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Diamond Drills

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sparky mike24/10/2020 08:02:58
207 forum posts
50 photos

I have to remove a dozen Phillips head self tappers from rusty steel plate and each one has rusted in tight. Nothing will shift them and can't use heat as they are next to fiberglass.I need to remove the heads so I can remove a chrome trim piece that is unobtainable, so must not damage it.

Where can I buy decent diamond drills from ? The Chinese ones last two minutes and then go blunt, so no go there.


Mike Poole24/10/2020 08:18:40
2816 forum posts
66 photos

If you have a steady hand could you slot them with a Dremel disc for a screwdriver? They will probably shear off with a decent screwdriver. A carbide drill will be hard enough to drill the heads but chipping the edge may be a problem. I am guessing the job doesn’t have the mass to allow an impact driver to be effective.


Tony Pratt 124/10/2020 08:33:29
1277 forum posts
5 photos

Mike has listed the 2 methods I would try.


sparky mike24/10/2020 08:48:12
207 forum posts
50 photos

No Good, a Dremel disc would damage the chrome brass strip that is held on with the screws as screws are countersunk.


Tony Pratt 124/10/2020 08:53:28
1277 forum posts
5 photos

You can buy left handed twist drill, I've had success with them.


sparky mike24/10/2020 09:00:03
207 forum posts
50 photos

Any normal good quality twist drills will not touch these screws. They are well hardened.

All I want to know is where to buy decent diamond drills. Have tried all the obvious methods.


Speedy Builder524/10/2020 09:09:50
2150 forum posts
152 photos

I see that is selling US made "quality" diamond drills - packets of 10. for about 20 dollars.

John Haine24/10/2020 09:28:42
3441 forum posts
185 photos

It might be worth trying a Heller cobalt drill?

pgk pgk24/10/2020 09:30:59
1978 forum posts
288 photos

No experience with them but: here

It'd also be another situation where a high speed dental handpiece with coolant and enough patience to paint away the head of the screws. Dental burs are cheap. Back when i was working I used to make hip toggles out of scrap intramedullary pins, eyeballed, using my dental kit. Cheap handpieces are just that but work well and can be adapted to a shed compressor.

David George 124/10/2020 10:01:21
1390 forum posts
448 photos

You can buy special carbide drills they can drill HSS taps so screws should be no problem.


Michael Gilligan24/10/2020 10:24:43
16674 forum posts
727 photos
Posted by sparky mike on 24/10/2020 09:00:03:


All I want to know is where to buy decent diamond drills. Have tried all the obvious methods.




david homer24/10/2020 10:52:49
28 forum posts

After seeing this post I caught sight of this add on you tube, not sure if these are any use but are made for the application you need, hope the link works™-screw-extractor4-pcs?variant=32927540707363&gclid=EAIaIQobChMIr5zLofnM7AIVyt3VCh2w0ggiEAEYASAAEgKIw_D_BwE


Andy Gray 324/10/2020 11:15:05
49 forum posts

When I did some work with diamond tooling years ago, machining steel was an absolute no-no (it reacts with the diamond under very high pressures, IIRC). CBN was needed for ferrous metals.

UK drills do tungsten carbide tipped drills which might be a better bet if cobalt ones don't work.

Carbide tipped

Cobalt for hardened steel

Les Jones 124/10/2020 11:46:32
2171 forum posts
149 photos

If you know someone with a small EDM (Electrical discharge machine.) that would probably work.


Edited By Les Jones 1 on 24/10/2020 11:46:54

peak424/10/2020 13:14:41
1268 forum posts
146 photos

Sparky, Sorry if this is a long post, when you've only asked where to buy diamond bits.

Like you, I've struggled with exactly this in the past, and had poor success even with reasonable diamond drills and burrs.
Obviously the problem with the latter is skidding and damaging the trim, and the former just don't seem to have enough diamond in contact with the offending screw head.

Two things spring to mind here, depending on how damaged the screws are;

I assume Philips or Posidrive heads, where a normal screwdriver cams out and damages the slots.
It's possible to get diamond dust coated driver bits, to fit the normal driver/socket set handles.
These allow the diamond dust on the bit to bite into the screw head and help stop it camming out. It may well provide enough grip such that you can shear off the heads. I think they are also available for plain straight drivers as well, but never looked for them.

