How do you drill a hole in hardened steel?

I want to bolt some sweeps onto the tynes of a landscape rake that I'm no using, but I cannot seem to be able to even drill a 1/8 guide hole. I want a 3/8 hole to fit a plough bolt through. Any ideas?
Thanks

(quoted from post at 12:51:33 05/29/18) I want to bolt some sweeps onto the tynes of a landscape rake that I'm no using, but I cannot seem to be able to even drill a 1/8 guide hole. I want a 3/8 hole to fit a plough bolt through. Any ideas?
Thanks

Click to expand...

Sharp bit on slow speed with cutting oil. If you go fast it will heat the bit and dual it rapidly. I would start with a 1/4 or 3/8.

A carbide bit. Masonary ones are a cheap easy way to get a carbide bit. May not work for many holes though ? I have used them in the past for a one shot deal.

carbide

OllieJ,

I wil double that remark, slow and then even slower with a ample supply of a drill lubricant. I use 80/90 weight oil, because it has sulfur in it and that's what you want.

D.

Plasma cutter or a torch?

I'd try Cobalt drill bits first before heating up the metal with a plasma cutter or torch

If you can take the part off, use a drill press or mill.

You need lots of down pressure, way more than a hand drill can apply.

Slow speed with cobalt or HSS drill, and cutting oil. Carbide is better, especially if you have to use a wood drill press, which won't go slow enough for cobalt or HHS. Solid carbide bits are very expensive and brittle. The part needs to be clamped down or the bit will break instantly. You might get by with carbide tipped masonry bits, maybe...

A plasma torch will cut it if the tyne is wide enough to dissipate the heat. You can make a circle template to clamp on the tyne. Put the plasma torch inside the template hole, practice on a piece of scrap. The template will get the hole where you want it, get in and out quick before the heat spreads.

Heat the part you want to drill, it will
anneal it and actually soften it. Been a
long time, can't remember the temperature
range anymore. I welded a new spade nose
cutting edge in a Cat 994 quarry bucket.
This was a 22 yard bucket that was about 18
feet wide. That cutting edge was about 18"
wide at the ends and about 3 feet wide in
the center where the spade nose was, and
about 4" thick. It did not have any of the
holes drilled in it for all of the bolt on
wear plates used in quarry use. Seems like
I had to drill around 50 or 60 1-1/8" holes
all the way through that cutting edge, and
any of you that have had to drill, cut, or
weld a -quality- cutting edge know what I'm
talking about. Anyhow, after marking where
all of the holes needed to be, I had to
heat them using an infrared thermometer and
a heat crayon. Took a little while, but I
figured it out for how long and hot I had
to heat both sides of the cutting edge and
then how long I had to let it set before
the center of the edge was the temp I
needed it to be to anneal it. Before doing
this, the Hougen bits would hardly scratch
it. After annealing it, well, I won't say
it cut like butter, but they actually
drilled out pretty nice.

I am not sure which piece of steel you want to drill the holes, the rake or the plow? One way to spot anneal is to find some carbon arc rods. The pointed tip will produce resistance heat at the metal-carbon junction. I don't remember how much voltage is required. The temperature needs to be at least 600-800 F. It should be a dull red in the dark. Let it cool slowly.

There are also carbon/graphite gouging electrodes, but they need air to blow the molten metal away. This can be dangerous if you don't know how to do it.

use a masonry drill bit like mike down below in the post said did it many times myself. it will work better if you can do it in a drill press or mill.

Lots of good advice. While drilling you need pressure and SLOW speed.
A tip I learned years ago from a drill bit salesman. As you start to
drill put a couple of drops of straight antifreeze on the area where
you are going to drill. Add a couple more drops every five seconds or
so. It really does work ! Slick as can be.

I drilled ports in a stainless steel propeller once. Took lots of pressure, sharp bit, high quality oil made for
the task and slow speed......lots of pressure.

(quoted from post at 21:51:33 05/29/18) I want to bolt some sweeps onto the tynes of a landscape rake that I'm no using, but I cannot seem to be able to even drill a 1/8 guide hole. I want a 3/8 hole to fit a plough bolt through. Any ideas?
Thanks

Click to expand...

Reverse a drill in the press & "drill" at a high speed with a lot of downpressure until the end of the drill & the work glow red. Don't let the drill weld itself to the work! You have now spot annealed the work. Use the drill in the normal way & drill the hole.
Masonry bits also work, but will need sharpening to cut steel for which you will need a "green grit" or diamond wheel. (Ordinary wheels wont touch the carbide insert)