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Rottman
12-09-2011, 01:25 PM
So I'm in the process of building a grinder for 50x2000 mm belts and I'm pretty free in designing the flat-grinding arm. What is a decent length for a platen?

Thanks in advance

jmforge
12-09-2011, 02:50 PM
Typically, they are 8-9 inches long depending on the grinder model. That would be 200mm minimum.

Rottman
12-09-2011, 03:54 PM
I thought of making it around 250 mm since the steel I have is 500 mm and that would give me a spare platen. If there's a possible gain of going longer than 250 mm I'm all ears. The grinders I've used had all very different designs so I don't have first hand experience with the KMG clone I'm building.

jmforge
12-09-2011, 05:36 PM
If you are using actual KMG measurements or parts, then I'm pretty sure that you want the 8 inch platen. Also remember to make the tooling arm longer than the regular KMG one. Your 2000mm belts are about 10% longer than the 72 inch belts that the American machine was designed for.
I thought of making it around 250 mm since the steel I have is 500 mm and that would give me a spare platen. If there's a possible gain of going longer than 250 mm I'm all ears. The grinders I've used had all very different designs so I don't have first hand experience with the KMG clone I'm building.

David Metzger
12-09-2011, 06:00 PM
The vast majority of grinding will be over a small area of the platen. I think this is the main reason people stick pyroceram fireplace glass to the steel plate to prevent wear. The length of the platen might help flatening the edge before grinding or flatening the spine. Maybe it could also be helpful for distal taper. It really depends on what other equipment you have for these type of things.

I forgot to mention that platens cause significant drag, so the longer the more power you need.

RRLOVER
12-09-2011, 06:57 PM
I made a 6" and a 10" platen out of 2"x1" 6061 t6 al. with a glass liner.

jmforge
12-09-2011, 07:57 PM
Good point. On blades the size of the typical kitchen knife, you can grind lengthwise on a normal vertical platen without removing pieces of your fingers as long as it is not in intergral. Pyroceram or graphite/carbon fabric are good stuff but they do have certain disadvantages. Using either means that you can only use one side of the platen. With the plain steel platen typical on a KMG, you can use both sides and have two or even four different radii on the edges. Also, the edges of the pyroceram can get chipped out, so you need to be careful.
The vast majority of grinding will be over a small area of the platen. I think this is the main reason people stick pyroceram fireplace glass to the steel plate to prevent wear. The length of the platen might help flatening the edge before grinding or flatening the spine. Maybe it could also be helpful for distal taper. It really depends on what other equipment you have for these type of things.

I forgot to mention that platens cause significant drag, so the longer the more power you need.

Rottman
12-09-2011, 08:54 PM
If you are using actual KMG measurements or parts, then I'm pretty sure that you want the 8 inch platen. Also remember to make the tooling arm longer than the regular KMG one. Your 2000mm belts are about 10% longer than the 72 inch belts that the American machine was designed for.

I don't use KMG measurements, I'm using a KMG inspired plan from British Blades (for 1600-2000 mm belts) that I fit for my needs. Power will be 1.5 KW with VFD.

l r harner
12-09-2011, 09:45 PM
i like the thought of the AL with the pyro glass face as the AL woudl wick more heat away from the platen then the steel one (yes i make mine way hot when grinding )

RRLOVER
12-09-2011, 10:32 PM
i like the thought of the AL with the pyro glass face as the AL woudl wick more heat away from the platen then the steel one (yes i make mine way hot when grinding )


The heat reduction was my goal when I made them and it does run cooler then my old steel platen.

Mike Davis
12-11-2011, 02:11 PM
You can also get creative and do a liquid cooled one...SOund like you need to Butch lol. I will do a drawing in a few minutes and post it...I am doing this on mine...Just need a small water tank,an aquarium pump, a few fittings and some rubber hose.

jmforge
12-11-2011, 02:18 PM
I want to build one of those like Brian Fellhoelter made. That looks like it would be a slick little accessory.
You can also get creative and do a liquid cooled one...SOund like you need to Butch lol. I will do a drawing in a few minutes and post it...I am doing this on mine...Just need a small water tank,an aquarium pump, a few fittings and some rubber hose.