How to slow down a drill press?

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I have an old drill press that was my first machine tool buy back when the first digit in my age was a "1" (a long time ago). It is a decent quality import with a 3/4 hp 1725 motor and two stage step pulley reduction. The problem is that it will only go down to 240 rpm on the slowest setup. I would like it to go down to 150 rpm or less to turn large diameter drills and hole saws. I haven't seen any slower running AC motors and I don't think a rheostat would work with that power motor. Has anyone modified their machine to run at the slower speeds and how did you do it?JimCut an MGB and widened 11" C4 Corvette suspension and LT1 Chevrolet power & 6 spd. Pictures here:Part 1http://forum.britishv8.org/read.php?13,7581Part 2http://forum.britishv8.org/read.php?13,22422
Reply:Pulleys or a different motor....if you try to vary the speed of the ac motor with a current drop it will let all the smoke out of it....Mike
Reply:You might be able to find a smaller pulley for the motor.  Odds are, you can't put a larger pulley on the quill because of the belt guard.Sorry, nothing simple comes to mind right now...America Needs AMERICA'S Oil!!!"Global warming is the greatest scam in history ...There is no run away climate change. The impact of humans on climate is not catastrophic. Our planet is not in peril."--John Coleman, Founder of The Weather Channel
Reply:You could use a frequency drive, Automationdirect.com sells them. $99.Last edited by tnjind; 02-10-2008 at 06:22 PM.Reason: spelling, again.
Reply:Originally Posted by tnjindYou could use a frequency drive, Automationdirect.com sells them. $99.
Reply:http://www.baldor.com/products/detai...40C+AMB%2DCONTThey do make lower rpm motors, however you can see that you can get two more drill presses for the same price. If there is a motor rewinding company near you they may have a great deal on something like that laying around. This would also limit your top end. I never use the really high speed anyway. But if you have a center free wheeling pulley you can get a pulley with a larger and smaller pulley on it. You might only need one new fan belt. It depends on how big a pulley you get. But that would probably be the best way to slow it down. You may have trouble using it in all the other speeds though. Because you may not be able to get the center pulley to swing away from the walls of the enclosure enough.        Sincerely,             William McCormick
Reply:Yep my bad, no single phase on the freq. drives, I work mostly with 3 phase. I just purchased the $99 one for a 120v single to 240 3 phase conveyor.I should just go back to learking and not respond.
Reply:Naw, don't do that! Somebody else will have the same question and benefit when you ask! Here is where you get to do a little bit of cost vs. benefit  analysis. Either you modify the press that you have, or you invest in a second machine with the speeds that you need, or you sublet the work to someone else this time.City of L.A. Structural; Manual & Semi-Automatic;"Surely there is a mine for silver, and a place where gold is refined. Iron is taken from the earth, and copper is smelted from ore."Job 28:1,2Lincoln, Miller, Victor & ISV BibleDanny
Reply:Originally Posted by Jim StabeI have an old drill press......it will only go down to 240 rpm on the slowest setup. I would like it to go down to 150 rpm or less to turn large diameter drills and hole saws....
Reply:Originally Posted by Sober_Pollock"Variable" frequency drives are for three phase motors.....to the best of my knowledgethere aren't any that will operate a single phase motor.
Reply:Oh one more thing, you can use a 3 phase motor on you drill press if you want a variable frequency speed control to run it and power it from single phase... keep an eye on eBay.  You do not want to buy one retail $$$$ :0Me!
Reply:Originally Posted by tnjindYou could use a frequency drive, Automationdirect.com sells them. $99.
Reply:I slowed my spindle speed by adding a jackshaft.  Eliminated overheating and increased torque.
Reply:Originally Posted by WeldordieI slowed my spindle speed by adding a jackshaft.  Eliminated overheating and increased torque.
Reply:You may be able to temporarily remove the belt housing and put a larger pulley on the spindle and a smaller on the motor, but if you have a lot of low rpm drilling projects you need to get a variable speed drill.
