Since we’re talking about crosscut sleds…how many runners?
I’m about to make my third crosscut sled. First one is now a dado sled. Second one is bigger than needed most of the time, and so…here we go. Sled number three.
First two sleds both got two runners, but I found later that I had to fettle the runners a bit to keep ’em from binding. This got me to wondering about the necessity or desirability of two runners for a sled.
There are claims made that a two-runner sled is more stable and more accurate, but I’m not aware of any meaningful data to back up such statements. It seems to me that a solidly-attached single runner should be able to do the job–that is, keep the whole contraption moving in a straight, perpendicular line as one slides the sled over/through the blade. It’s also fairly obviously easier to build a sled with a single runner. Matt Kenney’s FWW article on his second-fence technique for a sled featured a design with a single runner, and it was called “super-accurate” or some such, I think. I’m inclined to think that a single runner is a good choice. But…I’ve been wrong before, including at least twice since lunch. So….
I realize that the question–Two runners or one?–might attract more heated opinion than illuminating discussion, but here it is.
Is building a sled with two runners merely a manifestation of the “If one is good, two are better” phenomenon? Or maybe, “God put two slots on table saws for a reason, and it’s so you could put two runners on your crosscut sled.” Did some Really Famous, Notable, and Unquestioned Master of Woodworking make a sled with two runners, and that set the stage for everyone else? Or…is it just a thing regarding which one does whatever one wants, and need justify it only to oneself?
Replies
> "Or…is it just a thing regarding which one does whatever one wants, and need justify it only to oneself?"
Suspect this is your answer, at the end of the day. Whatever works for the sled YOU built for YOUR saw to keep it running true.
FWIW, I've been through similar iterations to you. Settled on one runner, figuring that simpler construction and fewer moving parts to fettle = less that can go wrong and easier to fix if it does; and setting the thing up perfectly and then keeping it there is half the battle. Does mean that runner has to be a good one, though. But my cuts are all reliably square.
No doubt someone will be along to tell how wrong I am... Not that I have a fixed view, just that it Works For Me(tm)
I think this is a case of what ever works on your saw and accomplishes what you want it to accomplish. On my smaller cross cut sled, I have no runners. I place the blade in the kerf and square the sled with the fence. Then I I put a mitre guage in each runner on the saw and screw them to the sled. This works extremely well, simplifies the construction and also means I can easily use it on any table saw. My very large cross cut sled has two runners because a mitre gauge that is long enough isn't available anywhere. Works just as well, just more fussy to build.
The sled I use most of the time is pretty small, and only uses one runner. I like it a lot.
Hi
My last sled I used tip #2 in link below. Eliminating the need to fettle runners in two-runner sleds.
I’d never seen it before and would use it again.
Mike
https://www.instructables.com/6-Tips-to-building-a-better-Cross-cut-Sled-for-you/
I think that’s the same as this method. I’ve used it a couple times with great results (easy, and no slop)
https://www.finewoodworking.com/2012/05/31/foolproof-crosscut-sleds
P.s. MikeinOH, you may not recall, but thanks for tip on router education (Bill Hylton). He wrote a book published by the American Woodworker, it’s been extremely valuable to me!
P.p.s. Nevermind, I see now that you are MikeFM not MikeinOH, ha.
Actually I *did* recommend a Hylton book to someone a few weeks ago!
Lol, that was me! Just looked back, it was fm and not OH. Looks like I’m the one who can’t recall :(
Anyway the book is outstanding. Very clear, well organized, breezy reading.
Thanks! I’d forgotten about this technique, and haven’t used it yet. I read about it when scouring old FWW archives (same as that given by weymouth2, below, I believe), but for some reason didn’t employ that method on either of the first two. Can’t recall why, or if I even had a reason. Seems almost like cheating! And by the way, I’m giving serious consideration to UHMW PE for the runner(s). (I saw you mention that material below.)
I’ve only made them with one, but I think moving forward I’ll make them with just one purchased runner. I find seasonal movement to be a real drag sometimes when it comes to runners and accuracy so I like the aluminum ones with the set screw to take out the slop. I wanna try 1/2 baltic birch treated with CA to toughen it up, in my head it works.
But personally I really rely on that kerf being dead on for as long as possible and you can only put so many layers of hardboard down before its just ridiculous.
Just being able to make a tic mark, line it up with the kerf, and confidently cut is huge in my shop.
I’ve used UHMW plastic with good success.
Lee Valley has it in reasonably sized sheets. They also offer it precut for miter gauge slots but I found they were too small for my table saw although just right for the bandsaw. Anyway my point is don’t buy the precut UHMW.
Mike
https://www.leevalley.com/en-us/shop/hardware/jig-and-fixture-parts/32045-uhmw-polyethylene?item=46J9011
I took a class at CT Valley School of Woodworking (Bob Van Dyke’s school), and he uses Baltic birch plywood for his runners (so, I did too). You have to run it through the planer, but he said after he gets the width dialed in on TS he’ll make a batch of them and store the unused ones in a large’ish diameter piece of pvc pipe and grab them as needed.
I much prefer the 2 runner setup. If you install the fences after cutting the sled in half, you can set the runners to the inner edges of the miter slots. This eliminates any slop.
