Jump to content
Sign in to follow this  
Greg R

Drill bits

Recommended Posts

What kind of drill bits do you guys use? I have cobalt bits and they are usually good for 1 or 2 holes then they are toast

Share this post


Link to post
Share on other sites

Cobalt bits should last for a little while, with cutting oil and low speed. Carbide bits last longer but are brittle, have to be careful

Edited by Doug Crawford

Share this post


Link to post
Share on other sites

Regular HSS. Keep the speed down, use fluid, and lastly, learn to sharpen drill bits.

 

Share this post


Link to post
Share on other sites

I'll echo on the low speed and use of cutting fluid and I'll add good constant pressure.  One of the easiest ways to dull a drill bit is by letting it spin on the steel without cutting.  Also, try to remember to drill your holes before hardening the blade whenever possible. I use cobalt as well, my 1/8" drill bit probably has 30 holes to it's credit and is still in good shape.

  • Like 1

Share this post


Link to post
Share on other sites

I drill at low speed and use cutting oil but I still seem to be using more and more bits. What brand bits do you use?

Share this post


Link to post
Share on other sites

Finally! A topic I know something about!  I assume you're talking about just drilling small diameter holes (less than 1/2" dia). Cobalt will drill just about ANYTHING but keep in mind that being that HARD means that once you get into small diameters they can be frustratingly brittle, and are prone to snapping. I have a contractor supply store, and we sell A TON of drill bits in a month, and 90% of fabricators and steel workers just buy a good quality (made in USA) HSS drill bit. The ones we sell are NOMO surface treated (Nitride on margin only) 135 degree split point HSS bits. You can find a lot of gold coloured titanium coated bits out there, we find those are usually 'gimmicky' compared to a good quality HSS bit. Whatever you use, as stated, you should always mind the RPMs and certainly use a coolant or, even better, a cutting wax when drilling deeper than 1/8". I don't like to recommend specific brands, because even the brand we sell has an offering of good USA made HSS bits as well as cheaper pacific-rim line to appeal to all markets.  You get what you pay for.  If you're paying less than $2 or $3 for a 1/4" bit, then chances are you're just getting spiral twist drills. I will recommend a split-point bit though. It won't wander the same as regular bits.

Edited by GPrimmer

Share this post


Link to post
Share on other sites

Also if you don’t have one, this is the best $4 I’ve spent at harbor freight

 

https://m.harborfreight.com/spring-loaded-center-punch-621.html?utm_referrer=direct%2Fnot provided

Share this post


Link to post
Share on other sites
5 hours ago, Greg R said:

I drill at low speed and use cutting oil but I still seem to be using more and more bits. What brand bits do you use?

I assume you are drilling before HT??  I wanted to put brass bolsters on my last blade as an afterthought. After a half hour with a brand new bit I gave up.

Share this post


Link to post
Share on other sites

yes I am drilling before heat treat. however right now I am working on a piece of 1095 that seems to be inpenetrable. brand new cobalt bit drilled half way through and just stopped cant find any bit that will finish this hole even another brand new one of the exact same bit.

Share this post


Link to post
Share on other sites

To sound like Mr. Picky here, "Heat treating" can aid in drilling holes in other than air hardening steels generally. If you reduce the size of the carbides through thermal cycling and then heat to a dull red heat basically, it can make the steel easier to drill. It is after "hardening" by quenching that drilling becomes difficult. 

Thermal cycling, normalizing (Bladesmiths anneal), generally all heats before quenching = "Heat treating"

Quenching = "hardening"

Oven heating after quench = "tempering".

Share this post


Link to post
Share on other sites

Try taking the steel up to decalescence and letting it cool to black a couple of times then take it up just to where you see a bit of red starting and let it cool. 

Share this post


Link to post
Share on other sites

That's a good point Vern, I can't believe I didn't remember that.  I had a ton of troubles drilling pin holes when I would try to "anneal" my blades by letting them cool in the forge.  I thought it would make them softer and easier to drill, turns out it creates sheets of carbide within the structure of the steel and eats drill bits like I eat M&M's!  I switched to just normalizing/thermal cycling my blades after forging and have had no issues since.

Share this post


Link to post
Share on other sites
8 minutes ago, Vern Wimmer said:

Thermal cycling, normalizing (Bladesmiths anneal), generally all heats before quenching = "Heat treating"

Quenching = "hardening"

Oven heating after quench = "tempering".

I'll one-up you on pickiness.  All of that is heat treating.  When you heat the metal to affect it (e.g. change microstructure, not for reasons like making it ductile for forging) you are heat treating.  ;)

Share this post


Link to post
Share on other sites

I actually normalized the steel by heating it up then letting it cool back down to room temp. then realized I forgot to drill the holes so Im now trying to do that before I quench. is that the wrong way to normalize it? did I accidentally harden it?

image.jpg

Share this post


Link to post
Share on other sites
22 minutes ago, Jerrod Miller said:

I'll one-up you on pickiness.  All of that is heat treating.  When you heat the metal to affect it (e.g. change microstructure, not for reasons like making it ductile for forging) you are heat treating.  ;)

Indeed, but if you do not make distinctions........ There is a big differences between some actions.

Share this post


Link to post
Share on other sites
17 minutes ago, Kreg said:

I always thought quenching = HT....sounds like I should be using the term quenching from now on.

In the interest of technical honesty I have to admit that I technically misrepresent quenching on a regular basis. If you cut to the finest line "quenching"a carbon steel in a liquid medium does not, technically, harden the steel. The steel hardens later on, relatively, BECAUSE it was quenched thereby passing quickly over/thru the pearlite stage.

A blade is still pliable when it comes out of the quench until it reaches the point that the austenite starts to convert to martensite.

Share this post


Link to post
Share on other sites

I finally got the holes drilled. After trying a number of different cobalt bits I found this and it went through it like butter.

 

B103CF61-EB8B-41F9-9DFA-2863DF6F57AD.jpeg

Share this post


Link to post
Share on other sites

By chance is your drill a "hammer drill"? (option to impact as it drills) May seem like a stupid thing to ask, but I get that all the time from customers who forget to simply switch to 'rotary-only' mode for this kind of task. That bit lends itself well to drilling in impact mode in concrete/brick because of the carbide tip, but you certainly wouldn't want to use impact mode for drilling steel.

Edited by GPrimmer

Share this post


Link to post
Share on other sites

Ooh, those look nice!  Gotta get a few in certain sizes...

Share this post


Link to post
Share on other sites
37 minutes ago, Alan Longmire said:

Ooh, those look nice!  Gotta get a few in certain sizes...

I've been very happy with them. I'm not cranking out a ton of blades, but that said, I typically place only one order a year; two each in 1/8" and 3/16".

Oh, and I keep my press set at the lowest speed; 760 RPM.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×
×
  • Create New...