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MG MGB Technical - Drilling out trim rivets

I'm getting my GT stripped down for painting, and drilling out the rivets is problematic. A new (titanium coated) drill bit went through very well at first, but now seems quite dulled after about a dozen rivets. I don't want to use a chisel so as not to damage the anodized aluminum. Any suggestions as to drill bit material (titanium/cobalt/HSS) or cutting speed, or do I just have to resharpen the bit after every 10 rivets?

Thanks,
Paul

Paul K

Most rivets used for trim were aluminum, so a titanium coated bit should last longer than yours seem to. Some rivets were steel, but even so, mild steel, so that they deformed easily when installed. These too should allow your bits to last longer.

My guess is, Paul, that titanium coated or not, what you may be encountering is aluminum build up on the bit surfaces from the rivets. I had this happen when doing the same work as you are doing.

You can buy yourself a bottle/tube of machinist's lube (harbor freight sells it) which is designed to cool and lubricate these bits so that they go through the metal more easily and cleanly, and help to prevent accumulation of softer metals on the drill bit or cutting tool. Even a drop of oil when drilling each may make a difference for you. Drilling dry will work, but a lube can help shed chips and prevent aluminum, especially, from collecting on the tool/drill bit. Les Bengtson may be able to offer up a better suggestion.
Bob Muenchausen

May want to try a smaller drill bit. You really only have to drill until the head is detached from the body of the rivit. This requires a bit just slightly bigger than the hole

Even if you have steel rivits, you should have no problem. I did all my rivits on my GT with a standard bit.
BEC Cunha

Paul. There are a lot of cheap drill bits, and other machining cutters, out there today. I have had imported 1/8" carbide end mills break as soon as I have started a cut. The US made bits and end mills seem to cost more and last better than the imported stuff. Thus, first choice would be a good quality, US made high speed steel drill bit. If that does not work, cobalt is harder and lasts longer than HSS. Carbide is stronger than either but tends to be more brittle. Rutland Tools is located in California and may be able to provide what you need in a timely fashion.

Les
Les Bengtson

The main problem I have is that the rivet starts to spin before you have cut the head off. You can usually just tap the remains off with a screwdriver by then though. I just use a steel drill just big enough to remove the head.
Stan Best

one idea use a small punch and punch what is left of the mandrel from the center of the rivet that way the tip if the drill will not be held of the rivet,to stop the rivet spining drill at a slight angle the srivet my spin but slower than the drill and it will cut the head off
andy
andy kennedy

Use a high speed steel drill bit. It's more flexible, less brittle, and more forgiving on handheld drills. Do not opt for any extra features, just quality high speed steel, made in USA or Germany or somesuch.

Fancy super-hard drill bits offer no advantage (you're drilling into soft metal) - and they're no good when you're drilling kinda sideways by hand. Carbide bits die young in conditions like these. Titanium is no friend of yours. No, sir, plain old steel saves the day as usual.

A 1/8" bit worked fine for me. The bit will center and push the rivet through, and a little pressure keeps the rivet from spinning while you drill, most of the time. Most rivets come out in seconds apiece, while a few will annoy you greatly.

One or two HSS bits should do the whole car.
Sam Good

Thanks for all the excellent advice. I found the solution after making a mistake. I used too much presure on the 1/8" bit, and when it went through the hole, it snapped. I went to the next size up in the index (9/64"). Not wanting to enlarge the hole, I slowed down the drill speed, and voila! I was getting a nice continuous curl of metal, an indicator of correct cutting speed, instead of small chips. The rivets on the LH side of the 2 pieces above the door and rear quarterlight were steel as opposed to aluminum (DPO strikes again!) but I got through them as well, and now all the trim is off the car and ready to be re-anodized.


Paul K

This thread was discussed between 02/09/2007 and 07/09/2007

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