How do I undo this screw?

Some years ago I installed a small safe which I bolted to the floor with a couple of the supplied screws. SWMBO says she would like it moved to a more accessible place, but I can't undo the screws. The photo is the best I can do, but it does show the type of thing. It has two shallow, concentric, hex sockets. The large one is 6mm AF, and the small one is 4mm. They are both very shallow - too shallow for a normal Allen key to get a purchase. I must have used a special tool to insert them, but it's so long ago I just can't remember; and I certainly don't have it now.

I've tried using 6mm and 4mm keys, but they just cam out.

After a good look at the (rather poor) photo it appears to have a 3rd, even smaller, hex socket in the middle, but I can't measure it.

Any ideas folks?

Angle grinder ?

How hard is the screw? Drill for the largest screw extractor that won't interfere with the thread?

Arc-weld on a bit of rod with a tommy-bar?

Instead and despite the risks, have you not tried telling SWMBO it can't be done?

If you have a welder, hold a, (non zinc plated), nut over the screw. Weld through the hole and unscrew with a spanner.

I've had more success by deeply countersinking the top face of the nut first, so it's easier to get the mig wire down to the bottom.

Bill.

Get a bit of silver steel and mill suitable hex sizes onto the end, harden and then use to fit the screw

Are the heads hard? If not just drill them off, you've got a centre to start the drill. You'll need to sharpen the drill afterwards

Use your 6mm hex key, but to stop it camming out, grind the end of the key flat, as if it is a decent key it will have a profiled end.

Unfortunately, there is no room in the small safe to wield a drill or an angle grinder. The best I can do is use a small Dremel type device, but I'd much prefer to get the special tool..

Why not contact the maker and ask for a replacement tool?

Gary,

It's 'Uni Screw'. I bought a box some time ago. The idea was that one bit would cover a range of screw sizes. Needless to say, the bit has long gone.........

I'm trying to upload a photo of the box.....just hang on.

I did a search on line and found a firm that makes the screws to order, but never got a new bit. I'll have a dig to see what I can find.

Rgds,'

John

Edited By John C on 22/06/2018 12:25:27

Edited By John C on 22/06/2018 12:29:39

I'm struggling with the photo Gary - I'll get there eventually. Meantime, this may help:

**LINK**

John

Hi Gary

You should get 5/16 hex bit with 6mm on the end, grind the 6mm end so that it is flat and force it into the bolt withsome type of lever to apply downforce. Use a suitable spanner to undo.

Cheers

Roger

Gary,

I can get quite a good grip with a Torx wrench - might be worth a try,

John

Sharp cold chisel to try and 'spin' them out.

A dab of valve grinding paste on the end of the allen key sometimes helps it grip.

Otherwise, Dremel tool is looking pretty good.

I think Uni-Screw was a turn-of-the-millenium idea that never really took off. Not much sign of Uni-Screw drivers or bits on the net today.

I think you're right John about it being a Uniscrew.

I managed to get a better photo, and also managed to get a reasonable impression on a bit of polymorph plastic - the is the other photo.. Now if I could get a bit....

Hello Gary,

From the later picture and the impression it seems the fancy hex forms are contained within a raised section; does that leave you enough room to get a grip on the outside of it with a pair of Mole Grips?

Regards

Brian

Hi Brian,

No, I've tried that - the head is very shallow, as are all of nested sockets.

Should be easy on plenty of depth there just find a good fitting allen key.
No good if it has play in the hex, best found to date are the plastic covered Wera, fit hex better than anything else.

I use shallow head sockets every day, feed allen key in square press down whilst giving it sum.