Trouble with motor mount screws

[MikeConyers]

Just getting back into RC boats after 15+ hiatus. So pretty much learning all over again. I have two brand new motors but I'm having trouble mounting them. Using 6/32 screws which fit perfectly into my motor mounts but won't budge in the non tapped holes of the motors.

Also, 4/40 screws are too small.

Should I use 6/32 tap on the holes?

Thought about using a 1/8 drill bit to open the hole, but didn't know if that would make it too large.

I understand that I could turn down the OD on the screws but not exactly familiar with how to do that w/o a lathe.

Just looking for some advice! Thx!

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[Ray Sametz]

Just drill out the case holes to clear the 6/32 machine screws. Cover every opening on the engine to prevent filings from getting in. I've never seen case hole taped to match mount.

 

[PaulHail]

Don't turn down the threads on a bolt or screw, it will pull out the threads of the mount and damage the mount.

Don't tap the holes in the engine. It will be almost impossible to properly clock the threads so that they will line up with the mount and you won't be able to tighten the engine against the mount. Worse yet you run the risk of damaging the engine.

The major diameter on a 6-32 thread is 0.138", and per machinery handbook you'll want a 0.154" or #23 drill for the clearance hole in the engine mounting tab.

 

[MikeConyers]

Don't turn down the threads on a bolt or screw, it will pull out the threads of the mount and damage the mount.

Don't tap the holes in the engine. It will be almost impossible to properly clock the threads so that they will line up with the mount and you won't be able to tighten the engine against the mount. Worse yet you run the risk of damaging the engine.

The major diameter on a 6-32 thread is 0.138", and per machinery handbook you'll want a 0.154" or #23 drill for the clearance hole in the engine mounting tab.

Thanks Guys! I figured I was making it a lot harder than it needed to be...

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[moparbarn]

The mount holes in the CMB's are a metric/mm size. No matchee round eye sizes (-:

 

[Mike Betke]

Stock holes in that 21 should be clearanced for 4-40. That's what I use on mine. I put a flat washer on the screw to keep it from digging into the case.

 

[Alan Elzer]

Mike

Your black 67 motor is discontinued on parts, but I have what's left from the CMB dealer.

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