Thread question

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marcofsiny
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Thread question

Post by marcofsiny »

I'm trying to identify the thread size in a gm brake caliper pin. I've asked the manufacturer and they won't tell me. Other manufacturers don't respond and the thread size isn't listed anywhere.
Using digital calipers on the diameter I get inch=.430 (7/16?). On metric I get 10.94 (11mm?).
A "larger" repair pin that taps its own threads in a stripped hole says 7/16-20 on the package. I cannot thread a 7/16-20 die on the pin at all.
So, I'm thinking it is an M11. But I'm not sure of the pitch. Maybe 1.25? Here are 2 pics, one metric one inch
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earlgo
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Re: Thread question

Post by earlgo »

I am inclined to believe that it is a 7/16-20. Your picture shows 6 thread crests 1/4" apart, that means there are 5 spaces in 1/4 inch so 5 x 4 = 20.
None of my books show a M11 thread of any sort but the internet shows:
M11 x 1.5; so the pitch is 1.5mm (or .059" or 16.9 TPI)
M11 x 1.0; so the pitch is 1.0mm (or .03937" or 25.4 TPI)
M11 x .75;
M11 x .5:
None of those fit your picture which shows 11 spaces in 15mm or a pitch of 11/15 = 1.36mm.
Be aware that I am NOT an auto mechanic.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
EOsteam
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Re: Thread question

Post by EOsteam »

I'm betting that it is a thread w/ 1.25 mm thread. On the mm scale the threads line up exactly between 10 mm with 8 threads in that 10 mm. 10 divided by 8 is 1.25
If you have a Metric tap and die set there should be a thread gauge in that set.

Here is a quick search showing an M11 x 1.25 mm tap

https://www.amazon.com/1-25-Metric-Righ ... B0084C5ZOM

Good luck!

Harper
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marcofsiny
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Re: Thread question

Post by marcofsiny »

Thanks for the help guys. Tomorrow I'm going to take the part to a welder to see if he can fill the hole and then drill and tap them. Hopefully he can match the thread up, I wanted to give him as much info as possible. If not I'll let him weld them up and then I will buy a metric gauge and try doing it myself.

Earlgo...I would think 7/16-20 is it also but my die will not even make it up one thread
I dint have a metric t/d set....yet.
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GlennW
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Re: Thread question

Post by GlennW »

try a 7/16-20 nut.

A die can be a bit prickly to get started and it may be a rolled thread.
Glenn

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marcofsiny
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Re: Thread question

Post by marcofsiny »

I've been meaning to take it to home depot and thread it into their thread checking plate. I have had 7/16-20 hardware floating around as I save nuts and bolts,but I moved and got rid of tons of stuff.
The die felt like it wanted to cut new threads, really tough to start.
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Bill Shields
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Re: Thread question

Post by Bill Shields »

What year?

Be careful about welding and then expecting to then drill and tap...unless you have access to a replacement.
Too many things going on to bother listing them.
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marcofsiny
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Re: Thread question

Post by marcofsiny »

It's an 81 pontiac
I was reading that drilling weld and tapping it could be difficult because it heats up fast and then cools down and hardens. Hopefully this will be done at the welders,,they offer a ton of services so I have some faith in them
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Bill Shields
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Re: Thread question

Post by Bill Shields »

Exactly my concern

I would drill it out oversize, rirve a donut into the recess and weld the OD...leaving the ID undisturbed.
Too many things going on to bother listing them.
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marcofsiny
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Re: Thread question

Post by marcofsiny »

I found something called threaded weld washers. If I had a welding machine I would go that route. Looks like the easiest fix, sort of what you mentioned about the donut.
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Bill Shields
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Re: Thread question

Post by Bill Shields »

Or maybe a helicoil could be found..?
Too many things going on to bother listing them.
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liveaboard
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Re: Thread question

Post by liveaboard »

Are other fasteners on the caliper metric or imperialist?

A helicoil would be the best, but finding one for that thread would be a miracle.

So as I understand it, the pin is just the retainer for the pads?
In that case, I would drill oversize, tap with whatever you have, and make a custom pin.
Maybe from a bolt.
Maybe you can get a bolt with the new thread already on it, so you'd only need to turn down the pin section a bit.
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