Hello Colin,

I take it you are cutting an M5 thread.

Fit the 33 T gear in place of the 24, set the gearbox to 44 tpi and this will produce a pitch of 0.794 mm

Regards

Brian

0.794mm pitch is 31.989924 tpi, might as well just cut it 32 which is 0.79375 and save messing with the change gears

I think you have to judge each case as you get to it. In this instance it is totally practical as there is no difference that most of us could measure and combine that with the fact it is going to have an off the shelf screw which will be a bit slack and the screw is only to hold a part while it is being welded.

Same as you could get away with 20tpi to cut 1.25mm pitch if it is taking a stock nut, the odd 0.02mm over a few turns won't make it lock up, provided that nut is not holding the wings onto your home made aircraft.

Hi there, all,

In discussions of screw-cutting, there is sometimes mention of the percentage error ensuing from the use of some combinations of change-wheels and/or quick-change gear-box, i.e. the percentage difference between the desired or nominal thread and the actual achieved pitch. (Though I notice that none of the posters here have quoted percentage error. )

I wonder whether a usable 'figure of merit' in such matters might be the number of turns required for the error to accumulate to 1 pitch?

Best regards,

Swarf, Mostly!

Then you get the problem that one mans long nut is another's lock nut.

What about the "fit" of the thread will that be based on measuring with wires of just feeding in to depth and if a full form insert is used will that be less likely to bind that using a home ground 60degreeish tool that leaves pointed crests.

As I say so many variables that you can really only judge each job as it comes along.

If we really want to get into the nitty gritty, it is arguable that nuts should have a slightly larger pitch than bolts as nuts get compressed and so shorter when tightened, vice versa bolts. No I'm not going to do the sums, I'll stick to having them the same

Suggest he checks again as 24tpi is standard for all 5C collets not 25.4tpi which is what 1.0mm pitch is.

Luckily they are a bit slack to allow for swarf etc so you got away with it