Question for all you machiniests

[Julio Navarro]

I' ve been building a sheet metal break out of 1x1x1/8" angle iron (I assume it's steel, not sure) but its the regular black angle shape they sell at HD.

I ran into a sudden road block that I did not anticipate...drilling a 1/2" dia hole in the angle. For some reason I cant seem to be able to drill a simple 1/2" hole. I have steel bits, cobalt bits I used a Ridgid cobalt bit and it barely made a dent. I used a Hitachi metal bit and it also just barely bit the metal. I made a 1/8" hole...no prob...1/4" no prob...3/8" no prob...but the 1/2"... nothing. I even predrilled up to the 3/8" but thats as as far as it goes, ...even RED hot the bits just turn blue and die.

Am I using the right type of bit? Can anyone recommend a type of drill bit, or brand?

I am using a 12" drill press at 3200 rpms

Any help is greatly appreciated.

[Rob Blaustein]

Not a machinist, but I have drilled through steel several times and asked machinists about it. I suspect that the pros would say you're running your DP way too fast; I think the recommended speed for steel and a 1/2" bit is something like 600 RPM. Are you using oil to lubricate--I don't think the bit should get red hot. Once the bit gets dull you end up having a very hard time. I've had good luck with the Drill Doctor, even with inexpensive bits--I just sharpen them often when drilling through steel. Hopefully the machinists will pipe in and correct me if I'm wrong.

[Barry O'Mahony]

3200 rpm!!!!!!!!!!!!!!!!!! No wonder the bits are getting red hot.

Rob is right, 600 rpm is the max for this size in steel. The piece MUST be clamped in place, and use lot's of cutting oil. Even so, it takes a bit of down pressure. Be patient.

[Stu Ablett in Tokyo Japan]

Yep, Julio, slow it down!

What I do is drill a pilot hole, it makes life much easier on the 1/2" bit, and you can more accurately place the hole as well, as the 1/2" bit is not the easiest to "place".

You got to use some sort of oil as well, there is specific oil that is for doing just this, but most anything is better than nothing. The oil for your air tools, or even WD-40 works better than dry!

I use some chain oil for my motorcycles, one I have a big can of it, two it has a long thin spray tube on it, three, it is really sticky, so it stays in place and does not go running all over the place, works for me, but it is not "Drilling" or "Cutting" oil per say.

Dude you have to clamp that sucker down, make yourself an extended table for your DP, all it has to be is some thicker plywood, say 3/4", bolted to the existing table top, use 4 carriage bolts, and some big washers on the underside, (expect to toss the plywood when it gets nasty) this way you can easily clamp something down to the edge of the plywood top, as most DP's table tops are not flat on the underside, so they are hard to clamp to.

Lastly, a little trick, when you change the belt position on the pulley, you loosen off the motor, so it moves in a bit to change the belts, when you tighten up the motor after changing the belt position, don't push the motor so far that the belts are super tight, make it just tight enough. This way if you have a catch on the drill, the belts will slip, and not send the work piece rotating around to smack into you.

Too loose and the DP won't work right, so you have to try it a few times.

Good luck!

[Bill Lewis]

I think even 600 rpm is too fast for this, but according to my machinist handbook it is ok. Just go as slow as you can, raise the bit out often to keep the heat to a minimum, use coolant (cutting oil) as others have suggested. Definately use a pilot hole, or several stepping up in size if you need to. The pilot hole should be just larger than the "starter point" on the 1/2" bit.
BTW it sounds like your 1/2" bit is now toast, but in addition to ruining the bit, you have probably locally hardened the hole you were attempting to drill. So no matter what you do, you'll likely to ruin any other bit by attempting to drill it out.

I was once in HD and I overheard a sales guy in the tool department tell a customer who wanted an explanation on the differnt drill bits, "oh, this is high speed steel, that means you can run your drill faster".

[Julio Navarro]

I half figured it was the speed, but fully knew I ws doing something foolishly wrong.

I went by the chart on the DP for metal which recommended 3200 rpms, but seeing the unanimous responce I now see that was not the way to go.

Rob, I will slow it down to 600rpms and try on a new peice, as Bill suggests, the peice is probably hardened by now.

