Recommend some metal drill bits and technique?

[AnthonyH]

I need to drill out some metal screws to take off some body work. Can someone recommend some drill bits? All I have are assorted pound shop or B&M type drill bits and I don't want to be drilling these all year!

Is there a good technique and things to avoid?

 

[AndyRKett]

Colbolt steel drill bits, and the technique is to just drill though everything in seconds.

I was put on to these by a guy who repaired cherry pickers. They will go though alloy bolts like they are butter, where hss bits would work harden the bolt then go blunt in seconds.

The colbolt bits are expensive but worth every penny in the time and frustration you’ll save.

Tool station is a good place to get them

 

[AnthonyH]

Colbolt steel drill bits, and the technique is to just drill though everything in seconds.

I was put on to these by a guy who repaired cherry pickers. They will go though alloy bolts like they are butter, where hss bits would work harden the bolt then go blunt in seconds.

The colbolt bits are expensive but worth every penny in the time and frustration you’ll save.

Tool station is a good place to get them

I've just seen some at Toolstation for £10, there are some for £60 but the difference will be marginal I'm guessing.

I tried drilling some screws with cheap bits earlier in the year. I was sweating by the time I finished, would've been easier at the gym!

 

[varesecrazy]

Heat is your enemy,( it will get harden the screw)

So Not mega fast,
feel free to cool it, water is fine

Before and during, look at the tip of the drill,
if it is rounding the edges, Stop and change the bit

You are probably only looking at 3 or 4mm drills,

But with Bigger bolts, 3 or 4 would be my ideal for coreing out the Centre, you can cut pretty quickly

If you are leaning on a @10mm in steel it will quickly get HOT due to the area of contact , potentially "work hardening it"

 

[vexorg]

I find quality of drill bits hit or miss, some are great and last, orther jsut blunt really quickly. Generally though some £5 drill set from B&M isn't going to last.

Slow drilling is needed for metal, you should be able to see it cut at the tip as you go into it. Most drills are variable speed these days.

 

[AnthonyH]

I get the idea now. Use a small drill bit, use low revolutions and use a spray of water. Generally to keep the screw head as cool as possible.

The head of the screw has a diameter of 12mm and so I'm guessing the thread is around 6mm diameter. It shouildn't be too difficult now I know what to do.

 

[HughJarsse]

Colbolt steel drill bits, and the technique is to just drill though everything in seconds.

I was put on to these by a guy who repaired cherry pickers. They will go though alloy bolts like they are butter, where hss bits would work harden the bolt then go blunt in seconds.

The colbolt bits are expensive but worth every penny in the time and frustration you’ll save.

Tool station is a good place to get them

Agree with Andy K here.
As a retired machinist/engineer, would only use cobalt or carbide (though carbide is very expensive, and mostly used for machining on lathes, and mills etc, and only really for batch/mass production).
I would rather pay for the better Cobalt drills, and save time and frustration caused by using cheap HSS or even titanium coated, (as the coating wears of quite quickly, and if re-sharpened, its then only HSS underneath. Cobalt are solid, so sharpening still leaves the carbide cutting edge)
Allow the drill to cut itself into the work, don't push or force it, slowish speeds, minimal pressure, and keep it lubricated (I use cutting fluid, (as I do a bit of machining, having a lathe and a mill) but any coolant is better than none at all)
Personally use Bosch cobalt drills, but any reputable make is OK, though some of the cheaper ones aren't as good as 'branded' ones.
Buy decent kit once, or cheaper kit many times, the decent stuff is probably more expensive to start with, but will last, and be more effective, and cause you far, far less aggro..

 

[vexorg]

The head of the screw has a diameter of 12mm and so I'm guessing the thread is around 6mm diameter. It shouildn't be too difficult now I know what to do.

Not quite sure what you are drilling out, are you hoping to keep the old thread? there's a good chance you'll destroy the original thread if you plan to go beyond the head.

 

[AnthonyH]

Not quite sure what you are drilling out, are you hoping to keep the old thread? there's a good chance you'll destroy the original thread if you plan to go beyond the head.

I'm drilling out screws on a rear bumper.

From what you've said I think I need the drill bit to be smaller than the screw thread. This does beg the question when the head is off how do I get the screw body out?

I've not drilled anything out before, so I guess it'll become obvious one I get started...maybe I'll ruin some threads - all part of the fun lol.

 

[vexorg]

If just drilling the head off then needs to be bigger than thread size.
If drilling the old screw out then you'll need to be lucky. You do get extractors that require drilling down the centre.
Or just drill and re-tap. Or use inserts or helicoils if you need the same size.

You do also get the easyout tools that can remove bolts with chewed/rusty heads.

 

[AnthonyH]

If just drilling the head off then needs to be bigger than thread size.
If drilling the old screw out then you'll need to be lucky. You do get extractors that require drilling down the centre.
Or just drill and re-tap. Or use inserts or helicoils if you need the same size.

I see, once the bumper is off I might have access to the thread on the other side, will have to wait and see.

 

[AndyRKett]

What is holding in the screws on the back side, A lot of the bumper screws on more modern fiats go into J - Nuts which are just a thin metal clip that clips over a piece of plastic and offer some structure, but because they are so small they rust and fuse themselves to the screw.

If you have enough of a head then you could use a dremel of angle grinder to put some new flat edges on the bolt and use that to get a spanner on?

If they are screws and they have stripped out then you can get extractors for them as well.

 

[AnthonyH]

What is holding in the screws on the back side, A lot of the bumper screws on more modern fiats go into J - Nuts which are just a thin metal clip that clips over a piece of plastic and offer some structure, but because they are so small they rust and fuse themselves to the screw.

Some of the screws go into a thin metal clip as you've described, others are in the wheel arch and I'm not sure what they attach to on the other side.

If you have enough of a head then you could use a dremel of angle grinder to put some new flat edges on the bolt and use that to get a spanner on?

If they are screas and they have stripped out then you can get extractors for them as well.

I'll keep these in mind.