Longevity of shop-built jigs

[Leuf]

So today I brought out my shop-built tenoning jig that rides the table saw fence and made a mess of some tenons. Brought over the square and saw just how much that sucker could rock on the fence. Hmm, it sure didn't do that a few months ago.

My miter sled that I made in the winter worked really great, until the summer when the oak runners wouldn't even fit in the miter slots due to the change in humidity. After planing them down with a shoulder plane it just never slid quite as well as it did before, and I'm in real trouble when winter comes back. My plywood zero clearance insert wasn't flush with the table anymore either.

Do I just suck at jig building or is every one else quietly cursing at the jigs they made a few months ago?

-Leuf

[tom]

[tom]

[tom]

[tom]

[RayV]

Yeah my u-shaped sacrificial fence that slid nicely over top of my fence now needs a 16oz persuader to get it on and off. I thought plywood was supposed to be stable.

[Ron Magen]

Ray, Hate to burst your bubble . . . steel will do the same thing.

That's why heating the nut will help to free a 'rust-frozen' connection. And inversely, if you want a tight fit for a pin, freeze it for a 'slip fit', then drive it in.

Pack to the ply . . . this is one reason I use UHMW material for runners, contact points, position locators, etc. Not glued, but screwed on or otherwise attached. Typically somewhat adjustable for 'Zero'.

Regards & Good Luck, Ron Magen Backyard Boatshop

SNIP

[mac davis]

I'm sure it's a common problem.... can't just be the two of us, Leuf..

I use a lot of non-wood parts now, including a lot of corian... a 3/4" strip of corian is a great miter slot runner and can be sanded, drilled, etc... no seasonal movement...

The plans for my next crosscut sled are for a transparent plastic base with corian runners.... I took me a few years to admit to myself that jigs don't have to be wood just because you use them FOR wood... Mac

[Leon]

I do not think it is you rather the material you are using. I make most all of my shop built jigs and shop-built tenoning jig and zero clearance inserts out of 1/2" Baltic Birch. No problems at all with fit or warping. The tenon jig is 7 or 8 years old and I live in a climate that has very high humidity in the simmer and much lower humidity in the winter.

[Andy]

I had to scrap and re-build a router table fence when the first one warped pretty significantly after about a year. I'm still confused about this one - made entirely of particleboard and hardboard, which I thought was supposed to be very stable. If I held a straightedge against the fence, there was a space of almost 3/16" at the middle of the fence. I'd suspect moisture, but the whole thing was "finished"/sealed with titebond II all the way around. Oh, well. I should probably get some UMHW plastic if I insist on being cheap and building stuff on my own, and do it right (the third time...). Andy

[cselby]

No, but your learning about materials to use. I went to a plastic supply house here and looked through their cut-off bin. For 5$, I got 8ea 1x2x48 polyethelene slabs. I cut some to 3/4x3/8 for slot runners, fine tuned with a surface planer. Also lucked in to 3/8 lexan - enuff to make 3 router table inserts for 20$. Try shopping at a plastics place for cut-offs.

Pete

[Chris Friesen]

I don't have as much experience as some here, but he instructions for the sled that I made were explicit about orienting the grain of the runners so that the expansion occurs mostly in the vertical direction.

Using Northern Red Oak as an example, going from 5% humidity to 10% humidity will cause a width change of 11 thou if flatsawn, but less than half that amount if quartersawn.

[Leon]

I do not know about particle board or hard board being stable however MDF and plywood's and I suspect particle board and hard board are indeed stable as long as the climate remains stable. Adding glue to a side of MDF can cause it to warp. Multi layered plywood's like Baltic Birch tend to be pretty stable.

[David Merrill]

I've seen second-hand dehumidifiers in the local Habitat for Humanity surplus outlet for as little as $15. Some of these are missing their condensate buckets, but you really need to set the unit up to drain continuously to a floor drain, shop sink, whatever. In my humid NC mountain climate, I run mine 24/365 and the humidistat keeps my shop at 50 percent relative humidity all the time. Previous owner left a Sears unit with the house and it's still going strong after five years.

David Merrill

[John]

It's not you, it's the materials you're using. I had made all of mine at first out of whatever material was at hand, precisely because it was cheap and available. The plywood in particular would assume all sorts of compound curves after a year or so of sitting around in an unheated garage. Subsequently I started making jigs out of scraps of hardwood and various plastics. I came upon some free rectangular bits of 1/4 inch thick acrylic sheet which work pretty well, and I've even cut up an old white plastic cutting board (don't know what kind of plastic it is but it doesn't swell or contract). Leftover bits of the better grades of birch plywood, when shellac'd and then edge banded the way you'd do for a book shelf to keep it from sagging, seem to last okay too. Never could bring myself to part with the $$$ to cut up the Baltic kind for a jig though, or to cut and trim plastic laminate over a raw plywood jig, but maybe I should someday.

J.

Leuf wrote:

[J T]

Thu, Aug 17, 2006, 1:01am [e-mail] (Leuf) doth beat his chest and query: Do I just suck at jig building or

Apparently.

I make mine from plywood, laminated if need be, and have no problems. Plywood runners on my old saw sled worked fine too,,for who knows how long, until I tore it apart to make a new one to meet new needs.

JOAT Justice was invented by the innocent. Mercy and lawyers were invented by the guilty.

[mac davis]

Might be the hardwood, Andy... My router fence is 3/4" particle board, doubled up for 1 1/2" thickness and has never warped or moved from humidity, AFAICT.. it's about 10 years old.. Mac

[Bruce]

On Wed, 16 Aug 2006 23:01:03 -0600, Leuf wrote (in article ):

Humidity aside, another thing to watch out for is to build your saw jigs _after_ aligning your table saw.....

[Rick Samuel]

Baltic Birch works great for me. 2 ts sleds, 2 years old. Not a lot, but still in new condition. (Nicks don't count)

[Leuf]

I'm still having trouble wrapping my brain around the zero-clearance insert not being flush anymore. It's 1/2 inch BB, well actually two

1/4 pieces laminated together. It's got to be at least 1/64th proud of the table now. I would have thought its expansion would be 5 thou at the most.

I intend to remake the tenoning jig out of some 1/2" BB and I think this time I will make a box slightly narrower than the fence and shim it, attaching the short side with screws only. The first time I just did a single piece across the top of the fence dadoed into each side and then added bracing over it. I also want to make it easy to replace the stop at the back edge, there's not much left of the one on there now for the first inch or so above the table.

I'm thinking about getting some metal slides for the miter sled. Something to do with my $15 off at woodcraft anyway.

-Leuf