Sheared screws

[petrolhead]

I took my water pump out yesterday, and predictably a couple of the housing screws sheared off!<br />I assume these are s/s screws, I've never had much luck drilling steel screws out of aluminium castings so I guess this may be difficult and I'll need professional help.<br />Is this a job any machine shop should be able to tackle, or should I be looking for some sort of specialist? <br />The scews are sheared off flush with the casting BTW, so there's nothing to get a hold of and no way to grind a slot to get a screwdriver in.

 

[petrolhead]

Re: Sheared screws

Before anyone answers this I already solved it myself!<br />I took the unit to the local marina to get an opinion, their engineer said he had done this on a lot of old engines and he'd drill the screws out, right through the casting, and replace them with a screw right through from the outside with a nut on the inner end to retain the water pump. As he said, not very elegant but it works.<br />I actually improved on this, I drilled the screws out carefully, centre punching them then starting with a small drill worked up to a 3.6mm. Then with a sharp implement I picked out the remaining bits of screw thread.<br />Then I ran a 4mm tap through the hole, cut the heads off four 4mm s/s screws, and screwed them into the holes with some studlock compound.<br />When it sets I'll re-install the pump and put a nylock nut on top of each stud, they should last for years!

 

[OBJ]

Re: Sheared screws

Nice enginuity petrolhead.

 

[petrolhead]

Re: Sheared screws

Thanx OBJ! Thinking about it my fix may be better than the original, screws will almost certainly become stuck in the case at some time due to corrosion, but the s/s nuts on my s/s studs never will.<br />I'm beginning to get the hang of this now, having made or repaired several parts for this motor!

 

[OBJ]

Re: Sheared screws

What's nice about your idea is that it can be adapted to many other applications where screws/bolts can be replaced with studs. Please share anyother ideas/fixes you come up with. Ain't none of us to old to learn.

 

[Paul Moir]

Re: Sheared screws

Earlier this spring I was pulling apart my brother's neglected 4hp Merc to change the water pump. It took two days of heat and oil to remove the lower unit because of aluminum to stainless death grip corrosion. So finally I was looking at this water pump that surely hadn't been changed anytime this millenium, and thinking to myself about the task ahead trying to get the water pump bolts out. But lo and behold, they were actually stainless nuts and studs! It came apart with ease after at least ten years operation in salt water.<br />So I'm convinced studs are better!

 

[OBJ]

Re: Sheared screws

But as your post points out Paul, being selective as to where to use them would be a must. Some places you might have to remove them again.

 

[petrolhead]

Re: Sheared screws

Removing them is easy, if you put them in with studlock or epoxy you can soften it by heating the stud with a gas torch, then they come out easily. If you're afraid of damaging the surrounding metal or adjacent components, a large soldering iron provides enough heat for all but the largest studs.<br />But I agree, they are not suitable for every application.