Jigs - Material - Woodworking Talk - Woodworkers Forum
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post #1 of 9 Old 02-16-2020, 07:58 AM Thread Starter
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Jigs - Material

I have always used plywood for the bottoms of my table saw cross-cut jig, Straight Line Rip and similar jigs. No special reason other than that is what I always have laying around.
I noticed on here some people use masonite, some MDF, etc.
What do you use and why?

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post #2 of 9 Old 02-16-2020, 08:20 AM
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good question, Tony.

I DON'T use MDF: as in my area, it is an inferior product for most
of my needs. it curls & warps easy, absorbs moisture, edges and corners
are easily mooshed up. does not hold screws well that are often removed.
thus - plywood with a coat of paint or varnish is my "go to" for jigs.
plexiglass for the hand-held router base plates.

Edit: cleaning up today. will be putting 4 pcs of 2x2'x1/4" sheets of
MDF in the trash - absolutely no need for it.

.
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post #3 of 9 Old 02-16-2020, 05:10 PM
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Cheap, dimensionally stable, easy to work with, commonly available.

MDF is great stuff, but a lot of people try forcing it to do stuff it shouldn't do, square peg and a round hole. It's not very moisture resistant, so yeah, don't use it in wet environments. It's compressed sawdust so no, it doesn't stand up to frequently removing screws. That doesn't make it useless. If you need a table saw sled or a quick assembly jig, it's hard to beat something you can glue together, doesn't change with seasonal humidity swings, and is dirt cheap.

I'd be pretty hard pressed to find a plywood that works as well as MDF for shop jigs for the same cost. I can get MDF for $30 a sheet, and I'm guaranteed a smooth, flat face and dimensional stability. Can't always say the same for the ACX plywood in the same price bracket
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post #4 of 9 Old 02-17-2020, 08:07 AM Thread Starter
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The only reason that I haven't used MDF for jigs is mainly due to weight. I use it a lot for other stuff though.
I have read that all it takes to make it moisture resistant is a coat of lacquer or any other hard finish.
The only plywood I use is either baltic birch or cabinet grade.
I notice that on you tube a lot of folks use what looks like construction grade. Dont know if it will stay flat.

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post #5 of 9 Old 02-17-2020, 09:59 AM
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I don't like it for jigs just because it doesn't take screws well, but I will use it if some is hanging around. I really like quarter inch mdf for painted door panels. It is exactly 1/4 inch (unlike 1/4" ply) fits perfectly in grooves and paints really well, no grain lines at all. I just made a workbench with 3/4 mdf as the top, looks good with 3-4 coats of poly on it and is flat. All in all, I hate using it because of the dust and it's a lot heavier than it was when I was younger, but it has its uses. Actually, all sheet goods are a lot heavier now, I'm beginning to think its me.
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post #6 of 9 Old 02-17-2020, 10:11 AM
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I use MDF for my guitar molds and forms, for my spoilboard on the CNC, and occasionally for a fixture or template. But I rarely have MDF on hand so I use BB often for fixtures. The only drawback to that is the thickness is only about 0.475" and two pieces end up being too thick for some things. I don't do any sheet goods work except for the Longworth chucks in BB so there's never any plywood laying around to use.

And I don't ever have any construction lumber here, no 2x4's or Pine, so many of my fixtures are made of Maple and Walnut. If I were to do an inventory I'd say over half of my fixtures are Maple and Walnut, come to think of it...

Our shop is climate controlled so I don't have issues with MDF swelling or bowing, it just stays flat and straight. But my preference is to use it for the CNC spoilboard only unless I have to use it for something else.

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post #7 of 9 Old 02-17-2020, 06:59 PM
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I've used those handi panels of plywood from HD (for about $20-25 4x8; couldn't find link) for casework projects for the shop. I let stand on the long edge propped against a wall and when I went to break it down, I found that is has sagged. I had to rough cut and then press flat on the work bench.

Back to the topic, I would use it for jigs because I have scraps on hand. I think screws will strip out because it's not as dense (core) as you would think.
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post #8 of 9 Old 02-20-2020, 10:30 PM
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I use Baltic birch. I think the 1/2” is 9 ply. Very stable. Plus as a cabinet maker, I have stock on hand at all times.

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post #9 of 9 Old 02-20-2020, 11:06 PM
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I use mdf for jigs that I expect to cycle 10-100 times. I like the flatness and uniformity. I hate the dust. This shaper jig was cycled 8 times for a raised panel door.
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