What's your go-to tool for motor shaft thread repair?

[tylerssn]

If you enjoy a good backstory, I bought an old Yerf Dog (3203) the other day. In our hurry to get it going, we didn't secure the shaft bolt on the motor quite well enough, so it came lose and the last few threads holding it in stripped.

Forcing it back in, I'm sure didn't help. I'm replacing the driver and the bolt and would like to re-thread the shaft.

The shaft I'm needing to repair is 5/16-24 on a Predator 212cc.

 

[panchothedog]

Try running that very same tap back in there. Then make sure the new bolt is as long as possible without bottoming out. Even if you have to cut one that's too long down a little. You need as much thread grabbing as possible. This same procedure has worked for me. Messed it up the same way you did. Came out under heavy throttle and I thought it was ruined.

 

[Master Hack]

Are you using a plug tap or taper?
ok re read that…
ya need a plug tap.

 

[panchothedog]

I honestly think it was a tapered tap. Just an ordinary 5/16 x 24 tap. Seems like it was a little narrower at the very end.

 

[Master Hack]

A plug tap is for threading all the way to the bottom of a blind hole.
Taper is for through holes. The taper mahes it easy to start straight.

iffin….
the threads are too honked up to hold securly, yer still not up a creek.
5/16 happens to be the drill size for a 3/8 x 24 threaded hole.
run a 5/16 drill doen the crankshaft. The shaft is not hardened there.
that sets ya up to rethread it bigger. Use a plug tap, cutting oil and go slow.
know yer depth, maybe practice on a piece of scrap. Ya only get one chance, force it, break a tap and yer up a creek and yer paddle just broke.

 

[Master Hack]

Just when ya started being sorry ya asked....
Here is some more tap porn for ya. Or as we often say screw....ahh nevermind.
Or if ya just have trouble sleeping this is sure to cure THAT problem!
If ya stay awake long enough you will see the correct info regarding bottom cutting taps, instead of the wrong gobbledegook i said earlier.
This is based on CNC applications but basically the same BS.

Taps and Applications | Redline Tools

Taps and their applications for CNC machines and lathes. All RedLine tools are made in the USA.

www.redlinetools.com

 

[panchothedog]

Hack, the threads on my crank shaft ( and I also think for tylerssn ) were the threads at the beginning or end of the crank. Not at the bottom. As the bolt comes out, right before it is thrown, it is wobbling real bad and tears up the last few threads. That is why an ordinary tap worked for me, and I think it might work for him as well.

 

[Master Hack]

Hack, the threads on my crank shaft ( and I also think for tylerssn ) were the threads at the beginning or end of the crank. Not at the bottom. As the bolt comes out, right before it is thrown, it is wobbling real bad and tears up the last few threads. That is why an ordinary tap worked for me, and I think it might work for him as well.

Yeah, i get that. I guess i wasn’t very clear.
i shoulda said:
if yer gunna rethread a blind hole, you should use a plug tap or other bottom Cutting tap. That will insure that the threads all the way to the bottom are clean.
Debris can collect at the bottom of a blind hole and if there was a thread failure could be chips in there. If there has been trouble such as described ya want a clean restart. If yer rethreading to a bigger size use a plug.
thats what i was tring to get at.
any tap will do the job, some better than others.

its not difficult to find plug taps. The. Hanson brand sold at our local Ace are plug taps. You probably have a few without knowing it.

in addition it feels good to unload some of the useless info stuck between my ears. So thank you for allowing me another “brain dump”

 

[rockman96]

Actually, a plug tap is in between a taper tap and a bottom tap... A bottom tap would work best for a blind hole, that way you can get the threads as deep as possible. Just make sure to remove the tap multiple times and blow out the hole to keep it clean.

 

[Master Hack]

Actually, a plug tap is in between a taper tap and a bottom tap... A bottom tap would work best for a blind hole, that way you can get the threads as deep as possible. Just make sure to remove the tap multiple times and blow out the hole to keep it clean

That is correct! I knew this stuff much mo bedder years ago, before the brain started getting soft. Then l retired, now l just think 'bout whiskey and wimmen.
so l often get things backwards.

Ya won't find a bottom cutting tap at ace or HD. So that leaves ya with on line stuff unless ya can find machinery dealer kinda place.