Threadmilling Metric Threads

[AMCNitro]

How do I calculate pitch for metric threads?  Is there a formula?

 

Thank!

[JoshC]

14 minutes ago, AMCNitro said:

How do I calculate pitch for metric threads?  Is there a formula?

 

Thank!

A few people answered this question here, i think GCode showed the forumula

 

14 minutes ago, AMCNitro said:

How do I calculate pitch for metric threads?  Is there a formula?

 

Thank!

And i think what you meant to say is how do you calculate Threads Per inch from a metric pitch. 

alternatively you can just do what i show in the image below and not even have to do any math

[Leon82]

Type in .5mm or whatever the picth iidn the field box

 

Or type 25.4 and divided by the pitch in the field box

[JoshC]

wait a minute, after another read over this question once again it seems as you are not even tapping and are just threadmilling. The pitch of a metric tap is the second number listed. 

M6x1 = 6mm dia, 1mm pitch

M12x1.25 = 12mm dia, 1.25mm pitch

here is a link to a starrett drill tap chart as well https://www.bing.com/images/search?view=detailV2&ccid=0a%2f6m%2bdD&id=D14B3A227CDDCED04134CA19FBA33DB5FD090AD6&thid=OIP.0a_6m-dD_ff9x8lB3toQAQHaLj&mediaurl=http%3a%2f%2fwww.ubbcentral.com%2fstore%2fitem%2fimg-large%2fstarrett-25x39-tap-drill-machinist-wall-chart-poster-decimal-metric-pocket-card_173267621829.jpg&exph=1600&expw=1025&q=starrett+drill+tap+chart+metric&simid=608023165434135280&ck=831D720D03620C0C9445B4C27CADB69D&selectedIndex=0&qft=+filterui%3aimagesize-wallpaper&ajaxhist=0

on a side note heres a handy trick, the pre-drill size  or minor diameter for a metric thread is the pitch minus the major diameter, so lets say your tapping a M6x1, you would predrill to 5mm, or if you were doing a M12x1.25, you would predrill to 10.75mm for an standard 75% thread. if you look at that chart i sent in the link above you can see you simply take the second number or pitch minus the major diameter and that gives you minor diameter of the metric hole AKA the predrill size. just a handy tip for these metric threads.

[Leon82]

13 hours ago, JoshC said:

wait a minute, after another read over this question once again it seems as you are not even tapping and are just threadmilling. The pitch of a metric tap is the second number listed. 

M6x1 = 6mm dia, 1mm pitch

M12x1.25 = 12mm dia, 1.25mm pitch

here is a link to a starrett drill tap chart as well https://www.bing.com/images/search?view=detailV2&ccid=0a%2f6m%2bdD&id=D14B3A227CDDCED04134CA19FBA33DB5FD090AD6&thid=OIP.0a_6m-dD_ff9x8lB3toQAQHaLj&mediaurl=http%3a%2f%2fwww.ubbcentral.com%2fstore%2fitem%2fimg-large%2fstarrett-25x39-tap-drill-machinist-wall-chart-poster-decimal-metric-pocket-card_173267621829.jpg&exph=1600&expw=1025&q=starrett+drill+tap+chart+metric&simid=608023165434135280&ck=831D720D03620C0C9445B4C27CADB69D&selectedIndex=0&qft=+filterui%3aimagesize-wallpaper&ajaxhist=0

on a side note heres a handy trick, the pre-drill size  or minor diameter for a metric thread is the pitch minus the major diameter, so lets say your tapping a M6x1, you would predrill to 5mm, or if you were doing a M12x1.25, you would predrill to 10.75mm for an standard 75% thread. if you look at that chart i sent in the link above you can see you simply take the second number or pitch minus the major diameter and that gives you minor diameter of the metric hole AKA the predrill size. just a handy tip for these metric threads.

It's about the same for inch thread minor diameter also, the drills in the charts are within a few thousanths

[pro grammer]

17 hours ago, JoshC said:

A few people answered this question here, i think GCode showed the forumula

 

And i think what you meant to say is how do you calculate Threads Per inch from a metric pitch. 

alternatively you can just do what i show in the image below and not even have to do any math

That's lathe. Thread milling is generally mill.

17 hours ago, AMCNitro said:

How do I calculate pitch for metric threads?  Is there a formula?

 

Thank!

M8 x 1 pitch is 1/25.4

[zachlancy]

In the TPI dialogue box i'll type for example with an M5 x 0.8 tap...

1/(.8/25.4) and hit enter. It'll calculate it for you and it should now have the converted threads per inch. Just make sure you use the parenthesis. Double check to make sure you did it right until you build confidence in the method. 

[AMCNitro]

20 hours ago, zachlancy said:

In the TPI dialogue box i'll type for example with an M5 x 0.8 tap...

1/(.8/25.4) and hit enter. It'll calculate it for you and it should now have the converted threads per inch. Just make sure you use the parenthesis. Double check to make sure you did it right until you build confidence in the method. 

Ill try that, thanks!  I did find a webpage with all the conversions already done.

Thanks to everyone that helped.

[gcode]

21 hours ago, zachlancy said:

In the TPI dialogue box i'll type for example with an M5 x 0.8 tap...

1/(.8/25.4) and hit enter. It'll calculate it for you and it should now have the converted threads per inch. Just make sure you use the parenthesis. Double check to make sure you did it right until you build confidence in the method. 

 

or type .8mm and let Mastecam do the work

[zachlancy]

33 minutes ago, gcode said:

 

or type .8mm and let Mastecam do the work

But .8 is not TPI...

And if you tick the metric box you have to define all the other parts of the tool in metric.

[JoshC]

Just now, zachlancy said:

But .8 is not TPI...

And if you tick the metric box you have to define all the other parts of the tool in metric.

i think he was just mentioning that your formula of this 1/(.8/25.4) to convert a metric pitch into threads per inch can be simplified with this formula 1/.8mm

since .8mm in mastercam is the same as .8/25.4 

[zachlancy]

9 minutes ago, JoshC said:

i think he was just mentioning that your formula of this 1/(.8/25.4) to convert a metric pitch into threads per inch can be simplified with this formula 1/.8mm

since .8mm in mastercam is the same as .8/25.4 

Fair point didn't know thats what he meant.

You still need to use parenthesis around the .8mm though. At least in MC2020

So 1/(.8mm)

[Leon82]

25.4/.8 

Type that in the box for tpi

That's is one inch divided by the pitch and you will get tpi

[SlaveCam]

There were very extensive thread data charts at Maryland Metrics website but now it seems it has gone under and the material is gone. However some very good soul has put all the charts into one pdf file which seems to be available here https://pdfslide.net/download/link/maryland-metrics-thread-data-charts (includes M and MF charts)