Motor mounts threads

I have new rubber mounts for the motor and the 1/2-18 threads are very tight. A new 1/2 inch bolt will only thread in about a 1/4 to 1/2 a turn. Is this normal?
Is it some form of thread lock?

I suspect you have got metric ones which are 12mm.

The usuals sometimes supply generic rubber mounts.

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Thanks for the thought. I will give it a try.

Jim Pomeroy
506 850 0671

I have both SAE and metric thread gauges to help me sort out things like this. Some of my Jaguars have both SAE and metric fasteners so it is important to know which is which quickly and easily to avoid expensive mistakes.

These come in tap and die sets but they are also sold separately.


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Thanks Paul. I too have thread guages. This is the first time I’ve seen a Metric fastener in either the car or engine.

Jim Pomeroy
506 850 0671

My money’s on M12 x1.5 which is about 17tpi.

So close enough to the naked eye.

To be honest, if they send you a metric mount they usually provide the bolt too.

As an aside, I usually use the “uprated” mounts from SNGB.

Some of the el cheapo ones collapse pretty quickly; these seem not to. If you look at the detail on the bolt it has 8.8 on it. That’s a metric tensile grade number.

Thanks Andrew. Parts from SNGB came with no matching bolt.
I will try a 12mm today.

Somewhere in the archives, I provided a link to the industrial mount that these are: I got them for my Jag for about five dollars, each.

Well, I got out to the garage to check this morning. I don’t believe they’re 12mm as the bolt will go in but is very, very sloppy. Certainly not what I would be comfortable for an engine mount.
I will reach out to Barratts to see their thoughts to day.

1/2" UNF is 20 TPI, not 18. Where did you get the 18 figure from?

Sorry. Brain fart. I checked with a thread gauge and they are 20.

Threads not metric. Just badly cut 1/2 UNF. Ran a tap through and all OK.

Bang on Wiggie. The ones with the metal cap carry on for years, don’t crush, and the metal implant for the bolt doesn’t pull out of the mount on the left side from the torque. (If you drive it like you should!) .