As other posters have mentioned there are Tungsten carbide bits available which look a bit like masonry bits, but are of a grade and geometry which allows one to drill even high speed steel. I use them for drilling holes in machine hacksaw blades to shorten them for my 9" Rapidor Minor. These generate quite a lot of heat and I suspect will cause damage to both the chrome strip and the underlying fibreglass, as well as bursting through unexpectedly; they need a lot of pressure to work effectively.

I've recently been drilling some conventional hand hacksaw blades with smaller holes, and for that used a high speed bench drill (10,000rpm) with solid tungsten carbide PCB drills, which come on a 3mm shaft. This worked fine without damaging either the drills or the blades. The drills are easily and cheaply available off ebay or similar.

Do you have a woodworking router or a die grinder (electric or air)? ( a Dremmel or Proxxon would do at a pinch, but ideally with the little drill/router attachment.
Either of these should give sufficient speed to run these solid carbide drills.
You might need to make a new collet to take the smaller drills, as normal small cutters/stones are either 6mm or ¼"; I've made a replacement 3mm collet for mine.

I think I'd use my plunge router with a sacrificial wooden base, carrying a groove to fit the trim. This would locate everything and help prevent skidding.
I'd try with the diamond coated screwdriver bits first, they might just remove the screws OK, but if not, should be hard enough to properly round off the inside of the heads to form a nice countersink to locate the carbide s drill bit.
Any of the four internal corners remaining will chip the carbide bits.

Good luck


Edited By peak4 on 24/10/2020 13:18:09

Jeff Dayman24/10/2020 14:25:07
1924 forum posts
45 photos

When I am faced with this sort of screw removal issue from parts that must not be damaged I use my home-shop-built EDM (the Ben Fleming design mk1 with mods) and a hex brass or milled copper hex electrode. This burns a hex pocket in the screw and a hex key in the new pocket plus penetrating oil usually gets them out without any fuss. Since EDM is a zero force cutting technology, if the electrode is placed carefully over the work , the ram holding the electrode drive is fixed in place, and depth of cut is checked frequently there is almost no risk of damaging adjacent parts.

My EDM machine was simple to make, not too expensive, and has paid for itself many times over by handling repairs and screw / broken tool removals hard to do by any other method.

Nicholas Wheeler 124/10/2020 15:03:53
419 forum posts
22 photos

An important thing to consider when working with cross-head screws is that the screwdriver you're going to use on them is a consumable!

It needs to be the right type(Phillips, Pozi and JIS are not the same) and in good condition. Even a slightly chewed tip will ruin perfectly good screws. Any driver in this condition should be taken to the grinder and turned into a pick/awl/scraper/general poky tool, or you'll put it back in the box and bugger up more screws in the future.

If possible, use an impact driver from the start.

You can buy specific grip paste for use on screws, but fine grinding paste works almost as well.

Sometimes grinding a slot across the head gives enough grip to undo the screw.

Once it's rounded out, drilling is necessary.

Anyone who has worked on aircraft will have their favourite methods for removing small cross-head screws because planes are littered with the bloody things; it takes a day to remove all the inspection panels on an Islander....

sparky mike24/10/2020 16:25:27
207 forum posts
50 photos

Thanks for all posts, the last three or four most interesting. I have a spot welder and considered using that to soften the screw steel but can't get to the back of this trim for the other electrode. The item I am trying to remove is the cant rail (gutter rail) from a classic car and its made of unobtainium.

I have ordered some cobalt drills so will see what they do. I only need to remove the heads and then can remove rail and then I can attack what is left of the screw if not flush with the surface. The cant rails are going to be re chromed anyway so the slight scratch here and then is not too much of a problem.


Phil P24/10/2020 16:47:44
671 forum posts
168 photos

I know this is a bit of the wall but if the screws are steel and the strip is brass, could you dissolve the screws out with Alum ?

Its a bit akin to removing a broken tap.


Edited By Phil P on 24/10/2020 16:50:35

Steviegtr26/10/2020 16:36:38
1660 forum posts
202 photos

Did you get the screws removed. I just saw this ad for a screw removal kit. Looks pretty good.


Screw removal tool

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