2x72" Belt Grinder as a Foundry-Related (Pattern-making) Tool

Discussion in 'Foundry tools and flasks' started by Melterskelter, Oct 4, 2021.

  1. Melterskelter

    Melterskelter Gold Banner Member

    Today I did a bit of a vibration test demo:

    The grinder is turning at just under 6000 feet per minute.

  2. Zapins

    Zapins Gold

    Man these grinders are super tempting to build. I'd love to have one. There is a plasma cutter shop nearby about 2 hr drive away I could probably have the patterns cut out if I had the 3d model plan. But the wheels are the part I don't want to spend a huge amount of cash on. I wonder if I could make my own on the lathe that would be any good?
    DavidF likes this.
  3. Melterskelter

    Melterskelter Gold Banner Member

    The guy who made the plans will supply CAD files for just that purpose. Thet is how our group had them laser cut. Plasma would be OK but realize plasma cut surfaces are darned hard---nitrided due to heat and atmosphere. Water jet would be better. He suplies paper templates in his plans download.

    The planms are dirt cheap for what you get. 30 bucks.

    Note: he sells metric and Imperial plans. They are each optimized for raw stock that is metric or imperial. Buy metric if you will use metric stock and Imperial if you will buy Imperial stock.

    You save a lot of time getting parts CNC cut. I have some thoughts about where to deviate from the plans too as I think there are some ways (that I implemented) that work better than a few things he suggested.

    Last edited: Nov 25, 2021
  4. Zapins

    Zapins Gold

    What about motor size? I'm guessing a faster >3,000 rpm motor in the 2 to 4 hp range would be best? I'd love to take some super aggressive cuts through metal. I've seen some bigger sanders made using go-cart wheels that really eat metal for breakfast.
  5. Melterskelter

    Melterskelter Gold Banner Member

    2 HP 3-phase 3750 that I will be over-driving to 4500 or so. It's induction so no moving coils. Will provide 6000 SFM on the belt.

  6. Zapins

    Zapins Gold

    Gotcha. I have a 1 or 1.5 hp 3750 motor in the shop that I salvaged. Might work always nice to have more power though.
  7. Melterskelter

    Melterskelter Gold Banner Member

    With respect to the motor you have, it may be adequate at 1.5 horses. But, if you use it, buy a VFD for a two, just in case. The cost difference is small. That way you can upgrade painlessly if needed now or the salvaged motor fails at some point.

  8. Melterskelter

    Melterskelter Gold Banner Member

    I have mentioned the fibrous nature of the swarf produced by the belt grinder in a couple places. Well, today I decided to get out a ten power magnifier and exam a somewhat cohesive mat not pile of swarf I made doing some grinding yesterday. I have no special macro photo gear so I just let my iPhone look through the magnifier. A rather marginal work-around but one that still produced a couple images that makes the point of how different the swarf produced by the belt grinder is compared to the granular stuff that comes off a snag wheel. The belt used was a Norton Blaze 60 grit.

    Here is an image of a mat of fibrous swarf suspended in mid air and holding together.

    And here is a magnified view of the swarf showing its fibrous nature. Magnifying the material first hand I can actually see little balls of steel on the ends of the fibers where the molten metal coalesced on the end of the fiber. Interesting.
    734D8FD0-C0A7-4D21-9B06-6289776323D6.jpeg 1DF59A5F-EE48-41F5-ADD8-B328AA08AE58.jpeg

    I found this material to be fascinating and quite unexpected. Probably very old hat for long-time BG users.

    Last edited: Dec 15, 2021
  9. I've seen the same from a surface grinder with a very coarse wheel on mild steel and thought about how steel wool get made.
  10. Melterskelter

    Melterskelter Gold Banner Member

    Recently boroko asked via conversation on my profile page me about the mods I made to the plans that I alluded to above.

    The biggest and most important change to NOT follow Jer’s recommended fabrication method for welding up the square sleeves or tubes the receive the square bars holding the table and platen/ contact wheels. For my first square sleeve I did follow his method. But, as I suspected, the contraction of the sleeve tack welds cause the sleeve to grab tenaciously onto the fixturing square bar. For the next square tube I bought a piece of larger flat bar and milled shoulders the accept the two sides of the tube. Now the welds could not draw the bars together as they were seated on the milled shoulders. Worked perfectly. I don’t see any way his method can result in anything other than a seized fixturing bar that has to be beaten, and I do mean furiously, beaten apart. Never again. Here is a pic of the tube fabrication method I strongly suggest: DA9A3264-CF12-4ED0-A947-81B867AEA5E0.jpeg

    You can see the the top and bottom bars have recesses milled into them to receive the upright side pieces. Once they are positioned, strategically located tack welds with frequent squareness checks will establish relative positions and simple good welding techniques will ensure good square and straight tubes. I allowed 15 thou clearance left and right and up and down. There is no reason to attempt close tolerances.

