Power drill torque vs spindle for CNC drilling?

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Thread: Power drill torque vs spindle for CNC drilling?

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    Question Power drill torque vs spindle for CNC drilling?

    Short version:

    Can a VFD controlled spindle produce enough torque in the 100-1000rpm range to drill like a power drill or drill press?


    Long version:

    I frequently find myself doing jobs where I need to accurately drill a number of holes (4-10mm diameter) in wood, MDF or sometimes aluminium or steel, and also 20mm-40mm diameter holes in wood (using Forstner bits). Instead of doing this with a drill press, I'd like to use my CNC machine.

    The CNC is a small/medium sized machine (an old K2 KG3925), approx 100kg total, aluminium extrusion frame, running a Porter Cable 890 router (claimed 2 1/4 HP). But, I generally avoid using it for simple drilling tasks as the router is very noisy, and tends to create way more dust than a drill.

    With a 10,000 rpm to 23,000 rpm speed range, the PC 890 router is obviously unsuited for drill and Forstner bits, but would a VFD controlled spindle create enough torque in the 100 rpm to 1,000 rpm range? There are a plenty of air cooled spindle + ER collet + VFD packages on eBay, in the 1.5kW to 2.2kW range.

    Alternatively, I could buy a cheap 600-1000W corded power drill, and mount it instead of the router, but a spindle would be preferable if it would work well below 1000 rpm.

    Anyone got experience of running such spindles at slow speeds?

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    Community Moderator Al_The_Man's Avatar
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    Default Re: Power drill torque vs spindle for CNC drilling?

    Mains powered hand tools in general use a Universal (series field) motors, these are very high torque motors, but essentially operate in a run away condition.
    This is the reason they are geared to obtain the lower RPM's.
    Without some added feature, they are hard to operate at a fixed rpm.
    There is one that was developed by a member here and it is marketed generally for router spindles, and it goes under the name of SuperPID unit.
    Routers are direct drive, so no reduction like the hand drill version, but use the same motor.
    Al.

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    Default Re: Power drill torque vs spindle for CNC drilling?

    Yea - my understanding is that single phase routers are just chopping the AC wave in order to produce reduced speeds (at the cost of losing torque). I know some routers have a "constant torque" type feature; which I believe is essentially what the SuperPID does - i.e. applying more power if the rpm drops below the requested speed.

    I was just wondering whether a 3 phase VFD controlled spindle would be able to generate sufficient torque when run in the 100-1000rpm range; but I guess they're probably just not intended for that. I could try to rig up some solution with a motor and gearbox, but obviously that already exists in a power drill. Maybe trying to mount a cheap drill is the way to go.



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    Default Re: Power drill torque vs spindle for CNC drilling?

    The SuperPID uses a the typical Triac control but with a optic sensor for feedback to a Microchip in order to maintain the set RPM.
    A VFD below 1Krpm will show some loss of torque, So make sure you source the vector control version, not the V/F cheaper version.
    The ideal way is either a gear box reduction or feedback control.
    For MDF or aluminum etc, I would not think you will have a problem, or any thing but large dia in steel.
    Al.

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    Default Re: Power drill torque vs spindle for CNC drilling?

    I was just wondering whether a 3 phase VFD controlled spindle would be able to generate sufficient torque when run in the 100-1000rpm range
    It's going to depend on the spindle or motor you choose. If you are talking about a 24,000 rpm spindle, then the answer is no.

    Even a 6000 rpm spindle like this has a minimum recommended speed of 2000rpm.
    GMT Air Cooled CNC Spindle 2.2 kW 220V / 380V 6000RPM S | Air Cooled Spindles

    Note that the forces required for drilling can be very high, especially when drilling steel, so the machine may not be rigid enough. And these spindles are not designed for high thrust loads, so the bearings may not last long.

    Gerry

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    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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    Default Re: Power drill torque vs spindle for CNC drilling?

    Quote Originally Posted by sploo View Post
    also 20mm-40mm diameter holes in wood (using Forstner bits).
    I would just mill these holes with a 1/4" bit - it's the kind of work CNC routers are made for. A direct drive spindle with enough torque for a 40mm Forstner bit is going to be unreasonably big.



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    Default Re: Power drill torque vs spindle for CNC drilling?

