Drilling speed?

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You want to go real slow with a hole saw and use LOTS of water based coolant. Enough to help float chips away plus cool the blade. Squirt bottle works great. If you're only drilling 1", why don't you just use a standard drill bit? Me thinks it would be easier,faster, cheaper.

Karl

200 RPM if you can do it... 275 is about the maximum I'd try it with a hole saw... LOTS of fluid. Fill the groove made by the hole saw with fluid every few seconds while cutting. Make sure those chips are gone as they will clog the teeth.

A VERY sturdy table and/or drill press helps a lot. A Bridgeport helps even more. If you have a standard 1" bit, pre-drill a smaller hole first. Maybe

1/2" or so and use the same numbers. Better to go slow and careful (even lower RPMs if you can) than to ruin pieces and/or bits.

250-275 rpm

Technique is as important as speed here. The important thing is to clear the chips. One trick is to drill a small hole tangential to the hole you'll cut with the hole saw, on the waste side. That allows chips to find their way out the small hole. Another thing is to use steady pressure. It should cut, not rub. Rubbing rapidly dulls teeth and hardens what you're trying to cut. Too much pressure and you'll break teeth or do something else bad. Also, hold your part rigidly, not just one spring clamp. The force can be considerable, and you don't want a piece of plate steel to suddenly start spinning at 280 rpm and run a corner into your stomach - ow, makes me cringe even thinking about it.

GWE

And by the way, a WAY WAY better way to make those holes is with an ironworker. Centerpunch, put the part up to the machine, MUNCH, perfect hole. The layout takes most of the time, but you have to do that anyway.

GWE

I had noticed an Ironworker sitting at the local metal supplier and had asked if that could punch holes in 4" channel, I'm not sure what is the terminology, but I need the holes on the two side rails, not the flat back(?) piece. He had told me that the Ironworker can't punch hole in the side rails because it need to be a flat surface, the side rails are tapered.

I do have a 11 PC. 1/2 IN. shank SILVER and DEMING drill set from Use-Enco and a drill press. What would be a the best procedure for step drilling these holes? 1/4" -> 1/2" -> 1"?

First, drill a hole with your 1" S&D bit in something, then measure the hole. Those bits can cut considerably oversize if they aren't sharpened correctly.

I always start pilot drilling with 1/8". I buy those drills in 10-packs best quality I can, and don't bother sharpening them. They do the hard job. Then I'd go probably 3/8"->1". Same drilling speed for the 1" hole, 250-275 rpm. Lots of DPs don't go that slow.

Grant

SomeBody wrote:

Could not have gotten better advice if you paid for it... Grant has this nailed.

Try drilling a small hole about the size of the web of the one inch drill. Then use the one inch drill. Sometimes I drill the first hole just shy of all the way thru and fill it with cutting oil.

Note your drill press may not be able to go to a one inch drill after drilling the web sized hole, but that is the way to do it if you machine is rigid enough and powerful enough.

Dan

Your choice of a hole saw is likely a good one for this project. A twist drill would have a little trouble as it started cutting only on one side when you'd break through the leg.

I agree- clamp the piece well, and don't go short on lubrication. Clear the chips often, and run slowly----using a HSS saw. A carbon steel saw is most likely to fail immediately unless you can run it *very* slowly, and keep it cool.

One thing you might consider to help keep your holes in line is to set a stop on the drill press table. The channel would slide along the stop, indexing the holes in a straight line, and help prevent the piece from twisting under cutting pressure. It would serve double duty in that regard. Another short piece of the same sized channel would serve well, assuming it's square enough. You could clamp it to the drill press table, then clamp your drilled part to it with C clamps. A scribed line and a wiggler would locate each hole properly as you moved along the channel.

Harold

Harold

You have a long, painful road ahead. Lowest speed possible on your DP. You'll be wanting somebody to help you hold the end of the stock as you pull the quill. You'll need quite a bit of pressure, so make sure your drill press can handle it and you might need a bit of pipe to extend the quill handle to get enough leverage. BTW, you might check the age/condition of your drive belt. I had to drill hundreds of 1

1/2" holes with a hole saw in 1/8" wall 1x2" aluminum extrusion. I had an old belt on the DP, and whenever the hole saw grabbed or ran into resistance, the belt just slipped on the pulleys. Made the whole room stink like burning rubber! You will also want some good ear protection, as when the hole saw hits the metal, it makes a horrendous screeching sound. I used plain 3-in-1 oil in a pump oiler, squirted liberally on the hole saw and the work. Good luck!

Oh yes!!!

And... As far as coolant goes. You are gonna need lots of it. Not so much for cooling but for flushing those chips out.

Normally I take Dan's advice literally, he's a real smart experienced guy. I don't agree, however. On many drill presses, the downwards force required to keep a 1" drill cutting will cause the table to deflect enough to make a noticeable error in the positioning of the second hole. This is almost a worst case scenario in fact for table deflection if you think about it. Step drilling will require smaller cutting forces and the resultant table deflection will be smaller.

GWE

I'm surprised I don't see this more often...

I use this formula EVERY DAY.

Surface speed in Feet per Minute, divided by cutting diameter in inches, times 3.8

that is: SFM / inches * 3.8

for example, tool steel cutting mild steel, we use 60fpm as a rule of thumb.

60fpm / 1.0" * 3.8 = 228 rpm

Now you can find a reasonable speed without having to refer to a chart =)

Blushing..... I did say his drill press might not be up to it. Drilling a pilot hole slightly bigger than the web reduces the downward force a lot from what it would be without the pilot hole.

If step drilling is required, remember the area being cut varies with the square of the diameter. So if you were going to use just two drills ( not counting the pilot ) you would use a .7 inch diameter drill and then the 1 inch diameter drill. Three drills would be .57 then .81 and finally 1. Four drills would be .5 , .7 , .86 and then the 1.0 Not very intuitive.

Dan

Grant Erw> >

It's worse than that, too. Drills that tend to cut oversized lose their ability when they remove only a small amount. You do that by double drilling. It's the way holes are drilled when size is critical, unless drill jigs are employed. Assuming I was going to drill the holes in question, using twist drills, I'd open the hole to 15/16", or even 31/32", then go for size. The machine available would dictate other drill sizes, if any.

Harold

Its a waste of time doing the 3/8" drill IMHO. Simply drill a pilot hole the size of the 1" drill web thickness and making sure the work piece is Securely held in the vise, for for it, pecking once you are at full diameter.

If the work piece is thin..it may pull itself into the drill flute at break through. However..if its that thin..you should have been using a Uni-bit or hole saw in the first place.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

Ok..you got me. Ignore my previous post. I forget other folks dont have heavy drill presses or mills.

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner