How do you drill hardened steel?

[ebinmaine 67,627]

Ask Trina and I expand our abilities working on machines or doing house and yard projects we come up on different situations for which we need new advice tools, or both.

 

 

My latest little adventure is figuring out how to drill HARDENED STEEL.

 

I bought a plow edge off of the jungle site. I need to drill seven holes in it.

I've got about a pile and a half of drill bits and every single one of them is HSS. Perfectly fine for everything we've done up until now. 

 

 

Two questions.

1. Methodology. What type of speed and pressure should I be using on the drill press? Do you start small like around 1/8" and go bigger?

 

2. What type of drill bits do you use?

 

I've read where some people use an End Mill bit with high RPM and slow downward movement. Others say that's not possible.

 

 

@OldWorkHorse Steve I figured you'd want to follow along on this one. 

 

@Stepney I'd like to hear your thoughts on this. 

 

 

[midpack 866]

2 minutes ago, ebinmaine said:

 

I've read where some people use an End Mill bit with high RPM and slow downward movement. Others say that's not possible.

 

 

 

 

That's called "hard Milling" 

Quote

The process of hard milling is very similar to normal machining; however, it requires special equipment and understanding of material hardness, machining capabilities, tooling, and tool holding devices.

 

[OldWorkHorse 3,045]

I've always had a hard time with this so this will be good info. From what I can assume u have to take the hardening out of the material and then re harden it? Somthing like drill bits are hardened steel can't drill hardened with hardened? Probly have to get a even harder drill bit. This was my guess I'll wait for the smarts   

[ri702bill 8,339]

Eric:

My son is a Locksmith and has to drill thru hardened steel plate inside  the door on safes. He goes thru about 4 NEW carbide tipped masonry bits per hole. He also uses a magnetic base drill to keep the drill bit straight and steady. As a side note - sounds like you are making holes for 3/8" bolts, right??  Start off with a 3/16" bit to go thru the plow edge and then go to the 7/16" - carbide cutting edges chip rather easily.

Bill

[wallfish 17,011]

 

[Achto 27,605]

I purchased a 1/4" Titanium-Aluminum-Nitride (TiAlN) Coated Carbide bit from here for drilling out rusted in roll pins that won't move.

 

https://www.mcmaster.com/drill-bits/material~carbide/carbide-drill-bits-11/

 

It was $35.60 for the one 1/4" drill bit.  Why was it so expensive??? Because it's worth it!! High speed low pressure and his bit will walk through a roll pin like you were drilling through aluminum. I've drilled out several pins and it still cuts like the day I bought it. One note: I never drill all the way through a roll pin. I stop about an 1/8" shy of going through and punch the last little bit out. I don't want to chance catching the last edge and have the bit snap.

[953 nut 55,321]

If you use a torch to heat the spot you intend to drill through until it is red and then let it cool you should have no problem drilling it. The rest of the piece will retain its hardness.

Edited March 9, 2021 by 953 nut
fat finger

[squonk 41,155]

I've had good luck drilling out SS screws on kitchen equipment with colbalt bits

[Pullstart 62,912]

Just drill it at your neighbors 

[TJ5208 1,824]

If you get some steel bits that should help 

[WVHillbilly520H 10,373]

From my machine shop days drilling hardened tool steels,  we used solid carbide drill bits , very expensive like @Achto said and also fragile if not use correctly (like glass will shatter) if using coolants always use it, or keep it dry use air to keep chips removed, a regular grind stone will not resharpen these has to be an aluminum oxide wheel (green) if they chip, around 750 rpm for a 1/4" bit faster for smaller slower as they get bigger, "medium" pressure and don't rush depends on hole depth how many "pecks" (plunge and retract) you should use instead of one steady all through motion, make sure your work piece is clamped securely and with sufficient space under as to not drill into the table, let the bit cool before drilling the next hole.  End Mills should not be used in a drill or drill press for hardened steels only rigid milling machines. Most drills and drill presses have to much circular run out for this (osolation). Masonry carbide tipped bits will work but the bit itself is soft and the carbide is only 1/8" at most soldered to the shank. I'm sure @lynnmor or even @Ed Kennell should know more about this than me, I'm just a "mutt" without papers who did this for a decade to pay the bills.

Edited March 9, 2021 by WVHillbilly520H

[DennisThornton 4,769]

I've seen them at several shows and brought some home.  I did break one but they are guaranteed.  

https://baddogtools.com/

[Ed Kennell 38,227]

Actually all my machining experience has been with milling of the  aluminum and manganese bronzes.    The masonry bit video was interesting.   I have a couple bits that I may try to sharpen.

[JoeM 7,874]

If the piece has holes can you drill the material you are attaching the piece to match the piece?

 

No matter what drill you use got to keep it cool with fluid, I like a good quality cutting fluid. The anneal thing might be the cheapest way to go.

 

Second word of the day Anneal

 

Annealing is a heat treatment process which alters the microstructure of a material to change its mechanical or electrical properties. Typically, in steels, annealing is used to reduce hardness, increase ductility and help eliminate internal stresses.

[lynnmor 7,308]

The question is how hard?  I would guess that your work piece is under Rc 44 and that can be drilled with a HSS bit, of course cobalt would be better.  Keep the speed down and use cutting oil, or other oil if that is what you have. Make the drill cut, either make it go or get out.

