glenn k 14th October 2004, 12:05 AM I need to slow my drill press down to 180rpm to countersink 1/2" holes in spring steel to make blades. On the slowest speed it is too fast is there an easy way to slow a 1/2 hp induction motor? I did make a tungsten drill bit to do the job but it is slow and gets hot so I think it would be better to slow the drill down and use a proper countersink bit.
Different 14th October 2004, 01:24 AM Use a coolant
himzol 14th October 2004, 09:52 AM Use a coolant
What he said, also try a tool cutting compound.
echnidna 14th October 2004, 09:54 AM Ther's no easy and economical way to slow an induction motor Glenn
Zed 14th October 2004, 10:13 AM You need to drop the voltage- eg if the motor os 240V AC, and you drop the voltage to 120V AC - the motor will work half as fast.
best for a sparky or engineer to do this for you. If you familiar with AC theory you may be able to work it out (and a practical solution) yourself but I would be concerned for insurance purposes.
as an alternative to voltage dorp or cooling compound what about a gear reduction pully system on the chuck ????
rev 14th October 2004, 10:25 AM If you can easily replace the pully on the shaft of the motor or the shaft of the drill spindle (or both) that might be the go. You need a smaller one on the motor shaft and a larger one on the spindle.
ED T 14th October 2004, 11:01 AM Zed,
The AC "squirrel cage" motor used in drill presses will NOT drop to half speed if you halve the input voltage. Speed is contolled by mains frequency and the design of the windings.
If you drop the voltage, then load up the motor, it will pop its cork.
Ed T
Zed 14th October 2004, 11:08 AM AAARRRGGHH!!! DC theory - dontcha love V=IR ?
Rev - Doesnt an induction motor not have pulleys ? I thought the speed was goveredn through a potentiometer in the windings .... thats why I suggested pulleys in the chuck....
rev 14th October 2004, 11:29 AM Zed,
I think almost all drill presses use induction motors and most are driven via pullys and belts (some in steel engineering workshops are driven by gears and shafts). Anyway, larger pullys on the spindle and smaller pullys on the drive shaft of the motor combine to reduce the speed of rotation of the drill I think.
This doesnt alter the speed of the motor, just the speed of the drill.
forge 14th October 2004, 09:26 PM I need to slow my drill press down to 180rpm to countersink 1/2" holes in spring steel to make blades. On the slowest speed it is too fast is there an easy way to slow a 1/2 hp induction motor? I did make a tungsten drill bit to do the job but it is slow and gets hot so I think it would be better to slow the drill down and use a proper countersink bit.
Glenn ,is your spring steel softened where you are trying to countersink?If it is still hard (the spring steel)I would use a dremel ,or the like and grind the countersink.
On the other hand ,you may know something I don't :D ,please tell how
you doing the countersinking(please forgive the pigin)and what bledes are you making.
Regards Bela.
glenn k 14th October 2004, 11:07 PM I'm using roil as a cutting compound it worked well to drill about 20 1/2 " holes though 8mm spring steel to the sharpen. The countersink bit is bigger and needs to go slower.
Bela it is new spring steel that has not been hardened. If it gets hot it hardens. When cutting it to length it got hot a few times and the cut off wheel had trouble getting through.
I blunted a countersink (cobalt HSS)bit in one go $60 worth I took it back and paid another $15 to replace it with a titanium coated one and was told to run it at 180 rpm. The tungsten carbide bit I made works but I feel the drill is too fast. The blades are for a 9" wood chipper.
I was hoping there was something available to remove every second peak from 50 Hz to make 25 Hz so have a motor with half the speed and half the power but it appears there is no such thing. I may have to add an extra pulley shaft but a very large pulley on the chuck shaft may be easier.
Thankyou for the input every one.
Glenn
echnidna 15th October 2004, 10:48 AM most of the variable speed portable drills can spin very slow, might be the way to go.
forge 16th October 2004, 09:17 PM I'm using roil as a cutting compound it worked well to drill about 20 1/2 " holes though 8mm spring steel to the sharpen. The countersink bit is bigger and needs to go slower.