Reply:You could convert it to use a variable speed DC motor & controller, but it might be cheaper to buy a new drill press.Hobart Stickmate LX AC/DC, Millermatic 252 & 30A spoolgun, Thermal Arc 185 TIG, Miller BWESmith Oxy-AcBridgeport 2J , South Bend 42" 9AHusky 7.5 HP 22.3 CFM 80 gal compressor
Reply:Originally Posted by tnjindYep my bad, no single phase on the freq. drives, I work mostly with 3 phase. I just purchased the $99 one for a 120v single to 240 3 phase conveyor.I should just go back to learking and not respond.
Reply:How 'bout buying a mill???America Needs AMERICA'S Oil!!!"Global warming is the greatest scam in history ...There is no run away climate change. The impact of humans on climate is not catastrophic. Our planet is not in peril."--John Coleman, Founder of The Weather Channel
Reply:Originally Posted by 510robI for one am very grateful for your input, so please continue to speak up!I currently have a traditional motor-style 3-phase converter driving my metal cutting bandsaw.  I am now seriously considering buying one of the 1HP VFD 1-phase to 3-phase boxes for $125.  It would allow me to have infinitely adjustable blade speed between the belts, the gearbox, and the VFD!!! That's awesome!
Reply:Typically with a 3-phase motor on a VFD you get constant torque below the rated (60hz) speed and constant horsepower above the rated speed. The motor ratings spell that out.Lincoln SA200, HH135, Lencospot, HF80 Inverter, Rockwell 11x35 lathe, HF drill mill, Kama 554 tractor w/ FEL & BH, Belarus 250AS, lot's of Chinese tools
Reply:The issue with running a motor on a VFD at any speed significantly lower than its rated speed is COOLING.....If you slow the motor down very much, its built-in cooling mechanisms loose their ability to cool the motor.....(For example, if the motor has a fan built into it, and you slow the motor down, then you are also decreasing the amount of air cooling the motor).....Yes, the better quality VFDs run very well at "Below Rated" speeds. I have drives in use where I work that are able to safely hold 100% "Zero-Speed-Torque".....In other words: The amount of torque it can develop at its rated horsepower and speed, can be developed all the way down to zero speed.....Another way of putting it would be to say that if the motor can develop 400 foot-pounds of torque at 1000 RPM, it can do so all the way down to zero speed and hold itself still with a torque of 400 foot pounds. The motors and drives I deal with will actually hold their loads perfectly still while applying a desired amount of "Tension".Of course these motors have blowers that cool them, or they would smoke in a matter of minutes.Patrick
Reply:I saw that Harbor Freight has their 1 1/2 hp industrial drill press on sale now for $399 and it goes down to 150 RPM. Anybody have any experience with this machine good or bad?JimCut an MGB and widened 11" C4 Corvette suspension and LT1 Chevrolet power & 6 spd. Pictures here:Part 1http://forum.britishv8.org/read.php?13,7581Part 2http://forum.britishv8.org/read.php?13,22422
Reply:The Grizzly drill presses are sturdy, with good castings. Here's one that goes 140 rpm slowest: http://grizzly.com/products/12-Speed...ll-Press/G7944 for around $300. I just bought the 7948, for the bigger table. It's crude compared to the industrial USA machines, but quite a lot cheaper.Jim
Reply:Your a welder.  Switch to a larger pulley and make a new belt gaurd.I have one of the Taiwan floor standing drill presses and it's OK for hobby stuff.  I've had it for about 20 years now and worn out several belts with no real problem.  It has 16 speeds and slows down to 150rpm (or less).  If you buy one, take a square to check the quill for trueness to the table @ both X & Y axis, and at different quill/table heights.  I've found the cheaper ones can have poor QC in the basic machining.  You don't want to get stuck with something that drills crooked holes down the road.  You can adjust out left/right, but not fore/aft.Hobart 140 Handler w/ gasHyperTherm Powermax 380 Plasmaoxy/acetylene
Reply:I believe the next speed class AC induction motor would put you at around 900 RPM on the motor shaft.   That would likely be your simplest solution that is to get a low speed motor.   There is a problem in that the motor will likely be a different size and be of higher torque.Your next possibility is to simply add a jack shaft to go to a lower RPM.   This is not uncommon.A few warning about going the Variable frequency AC drive route.   The cheaper drives may not supply the low speed torque you desire.   Second; as has already been mentioned if you run the motor to slow heating problems develop.  Such drives are very good if you expect to vary speed over narrow ranges and keep the belt drive step pulleys.   If you want limited number of pulley steps and few belt changes you will have to up rate the motor by a substantial margin to get the torque you need a the lowest speeds.A variable Speed DC motor and drive might be a better choice in some instances.Ignore the higher end drives as they likely cost more than a dozen cheap import drill presses.   Very good performance can be had out of the latest technology though.You could look into a mechanical gear reducer.   There are a number of possibilities here if you can find something compact enough.   This of course puts a fixed reduction in your mechanical path.daveOriginally Posted by Brad BlazerJust be careful you don't put a twist in the splined spindle shaft with all of that torque.
