Drilling 15n20?

A

aarongb

Joined
Nov 2, 2007
Messages
299
Hi All,

I need to drill several blades of thin 15n20. The steel is annealed from Aldo, was easy to cut and grind, but when I went to drill holes, failure. I managed to drill one, mostly using a bad attitude and sacrificing a couple of bits. I took a break for a couple of days and went to drill more last night using a cobalt bit and a carbide bit on partial holes I already failed to drill. I was patient, I used a cobalt bit first, was patient and stopped when I thought it might overheat. Nothing was happening anyway. I moved on to the carbide(s), the longer one snapped at the tip (little too much pressure) the second just spins in the chuck of my drill press.

I don't have this kind of trouble with 1084 or O1, and those were thicker stock. Any tips on bits, speed, technique?
 
What size hole are you drilling and what speed are you using ?


Maybe you are work hardening that steel with too much heat
ie high speed and low pressure.


The larger the drill, the faster the edge turns and the lower RPM you should use

For example this chart
Mr-Skill-Drill-Speed-Chart-Metals.jpg




THIS is gold
www.bladeforums.com/forums/showthread.php/975598-Drill-your-holes
 
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Hole size started at 3/16, but moved down to 1/8 because that is the only size carbide bits I have. Speed is 1100 (Craftsman 10" drill press), and I tried 3100 briefly, but thought I heard that wasn't a good idea.
 
If all else fails get a couple of masonry bits. They are a couple of bucks and I have used them many times to drill harden steel.
 
If you removing small chips you're not applying enough pressure. When you have the right pressure/feed rate you will see nice long curly pieces being removed. You will be surprised how much pressure a 3/16" bit can take without breaking. The Count is probably right when he says you're probably work hardening the steel. I leave my press on the lowest speed 90% of the time and just apply enough pressure to get those nice curly q's I was talking about. Another thing to consider is that even annealed steel sometimes has an occasional hard spot here and there. I hope this helps and good luck.
 
Thanks all! I think I am work hardening as well, I'm getting bit shaped smooth depressions and bright steel turning dark blue/black. I get the curlies that Darrin describes when I drill 1084. I'll start from scratch, anneal, lowest speed, and some new bits (including masonry, just in case).
 
aarongb said:
Thanks all! I think I am work hardening as well, I'm getting bit shaped smooth depressions and bright steel turning dark blue/black. I get the curlies that Darrin describes when I drill 1084. I'll start from scratch, anneal, lowest speed, and some new bits (including masonry, just in case).
Click to expand...

Dark blue black chips indicate too much heat.
 
Get some micro solid carbide bits from HF, drill a hole through the center of the divot to mark the spot and start fresh from the other side. You may be able to salvage it that way. I've had hard spots in 15n20 before and had the exact same issue as you describe.

-Xander
 
Along with everything else mentioned I think feed rate and bit speed is key.

I just drilled 17 15n20 knives with 3/8" holes. I used a cobalt bit that has probably been used on 100 knives. I have a big press that I can run slow and apply a lot of pressure to. (and the bit is really done with, I ordered another one)

Run your drill slow and get some decent cobalt bits. They are very inexpensive for as long as they last and 1/5 the price of carbide which can easily break.

I had a really hard time with holes at first and was running through bits like crazy when I started.

Drilling a holes seems simple but it is tougher than it sounds!
 
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