Building a Slow Speed Grinder (Carbide)

  1. mm289 Member

    Messages:
    608
    Dover, Kent
    Thanks @gaz1 hadn't thought of that - will have a think about it.:thumbup:

    Also looking at the polyurethane drive belts that can be cut to length and melted together - might be an easy way of making a belt, any experiences with these?

    Cheers,

    MM
     
  2. mm289 Member

    Messages:
    608
    Dover, Kent
    Its the Christmas hols so must be project time, :clapping: well lets face it we can't do much else:o

    So couple of evenings in the workshop on the slow speed grinder - slow because of how long its taking me to build it I think :laughing:

    Got the 6" slug of ali up onto the lathe and cleaned it up. Then machined it down to leave a boss that the diamond disc will slot onto.
    2020-12-20 18.37.34 (Medium).jpg
    2020-12-20 18.37.48 (Medium).jpg

    this is then ready to drill for the magnets and dowel pins to locate.

    The disc will be drilled and the end of the shaft tapped to allow me to mechanically secure the backing disc to the shaft itself, but the abrasive disc will just be held on with the magnets.

    Now needed to make a second pulley for the other end of the "layshaft". Originally I was going to just do a matching pulley for the one on the motor but to give 300RPM at the disc this would mean running the motor at 20Hz. Its "normal" RPM is 720 I think so I did a bit of calculating and decided to make a slightly bigger pulley for the layshaft. 35mm vs 20mm for the motor will allow me to run the motor at about 80-90% Hz so should run much smoother and cooler.

    Dug out a slug from the box of offcuts I bought of Pressbrake and mounted in lathe.
    2020-12-21 18.05.04 (Medium).jpg

    Cleaned up then cut down to size on the bandsaw.

    After a bit of playing around ended up with this.
    2020-12-21 22.35.10 (Medium).jpg
    And then machined down the end of the shaft so that the pulley fits up against a flange on the shaft. The shaft will then be drilled and tapped and the pulley held in place by bolting up against the flange.

    2020-12-21 22.35.14 (Medium).jpg

    So - a little bit further on :clapping:

    Cheers,

    MM
     
  3. Pete.

    Pete. Member

    Messages:
    9,813
    Location:
    Kent, UK
    Make sure you leave a couple of mm of the disc showing on the edge so that you can pick it off easily when the magnets are fitted.Perhaps a small bevel right on the corner under the lip.
     
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  4. mm289 Member

    Messages:
    608
    Dover, Kent
    :thumbup: I have slightly bevelled the edge but will probably cut it a couple of screwdriver blade sized slots. Need to strip down and old hard drive to see if it has any decent small magnets in it next :laughing:

    Cheers,

    MM
     
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  5. RichardM Member

    Belt tension - how are you going to mount the motor?

    Flange to a flat plate which is slotted on the edges and mounts onto the angle iron uprights allowing movement for belt tension.
     
  6. mm289 Member

    Messages:
    608
    Dover, Kent
    Good question @RichardM There is no obvious way to mount the motor as it has no feet. There are some tapped holes on the end flanges where the reduction box and speed sensor mounted so i could make some brackets to attach to those. The other idea was to "strap" it down to the deck.

    Neither of which lend themselves to adjustability........

    I am going to try a 6mm polyurethane belt which can cut to length which may take away the tensioning issue.

    The alternative thought is as suggested by @gaz1 to use a tensioner pulley arrangement to the side.

    That's the fun of projects - always a puzzle to be solved:doh:

    Cheers,

    MM
     
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  7. striker Member

    Messages:
    490
    middlesbrough
    Can you fit a power twist linked v belt? You just remove links to tension. I've just fitted one to my mill drill. See vfd advice sought thread
     
  8. mm289 Member

    Messages:
    608
    Dover, Kent
    Will see how I get on with the polyurethane belt first but thanks for the suggestion.:thumbup:

    Cracked on with the motor mounting this afternoon after a bit of a tidy up. Decided to make up some plates that will mount to the pre drilled holes on the motor body where the reduction box and sensor were.

