best platens

M

magnum .44

Joined
Jun 12, 1999
Messages
1,110
how should i make my platen, so i get a very smooth flat grind? what tips do you guys have for modifying platens so they are at the best they can be. keep in mind that i have a surface grinder so if they need to be surface ground flat i can do that. i can buy glass too, shouls i face it with that?
i already rounded over the top and bottom edges so the belt doesn't get caught on it and split the splice. these are $12 belts so i don't want to wreck them.
 
Magnum, my platen is 1/4" surface ground and hardened D2. I have thought about slightly radiusing the sides but never have. Maybe someone else can comment on that. This works good as is though.

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Jerry Hossom
www.hossom.com
 
Magnum .44

You might want to try some platen cushion. I use this and have not ripped or torn any belts. But if your belt are spilting at the splicing point, talk to your abrasive sales person. There has been some belts known to be spliced incorrectly, and they fail, to no fault of yours.

Good Luck
Jeff
 
I used to have my platten surface ground every time I felt a shutter or a hollow started to develop on the surface, no more...

I have started using the glass trick just by putting a peice of 1/4 inch glass epoxied directly to the platten. The change is incredible! not only is it flat and smooth, I think the belt slides across the surface of the glass a lot easier than it does across steel, unless you took it to the same degree of surface finish. The glass doesnt hold up well for hogging or for work from a workrest for profiling, the constant hammering of the splice on one spot starts to crack the glass. So what I think would be ideal is a nice flat fully hardened D2 or vascowear platten for profiling and hogging your grinds then switching to a glass surfaced platten for final bevels and finishing grits...

Alan Folts...

PS anybody wanna make me a hardened D2 platten for a Bader 2?
smile.gif




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If a Man talks in the forest, and there is no Woman around to hear him, is he still wrong?
 
how about hard rubber, like a contact wheel? thanks for the tip on the d-2. can i use 1/8" d-2 epoxied to 1/2" thick steel? cuase i already have the 1/2" thick stuff, it has to be welded to a bar, d-2 doesn't weld very good. it's going to be used for hogging off steel, and finishing, so i can't use glass. do you think i could substitute a-2 for d-2? or is it less wear resistant?
thanks for the tips guys.

[This message has been edited by magnum .44 (edited 03-19-2000).]
 
Hmmn... This is a timely thread. I've got a slab of 5mm teflon bar sitting at home that would be about the same dimensions as my grinder's platen. Since a 220 grit belt let go on me this weekend while flat grinding, I was thinking of surfacing the steel platen with the teflon, with the leading and trailing edges feathered to ease the belt transition.

Since no-one apears to have done it, I'll give it a try and report back - unless someone can think of a good reason not to...

Cheers,
Tim
 
thanks tim, i'm looking forward to seeing the results of using teflon on the platen.
do you think it will stand up to flat grinding?
 
Originally posted by magnum .44:
thanks tim, i'm looking forward to seeing the results of using teflon on the platen.
do you think it will stand up to flat grinding?
Click to expand...

Not sure... But since it cost me nothing, and is currently doing nothing, I figure I have precisely nothing to lose.

My two concerns with it are melting, and grooving due to imperfections in the belt. If your platen is being cut by the back side of the belt, it's not going to take too long before the results are coming through on your blades.

Anyway, we'll see. I'm sure between us all, we can come up with the perfect platen. I can picture it now... surface ground, hardened D2, glass-backed, bevel edged, teflon impregnated and liquid cooled....

Cheers,
Tim
 
Guys: Here is my experience:
-Rubber won't work
-Teflon won't stay flat
Graphite coated cloth won't stay flat either.
-Hardened steel is more difficult to set up and maintain and bows when heated.
Glass works best-good cyanoacrylate works fine for putting it on.

As to belt breakage- You should adjust your platen so that it protrudes ONLY SLIGHTLY beyond the face of your wheels.
Use a straightedge and be sure nothing moves when you tighten the bolts. Radius the top edge, and, you're set. I've never ruined a belt or had one break when using the platen. You don't need to crank down on the tension excessively, either. And, 4000SFM should be fine for speed.

Now, as for hogging, you should never hog on the platen! If you're tapering tangs, remove 90% of the material with your contact wheel, leaving just the perimeter to be flat ground. This will take about 20 seconds per side to accomplish, and, you don't need to push hard. If you push hard, you'll flex the tang, and, it won't come out flat anyway, no matter how flat your platen is!

For roughing work, just use the angle iron platen.
Buy a spare platen attachment, and set it up with glass. Use it to finish your tangs after HT. Always use fresh, sharp belts for finishing, or, again, you won't get a flat tang.
Trust me, it's not rocket science. Been there, done that, and, this is the simplest, best way to go.

RJ Martin
 
rj, i'm looking for flat grinds, i haven't tried out the tang tapering, when i do i'll use the angle guide on my surface grinder. whould glass stand up to flat grinding, or will it break. should i just get my platen hard chromed?
should i make the top wheel on my platen adjustable, so i can move it forward or backward? with some sort of arm?
should i worry about the hardened steel
bowing if my motor is a variable speed up to 1750, with a 6" drive wheel? the steel whould be epoxyied to 1/2" steel also.
is it possible to use ceramics? to glue onto a platen?
tim, i think rj is correct, it wont stay flat. you can try it if you like, there may be unexpected results.

[This message has been edited by magnum .44 (edited 03-20-2000).]
 
for flat grinding, again, you should be doing almost all of the grinding on the contact wheel, then, flattening it to remove the last 20% of the steel. working on a platen is very severe on both the belt and you, so, do whatever you can to minimize the time you spend there.
I do my flats on a 6 x 48 machine, using the cast iron platen. I like grinding flats holding the knife horizintally, rather than vertically-it sems much easier to me. Ny only machine modification is rounding the edge of the platen slightly. I "break" the edge of my belt using a piece of scrap stock so the belt is soft where it overhangs the platen and the abrasive is worn down somewhat so it cuts more slowly than the main part of the belt. you can grind a perfect plunge in this manner, with no gouging and a beautifully smooth radius.
I see no problem grinding flats on a plain steel platen that is flat and smooth. you can grind at different locations on the platen and your grinds will be plenty flat enough. I like a belt with a heavy backing, as it provides a nice cushion and keeps little riples,waves and things from showing up on the grind.
As you get finer in your belt grit, slow down and don't use heavy pressure.
graphite coated Canvas is occasionally useful, but, it's finicky-wears unevenly, etc. and you need to look out that you don't start getting funny effects on your grind.
Slow belt speed is more important as your belt gets finer.
Flat grinding is tricky if you're going for a high finish-I believe most guys who do it well do a LOT of hand finishing above 320 grit.

You don't need a moveable wheel-on my Bader, the platen can be moved in-and-out, allowing you to set it's location relative to the wheels.

Good Luck,

RJ Martin

 
rj, what brand of CA do you use? Most I've tried are heat sensitive.

Jerry Hossom

[This message has been edited by GaKnife (edited 03-21-2000).]
 
thanks for the tips rj, i think i'll face my platen with hardened d-2. the glass seems like it would break.
 
If you face the platen with glass, should the glass, then, be radiused? If so, how is this done?

------------------
Hoodoo

The low, hoarse purr of the whirling stone—the light-press’d blade,
Diffusing, dropping, sideways-darting, in tiny showers of gold,
Sparkles from the wheel.

Walt Whitman
 
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