U Drills

[Ian B]

Anyone out there used U drills? These are the larger size drills that use a replacable carbide tip; Sandvik, Kennametal & others make them.

I need to drill quite a few 24mm holes through H beams and 10mm steel plate - any thoughts on the suitability of these drills, other suggestions? I'll be using my turret mill for the drilling, so power & rigidity shouldn't be an issue.

Thanks,

Ian

[DR]

We've had very good luck using Rotabroach annular cutters for the type work you're describing. They aren't cheap and you should have the coolant inducing shank for best cutter life.

I think I'd prefer them over the replaceable carbide tip style, though.

[Bill Cook]

Don't know anything about U dills, but I'd want to know if they do well on such proportionally thin material.
Or breaking through against a fillet or tapered thickness, if drilling in those areas of an H-beam.
A two lip HSS drill would take the least power and is the most forgiving. Even without a pilot hole.

bc

[torker]

We use mag drills w/annular cutters all the time for structural steel. The annular cutters don't take much power to drill holes and they cut through flanges and angle cuts with no problem. However...they are a PITA if you have to cut through two thicknesses. You have to remove the drill and fish out the slug, then line everything up again and continue. If you aren't really careful and catch the slug in time, it can bind up and snap the cutter. Even with hand applied coolant they don't stay sharp for very long. Would probably do better with a proper coolant setup though. Another thing I don't like about them is we have to send them out to get them sharpened on a regular basis. I've never used them on a regular basis in a sturdy mill setup but I'd assume they'd last a bit longer. For smaller diameter holes (1/2" and under) we've all but given up on annular cutters for the mag drills. Regular twist drills will out last an annular cutter about 10 to 1 and we can sharpen them "in house". They do make a bigger mess and require a little more power to turn but the guy using twist drills will drill a lot more holes in a shift than the guy with annular cutters. Note...this is for the smaller diameters only. For production drilling with larger holes the annular cutter/mag drill setup is the best we've tried...even with their down sides. I'm interested to hear about the indexable drills though. Would be nice to find something new and better for this job. Maybe it would cut down on the number of guys phoning in sick when they know they have to drill a few hundred holes next shift...LOL!
Russ

[Ian B]

Thanks for the replies, guys,

I've used Rotabroaches before, and liked them - it was just that I was wondering how long they'd last after having to contend with the mill scale usually found on H beams, with or without coolant. Hence me looking at drills with replacable carbide tips.

I'd only be drilling one piece at a time, and not close to the fillet or in much of a tapered section (they're bolt holes). I was avoiding normal HSS twist drills because (I think) in 24mm, they'd need a pilot hole, which means swapping a lot of tools - I'd like to go top full diameter in one pass. Having a bit more swarf around isn't too much o a concern.

Ian

[suprdvn]

I use U-drills all the time in a CNC lathe. With thru coolant the cutting speed is around 700. It's amazing watching the chips shoot out the hole.

The size of the hole is somewhat adjustable with an offset (lathe only).

The drill can double as a bar (lathe only).

No pecking. It's not necessary and should the insert come down on a chip it will be destroyed.

No interupted cuts. I don't think it would work in my opinion anyhow.

No stacking. When the drill breaks though it leaves a disk.