Dril Press

[coachgeo]

ok..... maybe someone in here knows.... maybe not.

I have a drill press and it's lowest RPM setting is 250. I see now that I might need to go as low as 150rpm.

Can I wire something in between the wall socket and the press's motor that when switched on would limit the power to the drill press thus reducing the RPM's. If so... what? Could this damage the motor? Would it even work cause I imagine the RPM would lower but so would the horse power.

[TxRedneck]

Yeah only thing I know of that would do this is a voltage limiter...but then even that would cause problems because youll burn out your motor. Basically the mootr will overcompenstte by pulling more amps due to the loss of volts. This inturn will burn the motor out. Ive seen this question posed before on differnt theories and it comes back to the same you would need a reducing gear from the motor to the output shaft. Not sure how you get that accomplished. IF its possible. Sorry cant be much help but good luck

[KEENAVV]

If it is belt driven you might get another drive pully and belt.

[TxRedneck]

that was kinda my idea but then it depends on the machine some have it some dont...even then I dont know how easy or fesible this is on your particular model if it does have a belt

[Sandy]

There's not a lot you can do with that particular type motor. A change of pulleys is the better avenue to explore. A lot of drill presses are set up for primarily wood working and something close to low end router speeds. For instance what is the top speed and how often do you use that? Seldom I'll bet.

[ctardi]

Sounds like a job for either new pulleyes or a Jack Shaft, or switching your drill to run on DC, with a DC motor.

[BBchevy396]

I had the same need a few years ago,.... I took the drive pulley on my crappy little craftsman drill, machined/ground off the smallest pulley, then brazed the smallest pulley I could find onto it, using a pilot shaft.
The thing crawls along perty slow now, enough for the bigger drills anyways. Hope it helps.

[falconblack]

There is also a unit called a speed controller that you can wire in which switches the hertz therefore slows the motor down as low as 20 rpm to it,s maximum.I use alot of the at work and find they are great and do not heat the motor windings at all due to a constant voltage.That is a bit expensive although cheaper than a new drill press.But if you have a belt drive there are adjustable pulleys you can buy which open up on threads and therefore letting the belt ride lower inside the pulley.

[coachgeo]

There is also a unit called a speed controller ..

Looks GREAT. I did a google search to get more info. Found some circuitry info on how to make them as well as some info for robotics etc. ALL of it was over my head. I didn't really see pricing info either.

Can anyone provide some more detaills on what type of speed controller to search for/buy? Specifications to look for? Etc. etc.

[awright]

coachgeo, you have several options to get low speeds on your drill press but the better methods require money or labor or both. It's hard to be very specific without knowledge of your present motor type and sheave setup.

Options that come to my mind include:

1) Install a VFD (Variable Frequency Drive) between your power source and the motor (but see precautions below).

2) Replace your present motor with an 1140 RPM (six-pole) motor. (Can be expensive.)

3) Install modified sheaves and/or an intermediate step-down pulley between the motor and the spindle. (Cheap, but crude.)

By far the most useful and versatile method of getting well controlled, widely adjustable, low speeds on your drill press is to install a VFD. This is also called a VSD (Variable Speed Drive) or a "Speed Controller." I highly recommend this solution, having installed a surplus VFD in my garage shop almost thirty years ago for about $200. I love it! I run a geared-head drilling machine, a 26" bandsaw, and a Bridgeport mill off it (one at a time). With it, I can drill 1" and larger holes in steel and use large diameter hole saws without burning the cutting edge.

The main problem (or advantage) is that most (or all) VFDs are designed to drive 3-phase motors. That is a problem and additional cost if your machine already has a single-phase motor, since you will have to replace the motor. However, it is a great advantage if you are buying surplus machines already equipped with 3-phase motors. Three-phase motors are typically cheaper and more reliable than single-phase motors of equal quality and rating. Three-phase motors are also ideally suited to VFDs, while single-phase motors might require special starting procedures because of the need to kick out the start winding centrifugal switch (and the possibility that the centrifugal switch would kick in if you run the motor too slowly). I don't know if VFDs are even made for single-phase motors. You can't simply use two lines of a 3-phase VFD to drive a single-phase motor because (if it worked at all) the VFD will sense a lost phase and shut down.

