I am going to mount an air shock absorber pressure gauge on a 2006 Ultra. While looking for places to put the gauge mounting bracket I would make I came across an existing untapped hole that looks like it will accommodate a 1/2" tap. The location is on the right side of the cycle on the metal plate at the frame V just rearward of the outside of the rear cylinder. There are two holes in this area, one larger (about 1" dia.) toward the centerline of the cycle. It is the other one (closest to the outside) which I'm thinking of tapping.

So, since this metal plate is fairly thin, perhaps 1/8" at most, is it better to use a coarse thread tap (13 tpi) or a finer thread tap (20 tpi)? Once I get the hole tapped I would use a hex head bolt with blue loctite.

Any other mounting suggestions? Should I use a rubber washer at the mounting location (the hole I have been talking about) for a glycerin-filled air gauge. Or, should I just mount it solid to the metal plate? I have been trying not only to find a suitable existing hole to use but also to find it in a location that wouldn't interfere with my riding position. I do not need to see this gauge all the time, of course.

Thanks for any assistance or advice offered.

 

You will need a hole smaller than .500 to thread .500 i can give you the drill size for a .500-fine thread if you need it . The fine thread is better in the thin metal as you will get more threads per inch. But i would look for a different attaching method myself

 

how thin are we talking about?
Is it possible to use a bolt, washer, and nut?

dd

 

A good thing to remember is, the finer thread isn't as deep as a course thread.

 

1/2 -13 (coarse) Tap drill size is 27/64" (.422) @ 75% Thread. 1/2-20 (fine) Tap drill size is 29/64"(.453) @75% Thread.

 

I have a gauge bracket mounted behind the right saddle bag, there is room to mount there see picture. The gauges show air pressure for front & rear shocks.

 

Bolt it, too thin to expect a tapped hole will last.

 

Tapping the hole in the frame is going to remove the powder coating in the hole. Just sayin.

 

A fine pitch thread will should be ok.

 

Well thank all you responders. I am going to try and bolt/nut the bracket first. To do this I will have to cut off an end wrench real short, then weld up a bendable handle that I can fish through the larger of the two holes. Maybe I'll just use a thick welding rod for the handle. Then, with a nylon lock nut I should be able to use the air ratchet and get it quite tight. With only two hands the air ratchet comes in real handy.

Thanks again.