    Use a cardboard template to transfer the rough shape to some 2mm sheet and then filed it till it was a good fit to the flange on the front. Only 3 mounting points on the back so drilled out a hole for the shaft end so I could use all 3 points.

    Then had to try and drill all the holes in the right place :doh:

    2020-12-23 15.23.35 (Medium).jpg 2020-12-23 15.23.41 (Medium).jpg

    Got there in the end. Then used the folder to put a 90 degree bend having measured up to make sure it was in the right place to allow the motor to sit flat.

    2020-12-23 15.56.37 (Medium).jpg 2020-12-23 15.56.40 (Medium).jpg

    Works quite nicely and all measured so it fits onto the bottom plate snugly and allows room for the VFD behind.

    Drilled and tapped the shaft and secured the pulley I made yesterday then mocked up the fitment

    2020-12-23 15.57.15 (Medium).jpg

    With the layshaft in place I could line everything up and drill the holes in the base plate and fix down the motor.

    The pillow bearings are on slotted mountings so when I do the final fit I can shim/adjust as necessary to get everything lined up properly.

    2020-12-23 16.55.44 (Medium).jpg

    And with the VFD in place.

    2020-12-23 15.57.20 (Medium).jpg

    Next job is to work out the electrical connections. Rather than use a stop/start setup I have a 2 pole on/off switch which I am hoping to use but I need to figure out of I can use that with the switching circuit of the VFD:dontknow:

    Time for some reading;)

    Cheers,

    MM
     
  9. Spark plug

    Spark plug Member

    Messages:
    3,779
    Location:
    Durham, England
    You’ll be fine with the polly belt, it works on my grinder, it transmits plenty drive for lapping carbide.

    Still need to finish the tool rest, but it works so who knows when that will happen:

    E712EB2B-A7ED-437E-BAF9-FAFA67C2716F.jpeg
     
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  10. RichardM Member

    Mount.png


    Make a plate to mount it from the end, slot the plate and drill the uprights for adjustment.
     
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  11. Pete.

    Pete. Member

    Messages:
    9,813
    Location:
    Kent, UK
    My grinder used a normal o-ring or about 5mm section to drive the disc. they don't need a lot of power, I think mine is 250w.
     
    mm289 likes this.
  12. mm289 Member

    Messages:
    608
    Dover, Kent
    SO did the final bit before the Christmas break and got the electrics sorted.

    Eventually figured how to wire up the VFD to operate of a simple switch for stop start and rigged up a pot so I can control speed if I need to.

    The VFD was about figuring out the config options to enable remote control rather than the onboard keypad, got there in the end.

    Now all connected and ready to start putting the body on. First pic was in test mode, then tidied up the cabling a bit before locking down.

    2020-12-24 16.33.09 (Medium).jpg 2020-12-24 17.52.05 (Medium).jpg

    Cheers,

    MM
     
    daleyd likes this.
  13. mm289 Member

    Messages:
    608
    Dover, Kent
    With the electrics sorted I could now start on the casing. Off to the box pan folder and raiding my collection of sheet steel and knocked up a 1 piece wrap for the sides/top and an end piece for the front.
    2020-12-27 19.17.38 (Medium).jpg 2020-12-27 19.17.28 (Medium).jpg

    I've put a solid piece on the front to minimise dust getting into the motor enclosure. Also fitted the potentiometer and start stop switch.

    The belt end will probably just have some mesh on it so I can see what's going on with the belt and gain easy access.... not decided yet.
    2020-12-27 19.17.45 (Medium).jpg
    It will all get pulled apart again when I am finished for some final fettling and paint before final assembly but thats a bit of a way off yet. Now waiting for the poly belt to arrive so I can get everything trued up and locked down. :clapping:

    Cheers,

    MM
     
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  14. ukracer Forum Supporter

    I have too many grinders so I don't need to build another but I do need a way to make them all useable.

