Dum question: best way to drill sheetmetal?

I've had a lot of this to do lately, and besides breaking drill bits my results have been fair to middlin. Any suggestions? I've been starting small, using a lot of 3 in 1 oil, but I think I've been drilling way too fast.

So do I start small and work my way up, using oil and a low drill speed?

Or do I start with the final size bit and drill slowly, oiling as I go? I think I read somewhere about doing this because using the smaller bits work hardens the edges or something like that, I don't recall.

It seems like once I have a hole drill, the rest is farily easy, just getting that started is the tough part.

I've got airtools, HD electric, and whatnot I can use.

I've tried a HF step-bit I think it's called and that was pretty worthless, didn't cut anything but then maybe my technique was wrong.

The bits I was using were just consumer grade black and decker. I guess I just spun too fast and pressed too hard on the small ones

I'm specifically trying to drill on the front doorjamb of my '51 Ford to install door poppers, and around the hood and trunk latch to install new autolock products. I was doing some drilling on the side of the engine compartment, the inner fender wells, trying to mount the battery box in a non-stock location(header interference), but after breaking some bits and a second opinion I think I'm going to just weld some bolts to it as studs and brace it at the bottom so no more drilling that thick metal

Anyway thanks for the help!

EDIT: I shoulda mentioned, I've been using a punch before drilling so no wandering really, but yeah breaking before getting a hole started. I guess I've just been impatient, staring at that drill while bent over and not seeing any curlicues of metal coming out. So naturally I figured I need to press harder and drill faster! And break a bit....heh

Good to hear the step drill bits work, I just had no luck getting a hole started with one. I guess I'll try using a smaller bit to drill through first, and *then* try the step bit? Worth a shot before I break down and get some name brand ones.

 

I use the step drills. i have a set from Makita. They work great.

 

I also use the step drills with great success... even the HF ones!

 

Look into roto broaches........clean hole every time, you drill a 1/8'' pilot hole and go.....Littleman

 

You might try using a center drill to start your hole. They are sharp and help hold a good center. Center drills like to b spun pretty fast.

 

If the bit is moving, you need to start with a punch, or even just a screwdriver dimple for the bit to sit in.

If the bit is breaking before it punctures the metal, you are pushing way too hard and crooked at that.

If the bit is digging a groove and sliding across the metal, it's not sharp enough, or is not sharp in the center of the bit.

Basically, start with a good bit and push lightly and straight into a small dimple. Speed shouldn't matter as long as it's not 5rpm or full-tilt boogie.

 

Don't drill fast, it'll heat up the metal and the bit and cause it to dull quickly. Have you ever used a drill press, they are somewhat slow. The drill is working when you're getting a nice cork screw effect in the metal waste. I usually go medium speed on a hand drill.

 

I use step drills also. Ain't used HF ones though.

 

Thanks for the input, you guys. It's a little intimidating admitting you don't know how to do something on the HAMB.

At least I searched the forum first

 

I would get a new set of bits. I like the titanium coated ones from Lowes or Tractor Supply. Get the ones with the 3/8 shanks so you can drill up to 1/2 with a 3/8 drill. Any oil but a cutting oil has anti wear additives which make the bits not cut. Don't use them!

 

HF step drills, had them on sale a few weeks ago like less than $10 for a set of three, bought two sets they work great!

 

On drilling sheetmetal,I've changed over to step-drills..even the cheapo HF ones work great for me....twist type drillbits always seemed to get "grabby" just as you get thru the other side...and left a nasty burr


My $o.02

Stan

 

Thanks Andy! I wondered about that myself. I was using a friend's drill, so I did it his way, but true cutting oil sounds makes good sense to me. I'll pick some up and give it a try!

I'll get some titanium bits while I'm at it. Cheap way to save time and trouble.

 

Good bits make a lot of differance,old cars have some hard metal in them.

 

Yblock or Turbo:

Do you *start* the hole wtih the step bits? I bought the 3 pc set of titanium coated ones on sale at HF a few weeks ago myself hehe but I think I tried the smallest one to start the hole and just didn't get any bite at all. That said, I'm sure I was using 3 in 1 oil and drilling as fast as possible.

 

Cutting oils usually have something in them to promote cutting. I remember 25 years ago, being new to the machine shop and complaining about the sulphur smell. The old hands couldn't even smell it.

 

For sheet metal, I start with a center drill and finish with a step bit. The center drill cuts in quick and gives a good tapered hole for the step bit to pilot on. The step bit leaves a nice clean edge and won't grab like a regular bit.

If you're drilling something thicker (like 1/4 plate), start with a center drill and finish with a regular bit. I like to go straight to the final size; as you mentioned, the heat from drilling the smaller size holes work hardens the metal.

Speaking of work hardening the metal, spinning your bit too fast will heat the metal up and before you know it the metal will be near impossible to drill through. If you have a drill press and can adjust your speed, make sure to slow it down with larger bits and faster for smaller ones. You can find drill speed charts on the net that will tell you how fast to go based on bit size. For hole saws, go S-L-O-W.

We use these at work.

