TheSamba.com :: View topic - How to remove broken dowel pins (crank to flywheel)

Wed Aug 12, 2015 5:19 pm

I got a great deal on a scat 82 stroke crank with all 8 dowels broken off in it.
The end of it is so mangled i can't see exactly where the pins are(were).
The crank is very hard, the pins are harder.

Two days ago I thought of how to remove the pins.
I tried it today and got all 8 out in 40 minutes.

Now, I'll still have to weld up around the holes and re-cut the back of the crank and use 11/32 pins, BUT, that's doable! Done it several times before.

There are a lot of sharp thinkers around here, so I bet somebody can guess how I did it.
Clue: step one was drill a 3/16 hole through each dowel (carbide end mill)

Wed Aug 12, 2015 5:44 pm

Core.
Tap to grab.
Slide hammer on tap.
Out.

I've found some dowels were only hardened on outside. Tapped and threaded a bolt in and out they came.

Wed Aug 12, 2015 5:54 pm

nope. No threads

Wed Aug 12, 2015 5:55 pm

Drill 3/16 hole, tap, thread, then use grease to push them out?
Genius...

Oops! No threads.... Hmmmm..

Wed Aug 12, 2015 5:58 pm

YES! or close enough.
Flooded with heavy gear oil and drove with a short piece of 3/16 drill rod.
A few taps with a hammer, add more oil, few more taps, and out!
Just like a little hydraulic jack!

Wed Aug 12, 2015 6:01 pm

brilliant.

Wed Aug 12, 2015 6:10 pm

Thanks. I wasn't sure if it would work, but it DOES!
I think grease would work well too, but I didn't have a needle attachment to squirt the grease into the tiny hole.

safety goggles and heavy gloves are recommended.

Wed Aug 12, 2015 6:33 pm

Is this something that you are interested in offering as a service. I know someone with a messed up scat 78 that might be interested. Four dowels are broke and four are good but I would take all out for butt grinding.

Ok sickos just tring to describe it.

Dan

Wed Aug 12, 2015 7:04 pm

If it's worth the shipping and 60 an hour, I don't see a reason against it.

But.....I betcha if you explain it to Jose he can do it too!

Wed Aug 12, 2015 8:43 pm

Quote: Now, I'll still have to weld up around the holes and re-cut the back of the crank and use 11/32 pins, BUT, that's doable! Done it several times before.

What kind of filler rod do you use for that sort of thing? :?

Wed Aug 12, 2015 8:46 pm

What do I win?? Hahaha!
I'm such a newb.
Someone here had suggested that method when I was having trouble trying to get my clutch shaft out. It worked like a champ. Amazing.

Think it was Glenn?

Wed Aug 12, 2015 9:39 pm

theKbStockpiler wrote: Quote: Now, I'll still have to weld up around the holes and re-cut the back of the crank and use 11/32 pins, BUT, that's doable! Done it several times before.

What kind of filler rod do you use for that sort of thing? :?

I can't give away all the secrets. I should have said I have an edm machine at work, which is true, but it isn't plugged in, and doesn't work.

It's all in the technique anyhow. But if you really want to know it's the same filler material used in traditional sub arc to build up steel crankshafts. The secret is......... there is no secret.

Wed Aug 12, 2015 10:27 pm

Any body ever try a pin spotter and a slide hammer?
We had one at the shop where I used to work that worked good, we had to grind them off if they were put in the wrong place.

Casey

Thu Aug 13, 2015 4:34 am

modok wrote: YES! or close enough.
Flooded with heavy gear oil and drove with a short piece of 3/16 drill rod.
A few taps with a hammer, add more oil, few more taps, and out!
Just like a little hydraulic jack! What happens as dowel part has moved & contacts the 'driver' dowel, movement stops, its still in crank , no magnet will pull broken part out of crank?? Try to stick a weld to finish? Maybe just lucky but only broken dowels I've run into were 36hp ones, they r easy to break if u don't slowly & evenly remove fwheel.

Thu Aug 13, 2015 5:21 am

I forgot about the 'grease and dowell' trick. Used it years ago to pop bushing out of V6 or 8 crank we were converting. Worked surprisingly well! Got a little messy but it worked.

Thu Aug 13, 2015 9:44 am

earthquake wrote: Any body ever try a pin spotter and a slide hammer?
We had one at the shop where I used to work that worked good, we had to grind them off if they were put in the wrong place.

Casey

I worry that the ground path would weld the pins into the crank. Then you are worse off than when you started..

Thu Aug 13, 2015 5:16 pm

I've never seen a stud welder successfully attach to a large chunk of hardened steel. It could be done somehow, but never seen it.

Thu Aug 13, 2015 5:20 pm

Thanks for sharing, this is ingenious!!!! I wouldn't have thought about it but have done similar for other scenarios. I'll put this in the trick bank

Fri Aug 14, 2015 4:09 pm

What about using the trick used on broken head studs of welding a washer on the flush stud through the hole of the washer placed on top of it and then welding a washer faced nut on top of that? :?

Mon Jun 15, 2020 1:40 am

modok wrote: YES! or close enough.
Flooded with heavy gear oil and drove with a short piece of 3/16 drill rod.
A few taps with a hammer, add more oil, few more taps, and out!
Just like a little hydraulic jack!

so how do you know how deep to drill the hole, given differing dowel pin lengths?