Another Threading Question

[Tozguy]

I'm working my way through this. The 86/91 tooth gears can be reversed. I knew that but had not accepted them as part of the change gear equation. I roughed out another blank this afternoon and will have another go tomorrow. Worst case I'll take the blank to an experienced friend who offered his machine and expertisee while I sort it out.

From what is shown on p.33 of the manual, the 86/91 gear doesn't need to be flipped at all for metric threads.
The smaller gear (G) on the bottom front of the set up needs to be shifted out to mesh with the 86 gear as John mentioned above.
Isn't it all in understanding the metric gear chart fixed to the front of the lathe?

 

[atunguyd]

If you have a DRO on your lathe or is even easier to test what pitch you are cutting. Engage your half nuts and turn the chuck a few turns to take out any backlash. Now zero your DRO Z axis and then your chuck exactly one turn by hand. The DRO should indicate the carriage travel and hence your thread pitch.

If you are cutting a particularly fine pitch it may be hard to get a decent result as your can't turn the chuck exactly 360 degrees, then try for ten turns and divide the dro amount by 10.

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[epanzella]

According to your chart, you need to mesh the upper 45T to the 91T and the 86T to the lower 60T with the transmission in B6. This gives you the wrong pitch? If you can't mesh that combination you may have to fab something or reverse the lower gear to mesh further out. When I got my 12 x 36 grizzly the first time I tried to cut metric threads I couldn't get the correct combo of gears to mesh up. I ended up making a spacer or two and keep them in the box with the change gears.