I have an expensive item that is manufactured from Billet Aluminum. It is assembled with 316 stainless steel csk hex head screws.
I need to disassemble and the screws are stuck fast.
The heads are 7/32" hex imperials (yep 100% sure - It's a US manufactured product)
I have tried encouraging Allen key with mallet - no good. Applied releasing oil - no good (happy to try a specific product if there is a particularly good one)
So far only one of the 8 have come out !
Now one way to approach this would be to use an impact driver ... I have a compressed air 1/2" square drive impact driver, and assorted sockets ... but would need a 7/32" hex insert ............ anybody know where I can get one ?
Many years ago I made my own using some spare sockets, spare allen keys, araldite and an angle grinder (to cut a suitable length of hex from the keys) - they're still going strong!
You can get adaptors from various square drive heads to a hex bit holder, and then a standard hex bit of the required size would fit that.
e.g.
formatting link
think my first approach would be a allen hex bit in my small cordless impact driver - it only develops about 20 Nm, but might shock it free. Failing that a full size cordless one before resorting to a full on 1/2" drive pneumatic impact driver
fittings do tend to lock on very tight because of the angle and area of the underside of the head. You need to shock these loose with something other than an unmodified right angled allen key which can't really be hit directly on the end very easily. A small brass or bronze drift is ideal, especially if you can machine a pip on the end in a lathe to keep it centred inside the allen screw so it doesn't jump about and mangle the aluminium around it. Or just cut a bit off an old 5.5mm allen key and hammer that. By mallet I assume you mean a wooden one. You *must* use a steel hammer to get a proper shock loading on the drift. Hitting something with wood will achieve three fifths of FA. If they still won't come out hit them harder! You won't hurt anything. It's like training a dog. Once it really knows who's boss it'll give in and stop dicking about.
To use an allen key in your impact driver simply cut a length off the long end with an angle grinder disc and use it in a 7/32" socket.
Absolutely no point using releasing oil. The joint will be fluid tight.
You also must tighten back up each screw you loosen to take the load off the others and when all are free remove them one at a time.
If the screws are loctited in then applying heat for a while will soften it.
Car engine oil pumps are often held together with csk allen screws and I've had to remove god knows how many ultra tight ones over the years but nothing has ever failed to succumb to the right technique.
I'll bet you a pound to a pint if you cut a bit off an old 5.5mm allen key, belt that firmly with a claw hammer a few times and then just use a good tight fitting 7/32" key they'll pop out as easy as anything.
Not really. You just drill the heads off and you're left with a bunch of easily removeable threaded stubs after the cover is removed. Just use a drill a gnat's bigger than the screw shank and drill until the head spins off.
My worry would be damaging the Aluminum .... hope it does not come to this.
I have ordered a Hex socket bit .... I'll try walloping it a few times to seat it well, and hopefully loosen the fit. Contacted the manufacturer - he said this is very common ... suggests using a Torx bit and driving that in ... so it cuts itself in, plus the driving in will loosen .. and then it should come out.
He did add a standard 90 degree bend allen key is no use, needs a socketed driver.
You drill using a size slightly less than the thread diameter. You'll get a pretty good centre using the hex. A tap with a mallet on the back of the top part should then break the head off. If the top part can then be removed, a pair of grips on the thread should remove that. Perhaps soaked in penetrating oil overnight if corroded. Happens all the time with BMW disc brakes. ;-)
My experience with impact drivers says they are less likely to break things than steady pressure. Although a very powerful impact driver could be different.
Given the comparative rarity of impact drivers it's obvious that the primary use of the type of tool which the OP has is as a hand tool. Few people routinely reach for an impact wrench for every tight nut, bolt and screw. I hardly ever use mine and of course there is often no access for an impact wrench, so it makes sense to try basic conventional methods first as I suggested.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.