Thread cutting and Change gears

This topic has 10 replies, 8 voices, and was last updated 5 January 2016 at 21:01 by Bodger Brian.

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5 January 2016 at 12:59 #219484
Roger Hulett
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@rogerhulett83124
I have a S.B. 9" and I am about to commence some screw thread cutting. I find that some of my change gears are duplicated.I have studied the SB screw cutting chart and there is no indication that I would ever need to use two similar gears at the same time.

My question is….Should I keep the duplicates or should I sell them or should I try to swap them with someone for gears that I do not have (and may well never use) ?????
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5 January 2016 at 12:59 #24304
Roger Hulett
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@rogerhulett83124
5 January 2016 at 13:15 #219485
Ralph H
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@ralphh
Duplicated changewheels do have a use but I am not sure enough how myself. I am sure that someone on here will know.
5 January 2016 at 13:49 #219502
Jon Gibbs
Participant
@jongibbs59756
If they're duplicates of either the smallest or the largest gears then they can be useful for setting up very slow feed rates.

HTH

Jon
5 January 2016 at 14:30 #219508
Martin Connelly
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@martinconnelly55370
They can be used as idlers. Idler gears can be any size but they need to be a size that allows a set-up. If you have pre-owned lathe then there is a possibility you do not have a full set of gears and the duplicates can be used instead of idlers listed on a change gear chart that are missing from what you have.

Martin
5 January 2016 at 14:44 #219511
wheeltapper
Participant
@wheeltapper
Hi

this little program may help you. **LINK**

you input all the gears you have ( including doubles), input your leadscrew pitch and the thread you want to cut and it churns out a list of possible gear setups.

I use it all the time because my lathe has a chart on which some of the setups only work in theory.

Roy.
5 January 2016 at 16:01 #219520
Roger Hulett
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@rogerhulett83124
Thanks everyone. The screwcutting program is excellent.
5 January 2016 at 20:29 #219563
Bodger Brian
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@bodgerbrian
Posted by wheeltapper on 05/01/2016 14:44:05:

Hi

this little program may help you. **LINK**

you input all the gears you have ( including doubles), input your leadscrew pitch and the thread you want to cut and it churns out a list of possible gear setups.

Although the link itself works, there is a link within that page to a diagram of a typical change wheel setup (gear-train.bmp) that appears to be broken. Can anyone point me in the direction of any other link/diagram that shows the same thing?

Brian
5 January 2016 at 20:49 #219568
John Stevenson 1
Participant
@johnstevenson1
How about this one specifically for the Myford ?

**LINK**
5 January 2016 at 20:58 #219570
Speedy Builder5
Participant
@speedybuilder5
Remember, you can't cut all threads using the std gear range and have to sometimes create your own ratios, approximating within 1 tip or so. Especially BA threads !! Keep the gears.
BobH Boxford AUD (similar to the SB 9)
5 January 2016 at 21:01 #219571
Bodger Brian
Participant
@bodgerbrian
Posted by John Stevenson on 05/01/2016 20:49:35:

How about this one specifically for the Myford ?

**LINK**

Thanks John – looks as if that might be what I'm looking for. Presumably the general principle applies to lathes in general & not just Myfords?

Brian
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