Where can I get LARGE Drill Bits at good prices??

[dourobob]

My buddy and I are working on a project where we need cut holes in some steel plate. Some of the holes are 1.5 inches and some are 2.5 inches. The largest drill we have for the drill press is 1 inch (1/2 inch shank). The steel ranges from 1/4 to 1/2 inch thick. We would buy the bits if it didn't take a small mortgage /w3tcompact/icons/grin.gif to finance them and if we could find a supplier. Any suggestions?

As an alternative, we are considering taking the parts to a custom machine shop. With the pieces having the same diameter holes aligned and tacked together it would mean set up for five holes - two at 1.5 inches and three at 2.5 inches. The pieces are not large and can be easily handled by one person. What would a reasonable shop rate be for such a job. I am in Ontario, Canada so if you are quoting rates please indicate the currency.

Thanks for any ideas.

Bob

 

[Spencer]

I would try a hole saw made for cutting metal. Remeber when you are using a hole saw in metal to go slow and cut your way through the metal. Too many people go fast and try to melt their way through.

 

[northcreek2624]

A hole saw would be slow but for one or two holes it would work,otherwise I would have them punched,it's not as expensive as you might think.
While on the subject I discovered some super bits that will drill through car springs or the like,here's the link if you want to check them out. 1 1/4 bit $20 bigger sizes available....Mike
<A target="_blank" HREF=http://www.bitlady.com/>http://www.bitlady.com/</A>

 

[hazmat]

It used to be that if you needed a 2" hole, you used a 2" bit. With today's CNC mills, they would put in a 1/2" mill and spin it in a circle to cut the 2" hole.

Alternatives are to punch it or CNC plasma cut it.

A twist drill of that size is going to cost you big bucks.

<A target="_blank" HREF=http://www.mcmaster.com>mcmaster carr </A> 1.5" $80, 2" $172! (US dollars)

Around here, a reasonably priced machine shop is going to charge about $50 (US) an hour. Don't know if they'd have a minumum. Typically you won't get "drive thru" service. They'd hold your small job to do in between larger jobs.

Also, they aren't going to drill them all at once. They will drop each in the clamp, zero it & mill each hole (probably with the small 1/2" mill)


Don't know how round/smooth/accurate the holes need to be, but I'd use the hole saw & go as SLOW as your drill press will go! with lots of oil. Sometimes it is easier to drill 1/2 way thru on one side, then flip it and go from the other side.

 

[JerryG]

For anything of that size, I always have a plasma torch used on it. It will give you almost as smooth of a cut as a bit. Any metal shop that does very much should have one and be able to do it for you if the metal isn‘t to thick for their torch.

 

[hazmat]

Hmm, Jerry brings up a good point. The local welder likely has a plasma cutter & probably is cheaper than a machine shop. Also better chance of getting it done in a timely fashion.

Might save a couple extra bucks if you offer to make a jig for the guy. Basically, cut 3/4" plywood with holes that are oversized by the diameter of the plasma cutter head, IE if it's got a 1" dia head, you'll want 2.5" & 3" holes for your template. The welder should be able to tell you how much to oversize the holes by, if he can't use somebody else!

 

[rdln]

try a flea market to buy them or contact local community college or high school might have a shop and do it for a "donation".

I have used a hole saw for clearance holes when mounting trailer harness sockets on truck bumpers, as said before go slow and use oil.

 

[EdDekker]

Bob,

The big twist drills show up on ebay with low prices.

Do you have a drill press that can handle a bit this big? A 2.5 inch bit this size will require a #5 Morse Taper spindle and a speed slower than a typical home/light industriual drill press can handle.


If a clean hole is not needed using a plasma cutter would be the easiest method.

If you need a cleaner hole you can cut the hole.To cut the hole I would use a bi-metal hole saw but drill a few 1/4 inch holes for chip clearance. Mark your center, and use dividers to mark the circumference of the hole. Now you drill a few (about four for a 2.5 inch hole saw) 1/4" holes just inside the circumference and drill your center pilot hole.

The holes on the circumference will give the chips somewhere to go. Start cutting with the hole saw, and keep the coolant flowing (don't just dribble oil - flood the surface with coolant, water directly from the garden hose will work) to flush the chips.

 

[em14]

I agree with most of what you have advised except the water flooding to cool and lub the cutter ... If he is using an electric hand drill, life could get very exciting when he gets a bit of water in the drill motor .. so be careful of any liquids and electrical devices getting together ... I know what you mean and you do need to keep a lot of lub on the cut ...
Leo

 

[Darren]

There's a company named Hougen that I believe came up with the idea of the annular cutter. An annular cutter has a hollow coreand teeth on the periphery so it only cuts out a thin band of material at the edge. I've seen them made that will cut through 2" thick steel. When you're finished you're left with a round chunk that ejects out of the cutter. They're a lot heavier than holes saws. They're designed to be used with magnetic base drills.

I'd try to locate a contractors rental place that might have one. I know they go at least to 2" dia. Not sure abot 2.5" though. Either way you're only cutting a small percentage of the material rather than reducing everything within the hole to chips. That takes far less hp. If you're going to use a 2 1/2" drill to cut the hole in one shot, I suspect most shops would use a radial drill which is to a drill press as a Mack truck is to a golf cart. Either that or they can use a boring bar in a vertical mill.

The other idea which would also need a magnetic drill, if you could run it at low rpm, is to use a boring bar. By repeatedly adjusting the offset of the boring bar you can get the exact hole size you want.