Bela it is new spring steel that has not been hardened. If it gets hot it hardens. When cutting it to length it got hot a few times and the cut off wheel had trouble getting through.
I blunted a countersink (cobalt HSS)bit in one go $60 worth I took it back and paid another $15 to replace it with a titanium coated one and was told to run it at 180 rpm. The tungsten carbide bit I made works but I feel the drill is too fast. The blades are for a 9" wood chipper.
I was hoping there was something available to remove every second peak from 50 Hz to make 25 Hz so have a motor with half the speed and half the power but it appears there is no such thing. I may have to add an extra pulley shaft but a very large pulley on the chuck shaft may be easier.
Thankyou for the input every one.
Glenn
Thank's for reply -explanaion Glenn.
Regards ,Bela.
"Makin Sawdust" 18th October 2004, 11:39 PM If all you want to do is drop the speed you can use a heavy diode in series with the ac feed. This will feed one half only of the sine wave AC to the motor and effectively be 25 hz., hence approximately half speed! You will have to use a diode with ample current rating (amps) and a voltage rating of at least 600 to 700 volts. Bear in mind that the available power will also drop to a little less than half. Better to play with pulleys. Cheers. Les.
Bunyip 19th October 2004, 01:53 PM I was hoping there was something available to remove every second peak from 50 Hz to make 25 Hz so have a motor with half the speed and half the power but it appears there is no such thing.
Glenn,
If you are half handy with the soldering iron, go down to Dick Smiths and pick up a motor speed controller kit (you'll have to put it together). The way this works is quite sophisticated, but basically allows infinite speed control whilst maintaining torque and smoothness of operation (if you start chopping the wave forms you can get jerky action).
I have used one of these on my 3 hp router with great success.
Bunyip 19th October 2004, 01:56 PM Grrrr - sorry for the dud advice.
Just remembered that the speed controller can only be used with universal motors :mad:
Use pulleys :o
glenn k 20th October 2004, 01:01 AM thankyou Les and bunyip
forge 22nd October 2004, 09:16 AM There is perhaps another way.One can buy a 3phase motor and controleror it - an inverter.It is supposed to be able to infinitely vary the speed -as I understand it .
Not cheap.
Regards ,Bela.
glenn k 22nd October 2004, 11:07 PM Bela is this one of those motor generator things or something else?
I was just thinking don't 3 phase motors work on single phase only a lot slower and less power I supose.
forge 23rd October 2004, 01:30 AM Bela is this one of those motor generator things or something else?
I was just thinking don't 3 phase motors work on single phase only a lot slower and less power I supose.
Glenn,recently I was going to get one of these 3 phase motors and a inverter/
controler .This is run from single phase 240v.Have read about this type of motor control in Model Engineers Workshop.A UK publication.I was phoning around looking for dc. motors when one of the places I called told me about it .From memory I think the price was just under A$300.If you interested I can try to go back trough my notes .Let me know.
Regards ,Bela.
PS.http://www.mechtric.com.au/Pdf/MStarters/VarSpeed.pdf
I think it was this type of drive system
glenn k 23rd October 2004, 06:13 PM I have a 415-440v single phase motor that I have tried on 240v it runs slowly is it OK to use on 240? It does have thermal overload.
Well I slowed the drill down by running the belt on the motor shaft it slipped a bit but was enough to see that the titanium coated countersink bit even at ~180 rpm was not good enough. I shapened up my home made tungstencarbide countersink and it works fine at ~600rpm in short bursts.
Thanks Bela that mechtric site was interesting but I will just leave the drill press the way it is now. Thanks for your help all those that posted.
forge 25th October 2004, 10:57 PM I have a 415-440v single phase motor that I have tried on 240v it runs slowly is it OK to use on 240? It does have thermal overload.
Well I slowed the drill down by running the belt on the motor shaft it slipped a bit but was enough to see that the titanium coated countersink bit even at ~180 rpm was not good enough. I shapened up my home made tungstencarbide countersink and it works fine at ~600rpm in short bursts.
Thanks Bela that mechtric site was interesting but I will just leave the drill press the way it is now. Thanks for your help all those that posted.
It's great that you have achived satisfactory result .
Regards ,Bela
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