I'm working on drilling some 9/16" holes in the trunk floor and I usually get "square" or effed up shaped holes instead nice, round holes. The larger drills' flutes usually catch in the sheetmetal when they drill through, and that aint helpin'. I started with smaller drill sizes. What to do, what to do? Thanks, Kurt
Get you a "center drill" bit.They are cut so that they are able to start a hole without walking.They are good also for counter sinking holes in thicker metal.A machine tool supply store should have them,some hardware stores carry them.
Your bst method is to use a hole punch like a greenly punch. Btut the cheaper method is to not use standard drill bits but to use a step drill bit. It will make clead round holes in sheet steel. Tim
If you can back it up where you are drilling even with a piece of wod clamped tight behind the hole will help
Uni-Bit............It will be your best friend. And they "can" be sharpened. I keep about 20 of them around all the time.
Rotabroach sheet metal hole cutters were discussed here a few months ago. I bought a Kit No. 11090 off eBay. I love it. Round, almost burr free, holes every time. Charlie
What he said. H***led trying to grind drill that wouldn't cut a a triangle hole in sheet metal for 30 years. One day Ronnie Benham was helping me fit the new hood on my roadster, and hauled out a Uni-Bit to drill the Dzus holes. Magic!! I went out and bought every size.
Unibits are great another way is a hole saw the type with a arbor that electricians use with a bi metal bit . The drill bit stops the walking as the hole saw cuts the metal.
Hole Saw are hardly ever centered enough to drill nice ROUND holes. 9 times out of 10 they are oblong or mount off-center I work with sheetmetal all day every day and Step-Bits (unibits) and Pilot Point bits by DeWalt are the cheapest and best thing to use. If youre having trouble with the bit walking, dril a pilot hole with an 1/8th inch bit first and you will minimize an squareing off of the holes. SHARP bits are the best.
I am hooked on step drill's use them on almost anything up to 3/16" thick. I buy cheep HF ones they seem to last quite well.
Agree with 39 Ford. One of the few things that I get from Harbor Junk worth a **** is their cheap Ti coated uni bits. I even find myself punching holes in 3/16 with them
Don't forget a hole punch. Requires a pilot hole, but punches clean. Not cheap but you will use it over and over.
Uni-Bit. They come in different size ranges and steps. I keep a couple in several sizes so I can reserve one for sheet metal and another for plate, etc. If cutting plate, turn them slow with oil.
I only use Uni-bits Or the Rota-Broach style for holes in sheet metal. I have a little air drill with an 1/8 bit (the double sided ones) that gets used for drilling pilot holes for both styles. The Rota-broach has an 1/8" arbor, and its easier to get the Uni-Bit started with an 1/8" pilot. I also use the same drill for clecos, it gets alot of use!! Jimmy White P.s. It always helps to use an automatic center punch to dimple your metal as well, it will help keep things from walking.
Another vote for the HF unibits.. they are sometimes on sale for 9.99 for the 3-pack. I've drilled through 1/4" plate with them before... Brian
I personally like this method I always keep a set of the most common sizes ground this way this is also the best way i have found to drill out spotwelds you can drill through just the top layer.
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