Have a new chrome rear bumper and want to mount license guard , so I need to drill some holes in the bumper So I was gonna tape where I have to drill so I don't scratch to much but is there anything elsei need to do so I don't screw up royally ??
i always hate drilling chrome. you've got the right idea with tape. make sure you have a good sharp bit and a steady drill hand. good luck.
Go get two masonary bits the same size as the holes you want. I needed 1/2" ones so I used two 1/2" masonary bits. Use tape just in case you miss. But this works great and will not alter the chrome. MAsonary bits are carbide tipped so they cut through quickly. If you try this with an ordinary bit you won't be very happy and when you ruin them all you still won't have two good holes. Tim PS this was done on my freshly chromed '54 one piece rear for a '51 license guard and I go the tip from an old timer who really knows his stuff.
Start of with a "NEW" 1/8th bit and work your way up. Center punch the hole after taping up the area and marking it exactly where you want the holes!
Center punch where you want the holes to go. Then use a sharp center drill to start the hole. Use at least a #3, the deeper you go the better but don't drill past the taper. The chrome is hard, but once you get past it the steel is easy. A little motor oil on the bit always helps. If you are stepping up the drill size, I would go in 1/4 inch increments. The corner of the drill is what gives up first, so haveing something to cut is better than just the a little on the corner, follow? Don't push too hard or run the bit too fast and everything will be fine.
PERFECT WAY TO DO IT!! Especially the center punch!! And, the start with 1/8" and step up is also right on the money.
And coat the inside of the hole with something before you bolt into it, since you've opened up bare steel and eventually it will start to rust.
I wonder if first grinding away the chrome at the spot where the drill bit will be drilling would be a good idea? Use a dremel.
Start with center punching your desired hole, start with an 1/8" bit, keep a cool wet rag handy & keep your metal cool so you dont heat it up and turn the chrome blue, work your way up to your desired hole size and cool in between each time you step up in size to keep the heat down. I always drilled the holes, then mask the hole, apply black bbq paint in a smaller circle then the bolt head size to seal the edge of the chrome front & back of the metal and once you install it, put a small line of clear or black silicone on the threads @ the head to keep ANY water out of the hole. If water gets in, it'll get under the chrome plating, bubble it and eventually flake it off. Good luck!
Use beeswax for a lubricant and don't let it stop cutting till your through the chrome. I'd use center pilot bits. You didn't say how big a holes you need, but start with a small hole the size of the pilot on your second bit, then drill the hole to final size on the second shot. Tape and centerpunches are you friends. If you are going over1/4", keep the drill speed down to prevent overheating the bit.
I agree totally with TERPU, anyone who has drilled anything chromed knows it will play hell with high speed or cobalt drill bits. My advice is to either grind off the chrome, which Im sure you don't want to do on a new bumper, or use carbide, a masonary bit is the most economical way.
I would not recommend trying to grind off the chrome first. This can cause unnecessary headaches. Remember that the chrome is going to be very very thin! The nickel underneath is what will be the material that is hard to get through. The biggest concern in drilling into the plating is that if it wasn't done just right you may have some flaking or peeling. Taping should help prevent this. I would agree with above statements that the exposed steel should be sealed with something to prevent future rusting.
definatley use 2 inch mask tape and agood center punch, and a new step notch bit, nice and easy use cutting oil also!
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