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Surface Grinder Attachment Build

Discussion in 'Grinders' started by dancom, Feb 14, 2021.

  1. dancom

    dancom Dust Maker

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    Been watching some videos on YT of makers (James Keeting, Kevin McGovern, One Armed et al) who have been making Surface Grinder Attachments and decided to have a go. An innovation from Travis Wuertz of Wuertz Machine Works was on the market some time ago, but cost prohibitive at US$1,700. Not wanting to re-invent the wheel, I went One Arm's design and James' parts list. I wanted to be able to slant the slide for vertical use, or keep it 90° for horizontal use. I don't have a milling machine, so I had to be innovative to work around this.

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    I did some sketching in CAD based on the manufacturers dimensions.
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    Parts started arriving back in mid-January. Time to confirm some dimensions before cutting or drilling anything.
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    The sliding table is quite robust. In order to match the wheel to the chuck, I needed to raise the table exactly 0.5".
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    Mounting the slider to the table was the most problematic part of the build. I originally went with flat head M6 machine screws but the heads stick out and rub. I changed these to M6 socket head capscrews and recessed them.
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    Without a mill, the slots for the neodymium magnets is a chore. I made this little jig and used a router with a 3/8" carbide bit. It actually went better than I was expecting. Many slow passes, but I got there.
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    I made the 17 slots and touched them up with a file. Cleaned with acetone and epoxied the magnets in. The magnets are 10 mm, so they stay friction fit in the slots. Careful, it's easy to break these magnets as I learned from this process.

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    The bar magnets are 60 mm 2.23" long, so there is some stick-out which is annoying. I decided to pot them in with table top epoxy tinted with black leather dye. Sprung a little leak in my form, but it solidified before too much escaped.

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    Kind of ended up looking like this. Here I am "dressing" the face of the magnetic chuck to make it flat.
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    The chuck held very strong, crazy strong. Sliding off some 1/8" steel was arduous, so I made a plate from 1/8" aluminum and attached it with some stainless flathead screws. I dressed that down about a 1/32" more.
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    Just kissing the surface of some 416 SS.
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    Some blades that were heat treated last year got a flattening. I checked various points around the blade and they are within a couple thousandths. My caliper isn't the greatest, but I feel it will work just fine for my purposes.
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    All in all, this is a great addition to the shop and I still have all my arms and legs. Total build cost was about $580 and that includes the epoxy and a new bit for the router.

    If you have any questions, let me know.

    Cheers,

    Dan
     
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  2. FORGE

    FORGE Active Member

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    Great post and a great addition to your shop.
    Back in the day when I made everything from stainless it sure would be nice to take the scale off stock with a machine like this.
    Thank goodness the fellow I make Damascus with has access to a automatic grinder that will do up to 24 inches long, you just program it and basically walk away from it.

    Dan a parts list may be helpful to anyone wanting to build one of these.
     
  3. dancom

    dancom Dust Maker

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    Thanks Cal. Working on bill of materials and drawings. I am fitting a dial indicator on tonight.

    I didn't expect it to be super precision like a proper 2000 lbs surface grinder, but against the surfacing plate nothing is rocking. For the knifemaker these things really do the trick.

    I might recommend using some decent neodymium disc magnets where one could simply make a bunch of holes with a Forstner bit instead of making the slots.

    Dan
     
  4. Magnus

    Magnus Member

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    Nice work, Dan. I made something similar two years back using the same ali express parts and it still works very well. I find it really shines when flattening billets for welding or for a pre-hardening flattening. My chuck holds long items very well but has trouble with shorter items and thick sections, do you find something similar?

    Cheers,
    Magnus
     
  5. dancom

    dancom Dust Maker

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    Thanks Magnus. There are 17 magnets in there, spaced every 3/4" over 13". Before I put the aluminum skin on the chuck, I was ripping my fingernails trying to slide a piece of 1/8" steel off. The shortest piece I have put in there was about 1" x 3" and 3/16" thick and it held fine with a 36 grit belt. I think the secret is to not cut too deep on any single pass. Rather, take a few thou off each pass. I added a dial indicator so I can gauge approximately how much it is removing.
    [​IMG]

    Dan
     
  6. Magnus

    Magnus Member

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    similar set-up here, 20 magnets at 3/4" spacing. Maybe some of my magnets are upside down? I don't remember for sure but i think the poles were oriented along the long face. Or maybe i should be using a smaller contact wheel; that would make a difference too.

