Has anyone else had a problem with James Morehead bellcranks? What size drill bit should I use?

[Lane Gray]

So I'm working on my MonsterBud, and I found the missing 2-hole pullers, but they don't fit on the 5/16" shafts, the holes are SLIGHTLY too small. Obviously reaming out the holes makes more sense than milling the shafts, but does anyone know if I need 8mm or 21/64"

[colin mcintosh]

5/16ths is 8mm.
I would get a round file and remove a bit of metal. It can't need too much removed.

[Lane Gray]

5/16 is a hair shy of 8 (7.95 IIRC), and 21/64 is 8.3

[Bobby D. Jones]

Hi Lane, The size drill bit for a 5/16 shaft (.3125) is an O size letter drill bit. The drill is .316 which gives you ,0035 clearance, On a 5/16 shaft. That is a thin hair thickness of clearance.

There is 3 sets of drills used in USA machine shops, Fractional, Letter and Number drill sets.
MM was not around when Sho-Bud was being built.
If you need any closer fit, An adjustable reamer would be required.

Good Luck on your Sho-Bud rebuild, Happy Steelin.

[Lane Gray]

I put a precision caliper on it. My problem is in the shafts I got from Amazon. They're not 5/16, they're 8mm. That 5 thousandths makes a difference. My father in law has metric bits: we'll just ream out the bellcranks. Seems easier than ordering more. Effing annoying

[Jerry Overstreet]

I've run into this discrepancy with Amazon more than once with metal dimensions.

Recently bought some tubing listed at 5/8 in. o.d. for steel leg inserts. Turns out they were 16mm instead. Pulled my hair out trying to get the clutch parts to work right. Had to return them finally after measuring them. Their ad copy is iffy on dimension.

Also bought some other stainless steel hollow tubing from them earlier with the same discrepancy. Seems everybody is pushing metric dims over SAE these days.

I've found that the Metal Supermarkets, if there's a local store in your area, are the best bet. They will cut and size material to your specs and you can always double check it before you leave. It's a little more expensive but worth the savings in frustration.

Long as your parts fit together that's all that matters but you'll still know they are not factory spec....if that's important.