Another 2x72 Belt Grinder

[James Combs]

I have lots of pics so if you want to see all of them without interrupting commentary, please hold off on any comments until you see my post labeled "Finale". That said here we go.

Started building this close to a year ago and have finally got it into a usable form. A 2x72 Belt Grinder/Sander, made mostly from two $5 yard-sale treadmills and salvaged material I already had. These grinder/sanders are typically used by knife makers but they are very useful for most any grinding/sanding operation. Only work left to do on it is mounting it onto a stand and a paint job. It is just setting on my table-saw out-feed at the moment but still very usable. I designed it to be switchable from vertical to horizontal and to be able to pivot the flat platen and a 10" contact wheel in and out without having to have a separate off machine storage location for either.

Purchased parts, BTW it was not that cheap and I did not build it to save money, mostly just for the experience :

I believe this is everything I purchased.
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Some pics of purchased Items: The "D" platen, contact wheel, tracking wheel, and the electronics enclosure.
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I am sure a lot of you will recognize the Oneway grinding fixture base/lock. I used a 40psi gas spring for tension.

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The build:
Treadmill Motor Mod (Don't need steel grinding dust inside a permanent magnet motor)
Just realized that about $20 can be added to the cost for plumbing parts used to mod the motor.
Used a PVC adapter, floor drain, and magnets to hold filter material to capture grinding dust that might migrate back to the motor. It's not shown but I replaced the three wires with a round power cord and install a liquid tight fitting for the cord. In the processed I also reversed the rotation of the motor(switched the red and black wires in the cord.
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To be continued, out of pic space.

[James Combs]

Another pic of the motor showing the wiring.
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Drive Pulley Fab: Made my own 4" drive pulley from 4+inch squares of .8" thick Phenolic sheeting.
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The results: I made it 3.82" which gives a circumference of 12". One rotation is one foot of belt travel which means an RPM readout is also Ft/Minute.
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Motor & Pulley Installed on the Grinder:
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To Be Continued:

[James Combs]

The Swivel Platen/Contact Wheel:
Drew the entire machine on cad first:
Printed parts to be cut out on adhesive backed paper at full size to give me cut markings and hole locations.
Reinforce the while axle mount with a pipe flange and a brass pipe insert. The insert ID was re-threaded to 1/2-13 for the wheel axle. The threads go all the way through the brass and the 3/4" aluminum pivot/mounting plate. The thickness of the pipe flange/brass fitting and a lock nut brought the wheel out to near perfect alignment with the wheels on "D" platen. The whole thing is mounted on a large piece of Phenolic.
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A tee handled locking screw was fabricated from a 1/2"-13 piece of all thread rod and matching coupler a similar 3/8" one is used for tracking adjustment.
The pivot plate is held at it's pivot center to the Phenolic with a couple wave washers on a 1/2-13 bolt/nut.
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To Be Continued.

[James Combs]

The Tension Arm:
The tensioning swivel was made from 1x2x.125"wall tubing. The tracking wheel is mounted onto the top of the shorter leg, the cut out notch piece is used as the gas spring mount and a piece of 1" conduit tubing was notched, welded in place and used as the handle. The white paper was just for a contrasting background for the pic.
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Mounted and in use and a close up of the tensioning/tracking wheel.
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Side and rear views.
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To be Continued:

[James Combs]

The Work Rest:
Fabricated from a piece of A2 steel, some 3/4" heavy walled tubing and a Oneway grinding jig base. Will pivot as well as rotate from vertical to horizontal which allows it to stay horizontal when the machine is rotated from vertical to horizontal.
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The Onway mounting and a slight mod for more screws and threaded holes.
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A piece of 9/16" socket was welded in place to hold the head of the pivot bolt. Also shown is a mock-up of the main structure rotated 90* to horizontal.
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To be continued:

[James Combs]

Final Post:

The Controls:
Didn't want to use the treadmill controls as the final controls although I did use them or a 12V battery for initial running and tracking checks.
I found this idea on YouTube. It uses a 10,000watt SCR which out puts variable pulse width AC and piped that through a 50amp bridge rectifier which the will output a variable pulse width DC for a very cheap PWM DC motor speed control. Works great, the downside is that it doesn't have all the motor protective circuits in it that a dedicated(expensive) PWM DC motor speed control would have. However, I have 4 more treadmill motors so not a problem.
Installed everything into a metal box including a cheapie Chinese RPM meter readout, an extra on off switch stolen from my Grizzly lathe spare parts. There was a large choke used with this motor on the tread mill so I installed it in the box and output circuit also.
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Made a label for the box cover, installed liquid tight fittings for the wiring and reinstalled the controls, mounted and tested them. Everything worked great.
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This is the final initial(oxymoron anyone ) post for this thread. I will be posting another with links to videos of this grinder in operation.

Appreciate any and all comments and/or criticisms.

[James Combs]

Had a little vibration from the motor/pulley combo so did a run-out check of the pulley and a little in-place correction.
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After the correction I had just barely detectable vibration at around 3600 RPM. In one of the pics above you will see a nickle on the work surface where I was doing a standing nickle test after the correction. I stood until about 3800 RPM and then there was so much air coming off the belt that it kept "blowing" over. That's my story and I am sticking to it.

[Doug Walls]

Nice looking belt grinder set-up!

Reinforce the wheel axle mount with a pipe flange and a brass pipe insert. The insert ID was re-threaded to 1/2-13 for the wheel axle. The threads go all the way through the brass and the 3/4" aluminum pivot/mounting plate.
IMG_3349.jpg

I like the use of the pipe flange & brass insert for the axle support!

I hope to build a 2" X 72" belt grinder myself this summer, Just gathering information & ideas for now.



Doug

[James Combs]

Doug, thanks for looking, hope you have as much fun building yours as I did mine and perhaps there are some ideas here you can use. If you would like to see it running checkout my vids on YouTube, just figured out how to get them there a couple days ago. lol They are nothing special, no narration, just me playing with the machine. At YouTube, search on "Another DIY 2x72 Belt Grinder #" There is #1, #2 and #3 so far. Here is a link to #3. https://www.youtube.com/watch?v=oYYLlnQWC-Y

It's my nickle test for vibration.

[Carroll Courtney]

Dang that is neat,really love the variable speed.Adding this to my wish list of things I want to build,once I get my metal cutting BS up and running.Will be coming back to this post later for some of your ideals.Thanks for posting-----Carroll

[James Combs]

Dang that is neat,really love the variable speed.Adding this to my wish list of things I want to build,once I get my metal cutting BS up and running.Will be coming back to this post later for some of your ideals.Thanks for posting-----Carroll

Hi Carroll, appreciate the comments and hope something in the post helps. Just came online to add an update in another thread on the final version on it's stand.