I have been fighting w/ trying to drill some 7/16 holes in 1/4in steel plate. I have tried pilot holes and all I keep doing is burning up drill bits. I've go the drill press set as slow as it will go and am using "decent" drill bits. What am I missing???

Flame Away...

some kind of lubricant or cutting fluid? I really don't know.

I tried that. Would work for a mm or 2 and then smoke... think its time to but a cutting torch.

I think he meant to say to use ALOT of cutting fluid.
and you will make stuff smoke.
Friction makes heat.
Heat + and fuel (cutting oil) makes smoke.

I destroyed 4 1/2" drill bits...
The I bought a drill doctor...
It paid for itself in about 20 minutes.

¼ inch Mild steel? 7/16 should not be a problem. Yes pilot drill the holes 100% with a smaller drill bit, then swap over to the larger drill bit. If it keeps having and issue your bit may be real dull.

Mark

I've got the Drill Press set at 620RPM - I just looked at the chart and it recommends 1100RPM. Isn't 1100 RPM too fast?

hhhmm...I just drilled some 5/8" holes thru a pair of tacked together 3/8" flat steel plates (3/4" total) ....no cutting fluid, no pilot hole, no nuthin. Just taking my time and not rushing it...

oh, and my bits were just sharpened with my Drill Doctor....I couldn't live without that thing!!

Have you resharpened the bits? I had pretty good luck hand sharpening. What size pilot are you attempting?

Slow is usually better. 1100 should be a max speed. I drilled holes last night in 1/4 with a regular drill, did three steps and it cut through just fine.

Actually the formula for determining RPM is "SFM"*4/Drill Diameter. The "Surface Speed per Minute" largly depends on the type of material cutting. It you have steel, then I would us 30-40 as the "Surface Speed per Minute", so you work the math. Roughly this means you should run at about 50-70 RPM. Hope I remember the formula right, but I think that is correct. So the smaller the drill, the faster you should spin it. Most peeps don't know that, but try it. There are two purposes of the pilot hole. 1. It gives the bigger drill bit the ability to dig into the material. Here is why: If you look at a drill bit, the end has a flat section on it. This is called the land and no cutting happens here. As you go to smaller bits, the land decreases and this is why you typically us a small bit to drill a pilot hole. Even the small bit has a small land, but it will cut much easier than a larger bit. 2. Gives a good path for the bigger bit to travel...and won't allow the bigger bit to "Walk" on the material you are cutting.

Phew...long lesson in machining. I used to TA in college about this stuff, so I know a little, but I am sure I am missing a lot. Someone correct me if I am wrong on the SFPM value. Couldn't remember it exactly.

I experienced burning bits when trying to drill through spring-steel...
Do you know the origin of your 1/4 stock?

just a thought,
manny 72fj40 in SF

I experienced burning bits when trying to drill through spring-steel...
Do you know the origin of your 1/4 stock?



I am curious about this aswell. My first thought is your bits are dull . I sharpen my bits on a normal bench top grinder (it take some skill but is not that difficult). Buy a new pilot bit , and the size that you were trying to end up with. If those dont do the trick the first time somethings up with the steel stock. Even using the wrong speed should not give you the hassles you are speaking of. 1/4" is/should be a cake walk for you even with a hand drill.
HTH
Richard

I recently purchased a new 9/16" bit from Home Despot to drill 14 holes in 3/8" steel using a ~3/16 pilot hole. This, along with my other crude shop tools allowed me to make the mounting for my 8274 in the CCOT HFS bumper. I drilled the 8 corners with the 9/16" to radius them some before cutting the straight sections with a combo of sabre saw blades and angle grinder. I ate up a number of Bosch metal blades before I discovered how nicely one can cut 3/8" with a steady hand on the angle grinder. Fluid used with the drill was tap and die cutting fluid. 'Had to resharpen the bit in the Drill Doctor when I got to the 12th hole...... then ... cut like new. Used my ancient Allied 1/2" "D"-handle electric hand drill. New bits should drill many holes in 1/4" steel with proper pilot/rpm/fluid/pressure.

John Sherwood '79 FJ-40
Charlotte, NC TLCA Upstate Cruisers

1100 is not that fast if you are using a drill press. At work we have a very large (like 8 ft tall) old cincinati drill press it only has two speeds. One is about 1200 and the other is about 120 rpms. Anything under 3/4 we use the high speed and anything over 1" we use the slow speed (in between is really just a judgement call depending on how sharp the bit is and if you want to re-grind it afterwards) If you are able to hold the piece steady (solid setup) and you are applying constant pressure (not forcing it just constant pressure) let the bit do the work it should work fine on the higher setting. Drill doctors are nice but learning how to grind bits helps even more because you can change the profile of the cutting edge depending on the application (bottoming, line drilling, ect.) Lubrication is also helpful but it will usually smoke pretty good and smell nice at that speed we use tap magic and it works pretty well. Hope that helps you out some.

ben

Damn, I use around 150-250 RPM on our press, and drilled 1/2 plate with 5/8" holes no problem. started small, went to 3/8", then 1/2", then the big one.

Lot of excellent high-tech responses here on the science of drilling a hole. However, I believe your particular problem is much simpler: Ya gotta be smarter than the damn metal. :flipoff2: :flipoff2:

I experienced burning bits when trying to drill through spring-steel...
Do you know the origin of your 1/4 stock?

just a thought,
manny 72fj40 in SF

No, Still pretty inexperienced when it comes to metal. I went to a metal distributor "Fulton Supply" and bought 1/4 inch by 4 1/2 by 10' "Steel Plate". It cost $13.00 - so I'm assuming it's just mild steel - unless the yard guy pulled the wrong stuff. How can I tell the difference?

