Thread: Roll pin removal problem

Problem: To remove a 6mm roll pin (straight split type) that has broken below a surface.
It's in a blind hole with no access from the rear.

I tried drilling it with a HSS, then a HSS/cobalt drill bit, with no impression made.
The pin is evidently made of hard stuff.

Some solid carbide bits are next to try.

Any suggestions otherwise?

How far below the surface?

Silly idea 1: spot weld a small bolt to it and use a slide hammer to draw it out.
Silly idea 2: Would a small 'ezy out' grip the inside of the roll pin?
Any space under the pin or is it against the blind hole?
Silly idea 3: make a hook to get behind the pin to slide hammer it out?

I'm out.....

I'd say go with the carbide drill, no need to go the full diameter, just make it thin enough to let it collapse

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If the centre of the pin is still visible, try inserting some squashed timber slivers lengthways into the hole, try and pack it tight if possible, try to get them flush or just below the surface.

Take your drill and grind negative rake on the cutting edges as if you were drilling brass or cast, run drill at low speed with reasonable pressure, hopefully you are able to use a drill press, if not you may have to rig up some type of lever system to apply a constant load.

A carbide drill bit might snap due to the interrupted cut caused by the split in the roll pin. Pipeclay's method might prevent that. Do you have a long thin carbide burr?

Interesting design that uses a roll pin with no ability to drive it out again.

Originally Posted by Sterob

...
Silly idea 2: Would a small 'ezy out' grip the inside of the roll pin?

Silly idea 3: make a ____ to slide hammer it out?

Ezy out probably would not work as the screwing action would push the pin further out.

However, combining 2 and 3 may be worth a try - a screw (like a self tapper) in the pin and then using a slide hammer to remove could be worth while. Once a reasonable amount of pin was showing, a pair of locking pliers could be used to compress the pin, making it easier to remove.

Michael

What about fill it with grease and drive a pin punch down the centre to hydraulic it out ?

Just read the comments, and I would take on pipeclays advice, as in my opinion he is a highly respected machinist on this page.

Just a thought, what about trying to gently put a good quality tap inside it of the right size, a few threads would be all that's needed.
Then use a bolt, plate and spacer to Jack it out like a taper pin.

You could even use the tap as the jacking bolt once it grabs, then depending on the surface you could get some vice grips on it and a steel or aluminium block under it for leverage a few mm at a time?

If it starts spinning with the tap engagement all the better.


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Originally Posted by droog

What about fill it with grease and drive a pin punch down the centre to hydraulic it out ?

There is a slot up one side, so the grease would escape.
Done plenty of flywheel spigot bushing like you describe in my earlier years.

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I suspect that only a carbide tap would be hard enough to cut a roll pin. And I reckon an Ezi-Out would just expand the roll pin in the hole, jamming it even tighter. Can't hurt to try though.

Some good comments, thanks folks.

I think the roll pin is not what is supposed to be there, which is the coupling/drive between a sprocket and camshaft.
It's likely the original piece was lost, so the roll pin was used by someone in place of a solid pin.

There may just be some space between the end of the roll pin and the bottom of the hole, worth checking to see if I can fish it out that way.

I don't understand the idea of packing the pin with timber. What's the theory there, please?

The pin is quite hard, and even with lots of pressure at low speed, it won't be cut with a cobalt HSS bit.
I did try to tap it, no progress at all.

I can't tell you the theory, only that I was shown the method over 40 yrs ago when removing broken bolts from dies, it worked.
Have also used the same method for drilling concrete when you hit reo.
The wood may provide a bit of resistance to stop the drill wanting to bite, same as the slight negative rake on the drill.

Hi Jordan, Guys,

Would it be possible to drill down the centre of the pin and right through ! That would give you a starting point to drill from the other side and get a pin punch in there, particularly if the exit hole was a fraction larger.

Originally Posted by pipeclay

The wood may provide a bit of resistance to stop the drill wanting to bite, same as the slight negative rake on the drill.

Thanks Pipeclay, that seems right. But I wish the drill bit would want to bite.

Originally Posted by BaronJ

Hi Jordan, Guys,

Would it be possible to drill down the centre of the pin and right through

It would have to be a long hole, from the back end of a 4 cylinder engine camshaft - not practical, but thanks for the suggestion!

I thought of a possible alternative solution - drill another hole through both the sprocket and the camshaft end.
If the carbide drill breaks I may have to do that.