Finishing MDF jigs

[Vonrek]

Hi all

Having a limited tool budget, I find myself making lots of jigs to improve the versatility (and safety) of many tools. I use MDF mainly as it is very easy to work to fine tolerances and is very accurate in its thickness, a real benefit when making sliding parts.

I've read others (pro's?!) talking about MDF wicking up moisture, even from the air and changing dimensions as a result of the swelling that occurs. I've therefore finished my jigs with polyu varnish to seal out any unwanted moisture. However i do not particularly like the finish, smell, sheen, build etc.. of the stuff and was wondering if anyone could suggest an alternative, ideally that would:
1.Be low sheen.
2.Be close to 100% waterproof, perhaps penetrate a little but not cause any swelling as a result.
3.Not build too much with successive coats.
4.Stand up to a little friction and wear as a result of sliding over other parts
5.Be low friction.
6.Be easy to maintain.
7.Seal the MDF effectively.

I was thinking of something along the lines of a danish oil type mix (I konow it contains some polyu) or perhaps a combo of products with a wax topcoat?? Not really sure -- hence the post!!

Any and all takers welcome to reply.

Thanks in anticipation

Cheers, Tim

[Iain]

I've got a couple of jigs and no finish, no problems yet and I have had them for about two years.
Mate of mine is a shop fitter and he has dozens of them andd uses them until they break or are no longer needed, also no finish.
Might save you some money, I have not had a problem with the hydroscopic (sp) properties.

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: http://community.webshots.com/user/iain49

[Shane Watson]

Same as Iain, never had a problem and leave em all un-finished (thats when I use MDF as template material - I usually just use left over ply)


But if you want to go to the trouble, Mirotone (& I now believe Wattyl as well) produce a sealer designed for use on MDF (it was called 802 - but I would reakon thats changed by now as Mirotone are renowned for regularly changing there product codes). Works a treat as well. I use it when painting MDF kitchen doors in the moulding thats routered in the surface of the doors, it improves the sanding of the MDF considerably as it dosn't 'fluff' up as much, and therefore saves on undercoat.


Otherwise a quick squirt of shellac will be as good if not better than anything else.
Cheers.

[soundman]

Ive tried a number of things.
Bees wax timber polish, without getting fussy. seems to seal and give a bit of lube.
Sanding sealer with a light sand gives a hard smooth finish that wears reasonably. a quick rub afterwards with bees wax gives a bit of lube.
Nothing, for short run or non fussy works just fine.
For router jigs used with a guide I have found signboard to be great. I machines realy crisp, is hard, and has a nice white primed "A" face for marking out and writing notes on.

[John Saxton]

Hi,like other responses I leave home-made jigs in a natural state but I mainly use ply tho on occasions I do employ MDF.

I reckon that if the tolerances in the jig are susceptible to high moisture absorption
then your view on finishing may well have merit but, I don't believe I have heard of anyone here in Oz having problems.

Some well known folk employ melamine in jig manufacture and don't worry about the expense..no doubt it can be costly but with its own finish it should last.

May I suggest you look into manufactured board properties across the range whereby there may be a solution if'n you dont feel there's one here..at least that way you'll find what you want.

Sometimes a visit to a boatbuilders yard for a source of offcuts of marine ply may offer up a solution.
Cheers

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Johnno

[Glen Bridger]

Your right, MDF will absorb moisture. I made my router table out of 32mm MDF and to reduce any warping, I sealed all surfaces.
I used a light coat of acrylic primer then coated all non work areas with exterior acrylic. All work surfaces were sanded flat then coated with Spray Enamel (pressure pack).
When cured, the enamel surfaces were coated with bees wax.
I have made some jigs and given them the same treatment.

Glen