fabricating a 2" x 72" belt grinder

Inflight

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I'm considering building a belt grinder that seem popular with knife makers. Here are a couple sketches I came up with so far. I plan on including the flat platen and an optional large (8" or 10" ) wheel for hollow grinding. I want the whole thing to be modular so I can quickly swap out components. Belt tension is accomplished by spring loading the vertical pillar and alignment is adjusted with the hinged idler wheel. It'll be driven by a 2 or 3 horsepower permanent magnet DC motor and a variable speed drive controller. Let me know what you think about this design so far.
Belt Grinder 1.jpg Belt Grinder 2.jpg Belt Grinder 3.jpg

Matt
 
My first impression is that the SPFM of the belt will not be high enough with a direct drive motor and a pulley that size. What is the motor RPM and what SPFM are you looking for? Mine runs at about 5000 SPFM.
Robert
 
The motor can do 3000 RPM and I thought about using a 4" wheel, which should give me a little more than 3100 SFPM. If I used a 6" drive wheel I'll get somewhere around 4700 SFPM and the 6" should fit fine.

Thanks for the feedback.
 
I would definitely go 6" minimum. Other than that I like it. Simple clean design. Does your tubing have a weld seam inside? Will that interfere with the telescoping support?
Oh yeah...I would not paint it yellow and green. LOL.
I was kidding about that but why don't you change the material in Fusion and post a rendering also? Did you draw the motor or import it? I don't have much experience importing objects.
R
 
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The color scheme was just to help me visualize the components as I did the drawing. I'm not hung up on any particular color scheme except that I don't want any two machines in my shop to look the same.

The still images above and the stills and turntable views in the video were rendered at low resolution with generic materials assigned.

The motor, nuts, bolts, washers, knobs and skate bearings were imported directly from McMaster Carr into Fusion360.


Matt
 
Does your tubing have a weld seam inside? Will that interfere with the telescoping support?

Yes, I plan on using ERW tubing so I expect I'll need to grind / file down the seam. If I keep the seam to the side with the lock knobs, it shouldn't interfere too much.

Matt
 
The platen which is the support for flat grinding may be ate up quickly by the belt and the grind dust. The knife makers use a vetrfied glass plate as the belt rub surface. Some kind of Corning Glass plate that is glued on. Your design looks good. You may need a means to tilt one on the wheels or slightly crown the wheel to keep it on the rollers. At 3500 sfm , a belt coming off would be quite exciting
 
A design I have seen, that is similar to yours as far as the grinder portion goes, is to cabinet mount it, with the motor down in the cabinet and a belt drive. That reduces the foot print, lets you keep the motor cleaner, and combined with the variable speed motor gives you a very large speed range (good torque at lower speeds and very high speeds if you want that).

I am looking forward to your build (I've long heard that a good belt grinder is very useful). Its' on the "someday to build" list.
 
The platen which is the support for flat grinding may be ate up quickly by the belt and the grind dust.
Good point. Since I plan on using scrap mild steel for the entire build, I'll make an extra platen just in case it's eaten by the abrasive belt.


You may need a means to tilt one on the wheels or slightly crown the wheel to keep it on the rollers. At 3500 sfm , a belt coming off would be quite exciting
It's difficult to see in the images I posted and the video, but there is an adjustable hinged component holding the wheel at the top of the pillar. The should allow enough tracking adjustment to keep the belts straight.

By the way, I found another motor in my shop that I might consider. It's top speed at 130VDC is rated for 5000 RPM.

Thanks for the feedback!
Matt
 
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