thread course pitches, because that apron is gonna move!
Oddball sizes (7, 9, 12, etc) would require a lot more calculation, and anyway you slice it your threading adjustments will never be the same unless you can work out an appropriate gear change to compensate.
GsT
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- Jan 26, 2024
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as others have said, any change will change everything! Unless there is a very good reason to change the pitch I'd leave it as it is! I changed the leadscrew on my tool and cutter grinder, but that was simply so that I could have dials that showed the feed applied (the originals were blank and a strange thread!!)
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Why would you want to do that?
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- Apr 14, 2014
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I would agree with what's been said so far. I have 2 lathes in the shop. The older one has a 10 tpi lead screw and cross slide screws. The newer one has an 8 tpi leadscrew and cross slide screws. I have to remember that each turn of the cross slide on the older one advances the tool .100" while each turn of the cross-slide screw on the newer one advances the tool .125".
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- Nov 17, 2017
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I converted my Atlas cross slide and compound from 1/2” x 10 TPI Acme to 1/2” x 20 TPI 60 degree. Then made bigger dials to match with 50 graduations instead of 100. Now the graduations are about 1/8” apart on the dial for .001. Super easy to read for old eyes. It was a fun project and glad I did it.
Mike.
Mike.
I was thinking of a ball screw up date , but looking into it the price had put a pretty solid No on that idea.
The lead screw and so called half nut on my lathe need a redesign.
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- Nov 17, 2017
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Mac
I didn’t read your original post very well. I definitely agree with everyone that you should not change the lead screw pitch. Sorry for any confusion. Plus I’m not sure how a ball screw drive would even work as a lead screw. Best to put it back as originally designed.
Mike
I didn’t read your original post very well. I definitely agree with everyone that you should not change the lead screw pitch. Sorry for any confusion. Plus I’m not sure how a ball screw drive would even work as a lead screw. Best to put it back as originally designed.
Mike
Im just exploring options to fix/upgrade this unit.