I have a mirror mount on my truck door that held a rear view mirror. Unfortunately the mirror decided it didn't want to stay with my truck.
So, I'm looking for a replacement, well actually two since I want the mirrors to match. The mount is drilled and tapped for 1/4"-28 threads. Threads about 3/8" deep and the rest of the mount is hollow. Most of the mirrors I find is 1/4-20. I'm wondering if I can
re-tap the metal over existing threads with a 1/4-20 thread and it will hold...(maybe use some epoxy inside the body of the mount ...........or will I just make a mess of it and make it broke. The drill size for the
two thread sizes are within a 64th or so of being the same and the mount is 7/16" or so wide so I have some meat to play with...










another option... drill completely thru mount and find a mirror with a stud long enough to pass thru completely
and secure with an acorn nut (or something) at the back side of the mount




another caveat... I don't want to remove the mounts from the door... involves removing upholstery and windows and regulators
to get to the internal nuts.

suggestions?

j

 

Are you sure it isn't metric? An M6 x 1.0 would be nearly the same size and is 25 threads per inch.

 

This is what you need John. Only $99 on eBay. This way your mirrors match!

 

That's what I have abe but having second thought now that I didn't build a flat deck..

 

You could drill out the arm and heil-coil to 1/4-20 or cut stud off mirror head and tap and put stud in it.

 

had those west coast mirrors on a 72 ford truck and loved them best rear view I ever had. No blind spots with a spot convex at the bottom
but they just don't add to the ambiance of a '53 as lovely as mine

 

For sure! ....

 

But with that bed you are building you'll need good mirrors to see around it.

 

Bed is narrower than the cab though abe but seeing as I have these I'll likely use them..

 

never installed heli-coils before but understand the principal and it's easy on youtube. The mirror mount is 7/16" wide at the mounting face with a 1/4" hole




a 1/4" helicoil needs a 17/64 hole to tap for the coil.

7/16 = .4375"
17/64 = .2656"

leaving a difference of .1719 or just a fuzz less than 3/16 total
I don't know how to figure the depth of tap thread cut or if it even matters

3/16 = .1875 / 2 = .0937 or 3/32 edge around the hole

I think that will leave enough material to hold the mirror... there's not really a lot of lateral force there.

tell me why I'm wrong

Also the thread depth now is only about 3/16 deep. Do they make a helicoil that short ?? or

feeling around with a piece of tie wire , it doesn't feel like the current inside diameter is much larger than the threaded portion so
the drilling/tapping might give a bite for the coil deeper inside the mount.. keep in mind that I'm doing all this conjecture thru a 1/4"
almost blind hole.

If this is feasible I'll do the drill/tap/insert with red lock tight (after I dry test the hole.

any tips/advice/warnings are encouraged. if I screw this up, it's back three steps or more and replace mounts AND mirrors and
that isn't what I want to happen

thanks
j

 

( if I screw this up, it's back three steps or more and replace mounts AND mirrors and
that isn't what I want to happen )

I thought that was the theme of your build....
couldn't resist John....sorry me bad

 

not a theme John...more like a sword that is continuously hanging there waiting to fall

j

 

Did it fall off while you were driving and if so did the mirror survive ..?

 

searched for it for over an hour... even on both sides of the road. Nowhere to be found , but no telling how far it bounced or traveled off the shoulder...

 

Don't worry, you'll find it in pristine condition after you get new ones..