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Forum topic by intheshop posted 11-09-2010 02:48 AM 1659 views 0 times favorited 15 replies Add to Favorites Watch
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intheshop

58 posts in 2300 days


11-09-2010 02:48 AM

Topic tags/keywords: question

About three years ago I built the table saw sled in the photo. The base is 1/2” cherry ply, the front and back fences are 1 1/2” maple, and the runners are QSWO (for stability). There is zero slop in the runners and until recently it cut perfectly square – so well that I now only use my miter saw for sizing up rough lumber. But a couple of weeks ago I was dismayed to find that the front fence had become bowed and now the sled can’t cut square. The fence is screwed and glued to the plywood, and my shop is in my basement which is air conditioned and the humidity stays relatively constant due to a weatherproofing system we had installed. The sled is stored in the manner you see in the pic and has never been dropped or otherwise damaged.

So, how could the fence become bowed? Is it because it’s maple? Should I have used QSWO for the fence as well? I’m going to have to make a new sled and I don’t want to run into this issue again. any thoughts?

-- Fast is fine, but accurate is final. The real trick is learning to take your time when you're in a hurry. - Wyatt Earp


15 replies so far

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KayBee

1083 posts in 2708 days


#1 posted 11-09-2010 03:07 AM

Is it stored propped up at an angle like in the picture? With the bungie cord adding pressure to not make things flat?

-- Karen - a little bit of stupid goes a long way

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intheshop

58 posts in 2300 days


#2 posted 11-09-2010 03:22 AM

It is at an angle and the bungee cord is to keep it from tipping off the shelf. There isn’t very much tension on the cord, I certainly don’t think enough to warp 1 1/2” of maple but I could be wrong. It is a thought. Thanks for the input.

-- Fast is fine, but accurate is final. The real trick is learning to take your time when you're in a hurry. - Wyatt Earp

View araldite's profile

araldite

188 posts in 2866 days


#3 posted 11-09-2010 03:34 AM

Are you sure those cinder blocks are dry? There’s no moisture coming through? You have a moisture barrier in the outside between the foundation and the soil? I use to have my shop in the basement with cinder block walls and although it looked dry, there was coldness and moisture there. I covered the walls with pegboard and hung things on that.

-- Failure is the road to success if you learn to learn from your mistakes - Vince, Greenville, SC

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8iowa

1546 posts in 3223 days


#4 posted 11-09-2010 04:02 AM

While moisture is most likely the culprit, there are other reasons why a board can become warped. Trees don’t always grow perfectly vetical. A tree that is leaning develops tension in the fibers that can cause bowing as the tension is released. This is the reason why limbs are unsatisfactory for most woodworking.

-- "Heaven is North of the Bridge"

View Praki's profile

Praki

197 posts in 3459 days


#5 posted 11-09-2010 04:37 AM

FWIW, my sled made more than two years ago has remained true. The fences are glued up blocks of poplar. I read somewhere that poplar is pretty stable and picked it. The fence is attached with just two bolts, one of which is in an over-sized hold for alignment.

-- Praki, Aspiring Woodworker

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wseand

2754 posts in 2504 days


#6 posted 11-09-2010 05:06 AM

If it is all glued and you can’t replace the fence or move the rail than I would say it is time for a new sled. All wood moves over time it is just the nature of the beast.

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

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Camper

232 posts in 2318 days


#7 posted 11-09-2010 05:06 AM

Can critical components of jigs (such as this fence) be sealed with a type of finish to prevent/lessen the effects of humidity? Do not mean to highjack your thread, just thought it may be an option…

-- Tampa-FL

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intheshop

58 posts in 2300 days


#8 posted 11-09-2010 05:07 AM

Thanks for all the replies folks. Dixie, I think I’ll use the hanging method, thanks for the suggestion. Vince, the blocks are dry. There is a barrier that goes all the way down to the footers, as well as piping in the floor to carry away any water that finds it’s way in, and then a “glorified dehumidifier” that dries the air. Once again, thanks for the help.

-- Fast is fine, but accurate is final. The real trick is learning to take your time when you're in a hurry. - Wyatt Earp

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wseand

2754 posts in 2504 days


#9 posted 11-09-2010 05:10 AM

I have thought of that myself I don’t see how it would hurt to seal it but have never done it, good question.

-- Bill - "Freedom flies in your heart like an Eagle" Audie Murphy

View cabmaker's profile

cabmaker

1506 posts in 2271 days


#10 posted 11-09-2010 05:18 AM

Hi Cole, You got lots of good suggestions, personally I think you just got a piece that is gonna warp no mater what you do. Looks like an easy fix if your leading and trailing rails are the same height just run it through the table saw using the true guide on the fence. (sled inverted of coarse). Or simply get after it with a hand plane (preferably a carriage makers). For what it is worth I used maple on my sled (4/4), made this one approx. 8yrs ago and is still true. It lives on its edge next to the table saw on concrete. Good luck with it

View Gene Howe's profile

Gene Howe

8244 posts in 2890 days


#11 posted 11-09-2010 03:12 PM

I use glued up 3/4 MDF….in AZ….and have had no warpage.

-- Gene 'The true soldier fights not because he hates what is in front of him, but because he loves what is behind him.' G. K. Chesterton

View CampD's profile

CampD

1474 posts in 2948 days


#12 posted 11-09-2010 03:46 PM

A cinder block or cement foundation is going to have some or more moisture in it then the surounding air.
Its naturaly going to be cooler and therefore any moisture in the room is going to be drawn to it. Hanging the sled next to the block wall will create an area behind it for moisture to settle so to speak, so the back side of the sled is going to be damper then the front, thus cuppings #1 cause.
In the future I would hang the sled on a wall away from any foundation wall.

-- Doug...

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8iowa

1546 posts in 3223 days


#13 posted 11-09-2010 07:39 PM

We also need to be reminded that our “raw” wood should be climatized in our shop for two or more weeks before starting cutting and planing. I violated this rule last year when making maple pull out shelves for our kitchen. A few days after gluing the boards to a width of 15” they bowed badly.

-- "Heaven is North of the Bridge"

View Robsshop's profile

Robsshop

899 posts in 2437 days


#14 posted 11-10-2010 07:00 AM

Have read above posts and agree with most .Having a shop with A/C and heat will also have affects on natural woods. With different temp changes wood will do crazy things some times ! I once built a picture frame for a co-worker and after storing it in My heated shop for several weeks I brought it into work and left it in my truck for a hand full of hours(in the cold ) and it twisted so bad that the mitered spline joints cracked. I have built several different sleds over the years and have learned the hard way (as You),that stable materials are the way to go(i.e. Ply’s/ MDF/plastics and aluminum) are best choices ! My advice is to design/construct an upgraded sled, and then You can post it as a new project ( 2 BIRDS 1 STONE) !! Good Luck and be safe !

-- Rob,Gaithersburg,MD,One mans trash is another mans wood shop treasure ! ;-)

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intheshop

58 posts in 2300 days


#15 posted 11-11-2010 03:26 AM

Thanks, Rob. That’s the way I’m leaning right now.

-- Fast is fine, but accurate is final. The real trick is learning to take your time when you're in a hurry. - Wyatt Earp

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