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anyone have experience drilling holes in either ar400 or ar500 steel?
somewhere I read that using annular cutter that is tungsten tipped is a good way to go.
if im going to do this I only want to buy drill bit once and want to be sure to get something that won't end up in the scrap pile after just a couple holes. the local steel supplier will cut up a sheet for no extra charge but they dont drill holes to make hanging targets
Bif: The key to drilling holes and not burning up the bit, is to run the drill at the appropriate speed for the material you are using. Most try to run the drill faster than it should be and this is a problem with most Drill Presses, they simply run too fast..
A regular Hi Speed Drill Bit will work just fine.
For steel a 1/2'' drill bit should be ran at < 300 rpms. Slower is fine. Some cutting oil is nice. A 3/8" bit needs to run at about 400 rpms. 1/4" needs to run about 500 rpms. Anything above 3/4" you need to run at 150-200 rpms or less,,,
bigger = slower. Period!!!
In Aluminum you can run any size bit up to 1/2" at 1200 rpms using WD 40 for cutting oil. Once again Slower is not a problem .
If you can't slow your Drill Motor or Drill Press down to these speeds then you are going to have problems with any drill bit.
Once again Slower is not a problem, it will just take a little longer to drill the hole, but you won't overheat your drill bit. If you've got nothing else use lots of WD40 on it. But some decent cutting oil will help. Citgo 130 is a good one.
The gold lookin' (Titanium Nitride Coated) ones are a little more tolerant of incorrect speeds. But not enough to warrant speeds that are more than about 10% higher.
Hope this helps.
Randy
Depending on the quantity and diameter of the holes, a good quality HSS drill from a reputable manufacturer such as Cleveland Twist Drill, Guhring, Precision Twist Drill, etc, will be sufficient enough. I've drill hundreds of holes in AR500 plate and have always used HSS drill. I really don't see the need in spending money on an expensive Annular cutter when a HSS drill will work just as well.
A lot drill to big of a pilot hole also. Look at the end of the bit the pilot only need to be as big as the web ( straight line in the middle) or just a little bigger. To big and the drill dosnt center well and wants to grab and suck into the work. A good cutting oil helps a lot. Set up makes a big difference a solid set up in a Mill. drill press, or magnetic drill will work mush better than a hand held drill motor.
When drill like above break the chips often as they are strong and will rab clothing and suck you into the drill. No loose clothing, watches rings,Hair covered under a hat. NO GLOVES.
Cut it with a torch if you just need hanging holes. I used to work at a fab shop that built armored store fronts - we used a CNC water jet to make all piercings.
You want cobalt drills with a 135* split point. Not 118*. Use cutting oil and proper rpm and feed.