HELP :(

King_Gorilla · **on:** October 29, 2019, 03:46:03 AM

For over a year now I have had my main MT mod project on hold because I cannot get anything to drill through hardened steel. (particularly knife steel)

I have drilled through a number of different metals for a number of different reasons with very few problems to speak of, but knife steel has got me beat! I have a decent Craftsman drill press which I have set as slow as it will go. I have read through forums, spoken to people at a local makerspace, and I lost count of how many youtube videos I have watched.

I've burned through HSS bits,

Home Depot cobalt bits, and tonight I just tried an expensive cobalt bit from a contractor supply store. They assured me that "our cobalt bits are WAY better than what you will find at big box stores." No progress. On each of these bits I have tried a variety of lube. dot 3, WD-40, I even tried water because someone on youtube swore by it.

The two things I have not tried yet. Last year, gerleatherberman said that he had success with a "harbor freight carbide glass bit." And another youtube video had a guy that said high end masonry bits would actually go through hardened steel better than cobalt, or tungsten.

I wanted to ask around here before trying either of these options because they both seem like an odd idea. (since neither of those bits were made to cut metal in the first place)

ANY SUGGESTIONS WOULD BE VERY WELCOME

BClogic · **Reply #1 on:** October 29, 2019, 04:16:41 AM

The only luck I’ve had drilling the hardened steel was to start small and work up. Using plenty of oil (3n1, JB80), going slow, touching up bits while having plenty of bits on hand. I’ve never drilled into a knife and when I had to drill into hardened steel it was broken tap removal where I could weld a nut on. So I can’t say with confidence it will work with your project, But I hope it might help.

Sent from my iPhone using Tapatalk

Aloha · **Reply #2 on:** October 29, 2019, 05:42:46 AM

Wow thats some tuff steel. With all you've tried I'd suggest trying gerleatherbermans suggestion. I used a diamond bit when I drilled thru a vic scissor pivot to enlarge it. It was slow and as mentioned it was gradual as far as opening up the hole. I used a variable speed dremil clone.

Good luck.

AimlessWanderer · **Reply #3 on:** October 29, 2019, 02:35:27 PM

If you have a drill press, I'd be tempted to go for a couple of solid carbide bits, and bump the speed back up a bit. Wear eye protection. Still use a lubricant.

What diameter, hardness, and thickness are we talking about?

Afterthought - if you're opening up an existing hole rather than drilling from solid, I'd be tempted use a solid carbide slot drill. Align using a regular twist drill if you want to keep the same centre, but switch to the slot drill for cutting

King_Gorilla · **Reply #4 on:** October 31, 2019, 02:09:12 AM

Thanks,

I'll let you know how things turn out.

gerleatherberman · **Reply #5 on:** October 31, 2019, 03:37:18 AM

I still stand behind the glass drilling carbide coated harbor freight bits as the cheapest and quickest method.

You have one more issue now that you've burned up some cobalts bits in the drilling attempts. The metal is hardened(work hardening) a bit more than it was when you started. The contractor bit might have worked before, but you'll need carbide or diamond to get through that sucker now.
I still use the same set of carbides that I had bought originally, and they still work. I do use a drill press on slow and oil to drill through. Patience and a hand drill should work well too.
Haven't tried water, and probably won't as long as I have oil/penetrating fluid available.

The hardest metal I've drilled through was 420HC. I don't know how the cheap bits would work with anything harder yet.

Only downside of the HF carbide coated bits is that the size options are limited.

Best of luck, KG!

King_Gorilla · **Reply #6 on:** November 10, 2019, 07:21:47 AM

Quote from: gerleatherberman on October 31, 2019, 03:37:18 AM

I still stand behind the glass drilling carbide coated harbor freight bits as the cheapest and quickest method.

You have one more issue now that you've burned up some cobalts bits in the drilling attempts. The metal is hardened(work hardening) a bit more than it was when you started. The contractor bit might have worked before, but you'll need carbide or diamond to get through that sucker now.
I still use the same set of carbides that I had bought originally, and they still work. I do use a drill press on slow and oil to drill through. Patience and a hand drill should work well too.
Haven't tried water, and probably won't as long as I have oil/penetrating fluid available.

The hardest metal I've drilled through was 420HC. I don't know how the cheap bits would work with anything harder yet.

Only downside of the HF carbide coated bits is that the size options are limited.

Best of luck, KG!

WOW!!!

