drilling heat tempered steel

Southern Ray

Well-known Member
can these be drilled?
I am repairing my dad's old disk.
I have plenty of the front halves but the rear halves are kinda worn.
John Deere wants over $100.00 for each.
I want to drill and tap for a grease fitting and use these for the back half.
Lowes's and Home Depot bits won't touch it.
I went to a machine shop store and bought a tough bit, so I thought.
It just barely makes a bite.
a238075.jpg
 
Heat it until it is red hot and bury it in a pail of dry wood ashes. The next day you can drill & tap it. Then heat it to red again & drop it in a pail of used oil. The way it is, if you get it drilled you will break a tap trying to thread it.
 
A good way to test for hardness is with a file. If a file will cut it, it is soft enough to machine with standard tooling. If the file just skips across, it's hard.

If it is hardened steel (which that doesn't look to be) you can drill it with a carbide masonry bit. Run it slow, lots of down pressure, use cutting oil. But, no way to tap it.

If you can find the right size drill and grease fitting combo, you can use a drive in type fitting.
 
I use to drill hardned steel in the shop and we did as was suggested. Run the bit slow flood with oil and we use to resharpen the bit so that it had a flatter angle. I do not remember offhand what the angle was. And oh yes sometimes we did a lot of cussing LOL
 
As you have a drill press, you're probably best off with an actual carbide drill rather than a carbide-tipped masonry drill. A masonry drill will certainly work in a pinch, but you're going to want something fairly precise if you're tapping and most masonry drill are, of course, designed for masonry, not steel. As a rough price guide, a 1/4" carbide drill runs under $20 from Enco (which is now officially fully back under MSC's umbrella but their website still works the same as normal, at least for now) and should drill as many holes as you're apt to need, though you'll also need a carbide tap and those will run more than the drill, in addition to being fragile. Still, it can be done, it just takes a steady hand and a light touch--if your tapping technique involves hauling on the tap handle like you're steering a windjammer in a typhoon you're better off paying someone to do it.
 
Try the way to get it a bit softer first. Now my tip is when you are ready to drill keep it as slow as you can go on your drill press and use straight out of the bottle Anti-freeze. It really works! Just keep putting a few drops on it every few seconds. Another thing to look into are "drive fittings". No need to tap. Just make a damn straight hole, no margin for error, and you whack them in with a hammer. I use them all over the place and they are very handy on castings like that. You can get those fittings at NAPA. Also ebay. There are five or six sizes. Tiny is 1/8 and the biggest I have ever used was 1/2. Mostly use 3/16. Go look up 162203891072 and look at the picture. Those are not threads but are barbs like an air hose fitting. Give them a try. Get back to us.
 
I doubt that housing is "hardened steel", probably some sort of chilled cast iron, HARD on the outside and tough on the inside, and the LAST thing I would want to do would be to muck around trying to heat it and soften it, if you DID succeed in softening it a bit, I don't think you can re-temper it like steel, as a couple of the replies suggest doing.


Was the "better bit" you bought a "cobalt bit"? I would be VERY surprised if a slow-turning cobalt bit with oil being drizzled on it would not drill it.
 
I've come across this sort of problem before and never really did come up with a solution .
I have had one idea though and would welcome any comment , it might even help Ray .
I wondered if heating the area very locally with a welding rod would work ? I am thinking that if you could strike an arc on the exact spot the hole needs to be drilled on and weld enough to get the spot really hot . Surely this would soften hardened metal to some extent .
 
I would look into pressed in zerk fittings because when you do get it drilled you probably won't be able to tap it.
 
Sure looks like cast iron to me. A good drill bit, and some coolant, it will dril and tap pretty easily.
 
ivor from uk here and just putting my 2 cents worth
I am thinking there are no grease points for a reason and that is when dust from discing mixes with grease it becomes a very good grinding paste
 
Drill a pilot hole then go to full size.
That stuff looks like it should not be hard to drill. Might have gotten a poorly sharpened bit.
BTW Adding a grease fitting will only work if the bearing will accept grease.
 
ocassionaly we run into cars here at the shop that have boron steel in them. disk blades are also boron steel. we use a special bit to drill the spot welds out. (bmw uses boron steel in some of their structural panels. ) here is a link to the bit, i believe it is a tungsten bit. they work well. they are expensive.
poke here
 
My suggestion, dremel tool grinding bit such as one for chain saw sharpening, then fit for grease fitting.
Good luck,j
 
Just a caution not to get too macho. I was trying to drill into a hardened shaft some years ago and forced it so much that the table mounting casting broke to pieces. I built a wooden table for it, but just not the same. I just found another drill press at a garage sale last week and gave the broken one to my son.
 
Possibly it's become work hardened, either through normal use or your unsuccessful attempts to drill it.

If it's hardened, you should be able to anneal only the spot you want to drill by using a brazing tip on your acetylene torch to heat a small spot cherry red. Then let it cool slowly.

Drill the annealed spot with a FRESH COBALT bit, making sure you have the drill motor slowed down to the appropriate speed. Use oil and keep enough pressure on it so that you get a pair of continuous shavings off the bit. If you're just getting chips, you'll wear out the drill bit almost instantly.

Most hardware stores carry cobalt bits. I think you can even find them at Lowes & HD.
 
I was wondering how to drill tempered steel for the pivot on the front axle of my NAA. It is 1/4" steel with a 1/2" hole in it. Due to abuse by others it needed to be drilled out to 5/8". After reading the replies on this topic I bought a 5/8" masonry bit, set the drill press to the slowest speed, about 250 rpm, filled the 1/2" hole with cutting oil and it took about 10 minutes to cut the hole. The masonry bit is fine. Thank you for the question and all of the responses.

Harvey
 

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