Another solution is to replace your 1725 RPM motor with an 1140 RPM motor, thus instantly reducing all speed settings to 0.66 of the original speeds. 1140 RPM motors have six poles, rather than the usual four poles and therefore run at 2/3 the usual speed. This would get your 250 RPM speed down to 165 RPM, but with no adjustability other than that built into your sheave arrangement. Due to their smaller demand and greater internal complexity, 1140 RPM motors tend to be more expensive than 1725 RPM motors. Be sure to get a motor that is designed to drive machinery, not a fan. Fan motors usually must be cooled by being mounted in the fan airstream.

Modification of the sheave arrangement can get you lower speeds, but it can be a hassle to design and install. One of the posters showed a photo of a sheave arrangement that can achieve lower speeds than the common dual stepped sheave arrangmement. It is by far the cheapest approach, but a hassle to design and install.

If you need the low speed only temporarily for one specific job, you might be able to install an oversize sheave on the drill spindle and a minimum size spindle on the motor. Feasibility depends on the design of the belt enclosure on your machine. It could also be very dangerous since the oversize sheave would be at your hair line. You will also have to do some creative machining to make an oversize sheave fit the special oversize spindle that contains the splined chuck spindle. Not a simple bolt-on substitution.

If it is at all within your budget, I recommend the VFD approach, even if you have to replace your motor. You will reap lots of benefits in the future.

By the way, the VFD avoids burning out your motor by reducing the motor voltage in proportion to the reduced motor drive frequency. If you were to reduce the frequency of the electrical drive to the motor without a proportional reduction in voltage, you would reach a point at which the steel would saturate magnetically. At that point, the current shoots up high enough to damage the motor or the drive and start things smoking. This voltage scaling feature is automatic in any VFD.

A year ago I got a 2 HP VFD on ebay for well under $100. They are getting pretty cheap for lower power units without all the digital programmability features. All you need is a VFD that lets you change the speed with a simple potentiometer setup Check out Grainger's catalog for motors, but I would try the surplus/salvage market or ebay for VFDs. Try Googling Servo Corporation or HSC Santa Clara.

Lots of luck.

awright

[awright]

Well, just after signing off the previous post, I tried Googling Servo and HSC. Not very helpful, but ask HSC about their VFDs. They are not a regular stock item, but they had several brand new fractional HP and larger VFDs a month ago. Note that you won't normally get installation instructions with a surplus/salvage or ebay purchase. If that is important to you, consider getting a new unit from someone that can give you support and advice.

I suggested Servo because that was the name of the surplus outfit I bought my VFD from thirty years ago, and they were still there a few years ago. I don't remember their exact name.

Good luck.

awright

[caosesvida]

awright, are you using at static converter for that or rotary? You don't have the unimaginable luxury of having three phase power in your shop do you?? OR does the vfd make the third phase for you?? good post!

[awright]

No, caosesvida, I don't have the uxury of 3-phase power to my shop. And yes, VFD always put out 3 phase power to the motor. (Maybe someone makes a VFD for 1-phase motors, but I don't know of them and it would be kind of silly, given the advantages of 3-phase motors.)

Some VFDs take single-phase input and some take 3-phase input. VFDs built for 3-phase input can often be used on single-phase input, but only with caution and with advice from the manufacturer. This is because the VFD simply rectifies the incoming power and stores it on a capacitor bank that powers the 3-phase inverter section. The problem is that 3-phase power provides smoother rectified power and can, therefore, use a smaller capacitor bank for the same amount of ripple that the larger capacitor bank in a single-phase unit achieves. So, if you supply the 3-phase unit with 1-phase power, the DC bus inside the unit will have excessive ripple, possibly messing up the delivered power or the electronics.

Some manufacturers say it is ok to provide their 3-phase units with 1-phase power (you just leave the third terminal unconnected), but usually the power rating of the unit must be derated by, perhaps, 30 percent.

All VFDs are static inverters. These are more than simple phase converters, as the frequency is variable. It would be impractical, cumbersome, and difficult to design a VFD using rotary converter

Got to go to lunch!

Have fun.

awright.

[Snobound]

This might suit your needs:
http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/speedcon.html
It is a router speed control that will handle up to 15amps. It should work as well on any AC motor as long as it is within it's current rating. I'm sure they make heavier duty ones if your drill press draws more than 15 amps. You can Google "router speed control" and get a lot of sources.

