Planer Sled for Face Jointing

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Forum topic by cpbuck posted 01-04-2019 04:48 PM 1082 views 0 times favorited 9 replies Add to Favorites Watch
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14 posts in 645 days

01-04-2019 04:48 PM

Topic tags/keywords: jig planer plane jointer joining

Hi all. I am having issues using a planer sled to face joint some longer boards. My sled consists of one piece of 3/4” melamine and I use shims and hot glue to stabilize the board. When I run it through the planer and put a straight edge on it, there is a dip in the middle. It removes more material in the middle than at the ends. This is happening to 5/4 stock.

Is this an infeed/outfeed issue? I am using the Dewalt DW735 planer.

Could it be that my planer sled isn’t stiff enough? Should I double up the sled thickness or even build a torsion box sled?

Any help would be great. I have a table top to build and my jointer isn’t long or wide enough.

9 replies so far

View DrDirt's profile


4588 posts in 4197 days

#1 posted 01-04-2019 05:02 PM

Seems a strange problem…. it would seem to me if the sled were not rigid enough… the rollers would flex the sled, and you would cut LESS from the middle, and have a high spot, not a low spot.
Only thought is that the board is not fully supported (needs more shims).. but as above, “more support” in the middle, would make for a deeper cut, not a shallower one.

-- “The two most important days in your life are the day you are born and the day you find out why.” Mark Twain

View AlaskaGuy's profile


5332 posts in 2764 days

#2 posted 01-04-2019 05:18 PM

Why not make life and you hobby more enjoyable? Buy a jointer. For me anyway an jointer is a must have tool.

-- Alaskan's for Global warming!

View pintodeluxe's profile


5970 posts in 3268 days

#3 posted 01-04-2019 05:28 PM

Planer sleds are just a funky way to face joint lumber. The technique is rife with problems, especially on longer boards. As an example, compare the bed length of a good 8” jointer (which might be 75” long) to a piece of melamine the same length. At first glance they seem to have the same length, and offer adequate support.

However, the jointer is flat along its length to within .003”, while the melamine may sag 1/8” or 1/4”. Add the fact that the workpiece is only supported here and there with dabs of glue, and the roller pressure from the planer is significant. I’ve always been surprised that technique worked for people.

That said, I do use a planer sled in conjunction with a jointer to flatten boards wider than my jointer would normally allow. That seems to be a good solution if you have a jointer.

-- Willie, Washington "If You Choose Not To Decide, You Still Have Made a Choice" - Rush

View EarlS's profile


2987 posts in 2803 days

#4 posted 01-04-2019 05:52 PM

First, I’m assuming you are talking about the sides of the 5/4 board, so you are standing it up and running it through the planer.

Use the jointer sled to get the faces smoothed out and relatively flat then use some double sided tape and a long straight edge and make an edge that will track along your table saw fence. Kind of like a straight line jig or a EZ jointer jig. By getting the face close to square and flat on the planer you wont have a severely twisted/bowed board to push through the saw.

Alternatively, gang a bunch of 5/4 boards together and run them through the planer together.

-- Earl "I'm a pessamist - generally that increases the chance that things will turn out better than expected"

View clin's profile


1051 posts in 1451 days

#5 posted 01-04-2019 05:57 PM

I’ve had very good results using a planer sled. There’s some things to consider.

Generally the sled itself does NOT have to be unusually rigid. 3/4” melamine works fine (that’s what I use and happens to be a shelf board). You are running it through a THICKNESS planer. So the only thing that matters is the distance from the bottom of the sled (that’s the reference surface) to the cutters.

Now, were rigidity of the sled can play a roll is IF the shims or other contact points supporting the stock are farther apart then the bed of the planer. This however should never be the case because then your shims are likely much too far apart for the next issue.

