Drilling a roll pin

[mhouse]

I dont have any option other then drill out or grind off an old roll pin.
Is a cobolt drill hard enough to make any headway? The one I got from Machine mart does not touch it , I guess its not good enough quality.

 

[vyv_cox]

Roll pins are very hard indeed, heavily rolled and heat treated. I am guessing that the hardness is around 800 Vickers, not far off the same as a metal file and an HSS drill. It would be difficult to drill a file, although the guy who sells drills at various shows seems to manage it. A cobalt one might cope with plenty of lubrication.

 

[savageseadog]

The OP could consider a diamond cutter/grinder.

 

[John the kiwi]

I am confused. (an increasingly common state for me!)
Roll pins are designed to be pushed in and even more importantly pushed through with a pin punch of appropriate size.
Why cant you punch this one through? Has someone screwed up and pushed a roll pin into a blind hole?
Can you attach a photo?
Cheers
John

 

[lw395]

Carbide tool. Dremel?
Alum?

 

[Graham_Wright]

I dont have any option other then drill out or grind off an old roll pin.
Is a cobolt drill hard enough to make any headway? The one I got from Machine mart does not touch it , I guess its not good enough quality.

Grind off? Roll pins normally sit flush both ends.
If there is a centre or you can make one, a carbide tipped drill (masonry drill - not the impact kind) might touch it.

 

[Martin_J]

I'm intrigued as well as to where this roll pin is...

I came across a similar situation on the gearbox selector at the top of a 120SD saildrive... I seem to remember a roll pin installed blind.. I couldn't for the life of me figure out a way of pulling it out..

Then found out that behind it there was a hidden hole that it could be knocked into.. The part it was holding could then be removed and then the roll pin removed from the hole...

Apologies for the thread drift if this is not the case..

 

[tico]

self tapper then pull it out?

 

[Fr J Hackett]

You just might have success by using a small stud extractor to drive into the gap and carefully pull enough of it out to get a better grip on it.

 

[mhouse]

Its been put through the clamp of the flexible coupling into the ss prop shaft and then had 20 off years laying in salt water . Previous owners have been hitting and drilling it. the clamp has been heated as much as possible and soaked with easing oil . Still it wont budge and due to limited space etc I think its angle grinder time through the coupling .. I did wonder if a stud extractor would work but would this expand the pin more and make it harder to get out ?

 

[vyv_cox]

You might like to read down this page to pick up some hints, especially the case history from forumite Old Bilbo. https://coxengineering.sharepoint.com/Pages/Couplings.aspx

I suspect that self tappers and even stud extractors would have little effect on a roll pin due to its hardness.

 

[mhouse]

Thanks . The pic shows it a a volvo coupling with 3 bolts either side , but instead of grub screws its been drilled out for the roll pin.

 

[Trundlebug]

I have a similar set up, and had similar problems although the roll pin in mine sheared into 3 parts which made it difficult to remove.

Ultimately the ONLY way to remove it is by drifting it out with a parallel punch and a HEAVY lump hammer. The heavier the lump hammer the better.
Make sure you support the shaft underneath, so you don't damage the gearbox seal, cutlass bearing, stern gland seal or bend the shaft.

Supporting the shaft close to the pin (but not directly underneath it, obviously) also prevents the shaft springing and absorbing the impact, so will improve the effectiveness of each thump.

From what you've said the pin has already been well soaked in release agent. So all it needs is a good shock to break it free. But you need to be sure it's all aligned so you really are trying to push it out the other side, otherwise you're on a hiding to nothing.

Perseverance and brute force will eventually win, if correctly applied.
Good luck.

 

[Poignard]

Best to use a well fitting stepped punch for driving out roll pins. I turned one up on my lathe from silver steel, then hardened and tempered it but I think you can buy them ready made in sets.

 

[davidej]

The last time I was struggling to separate the shaft from the coupling, I had to resort to hacksawing through the shaft.

When I got the remains out, the shaft was so worn in the cutless and stern gland area, it needed replacing anyway. Thus the days I had spent with a blowlamp, lump hammer, hydraulic press etc were completely wasted.

A new shaft isn't a major expense item - £100 to £200 according to size

 

[alahol2]

OK I'm sticking my neck out and expecting to get it chopped here... What about loosening the clamp, starting the engine and seeing if you can shear it? Assuming the shaft is not keyed.

 

[Iliade]

Perhaps: long series drill small enough to pass through the roll pin. Drill from roll pin through to other side of coupling, then drill from other side to enlarge hole until pin can be drifted out from what is currently the blind side.