Where to get 127 tooth change gear for SB 9?

No idea where you can get such a gear. You could try to make one.

That's the hard and expensive way.

The smart way is to use a 63 tooth gear which is much cheaper to get, I believe.

I worked out the arithmetic for use of such a gear some years ago and, while the conversion is not exact, it is so close that the inaccuracy would get lost in the accumulated tolerances of the lead screw and gear train.

If you are interested in pursuing this let me know and I will dig out my scribbles.

Wolfgang

The inaccuracy is only 1 part in 127, but it is all in one direction. If you are threading a long part it could be a problem.

I bought change gears from Scott Logan for my 10EE and modified to fit. I'm sure you can do the same. I used a smaller gear set that is only off .02% but he has the 127 also if that's what you want.

Loganact.com I think

Karl

Union Gear and Boston Gear both list 127T 16DP change gears. Ametric shows 127T metric spur gears in modules 1, 1.5, 2, 2.5, and 3.

The error is MUCH smaller than 1 in 127, provided the proper gear train is set up. There is more to it than a straight substitution plus 1 to 2 ratio.

As I said, if there is interest I will dig out my calcs.

Wolfgang

47:37 Gerry :-)} London, Canada

Check out this Australian dealer's site, under "Hercus lathe parts" near bottom of page. Hercus9 is close copy of SB9, pretty sure gears will fit.

the hercus is actually an exact clone of the southbend.

try the hercus website as well. the guys who now run hercus engineering have nearly all the hercus spares. steve will respond to an email query.

hercus btw are gear makers and light engineering now so making a gear shouldnt be a problem.

Stealth Pilot

snipped-for-privacy@sympatico.ca wrote in article ...

I just read an article in one of the metalworking magazines I receive (Home Shop Machinist - November/December 2007) that shows the use of a 32DP

127-tooth gear that drives another 32DP gear. On the same shaft as the driven gear is a standard 16DP gear that allows the rest of the gear train to be setup with the lathe's usual 16DP gears.

This allows for a smaller diameter, 32DP, 127-tooth gear to be used where a

16DP, 127-tooth gear might not fit well.

These should work just fine. I bought a used one for a Boxford and it worked.

-- - - - - - - - - - - - - - - - - Bill Graves RKBA! snipped-for-privacy@ix.netcom.com

This is exactly the setup I have for a generic 7x10 - using the Sherline

127 and 50 tooth gears; the 7x10 gears have a different pitch, but keying each of the Sherline gears to one of the 7x10 gears eliminates this problem.

The Sherline gears were

a) available; and b) relatively cheap.

33/13 = 2.5385, -0.06% error 127/50 = 2.5400, 0% error 94/37 = 2.5405, 0.02% error 61/24 = 2.5417, 0.07% error

My Smithy, which is a brand that is world-renowned for quality* uses the

33/13 trick, and does OK.

0.06% error would require 1666 threads to be off by one; if being off by

1/20th a thread makes you bind up that's still 83 threads, or over four inches for a 1/4-20 screw.

• I didn't say _good_ quality!