Stubborn locking screw

If you cannot drill it out, I’d soak it overnight in some penetrating oil, giving it an occasional tap to loosen or break any seal or adhesion that has formed.
Assuming that it is a roll pin, it should just be held in place by its own friction so you may be able to pull it out with a blind bearing puller. A cheaper way of trying that is to use an expansion bolt cut and filed to size, tightened in to place in the hole and tapped upwards to pull the pin out. A spanner under the bolt head can give you a bigger target to tap, pulling away from the hole.
 
If that is a roll pin try drilling from the other side .Then you can push the pin out with a suitable rod.Use cobalt drills, plenty of cutting fluid and keep the pressure on to avoid work hardening the stainless.
 
Rigger Mortice said:
I'm confused.
If the clamp doesn't split in half what are the allen bolts doing?
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The split is so the coupling tightens down and grips the shaft - the four socket head cap screws deform the coupling to reduce the hole size. The roll pin might be a later addition, sometimes done if the coupling has slipped on the shaft. If that is the case there probably won't be a key or keyway.

edit- as Alahol says above
 
alahol2 said:
It's similar to this one. The coupling is split but not completely. The allen bolts clamp the two 'halves' to the shaft.
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Ah, I see. Thanks.
Technically that is known as a bit of a b u g g e r. :rolleyes:

Drill from the opposite side I reckon. Then a drift to push the pin out. If is is cast iron it won't be hard. If it's S/S it will be a bit of a .........
 
If it's a roll pin of some sort, what about gently screwing in a self-tapping screw and then trying to pull and / or tap it out? Perhaps tap it in a little first to release it? Dumb and dirty maybe but easy and not much to lose if it doesn't work.
 
alahol2 said:
It's similar to this one. The coupling is split but not completely. The allen bolts clamp the two 'halves' to the shaft.
Click to expand...

It looks just like my Yanmar one, which is similar in principle to that one though it looks a bit different. On mine, that thing is an allen grub screw. There is a trick to help get the shaft out of the coupling. Remove the Allen screws which clamp the coupling to the shaft, and place steel strips in the slots. Put the screws back in from the other side and tighten them onto the steel strips. Doing that opens the slot slightly and makes it easier to get the shaft out once the allen grub screw is out. It may also help get that pesky screw out by reducing its grip. Heat will also help, and I would try putting a shield of some sort round it and heating it.

If all else fails you can drill it out by hand. To do so you have to make a special and very useful tool. A ratchet hand drill. You need access to a lathe to make it. The principle is to use a ratchet spanner to turn a cobalt drill held in a chuck screwed to the end of a piece of hexagon bar. The other end of the bar is forced downwards by a screw clamp arrangement working on a strong fitting passed right round the object being drilled. It is slow but works because you can apply huge pressure to keep the drill cutting. As a volunteer on a preserved railway I have drilled steel rails for the fishplate holes, using a big morse taper drill in a commercial version, with no pilot hole. The drill was about 7/8 inch diameter from memory.
 
Looking at it from a "idealist" point of view it is not a desirable option. So just drill the bugger out and remove the shaft and "clamp" and rethink the flange from scratch.
 
If it's a roll pin in the hole it may be that the pin is rotating with the drill bit, preventing the bit from actually cutting into it. Even if you tried a bit that was larger than the existing hole it would still bottom on the pin and prevent further progress.
The only way out of that I suspect would be to drill from the other side.
 
rotrax said:
In my humble opinion you would be better served by drilling right through the shaft from the side with the screw, using the existing hole as a guide. USE A GOOD BIT, SLOW SPEED, PLENTY OF LUBE AND LOTS OF PRESSURE. Once through you will have a small hole perfectly in line with the opposite side. This will give you a pilot for a larger drill to go through from the other side to clear the end of the screw or pin.
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+1
 