Stu, I'll try the oil for the air tools as I have a whole pint of it. BTW, I am building the break using your design, its looking good and I should have it done tonight when I can finally make the holes for the pivot pins. I have pics I'll put up tonight. The welds arent very pretty but I dont think it will come apart any time soon (first welding ever for me)

One thing I did do right was drilling the pilot hole and clamping the peice to a BP vise which in turn is clamped to the table firmly.

Thanks all, as always a wealth of advice here.

[Jeffrey Makiel]

The advice provided above to clamp the work is important for safety reasons. When the bit (especially 1/2" dia) is completing the hole, it will try to grab the work piece and spin it. Slower speeds tend to make the 'grabbing' even worse and more powerful vs high speed. This is one sure way to break fingers or wrist if not clamped.
-Jeff

[Mike Cutler]

I half figured it was the speed, but fully knew I ws doing something foolishly wrong.

I went by the chart on the DP for metal which recommended 3200 rpms, but seeing the unanimous responce I now see that was not the way to go.

Rob, I will slow it down to 600rpms and try on a new peice, as Bill suggests, the peice is probably hardened by now.

Stu, I'll try the oil for the air tools as I have a whole pint of it. BTW, I am building the break using your design, its looking good and I should have it done tonight when I can finally make the holes for the pivot pins. I have pics I'll put up tonight. The welds arent very pretty but I dont think it will come apart any time soon (first welding ever for me)

One thing I did do right was drilling the pilot hole and clamping the peice to a BP vise which in turn is clamped to the table firmly.

Thanks all, as always a wealth of advice here.

Julio.

You are looking for a "cutting fluid". While a general purpose oil/lubricant will work, you should really get a cutting fluid. Aqua-Tap, Rapid-Tap, even Kroil, or LPS etc.. One more thing. The cutting fluid for steel is different than the cutting fluid for aluminium, have both on hand.
Good luck.

[tod evans]

julio, slooow for steel. .02 tod

[Mike Parzych]

What you're experiencing is "work hardening" of the steel - in effect "heat treating" that small area to a higher hardness. The more heat you apply by more high speed drilling, the harder it will get.

Slow speed will work.

[Tyler Howell]

As long as I have the attention of all this talent, How about the preasure used for drilling in metal.
Light even or pour on the coals:confused: :confused:

[tod evans]

As long as I have the attention of all this talent, How about the preasure used for drilling in metal.
Light even or pour on the coals:confused: :confused:

use enough pressure to make chips, the bigger the bit the more pressure...02 tod

[Jeffrey Makiel]

Caution with the cutting fluid. I have dripped cutting fluid while threading black pipe over a concrete floor. Some of the oil contacted the floor and started to eat into the concrete within 15 minutes! I don't know if this is common for all cutting oils, but the stuff I have is called Sulflo. Wear glasses and watch the drips. (And remember to clamp the work!)
-Jeff

[Bruce Page]

Julio, I suspect that you have work hardened the steel. Try drilling it from the other side at about 400/500 rpm.

Toss that drill speed chart you were using!

[Julio Navarro]

Julio.

You are looking for a "cutting fluid". While a general purpose oil/lubricant will work, you should really get a cutting fluid. Aqua-Tap, Rapid-Tap, even Kroil, or LPS etc.. One more thing. The cutting fluid for steel is different than the cutting fluid for aluminium, have both on hand.
Good luck.

Any suggestion on where I can find this fluid, Mike?


Julio, I suspect that you have work hardened the steel. Try drilling it from the other side at about 400/500 rpm.

Toss that drill speed chart you were using!

I'll be using a new peice. Consider it tossed, Bruce. I'll be looking for a machinest guide.


Caution with the cutting fluid. Wear glasses and watch the drips. (And remember to clamp the work!)
-Jeff

SOP, Jeff, thanks for the tip. It's very easy to overlook such simple procedures in heist.

As always, thanks for the advice and taking the time to give it, wish I had asked before doing.

[Cliff Rohrabacher]

I'll offer this:
1.) Heat is your enemy.
2.) Speed is not your friend when cutting steel.
3.) Any oil ( any as in any) oil is needed for drilling ( or any machining) steel. (newer use oil when cutting cast iron) Oil is a perfect cutting fluid. You can purchase specialty oils and fluids but any oil at all - even used crank case oil - is just fine and works great.
4.) As stated earlier you have work hardened the metal.
5.) drilling the metal after it's hardened may be a reall issue
6.) Heat the affected area with a torch and let it cool slowly. Do not heat it red hot just hotter than 400-Def-F.

