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2X72 Belt Grinder

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buddy3223

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#1
I just completed a new 2x72 grinder. I used the plans from Dan Comeau and found that the machine works quite well. The following material was used:
2x2x.250 square tubing
1.750x1.750x.250 square tubing
.500 alum. for the platen holder
Set of 4 roller from Oregon Blade Maker
8x14x .250 steel plate for base
2hp 3450 motor single phase
Assorted nut and bolts
It was built as per plans but I would suggest using fine thread for the top roller adjuster, as the adjustment is very sensitive with a course thread. The machine runs very smoothly and has no sign of vibration. In comparison to my friends grinder it quit a bit quieter. Most of the cost was taken up by the motor and rollers, I have a little less than $300.00 for the total job. image.jpg image.jpg image.jpg image.jpeg image.jpeg image.jpg image.jpeg image.jpeg
 

mikey

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#2
Came out nice, Buddy. Had a few comments:

You might want to epoxy on a Pyroceram liner on the platen so it stays flat over time.

So, direct drive motor, right? Might be a little fast when using fine grit belts; eats them up quick! Variable speed would be nice someday, maybe?

A bunch of guys have built one of these here. Hopefully they'll chime in and compare notes.
 

ttabbal

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#3
I agree with @mikey. The glass liner is very nice to have.

I went 3 phase with a VFD for variable speed. It's nice to be able to to adjust the speed both higher and lower depending on the belts and the job. Your work might not need it though.

I like the hand screws. I should do something nicer than bolts on mine.

I bet you will use the crap out it. Mine gets used for much more than I expected when I built it. Even for dead trees (kids pinewood derby).
 

rwm

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#4
I suspect you are going to find the direct drive motor too slow even at 3450 rpm. Assuming your drive pulley is about 4" you are running at about 3500 SPFM. To grind steel you should be shooting for 6000 spfm according to Burr King. I used a 6.5" pulley on a 3450 motor. You may consider moving to a pulley drive if you find that it is not fast enough. The VFD is also a great idea. I wonder how fast you can overdrive it with a VFD? Otherwise it looks great!
Robert

Edit:
"Question: What abrasive speeds are best for which materials?
Answer:
In general abrasive speeds from 4000 to 8000 surface feet per minute are recommended for mild steels and aluminum. Abrasive speeds from 3000 to 6000 surface feet per minute work well with stainless steels and cast irons. Exotic materials such as titanium generally prefer speeds below 2000 SFPM. Plastics and other polymers usually prefer speeds below 2000 SFPM. Woods and similar fibrous materials are often best ground below 6000 SFPM. Grinding speeds are determined by the material to be ground, the finish desired, and the abrasive used. "

Burr King Website.
 
Last edited:

buddy3223

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#5
Thanks for all of the replies. I plan on changing the motor once I get the rest of the items that I will need for this machine. I am making a set of small wheels and a large contact wheel. I am also making a rest for the machine. This motor was bought for another project and is being used to work out any bugs. I was totally surprised at how smooth and vibration free it was right from the start. I have ordered a glass liner for it also. Can JB Weld be used to install the glass liner?
 

mikey

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#6
Yup, JB Weld works. It has a fairly high heat tolerance but good prep is a must.

Your platen can be mild steel but should be as flat as you can get it so that the epoxy bed is complete and of even thickness. That is why I used precision ground O-1 steel instead of a mild steel bar. My platen is screwed to a piece of angle iron that is attached to the chassis of the grinder. The angle iron screw holes are slotted to allow precise alignment of the platen to the belt path.

As I mentioned, you should drill and tap the lower part of the platen for two socket head cap screws that the platen liner sits on. They act as a stop in case the epoxy lets go for some reason and prevents the liner from dropping down and getting trapped between the belt and wheel.

Before mounting the liner, use a medium grit belt (80 grit works) to lightly round the sides and top edge of the liner. Yes, use your belt sander for this; you'll get orange sparks! This prevents the sharp edges of the glass from cutting your belts in use. Also lightly sand the back of the liner and the face of the steel platen with 80 grit; this provides tooth for the epoxy. Then clean everything with Acetone to remove all traces of oil.

Apply a thin layer of JB Weld to both pieces and join. I use multiple spring clamps to clamp them together. I think I must have 8 clamps on a 9" long liner. Allow to sit undisturbed for 24 hours and don't try to speed it up with heat. Remove the clamps, clean up any drips and you're done.

I suggest ordering at least three liners and make two platens; if something happens one day, you'll have a complete platen ready to go so you don't have to stop working. Keep the extra liner for a spare. If a liner comes loose somehow they can be re-used but you have to use a torch to get the old epoxy off and its a hassle. I would just toss it and use my spare.
 

Z2V

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#7
Treadmill motors and controller work well for belt grinders also. On Craigslist for free if you watch for them.
 

lordbeezer

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#8
Look for treadmills with a knob or slide switch for speed control.most have a mc 60 controller.large or commercial type treadmills have much larger motors.most have KB electronics.
 
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