Mayerial for jigs - make a difference?

[steve_b]

Maybe not the correct forum but it is a BT3 question - kind've
All my woodworking tools live in the garage 24/7/365 - so they see all temps & conditions - It may be a nothing question but I might as well ask - does material for jigs and the like that I make for the saw make a difference? I wonder if moisture will effect MDF - plywood etc - so form/fit/function remains constant.

And is there any opinion on MDF vs plywood (I'm thinking 3/4 G2S) for jigs
want to make a fence extention with feather board, router fence (attached to existing fence with dust collector)

Thanks

(just noticed - cant spell material - duh)

[LarryG]

It partly depends on what the jig or fixture does, and what kind of component it is, but generally speaking my first choice is Baltic birch plywood. Second choice is MDF. I have used 13-ply 3/4" plywood from Home Depot for some things -- it's roughly comparable to Baltic birch -- but not the ordinary 7-ply stuff. The last tends to have too many voids, and won't stay flat.

I don't see the extreme temperature swings that you get, but I do have high humidity to contend with. As long as MDF stays dry, it is probably the best material in most respects ... it's the most stable, has the smoothest faces, machines beautifully, and it's dirt cheap to boot. Its main drawback is the difficulty of putting mechanical fasteners in its edges (splits easily), which is the main reason Baltic birch is my preferred material despite its higher cost. Also, MDF is not suitable for things like miter slot runners.

[dbhost]

What Larry said...

I have a couple of jigs made with BORG pine plywood. Not a pretty thing... This stuff bends, warps, and twists every time a cold front moves through...

[SARGE..g-47]

I use the plywood Larry mentioned also and MDF.. just depends on the jig. Most of my extentions are MDF triple coated all sides with poly. Some are 10 years old and going strong. As Larry my climate in Atlanta is mild but with high humidity summer months.

[steve_b]

Since I can see the issue with mechanical fastening on edges with MDF.. I'll see if my local HD or Rona carries Baltic
1/2" heavy enough? or 3/4 the best way?

Thank you

[Uncle Cracker]

The thicker the better, Steve, particularly if you are going to be edge-fastening with screws. That's not to say that 1/2" isn't fine for smaller stuff, either, particularly if you are gluing, rather than screwing... Unless you are building a one-off throwaway fixture, you will want your jigs to last and be stable, so it pays to spend a bit more for the good stuff.

[BigguyZ]

I know Menards have Baltic Birch ply. I've used that stuff, and it's worked out failry well for me.

[tribalwind]

i dont know anyplace near me that has the baltic birch,
i've used regular 3/4 ply,mdf, and solid phenolic(i have a good source)
the ply can warp or have voids, the mdf chips out and splits easy with screws, the phenolic is virtually indestructible and perfect.. but stinks when cut and a ***** on blades(i have a few dedicated for only cutting it).here in long island, we do have some moisture and temp extremes

[LinuxRandal]

Here a while back (haven't been in the shop in months), I was in my local hardwood store. They said a lot of their clients, use either Baltic Birch, or MDO, as those are their two most sold plywoods, and people use their leftovers.

[poolhound]

Since I can see the issue with mechanical fastening on edges with MDF.. I'll see if my local HD or Rona carries Baltic
1/2" heavy enough? or 3/4 the best way?

Thank you

Thickness really depends on the specific jig or fixture you are trying to make.

In some cases MDF plus glue and mechnical fasterners or even brads works just fine.

HD MDF is fine but I would not touch their ply especially for jigs and as far as I have seen no HD ever stocks baltic birch. I would search through your yellow pages and call around local lumber suppliers or woodworking stores they should all stock BB.

[Tom Miller]

HD MDF is fine but I would not touch their ply

Yeah, what he said. While you're at HD, pick up some 2' x 4' pieces of 1/8" and 1/4" hardboard. This stuff comes in really handy for jigs, and plenty of other stuff, too. And, more to the original point, I think it's reasonably humidity resistant. (Edit: If it's the smooth on both sides stuff.)

Regards,
Tom

[eezlock]

material for jigs.....

First, yes the material does make a difference. Baltic birch plywood, luan,
then mdf if they aren't exposed to moisture. Second, make the jigs with glue and screws they will be more stable that way and expand and contract less
over time. After assembly and you are satisfied with the way they work with your machine, you should give them a good sanding on all surfaces and a couple coats of clear spray shellac. You will be surprized how good they look and how much longer they last after being sprayed! When the shellac dries
completely, paste wax the areas where the jig needs to slide on the machine,it will reduce friction by 50% or more...believe me it works!
Hope this helps.......eezlock