[Snobound]

Before you get this device... does your drill press have a capacitive start motor (Bump on the side of the motor a little largrer than a roll of quarters)? If so, this may not work for you. Anybody have any experience with this?

[coachgeo]

This gets better everyday!! Look forward to more input.

Also, anyone got a hair brain idea on figuring out/measuring RPM's after using a device such as these?

[awright]

No, Snobound, the router speed control is a simple chopper-type voltage control using an SCR or Triac to chop off part of the AC waveform, thereby controlling the average voltage. That type of control will work properly with brush-type motors like those in routers, but can burn out induction motors lacking brushes. The Universal motor used in routers, drills, etc. (that is, motors with brushes) can work on AC power of any (moderate) frequency or even DC power because their operating principle does not have any dependancy on the frequency of the power. Conversely, the rotor of an induction motor is dragged around its axis by the rotating magnetic field created by the AC power and the pole arrangement of the stator. The speed of an induction motor is, therefore, strongly dependent upon the power frequency and relatively weakly dependent on the voltage.

A chopper-type speed control eliminates part of the voltage waveform, thus controlling the average voltage in the chopped waveform, but it does not change the frequency of the power source. Thus, an induction motor used on a chopper is still trying to rotate at the speed of the rotating magnetic field (and would if the load did not pull down the speed), which is fixed by the power frequency and the number of poles in the motor, but it has been deprived of the power required to properly drive the load. The result will be excessive slip (difference between speed of the rotating field and the speed of the rotating rotor), possibly resulting in overheating and motor burnout.

The above is not absolute, as some induction motors (such as light-duty fan motors) are specially designed to operate as torque motors at high slip. Such motors can tolerate chopper-type control. But machine tool drive motors are rarely designed for that type of speed control.

The above discussion is applicable to both 1-phase and 3-phase motors. Centrifugal switches used in 1-phase induction motors (that's what the "click" is as the motor coasts down) add new complexities because if the centrifugal switch does not disconnect the "start" winding within a few seconds of applying power, the start winding can burn out because it is not designed for continuous operation. Starting the motor at reduced voltage can result in prolonged or continuous operation on the start winding and overheating. Note that this is also true of split-phase motors showing no capacitor case on the side of the motor body, but still having a start winding.

awright

[awright]

Here's a possible method of making crude speed measurements of your low-speed drill press spindle. This assumes that you don't want to spend money for a real tachometer or rev. counter.

Grip a small dowel (1/4" or so) in the drill press chuck. Make or obtain a disk about 6" in diameter (ideally with a rubber tire around the periphery), and poke or punch a small hole for an axle like another small dowel or a pin.

Turn on the drill press, press the rim of the disk against the dowel in the chuck, and measure the time for a mark on the periphery to make one or more complete rotations. Calculate or measure manually the number of rotations of the spindle for one rotation of the disk and calculate the speed of the spindle.

Have fun

awright

[Sandy]

Or you buy one of these.

http://www.mechanicaltachometer.com/

They used to make one that was nothing more than a dial indicator with a pointed rubber knob on the end. Put that rubber point into that little divot that is in the end of every motor or pulley shaft and read what it says. Maybe some old timer around you has one ......:)

[falconblack]

There is however one other way to slow your drill press fairly cheeply that is a four speed motor it goes from 1075 rpm to 600 rpm that should do the trick for you and the cost is alot less then the speed controller I mentioned earlier in this post.Which by the way does 3 phase or single phase motors.Just need to order the right one,they have been made for at least 10 years now.

[awright]

falconblack, can you describe the operating principle of the speed controller you are referring to? It sounds interesting and economical. Can you provide a link to information on it?

Thanks.

awright

[coachgeo]

... motor it goes from 1075 rpm to 600 rpm that should do the trick....RPM ranges? This brings up a question? What range of RPM would you be looking for in a home shop drill press when your primarliy dealing with fabricating large truck offroad vehicle roll cages. Minor suspension fabrication too.

I will be building/modifying a camper box for my Unimog also. A few other things too but if I have the right rpm range of a drill press to handle these Im sure it could handle the trampoline apparatis I want to build too. Right now I go down to 250rpm? Is that enough for these type projects? (assuming good drill bits)

[Cracker]

Our old Delta at work runs down to 150 RPM. Thats the speed its been set at for the past 20 years. As long as we keep the oil flowing and have a decently sharpened bit, it'll drill anything we can throw at it. 1" holes in 1" plate is the thickest Ive personally drilled on it. It just chugs right through.

