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making sense out of metric machine screw (bolts) specifications?

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Forum topic by JesseTutt posted 09-21-2012 04:32 PM 1891 views 0 times favorited 8 replies Add to Favorites Watch
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JesseTutt

811 posts in 863 days


09-21-2012 04:32 PM

Topic tags/keywords: question machine screw bolt metric

I understand the notation for machine screws used in the United States. A 6-32×1 would be a #6 diameter, 32 threads per inch, and 1” long.

How do I interpretate metric machine screws?

What would “Cap Screw M6-1×20” mean? Another example is “Carriage Bolt M8-1.25×85”.

-- Jesse, Saint Louis, Missouri


8 replies so far

View Loren's profile

Loren

7826 posts in 2400 days


#1 posted 09-21-2012 04:49 PM

The M number is the diameter of the shank in mm. The middle
number is some sort of pitch designation I think. For an M6 it’s
usually 1 and for M8 it’s higher and for M5 it’s lower. The final
number is the length in mm.

-- http://lawoodworking.com

View ChrisK's profile

ChrisK

1287 posts in 1834 days


#2 posted 09-21-2012 04:52 PM

M6 -1×20

M6 – 6 mm dia thread, 1mm thread pitch 20 mm long.

Head styles names are the same as US standard

Check McMaster-Carr’s web site for all of the dimensions for each head style

-- Chris K

View JesseTutt's profile

JesseTutt

811 posts in 863 days


#3 posted 09-21-2012 05:07 PM

does thread pitch map into something simular to threads per inch? Threads per cm?

-- Jesse, Saint Louis, Missouri

View Loren's profile

Loren

7826 posts in 2400 days


#4 posted 09-21-2012 05:11 PM

My best guess is it’s the mm length on a complete thread.
Thus m6-1×20 would have 20 threads because the ratio
is 1. M8 is commonly 1.25 so in that case you’d need
a 25mm shank to have 20 threads.

-- http://lawoodworking.com

View crank49's profile

crank49

3524 posts in 1723 days


#5 posted 09-21-2012 05:13 PM

In the above example:
M6 – 1 X 20

6mm dia. – 1mm pitch (means one thread per mm) x 20 mm long

-- Michael :-{| “If you tell a big enough lie and tell it frequently enough, it will be believed.” ― A H

View Rex B's profile

Rex B

314 posts in 1003 days


#6 posted 09-21-2012 05:56 PM

crank49 is correct, 1mm thread pitch means that the distance from the peak of one thread to the next peak is 1mm. Likewise the distance from one valley to the next is also 1mm. See here.

-- Rex

View JesseTutt's profile

JesseTutt

811 posts in 863 days


#7 posted 09-21-2012 06:44 PM

Thanks all, that was what I wanted to know

-- Jesse, Saint Louis, Missouri

View Bill White's profile

Bill White

3589 posts in 2713 days


#8 posted 09-21-2012 06:46 PM

Want me to REALLY start an issue?
I wish we would all go metric since we have to own multiple tools to achieve the same results. I even had some “Whitworth” stuff from the motorcycle repair days.
Blast away if ya will, and I’m not tryin’ to hijack.
Bill

-- bill@magraphics.us

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