Screw cutting dials

[BRIAN]

Heving just lately converted my 7 x to belt drive and not yet got the motor to reverse. I was forced into using the dial
for the first time. to cut a 8mm thread with the metric lead screw already in I only need to put the correct dial on ( the one with 12 divisions ) and i am away Thinks I ,Just use No 1 ( to mutch in a rush to find the chart??? )
First pass OK second pass Oh me Gawd.! wiped out all my good work.

So look at the chart FOOL.

Now the metric dial that came with the lathe has 16 teeth

The chart says use a dial with 15 teeth for this thread. also there is a dial with 14 teeth for other threads

Look up the spares Only 16 teeth dials available for this lathe??

SO after a lot of extra work I made a cutter and then made the gear. and now i can cut 8mm threads OK

But i wonder? I have seen other threads from people having thread cutting problems .Can this be one of the causes.

Food for thought??



Regards BRIAN.

 

[British Steel]

Hi Brian,

Almost certainly the cause of a lot of screw-cutting problems - as your chart says, there should be 14, 15 and 16 tooth gears but only the 16 is supplied - it's even worse on some of the Imperial machines, a 12tpi leadscrew is fitted and a 16 or 32-tooth gear... So, I can cut lots of multipes of 1&1/3 tpi threads, what were they again? [1]

The manufacturers in China have finally got their head around how the dials work, and they're supplying the Imperial lathes with 24-tooth gear for the thread dial indicator now, so any multiple of 1/2 tpi can be cut! Looking at your thread chart, I guess your leadscrew is 1.5mm pitch?

Doesn't mean they come with the required change-gears though - some TPI threads may need gears form the metric set!

Dave H. (the other one)

[1] - so 4, 8, 12, 16 etc. work OK picking up on the same number - and 2&2/3, 5&1/3, 6&2/3 TPI etc... Aargh! What happened to 10, 11, 13, 14, 15 and 18 etc.? Damn glad I have a QCGB and a proper dial!