How do I 'dress' at press platen?

John Kasaian · Aug 18, 2007

My Seal 500 Commercial platen is badly erroded in one place towards the center of the platen---about a 4" on the side triangle portion, about 1/16th deep Seal dosen't have replacements so I'm considering dressing the original platen down. I have a variety of power tools at my disposal (but nothing as hi tech as a bridgeport miller) so I was wondering what course of action the intelligencia here would recommend? I was thinking several passes with a belt sand using progressively fine grades until the 600 grit range, then polishing with a rubbing coumpound then bon ami. Any better suggestions? Ideas?

Donald Miller · Aug 18, 2007

I think that you will have a problem holding a close enough tolerance. Sometimes a miniscule particle will dent a print. A belt sander sounds like it is too imprecise to me.

I would consider looking for a used replacement myself.

bdial · Aug 18, 2007

I agree with Donald that maintaining the flatness with a belt sander would be pretty difficult. A sheet of plate glass and grinding compound or covered with stick on sand paper would do better.
Better yet, might be filling the area with solder, or perhaps metal filled epoxy if it could stand the heat.

John Kasaian · Aug 18, 2007

bdial said:
I agree with Donald that maintaining the flatness with a belt sander would be pretty difficult. A sheet of plate glass and grinding compound or covered with stick on sand paper would do better.
Better yet, might be filling the area with solder, or perhaps metal filled epoxy if it could stand the heat.

Glass with carbide grit? That sounds workable---what grit do you recommend I start with? The press is in excellent condition otherwise, so I'd hate to chuck it out or break it up for parts considering the cost of new presses.

blaze-on · Aug 18, 2007

Maybe a filler than a sheet of thin metal overlay?

richard ide · Aug 18, 2007

If your press is anything like the Seal press I had; the platen was 1/4" aluminum. If you took the plate to a welding shop and had them fill the area, then all you would need to do is flatten the weld with an aluminum file and maybe a finish sanding. Trying to reduce the surrounding thickness would involve more work than you wish to know about.
You could also just screw a 1/8" aluminum plate to the platen, although there might be a thickness issue.

Donald Miller · Aug 18, 2007

If you go the route of a metal overlay, I would recommend that you drill, and tap the existing plate and then countersink the corresponding holes in the overlay plate. In order to get good thermal transfer, it would be advisable to place thermal conductivity paste between the two plates and plan on placing your fasteners at more than the edges...to keep the overlay plate from warping over time.

Welding aluminum normally requires high freq on a tig machine and it eats up a lot of current because of the conduction characteristics of the metal.

glbeas · Aug 18, 2007

You could look for outfits that do plasma spraying, a process that melts and sprays liquid metal in a hot inert gas electric torch. These are used to repair and remachine expensive parts like train axles and brakes among other things.
Might turn out to be not very cost effective unless you are buddies with someone who works with or owns such an outfit.

GeorgesGiralt · Aug 18, 2007

May I suggest you remove the platen and show it at a shop doing car engine overhaul ?
Engine's head are often of light alloy and often need surfacing. They have good machine for this job, and would provide good advice.
I do not know where you live, but car are a universal thing so you'll find these people listed on yellow pages.
Just my 2¢

John Kasaian · Aug 18, 2007

I'll check with an engine rebuilding shop. I'm starting to think it that perhaps it would be easier to get a shet of 1/4" aluminium and just fabricate a new platen?

eclarke · Aug 19, 2007

Could you show us a snapshot?..EC

bdial · Aug 19, 2007

Regarding the grit, I had a look at my collection that I have for flattening handplanes. I'd probably start with 3 or 400 and see if it's making reasonable progress.
But I like George's idea of checking with an automotive machine shop.

glbeas · Aug 19, 2007

John Kasaian said:
I'll check with an engine rebuilding shop. I'm starting to think it that perhaps it would be easier to get a shet of 1/4" aluminium and just fabricate a new platen?

That is may be the best, most of these schemes to add metal to the sheet will probably result in a warped platen from the extreme heat applied. If it is a plain unribbed or unreinforced sheet and the screws thread into the heater base you can do the refit yourself. Lay the old sheet on top of the new one, mark the holes and outer edges, drill and countersink the holes and adjust the edge trim with a file or cutter for a precise match.

Charles Webb · Aug 19, 2007

Simply look for a machine shop that has a "surface grinder" It could be a bit expensive (see last reports of pricing from SK Grimes), but trying to replace it by fabricating a new one would also be expensive.

Charlie

How do I 'dress' at press platen?

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