You have what's called "hot roll" steel. It's a rather cummy steel with "hot spots" and "hard spots." That doesn't mean you can't machine it, it just means you gotta work carefully so as not to wreck your tooling.

[Julio Navarro]

Thanks Cliff.

Can the drill bits be saved. All have blued at the end, can they be sharpened or did I ruin them beyond help?

I will forsaken the steel I was using and just cut two more peices to properly drill this time using all the advice given.

[Julio Navarro]

I want to take this opportunity to correct the spelling to machinists.

My spelling is not what it should be.

[Tyler Howell]

Great thread, Thanks for the info.;)

[Mike Cutler]

Julio.

I don't know what stores are available in your area. To purchase cutting fluids here, I can go to a few specialty machine shops, and some old time hardware stores.
As others have stated, just about any oil will help, and work. Aqua-Tap however, is a non petrochemical product and easier to clean up. Rapid-tap, and Alumi-Tap are easier to clean up than oil. Here at work the machinists will whack you upside the head with a spud wrench if they catch you using oil on their machines. That's why I use cutting fluids. Helps me keep access to equipment I like to use from time to time.

Your bits with the "blue tips" are most likely toast. Buy a nice quality drill bit, and use a cutting fluid, or oil. Slow that DP down, and just let the bit cut through and you'll be fine.

[Jason Roehl]

I'm no machinist, but try titanium-nitride bits. I have a Craftsman set from several years ago, and while I have broken a couple of the smaller ones, only 1 or 2 show any signs of being dull, and I have darn near abused these bits (i.e., drilled into steel with no oil or cutting fluid). Recently, I had to drill two broken bolts out of the cylinder heads on my truck. One of the drilling operations got a little off-center, so I ended up drilling part cyl. head iron. It took a little longer, but with some used motor oil on there (it was handy), and later some air tool oil, I got the job done with a 14.4V P-C cordless drill. It took about 1/2 hour for that hole at ~1/4", I think it was.

Oh, yeah, the bits were ~$90 for the 29 piece set (1/16"-1/2" in 1/64" increments).

[Randy Meijer]

The "DRILLING SPEED" chart that came with my DP states the following for a 1/2" drill bit. For mild steel and malleable, the speed should be from 430-720 RPMs. For cast steel and med. carbon, the speed should be 300-400 RPMs. According to my chart, 3200 RPMs would be the appropriate speed for a 1`/2" bit in wood. Perhaps there is a misprint in ytour chart or perhaps you misread the information?? In any event, you need to slow way down.....perhaps even more than has been previously suggested.

I haven't ever tried it; but what would happen if you used one of those 1/2" carbide masonry bits? Might that work or wouild it be a disaster??

[Stu Ablett in Tokyo Japan]

I haven't ever tried it; but what would happen if you used one of those 1/2" carbide masonry bits? Might that work or wouild it be a disaster??

You would destroy the bit.

The carbide tip is not for cutting metal, it is for grinding away and pounding away rock, concrete and such. The tip would not "Cut" steel.

Cheers!

[Bill Lewis]

Well Julio, I know you said you were going to scrap the piece with the hardened hole. There may be one way to possibly salvage the piece. You could try making the hole by using a cone shaped, shaft mounted, grinding stone. Grinding is the only effective way of dealing with hard, or hardened materials.

[Julio Navarro]

Thanks Bill, and all for all the great advice. The peice I scrapped is only a 3" length of 1x1x1/8" angle so cutting two new ones was much easier.

I bought a new drill bit, a DeWalt with a pilot point, I predrilled the hole with a 1/4" bit just enough for the pilot point on the DeWalt and I reduced the speed to the lowest setting on the DP and I used some grindng stone oil (I know I know, but its all I had)

It all worked like a charm. like drilling through butter. It was effortless with very little pressure. Amazing what using the right tools properly can do!

Thanks again for the great advice.

[Cliff Rohrabacher]

If the bits are made from high speed steel they are probably OK. You might grind a bit off and try it to see if it holds an edge.

