Repairing a Bench Grinder

[toolmaniac]

Advice needed - bench grinder problem.
I have a Creusen bench grinder which I use for chisel sharpening, etc.
Creusen use a roll pin in a blind hole as a drive key on the wheel flanges. (You would expect better!)
Mine has just sheared off, so I have a roll pin stub in a blind hole.

Any ideas on how to get it out?

I've tried drilling it out, and broken a bit - roll pins are spring steel and very hard.
The hole in the middle is too small for a screw extractor, and anything which grips by expanding from the middle is likely to make it harder to get out.
I'm considering grinding a punch with a chisel point, and trying to cut the sides of the pin from the top downwards.

Anybody got a clever ideas?

 

[powertools]

Is it possible to drill a slighty larger hole in line with the blind hole but from the other side then use a pin punch or even a nail to push the broken pin out.

 

[Hutzul]

How about drilling a new hole, to replace the old hole, and grind the old pin flush. An old allen key can be made to suit as a driver perhaps, or better still a twist drill shank ground to length needed.

Good luck

 

[monkeybiter]

You could try grinding a masonry drill on a green wheel to the right cutting angles and diameter. The tip is tungsten carbide and should manage the roll pin. Maybe even use a slightly undersized bit to remove material from the inner surface of the pin and weaken it sufficiently to remove it without damaging the hole.

 

[graduate_owner]

I haven't tried removing a roll pin, but here are a few possible ideas:-

1. Try tapping a thread into the roll pin, then screw in a bolt and pull the pin out

2. As has been suggested, drill out a hole in the opposite side, as long as this doesn't ruin the flange. You may have to drill a similar hole at the opposite side, to keep things in balance and avoid vibration.

3. Place a metal plate with a hole in it slightly larger that the roll pin. Then weld through the hole so as to weld the pin to the plate. You can then pull on the plate and pin together. This has worked for me when trying to remove a broken jammed bolt.

Whatever you try, let us know how you get on.


K

 

[Cheshirechappie]

Another dodge is to find or make a small punch that closely fits the inside diameter of the roll pin. Then about 3/4 fill the roll-pin hole with oil, push a small plug of cloth in followed by the punch, and give it a smart tap with a hammer. The generated hydraulic pressure on the inside end of the roll pin will push it a little out of the hole. Top up with oil and repeat, until there's enough to get a pair of pliers on.

One possible snag is the split in the roll pin relieving the oil pressure, of course. A piece of rag to cover the job and catch any possible squirts might be prudent.

 

[toolmaniac]

What a lot of great ideas.
Tried the hydraulic method, because it sounded the most interesting. Couldn't get it to work, though.
A 9BA is the right size tap to cut a thread, but the roll pin was too hard.
Masonry drill started well but quickly became blunt.

I decided to drill a new hole. I used a cut-off masonry nail in place of a roll pin, and that had the advantage of filling the flange cut-out better than a roll pin would have done.
You would expect Creusen to either use a better-designed key, or make the flange cut-out the same size as the diameter of the roll pin.

The disadvantage of the extra hole is that it will weaken the shaft. But the advantage is that a broken key can be driven out from either end.
You would think that Creusen might have thought of that, and continued the hole through the shaft.

I would recommend that owners of Creusen grinders remove the roll pin (while they can), and drill all the way through the shaft.
However, it now works well, the wheels are turning and I'm in business again.

So thanks for all the suggestions, and the support.

 

[Eric The Viking]

Personally I wouldn't consider using a roll pin for that. You really need some fairly soft steel - something that will shear if the torque becomes too great - you want to break the pin rather than the machine, or worse, fragment the wheel in use. If it's soft steel, you can drill it out if necessary.

There's a roll pin indexing the handwheel on my Kity table saw. It's a mechanism dreamed up somewhere hot and fiery, and on my list of rework (I'm growing to hate the thing - buy cheap, buy twice, or grumble forever). It's ripped chunks out of the handwheel itself (has to be a loose fit). I haven't got a clever solution yet - stay tuned...

E.

 

[Gary Morris]

Would a diamond drill bit be any good, I had one for drilling tiles, it had a central hole for swarf and lubricant, thei was about 6mm dia, not sure about availability for smaller dia holes, which I'd guess yours is.

Gary