    Magnus
     
  7. dancom

    dancom Dust Maker

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    Distance is very important with magnetic fields as the inverse-square law is in effect. I sunk the magnets around 0.3" to 0.375" and ground down when dressing until the first magnet was exposed. They are close to the surface. The chuck isn't perfect, but the goal was to have all the magnets within 1/16" of the surface. As mine are potted in the epoxy, I couldn't see them very well when dressing the face, so I just kept going until the first bizarre sparks appeared. I found this closeness to be too sticky for thicker stock.

    I didn't know if there was a right way or a wrong way to orient the magnets as the faces seem to attract steel equally well. Being bar magnets the field is concentrated at the ends, but the faces still attract and repel very intensely. Nearly impossible to push the faces together with the same polarity. They simply flipped out of my fingers to they way they wanted to connect. Like no human as going to tell them what to do. :eek: And you know how they can violently attract to each other from an unexpected distance. I broke two magnets this way.

    I installed the first magnet, say North facing up, the the next one South facing up. This makes a N, S, N, S pattern of faces. They are very much wanting to pull out of the slot and leap on to their neighbours only 3/8" away. When I got the last magnet, odd number 17, I made the orientation the same as the previous, so I had the repelling faces up. In tests (empirical of course), I couldn't tell any difference in stickiness to steel at that end compared to the other end of the chuck.

    A word of caution: I understand that some elements in these magnets are pyrophoric. Meaning if the metal is powdered, it can spontaneously combust in air. So you don't want to be grinding or filing them. Combustion can occur up to 15 minutes after first being exposure to air.

    Dan
     
  8. Scott Kozub

    Scott Kozub Active Member

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    This is a very cool build. I was about to build one myself but I found a surface grinder on Kijiji for $400 and couldn't pass it up. I've been happily warping blades ever since. That's how they're supposed to work right?

    I'll be doing a belt conversion on it. The stones seem to generate too much heat (even after being dressed) and the thin stock swells making the stones generate more heat and then taco. It doesn't have coolant so I'm hoping a belt conversion will run cooler. It could be my technique but I'm not sure stones are the way to go on thin stock without coolant. I like those SGA's like your making.

    The guy selling the surface grinder also had a completely rebuilt mill for $5000.00 Thing was beautiful. He was closing a machine shop and he specialized in rebuilding machines. I tell you, had my wife not been in the truck I would have emptied the bank account that day.
     
  9. dancom

    dancom Dust Maker

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    Belts make sense. I like the fact that I can put any grit belt on. I was playing with a fine conditioning belt and that smooth, straight surface with even belt pressure is like nothing I could get before.
     
  10. Griff

    Griff Active Member

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    Dan would you say this is still a necessary piece of equipment for me even though I already have a variable speed disc grinder?
     
  11. dancom

    dancom Dust Maker

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    Griff,

    Probably my technique, but I am not able to get larger things perfectly flat on the disc. At least to my eye's satisfaction. There are too many variables, pressure, surface speed, condition of the paper. Small things like bolsters and scales are ok, but the length of chef's knife is tough on a 8-3/4" disc. I would normally use the flat platen and a magnet to hold the blade. A surface grinder holds everything tight and takes steel off in beautiful, even amounts down the whole length. I did my best to check for varying thicknesses with a digital caliper and it appears to be even to 0.002" or as close as I can measure. Also, if I shim the bottom stop, the whole chuck can become slightly angled. This makes tapering tangs easy and perfectly symmetrical to boot as long as you put the blade in the same place on the mag chuck. These things that can be done in other ways, but this contraption makes them a whole lot easier. The fact that it works with any 2x72" belt has me giddy. I was playing with VSM Ilumerons last night and wow the finish is stunning.

