300 series stainless

Wayne Bensinger

Well-Known Member
Hello all,
I have question about something I've been dealing with for some time now. Just got real tired of it today and I'm gonna ask if anyone else deals with this issue.
I have a scrap steel graveyard near me and I bought some bolster materials off of the racks in the yard. They used one of those battery powered gun type metal testers on both of the pieces I grabbed. They told me one was 304ss and the other was 316ss. I took both because the price is like $1 per pound, it's a steal for steel, lol.
The stuff works great for bolsters, pommels, and guards and it takes a really good finish as well as cuts easy on my mill and band saw. The problem I'm have is that this stuff is extremely hard to drill, I mean really hard. I've tried a few different lubricants when drilling and even changing the drill bits angle a bit with no good results. Sometimes the holes actually get oversized or egged because of the chatter and wobble. Anybody out there have any ideas, please, before I just stop using the stuff.

Wayne
 

EdCaffreyMS

"The Montana Bladesmith"
Personally, I don't use 300 series stainless for any hardware on knives, partly for the reason you mentioned, and also for other reasons.

I suspect that your methodology of drilling is partly to blame for "egg shaped" holes.....that's a good indicator that you're either applying too much down pressure, turning the bit too fast, or both. What's happening is that the "chips" are not being allowed to clear, and those "chips" (some would say "curl") literally "wallows" out the hole as you drill it. Try going slower...by that I mean what I call "tap" drilling.

Put just enough down pressure to make the bit cut just a few thousandths at a time..... then bring the bit COMPLETELY out of the hole, and allow the chips to clear off the flutes....then repeat, repeat, repeat, until you complete the hole. IF any of the chips remain stuck in the drill's flute(s), clean them out with a pointed brass rod before going back into the hole....it's those chips that don't clear off the flutes, or out of the hole that is likely creating your issue(s). If you have to apply an unusual amount of down pressure....check the drill bit's sharpness. Many times I've had "brand new" bits that simply had issues of some type.....wouldn't cut the way I felt they should..... so I grab another one, and try again, or if the bit is large enough, I take it to the Drill Doctor for a light touch up, and the issue is very often solved.

In my experience, 135 degree split point bits work the best in these types of material, as long as they are SHARP. Any degree of "dull", and you're gona have issues.

There are certainly other reason these things can occur, but experience has taught me that what I mentioned above is more often the solution then not.

The following probably doesn't need to be said, but if it helps anyone, it's worth the words. Many individuals have the idea in their heads that when drilling a hole, the same methodology they learned to use on wood is the way to do it.....as much pressure as can be applied, in order to make the bit cut as fast as it can... train yourself to slow down, take just a bit of material at a time, pull the bit out of the hole and allow the "chips" to clear, and repeat...you'll find it gives cleaner holes, longer drill life, and much less frustration.
 

JMoran

Member
300 series stainless steel work hardens ahead of the cut. In other words, the last revolution your drill bit made left the bottom of your hole work hardened about .005 deep. If the next revolution cuts less than .005 deep, your cutting through the work hardened zone. The key is to stay ahead of the work hardened zone with enough feed, and not too much feed to bend your drill bit. I assume you are using small diameter drill bits. Carbide drill bits help, but you still need to get "the feel" for drilling stainless steel.

As Ray said a dull bit exacerbates the problem and pushes the work hardened zone even deeper.

The .005 figure is just a starting point if you have positive feed control.

John
 

Billy G

New Member
Yes indeed it work hardens. You can reduce the threat by slowing the drill down. 300 series stainless has a SFM of 40-75.

"Billy G"
 

Wayne Bensinger

Well-Known Member
Thanks all for the replies, I suspected I was doing something wrong and new the answer would be here somewhere.

Ed, you mentioned you don't use this material anymore, partly because of this problem, can you clue me into something that can give the same results but cuts better? Thanks

Wayne
 

EdCaffreyMS

"The Montana Bladesmith"
I prefer and use 416 or 410. Both work far better then 300 series SS, and finish MUCH easier/better. The only issue I've come across with either is that when using 410 for bolsters, and using 410 pins, it's sometime difficult to "blend" the pins in where they aren't visible. I have to believe that there is a slight difference in the makeup of 410 barstock and 410 pins.....even when you buy them from the same source(s).... most of the time the pin stock appears very slightly darker then the actual bolster/stock.
 
I drill 3/32 holes in 304ss with a cobalt drll. Use a sharp one with steady pressure and some oil. I use a slow drill speed of 480 rpm and steady pressure to keep the bit cutting steady. If I start to feel any chatter at all, clear the hole and continue drilling. I find the sharp cobalt bits work very well. Just my two cents worth.
 

Rick Weaver

Well-Known Member
One Arkansas knife maker uses 303 stainless exclusively for his guards but anneals it before use because he uses a slitting saw to make his guard slots. Mr. Dozier advised me that 416 stainless needed to be heat treated or it had the potential to rust.
 

Self Made Knives

Well-Known Member
I've use 300 series SS for bolsters and one of the reasons is what Ed mentioned. I had a hard time finding pin stock that would blend with 400 series. The 300 seems to blend perfectly everytime. I usually drill as others describe, without much trouble. But, where 300 drives me crazy is on the milling machine! I have horrible results milling it.
 

Drew Riley

Well-Known Member
Ah yes, 3xx stainless. I've machined quite a bit of 316 for some industrial washing machine parts where I work, and it certainly plays havoc on cutters and drill bits. Unfortunately, it's the best option for corrosion resistance vs price when you're working around industrial chemicals and solvents in an almost continually wet environment.
Once that first little spot work hardens, you're playing a losing battle with a drill bit. Recently, I've found some "high temperature cobalt" bits from McMaster Carr that I like for the stuff. You still have to mind your feeds and speeds, but I seem to get a lot more (and a lot cleaner) holes per bit. I also add just a wee bit of Moly-Dee cutting fluid to the end of the bit, though probably any sticky, sulfur based oil will help. Don't bother with the cheap, thin stuff that you'll find in the tap and drill section of most of the big box stores. You might have some luck with the pipe tapping fluid over in the plumbing section, as that stuff will tend to stick a little better, but most of all, you've just gotta be careful on feed and speed. Start with a sharp bit, clear chips often, and be deliberate with your pressure (though not overly so).
 

JMoran

Member
303 is free machining stainless steel, it shouldn't be confused with all of the other 300 series stainless steels that are difficult to machine. 303 was commonly called "screw machine stock" because it was used to make threaded parts on high speed screw machines. It's the SS that was designed to be cut.

John
 
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