I never should have doubted you. I went to Harbor Freight, bought 2 different sets of masonry bits, and the carbide glass bits you suggested. As you mentioned, they dont have a lot of sizes to choose from. I needed 5/32, and the glass bits were only 1/8 and 3/16 and larger. So I started with a 5/32 masonry bit. It chewed in but stopped digging after a bit. (so close

) So I put the 1/8 glass bit on and it dug right in. Slowly but surely, I got all the way through. After I had a hole, the 5/32 masonry bit was just strong enough to widen the hole to the right diameter. (but it was a struggle)

I am so surprised that after everything I have messed with, it was a glass bit made it through hardened knife steel!

Thanks again, gerleatherberman

If you come to Vegas anytime soon I'll buy you a drink.

Aloha · **Reply #7 on:** November 10, 2019, 03:20:26 PM

Glad it worked out.

gerleatherberman · **Reply #8 on:** November 12, 2019, 07:16:10 AM

Quote from: King_Gorilla on November 10, 2019, 07:21:47 AM

WOW!!!

I never should have doubted you. I went to Harbor Freight, bought 2 different sets of masonry bits, and the carbide glass bits you suggested. As you mentioned, they dont have a lot of sizes to choose from. I needed 5/32, and the glass bits were only 1/8 and 3/16 and larger. So I started with a 5/32 masonry bit. It chewed in but stopped digging after a bit. (so close ) So I put the 1/8 glass bit on and it dug right in. Slowly but surely, I got all the way through. After I had a hole, the 5/32 masonry bit was just strong enough to widen the hole to the right diameter. (but it was a struggle)

I am so surprised that after everything I have messed with, it was a glass bit made it through hardened knife steel!

Thanks again, gerleatherberman If you come to Vegas anytime soon I'll buy you a drink.

You're certainly welcome! Glad it worked out well for you!

Will take you up on that drink when in Vegas.

SteveC · **Reply #9 on:** November 12, 2019, 03:25:17 PM

Late to the party but yes, glass/tile bit work very well, I used one on a diamond file mod.

I found the quad tip type to be extremely effective.

King_Gorilla · **Reply #10 on:** November 14, 2019, 06:55:45 AM

Quote from: SteveC on November 12, 2019, 03:25:17 PM

Late to the party but yes, glass/tile bit work very well, I used one on a diamond file mod.

I found the quad tip type to be extremely effective.

Whoa!

Where did you find that? I can see how that would be more effective. I broke a couple of the bits that I was using already.

Mike 56 · **Reply #11 on:** November 21, 2019, 01:34:27 PM

I have only drilled SAK steel, not anything harder the glass and concrete bits work well. I have a few carbide bits for drilling rifle receivers for scope mounts. They work really good. The Dewalt drill bits marked 4X work well.
51

Simyo · **Reply #12 on:** November 21, 2019, 08:53:50 PM

I have to drill out sak tools for pivots and I use the dremel tungsten carbide cutter #9903. It cuts through the steel no problem you just have to manage the heat.

IvanDrago · **Reply #13 on:** November 26, 2019, 10:10:49 PM

In the case of hardened steel I usually use cheap masonry drills but before use I sharp them to the angle similar as in cobalt drills. Works surprisingly well.

Dutch_Tooler · **Reply #14 on:** November 27, 2019, 01:38:33 PM

Also you often need to reduce the footprint of the tungsten carbide insert in those bits as the size indication is often very approximate (the cheaper the bit was, the more approximate) - grind away the sides carefully until you hit the exact width.

IvanDrago · **Reply #15 on:** November 27, 2019, 07:08:00 PM

Quote from: Dutch_Tooler on November 27, 2019, 01:38:33 PM

grind away the sides carefully until you hit the exact width.

exactly so!

PTRSAK · **Reply #16 on:** November 30, 2019, 07:05:41 AM

Search eBay for solid carbide drill bit

example https://www.ebay.com/itm/KLOT-10pcs-Solid-Carbide-Drill-Bit-3-6mm-6-0mm-2-Flute-Straight-Shank-Twist-K10/322442415613?

if uou look around you can get from under 1mm up to 13mm in 0,1mm increments

spudley112 · **Reply #17 on:** December 01, 2019, 01:17:34 AM

Mike 56 · **Reply #18 on:** December 03, 2019, 06:03:12 AM

Crain Cutter sells double-sided 1/8 and 3/16 carbide bits for drilling terrazzo floors to install tack strip. https://www.craintools.com/carpet/other/tack-strip-tools/223 You can buy them at any flooring supply in the US and probably around the world.

Time22 · **Reply #19 on:** January 13, 2020, 06:59:08 PM

Quote from: Simyo on November 21, 2019, 08:53:50 PM

I have to drill out sak tools for pivots and I use the dremel tungsten carbide cutter #9903. It cuts through the steel no problem you just have to manage the heat.

Would you explain your process more?