Lots of Holes to Drill

I need to drill about 60 3/8 holes through 3/16th mild steel. I have tried a carbide tipped drill (after a 1/8th pilot hole), using medium speed, 30W Quaker State, on a drill press and only get about 3 holes before the bit is dull.

HD has cobalt... would that be better? I have also seen carbide end mills 3 for $30 on eBay ??

Please recommend a technique, and supplier for getting these holes done...

Thanks, Jeff

Reply to
Jeff Klein
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Something's not adding up here. You should be able to do tons of holes in mild steel with a standard drill bit. Maybe just touch up the drill every 25 or 50 holes.

Is it definitely mild steel and not some mystery metal? Just in case it is a material that work hardens, try a few holes at low rpm and high feed.

Are you getting things hot enough for the oil to smoke? Do you here a vibrating sound when drilling? Look at the dull drill bit. Has it chipped out? Or, has it burned and rounded the outside edge? I'm not sure I have a specific answer here, but there's a lot of other gurus on this NG.

I don't have an rpm readout on my drill press, but I think I run about 300 to 500 rpm for this drill size on steel. I'd hand feed for downforce, and let up on the pressure just as the bit starts to go through. Just a thought, maybe you're chipping the drill when you bust through on the first hole, then burning it up on the second.

I wouldn't use a pilot hole for 3/8". Do it in one shot. For "fabrication" accuracy, center punch the spot to drill to keep the drill from wondering. For "machinist" accuracy, spot drill each hole location first ( bet you don't need this)


Reply to
Karl Townsend

Try something besides engine oil. I prefer using that sulphur thread cutting oil, but I'm sure everyone has their favorites.

Jim Kovar Vulcan, Mi

Reply to
Jim Kovar

What kind of carbide tipped drill? Are you sure it's not for masonry? As Karl stated, you should be able to get a lot of holes out of any reasonable quality drill bit, with no pilot hole required.

Reply to

Skip the 1/8 pilot drilled hole. Invest in a spot drill to spot the locations after center punching. Get the cobalt drill you are asking about, and run it about 1300 RPM. (approx. 125 SFM). For infrequent drilling projects wd-40 works well as a lubricant. Spray into a small can/jar and then apply with brush.

Basically your 1/8 pilot is causing the larger drill to self destruct in the 'thin' material.

Reply to

I would expect at least 60 holes from a quality HSS steel bit. Some people don't give the drill enough pressure and tend to spin and burn the drill tip (more noticeable with a portable drill motor); but then there are those who put so much pressure on the bit that they stall the drill.

There's a happy medium out there somewhere, where the chips come up like continuous curls that may turn a little bit blue after they're out..

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Keep the whole world singing. . . . DanG

have tried a

speed, 30W

end mills 3

holes done...

Reply to

"Jeff Klein" wrote in news:Jhxbc.5682$ snipped-for-privacy@twister.southeast.rr.com:

In order to save your bits, I recommend you add more steps to your drilling. 1/8" then 1/4" then the 3/8". You should get many more than 3 holes even with the 1/8 to 3/8 jump. Are you hand drilling/drill press/milling machine?

Reply to

60 3/8" holes in 1/8" mild?

Plain old good quality HSS bit should do it easily. I use Rapid Tap, Mystic Metal Mover, etc. for cutting fluid. Plain 'ol WD-40 works pretty good, and WELCO 1620 welding anti-spatter works suprisingly well. The WELCO also removes magic marker like crazy. High sulfur cutting oil works great, I just don't like the mess.

Want to do some serious drilling on your holes?

Get the following: 3/8" bit, machine screw length, 135 degree split point, TiN coated. Available from J&L, Enco, McMaster, MSC, and probably any decent industrial supplier in your area. I get small quantities from my local Fastenal store, just because he's really close. Figure on paying $2-$3 for one bit. That should be all you need for 60 holes, and the darned thing will look new when you are finished..


Reply to
Bill Marrs

Do not use a carbide tipped masonry drill for this. It is not clear from your post but I thought that was a possibility. The 1/8 inch pilot hole is a good aproach. Select the correct SFPM for the 3/8 drill. Offhand I would say you want to be turning fairly slow, a couple of hundred rpm at most.

Do not use engine oil, or any other kind of lube oil as a cutting fluid. The pipe thread cutting oil sold at HD is a much better choice.


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Reply to
jim rozen

Are you using a hand drill? If so, you will get better performance no matter what if you use a drill press or better yet, a mill.

If it's at all possible, think about punching these holes. You can punch them a whole lot faster than you can lay them out and centerpunch them using an ironworker. For 3/8" holes in 3/16" mild steel you should use a 3/8" punch and a 13/32" die.

Punching beats the snot out of drilling. I do it whenever I can now.


Jeff Kle> I need to drill about 60 3/8 holes through 3/16th mild steel. I have tried a

Reply to
Grant Erwin

Do NOT use motor oil. Motor oil is formulated to *prevent* metal to metal contact, drilling *requires* metal to metal contact at the cutting edges of the bit. Use a cutting oil such as the black sulphurized oil sold anywhere pipe is threaded, or use kerosene (WD40), or even water. Use plenty. The major purpose of cutting fluids is to cool the bit so it won't lose its temper. The bit needs to be *flooded* with a constant flow of coolant.

Do NOT use a carbide tipped bit. Those are designed to drill non-ferrous materials, such as concrete, not for mild steel. Any good quality HSS bit should be suitable for drilling mild steel.

Do NOT be a sissy about drilling the hole. Put some real downforce on the handle. The bit needs this to work properly. You should be getting spiral chips *all the time that the bit is touching the work*. If you aren't, you're just heating up and dulling the bit to no good purpose.

I normally would not use a pilot hole when drilling 3/8 mild, just pull on that drill press handle and power through. But if your press is particularly wimpy, a pilot hole will ease the job. Be wary, however, that you're more likely to get chatter and chip the bit if you use a pilot hole.


Reply to
Gary Coffman

That's pretty much what I was going to say. Just want to add, GET RID OF THE MOTOR OIL!

You would be better to go dry if that is all you have for oil. As has been said, low rpm and don't be a panty waist, get into the cut and stay there. 60 is not a lot of holes, should be able to do hundreds even without cutting oil or coolant.


Reply to

I used to drill Japanese motorcycle brake disks back when they were a solid disk. I found that a COBALT bit, no pilot hole, at approx. 300rpm with a strong downfeed worked the best. No coolant was used and the bit would last for 100s of holes. BTW, most of the disks were some sort of stainless alloy and from 4 to 8mm thickness. Watch out for those looooooong spiral chips, though!

Rex the Wrench

Jeff Kle> I need to drill about 60 3/8 holes through 3/16th mild steel. I have tried a

Reply to
Rex the Wrench

Jeff Get a good quality split point 3/8" drill and use CUTTING oil not automotive engine oil. Forget about making a pilot hole. A good oil is the old reliable 'black oil' used for cutting pipe threads as it has some sulfur and chlorine compounds that do the job.


Reply to
J.R. Williams

Lose the motor oil first. Get some decent cutting oil from a local machinist supply or hardware store.

I just drilled 38 holes in 1/2" mild steel bars for a project that I'm working on, and did it with 1 bit. A good quality 135 degree split point TiN coated 3/8 bit, and it's as sharp now as when I started. I bought the bit at Home Depot.

I wouldn't bother with the pilot hole either, just center punch the hole to get the bit started with no wobble.

My .02. James Walsh Jr. Jigsaw Custom Fabricating

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Reply to
James Walsh Jr.

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