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    Converting Drill Press to Variable Speed

    First, I am not trying to optimize for cost or whatever here, but just having some fun with one of my home workshop's tools which gets periodic use. If I was really concerned, I would just go buy a factory VS drill press. This is mostly for fun and to see what all I can do (much like most of us and our E30's).

    The press is an older Delta 12 speed from the mid 1990's, model 70-200. A couple of years ago I picked it up on Craigslist for cheap, and then spent a month pulling it completely apart to de-rust everything, press in all new spindle bearings and put proper lubrication on all sliding surfaces. The keyless chuck I picked up on McMaster cost almost as much as what i got the whole thing for lol, and after the rebuild I was indicating <0.001" runout on the spindle. So, more than good enough for a home shop drill press. That reminds me that I was going to post a rebuild-pics thread on here.....

    Anyway, the belt changing is annoying, and the speed range is sort of limiting. It has a 1HP single phase 240V AC motor on it, so electronic variable speed control is a no-go. I have been looking at options, and there are a few routes to go with this.

    1) Find a used 3Ph motor and run it on a VFD. 3Ph motors have marginally-OK variable torque characteristics as speed if varied, and are about as quiet as a single phase AC motor. The non-linear torque curve is a no-go though.

    2) Brushed DC motor. There are "2HP" treadmill motors all over eBay and stuff for cheap, and some guys out there have used them to make VS drill presses and bandsaws. Some come with the treadmill speed control boards, of which many seem to be standard and are documented to varying degrees. They are all SCR-based controls, which I dislike because they are noisy, both electrically and acoustically. Brushed motors are already noisier than AC motors, and an SCR control would not help. There are some PWM controllers for DC motors out there for under $400, so that would make it a little better. Brushed DC motors have decent speed-torque curves.

    3) Brushless DC motor. There are plenty of 1000-2000W "rated" BLDC motors with Hall sensors out there new for decent prices, and the speed controllers are cheap'ish (reversing ones with closed-loop operation). I'd just need a beefy 48V AC-DC converter, which is not too hard to find. BLDC motors seem to have some of the best torque-speed characteristics of the various motors types out there, and they are fairly quiet.

    Right now I am leaning toward option 3. A local store has some $150 BLDC motors rated for 48V input and 1600W output, with integrated Hall effect sensors on all 3 phases. The original AC motor is ~750W (1HP), but it delivers a bit more torque at its rated RPM, so I need something rated a bit higher. They also sell a $100 speed control which supports forward+reverse operation and braking (and braking is SUPER useful when drilling dozens of holes with material setup in between). The motor and stuff are these (no affiliation to the business, etc):
    https://electricscooterparts.com/motors48volt.html Item # MOT-481600BLDC
    https://electricscooterparts.com/spe...ers48volt.html Item # SPD-481500BLDC
    https://www.alliedelec.com/product/m...0-48/70230351/ - 1500W 240VAC to 48VDC power supply

    I can machine up all of the necessary mounting brackets and stuff. Right now it has an intermediate pulley and uses 2 V-belts. I think that I should be able to just run a single longer belt between the motor and spindle pulley. The ratios possible in this conversion with the stock pulleys are not really optimal since they would be lower than 1:1 (spindle speed < motor speed), and I am really shooting for up to a 5000RPM spindle speed for when I want to drill really small holes in PCBs and aluminum. McMaster sells V-belt pulleys, so I could machine an motor shaft adapter for the one I need to work with the spindle pulley's smallest slot, and then machine off as much of it (the giant triple spindle pulley) as I can to reduce the amount of mass the motor has to accel/decelerate. The whole thing will have more than enough inertia for smooth operation, and I can get it balanced if needed at a local shop.

    Thoughts? If this somehow works out well, I am doing the same thing to my Powermatic bandsaw. The blade speed is high for cutting wood, but it would be the bee's knees to be able to run metal on it too.

    #2
    Just for kicks, here's a brief summary of the drill press story.

    It was living in a retired model maker's basement, in a coastal area with a lot of rain.




    It was fully stripped and everything was cleaned over the course of a few weeks. The small bits went into jugs of white vinegar, and the larger pieces were soaked/scrubbed in a concrete mixing tub that I filled with vinegar. The acid is mild and does not mess things up, and since I was not in a big hurry, it was fine to let it do its work on the rust over time. Also, brass brushes and window scrapers were key.