Even thick stock can bend under the pressure of the planer, so 5/4 can bend. You need to make sure you have enough shims under the stock to prevent this from happening. It’s not simply that you need to prevent the stock from rocking on the sled. It must be supported anywhere it doesn’t actually touch the sled. Of course I don’t literately my there is never any gap, but with 5/4 stock I’d be thinking of a shim every 4-6”. Of course it all depends on how stiff the stock is and how much pressure your planer applies. Shallower cuts will generally apply less pressure.

Shimming doesn’t need to be elaborate. I use wood door shims. Bundles of these are inexpensive. They only need to be secured enough that they don’t move while handling the assembly. I generally use a dab of hot melt glue. I don’t glue the stock to the shim. Just the shim to the sled. The I will put a dap of glue under the stock at the ends to make sure it can’t shift.

But again, the planer is mostly pushing down on the assembly. I’ve often had the whole thing sort of flop around with the sled drooping below the stock as I pick it up for large runs (6-8 foot boards). As long as it ends up back in the original position as you feed it into the planer, that’s all that matters.

Here’s what is critical !!!!

The bottom of the sled must be absolutely flat when you shim up the stock. Remember the bottom of the sled is the reference. The planer will cut to an exact thickness, but to get a flat result, the whole assembly must be flat to start. In my case, I have an assembly table that I built that is very flat, somewhere in the range of <0>s no question using a sled requires a lot more time to setup. Though with experience you can do it pretty quick. I would never consider a sled for a production shop.

-- Clin

View cpbuck's profile


14 posts in 645 days

#6 posted 01-04-2019 06:44 PM

Thanks for the help. I do have a jointer but it’s a 6” Ridgid and I don’t get good results with longer boards. I am making a table top soon with some longer 8/4 stock which is why I have been experimenting with the planer sled.

Clin, your point about making sure the sled is flat when shimming and hot gluing the board makes sense to me. I doubt my workbench is completely flat. Its just two layers construction grade plywood (I built it when I just started woodworking so it’s probably time for an upgrade). If the sled isn’t flat and then I shim and glue the board to it, it becomes rigid and that non-flatness will remain as I run the board through the planer. I will check this tonight.

View bilyo's profile


780 posts in 1557 days

#7 posted 01-04-2019 07:51 PM

With almost the exact same setup, I had the same problem. I think you understand the concept so well explained by clin. I solved the problem by making a torsion box for a sled. For me, making the sled straight and rigid worked well. I start a cut by having the sled supported by a roller stand and have another roller stand to catch it on the other side. Of course, as clin stated, it is important to have the work piece well supported with little wedges anywhere the planer rollers might cause it to flex. Doing this I get very flat results.

Another approach using your sled would be to install a temporary auxiliary bed that extends about the length of the sled on either side. Of course, this needs to be straight and well supported. Your sled will then slide on this surface and stay flat all the way through the cut.

In theory, I suppose, as was stated above, your sled should work as is. In practice, I’ve found that the flex in the sled causes inconsistent results as you have also experienced. I understand that others are able to make it work, but for me, the stiff sled is the easiest solution. I have used it to flatten many BF of crooked lumber. The auxiliary bed would also be a good solution if I had space to leave it set up which I don’t.

I’ll add one more piece of advice. Do the best you can to cut your lumber to rough size before planing it. You will waste far less wood that way. For instance, if you have a 6’ piece that varies from flat by 1” over it’’s length you will lose a lot of material by planing it in one piece. If you can cut it in half first, you will lose about 1/2 of that. If you can cut it into 3rds, you will lose even less.

View cpbuck's profile


14 posts in 645 days

#8 posted 01-04-2019 08:13 PM

Great advice bilyo. I learned that when I remade all my cabinet doors. Rough cut everything, do a quick initial mill, let the wood move and settle for a few days in the shop, then do your final mill/joinery/assembly. Straight dead flat doors everytime!

View cpbuck's profile


14 posts in 645 days

#9 posted 01-05-2019 01:28 AM

Threw a straight edge on my work bench tonight and it wasn’t even close to flat. Time to upgrade

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