High Speed Steel has excellent cherry red hardness. Which means you can heat the hell out of it up to 1,000Deg F and it'll still hold it's hardness. High-speed steel has high wear resistance. M-2 grade has up to ten times more wear resistance than conventional carbon tool steel. M-4 grade is three times more durable than M-2. High-speed steel also has excellent temper resistance,

Most carbon steel tool steels like O1, A2, A6, and S grades (chisel stock) steels will begin to lose temper at around about 355 - 360-Deg F.
High Speed Steel requires a reducing atmosphere or a diamond block to harden it. It is very different from most tool steels.

I hand sharpen my bits it's easy even with small bits with a little practice. Twist and roll with the wrist moving the forearm toward the wheel.

If the bit is one of those that requires a hard nitride coating then it might have a softer inner core and possibly you can't save it as a good bit but yes you might be able to save it for soft or in really dirty applications where you won't risk a nice bit.

[Rob Blaustein]

I'll offer this:
(newer use oil when cutting cast iron) Oil is a perfect cutting fluid. You can purchase specialty oils and fluids but any oil at all - even used crank case oil - is just fine and works great.

Cliff,
I assume that's a typo and you meant to write "never use oil when cutting cast iron." Could you elaborate--is it bad or just not needed? I had to drill some holes in my cast iron TS extension table. I was using a cordless drill and noticed that oil didn't seem to make much of a difference. I did notice, no surprise here, that it was a lot easier to drill through than the steel rails that I also had to drill holes in (for those I used oil).
-Rob

[Randy Denby]

I cant help it....I gotta reply. Julio, your a fortunate guy. By that I mean, buying a Dewalt bit with the pilot point, and having it do its job. I bought a set of these from Home Depot.....I cant get 'em to cut thru anything. I saw a thread on here about these bits awhile back, and it seems I'm not alone. So,it would have been ironic/ unfortunate if you had followed all this great advice, only to have a new bit let you down. Glad it worked out! And , bTW do you have a web address for the instructions on the sheetmetal brake? Thanks! Randy

[Cliff Rohrabacher]

Yes Rob that was a classic Cliff typo. Fingers mashing all over the keyboard.

Dry Cast iron chips are coarse textured, granular, don't adhere to the tool, and are easily cleared from the cut and the tool.

A high flow of any coolant would be fine but you'd need a little jet stream to do the job. Hence it's better to cut cast iron dry. It also doesn't contaminate the iron.

Oils are worse than unnessary for cast iron because of how they encourage heat transfer to the tool. The oil increases surface area, clings to the tool, and clumps the cast iron chips together preventing the air from carrying heat away. Because of these factors oil causes the heat to stay with the chip and then transfer to the tool. When the cut is done without any fluid the chips are ealily cleared with a vacuum, air hose, dry brush, or just knocking it off the piece when reliveiving the cut.

Dry cast iron chips tend not to have a smooth even surface to make good contact with the tool and they don't stick like steel chips do. Steel and copper chips adhere to the tool as they peel off, transferring much of their heat to the tool. Dry Cast Iron chips have less ability to transfer their heat to the tool with a concurrent increase in ability to transfer heat to the surrounding air.

(http://www.macraesbluebook.com)

[Rob Blaustein]

Cliff--very interesting. Thanks for the detailed explanation--now I'll know for next time.
-Rob

[Stu Ablett in Tokyo Japan]

Dry cast iron, if by that you mean what I was taught to call "Grey Cast Iron" like the stuff they use in old engine blocks, is nearly self lubricating, don't use any oil at all.....

...but I bow to Cliff's expertise on this.

Cheers!

[Stu Ablett in Tokyo Japan]

BTW do you have a web address for the instructions on the sheetmetal brake? Thanks! Randy

Randy, I think that Julio is talking about the sheet metal brake I made up for building my cyclone....

http://www.ablett.jp/workshop/images/sheetmetal_brake/sheet_metal_brake_ready.jpg

Worked like a charm

Give Me a Brake!! (http://www.ablett.jp/workshop/give_me_a_brake.htm) <-link to my personal website

Cheers!

[Randy Denby]

Thanks Stu!! I am in the HVAC business and bend metal from time to time. My cheap 4' Malco will not bend a consistent sharp edge for love or money. I am gonna try your design....Thanks!

[Julio Navarro]

That certainly would have been ironic. I predrilled a 1/4" hole where the pilot point fit perfectly. The bit then 'bit' right into the metal and whala...a hole.