Oddball Metric Threads

[soupy1957]

I'm a QC Tech for a Communications Equipment Assembly plant here in Connecticut.
Today I had a visit from a Toolmaker, asking me for the tolerance range on an M29 x 1.5 thread.
Wouldn't ya know the Machinists Handbook skips right over the M29's!
I know the "29" represents 29mm Nominal, and the 1.5 represents the threads per revolution, but I can't come up with the tolerance ranges for the Major and Minor threads to save my life!!
Anyone know what the tolerance range is?
-Soupy1957

 

[ScottyUK]

Hi soupy1957,

The 1.5 indicates the pitch of the thread, i.e. the linear distance between adjacent crests. M29 is a damned peculiar thread - not one of the standard ranges.

The following link might help you - I use it as a quick guide when there are no mechies to ask.

http://www.boltscience.com/pages/screw1.htm

The other link has some discussion of standard tolerancing

http://euler9.tripod.com/bolt-database/22.html

It lists

Default metric fastener thread tolerance class. If thread tolerance class designation (e.g., "-6g") is omitted (e.g., M10 x 1.5), it specifies "medium" thread tolerance, which is 6H/6g. The 6H/6g fit is the standard ISO tolerance class for general use.

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