Drilling hardened steel

harrymole

harrymole

Joined
Sep 1, 2004
Messages
377
I have a hardend 440c blade that I need to make the pivot hole bigger. Can you and if so what type of drill bit do I need? Thanks.:D
 
Hi-Roc or carbide spade bits. Drill undersized, and ream to size (carbide reamer). Be prepared to pay because these bits can get expensive. Good luck!
 
The carbides are expensive and they are also brittle tending to shatter if you use them wrong. Be very careful to not try to push the drill in faster than it can move out material. Also, when the bit is just about to make the exit on the other side of where you are drilling. I use a flat piece of scrap steel under the blade to help keep the bit from breaking as it exits and it helps if the blade can be clamped down to your table on the drill press. Usually this problem of shattering is greatly reduced when drilling out an existing hole but it can still happen.

STR
 
Would it be easier just to use the reamer to enlarge the hole rather than drilling it? It is just going up a 1/16 or 1/8".
 
You'll need the drill. Before drilling it out you need to make sure there is a pivot pin in the diameter you intend to drill it to. Otherwise you will be in a jam with a good blade that won't mount to a body properly.

STR
 
That is the problem now, the previous pin was a rivet type and had come loose allowing alot of blade play. I drilled out the rivet and found out it is not a standard size hole for an adjustable pivot pin. So I have to make the hole a tad bigger. Next question will I need to keep it cool and where can I find one of these bits? Thanks.
 
Jantz supply. 1-800-351-8900. I'd opt for getting an adjustable pivot pin in stainless from them as well as the drill so you only have one shipping charge. I've used the pivot they sell quite a bit in my folders and really like it. I have also upgraded many Spydercos as well as other knives by adding this adjustable pivot to the FRN models that had pins. I like the look of the ones with a screw head on both sides better but I've had less trouble with the single screw head type as far as screws loosening up goes. I've never had to use loctite on one of these from Jantz.

Order a #HP625 stainless folder pivot pin with the 1/4" head for $2.50 and a 3/16 carbide # TD612 for $17.95 and that should be all you'll need. Most of the time the pin slides in but you can use the same carbide to ream it out the hair it might or might not need doing it this way. 90% of the time I don't even need to put the reamer in my press using these from Jantz.

The only way I see you needing anything else is if you have to shorten both the pivot barrel and the screw to fit your folder or recess the heads into a hardened bolster. Most of the time a good cobalt drill will work on liners and bolsters though. You just need a 1/4" drill bit to get the head and the non screw side to recess. Then in the event that you do need to shorten the length of the pivot you can mark it in place on the folder and then grind it down using a bench grinder or sander. Just take your time and make sure you have a good grip on it. You might want to drill a hole in a piece of brass or some other scrap of metal and pop the pivot in it to help hold it better when sanding it down.

STR
 
you can use m35 (hss contain cobalt )or call super high speed steel drill bit.
carbide is rather expensive.
i know this because i am invoving those business-hardmetal
 
In my experience using a cobalt on a hardened steel blade 56Rc or higher is just going to heat it up and probably discolor the blade as well as burn out the drill bit. I've tried those and they work for some applications but only on things like the liners, bolsters of stainless and stainless pocket clips that are Rc45 or so. Get the carbide anytime you are planning to drill out a hardened blade that is above the hardness of the rest of the knife. The blade is a completely different league over say a 410 stainless liner that has a max hardness of 45 Rockwell.

STR
 
I wouldn't recommend it, but there are some fairly inexpensive carbide tipped multi-purpose bits that are made for use on things other than masonary, I found some at home depot, I think they were Skil or Vermont American.
 
I believe Wayne Goddard, or one of the other "Blade" magazine writers recommends masonry bits for hardened steel.I have not tried them.
Bill
 
I've tried that masonry bit trick and they are a compromise in my opinion. They have carbide tips but lets say you have a pivot pin with a 3/16" barrel. You don't want to drill the pivot hole in the blade with a 3/16" masonry bit. Why? Because if you look at it and measure it it actually drills a bigger hole than 3/16". Masonry bits are all oversized when it comes to the hole they drill out.

STR
 
Use coolant, and don't overheat the blade. Drilling properly should not overheat the blade. Even if it did, the small area around the pivot would not matter.
Bill
 
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