 

I didn't watch the video above, but I have used masonry drills on hard steel.  They should be run fast, just keep in mind that the carbide is silvered soldered in place and extreme heat will cause failure.  Cheap masonry drills may have little support behind the carbide and fail if pushed too hard.  Candle wax is a good lubricant for carbide drills.

 

I would use a smaller drill first, but not so small that it breaks easily.  Do not go in small steps, allow a substantial amount for the next drill.

 

You should download a speed feed chart, there are many available, some are bad and the rest are worse. 

[ebinmaine 67,627]

A lot of great information here folks. Thank you and keep it coming...

[WVHillbilly520H 10,373]

18 minutes ago, ebinmaine said:

A lot of great information here folks. Thank you and keep it coming...

Is that bar you got AR Plate? Like Lynmoor said under Rc45  but where I worked we would have to open up holes in Rc55-60 A2 A6 D2 hardened tool steels and/or machine slots that wasn't easily done with a surface grinders ... Also the shorter the bit the less flex from the start

https://www.mscdirect.com/product/details/78543972

Edited March 9, 2021 by WVHillbilly520H

[ebinmaine 67,627]

20 minutes ago, WVHillbilly520H said:

Is that bar you got AR Plate? Like Lynmoor said under Rc45  but where I worked we would have to open up holes in Rc55-60 A2 A6 D2 hardened tool steels and/or machine slots that wasn't easily done with a surface grinders ... Also the shorter the bit the less flex from the start

https://www.mscdirect.com/product/details/78543972

 

 

It's listed on the jungle site as 1055. Near as I can see on the interwebs that's equal to an RC of 60 to 66. 

 

I like the idea of heating it at the spots where I need to drill a hole but I only have a propane torch..

 

 

[OldWorkHorse 3,045]

10 minutes ago, ebinmaine said:

I only have a propane torch..

 

 

Thermite lol... 

[8ntruck 7,016]

22 minutes ago, ebinmaine said:

 

 

It's listed on the jungle site as 1055. Near as I can see on the interwebs that's equal to an RC of 60 to 66. 

 

I like the idea of heating it at the spots where I need to drill a hole but I only have a propane torch..

 

 

The actual hardness of 1055 will depend on the heat treat and tempering cycles that have been done.  The hardness on the Rockwell C scale (Rc) could be anywhere from 30 to 60.  30 to 40 is drillable, 40 to 50 can be drilled with more effort, 50 to 60 good luck.

 

Have you done a file test on your material?  If a file cuts it, you should be able to drill it.  My choice would be a carbide drill lubes with something like Tap Eze in a drill press.  A smaller pilot hole would help, maybe 1/8 to 3/16 for a final hole size of 3/8.

 

A propane torch should be able to anneal spots on material maybe 3/16 thick.  Heat to cherry red, then let cool in air - don't quench with water 'cause you will re-harden it that way.  Even better to cover the piece in ashes to cool it more slowly.

Edited March 9, 2021 by 8ntruck

[WVHillbilly520H 10,373]

16 minutes ago, ebinmaine said:

 

 

It's listed on the jungle site as 1055. Near as I can see on the interwebs that's equal to an RC of 60 to 66. 

 

I like the idea of heating it at the spots where I need to drill a hole but I only have a propane torch..

 

 

Heating it will not only draw the "temper" out of the steel but now you have introduced heat back into your drill bit doing the samething in turn ruining the bit, if trying to drill while hot,  if indeed it is 60Rc then the only real option "IMO" is the solid carbide bits or take it to a trusted machine shop.  Have you done the "file" test? Where you try to scratch the metal with a file if it gouges/scratched deep its soft enough to drill conventionally, if it just slides across without grabbing its 55Rc and above. Google the file test for metal. @8ntruck beat me too it.

Edited March 9, 2021 by WVHillbilly520H

[JoeM 7,874]

47 minutes ago, ebinmaine said:

RC of 60 to 66

 

Getting up there now, if not to critical on the fit........ torch or if you know someone with a plasma cutter?

[oliver2-44 9,761]

I made a new plow edge about 2-3 years ago.  Ideally you make square holes so you can use those countersunk head plow bolts.    OK, I like tools and I like to do as much a I can myself.  But I try to ask myself is this a one time job, or will I do it several times making purchasing a tool worth it.  I took the new and old plow edge to a welding shop that has an iron worker.  They have square hole punches and have no trouble punching through the hard material.   That is what I did for  mine. 

 

Regarding that drill bit Achto posted, I see drilling out numerous roll pins in my future.  Just might need to put that in my shopping for the next time I make an order! 

[formariz 11,987]

I have a grinding wheel that will sharpen carbide tools. I take a good quality bit such as the ones from Hilti and sharpen the carbide tips as if I was going to cut wood with it. I then use it on the drill press at a rather slow speed with substantial pressure while lubricating them with kerosene. I drill hardened plane blades this way. Some of the planes I make I have to insert a bolt through them for a specific function. They are impossible to drill though in any other way and They can not be softened in that area since that would ruin them.

[ebinmaine 67,627]

1 hour ago, JoeM said:

 

Getting up there now, if not to critical on the fit........ torch or if you know someone with a plasma cutter?

We have a friend who does work on commercial dump trucks and other rigs.

 

Been trying to get up and visit...

 

We have several things she can do for us. 

Damn pandemic got in the way this past weekend.