Reply:Question to those of you who seem to know. I've seen a speed controler for routers advertised in one of the catalouges I get.http://http://www.mlcswoodworking.co.../speedcon.htmlWould somthing like this work on the drill press, or possibly other tools that you might want to reduce the speed on say a band saw? Never gave it much thought before, but if you can slow down a 3 1/4 HP router why not the drill press, or would you loose to much torque? Other problems I don't see?
Reply:You cannot use those single phase speed reducers or a frequency controller on a motor that has a start winding. There may be some single phase repulsion induction fan motors that you might get away with using a frequency controller. They do not have a start winding. But you would need a huge motor. But to use one of those little router variable speed things, you would also have to see how the rpm reducer, reduces the rpms. Sometimes they just cut out all or a portion of a half cycle of AC. That would not allow a repulsion induction motor to work, or work well. Some convert to DC output and just pulse shorter pulses. However it allows an AC/DC armature motor to function well. AC/DC armature motors will run well on pulsed DC, or straight DC. You can run a drill motor off your welder output. I would get a new center free wheeling pulley with a larger and smaller pulley on it. That will let you go slower and faster. You might have to adapt the housing a bit. Most drill presses suffer from a loose press shaft, that holds the chuck. When you punch through metal, instead of the chuck and shaft that holds it, staying where it is. It is loose so it drops just a fraction of an inch very quickly though, allowing the drill bit to screw into the work. This is why most individuals are hurt on a drill press. If you tighten that shaft, it will stop the drill bit from catching material 100 times more then if it is loose. It is like getting a new drill press. Some drill presses come loose. Almost like rejects. Sometimes you cannot tighten them. I throw them away. Someone mentioned that a frequency controller will give the motor the same torque at low end or high end. In reality if the motor was getting the proper length low hertz pulse it would create more torque if the motor was designed to run at those rpm's. Since the motor is not designed to run at those rpm's it will slip a lot when you put a 3/4" horse power load on it. Causing heat. In other words at say 1100 rpm to get 3/4 horse power you will need much more torque, then you would at 1760 rpm and 3/4 horse power. Almost like volts, amps and watts. So if you put a 3/4 horse power load, on the drill press while you have the rpm's turned down you will need to create much higher torque then the motor outputs normally to make 3/4 horse power.        Sincerely,             William McCormick
Reply:Originally Posted by William McCormick JrMost drill presses suffer from a loose press shaft, that holds the chuck. When you punch through metal, instead of the chuck and shaft that holds it, staying where it is. It is loose so it drops just a fraction of an inch very quickly though, allowing the drill bit to screw into the work. This is why most individuals are hurt on a drill press. If you tighten that shaft, it will stop the drill bit from catching material 100 times more then if it is loose. It is like getting a new drill press. Some drill presses come loose. Almost like rejects. Sometimes you cannot tighten them. I throw them away.                    William McCormick
Reply:Originally Posted by William McCormick JrMost drill presses suffer from a loose press shaft, that holds the chuck. When you punch through metal, instead of the chuck and shaft that holds it, staying where it is. It is loose so it drops just a fraction of an inch very quickly though, allowing the drill bit to screw into the work. This is why most individuals are hurt on a drill press. If you tighten that shaft, it will stop the drill bit from catching material 100 times more then if it is loose. It is like getting a new drill press. Some drill presses come loose. Almost like rejects. Sometimes you cannot tighten them. I throw them away. William McCormick
Reply:Originally Posted by WeldordieHey, William,I could be wrong, but I think what you attribute to, "...a loose press shaft,...which drops just a fraction of an inch,...allowing the drill bit to screw into the work...," does not accurately describe what actually happens.  With the constant downward force on the bit there really isn't any opportunity for a "loose press shaft" to drop.  But, what actually happens to cause a bit to bite and bind in the workpiece, is the deflection (bending) of the workpiece, which produces a greater angle of incidence between the cutting edge of the bit and the piece.  At the same time, the incident speed of the bit increases, unless force is reduced between the bit and the piece. Coincidentally, I have observed that, since I slowed the drilling speed down with a jackshaft, thus increasing torque, I have far fewer binding problems... the bit just blasts its way through the piece. Weldordie
Reply:Originally Posted by Jim StabeTell me more about tightening up the press shaft. I'm not sure what that is or how to adjust it.Thanks Jim
Reply:Originally Posted by William McCormick JrI have used a really large press and holding onto a 1/2" plate with my bare hand I was able to cut through it with a one inch drill bit. Sincerely,             William McCormick
Reply:Originally Posted by SandyFor those not familiar with the operations and dangers of drill presses, attempt the above only if you wish either part of your hand ripped off or your gut ripped open.
