Drilling hardened steel- Help please

[Pherdie]

I am attempting to drill a tool holder which is used with a BXA series tool post holder.

I need to drill four 17/64 holes (approximately 1-1.5" in depth) through the tool holder and then counter sink the holes for the use of socket head screws. A yet to be constructed series of lathe accessories will be later attached to the tool holder. Rigidity of the tool holder, as related to the attached accessory, is the driving factor in using the socket head screws.

The tool holder steel is HARD, very hard and laughs off high speed drills. A check of the Enco catalog shows a number of carbide drills, but none is recommended for steel. I figure annealing is pretty much out of the picture and I have no access to EDM. I also tried some small carbide end mills which cut the metal, but make poor drills.


Any ideas????

[airsmith282]

have you tried to heat the object in question wiht a tourch cherry red hot then let cool on it own works for me with hardend tool steel and other steels that have been case hardened

[Pherdie]

As mentioned in my post, I don't really think annealing the part would be a good idea. Although I have a torch w/ a rosebud, I'm concerned that heating the part hot enough to anneal it might cause the part to warp, as well as ruin the ground surfaces.

[wierdscience]

If you need just a clearence hole look a good quality masonary drill bit.Moderate speed and some coolant they will drill through a leaf spring.

[TGTool]

It doesn't sound like a good proposition, particularly compared to just machining up what you need from fresh (soft) steel.

But if you're intent on doing it, look for die drills at the industrial supply places. They are a variety of a carbide spade bit designed for drilling hardened steel. You may be in luck in having your current tool holder block only case hardened. A carbide end mill will then produce the counterbores.

I've successfully used centercutting carbide end mills to drill case hardened gears so it can be done. Not fun, but doable.

[Pherdie]

weirdscience: Thanks for the tip. Even with lots of oil and making sure not to cook the bit, the masonry bit was gone after one hole. I might get several more masonry bits for sacrificial purposes and then clean up with a (to be purchased) die drill.

TGTool: I did start out with center cutting mills as drills but the two I had died during cross drilling threaded holes (I guess no amount of care can overcome an issue like that). The holder is hardened throughout so your suggestion of using die drills will be taken and an order to Enco will go out Tuesday.

Yes, perhaps making a new holder out of mild steel would have been a better choice, but in the challenge of punching the holes through hardened steel was the possibility of gaining some knowledge as to dealing with hardened metals ( yes, the lesson may have been don't do that again!!).

Thanks for your responses!!

[J. R. Williams]

Spend your time wisely and make a new holder and heat treat if necessary. All the hard steel drilling does for you is increase your frustration level.

JRW

[deltaenterprizes]

How do you plan to tap it?

[Pherdie]

Tapping not included..........

[Rich Carlstedt]

Well I have drilled through 60 + RC steel with a Masonary bit
and I did it by going as high a speed as the drill press would run, and
put the part in a small vice and then the whole thing in a pail of water.
The water is needed to keep the silver solder of the masonary bit from softening and letting the carbide break off.
lots of pressure helps ! almost stall the motor
Rich

[juergenwt]

Do this:
First check what kind of steel you have.
You can do this by:
Spark it - you need to be experienced -or
take a hammer and strike it with a corner of the hammer.
If there is a dent-you have a low carbon steel case hardened.
If not-it is made from tool steel and hardened all the way through.
Now, if case hardened take a carbide drill. Put in vertical mill with the part in a vice. Use a 5/16 carbide drill and with medium speed-forget about "as fast as possible"-drill to the full dia. to cut away the case. You can now use a regular HSS drill to drill the 17/64 hole. It will break out on the bottom. If not all the way use the 5/16 carbide to open it up. Do the same for the c'sink part.
If tool steel and hardened all the way through:
Get a 17/64 carbide spade drill or something close to it.
Again put the drill in a vertical mill and the part in a vise.
Set a stop.
At medium speed turn down the stop a few thousands at a time and push the drill to the stop. Turn down again-drill, lower-drill and on and on.
It goes very fast. An inch deep should not take you more than two or three minutes.
Don't try to work without a stop. You will break the carbide drill at the end.
Do not use a drill press!!!

[SmoggyTurnip]

Do this:
Don't try to work without a stop. You will break the carbide drill at the end.
Do not use a drill press!!!

So how do you finish the hole?

[loosewatches]

First a question How Hard Is It?



Ok, I'm probably going to get chiseled for saying this, but I drill hardened steels (Hardox 450-and up and dilladur) at work on occasion, on a TOS w100a horizontal boring mill. These things are above 650-700 Brinell and up (60-64R ?) I do it with drills that I grind by hand, when I can't get an indexable drill. (Crappy tooling at our shop)

Anyway, it can be done. Go slower than 500 rpm. The Hardox site recommends 500rpm for 10 mm holes. Start even at 350 and work up. If it doesn't cut at low speed, it won't cut at high speed either.

If you've got a feed (you didn't say did you?) stick it around .004 and use lots of coolant. (I hope I converted that right. I'm in Austria, and I'd be running about .1-.08mm per rev.) It may be agonizingly slow to start, but it will work.

Here's the Second question, though......What shape is your bit in? Can you sharpen it By Hand? I mean, you won't get far with a "Factory Finish" on it. It NEEDS to be facet ground. Here's an article, the only one I've found online on facet grinding:

http://www.mmsonline.com/article.aspx?id=14722

I'll tell you, people in almost every shop I've worked in, on two continents, have laughed at the way I grind drills. I even take drills fresh from "the grinding shop" and re-grind them. The look different and they work different. You'll get much less rubbing, less friction and more cutting, which is exactly what you need for the hard stuff.

I don't know what angles to say you should grind at....I've forgotten. I just do it by eye. (roar of laughter from the audience) If you still haven't gotten them holes drilled tomorrow, I'll post some numbers after work. If that doesn't work....well, we'll burn that bridge later.

oh yeah, be sure to center drill first, too.
Hope that helps

-loose