I think it is a roll pin or tension pin what ever you would like to call it. That been the case unless your going to heat treat and soften it you wont drill it out!... if it was a good fit then you wont pull it out either. I would first ensure that the hole in the shaft does not in fact go all the way through and that maybe it is partially obscured with the remnants of an old pin (some of which are solid or only have very small holes through them) or some such other obstruction. Have a feel down the hole in the clamp on the opposite side and be sure you can't feel anything on the shaft surface to indicate any of the above. If you can then punch using the largest diameter punch you can get down the hole to try and drift the visible roll pin out from this back side. If there is no indication of this above then I would seriously think in the terms mentioned above of drilling down through the shaft using the centre hole of the roll pin as a guide and then increasing the diameter of this pilot hole to match that in the clamp from the other side. This would/should give you access the the shoulder of the pin in order to punch it out from the back side. The problem with this though of course is that it may/ will weaken your shaft considerably from that which exists now. The last resort if you can get good access to the back of the clamp is to drive the clamp off with a hammer in an attempt to shear off the pin. If you go for this the dangers are that you irretrievably damage the clamp. mitigation here is to keep the screws in the 'split' side just sufficiently tight enough / loose enough not to prevent the clamp sliding along the shaft yet stop it expanding and so try to ride over the deforming pin! I've done the last many times though it's normally driving the shaft out of a fitting which is well supported and very accessible! Good luck!
 
If it is a roll pin, I wouldn't be in the least bit optimistic about drilling it out in-situ - cobalt drills or otherwise! They really are pretty hard! With limited access to really get your shoulder behind the drill, I think it will end in tears.
 
Agree it is more likely a grub screw that has been drilled out partially. Can't imagine why anybody would use a roll pin in this application. Indeed on a Yanmar coupling (at least on the small sizes) there is no lock at all, relying solely on the clamp screws to hold the coupling on.
 
Adding my threepenny worth.... Whatever you decide to do it would be best to retighten the allen bolts because if the pin extends into the shaft the act of loosening the allen bolts will tend to jam the pin as the split springs open .
Could be that the pin was originally not that tight in the hole but movement of the clamp has caused it to jam.
I would imagine that the hole was threaded when clamp was new,it would not make sense having it without unless hole went right through.
 
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If it is a grubscrew locating in a dimple will the clamp open enough to let the end of the screw clear the dimple and let the shaft pull out?
If it is a rollpin in a blind hole first step is to seek out the person who did it and extract a terrible revenge! You won't drill accurately enough from the back of the clamp without first drilling through the hole in the roll pin. Is the clamp too expensive to destroy it and replace as that may be your easiest option? Can you get the clamp slack on the shaft then get a good alternating torque across the pin to see if it will shear?
 
Thinking what would I try next.. Clean everything all around and tie hoses etc out of the way. Couple of those asbestos type plumbers matts used for soldering pipes adjacent to joists...wrap or drape them strategically then get the blowtorch with needle flame going on that pin end. Couple of wet rags on the gearbox and shaft housing will give warning of overcooki g adjacent components and it would be handy to have a garden hose running and to hand ( take bung out of bilge/depth sounder)...

If there is a continuous slot running the length of the 'pin' then were laughing . There is the leverage point and the pin can de deformed I to a smaller diameter to encourage rotation..

Plan B . Hose, water lube, drill right through the shaft from the pin size and then rotate the shaft 180 edg and come back through to meet the 'pin' with larger drill bit
Plan C angle grind or hacksaw or Dremel a new slot across the face of the 'pin' tho this will cut into the surrounding casting a bit ( but so what, over engineered anyway probably) . Support the shaft with wood block and two wedges tapped up . And snack the new slotted 'pin' end bloody hard with a quality screwdriver, cold chisel and BIG lump hammer .
I assume reasonable dexterity arm strength and prowess in forcing tho ts metallurgical into acquiescence. Or get a young ' in in there to apply said hammer

Edit: in haste sorry loadsa spelling erors
Good luck
 
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vyv_cox said:
Despite my having suggested earlier that it is a roll pin, there is a very similar photo on my website here, bottom pic of Fixed Couplings, which is of a grub screw. Is yours a Volvo, maybe smaller with four bolts instead of six?
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Yes can see the similarity , though the OP has the 'hole' running at 15mm into the shaft! Either a heavy handed attempt to remove a stuck grub screw or a pin in a blind hole! If it is a grub screw that's drilled through then it should 'shear' off quite easily!
The home made extraction method shown on VyV's page might well be sufficient to shear it off!
 
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Not being silly, but how about lifting the engine, just enough to slide the shaft out forwards? Once in an engineers shop life becomes easier, and you are going to need re-alignment in any case.
 
ean_p said:
.The home made extraction method shown on VyV's page might well be sufficient to shear it off!
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I think that's what I'd try. Don't be tempted to use the gearbox flange instead of a drilled plate though.
Drilling a 7 or 8mm hole through 10 or 12 mm of ss with a hand-held drill will be a real PITA, A roll pin won't drill out either. Let us know how you get on if you do try it.
My plan B would involve an angle grinder, cutting disc and expenditure of about £60!
 
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