Reply:Originally Posted by William McCormick JrI have used a really large press and holding onto a 1/2" plate with my bare hand I was able to cut through it with a one inch drill bit. It is the solidity of the press shaft that makes that possible. And the fact that the drill press was so ridged and strong that there was no spring loading of the drill bit when it did penetrate. Using the older quality drill press was like night and day compared to newer presses. Most would not believe it.William McCormick
Reply:You would have to try an older more solid drill press to believe it. It goes rather slow or can go rather slow. You would have to have issues to lose your hand using it. Unless you get something stuck or your clothing stuck in the drill bit and were unable to shut it off. But slow speed believe it or not, because of the often incredible torque can actually add to the problem of catching, if the shaft is not firmly secured, and drops through at the end of the cut. We have a powerful drill press that got sloppy. Oh man it could hurt you even if you had stuff in a vise. Maybe worse, when the vise or position able table came your way. But the older stronger drill press when it punches through it just does not grab. I did it a couple times because I could not believe it. We have lost drill press technology, I have no doubts. I could not get the thing to grab. It just cuts. I really think the industrial nation is out to lunch. All it took was the weight of my hand on it to keep it from catching and raising up. Should you expect that it will always do that heck no. But this older style can do it again and again.  I would not even consider it with a new rather heavy duty drill press. I put things in a heavy vise. But they can still be thrown at you. The older machines shaft was securely held and the tension on it was adjustable. Have you ever seen how a drill while drilling will leave a kind of chattering like pattern in the hole you are drilling, if you stop halfway through. Even a good countersink will often ruin the finish in the hole. That is all because the chuck is not firmly held. It is dropping and bouncing in the cut. Stop that and it is almost make believe how you can drill steel.        Sincerely,             William McCormick
Reply:Although Permanent Magnet D.C. motors need to be better shielded from chips and have brushes which wear out, they are, along with their variable speed controls, free around here. The ones used on treadmills (Free on Craigslist!) are usually 1 to 1 1/2 hp with a maximum speed of 4500 to 5500 rpm, but a low end which is probably in the hundred rpm range.  The older versions are usually best as they use a rotary potentiometer for speed control, while newer ones use a digital control which is part of the main circuit board.I am currently adapting one to run a bandsaw.
Reply:I worked for an old fart that grafted a 4 speed bus transmission to his gaint drill press. the motor ended up 3 foot from the press and it was mounted way down low. There was no belt gaurds or anything. OSHA would freak if they ever saw it but it was handy and drilled like crazy.
Reply:Originally Posted by Jim StabeI saw that Harbor Freight has their 1 1/2 hp industrial drill press on sale now for $399 and it goes down to 150 RPM. Anybody have any experience with this machine good or bad?Jim
Reply:Originally Posted by platypus20I have one of their 20" floor standing drills, its fine, I've used it to drill thousand of holes, and the only real problem I had was the drive belts, they were junk, switch to the Fenner Drive link belts and have had no more problems. Like all HF products, you have to go over it with a fine tooth comb, on mine the spindle return spring wasn't hook up, a simple fix, and I also replaced the base bolts, as the threads looked very bad. All in all it has been a good purchase.Jack