Thread: Metric Tap Speeds & Feeds

I'm an idiot. Thanks. This is my first job that I have had to use metric and although it is proving to be much easier and is quite an adjustment.

A tip for anyone using metric taps but programing using inch units. Use rpm's that are multiples of 254 For the above tap, 254rpm = 15ipm for rigid tapping. No rounding problems that way.

hi there my name is didier and am busy also with my first tapping on a vertical machining centre. how did you work out the correct speed for the recommended feed?

Consider a 1.0mm pitch tap

25.4 mm per inch so 25.4x10 RPM = 1.0mmx10 IPM feed
254 RPM and 10 IPM

For a 0.75mm pitch tap
254 RPM = 7.5 IPM feed Which is fine, most controllers handle .x or even .xx feeds. Or just double both to 508 RPM and 15 IPM

for a 1.25mm pitch tap
254 RPM = 12.5 Same as above.


ect.

Crashmaster - If you are tapping metric thread I would think that the print is in metric. So why not bite the bullet and program in metric?
First job may be difficult at first but for other metric jobs you will be saving yourselves a lot of trouble. The worst thing you can do is keep converting. Believe me! You will screw up big time.

Wow, talk about reviving an old thread. Juergenwt; I will program a part in metric if that is what the print calls for. This part was the first time I had to actually tap something with a metric tap and wasn't quite sure how the feeds and speeds for a metric tap needed to be computed. After running this part and several like it, I actually prefer programming in metric now.

I gotta use a M12x1.75 but I use a feed of ~ 10.0 and and speed of ...???
Example, 1/2-13 I program f10.0 and a speed of S130 ....
So with my metric I'm lost...

RPM 254 = 17.5 ipm. If you wanted a faster rpm just make sure you increase your feed proportionately. So if you doubled you RPM to 508 just make sure you double your feed too; 35 ipm. Does that make sense?

need to change metric to inches

M8X1.25 TAP

( mm X .03937) = inches.

1.25 mm x.03937= .0492125
then 800 rpm X .0492125 = F39.37.

here's a neat iphone app that will calculate feeds and speeds for both metric and inch taps and lots more... Machinist Calculator SFM by ApplicationSoft
https://appsto.re/us/Jeusw.i

I like this one better, and it's cheaper.
https://itunes.apple.com/us/app/job-...486151960?mt=8
Plus I'm the developer so if anybody sees a need for something to be added, let me know.