Choosing my first set of drill bits...

I

Iron Filing

Registered
Registered
Joined
Feb 25, 2023
Messages
38
Hello,

Background:
Recently I was trying to drill through some steel from a lawn mower blade as I was making a small metal part out of it. The bits I have been using up to this point are from lowes (TiN coated), harborfreight (TiN coated), and whatever hand-me-downs (non-coated) I have laying around. They are capable of drilling at least some forms of stainless steel. But for whatever reason, maybe I accidentally hardened the steel when grinding it to size with the bench grinder, they cannot penetrate the lawn mower blade steel. After they were dulled out, the drill bits were resharpened with a drill doctor sharpener and they penetrated even less than before. The procedure was attempted again before giving up. I need a good set of drill bits...

After doing some reading on the matter I'm left at a loss due to conflicting and missing information. Please give me a hand as I don't want to invest heavily in a nice set of bits only to find out that I got the wrong things.




Currently, you can choose between 118 and 135 degree bits. Supposedly, 118 degree bits are what you should use on steels, but other sources say that they cause a lot of vibration due to the minimalistic contact between the bit and the work piece leading to all manner of problems (and then recommend their drill bit products to you based on this info with YT videos showing a difference). Further recommending 135 degree bits is the fact that pretty much every cobalt bit I can find is a 135 degree bit.

What's going on? Is a 135 degree bit only preferable with cobalt or what?

Next you have to consider coating. There are some very nice coatings out there, like AlTiN, but once they wear off, then what? You have to buy new bits. Which recommends to me that I should get bits made of some tough steel to begin with. But then the question comes up, which, if any, alloys would work well uncoated? Even cobalt bits are coated based on my searches. Aggravating the problem is that not even name brands, in their official catalogs, list the steels/alloys that they're using. I'm talking Chicago-Latrobe, CLE-LINE, Drillco, Triumph Twist Drill, and others.

Do I have to call up each company to verify that I'm getting a decent product or what?

Thanks
 
I've had good luck with US made HSS bits. I'm sure others will chime in with online suppliers but I've always been able to get decent sets at my local hardware store. You may have to ask specifically but I usually get un-branded sets that seem to work great.

Of course you can always go with McMaster-Carr.

www.mcmaster.com

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.
www.mcmaster.com www.mcmaster.com

I've also had good luck with using stepped bits which you can get cheap from Harbor Freight.

www.harborfreight.com

Titanium-Coated High-Speed Steel Step Bit Set, 2-Piece

Amazing deals on this Titanium-Coated Hss Step Bit, 2Pc at Harbor Freight. Quality tools & low prices.
www.harborfreight.com www.harborfreight.com

John
 
Not to sound testy, but I know there are many good places to buy from. McMaster is one, as is Zoro, or Graiger, or Northerntool, etc. I'm asking specifically about how to pick out a good set vs. saying, "Good enough" and hitting the "buy" button.
 
Maybe it wasn't clear from my initial post, but I'd like to get something that will last if I'm going to be spending more than $100 on bits. Many of these sets go up into the range of $1,000. And although I'd rather not spend that much, I'd still want to purchase something that lasts.
 
Iron Filing said:
Hello,

Background:
Recently I was trying to drill through some steel from a lawn mower blade as I was making a small metal part out of it. The bits I have been using up to this point are from lowes (TiN coated), harborfreight (TiN coated), and whatever hand-me-downs (non-coated) I have laying around. They are capable of drilling at least some forms of stainless steel. But for whatever reason, maybe I accidentally hardened the steel when grinding it to size with the bench grinder, they cannot penetrate the lawn mower blade steel. After they were dulled out, the drill bits were resharpened with a drill doctor sharpener and they penetrated even less than before. The procedure was attempted again before giving up. I need a good set of drill bits...

After doing some reading on the matter I'm left at a loss due to conflicting and missing information. Please give me a hand as I don't want to invest heavily in a nice set of bits only to find out that I got the wrong things.




Currently, you can choose between 118 and 135 degree bits. Supposedly, 118 degree bits are what you should use on steels, but other sources say that they cause a lot of vibration due to the minimalistic contact between the bit and the work piece leading to all manner of problems (and then recommend their drill bit products to you based on this info with YT videos showing a difference). Further recommending 135 degree bits is the fact that pretty much every cobalt bit I can find is a 135 degree bit.

What's going on? Is a 135 degree bit only preferable with cobalt or what?

Next you have to consider coating. There are some very nice coatings out there, like AlTiN, but once they wear off, then what? You have to buy new bits. Which recommends to me that I should get bits made of some tough steel to begin with. But then the question comes up, which, if any, alloys would work well uncoated? Even cobalt bits are coated based on my searches. Aggravating the problem is that not even name brands, in their official catalogs, list the steels/alloys that they're using. I'm talking Chicago-Latrobe, CLE-LINE, Drillco, Triumph Twist Drill, and others.

Do I have to call up each company to verify that I'm getting a decent product or what?

Thanks
Click to expand...
Cobalt.... I bought a set of the HF coated bits, the middle of the road quality wise. The set I bought has the numbered, Lettered and standard bit; then as I use them when I do one in I replace it with a good cobalt bit from a machinist tool supply.
 
verbotenwhisky said:
Cobalt.... I bought a set of the HF coated bits, the middle of the road quality wise. The set I bought has the numbered, Lettered and standard bit; then as I use them when I do one in I replace it with a good cobalt bit.
Click to expand...
Interesting strategy. I like it. I'm not sure I'd use it, but I like it.
 
verbotenwhisky said:
Cobalt.... I bought a set of the HF coated bits, the middle of the road quality wise. The set I bought has the numbered, Lettered and standard bit; then as I use them when I do one in I replace it with a good cobalt bit from a machinist tool supply.
Click to expand...
Good strategy.

We recently got a new vendor at work and they recommended their cobalt tooling. I can be hard on tooling at times and these endmills and drills are worlds apart from what we have been using for decades.

It costs more, but for the amount of extra life you get out of a single sharpening its well worth it.
 
A mower blade is going to be some tough material, likely something like high carbon plow steel. It's going to be rough going to start with, then it will work harden from the dulled bit and become impossible. Take a torch to the hole you started and heat it up to cherry red (or as close as you can), then try again. Use cutting oil and push the drill hard to keep it cutting. Also, run about 1/2 the recommended speed for mild steel.
 
Last edited:
MrWhoopee said:
A mower blade is going to be some tough material, likely something like high carbon plow steel. It's going to be rough going to start with, then it will work harden from the dulled bit and become impossible. Take a torch to the hole you started and heat it up to cherry red (or as close as you can), then try again. Use cutting oil and push the drill hard to keep it cutting. Also, run about 1/2 the recommended speed for mild steel.
Click to expand...
If it helps, I was running 1/8th inch bits at 550rpm on a drill press at an unknown feedrate. I just pushed at what I thought was moderate pressure.
EDIT: When I say moderate pressure, I mean where it feels like you're getting somewhere, but not too quickly.
 
You must log in or register to reply here.
Back
Top