[cncserveng]

Superman you are correct that M20/21 can be used in this way, indeed I recommended this in a previous thread a while ago.

[broby]

You can see here

Metric Fine Thread Data

Be careful with this data... no mention of what class of fit that these specs will achieve.

Most generic metric threads are cut to class 6g/6H, but if you are doing Milspec or Aircraft work, then the class of fit is much higher.

[Green Button]

Here is a good "thumb" rule for metric threads:

Outside thread:

Outer diameter is nominal diameter - 1/10 of pitch
For example: M10x1,5
Outer diameter is 10-(1,5/10)=9,85

Inside thread;
turning(drilling) diameter is nominal diameter-pitch
For example:M12x1,75
hole diameter is 12-1,75=10,25


and for these to we can calculate that height of thread is pitch /2


(all dimension in mm)

[DouglasR]

You could also do this if you are running in inch by using F1.5/25.4.

I see that you are running metric instead of our inch mode, but thought that you'd be interested to know that math can be used in the program virtually anywhere.

So leave the J value at 1 and use whatever is easiest for you for your F value.

One of the reasons to use the math is that the control will calculate out the pitch to a much smaller value (more decimal places) which will give you a more accurate thread. even if you are only off by .00005, it adds up to .001 error after 20 rev's or so.

Best regards,

You are most correct! The OSP is capable of arithmetic calculations on the fly!