OMC Trim Bolt Thread Size ?

[cobrajet390]

I just picked up a used OMC TNT and two of the mounting bolts were snapped off in the unit which needs to be re-drilled and tapped. Does anyone know the thread size used on these bolts (OMC #0332216 7/8" long) ?

 

[cobrajet390]

Re: OMC Trim Bolt Thread Size ?

And the answer is.....3/8-16.

 

[durban]

Re: OMC Trim Bolt Thread Size ?

and the answer is.....3/8-16.

bsw

 

[Tim Frank]

Re: OMC Trim Bolt Thread Size ?

bsw

And the "BS" in BSW stands for....??

If it is a 3/8-16 fastener it is UNC threads series. Use a 3/8-16NC tap to clean up those threads.
Despite what many claim, BSW does not equal UNC....the pitch is usually the same, but the thread form is different.

If you are really stuck, and the security of the joint is not critical, BSW and UNC fasteners will fit-up, but they were not designed to fit, and that kind of re-engineering can be expensive sport.

 

[durban]

Re: OMC Trim Bolt Thread Size ?

And the "BS" in BSW stands for....??

If it is a 3/8-16 fastener it is UNC threads series. Use a 3/8-16NC tap to clean up those threads.
Despite what many claim, BSW does not equal UNC....the pitch is usually the same, but the thread form is different.

If you are really stuck, and the security of the joint is not critical, BSW and UNC fasteners will fit-up, but they were not designed to fit, and that kind of re-engineering can be expensive sport.

britsh standard whitworth, thread angle 55 degrees year 1841
UNC united national course 60 degrees year 1918

 

[Tim Frank]

Re: OMC Trim Bolt Thread Size ?

britsh standard whitworth, thread angle 55 degrees year 1841
UNC united national course 60 degrees year 1918

Thanks for that. There may be a few in here who did not know that.

I am not sure the OP was looking for a history lesson.
He wants to know what tap to use....BSW is simply incorrect.

Nothing wrong with BSW per se, but mixing BSW and UNC thread forms is ill-advised, and in this application it just isn't what should be used.

 

[boobie]

Re: OMC Trim Bolt Thread Size ?

Thanks for the info guys. I completly forgot about the whitworth size threads. Seems today everything is going metric.