Drilling hardened steel revisited

R

retiredff

Member
Hello,

I posted here almost 2 years ago as I anticipated making my own knives. Well, it didn't happen as things changed (wifes job went to mexico). So, I'm trying again.

I have searched here, google and I have found conflicting answers. I have a belt sander/grinder that will work for now and some wood working hand tools. I will purchase "blade kits" or finished blades minusthe scales. These blades are hardened and from my reading, are DIFFICULT to drill. I don't mean to imply I will drill every knife I buy, but I will modify a few for different pins, rivets etc. I doubt if I will get to the point in the next few years where I will grind my own blades and purchase the needed heat treat equipment (space limits) grinders/sanders etc.

My next purchase will be a drill press. I have looked at many and have settled on the Grizzly 12 speed MAINLY for the speed settings of 140-3050. From my searches, (here are the conflicts), some say SLOW speed, oil, carbide drill is needed, others have different ways to deal with this like spot annealing. So, my question is: Most drill presses slowest speed is 600+- rpm. For MY NEEDS is 600 slow enough with a carbide bit or should I opt for the Grizzly and the lowest speed of 140 rpm? I would guess from reading here the holes I will drill will be 1/8" - 5/16". It might be a new hole or enlarge an existing hole.

NOTE: I have woodworking experience and NONE for steel.

Thanks

Tony
 
Thanks Joe. I was leaning that way even though the Grizzly is more expensive. I have been watching craigslist, and have yet to see a Grizzly anything for sale.
 
If using carbide, you want to run them just about as fast as the drill press will go. Turning carbide at slower speeds on steel/metals will result in chipped cutting edges and/or broken bits. HSS should be turned the slowest, Cobalt a bit faster, and carbide the fastest. Some coolant such as "cool tool" or a quality cutting oil will make your life much easier.... the bits will cut much smoother and last MUCH longer.

Something that I think worth mentioning....if you have a bit sharpening disability (like I do) :) ...consider purchasing a Drill Doctor drill bit sharpener.... my Mrs. got me one for Christmas about a dozen years ago, and I am now on my 4th one (I've worn them out from so much use)...and it has saved me literally thousands of dollars in drill bits over that time. (not hard to believe when you consider some of the big (1/2"+) carbide bits I use in the shop are $100+ each)
 
Ed,
OK, so for my needs (drilling hardened existing or new holes), run the drill press 2500 rpm+ with cutting oil. What type of pressure? Heavy/pulsed or slow?

I remember reading a post of yours on the "drill doctor". I will look into one.

Thanks
 
The "way" you drill is going to depend on just how hard the steel is......if something is fully hardened, I have the best success with "tap" or "pulse" drilling.....drill just a bit, then take the bit out to clear the chips, and just keep doing that until you make it through. The biggest chance of chipping or breaking a bit is just about the time the coolant/oil is just about gone, and the bit "grabs" non-lubed material. Also, enlarging any hole whether in soft are hard steel runs an increased risk of a bit "catching" and chipping/breaking. Flood cooling is ideal, but creates a mess.....I generally use a typical household "spray" bottle, with water soluble cutting oil/fluid.....and keep the drill site "wet". Its seems to work well for me. For deep or large holes I have a "squeeze" bottle that I keep the hole flooded with non-diluted cutting oil/fluid.
 
I use the same procedures as Ed including the fastest speed when using carbide bits. In fact I may have picked them up from him in a forum long ago. I feel I'm getting good results, with these steps and points to use. Frank
 
Another tip is to use a scrap steel plate under the blade. That keeps the bit from snagging and spinning the blade as it punches through that last bit. You kniw the trick...when drilling and the blade catches as you are punching through... Yeah you drill a bit more but it saves bits and potential injuries.
 
Bosch makes some hammer drill masonry bits that will punch through hardened steel - go slow and use oil.
 
From the reply's, I don't need the Grizzly's slow speeds of 140 rpm. So any drill press will work with a speed over 2500+-.

Thanks for the reply's. I'll spend the $$$$$ saved on carbide bits.

Tony
 
I'm not so sure about "go really slow" or "go really fast". Carbide and hard steel has a relatively narrow chip load window, and I think moderate speeds will help you fall into that window better.

For all practical purposes, carbide will not be effected by heat, so there is no reason to go really slow, you can't burn it up.

It is very chippy and sensitive to chatter, so it may be unwise to go really fast unless you have a good rigid setup. An advantage to carbide and high speeds is there is an SFM that, once you cross, there is less chance of chip welding. But it will be had to get there with a drill in a home setup without other issues cropping up.

There are three primary reasons to use carbide
1: hard (can cut hard things and wears less)
2: stiff (less deflection, more accurate, better finish)
3: heat resistance (higher SFM possible = higher material removal rate, more productivity)

For this application, I'd say only the first really applies.

I would suggest an RPM fast enough to reduce risk of over feeding (probably over 500 RPM) but slow enough to avoid chatter caused by machine harmonics and a less than rigid setup (probably under 1500). This is for hard steel and carbide and a 1/4" drill.

For drilling just a couple holes in something no thicker than a tang, I'm of the opinion that oil or coolant shouldn't really be necessary. Though a sacrificial part under the work piece is very helpful in a manual setup like this when using carbide to help prevent you from wiping out the corners.
 
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One thing that may go with out saying but I'll say it anyway. Put a bit in the press that is the size of the existing hole, run the bit down into the hole to locate the part and clamp it down. Then raise the bit and change to the new size. With the part clamped and the use of lube you will reduce chatter.

Chatter chips carbide bits.

Good Luck
James
 
Bush Monkey said:
Bosch makes some hammer drill masonry bits that will punch through hardened steel - go slow and use oil.
Click to expand...

These bits are very likley carbide tipped (as most quality masonry bits are) and should be treated the same as carbide bits, I.E., used with relatively fast speeds.

That being said, while the bit should be turning fast, the drilling/plunging motion of the bit should remain relatively slow, with plenty of cutting fluid.
 
retiredff said:
From the reply's, I don't need the Grizzly's slow speeds of 140 rpm. So any drill press will work with a speed over 2500+-.

Thanks for the reply's. I'll spend the $$$$$ saved on carbide bits.

Tony
Click to expand...

While the slow speeds are not necessary for drilling hardened steel with carbide bits, you're probably gonna want the slower speeds for drilling soft steel with regular bits as well as for other tasks/bits that require slower speeds.
 
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