[Sandy]

RPM ranges? This brings up a question? What range of RPM would you be looking for in a home shop drill press when your primarliy dealing with fabricating large truck offroad vehicle roll cages. Minor suspension fabrication too.

That's a tough one coach cuzz a lot of it is subject to preferences. I know there have been gazzillions of scientific studies done by every manufacturer of every tool bla bla bla and charts have been produced showing the ideal rpm for just about anything you want to do with a drill press------BUT every time this question gets asked it boils down to "here's what works for me" type answers. So apparently few approve of the charts :) .

I've got two drill presses one goes from about 140 to 3800, the other from 150 to 4200. I used (past tense) to do a lot of wood work and the mid ranges seem to be the sweet spot for general drilling and sanding. The high end works for psuedo routing, shaping and buffing. Just remember that when stuff happens, it happens fast at 3800.

With any of the metal work I've dealt with I prefer the very bottom end of the rpm scale. 2000 rpm would be a rarity for me and I could live without it. Especially with two drill presses. Sometimes I wished I could get down to under 100 rpm but I can't.

If I were to shop for a drill press now I would look at how slow it would go, horses and overall precision. Precision within the needs range of the hobby guy that is.

To put that into a one liner== as big and as solid and as slow as makes sense for your budget.

[awright]

Coachgeo, I don't know what materials and hole sizes are involved in roll cage and suspension work, but I agree with Sandy that you should go for the lowest possible speed capability in your drill press. Unless you are drilling holes in circuit boards, you will probably never run into a lack of high enough speeds.

Since I am too lazy to refer to Machinery's Handbook for appropriate drilling speeds for various drill diameters and materials, my personal, intuitive criterion is that if I see smoke from hot drilling fluid, I stop and lower my drilling speed. The thing that dulls drills is getting the outer corner of the drill tip too hot, and I figure that smoking fluid is telling me that I'm exceeding the ability of the drill to carry the heat away from that cutting edge. This is not based upon anything I've read or heard elsewhere, but it has worked well for me for quite a while. This may be too conservative if you are trying to maximize productivity in a volume production environment, but it works fine in my home shop.

awright

[TxRedneck]

Coachgeo, I don't know what materials and hole sizes are involved in roll cage and suspension work, but I agree with Sandy that you should go for the lowest possible speed capability in your drill press. Unless you are drilling holes in circuit boards, you will probably never run into a lack of high enough speeds.

Since I am too lazy to refer to Machinery's Handbook for appropriate drilling speeds for various drill diameters and materials, my personal, intuitive criterion is that if I see smoke from hot drilling fluid, I stop and lower my drilling speed. The thing that dulls drills is getting the outer corner of the drill tip too hot, and I figure that smoking fluid is telling me that I'm exceeding the ability of the drill to carry the heat away from that cutting edge. This is not based upon anything I've read or heard elsewhere, but it has worked well for me for quite a while. This may be too conservative if you are trying to maximize productivity in a volume production environment, but it works fine in my home shop.

awright

While not being able to quote any piece of literature I agree 100% with AW on this. Some folks feel that quality of cutting oil is very important as well. I tend to do like the soviets and just use more of lesser qualtiy. Doesnt always work best, but gets the job done when im in my own shop. As always, the rule of if theres smoke, there fire....where theres fire its likely cause Im gonna be pissed for screwin up a good bit :D

[falconblack]

I would agree with sandy the faster it turns the more dangerous it is.Back to drill speed mine goes to 150 rpm and that seems to work great on metal no burnin bits.What size motor on your drill press?What voltage?What amperage is on the name plate?I will try and fit you with a proper speed control through our wholesaler here in Canada.Or I can get you a two speed motor or even four speed if you need it.Shipping should not be bad depending where you are located.

[comp]

so what did you do ???

[coachgeo]

what did who do? I am ahead of myself sorry. I got to get a shop put together so I have a place to assemble the drill press and get at projects. Now I know that I have to also buy a speed controller of some sort to get best use of the drill press and bits.

Once I know the specifications of the machine I'll get ahold of falconblack and see what he can set me up with so I can drop speeds down another 100rpm

[comp]

Cool,let us know how it works