I’ve got a Delta 12″ drill press (11-990) with a min speed of 620 rpm. I’ve got a 3 1/2″ hole saw that I want to use in the drill press, but it’s max speed is 140 rpm. I’ve called Delta and they don’t have any other pulley arrangements that would reduce the speed. I’ve looked at a router electronic speed control but the info says they work only with motors with brushes – my drill press is a 1/3 hp induction motor without brushes. I don’t want to do this job (many holes) using a hand drill – am I just up the creek?
Any suggestions would be greatly appreciated – thanks in advance.
Les
Replies
What kind of hole saw is it?
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Men will never be free until the last king is strangled with the entrails of the last priest.
~ Denis Diderot
Don't remember the brand - pretty much looks like all other 3 1/2" hole saw? Why?
I would think it would be fine in wood at 620 rpm. Clear the waste frequently.
Personally I would use a forstner bit, but if you gotta run what you brung the hole saw should be okay.
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Men will never be free until the last king is strangled with the entrails of the last priest.~ Denis Diderot
Edited 8/12/2009 11:46 pm by dgreen
Could it be a circle cutter instead of what we generally think of as a hole saw?
140 rpm seems awfully slow for drilling wood with any hole saw. Most handheld power drills can't go that slow and hole saws of that size are used everyday by contractors. Are you sure of that speed limit? It may be the limit for drilling in steel.
Otherwise, a photo of your drill press' pulley arrangement may inspire a solution.
Les,
If this is a conventional hole saw, a steel cup with small saw teeth around the entire rim, it should safely work at 620 rpm in a drill press but the stock will have to be very securely clamped to the table, the bit will try to spin the work piece with a lot of force. As you drill, you will have to back out a cup type saw every few seconds to clear the sawdust otherwise you will get a lot of heat build up.
If you have a wing cutter type of hole saw, a single steel bit on the end of a long arm, then keeping the rpm low is important.
John White
Shop Manager for FWW Magazine, 1998-2007
Thanks for all the good info - I'm considering which solution I'll use from this and other forums - I'll let you know how things work out.
Les
I did a test last year for fun using from 1/2" to 1 1/2" forstner bits in both pine and red oak. What I found is that from 3/4" up to 1 1/2" the best average speed was around 600 rpm in both woods using a plunge and release to let chips and saw-dust escape as John White mentioned. 3/4" down around 900 rpm was better suited using the plunge and release method.
So... why not try the 3 1/2" in a test just to see if how it responds at your lowest speed. But again.. you better take John's advice and clamp the stock with the force of h*ll or the stock is going to react violently. I would certainly not go to the trouble of possibly changing pulleys on a 12" DP to do a one-off job as you mentioned. I realize I was using forstners and you have a circle cutter but you have nothing to lose by running a simple test using plunge and release just to see.
Good luck...
Sarge..
Woodworkers' Guild of Georgia
I have drilled with a lathe ,it is possible to slow down many lathes to under 200 rpm or less with a shop made pulley. You would have to install the pulley on either the motor shaft or lathe spindle. This is a lot of work though. I mention it because it's possible.
I think you will be okay with the drill press. Take a hand drill and bore one 1/2" diameter hole at the perimeter of the hole on the waste side. The saw dust escapes thru this hole and makes it easier to bore with the holesaw. Actually the difference is like night and day.
You may run into problems with the 1/3 hp motor, I have a 3/4hp motor on a stand alone drill press and would expect problems drilling with a 3 1/2" holesaw.
mike
When you say to drill from the waste side do you mean right through the piece or stop short of piercing through?This sounds like a brilliant tip! Thanks.
I drill straight thru, the sawdust then doesn't accumilate like it does without the hole. You will notice the difference immediately. I found out this trick by accident years ago. I was drilling holes in a plank, one of the holes had a knot hole that fell out as I started to drill. It seemed to me that it was much easier drilling with the empty knothole. The next hole I bored was much tougher to drill,I hadn't bored the waste hole on this one. After this and thinking about it ,I decided to try boring a waste hole on the rest. Been doing it ever since.
mike
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