# Sealing table saw sleds and other jigs to prevent warping from moisture



## Rick1970 (Jan 29, 2015)

For those of you who live in humid climates, do you seal, (apply some kind of finish) your sleds and jigs? Even those made from plywood. Here in Alabama, where I live, I find it difficult to find a straight piece of plywood. Granted, I haven't tried any of the lumber yards yet, just the big box stores.

I recently made a table saw sled and it warped slightly, not very much but enough to push my cuts out of 90 degrees. Would sealing with, say, shellac have prevented this?


----------



## Ghidrah (Jan 20, 2015)

I keep a dehumidifier running most of the yr, once the shop temp drops below 45° I shut it down. In general if laminating the rule of thumb is to dupe the mat on both sides. If you only have 1/2", 5/8 or 3/4" ply as your platform it shouldn't be a problem unless you're using a low grade ply like CDX meant for exterior sheathing. Cabinet grade, AC or Luan, Most of jig platforms are 1/2 Luan.


----------



## agallant (Jul 1, 2010)

I live in NC and the only time my shop is climate controlled is when I am in there, scratch that I have become accustom to the weather down here and have stopped turning on the AC in the shop. I have never had a sled or jig warp.


----------



## wapakfred (Jul 29, 2011)

I use baltic birch for all my jigs/sleds. They stay unfinished, and I've not had one warp yet. Finishing will slow the moisture penetration somewhat, but it won't stop it. You have to finish all sides, and that might make thing slide with more resistance over cast iron. We likely don't have your humidity, but that's not to say we don't have any….it gets pretty damp around here at times in the summer.


----------



## Ghidrah (Jan 20, 2015)

I don't treat my platforms either. High summer I empty my dehumidifier 3 times a day, the bucket trips at about 2 1/4 gals. 2 yrs back, (#2) the old one died in early summer didn't realize it till the tables began to discolor, by the time (#3) was up and running I had to resurface 6 tables, hadn't had to do that in over 15 yrs.


----------



## BillWhite (Jul 23, 2007)

I make it a habit to seal all my jigs with a coat of shellac ( maybe 2 or 3 depending), then waxing with Johnson's Paste Wax. Just a habit to make all the jigs, etc. smooth and easily super slick to what ever top they might encounter.
Does this mean that I'm habitual? 
Bill


----------



## Ghidrah (Jan 20, 2015)

MDO works well too.


----------



## Rick1970 (Jan 29, 2015)

> I keep a dehumidifier running most of the yr, once the shop temp drops below 45° I shut it down.
> - Ghidrah


I had not thought of using a dehumidifier; I'll have to try that as spring is right around the corner.


----------



## Rick1970 (Jan 29, 2015)

> I make it a habit to seal all my jigs with a coat of shellac ( maybe 2 or 3 depending), then waxing with Johnson s Paste Wax. Just a habit to make all the jigs, etc. smooth and easily super slick to what ever top they might encounter.
> Does this mean that I m habitual?
> Bill
> 
> - Bill White


Yes in fact you are habitual, but in a good way.


----------



## Rick1970 (Jan 29, 2015)

Thank you for the responses.
It would seem I just did a poor job of building my sled. the base is 1/2" birch but the fence is two laminated pieces of 3/4" CDX. I need to stop being cheep and use the proper materials. However I don't think I'm ready to use hard wood for jigs. Just can't bring myself to do that yet.


----------



## rwe2156 (May 7, 2014)

From the humid south:

I've found MDF for your sleds works well. 
Coat it with BLO and shellac it.

Store sled vertically.

No problems


----------



## TheFridge (May 1, 2014)

You can get good birch or other generic hardwood ply from the box stores that is useable, but you just have to dig a little bit. I use 2-3 laminated pieces of ply for the fence. Pretty much eliminates warping and is easy to make.


----------



## Rick Dennington (Aug 27, 2009)

All my jigs, fixtures, and sleds are finished with 2-3 coats of Tung oil….When completely dry, a coat of Johnsons.


----------



## DrDirt (Feb 26, 2008)

I had a crosscut sled made from baltic birch and it warped. Not bad enough to mess up the 90 degree cut, but it made a hump on the right side, such that there was a lip at the saw kerf that prevented sliding stock smoothly from left to right.

I made a new sled from MDF, and because i was concerned that it could get set on a wet spot, and soak up some water, I sealed it I just had a partial quart of bullseye Seal coat shellac


----------



## OSU55 (Dec 14, 2012)

I seal all of my jigs/fixtures with shellac, not for preventing warping per se, but to prevent any liquid that may be spilled from being absorbed. Glue is easily removed from a shellac surface, but not bare wood. Saw dust or other dust/dirt will slide right off, but not off bare wood. My sometimes oily/greasy hands won't stain a shellac surface, etc. Just too easy to throw on a coat of shellac and know I don't have to worry about all the possible things that can cause problems with bare wood.


----------



## sawdustjunkie (Sep 12, 2013)

I also made a sled with Baltic Birch 1/2" and the right side warped by almost a 1/2".
I tried to cut the rear back stop and put some weight on it to see if it will flatten out.
If it doesn't, I'll make a new one with MDF. I have other jigs using that and have never had any of the warp.
What suprised me is the Baltic Birch actually warped that much.
My shop is the garage and I have heat in the winter, but no humidity control at all for the summer.


----------

