Table Surfacing -Quick question

[Simops]

No need to dwell....just a quick confirmation required.....

The spindles square to table, rollers checked and deck good to go....surfacing of spoilboard is smooth(which is attached to deck secure & flat)....

So when I surface the spoilboard, it should produce a flat and level surface.....right?

Well it is dead flat in my X-axis (your Y-axis) but in the pic below it is not flat in the Y-axis(your X) but produces a slight convex about 2 mm over 48".

Why? If it is surfacing how can it be .... I mean if you are surfacing at a set reference then should it not keep that reference when surfacing (even if the deck maybe slightly convex)?

So am I missing something here or being over concerned for no reason?

[bleeth]

Michael:
It looks to me that as your deck extends out from under the gantry it is sagging a bit. You can check this by measuring the thickness of the spoilboard. If it it the same then that is the problem, but if it is thinner at the ends then you have another issue.

[bleeth]

Nailed by the ten minute limit!

To really verify is a bit tough but as long as your base is flat pre surfacing, and so is your spoilboard, then that is probably the answer. If it were a changing of the deck thickness from moisture absorbtion it would more likely make the deck thicker around the perimeter. If that were the case, and all else were good, you would end up with a spoilboard thinner around the edges but should still be flat on top.

This issue of deck ectension support was very pronounced in the 8' powersticks in the early days. I don't know if it still is. You might try throwing a piece of verified flat stock on the table as it is and surfacing it. If after you take it off it is still flat then you know you are good when under the gantry, which is what counts.

[shilala]

Michael, I had zero luck with surfacing until I got rid of the composite deck that came with the Shopbot. It was just plain awful.
I replaced it with 2 pieces of glued, screwed, and sealed Baltic Birch and it's like I have an aluminum table now. No flex, no surfacing problems, nothing. Dead flat.
It's funny that I initially tried to solve my problem the same way you are, by using a small sheet of plywood in the center of the deck. When I did that, and surfaced it, that's what showed me just how terrible the composite deck was.
Hope this helps!!!

[Simops]

Thanks Dave / Scott for your thoughts........
So if the deck is ever so slightly convex it still can't be flattened 100% by surfacing??

I read here before when Andrew in Canada and Bob used additional rollers but I looked at that and can't see how there would be enough pressure to keep a 1.5" MDF deck flat?

Scott the spoilboard I'm using is MDF actually......the two pieces of Baltic ply you use for a deck.....what thickness? 2 x 3/4"?

Cheers

[bleeth]

I think I can speak for Scott and say-Oh yeah-2 x 3/4"
You can really help keep a home done deck flat by laminating both sides with p-lam. You'd be surprised how much stiffness that adds, although it wouldn't seem so.

[Simops]

I think I can speak for Scott and say-Oh yeah-2 x 3/4"
You can really help keep a home done deck flat by laminating both sides with p-lam. You'd be surprised how much stiffness that adds, although it wouldn't seem so.

P-lam? Got me there!

[Bob Eustace]

Well the Andrew roller method absolutely positively works on the 6 foot power stick. Hasnt had a resurface in 3 months and I think our weather is far worse than yours Mike. Our slats are only screwed on. We did use moisture resintant and now swear by the stuff. Might be time to bite the bullet. Only took Andrew half a day BUT it took us clueless Kinglakers a week! The next one might be quicker!

[bleeth]

P-Lam (American vernacular): High pressure plastic laminate (ie: popularly known as Formica; although they are only one of many manufacturers, as one of the pioneers in the industry,the word "formica" has become synonymous with the material much as Kleenex has for tissues).

Sorry Mike-I forgot you wouldn't know all of our slang.

[Simops]

Dave.....thanks now I know what you mean.....at least I think we have that in our country off the shelf without having to import a container load:rolleyes:

Bob....yea I know, I know....been real busy lately with work, away next week for a fortnight doing installs, etc. Gonna do it one day:rolleyes:

Guess need to come up your way for another visit.....but that windy road of death up to Kinglake does not enthral me!

Cheers

[Ajcoholic]

Mike, I can guarantee the rollers on my buddy do indeed keep the 2x3/4" mdf top flat pressed down against the main table rollers. Don't underestimate the strength of the hold down until you try it.

As for covering the top and back with hpl - two things I think that would really cause issue is the laminate is very slippery and would make clamping down harder without sliding. And the hpl gets very beat if you have to drive screws into it or pin with brads/nails ( I use the raptor nails often now). And what about re surfacing ? I skim the board every few months just to make sure it's still flat.

[Bob Eustace]

Bob....yea I know, I know....been real busy lately with work, away next week for a fortnight doing installs, etc. Gonna do it one day:rolleyes:

Guess need to come up your way for another visit.....but that windy road of death up to Kinglake does not enthral me!

Cheers

Mike just DONT usenyour GPS and come up via Whittlesea plus you get to go past the Flying Tarts Bakery!

[Simops]

Andrew, yes I'm sure the rollers work in keeping the ends from curling, otherwise I'm sure you would not use them....it certainly is a nice setup you've done, and Bob swears by it.....in my case the deck seems to curl down. Anyhow I just put a straight edge on top of the deck and spoilboard along the powerstick......it also shows same convexity....now surely along the powerstick it should be dead flat straight after surfacing?!! And yes the spoilboard is nailed down flat.....I also use the nylon raptor nails. Strange?

Bob, Whitlsea is a longer way....but guess 6 of one, half a dozen the other! Will do it one day on way back from work......going away this week for a while....

Anyhow when back will have take another look at all this again. Besides got to work out a vacuum solution.

Cheers

[Ajcoholic]

if your table is curling downwards... are the main rollers setup properly? I cant see how that would happen.

I set a precision 4' level on my power-stick, and then set the height of the rollers so that they are all in alignment with the top of the PS.

WHen the MDF table is bolted to the PS, and then my hold down rollers are set up, the outer edge of the table can no longer curl up nor down... (when the table is under the gantry/rollers - of course when it travels out past the rollers it can do what ever it wishes to but it is not important as when it returns under the gantry it is pressed & held flat).

On my 6' PS (which I leave on all the time) there is a slight sag over the length. Again, I feel it isnt important as when the portion that is being cut comes between the V rollers and under the gantry it is at the "same" height always. The off-hanging portion can sag a little and it doesnt affect the cut.

At least that's how I see it!

[Simops]

Andrew, yes I have already checked and setup the rollers with the power stick ( I use the 6' stick only). I did this earlier the year so should still be good.
I guess it is a fair call that only when under the gantry it is important.....maybe I'm being to pedantic!

Cheers