Production drilling advice needed

Hello folks,
I am the sawyer for the company I work for, and generally run the saws, the bender and an assortment of punches. We've got a different
fella who specializes in drilling, but he's gone this week, so I'm temporarily running the drills as well. Normally, I don't have any problem with this, but tonight I had to drill 2.5" x 2.5" x .25" square tubing instead of our standard solid stock, and I had nothing but problems- I'm hoping someone here will be able to give me some insight into the problem, or maybe just a link to a good drilling primer.
The material is held in a shop-built fixture that surrounds the tube on all four sides, and holds the material in place with a bolt on the side. We use infinately variable speed drills with pneumatic feeds, No.2 morse taper shanks, and a good coolant system. The material in question is 1018 mild steel (cold-rolled) and the problem I kept running into was that the drill did not want to finish the hole in the top side of the material- instead of drilling through, two small chips on either side of the hole would ride up the flutes and either twist the bit out of the chuck or jam the bit tightly enough to stop the quill (broke a couple of bits that way). The bits I was using were 17/32" HSS.
I monkeyed around with it a bit, and varied the drill speed between 250 rpm and 325 rpm, and tried feed rates between 1 and 6 inches per minute. It didn't sieze up every time, but the speed at which the drill press would operate properly for me (250 rpm with an approx. 2" per minute feed rate) seemed very slow compared to the speed at which we drill solid stock. The holes in the bottom of the tube went through just fine no matter where I set the speed and feed.
Is this just a problem with drilling tubing, or is there something I am doing wrong here? Any thoughts would be appreciated. Like I said above, it's not my normal job, but it comes up from time to time, and I hate to be wasting bits for lack of a few moments of education.
Thanks for your advice!
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that is the problem with mild steel, the chips do not break. you need to interupt the cutting occasionally. if it was on a cnc machine, you could program a break into it. if you are drilling manually, you could lift up on the bit for a second and it would break the chip. the reason why you don't have a problem with the bottom hole, is that the chip is probably breaking off inside the channel when it hits the top.

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wrote:

It's kind of halfway between a CNC and a manual operation, so it's tough to get the drill to do anything but drop at the set feed rate. Any chance that a chip breaker on the fixture right next to the bit would do the trick, or am I just barking up the wrong tree? My other thought was that a milled block with a pre-drilled hole inserted into the tube might work as well, provided it sat in the same spot for every part (which can't be too awfully hard inside of a fixture with a backstop)
I suspect you've got the problem nailed, though- I never have the same problem when I use the mill with the peck drilling cycle. Unfortunately, our mill is down for repair more often than it is working (the thing is older than dirt, and has been used for years by less-than-gentle hands,) so I'm stuck with the drills when I have to work in that area of the fab shop. Anyhow, thanks for the insight!
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