Drilling PTO for clutch

Hambone

Hambone

Member
#1
#1
Have any of you gentleman been down the road of drilling a PTO for a clutch? My little H35 has a 5/8” OD PTO, that is not drilled and tapped for a bolt. Any idea what the right size ID drill bushing that needs to be used?
 
minibikin'

minibikin'

Sho-nuff
#4
#4
RobertC said:
I am glad you've asked this, as I'm looking at similar scenario.

I know there's some threads around here about it, but I haven't searched around much for it yet.

I'll look later today, and post it here.

Edit: Here's one post that describes it...I'm looking for a guide piece to assist:

https://www.oldminibikes.com/forum/...s-getting-fewer-and-fewer.152430/post-1156164

Searching on the string "drill and tap"
Click to expand...
@RobertC I have the tools/guides for the 3/4 and 5/8 crankshaft. You are welcome to use them if you'd like. PM me and I'll ship them to you. Just return them when finished please...
 
RobertC

RobertC

#5
#5
Hey Chad @minibikin' ...Thank you for the offer.

And @Skipp too. I'm going to see if mcmaster carr has a 5/8 od drill bushing like the 3/4 od that cfh was referring to.

If that doesn't work out, I may take one of y'all up on it.

Any way y'all could post a pic of the ones y'all use ?

Thanks !
 
DaddyJohn

DaddyJohn

Well-Known Member
#6
#6
The last few I've done, I just center-marked the PTO output shaft, then center-punched the mark. Once you've got this done. you can set the engine on the drill press recoil side down, as this provides a nice, level base to drill against and holds the crank in a vertical position for drilling. You also can work on the floor (if you don't have a press) and hand drill if you feel confident in your ability to drill straight. Anyway, I use a size "F" drill, which is the tap size for 5/16-18.

Follow that with hand-tapping the hole, which is sometimes made easier by placing a rag over the PTO and grabbing it with some vice-grips to keep it from turning while you twist the tap into it.

Alternatively, I suppose you could tap to 5/16-24 using an I-drill, though I haven't had an issue with the coarser 18-pitch thread.
 
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DaddyJohn

DaddyJohn

Well-Known Member
#8
#8
F drill (tap drill for 18 pitch) is .257
I drill (tap drill for 24 pitch ) is .272

That means the 18 pitch thread’s minor diameter would be oversized a bit.
At any rate, some blue thread locker and not getting crazy over tightening the bolt should make stripping it a non-issue! :)
 
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