Tip for drilling through hardened steel

Here's a tip for drilling through hardened steel, and I mean the stuff that the best quality drill bits can't make a mark in.

I bought a worm drive wiper for my Avenger and opened it up, I found that the degree of swing was adjustable by inserting the linkage arm into holes that are spaced further and further from the center of the gear, however the degree maxed out at 120, so I decide to drill another one further out to try and get closer to 170 to clean both sides of the windshield. I attempted it with every bit I could get my hands on including a center drill from my lathe, barley made a mark in it. I took it to the machine shop here and he said he couldn't drill it, but a special carbide drill (not the ones made from carbide) but a 2 flute carbide headed one may work.

Well I went to the internet and started reading, somewhere I read that you could use a masonry bit, so off to Canadian Tire and $2.50 later, I tried the masonry bit in the drill press and........ whammo, cut through like a hot knife through butter !!! Amazing !! I am still amazed as this stuff was HARD ! Like I said, the best drills barely made a mark and burned out the bit right away.

So save some money and try your masonry bits when the going gets hard !

It does work ,just watch your speed/feed rates.I have not tried it on glass but I've heard it works on that also.

In my 30+years as a mechanic, I have drilled some EXTREMELY hard steel as you described. The best way I have found was to first, use a very small bit (1/8th or less) and drill a pilot hole. Then step up two sizes at at time to the final bore you want. Doing all of this with slow speed and moderate pressure, and cutting oil on the bit. HSS bits worked fine, but I prefer cobalt bits. They work alot better on stainless. Just remember to keep the speed down, and the pressure slightly up. (Approx 30-45 rpm for stainless)

Yeah, that's how I attempted it at first, but a 1/16th bit would only wander and put a shine on it. A friend of mine used to be the Worth rep and had a set of cobalt bits that he had used to drill stuff other guys couldn't so i tried those too, they made a tiny little mark, like I had center punched it. I could not punch it first or allow too much heat to build as the steel was attatched to a plastic drive gear and the plastic would crack or melt.
The masonry bit and some cutting oil was the ticket.

Besides good bits, it helps to have one thats ground to cut all the way to the center of the drill's web, otherwise you're trying to push metal out of the way, under the tip of the bit.

Quote:

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Originally Posted by Roger S

Besides good bits, it helps to have one thats ground to cut all the way to the center of the drill's web, otherwise you're trying to push metal out of the way, under the tip of the bit.

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Roger, these are otherwise known as a split point.

carbide end mill works tooo . robbie

RHC - Rockwell Hardness C

HSS Drill Bits - Work well up to the 50ish RHC
Drill - Mild steel, Some tool steel, Some Spring Steel
No Drill - Hard Plate, Anti Drill Plate, 404c Stainless Steel
Pro - Good in Hand Drills and most drilling applications
Con - Has limitations in hardened steels

Cobalt - Works up to 58ish RHC
Drill - Mild Steel, Some Spring Steel, Some Tool Steel
No Drill - Hard Plate, Anti Drill Plate, 440C Stainless Steel
Pro - Good for hand drills and most drilling applications
Con - Has limits with hardened steel

Carbide Tipped - Will drill almost any steel, Hard, Stainless or Mild.
Pro - Drills all steel
Con- Blunt tip requires extreme pressure to produce cuttings. Drill bit is hard to start on all steels.

Diamond Coated Drill Bit - Cuts on most steels(Not Hard Plate) just not for long.
Pro - Will Drill most steels (Not Hard Plate)
Con - Cutting stops quickly after diamond grit has warn off, Then behaves like HSS bit

Solid Carbide Drill Bit - Cuts all steels.
Pro - Sharpened points wont "walk" like carbide tipped bit. Cuts all steel
Con - Sharp tip and fine edges can chip easily and ruin drill bit. Not for hand drills. Expensive!

For more information enter “The Ultimate Guide To Drill Bits” ____ Tube video into your favorite search engine and watch the video.

2 most common mistake guys make with drilling is turning the bit too fast and making a pilot hole then stepping up to a too small of bit size. Another is when the drill isn't cutting try to puss harder and go faster, this is called work hardening and ounce work hardened it's wayyy harder to cut. Theirs drill speed charts and I'm sure you can google that, when drilling a pilot hole should be about the same size as the web in your desired finished hole bit size. Way too meany guys try to step up 4 or 5 bits to get the their desired hole size and all your doing is looking for broken corners off the bit and with no corner the drill will not cut! I worked for years in a machine shop and owned one for a time and I seen allot of work hardened stuff where someone tried to drill harder material without success and I would use the cheapo masonry bit as Number1cas said above to brake the hardened surface then a good quality cobalt to finish. Can't blame the guy for hardening the steel, he didn't know what he didn't know!!

Here is a good homestead trick, or old indian trick as we call it in Alaska. I use some aviation permatex in stead of cutting oil. Works good everytime and cleans up with iso-propyl alcohol. Lets you drill straight thru spring steel without a pilot hole. // RR