View Full Version : Drilling AR400 Steel

10-30-2006, 01:36 PM
Anyone know whether AR400 (abrasion resistent, BH 400) can be drilled easily with HSS or cobalt drills? Got some 1/2" AR400 plate coming for LR rifle targets, and need to drill a couple of 1/2" holes for mounting the finished targets on stands.

Optics Curmudgeon
10-30-2006, 01:48 PM
Might be abrasion resistant, but I'll bet it's not plasma cutter resistant. If you just need holes for mounting that would be the way to go, if you have one, or a friend that does.


10-30-2006, 01:52 PM
Never drilled it as it says it is hardened and tempered try this thread :-

10-30-2006, 02:28 PM
I've put lots of holes in AR400...with a cutting torch :D
Only success I've had drilling the harder stuff was with QT100. Drilled 3/4" holes in a bunch with a big radial. Lots of coolant, slow rpm and as much feed as it could stand.
Let off the feed...instant work hardening.
Had to sharpen the bit for each hole but the job got done.
I know there are prolly guys here who have drilled 400...

10-30-2006, 04:47 PM

The shop were I used to work did this all the time. Take a torch and heat the area to a dull red and let cool. Then drill your hole. We made allot of wear plates for a local brick company were the holes had to be drilled, and then countersunk for bolts. It worked for us and it will work for you. We used HSS drill bits and carbide counter sinks.


10-30-2006, 07:49 PM
Use cobalt or better still solid carbide drills with a 135* angle, lots of coolant and a slow speed. Be prepared to sharpen drills frequently.

10-30-2006, 10:42 PM
That's kinda what I thought - use a torch. We didn't have to drill any holes in the first batch of targets we cut out, but these are going on stands, and will use grade 8 carriage head bolts to attach the frame of the stand to the backs of the targets.

Thanks for the info, guys.

Mike Burdick
10-31-2006, 12:22 AM

You probably know this already but if not....

If one wants to "drill" nice holes with a hand torch make a guide plate. As an example, use a piece of 1/8 inch plate steel (about 6-inches by 6-inches or whatever) and machine a hole in the center such that it is the diameter of the hole needed plus the diameter of the cutting tip and maybe a little more for bolt **clearance. To this plate, tack weld four pieces of 1/4 inch steel (1 inch by 1 inch) about two inches away from the guide hole's edges and space them equally. These pieces elevate the guide so that the hot gasses have a place to escape!

Now all one has to do is locate where the hole is needed and clamp the guide. To cut the hole, first start the cutting in the center and then work to the edge of the guide and zip around it. With a little practice one will have perfect shaped "holes" that are all the same size!

A note here...if one makes the guide heavy enough it might not even need a clamp to hold it in place - which is nice if the holes are located where a clamp cannot be fit. What works even better is if the guide can be welded on with a very small tack - something that can be easily broken off with a light hammer blow. This way there is nothing to get in the way of the torch or one's arms. :)

** This depends on the size of tip and flame size - some tips cut a fairly large kerf - so experiment a little to find what is needed.

10-31-2006, 09:06 AM
I have drilled AR 400 and AR 500 quite easily as long as I used a drill press and kept good preasure on the bit and using tapmagic ...you let it ride any and it will work harden. The biggest holes were 1/2" and were mounting holes on the big Pepper Poppers, so I know it can done.


10-31-2006, 01:47 PM
Recently repaired a bunch of our trench boxes. Reskinned some areas wit AR400. Had to put two 5/8" holes in each cell to shoot foam in to fill annular space. Used a Milwaukee mag drill, made a 3" dia. dam w/clay around each hole to be drilled to keep fluid in. Moderate pressure, no real problem other than a resharpening exercise on bits afterwards

09-26-2010, 05:51 PM
I had to drill holes in some AR400 plate 7/16 in diameter. Using a SFM of 30 and a CPT of 0.003. I sucessfully drilled 24 holes using only one HSS drill for all the holes and no issues. No re-sharpening requried.

Liger Zero
09-26-2010, 05:56 PM
Might be abrasion resistant, but I'll bet it's not plasma cutter resistant. If you just need holes for mounting that would be the way to go, if you have one, or a friend that does.


...good excuse to buy one. :D