Max torque for M4 bolt into 8mm Aluminium - diyAudio
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Old 15th January 2014, 11:44 PM   #1
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Default Max torque for M4 bolt into 8mm Aluminium

I could probably Google this but thought I'd go to the forum

I'm tapping an M4 thread into 8mm thick Aluminium. What would be a sensible torque setting for mounting TO247 devices? Its a Class A amp so max thermal coupling is needed.
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Old 15th January 2014, 11:51 PM   #2
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About half newton meter. Not sure you can get M4 through the transistor.

Last edited by Andrew Eckhardt; 15th January 2014 at 11:56 PM.
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Old 16th January 2014, 12:12 AM   #3
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I suggest you follow the manufacturer's recommended mounting torque for the specific device you are using. The information can be found on the device's data sheet, as the example linked below:

http://www.vishay.com/docs/94391/70tpspbf.pdf

Look for "Mounting torque" on page 3.

If the data sheet of your device does not have that information, look for the manufacturer's publication containing the guidelines for device handling, lead forming and mounting.
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Old 16th January 2014, 12:25 AM   #4
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thanks!

The particular devices are 2SK1530/J201 and do not have mounting info so thanks for the link.

Andrew E: Well spotted! I've taken the standard M3 mounting hole out to M4.

So you think the torque will be governed by the device and not the tap?

Last edited by triplej; 16th January 2014 at 12:29 AM.
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Old 16th January 2014, 12:44 AM   #5
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Quote:
Originally Posted by triplej View Post
So you think the torque will be governed by the device and not the tap?
I do. You can damage most TO-247 devices with less torque than it would take to damage the thread, even if it is tapped in low grade aluminum.
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Old 16th January 2014, 01:27 AM   #6
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Quote:
Originally Posted by grimberg View Post
I do. You can damage most TO-247 devices with less torque than it would take to damage the thread, even if it is tapped in low grade aluminum.
Exactly what I needed to know. Thanks again.
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Old 16th January 2014, 01:33 AM   #7
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Yes, the program has really nothing to do with the title. If you have tools to measure torque that small, believe them.
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Old 16th January 2014, 02:47 AM   #8
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Quote:
Originally Posted by Andrew Eckhardt View Post
Yes, the program has really nothing to do with the title.
Ture, mainly because I thought the tap would be the limiting factor.
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Old 16th January 2014, 03:12 AM   #9
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Only if you break it off in the sink.
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Old 17th January 2014, 06:42 PM   #10
AndrewT is online now AndrewT  Scotland
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Using a clamping bar usually gets a more effective heat transfer.
Then you can use two M3.5, or two M4, or two M5, instead of one offset M3.5
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