2x72 belt grinder build

rabler

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Started building a 2x72 belt grinder. I've got the model in FreeCad done, here's a thumbnail picture of the model:
full-model.jpeg



This is composed of about 16 parts in Freecad, assembled with A2plus Assembly workbench (File belt-grinder-assembly.FCStd). I used simple rotate/translate in the assembly rather than relative constraints, I tried the constraints but changes broke to much. I may try Assembly4 for future projects. This is still a learning process. The (pink) base is set up so that it can pivot to a horizontal configuration to be used as an edge sander, the arm with the table under the platen rotates appropriately. Design includes a disc sander off the side because I could. If anyone is interested, the design files are attached, but it might be prudent to wait until I'm done to see what works/doesn't work with this design. Some of the hardware detail is missing, I didn't add all the bolts and pivot pins, etc, to the drawing, just gets to be too much detail. Also I'm doing some welding to put this together. The CAD design includes holes used as weld pockets, which I like to use as they seem a little easier to retain alignment.
 

Attachments

  • .25-handle.FCStd
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  • .38-handle.FCStd
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  • belt-grinder-assembly.FCStd
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  • centering-adjust.FCStd
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  • disc.FCStd
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  • discarm1.FCStd
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  • disctable.FCStd
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  • drivepully.FCStd
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  • gas-cylinder.FCStd
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  • grinder-motor-base2.FCStd
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  • motor.FCStd
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  • pivot-base.FCStd
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  • platten.FCStd
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  • plattenarm.FCStd
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  • plattenbase.FCStd
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  • roller.FCStd
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  • spring-arm.FCStd
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  • table.FCStd
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  • table-arm.FCStd
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larry4406

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Nice project! I am following you along.

The pivot point below the motor on the pin/shaft would seem to be well below the center of gravity of the unit making tipping over more difficult. Maybe extend the pivot points upward and use two separate arbors/pins?
 

rabler

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The pivot point below the motor on the pin/shaft would seem to be well below the center of gravity of the unit making tipping over more difficult. Maybe extend the pivot points upward and use two separate arbors/pins?
That might be a good change, it is going to be fairly heavy. On the other hand I want it to be fairly stable in either position, although there will also be a spring pin in the base to keep it from pivoting. I'll let you know when it's done.
 

rabler

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Here's a PDF of all the TechDraw shop diagrams. I don't use the classic drawing frame and footer so admittedly not the easiest to follow. There are some minor inconsistencies here, mostly with matching hole diameters for pins/bolts, so revisions are expected.
 

Attachments

  • beltgrinder-combined.pdf
    327 KB · Views: 36

brino

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Watching this build.
Thanks for sharing!
Brian
 

kolbroshop

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wow, you have put remarkable amount of work in it. Just WOW. Will be folowing this build....
 

rabler

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Here's the first part I'm working on. It is the main body of this and certainly the most complicated. This is actually 7 separate pieces of metal, to be welded together. I've already made the main backplate and the two pivot arms, next need to work on the slide supports for the platen arms and table. I'll grab some shop pictures of what this looks like so far.

grinder-motor-base.jpeg
 

rabler

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How are you going to cut those parts? Plasma? laser? waterjet? Angle grinder?
Bandsaws, horizontal and vertical. I did order a couple of new bandsaw blades for the vertical saw after doing this. I used what was marketed as a "Starret" blade on Amazon or Ebay (?) but I'm thinking it was a cheap knock off. It cuts poorly and is welded badly so it jumps significantly every time the weld goes past the cut. Also, while 3/8" stock should be about right for a 10TPI blade, for hand fed projects I lean toward a higher tooth count.

The larger piece started life as pieces of A36 HRS 3/8" x 6" bar which I had purchased a full 20' piece for a previous project. The tabs on top were welded on and then the whole thing was milled. Sort of an experiment that was only marginally successful. The problem (of course) is that welding is really hard to get things perfectly aligned and straight, and neither face was flat so I had trouble putting it on the table. What I should have done is sat it up on some 123 blocks that didn't span a weld. Duh.

(For those of you not use to working with cellulose, these are sitting on a woodworking shaper table.)
IMG_4297.JPG

The large cutout for the motor c-face was done with a 4 1/2" hole saw. Yeah, that was slow. I stopped about 1/2 way through and touched up all the teeth on the whole saw with a diamond file. My preference would have been to use a 4 1/4" hole saw and then bore it out. Or maybe I should have set it up on the rotary table. It came out well enough. I think my measurements for the four motor mounting bolts must have been off by 1/8"? You can see I milled out those holes inward a bit, kind of crude. Most of the rest of the holes are for plug welds. Once those are done I want to use the face mill to clean up the welds, I'll clean up that tab at the same time.

Since the two top pieces are identical, after I bandsawed them out, I clamped them together to drill and mill the edges. The radiused edges were done on a rotary table, I did the large base plate tabs on the rotary table at the same time. Here's my aluminum fixture plate that I use to put 14" parts on an 8" rotary table. Trick is to remember to indicate the table center in to zero on the DRO before mounting the aluminum plate on the table (held down by two 3/8" shcs into T-nuts on the table. I really need to rebuild this rotary table, it came with a factory featured backlash of several degrees, so I generally have to stabilize it by hand when making rotary cuts.

IMG_4299.JPG
It is interesting to do both the CAD and the machine work ... you learn a few things in the process that would be easy to miss if I hadn't done both.
 
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