Drill out a ht c/s allen screw

[Eric ArthrellParticipant @ericarthrell78468]

This might sound silly what an old fitter told me, but it is worth a try as it worked for me .

put an elastic band across the hex cap bolt push in hex tool firmly and twist at the same time.

and no this is not a wind up.

Hope this Help Eric

[JonParticipant @jon]

Posted by J Hancock on 26/11/2017 09:47:02:

If the 'core' drill goes out of centre and breaks into the aluminium you will be in big trouble.

Go the extra 'mile' to make a little jig up to make sure it does not wander.

You have to watch and feel for whats happening not a bull in a china shop.

Most can be done with nothing more than a hand held battery drill, no wandering use the hex to centre starter drill and larger drills will self centre, easy.
Also most of the getter outs are in to aluminium, done 100's and never ever failed yet.

[Tim StevensParticipant @timstevens64731]

Find a flat ended punch the same diameter as the heads of your screws. Support the workpiece on a firm surface (you don't say what it is) and using a steel hammer and holding the punch good and square, smack each head smartly once. This should have three results – the countersinks into which the heads sit will be compressed slightly, loosening the tightness, the metal of the heads will compress inwards making the hex holes slightly smaller, and the threads of the screws will be jolted back and forth in their holes, freeing any rust etc. This should mean that the screws will loosen easily, perhaps even with an allen key. Choose a key which is sharp on all six corners right to the end – and if necessary grind off the first millimetre or so to ensure this.

Unless the screws have been treated with Loctite, this usually works for me.

Remember next time that flat countersunk heads are least successful with hex sockets. This is one case where posidrive or a slot can work better.

Cheers, Tim

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Tim Stevens on 27/11/2017 18:43:49:

Support the workpiece on a firm surface (you don't say what it is) and using a steel hammer and holding the punch good and square, smack each head smartly once.

… < etc. >

.

With respect, Tim

"what it is" was described on page_1

[quote]

The engine is from a Bantam racer and had been put together with a lot of care and attention, eg plain bush replaced with needle rollers, homemade short stroke crank, shortened barrel, etc. The screws are securing the c/case packing and need to be removed as I intend using an ordinary crank.

[/quote]

MichaelG.

Edited By Michael Gilligan on 27/11/2017 20:21:18

[HopperParticipant @hopper]

Posted by JimmieS on 22/11/2017 14:46:59:

What a wonderful group of ‘workmates’ I have on this forum, freely providing advice with no thought of reward. Thanks to all concerned. Have tried all the suggested bench work methods without success – except for braking two new drills despite using slow, steady speed with coolant – so will buy some carbide drills. I am now wondering if the screws are indeed h/t.

The engine is from a Bantam racer and had been put together with a lot of care and attention, eg plain bush replaced with needle rollers, homemade short stroke crank, shortened barrel, etc. The screws are securing the c/case packing and need to be removed as I intend using an ordinary crank. The conrod is Yam RD400 which indicates it may have been built in the South West area. Could the engine builder have worked in the aerospace industry with access to high spec fasteners. And adhesive?

Jim

In that application, inside the crankcase, it would almost certainly have some kind of Loctite or similar on the screws to stop them coming out. A propane torch may be what you need there to break the bond.

If you are breaking drill bits you may be running the small drill bits too slow. They tend to grab and snap if you do that. Bit of a Goldilocks job: not too fast, not too slow, just right.

It would be worth buying left-hand drill bits. You usually don't have to drill out the full diameter then. Once you get close, the tension is relieved and the anti-clockwise direction of the drill bit screws the remainder out as you watch.

[JimmieSParticipant @jimmies]

Hi all

Job done using cobalt drills. Again many thanks to all who provided advice.

Jim

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