Best drill bit and drill speed?

[TNhobbyfarmer]

I need to drill a large number of a 1/2 inch holes in 1/8 inch wall steel tubing. I will use a drill press. What will be the best (longest lasting) type drill bit to use? Also, what would be good RPM speed to use?

 

[whistlepig]

Around 700-800 RPM for drilling mild steel. Cobalt drills last a little longer than high speed drills but cobalt is brittle, easy to break, and more expensive than high speed bits. You may want to consider a Unibit. These work well on thin walled pipe. A good cutting oil will greatly increase the life of the drill bit.

 

[mikehaugen]

what is a "large number of holes?" I like the dewalt pilot point bits because you can do a 1/2" hole in one shot. They last reasonably long (especially in a drill press) but they can't be resharpened. I haven't bought them for a while... the ones I have are made in Germany, I think the new ones are made in China or Taiwan so I don't know if they are as good. They are HSS, and as posted above, that is probably the best for your situation. Though using a drill press you may be good with the cobalt bits. The unibits are a good suggestion, and they do well in thin metal, but if you are doing a couple hundred holes I think they are too expensive and you would be better off with good regular bits. You can probably buy 5 or 10 decent twist drills for what a unibit costs and if you are doing them all the same size, you are not getting the advantage of the unibits.

 

[PILOON]

I need to drill a large number of a 1/2 inch holes in 1/8 inch wall steel tubing. I will use a drill press. What will be the best (longest lasting) type drill bit to use? Also, what would be good RPM speed to use?

Lowest speed you can do on the press and use cutting oil and you should be able to do a ton of holes.
Naturally a good bit is what you want, like Dormer is one top brand.

 

[whistlepig]

Too low of speed and the drill bit will grab and chip the edges. Too fast of speed the drill bit will burn up. It's best to use the recommended SFM when using high speed tooling. The recommended SFM for high speed tools in mild steel is 100 SFM. That works out to be 746 RPM with a 1/2" drill bit.

 

[sal64]

HSS Bright Finish 118° Jobber Drills - Jobber Length Drill Bits | MSCDirect.com

 

[SPYDERLK]

I would use about 400RPM for the 1/2" ... but I would drill a 1/4 pilot first and then go to a Unibit, as mentioned, due to thin wall. Square or round tubing?

 

[flusher]

I need to drill a large number of a 1/2 inch holes in 1/8 inch wall steel tubing. I will use a drill press. What will be the best (longest lasting) type drill bit to use? Also, what would be good RPM speed to use?

What's the diameter of the tubing? If it's 1" dia or more and with only 1/8" wall, I'd use a step drill at 150-200 rpm like electricians use to drill holes in circuit breaker boxes, etc. I'd be concerned about out-of-round holes using a twist drill in your thin-wall tubing.

Good luck

 

[TNhobbyfarmer]

I would use about 400RPM for the 1/2" ... but I would drill a 1/4 pilot first and then go to a Unibit, as mentioned, due to thin wall. Square or round tubing?

Rectangular

 

[SPYDERLK]

Rectangular

Good ... better for the bit than round. Anyway, as previous noted, it will be difficult to get round holes at 1/2 size on 1/8 stock unless you use a UniBit. Beware of the HF step drills. They seem to all be undersized - probably the nearest metric inch equivalent. For just using 1/2" possibility - -If you have a vise setup you could drill a pilot hole in thicker metal and then use that to stabilize the bit for each hole.
... Or you could drill a slightly smaller hole and use a tapered reamer such as McMaster Carr item # 3089A15 to finish.
larry