Clamp screw pitch and diameter?

[mickarch]

I was just attempting to mount up my new to me 1973 50hp Johnson only to realize that the port side clamp screw had been stripped somehow by the previous owner. It was nearly impossible to turn in or out.

So, i finally got it out and need to buy a new one, but I'd also like to clean up the threads in the bracket. Does anyone know the pitch and diameter of the clamp screw so I can by a tap?

thanks,
mick

 

[bigred69]

Re: Clamp screw pitch and diameter?

My guess would be try a machine shop they should have a thread pitch gauge and can tell you what you need.

 

[Joe Reeves]

Re: Clamp screw pitch and diameter?

Purchase the new clampscrew assembly, then visit the tool section of your local hardware or auto parts store. It's simply a matter of matching up the clampscrew threads to the proper tap.

 

[mickarch]

Re: Clamp screw pitch and diameter?

Those both sound like good ideas. I think I have enough of good thread left on the messed up screw to take it in and compare. That way I can work on cleaning up the bracket while I wait on delivery.

thanks for the suggestions.
mick

 

[david_r]

Re: Clamp screw pitch and diameter?

if you dont have enough metal left to rethread ask your auto parts store or screw/fastener store about a helicoil (its an insert slightly larger in diameter than your original hole) its a simple procedure of oversizing the hole and taping for the new helicoil thread.

on an application where you have a certain bolt that has to be used they are very helpfull

 

[mickarch]

Re: Clamp screw pitch and diameter?

For posterity sake, it's a 3/4" 16 pitch thread. I ran the tap through and would say that the remaining threads are marginal. I'll look into the helicoil. Thanks for the suggestion.

mick

 

[david_r]

Re: Clamp screw pitch and diameter?

sometimes you can get them in a kit that comes with the drill bit, tap, helicoil, and the installation tool......but it may be cheaper to buy it in pieces, depending on the size of your tool box.

ive used them on spark plug threads and brake caliper bolt threads and lots of other stuff.