    Dan
     
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  12. Griff

    Griff Active Member

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    Awesome Dan! I have also been hearing good things about the VSM Llumerons too. Looking forward to trying them out:beer::beer:
     
  13. dancom

    dancom Dust Maker

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    For those that we're looking for a bill of materials and drawings for the surface grinder attachment I have made this. (It's from my blog.)


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    101 - Manual Slide Table PT-SD102P PT-SD102P Manual Slide Table QTY 1
    102- Slide SGB20-5UU Dual-axis linear guide 600mm SGR20 5 Rollers QTY 1
    103- Wheel 32585108444 100*50mm Solid, with 12.7 mm bearings installed QTY 1
    104- Tool arm Aluminum, 1.5" square x 24" *see note below QTY 1
    105- Chuck Aluminum, 1" x 2" x 16" QTY 1
    106- Chuck support Aluminum, 0.5" x 1.5" x 16" QTY 1
    107- Chuck slide base Aluminum, 0.5" x 2" x 16"QTY 1
    108- Chuck side Aluminum, 0.125" x 1" x 16" QTY 1
    109- Chuck face Aluminum, 0.125" x 2" x 16" QTY 1
    110- Handle Aluminum, 0.75" x 1" x 4.5" QTY 2
    111- Table riser ** Aluminum, 0.5" x 4" x 5" QTY 1
    112- Magnets B07T3PNB6H Neodymium bar magnet, 60 x 10 x 5 mm QTY 17
    113- Handle MH-3039 5/16"-18 Adjustable Handle QTY 2
    114- Dial Indicator, 0-1", 0.001" ALL-52000 Dial Indicator, 0-1", 0.001", lug mount QTY 1
    115- Table base Hot Rolled Steel, 0.5"x 4" x 9.5" QTY 1
    116- Axle bolt Socket Head Cap screw, 1/2"-13 x 4" QTY 1
    117- Jam Nut 1/2"-13 Jam Nut, Stainless QTY 2
    118- Machine screw 10-32 x 1/2" Flat Head, SS QTY 12
    119- Cap screw 1/4"-20 x 1.5" socket head cap screw QTY 3
    120- Cap screw 1/4"-20 x 1/2" socket head cap screw QTY 6
    122- Cap screw Socket head cap screw, M6-1.0 x 12 mm QTY 4
    123- Cap screw Flat head cap screw 3/8"-16 x 1-1/2" QTY 2
    124- Cap screw Flat head cap screw 1/4"-20 x 1" QTY 2
    125- Cap screw Flat head cap screw 1/4"-20 x 1/2" QTY 3
    126- Cap screw Hex head cap screw, 5/16"-18 x 1-1/2" QTY 2
    127- Flat washer Hex nut, 5/16" (handles/bumpers) QTY 2
    128- Bumper Rubber grommet, 1/4" ID, 1/2" OD QTY 4
    129- Stand off 3/8" Schedule 40 pipe, 1" QTY 4
    130- Cap screw Hex head cap screw, 1/4"-20 x 1-1/4" QTY 1
    131- Bracket Made bracket, 1/8" flat bar 1-1/4" QTY 1
    132- Machine screw 6-32 x 3/8" machine screw QTY 2

    *1 Length of tool arm may vary with different grinders.
    **Table riser will be the correct thickness to put the magnetic chuck in line with the wheel. On my grinder (Sayber OSG) this height is 1/2".

    A lot of these parts you can substitute, but I would recommend getting the correct parts for items 101 and 102.

    Regards,

    Dan
     
    Last edited: Mar 1, 2021
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  14. dancom

    dancom Dust Maker

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    Follow up to @Griff 's question. After using this a bit one soon realizes its inherent limitation. Works amazing on steel and 416 stainless. Not good on brass, copper, wood or any other non-ferrous material as the chuck is magnetic. Tried a few things like double sided tape, tape loops, CA glue etc. and that's kind of workable, but much easier just to slap those non-magnetic materials on the disc.

    So yes, however wonky, I am definitely still using the disc grinder.

    Dan
     

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