Drilling holes for pins AFTER heat treat

Matthew Gregory

Matthew Gregory

Chief Executive in charge of Entertainment
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Jan 12, 2005
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Because I insist on doing everything the difficult way, I prefer to drill my pin holes after I heat treat. There are several reasons, but it creates some issues, as well. Here's why, and how I'm currently dealing with it.

I don't like being restricted to a particular material or shape. As I'm making a knife, there's occasion where I feel an element needs changing (a bump or contour in a handle needing to be eliminated, per se, or perhaps a desire to use bolsters on a knife that wasn't originally supposed to when I initially designed it). if the holes were pre-drilled, they could be in the wrong location, or even worse, be close to the right location, close enough to create mayhem when needing to relocate by a smidge. I guess I just like the idea of being able to go with the flow, as I don't make identical knives in multiples...

Previously, I'd chuck a center drilling carbide endmill into my little milling machine and put the holes where I wanted them. The dilemma stems from .125" holes not really liking to pass pin stock that's also .125". AND endmills really have no love for drilling. They do it, but they want to side cut, and that won't help here.

A little backstory, then my solution...

When I bought my mill, I was looking for good endmills, and although the big houses (MSC, McMaster-Carr, etc) all have them, my head was swimming from the sheer number of options. I have NO training in machining.

None.

Everything I've picked up has been through the kindness and patience of mentors and friends (interestingly enough, mentors usually have a way of becoming friends, too, I've found!;)).

After watching one of my brother NickWheeler's vids on milling guards, I asked him where he was getting them. Turns out Nathan the Machinist had turned him on to this place where he buys stuff called Lakeshore Carbide. I checked out their website, and sure enough - they've got darn near everything I was looking for! Digging around on their page, I noticed something else - their office is in my backyard! HA!

I ran my dilemma of post HT hole drilling past them, and they transferred me to Carl. Turns out Carl is the owner. He listened go what I was doing, asked a number of questions about what materials I work with and what my equipment was like, and made a few observations. Said I should be using a drill, rather than a center cutting endmill, as it's more efficient. He also mentioned that he didn't have any #30 (that's .128", btw) carbide drills to offer me, but that he had relationships with many other vendors (Carl and Lakeshore Carbide make all their endmills and drills, right here) and that he'd get back to me after he did some digging. Our conversation was on the Friday before the Super Bowl. At 6:45 that SAME NIGHT, Carl calls me back and says he's sourced a drill he wants me to try. WOW!!!!
Shouldn't this guy be forgetting everything until Monday or Tuesday!?!?!? Talk about customer service!!!!

So, long story short, I've been testing these drill bits and they're doing exactly what I need. I'm posting all of this because I'm wondering if there's not more guys out there like me, that wish to work a little more organically, but can't because they don't know how to put holes in hardened stock after the fact.

The ones he sent me seem to be working fine, but he's asked me to test them and see if they can't be optimized with a change in cutting geometry, etc. Also, if there's enough interest in this, he'll considermaking them in-house!

So, how do you guys deal with this?
 
I can barely get a hole through soft steel! If I need to, I use the bulldog bits which are the regorund carbide rock drill bits you see at trade shows, drill through a nicholson file and all that stuff.
 
Tell us more about the drill bits - are they regular twist drills? 118 or 135° point? Split point?
 
That's interesting, they have a knifemakeing tab on the website and solicit suggestions.

I'm curious about the drill geometry too, what is it ?
 
I just did this and used a solid carbide spade tip bit. Clamped the blade to a piece of mild steel bar as the backing. Worked without issues.

I'm also curious about what you're using.
 
Good stuff Matt. I drill all holes pre-heat-treat, so have no issues.

But do use carbide endmills and some carbide drills, will check out this company.

Thanks!
 
I'm interested. One slip In profiling and and pin holes aren't centered anymore. Have had to re drill in hardened steel a few times, always stressful. I hit it with a propane torch a couple of times but it still isn't a graceful process.
 
