I have a small visor accessory I wanted to reposition the hold down metal part. The clip on it must be stainless steel I only need a 3/16 or smaller hole in it BUT boy is it hard to drill Should I just use a center punch and make a hole then use a drill or is their a another way to drill this thanks for the info..
Any good sharp drill will drill a piece of stainless a few times before it dulls. If possible try cobalt drill bits.
start with a smaller bit first, and make sure it's very sharp... even slightly dull bits have a hard time in stainless
Use a sharp drill and push firmly on the drill motor; don't let the bit spin on the stainless, it will just get hot, dulling the bit and work hardening the stainless which makes it even tougher to drill. A little cutting oil will help too.
Instead of using a conical point center punch, grind 4 sides on it so the point is pyramid shaped. A lesser bit sharpening angle helps too. 130-135 degree angle, low speed, lots of coolant or air and enough pressure to maintain a steady chip.
They pretty much got you covered the only thing I can add for lubricant is you can use a 50/50 Rapid Tap and cutting oil mix....straight antifreeze...or bar soap they all work well on stainless
Stainless work hardens, so you have to take big bites with a sharp tool and always run it slowly. A good sharp stub length cobalt drill run very slowly with a high feed pressure is best. Lubricate it with heavy/dark sulfurized or chlorinated cutting oil (dark thread cutting oil works very well). It is very hard to run the drill slow enough with a hand held vari-speed drill motor. You never want more than 1/4 throttle at most, even on the super tiny drills. If you over speed it, the spot will turn blue and go hard on you. The only way out then is to anneal the spot with a torch, or step up to a carbide drill. Any further drilling in that spot (without annealing) using HSS or Cobalt HSS drills will only result in frustration and dull tools. If you aren't making big stringy chips, you are running the drill motor too fast. Slow down and press harder.
Good advice here. One question, are you sure it is stainless? If it is chrome plated metal, then you have a different set of problems. Chrome is much harded than stainless and may need to be ground off before drilling.
First off, get the RPM right or you'll burn up drills. RPM = (CS x 4)/D. CS is the cutting speed, use 50 for stainless, not knowing the alloy you have. D is the drill diameter, .187 4 is a constant. Plug it back into the formula: RPM = (50 x 4)/.187 = 1069 RPM. You can center punch it, but use a small drill like an 1/8" to do a pilot. If you are using a center drill, they don't free hand drill so well, hold the piece in a vise. Do the whole thing in a vise if possible. For a few holes, WD40 works as a lube, so does house hold 3 in 1 oil. Bob
I used carbide tipped cement hammer drill bits in the drill Press! Cuts right through stainless! spring steel too!
One of the best lubricants for drilling SS or hardened stel is bacon grease or plain old lard. This comes from 40* years as a machinist. Dave
Slow, fast, and 1/4 throttle can be defined differently by everyone however using the formula provided by Bobss396 will get it right every time provided the SFM is known for a given material. Here's a chart: http://www.melcut.com/ti_melcut/MelcutCat_32.pdf The chart states a cutting speed of 20 to 50 surface feet per minute in 300 series stainless so to be safe start at the low end. For example 20 X 4 /.187 = 427 rpm minimum and 1069 as a maximum @ 50SFM. "half the speed and twice the feed" is the general rule for reaming a pre drilled hole as can be found here: http://www.wisc-online.com/objects/MTL8202/MLT8202.htm
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