    Quote Originally Posted by CitizenOfDreams View Post
    I would just mill these holes with a 1/4" bit - it's the kind of work CNC routers are made for. A direct drive spindle with enough torque for a 40mm Forstner bit is going to be unreasonably big.
    The problem is: dust and noise (vs using a Forstner bit).

    That said, I've just ordered one of the Chinese VFD controlled spindles (air cooled rather than water), as a bit of research on the subject indicates even the air cooled models are still much quieter than routers, and (understandably) they're much stronger at lower rpm than an equivalent router. My little CNC machine isn't rigid enough to achieve speeds that would be ideal for the higher rpm of a router, so hopefully the spindle (running at a lower rpm) will be more suitable and a lot quieter. Not going to solve the dust problem though I guess, but at least it'll be an improvement.



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    Default Re: Power drill torque vs spindle for CNC drilling?

    The Chinese HS spindles cannot be ran lower than 6krpm otherwise you blow the drive or motor due to over-current.
    Al..

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    Default Re: Power drill torque vs spindle for CNC drilling?

    Quote Originally Posted by Al_The_Man View Post
    The Chinese HS spindles cannot be ran lower than 6krpm otherwise you blow the drive or motor due to over-current.
    Al..
    Yea, I'll park the idea of low rpm drilling for the moment. My router is 10k-23k, but tends to sound a bit rough lower than 16k. If I can run the spindle at 10k it'll be more suited for the feed speed of the machine, and I'm sure it'll be a whole load quieter than the router.

    Maybe I'll investigate mounting a power drill in the machine at some point.



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    Default Re: Power drill torque vs spindle for CNC drilling?

    An air cooled spindle is definitely an improvement compared to a router (truthfully, I do not understand why people use routers on CNC machines). But it's not going to help you with the "high torque @ low RPM" issue.



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    Default Re: Power drill torque vs spindle for CNC drilling?

    Quote Originally Posted by CitizenOfDreams View Post
    An air cooled spindle is definitely an improvement compared to a router (truthfully, I do not understand why people use routers on CNC machines).
    Two reasons: money and (available) information. At the time I bought the machine (circa 2006) there was a spindle option from the vendor, but it was very expensive. I looked at the Chinese spindles a few times over the years, but never had enough information to confirm they'd be an improvement that would be worth the time/effort/money. I've kinda been out of the loop with CNC stuff for quite a few years, and in that time, I see there's been plenty of YouTube "reviews" and comparisions.

    Quote Originally Posted by CitizenOfDreams View Post
    But it's not going to help you with the "high torque @ low RPM" issue.
    Indeed. That's probably going to require rigging up a power drill - though ironically a brushed power drill motor is pretty loud too. Maybe I'll just chuck a harmonic drive gearbox on the end of the spindle (joking).



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    Default Re: Power drill torque vs spindle for CNC drilling?

    Quote Originally Posted by sploo View Post
    Indeed. That's probably going to require rigging up a power drill - though ironically a brushed power drill motor is pretty loud too. Maybe I'll just chuck a harmonic drive gearbox on the end of the spindle (joking).
    Most of the reason for the being loud is the fact it is a Universal motor, gear train also.
    Some have used the 2.5hp-3hp DC Treadmill motors and controllers, they posses quite a bit of torque at low RPM, mainly due to the feedback incorporated.
    Two main types are SCR bridge type, or the little more refined PWM version for quiet operation.
    There is at least one T.M. free on most local sales sites.
    Al.

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    Default Re: Power drill torque vs spindle for CNC drilling?

    A treadmill motor could be an interesting idea. Certainly it's more likely to fit than trying to mount an induction motor and pulleys/belts on top of my little machine



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    Default Re: Power drill torque vs spindle for CNC drilling?

    On the subject of T.M.motors, they often have a flywheel that is threaded on to the shaft, this is why they specify a direction of rotation.
    It is usually desirable to remove the flywheel for most applications, so if reversing, a method has to be used to avoid a pulley inadvertently spinning off !!
    Al.

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    Default Re: Power drill torque vs spindle for CNC drilling?

    In many drills, motor power is measured in UWO, especially in Dewalt drills. For example, this blog https://top15products.com/tools/best-cordless-drill/ has said that some companies like Portable cable & Dewalt believe that UWO is the correct way to measure the power that's why they do not provide measurement in Nm or in-lbs.Is it correct? If yes, then why?



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Power drill torque vs spindle for CNC drilling?

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Power drill torque vs spindle for CNC drilling?