The specs for this particular test drill are as follows:

-Solid submicron grain carbide drill
-For materials 40 Rc and higher
-For high nickel, cobalt based and powdered metal
-Coating provides excellent heat resistance/lubricity
-Up to 40% faster than uncoated
-1.5 times the diameter optimum drilling depth
-2 str/rhc flute design provides excellent rigidity
-Live tooling recommended on lathe processes

This isn't so much of an issue with simpler steels, such as 1084 or W2, where simply throttling back the hardness with a torch will allow you to use standard drill bits, but I've been making a lot of chef's knives recently, and you're not going anywhere with a cobalt or HSS bit into RC62 AEB-L, or any other modern alloy, for that matter. I want to use a just slightly oversize hole for pins, as it provides just enough slip fit to work, as well as even afford a bit of gap for adhesive flow. That's why standard .125" drill bits don't work for me. #30 is just about perfect. I'll still use .125" into softer material, but going through the tang of a knife is perfect at .003" oversize.

I'll post a pic of the bit here in a sec...
 
I usually drill mine pre HT. However, sometimes I screw up the plunge and have to move it back to fix it. Then, my holes are off. So I had been drilling a couple of holes so I can adjust. I would love to be able to drill easier after HT. I don't have a mill, but do have a drill press. Can I still use these bits without them chipping or shattering?
 
I've been using #30 carbide bits for 1/8" pin holes for years. No matter what size hole I want, I always drill .025" - .030" undersize before H/T and then drill .003" - .004" oversize with a carbide bit after H/T. The reason I do it is so I can have good, clean, decarb free holes. I've always used the carbide bits from Jantz. They're reasonably priced and work fine for me. I hardly ever use them to drill a completely new hole but they will do it.
Having said that, I'm always open to a better tool and sources for them. Thanks for posting.
 
Well said, Darrin!





Here's the photos:

16103920694_9fda082c8c_b.jpg



16540122209_1f637280ba_b.jpg
 
Rookie25 said:
I don't have a mill, but do have a drill press. Can I still use these bits without them chipping or shattering?
Click to expand...

Good question. I'm really not sure. I can tell you, however, that I'm applying quite a bit of pressure (a LOT of pressure) at 1200 rpm to make these work. I would say it's all going to come down to how solid your vise is, how well supported your work is, and how little your drill press will flex. Any one of these things will snap a carbide bit two times fast.
 
Matt. If I decide to drill my holes pre HT in AEB-L, will I be able to do that with a cobalt or HSS bit?
 
Pre-heat treat? Yeah, no problem. Almost all steel is pretty easy to drill in its annealed state. Strangely enough, it's the simpler steels that can cause trouble (1084, 1095, etc) because they can either have strange structures in them that cause patches or hardness due to improper annealing by the mills, or they can work harden under the drill bit because of too much slipping/speed and not enough downforce.

AEB-L is really easy to work with, btw, aside from trying to drill holes in it while it's hardened. There's almost nothing in it to offer any increase in wear resistance. I don't bother to rough grind these previous to heat treat. I just profile them, heat treat them, and do all grinding in their hardened state.
 
Spot annealing is also an option and doesn't require any special drill bits. That was my sollution when I had to drill a hardened knife blade one time.

Just chuck a junk drill bit into the drill press, run it on high until the spot you want to drill turns red, let it cool, then drill the same spot with a normal drill bit.
 
Pretty sure that won't work with air-hardening steels, as they're meant to harden... In air. I suppose it might work for some of the simpler stuff, though. How do you keep the heat from getting too close to the edge? I can't imagine you getting a single spot on the knife red hot without it being a few hundred degrees an inch away from the red.
 
eyeeatingfish said:
Spot annealing is also an option and doesn't require any special drill bits. That was my sollution when I had to drill a hardened knife blade one time.

Just chuck a junk drill bit into the drill press, run it on high until the spot you want to drill turns red, let it cool, then drill the same spot with a normal drill bit.
Click to expand...

I've done this very thing on a hardened tang. But you don't let it cool, you run the drill bit on the spot until you get through it. The carbide tipped masonry bit can be used in this manner, but a 1/8" carbide tipped masonry bit will drill a slightly larger hole than .125".
 
I was told to keep the temper in a blade where you are spot heating the handle you can wrap the blade with an ice water towel or rag.
Will this actually work?
 
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