    The spindle (above) got all new SKF bearings, as did the motor. It was pretty gross inside, full of sawdust. It also needed a new starting capacitor.




    Here it is reassembled.




    With a shiny new keyless chuck.




    I later rewired it for 240V and stuck a 15ft 10ga SJOOW cord on it. The casting which holds the handles was all stripped out, so I bored the holes out to the next larger thread size and turned some new ones. McMaster knobs in red were the finishing touch.




    So this is the thing I am thinking of wasting a bunch of money on to make it into a variable speed system.

    Comment


      #3
      i have the solution for you.

      toss that motor in the trash. go buy a used treadmill off craigslist for 100 bucks or less.

      take out the motor(about 1 horsepower) and the controller. there are tons of videos on youtube that show you how to make this work. they are mostly geared toward lathes but you are a smart guy so you can adapt it to this project with ease.

      here is a youtube vid of my mini lathe/mill that i repowered with a DC permenant magnet motor.

      https://youtu.be/drbiL399Yr0

      in my case, i bought the motor and controller new off ebay. i have about 120.00 invested in the complete conversion.
      sigpic
      Gigitty Gigitty!!!!

      88 cabrio becoming alpina b6 3.5s transplanted s62
      92 Mtech 2 cabrio alpinweiss 770 code
      88 325ix coupe manual lachsilber/cardinal
      88 325ix coupe manual diamondschwartz/natur
      87 e30 m3 for parts lachsilber/cardinal(serial number 7)
      12 135i M sport cabrio grey/black

      Comment


        #4
        really nice restoration by the way!
        sigpic
        Gigitty Gigitty!!!!

        88 cabrio becoming alpina b6 3.5s transplanted s62
        92 Mtech 2 cabrio alpinweiss 770 code
        88 325ix coupe manual lachsilber/cardinal
        88 325ix coupe manual diamondschwartz/natur
        87 e30 m3 for parts lachsilber/cardinal(serial number 7)
        12 135i M sport cabrio grey/black

        Comment


          #5
          Originally posted by flyboyx View Post
          Way too cool, I gotta look into this!
          sigpic

          Comment


            #6
            I ain't gonna lie, this is dope.
            Si vis pacem, para bellum.

            New Hawtness: 1995 540i/6 Claptrap
            Defunct too: Cirrusblau m30 Project
            Defunct (sold): Alta Vista

            79 Bronco SHTF Build

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              #7
              Cleaned up really nicely
              Buy Replacement Tweeter Pins!
              Feedback Here

              Comment


                #8
                Originally posted by flyboyx View Post
                i have the solution for you.

                toss that motor in the trash. go buy a used treadmill off craigslist for 100 bucks or less.

                take out the motor(about 1 horsepower) and the controller. there are tons of videos on youtube that show you how to make this work. they are mostly geared toward lathes but you are a smart guy so you can adapt it to this project with ease.

                here is a youtube vid of my mini lathe/mill that i repowered with a DC permenant magnet motor.

                https://youtu.be/drbiL399Yr0

                in my case, i bought the motor and controller new off ebay. i have about 120.00 invested in the complete conversion.
                Nice! Yeah the treadmill motors were one of my first considerations. I was sort of afraid that the brushed motors would be noisy, particularly with an SCR type speed control (which is what all of the treadmill controls are for the most part). Is most of the noise in your video the spindle bearings?

                Comment


                  #9
                  I mean.... you are using the tool in your shop and not in church....so.... honestly, the noise is inconsequential. It is much quieter than the induction motor that came with the tool. The tread motor will be quieter than your original also.

                  My point is that using sound level as a primary consideration seems a bit silly in my opinion.

                  It is infinitely more powerful. This particular example is a 1/7hp pma. It produces more than enough power at the slowest speed to where I couldn’t even think about stalling it. The original single speed induction was rated at 1/10th hp and could easily be stopped by pushing a cutting tool a little too deep into the stock. It is literally night and day.

                  If you decide to go pma, you can save a ton of money by buying a used mill and you will be thrilled once you are done
                  sigpic
                  Gigitty Gigitty!!!!

