rousseau crowning glory?

[Woody Alan]

Hi

I had already bought one of these plates to fit into my table and reading all this made me decide to flatten mine. In fact I am in the process of doing it. First I have used one of these SB280 from http://www.permagrit.com/system/index.html I happen to have it from my model making days, just keep working it across the plate until flat including the inserts. Then I am working through wet and dry until I will finish with a polish, probably not as shiny as original but it will be a lot flatter. Someone said that they thought it was crowned because of the inconsistensy of moulding the plastic, I am inclined to agree if only because mine dipped near the inserts after having risen.

Cheers Alan

 

[johnnyb]

i tend not to agree about the difficulty of moulding a flat plate. every contour and item on the plate seems deliberate ie mine is also dipped slightly around the insert. if the mould is flat the inset will be. although the price will not allow much correction afterwards. use a piece of tufnol as a router plate.

 

[Woody Alan]

I have flattened mine now, Observations are, if I may Argee, that you must have had a very different plate to me because this was very visible to the naked eye and took a fair amount of effort to remove the "hump" from the middle. Now I know there are various theories about why it's humped and it should be flat. For what it's worth (and not very much at that) I believe we are at a design/manufacture tolerance thing again, and I'm not sure it's entirely due to the plate as much as the inserts.
There is a cost issue associated with making those middle inserts so accurate they fit in exactly right without sitting proud or low so the answer to avoid any "snagging" (which is why it dips down to the hole after rising) on the edge of the hole or the inserts this slight bump is put in. If it was made flat or as close as possible, it is possible the weight of a router could deflect it a couple of thou which is enough to risk snag.
None of this matters too much if you are doing mouldings but if trying to use the table imaginatively as Steve is there are issues.
Just my thoughts not aiming to be contentious. I have left a minimal rise on my plate the luxury of hand finishing which should prevent snagging should it sag.

Cheers Alan


Cheers Alan

 

[Paul Chapman]

I had already bought one of these plates to fit into my table and reading all this made me decide to flatten mine. In fact I am in the process of doing it.

Be interested to hear how it turns out, Alan, when you have finished it.

Cheers :wink:

Paul

 

[Argee]

Observations are, if I may Argee, that you must have had a very different plate to me because this was very visible to the naked eye and took a fair amount of effort to remove the "hump" from the middle.

Of course you may! I've had both my inserts for a number of years and they are exactly as I previously described them, causing me no problems whatsoever.

Ray.

 

[ike]

I fear the flatness (or lack of it) issue is mostly down to shortcomings in the injection mould design and material used. One could get a very flat plate with stiffness approaching that of aluminium by thorough mold flow analysis and molding for example in a resin such as 'Grivory'. Unfortunately however, not all product designers or indeed toolmakers/injection moulders are created equal - I know at least from working with toolmakers anyway!

Ike

 

[johnnyb]

it could also be flattened with a router and ski set up. i would tend to make another disposable table of mdf with a cutout for the plate and use a wide milling cutter. once flat finish by hand.