    This might also assist the op if he decides to make more. ;)

     
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  15. mm289 Member

    Messages:
    608
    Dover, Kent
    Next up was building the tool rest for the scraper blades.

    Am using a couple of slugs of ally as the mounts for an adjustable plate and as the mill is out of action decided to run them up on the shaper.

    First though I had bought an old Astra vice for the shaper as all my other vices weren't man enough to hold work pieces properly. So set up the vice and trammed it to get the box true. Then decided to clean up the vice from the previous witness marks.

    It started at lot worse than this

    2020-12-30 18.04.27 (Medium).jpg

    and ended up looking a lot better
    2020-12-30 18.34.02 (Medium).jpg

    Knowing the top of the jaws are within a few thou of true makes it easier to mount work IMHO.

    Then mounted the back plate to the shaft and that is running with only about 5 thou runout at the edge so well pleased with that as well.

    And cut a piece of plate that will be mounted between the two ally legs as mocked up here.
    2020-12-30 20.12.36 (Medium).jpg 2020-12-30 20.12.41 (Medium).jpg

    Doing this whilst waiting for the poly belt to arrive :whistle:

    Cheers,

    MM
     
  16. mm289 Member

    Messages:
    608
    Dover, Kent
    So, pretty much got this finished this afternoon. Nice peaceful day chuntering about in the shed:clapping:

    Finished of machining the two supports for the tool support and then drilled holes in the mounting plate for the magnets. Super glued them in, which is only looking partly successful at the moment as the superglue wont go off:doh:

    Then shimmed the layshaft mountings, assembled all the case, fixed a gland for the power cable and yes, the poly belt arrived in the post, so was able to put it all together:clapping:

    Had to wrap the bottom pulley in masking tape to give the belt a bit more grip as it was spinning but seems to be working now.

    And here it is - ta da.
    2020-12-31 17.56.08 (Medium).jpg 2020-12-31 17.56.14 (Medium).jpg
    2020-12-31 17.56.18 (Medium).jpg 2020-12-31 17.56.27 (Medium).jpg

    Set at 300rpm but will run up to 500rpm if needed. Still a bit of fettling to do and will probably pull apart to paint at some point, but had a quick go with one of my hand scrapers and put a lovely edge on it, so well pleased.

    MIGHT be able to get on with finishing a Biax or two now I can sharpen some blades to test them:whistle:

    Cheers,

    MM
     
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  17. Shox Dr

    Shox Dr Chief Engineer to Carlos Fandango

    Messages:
    16,028
    Location:
    East Yorkshire
    Nice project.

    Ive got this 4pole 3ph Mitsubishi motor for just this purpose. Only 90w. I dug it out last night and Jerry rigged it up to a VFD with a pot. Data plate doesn’t give an RPM, a quick check shows 1500rpm
    image.jpg

    Not seen a motor like this before, very smooth and well balanced, doesnt budge on start up, or have the slightest vibration. Slowing it down to 300rpm and its still difficult to stop by hand. So I’m going direct drive.

    Can you get the diamond discs in the UK, I don’t fancy ordering from outside
     
    daleyd likes this.
  18. mm289 Member

    Messages:
    608
    Dover, Kent
    looks good, should be ideal. Are you going to mount direct to shaft or use a layshaft?

    I haven't seen a UK supplier, all the links I have seen on ebay are for Chinese, but that doesn't mean they aren't around. Might need some googlfu though :laughing:

    Cheers

    MM
     
  19. pawsnizzy

    pawsnizzy Forum Supporter

    Messages:
    158
    Location:
    Derby, UK
    If you find any disks in the UK, they'll, no doubt be from China but at a premium:(
     
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  20. Pete.

    Pete. Member

    Messages:
    9,813
    Location:
    Kent, UK
    I've got some 100mm disks I'll send you one Dave.
     
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