pick-o-matic metric thread?

I don't know this lathe. But if it has a wheel with 127 teeth, chances are very high. If not, she can't.

HTH, Nick

Dave Check into the Atlas_Craftsman Yahoo group. Very active group,

- - Rex Burkheimer

snipped-for-privacy@aol.com wrote:

This question comes up every so often here. To generate an absolutely correct metric thread [assuming a perfect inch lead screw] a 127-tooth change wheel is indeed required. The problem is this is a large gear [relative to the other change gears] and may not fit.

Because the thread engagement of most lathe parts is only two or three diameters, a thread that is "close enough" is all that is required.

The ideal metric/inch ratio is 127:100 or 1.27000

Other smaller gears can be combined to give very close approximations of the ideal ratio.

For example

80/63 = 1.2698127 or -0.012498% lead

There are of course other combinations.

An additional benefit is that generation of a 127 tooth gear requires differential/compound indexing which is beyond the capabilities of most inexpensive dividing heads, while 47,37,and

Remember if you are using a metric/inch change gear, you *MUST* keep the half nut engaged as the thread indicator does not work with these odd thread fractions. A spindle crank can be a lifesaver if you need to thread to a shoulder.

GmcD

Thanks for the info. I'll try with the 47/37 combination and see if it works with the gears I have. A 127 tooth gear would be too big for the space available anyway. Dave Scott