new to site so hi for starters & only 4 days experience in cnc thrown in deep end right here we go im trying to cut an internal m10x1 thread firstly do i drill to tapping size? next im using a G92 so need to know how deep for each pass am i right in thinking that the cut lessens with each pass so is there a formula for this? i was going to do 5 passes.hope someone can help as im struggling here

For turning inside threads, the drill, or boring diameter is slightly smaller than for tapping. If the thread is not accurate, drill diameter for tapping works just ok. You can find all the dimensions from ISO thread charts (i didn't find any of the with a quick search on internet, but they exist somewhere.)

Basically, with G92 you decide number and depth of passes like this:

T101 (ID thread)
G97 S2000 M3
G0 X8.8 Z5. M8
G92 Z-15. X9.2 F1.
X9.4
X9.6
X9.8
X9.9
X10.05
G0 X150. Z150. M9

I don't use any formula for calculating chip thickness for each pass, just try carefully and increase depth of passes until it works fine and is fast. Five passes for this thread might be doable, or might break the tool. Depends on material.

I'd prefer G76 over G92, it might take longer but makes tool last much longer, gets better chip control and significally reduces chatter.

I hope this helps you :)

Oh, and welcome to this forum!

Stellram have a nice threading programme on their website which you can download.It`s a bit of a pain to find and download but is very good and easy to use.
Mark.