I am curious about this aswell. My first thought is your bits are dull . I sharpen my bits on a normal bench top grinder (it take some skill but is not that difficult). Buy a new pilot bit , and the size that you were trying to end up with. If those dont do the trick the first time somethings up with the steel stock. Even using the wrong speed should not give you the hassles you are speaking of. 1/4" is/should be a cake walk for you even with a hand drill.
HTH
Richard

I went through 4-5 bits starting at below 1/4 and up to 1/2. All with the same results. The interesting thing is that it would get to a point and then just stop - no matter how much pressure. I'm starting to think that I need to try the sharpening process. The outer edge of the bit would turn blue and that was it...

Lot of excellent high-tech responses here on the science of drilling a hole. However, I believe your particular problem is much simpler: Ya gotta be smarter than the damn metal. :flipoff2: :flipoff2:

Yeah, I should have expected and valuable response like that - from a Damn Yankee :flipoff2: :flipoff2: :flipoff2:

See you week after next :rolleyes:

The local metal/machine shop had a couple different types of plate, one of which is supposedly some really tough stuff. It was about 2x as much as the mild steel. Maybe they grabbed some of that? I can't remember what it's called but it supposed to be harder to cut and machine.

Drilling holes in 1/4" mild steel should be easy on a drill press, even with somewhat dull bits.

Your drill bits are dull, it's that simple. You didn't get spring steel and it doesn't matter that much if it's a higher grade plate steel or not.

Even with a slow speed, too much pressure and/or not enough cutting oil will dull the bit. To make matters worse, if the metal gets hot enough from pressing on it with a dull bit, it will harden a layer right where you're trying to drill. The blueing of the bits you describe is a good indicator.

FWIW, I bought a Drill Doctor cause I learned by doing exactly what you're going through.

Phil

FWIW, I bought a Drill Doctor cause I learned by doing exactly what you're going through.

Phil

Got one today - will give it a try tomorrow evening and let you know the results...

[QUOTE=Rascal] - from a Damn Yankee :flipoff2: :flipoff2: :flipoff2:


BTW: Ain't no Damn Yankee no more. I escaped from NY. Now I'm a good ole' southern boy again. :D :D Working in Tampa, FL. for a little while.

i just got done with soa and made my own front plates had no problem with drilling holes in them. lots of lube i used 3-1 oil 5/8 holes 3/8ths plate steel. smoke is good, lots of oil to cool steel and bit.

DRILL DOCTOR to the Rescue!!! :D :D :D

Got a drill doctor and cut through that 1/4 like butta.

Thanks for the info guys.

two pics of my DD sharpened bits in action....11/32 pilot hole, 9/16 and 5/8 bits, tho I don't recall how recently I sharpened them....3/8" steel

http://www.ih8mud.com/reviews/drilldoctor/dd1.jpg

http://www.ih8mud.com/reviews/drilldoctor/dd2.jpg

That is a sweet little machine :D

DRILL DOCTOR to the Rescue!!! :D :D :D


You had me wondering there for a moment.

Usually for small projects I was always grabbing scrap stuff at the local metal yard. Handy to find good size chunks of steel, aluminum, etc.

Needed a simple seal driver. Typically I grab what ever seems heavy, chuck it into the lathe... and turn to size. Started cutting, tool bit skipped across it. Tried a carbide tipped tool, new insert... nada. Cranked in a little more pressure, and it started carbide started glowing! :eek: I have no idea what that stuff is, but probably tossed into the yard by someone who couldn't cut the stuff. Oh, I just handed to a fellow home shop machinist with a comment... didn't you need some stainless steel, I picked up too much of this stuff! :flipoff2:

Tom :usa:

two pics of my DD sharpened bits in action....11/32 pilot hole, 9/16 and 5/8 bits, tho I don't recall how recently I sharpened them....3/8" steel

http://www.ih8mud.com/reviews/drilldoctor/dd1.jpg

http://www.ih8mud.com/reviews/drilldoctor/dd2.jpg

Hey Brian,

Where did you get that vise for the drill? I need one of those..

Thanks,
Charles

Harbor Freight, cheapie, like $40 for their 4-1/2"er. Comes in damn handy at times. I do wish on occasion it was wider, but for 95% of stuff, it works great.

You had me wondering there for a moment.

I have no idea what that stuff is, but probably tossed into the yard by someone who couldn't cut the stuff. Oh, I just handed to a fellow home shop machinist with a comment... didn't you need some stainless steel, I picked up too much of this stuff! :flipoff2:

Tom :usa:

There are a large number of supper metals out there. (Hastelloys, Inconel, Incoloy Nickel Alloy, etc.) I remember a job my partners and I cut for TRW (Satellites and Gov. spook stuff) where they supplied the “steel” and the part drawing. The drawing had no title block just a part number and an 800 phone number if you had any questions. Part of the quoted job was to not only send them the finished part but all the chips from the “steel”. We had to keep one of our CNC mills cleaned and dedicated to the job. They told us to cut it like Inconel but we just ate tooling ($$$$) and about the time we finished the job we had tweeked the feeds and speeds by backing the RPMs down, and increased the chip load big time.

(You always want the heat generated by the cut so stay with and exit with the chips you cut. Other wise it either goes into the part you are cutting = work hardening that then eats your tooling. And or it goes into your tooling = nuclear melt down of the tooling.)

The tooling survived 10 times longer. (Big slow bites, “Wack, wack,wack”) The floor shook and the machine sounded like it was gona blow. We had nice new Haas VF-2’s but they are not made for stuff like that! I have no idea what that “steel” was but machine #2 was not so nice IMO after that job!

Mark