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Chris Miller
Grand Master
Username: cjm51213

Post Number: 321
Registered: 5-2013
Posted on Tuesday, 30 December, 2014 - 03:48 am:   Edit PostDelete PostView Post/Check IP

Hi Folks,

The door trim hardware is attached with tiny slotted, fillister head machine screws. I am sure they are 36 TPI, and I am equally sure that they are smaller gauge then #8 and larger gauge then #6. If #7 ever existed, and I doubt that it did, it no longer exists. Does anybody know the designation of these screws? I have at least one mounting plate where I need to clean-up the threads. I could re-fit #8 everywhere, but that seems like a lot of unnecessary work, if I can get these and find a tap of the correct size.

Thanks for the help,

Chris.
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Jeff Young
Prolific User
Username: jeyjey

Post Number: 212
Registered: 10-2010
Posted on Tuesday, 30 December, 2014 - 03:58 am:   Edit PostDelete PostView Post/Check IP

Hi Chris,

I would have thought they'd be 2BA (which is 31.4 TPI and between a #8 and a #10).

Perhaps 4BA? (38.5 TPI and just a hair larger than a #6.)

But whatever it is, it will be a BA thread-form.

Cheers,
Jeff.
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Chris Miller
Grand Master
Username: cjm51213

Post Number: 322
Registered: 5-2013
Posted on Tuesday, 30 December, 2014 - 05:44 am:   Edit PostDelete PostView Post/Check IP

Hi Jeff,

You're probably right. I don't have a lot of threads to match and so I was not be able to discriminate between 31.4 and 36 or between 38.5 and 36 over the course of four or five threads that I could match. Given what I believe I do know, I'm going to predict 4BA, which is conveniently available in the correct length from Oz: http://www.classicfasteners.com.au/machine-screws/. 3BA is right there within a few thousandths of #8, and I know #8 to be too large a gauge. Also, 4ba appears to be the only candidate size available in 5/16" length, which is a number that I believe I know reliably.

These things appear to be completely unavailable in the US, so I'm going international! $20 (AUD) out the door, for 50 screws sounds like a pretty good deal to me, and probably enough to last a while, if I don't drop too many.

Thanks for the help,

Chris.
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Bob UK
Unregistered guest
Posted From: 94.197.122.79
Posted on Wednesday, 31 December, 2014 - 04:50 am:   Edit PostDelete PostView Post/Check IP

British Association that is BA threads are 47.5 degrees.
Find Engineers Screw thread tables on the web. Look for British Standards logo. ZEUS is the one I use.

Also machine screw can mean different things in different territories. I have heard grub screws called machine screws.

I think these are 3 BA.

BA was invented for electrical engineering.

Note cadmium plated anything is now expensive so little screws like this are Zinc plated they are fine to use but a smear of petroleum jelly stops chemical reactions between zinc and the die cast bit. Non trim applications, ie not in the car normal grease. For electrical connections always use brass but do not overtighten because they shear easy. Petroleum jelly for protection.

(Message approved by david_gore)

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