    I also changed his combination belt tensioning and tracking lever a bit. I made it 1.5 times longer and instead of using a nut to establish threads in it, I turned a 1.5” long drilled and tapped plug and welded it into a tube that knurled. The extra leverage is nice and the longer plug is just more stable and solider feeling.

    I am happy comment on any aspects of fabrication of this grinder. I use mine nearly daily and today, for instance, used it fifteen times. It is just plain great. It is a pleasure to use it. I use mainly the platen, though I made a 10” contact wheel and the small contact wheel attachments and occasionally use both. The two horse motor with VFD is perfect. I would *strongly* discourage attempted use of a DC treadmill motor. I tried it and, yes, it worked barely. But the treadmill motor setup does not even compare to the 3-phase 2HP with VFD. It just rips through metal when needed or slows to a quiet walk when “touch” is needed.

    If I think of other comments, I’ll add them.

    Last edited: Feb 8, 2022
    rocco and boroko like this.
  11. Melterskelter

    Melterskelter Gold Banner Member

    Here is a pic of the extended and beefed-lever:

    I also made a nice pull handle shown above for the base cabinet that attaches and detaches nicely and is convenient to use: 2F6F50CE-A9E2-43BE-A7AF-8E8406C45EEC.jpeg 5E51B3DD-5A91-4551-B7CC-C0BB55A7D43A.jpeg BBBF22C9-E664-46F5-A917-52730D0B1EA2.jpeg f

  12. rocco

    rocco Silver

    When I watched Jer's videos, I fairly impressed except when it came to those sleeves, I thought surely there must be a better way! How do you think you might have addressed the issue if you hadn't had ready access to a milling machine
  13. Melterskelter

    Melterskelter Gold Banner Member

    If I didn’t have a mill, I would buy heavy wall square tube of roughly comparable size and then find a slightly smaller bar or tube that would insert into the sleeve. Then I’d make shims for the inserted end of the bar and weld em to bar to make it a loose sliding fit in the sleeve. Adjustment of the maybe oversized shim with an angle grinder or file would be easy. Then fit shims to the mouth of the sleeve to make a loose sliding fit. Adjust them with a die grinder or file. The welded seam of the sleeve would have to be accounted for—-not hard. This might be a preferable method over welding in general. I went down the welding path as I had started that way and also, as the first builder of the machine amongst 35 folks who made a group buy of parts, I wanted to demonstrate the method was workable.

    The suggestion to use heavy tube really is not so much a strength issue, but, as Jer indicated, he designed the grinder with a lot of mass to reduce vibration. It’s a lot easier to make it heavy than it is to make and KEEP everything in perfect balance. Part of the pleasure in using the machine is it’s rock-solid feel and it’s smoothness of operation.

    BTW, if someone wanted to get a kit of laser-cut parts, I am pretty sure one or two of the group might sell their unused kits.

  14. crazybillybob

    crazybillybob Silver Banner Member

    I have the same plans and part of a sheet of 3/8" steel. Just need to get out to the shop and fire up the plasma. But currently there's too much snow between the house and the shop. Hopefully soon it will melt.
  15. Melterskelter

    Melterskelter Gold Banner Member

    How do you deal with ,machining the hard shell left by typical plasma cutting? It can be a bugger. The laser cut, on the other hand, was not noticeably hard.

  16. crazybillybob

    crazybillybob Silver Banner Member

    Normally I'm grinding and welding or sanding and painting stuff that comes off the plasma. But if I need to do bolt holes and such I make a pilot on the center and drill the holes to size. With this grinder I can oversize the lips and most of the machining will be under the nitrated layer (normally only .030-.050 thick). The little bit of plamsa cut stuff I've machined was kinda like machining hard chrome...Get under it and you don't have issues. Trying to plow through kills tooling. (and I have some cheap import carbide for those jobs).
    Melterskelter likes this.

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