Short platen

I run a 1.5hp 120v motor over a 8" platen with a 2" and 4" contact wheel.

It grinds very well, how would a 4" platen be better for HP?
 
I have a 2”, 4” and 10” flat platen. I fail to see how any of that really affects horse power? The wheel or contact point is still the belts width so other than if you were really bearing down and pushing that hard against the wheel, what would it matter?
 
The shorter the platen, the less drag on the motor. Seems it would also reduce heat, and maybe even some static electricity build up. I was just thinking why have a 8-10" long platen when 95% of the work in bevel grinding is done on the area 1-2" above the tool rest.
 
AVigil said:
I run a 1.5hp 120v motor over a 8" platen with a 2" and 4" contact wheel.

It grinds very well, how would a 4" platen be better for HP?
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I'm grinding hardened blanks at 7500 fpm with a lot of pressure. The longer the platen the more friction increases.
 
your belts shouldn’t be super tight, tight enough but the friction is on the wheels. Your platen should only be taking friction when you press your piece against it. I suppose there might be slightly more friction above / below the contact point but I imagine it’s moot. If you don’t have a mist system your still going to be into duncking your blades when grinding heats them.

There are various items that sell at blade supply shops that you can use to reduce some friction. I spent a bunch once on an air cooled unit thing a ma jig and it did help but I still had to watch my blades on more worn or higher grit belts.

Give it a try, can’t hurt just not thinking it will make a large difference personally
 
mike-E said:
I'm grinding hardened blanks at 7500 fpm with a lot of pressure. The longer the platen the more friction increases.
Click to expand...
Are you using a glass platen?

Friction should only be an issue where the blade contacts the belt. If it has to much friction on the platen otherwise it needs to be adjusted back a couple hairs.
 
Your platen should sit proud of the wheels by a 1/16-1/8". This helps maintain a straight running belt on plunges. I run a mist system, and 8" glass platen.
 
mike-E said:
Your platen should sit proud of the wheels by a 1/16-1/8". This helps maintain a straight running belt on plunges. I run a mist system, and 8" glass platen.
Click to expand...
Sounds like a fine system.

My two cents on this is I think the 8" platen would cooler because there is more surface area to dissipate the heat with a 8" Platen... I also grind Harden Blades with a 1 1/2HP motor on both of my machines and I have never felt under powered??
 
I use a 2" platten. It still gets hot. Not much temp difference than longer platten. I use the 2" since i resurface my platten by hand (sandpaper on flat surface, figure 8 pattern) and it is easier to touch up.
 
I would say that the cost of HP (from a motor) is relatively cheap in the overall scheme of grinding...
also if you do kitchen knives you can grind lengthwise on a long platen.
 
mike-E said:
I'm grinding hardened blanks at 7500 fpm with a lot of pressure. The longer the platen the more friction increases.
Click to expand...
Mike , I have two grinders for now .One is with 2hp motor and about 4 inch plate .Other one is with 1.5 hp motor and around 8-9 inch plate ...I have no notice any difference while grinding .My belts barely touches plate when run free . . . Most time I grind hardened steel ...both run very fast ....If you think that you loose power I think that you have belt slip on drive wheel ............As I have on first one .
 
mike-E said:
Your platen should sit proud of the wheels by a 1/16-1/8". This helps maintain a straight running belt on plunges. I run a mist system, and 8" glass platen.
Click to expand...
1/8" is 3mm , right ? That create a lot of friction/heat .I don t see any reason to do that ....If you have problem with straight running use stronger spring ...
 
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