 

These are what i have used. Bought them from MAC tool's a bunch of year's ago. Not too cheep, but as Littleman said, clean hole everytime.
I've even used them to drill hole's in painted tin and just about everytime they have produced a hole without even marring the paint to the outside of it..
Nice quality tool.
Tony

 

For drilling the pilot holes in sheet metal, I've been using some double ended 1/8" stub bits that are made for drilling holes in sheet metal studs. They have a shallower angle and they're ground differently at the tip to make them less likely to wander. They're short, so you can press harder without breaking them. Sometimes the back end will snap inside the chuck, but I don't think I've ever broken the front end while drilling.

Once you get a 1/8" pilot hole, it's easy to go up in size. The Unibits work great once you get up over about 1/4".

I bought some real cutting oil from ENCO for about $12/gallon -- a lifetime supply for me. I keep it in a little plastic dispenser bottle.

 

Another vote for step drills, the're tits for sheetmetal.

 

So is this the type of center drill bit I want to be using?

http://cgi.ebay.com/5-PC-CENTER-DRILL-COUNTERSINK-BIT-DRILLING-TURNING_W0QQitemZ280177343250QQihZ018QQcategoryZ50383QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

I'd never even heard of a center drill bit before today. I can't wait to try one out.

Oh and will these work on a portable type drill or do I need a lathe? They're calling them Lathe Mill Center Drill tool set, so that's what's corn-fusing me.

EDIT: The seller said I can use them with a lathe, hand drill, or drill press. Guess I'll give them a shot!

 

Step bits here too,also good starret hole sawsfor big holes."roto broaches" are garbage the torque the deliver can destroy thin stuff.Annular cutters were designed for heavy fab. work

 

I always use HF cheep step drills, run them very slow and no problems. I have even drilled 1/4" plate with them.

 

Go to a tool shop , don't buy the cheapest bits there are...they are a waste of time you don't need anything ridiculous...normal twist drills will do the job .Buy a pack of 1/8 bits , or even double enders for all your pilot holes, they aren't too big ,and only an oaf will break 'em.

Don't use 3 in1 oil that's for sewing machines....buy some cutting fluid ,there are some very good ones now that won't give you cancer in 20 seconds like the old ones.Good ones will leave a drill-bit almost cold and will you give you a continuous piece of swarf....not chips....this itself shows you you have a sharp bit that is working the way it should be.

with a good quality bit you don't need lots of pressure and high speed is pointless..it just creates heat which will ruin the tempering. Remember you are cutting , not abrading the steel away.

Centre punch , 1/8 pilot ...slowly til near the end. when you feel it start to give or it bites near the end pull it out ....run it fast and then carefully while it is running insert it back into the hole to run through the other side ...this part needs very little pressure....

For bigger Holes or things that you need to "open up" ever so slightly buy a tapered reamer....like this, they are invaluable



de-burring holes gently with a countersink works on sheet too...even a stone on a drill can do....

Drill bits are very very hard ...there aren't many things you can't drill into if they are good quality and well looked after...even a garden variety 1/8 bit should be able to drill through 1/2 plate if it is treated right.

If you break bits , or they won't drill in you are using too much speed or a blunt bit , or you are pressing too hard AND off centre

simple really.

good luck

 

Roto broaches work great while in capable hands, just like everything else...when drilling a hole with a drill bit, hole saw, roto broach, ect. the user controls the speed and force..Your just not going to find alot of people that have the roto broaches handy to use, or willing to make the investment to add them to their tool arsenal.........Littleman

 

Just a little something to think about. Drilling a hole can't be this difficult unless you are using a reversible drill and have it switched to reverse rotation by mistake, therefore trying to use a clockwise drill bit, counter clockwise.

 

.................he could be right you know.....

sheesh.........we might never know

 

If you know an older machinist, ask him to show you how to sharpen drills for sheet metal. I have seen them for sale, but I grind my own. I can best describe them as similar to a bottoming drill , with a tit in the center to pick up the punch mark, and a protruding cutting edge on the edge of each flute. SLOW drill speed w/lots of cutting oil. Step drills are still the cat's meow, though. But again, they should be very slow speed and lots of oil. Good luck and don't worry about questions, that's how all of us learn. My old man always said, " There is no such thing as a dumb question, but there sure are a lot of dumb mistakes". Git 'er done....Ole Pork

 

Someone I know did this, but first made repeated trips to Home Depot, until he cleaned them out with the size bit he was using....Finally called with lots of frustration, I went over, he had 11 wasted bits. I grabbed his drill and put my finger on the chuck and blipped the trigger, and it was in reverse......Sometimes the basics get us all at one time or another.....He ran a screw machine for a living.........Littleman

 

There are cheap drills then there are CHEAP drills, too. I have seen them with off center point grind, no rake or relief, etc., drills nearly incapable of cutting...small sizes usually worse than bigger, too. One of my friends had a cheap drill actually untwist its spiral grooves on him...
And of course the reverse thing...I would be embarassed to admit how much time I have wasted spinning drills backward. If you aren't seeing any twists coming up when drilling at soft steel, either your point is no good or you're running backwards!