A typical belt grinder has 3 wheels -- a drive wheel, which is typically crowned, a tension idler, which is usually where the tracking adjustment is located, and the contact wheel, which is where the work is done. Contact wheels are typically mounted on a loose tool arm so they can be removed & replaced easily. The diameter of the contact wheel controls the shape of the hollow grind on a blade. You can buy contact wheels in 6" up to about 14" diameters. Contact wheels are often urethane coated to extend the life of the abrasive belt, and make grinding quieter. They need to be absolutely cylindrical, and concentric/parallel to the axle of the wheel or a poor finish on the knife will result.
Flat plattens are used to create flat bevels. Many of the cheaper grinders use mild steel bar stock as the platten which wears quickly. Higher-end grinders use hardened tool steel. Some knife guys use fire-proof glass, or ceramic. One guy has even made a water-cooled platten backer to both extend the life of the belt and reduce the frequency of water baths on the blade. The plattens are always considered consumable.
(06-09-2015, 04:44 PM)RobWilson. Wrote: [ -> ]About the same time as when rubbing something back and forth on a bit sand paper became lapping .
I thought that was polishing?
Sanding / Grinding
Easy................ Sand Wood ................... Grind Metal
DaveH
(06-06-2015, 10:48 AM)dallen Wrote: [ -> ]Hope 3400 RPM motors are cheaper there then they are here.
Gosh David you're right ........... 3 phase motor do seem much cheaper here, however they are 2840rmp, and are 220v.
DaveH
A new company just started to make them.
Here it is ........................ now isn't that beautiful
[
attachment=10996]
DaveH
Looks pretty much the same as all of the others. It might look better in pink though.
Ed
(06-10-2015, 04:30 PM)EdK Wrote: [ -> ]Looks pretty much the same as all of the others. It might look better in pink though.
Ed
Funny you should say that, I asked if I could have it in pink, he said "sure, will need a couple of extra days"
This is a two wheel belt grinder so the belt can be driven in reverse. (No idea why one would run it in reverse)
DaveH
(06-10-2015, 05:02 PM)DaveH Wrote: [ -> ]This is a two wheel belt grinder so the belt can be driven in reverse. (No idea why one would run it in reverse)
DaveH
So you can sharpen both sides of the knife you're making.
To put the metal back on.
(06-10-2015, 01:07 PM)DaveH Wrote: [ -> ] (06-06-2015, 10:48 AM)dallen Wrote: [ -> ]Hope 3400 RPM motors are cheaper there then they are here.
Gosh David you're right ........... 3 phase motor do seem much cheaper here, however they are 2840rmp, and are 220v.
DaveH
I have a 1750 rpm motor on my belt grinder it works ok, but could use the extra speed.
But seeing as how its a 3 phase motor I could hook it up to one of the VFDs that I have and run it at 120 hz which would run the RPM up around 3400.
But for what I do with it I can afford to buy a new belt a little quicker then if I had the extra RPM.
I'm going to have to try Vinney's trick on making a soft rubber covered contact wheel, mines just bare aluminum that I cast and machined out it works is all I care about, that and the belt staying on