Belt Grinder Upgrade

[cfellows]

This is a picture of my updated belt grinder.  Before this weekend, it had a 3450 RPM, 1 HP pool pump motor.  When I'd flip it on the, lights would dim and the belt speed, at almost 5,000 SFPM was downright scary.  It also had a substantial amount of vibration.

Yesterday and today, I swapped out the motor for a 2500 RPM, DC permanent magnet motor.  Now, top speed is around 3200 SFPM and, since it's plugged into a variac, any speed from 0 up to the maximum.  It's also reversible, but I haven't figured out any practical need for that.  I trued up the 4.5" drive pulley on my lathe and that helped the vibration a lot.  Probably should true up the top pulley as well.  At any rate, it's now much tamer but still removes metal at a respectable rate. 



Don't know how many of you know about this, but several of the knife making supply houses sell ceramic glass platen liners for the platen or backer plate of your belt sander.  Here's a link:

http://www.usaknifemaker.com/ceramic-glass-liner-for-flat-platen-2x9x-0192-p-1181.html

I also just ordered the 2" x 9" x .192" piece which I'll JB weld onto the platen.  That should greatly reduce the wear on the platen and provide a slicker, cooler running backing for the belt.

Chuck

[sparky961]

Chuck,

I saw two things in here that clashed in my head.... you said that it's a DC motor and you control the speed with a variac.  By the very definition of a variac, you would be varying the amplitude of an AC source.  What other pieces are in the system?  Big rectifier, capacitors maybe?  Or is there something I'm missing here?

I'm very interested because I have a very nice variac I haven't done anything with but was afraid to use it for AC motor speed control for fear of destroying the motor.  I'd be interested in your take on this.

Thanks..
-Sparky

[cfellows]

Chuck,

I saw two things in here that clashed in my head.... you said that it's a DC motor and you control the speed with a variac.  By the very definition of a variac, you would be varying the amplitude of an AC source.  What other pieces are in the system?  Big rectifier, capacitors maybe?  Or is there something I'm missing here?

I'm very interested because I have a very nice variac I haven't done anything with but was afraid to use it for AC motor speed control for fear of destroying the motor.  I'd be interested in your take on this.

Thanks..
-Sparky

You're right, Sparky, there is another piece.  Inside the switch box on the grinder motor, there is a 200 volt, 35 amp full wave rectifier.  You can buy them pretty cheap, they have 4 connectors, 2 for the AC input, and 2 for the DC output. 

Chuck

[cfellows]

I got my ceramic glass platen liner in the mail yesterday and last night I attached it to the platen using a generous helping of JB Weld.



I was a little disappointed in the edge finishes.  They clearly scored the lines with a carbide glass cutter then just snapped them.  While pretty straight, they have varying amounts of bevel to them.  Also, the smoothing of the corners with a grinder was a little sloppy, like they were really in a hurry.  However, I have to admit that the edges won't really present any problems since it's the face I'm interested in and that is dead flat.

One of my priorities for the rest is to make it height adjustable.  Not sure why, but it just seems like a good idea.  Toward that end, I found this little dovetailed rail I had made for another project several years ago.  I ultimately used something else so this piece was a spare.  Turns out to be the exact size I needed to fasten on to the side of the column (Love it when that happens!). 





I'll make a carrier block that clamps to any position on the dovetail slide and use that as the foundation for the rest to be mounted on.  I'm looking to make an adjustable angle rest like the one featured in this link:

http://www.machinistblog.com/modifying-a-craftsman-2-x-42-inch-belt-sander-for-tool-grinding/

Chuck

[cfellows]

Made some changes to the tool rest today.  First I added a couple of strips of cold rolled steel to create a groove for a sliding table to slide in.  The two pieces are rosette welded from the bottom through 3/8" holes drilled in the supporting piece.



Next, I made a sliding table with a miter gauge to hold tool bits at various angles.  The hole on the outboard end of the miter gauge is a mistake.  The bar pivots on a flathead screw coming up through the table from the bottom on the end nearest the belt.



Here is a picture of the fixture I use to sharpen my tangential (diamond) tool bits.  It holds the tool bit diagonally on a 30 degree angle to the belt.  This is handy because it doesn't require readjusting the belt grinder tool rest.  It's made from aluminum and helps keep the tool bit cool during grinding.



And this is the fixture for holding woodworking chisels and plane blades for sharpening.  The heavy aluminum fixture helps channel heat away from the cutting edge of the chisel so it doesn't overheat during grinding.



Nothing very fancy about this set up and the fixtures, but it does greatly speed up the process of sharpening tools while increasing the accuracy and resulting sharpness.

Chuck

[BillTodd]

Great Chuck - I'm going to have to build one of those

Bill

[DavyC2]

Very nice work on the belt sander!!!!  I have an identical sander and I'll have to borrow a few of your ideas. As expressed very nicely done Chuck.
Davy