                  88 cabrio becoming alpina b6 3.5s transplanted s62
                  92 Mtech 2 cabrio alpinweiss 770 code
                  88 325ix coupe manual lachsilber/cardinal
                  88 325ix coupe manual diamondschwartz/natur
                  87 e30 m3 for parts lachsilber/cardinal(serial number 7)
                  12 135i M sport cabrio grey/black

                  Comment


                    #10
                    I literally just bought an 80's-vintage drill press the same day you started this thread and was already thinking about variable speed control.

                    I'd be more concerned about a treadmill motor not having enough power. 1/2hp on a drill press is not a lot. I'd shoot for a full 1hp. Go big or go home.
                    sigpic

                    Comment


                      #11
                      Hmmmm, i was unaware of this possibility.

                      I have a good American made Rockwell drill press and my only gripe is that i can't slow the spindle down enough and i also have a pretty heavy duty treadmill that could be a donor...

                      Time to check the HP rating of the treadmill.
                      Lorin


                      Originally posted by slammin.e28
                      The M30 is God's engine.

                      Comment


                        #12
                        Most of the treadmill motors that I have seen are rated at somewhere between 1.5 & 4HP. "Rated" anyway. Even if they can only reliably deliver half of what is on the nameplate/sticker, it's probably more than the stock motor.

                        I am not super concerned with noise, I was just thinking that it would be cool to run this as quiet as possible. But then again, it is likely not worth the extra $350 to run a big brushless when eBay can get me a motor and controller for <$200. So maybe I will go for the eBay conversion first and see how it does. Worst case, I don't like it and I re-sell it on eBay, and make the BLDC one.

                        I just pulled the trigger on the setup below even though I may have been able to piece something like this together for a little less, but having a working motor and control all in one shot was easy. The control panel will be discarded and I'll just program up my own PWM control with a microcontroller. I want to have a tachometer and segmented LED readout, so it was going to need it anyway. I may even experiment with closed-loop RPM control!

                        https://www.ebay.com/itm/323840930455

                        Comment


                          #13
                          I think you made a good choice going this route. i am kinda surprised that you purchased the parts off ebay when they are so readily availible to you locally.

                          https://sfbay.craigslist.org/scz/spo...935428322.html

                          https://sfbay.craigslist.org/pen/zip...935314644.html

                          https://sfbay.craigslist.org/eby/for...934989502.html

                          https://sfbay.craigslist.org/sby/spo...928302480.html

                          https://sfbay.craigslist.org/eby/spo...934834173.html

                          https://sfbay.craigslist.org/nby/spo...934758782.html

                          https://sfbay.craigslist.org/eby/spo...934063194.html

                          Andrew: to be clear, i used a 1/7hp motor on my mini lathe. bmwman is correct. treadmills have motors that are in excess of 1 horsepower but the comparison to an induction motor is not equal. the DC version makes so much more torque. this is why they are used in treadmill applications in the first place. think of some 400 lb fat fucker jumping on that thing trying to walk up a 6 degree incline.....
                          sigpic
                          Gigitty Gigitty!!!!

                          88 cabrio becoming alpina b6 3.5s transplanted s62
                          92 Mtech 2 cabrio alpinweiss 770 code
                          88 325ix coupe manual lachsilber/cardinal
                          88 325ix coupe manual diamondschwartz/natur
                          87 e30 m3 for parts lachsilber/cardinal(serial number 7)
                          12 135i M sport cabrio grey/black

                          Comment


                            #14
                            for example: a 12v starter is a DC permenant magnent motor. think about how much torque those things produce is such a small package. the problem with using a starter is that it isn't designed for continuous duty. they heat up too fast.
                            sigpic
                            Gigitty Gigitty!!!!

                            88 cabrio becoming alpina b6 3.5s transplanted s62
                            92 Mtech 2 cabrio alpinweiss 770 code
                            88 325ix coupe manual lachsilber/cardinal
                            88 325ix coupe manual diamondschwartz/natur
                            87 e30 m3 for parts lachsilber/cardinal(serial number 7)
                            12 135i M sport cabrio grey/black

                            Comment


                              #15
                              I am off to hunt for an old drill press now.....

                              Thanks!

                              P.S. Excellent work on the restoration.
                              My previous build (currently E30-less)
                              http://www.r3vlimited.com/board/showthread.php?t=170390

                              A 2016 Toyota Tacoma TRD 4x4 Offroad in Inferno is my newest obsession

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