Ditto on two runners. Two runners reduces any minor racking or binding. If you get binding, that means your sled is racking in the slot and your sled is producing inaccurate angles. I use hardwood scrap for my runners, usually oak, planed to fit. Don't forget to wax them. Even my largest sled glides smooth and gentle with no binding - ever.
I might disagree slightly with regard to binding; if working in a shop with significant temperature & humidity swings, and wood runners, wood swelling can produce binding that may (or may not) cause significant racking. The runners on my sleds were machined so close to “perfect” fits—and in the winter—that when summer humidity came around, they did bind a bit. Some very careful evaluation and adjustments got things back to square, etc. But it does raise a question about binding for a single (wood) runner in such circumstances, and whether there might be some racking then (or later, if too much slop is introduced, and one is not careful to always press the sled against the slot).
And good tip re the wax. With my first sled, I didn’t wax the runners at first, and doing so made a big difference.
Long ago stopped using 2 runners and making them from wood. Aluminum runners are relatively cheap are more consistent and just easier to install. An innovative idea I picked up from one of the YouTubers my son insists on sending me is instead of putting my single runner to the left of the blade mount it to use the slot to the right. The advantage in this is if you need to make a bevel cut you insert the runner in the left slot this enables you to cut bevels off the edge of the sled without another kerf tearing up your zero-clearance insert.
I have three.
A panel sled with one runner because a panel in a door is not that fussy. This is pretty large, 28" wide, 23" deep, sled is only to the right side of the blade.
The next is a two runner centered sled, 18" + 18" wide, 19" deep, that is pretty accurate and has a stout rear fence and a smaller top fence. I use this one for table apron and leg builds. I use the rip fence with a block for repeat cuts, or if the pieces are smaller, one on the rear fence.
The last one is smaller, two runners, and very accurate, five cut method accuracy, that is off set to the right. 10" to the left of the blade, 16" to the right, 7.5" deep. I use this one to cut tenon shoulders as my saw miter gauge is not good.
It honestly doesn't make a difference.
I currently have left, right, wood, aluminum and steel. They all have a purpose.
I would say more than material or number of slides, make them long enough. the longer the reference surface, the more stable and accurate your sled will be.
Twin runners are not necessary on all but the largest sleds, otherwise a single should be sufficient.
JMHO
The BEST and simpelest way to make an accurate sled was by Alan Turner on the front cover of FWW edition ????. I will try to find it and post it.So simple and accurate even a fool cant not do it right
Don't be so sure (that's kind of a joke)
I think you might be referring to this article?
https://www.finewoodworking.com/2012/05/31/foolproof-crosscut-sleds [Full PDF, behind paywall, I believe: https://www.finewoodworking.com/membership/pdf/10048/011227042.pdf%5D
This is the same one mentioned by weymouth2 above. I’d forgotten about Turner’s article, but I like it—with one exception. I’m not keen on the way he affixes and adjusts the rear fence. That said, I’m not especially fond of any particular way of doing that yet. All seem to have a weak spot.
Just my experience. I've got 2 sleds for my saw, both probably too big. First on I used a fancy steel runner, and just one. Second I used 2 oak runners. Whenever I build number 3 it will have 2 runners.
I think there might be a issue with a miter slot on my saw that I didn't identify at first, I think there is a subtitle inconsistency in the width, so might be part of the issue.
My single runner sled tends to shift or bind a little bit. My method for attaching runners has not been a big issue. I fit my runners, tight to each miter slot, then place some shims under the runners so it is proud of the table. I place glue on the runners, and put the plywood on the runners and place weight on the plywood. I let the glue set and then add some screws as extra security.
So…update. Built the sled. Two runners, even though I implied I was probably gonna go with only one. Made the runners of purpleheart—had a strip left over that was looking for a home. Sled of 1/2” MDF, two-layered 3/4” Baltic birch PW for fences. Three-cut method from Tom McLaughlin to get rear fence square. This sled is 40” wide—16 L, 24 R—and just more than 10” deep between the fences. Decided I wanted to be able to cross-cut up to 10-inch nominal width lumber with my “small” sled, with enough length to support great majority of pieces I’ll be cutting.
I decided on the second runner because of the imbalance in distances either side of the blade. Just seemed good to have a second runner, although I can’t say logic played a big role in this. Probably more or less a security blanket approach.
Our sleds sound similar, down to the materials. One thing I do that helps me mentally but probably nowhere else is to apply a few coats of white glue/water mix (50/50) on the MDF, especially the edges. It seals and protects it, in my mind at least.
I was actually wondering about that sort of thing yesterday. Had the thought of using a penetrating wood-hardening resin on the MDF, but that seemed like overkill, too much work, and harboring some unknowns that could prove unwelcome. Also thought of a slightly diluted hide glue application. But the 50/50 white glue & water sure sounds easy.
Totally no interest in this as I have a slider, which is basically one giant runner.
Nonetheless, I would have thought that two runners is a bit like having two watches.
I suppose if one of the runners were to wear and become a bit loose then it would matter, but otherwise it's unnecessary extra work to put them on.
I agree that having a slider makes all this pretty much irrelevant. But how did you know I wear two watches? Well, actually, I have one on my wrist, and another in my pocket—my cell phone. This last is a device that seems to wish to do everything for me. (Except chop out deep mortises. ) But it does keep excellent time. And it can also serve as a level, an angle finder, a (slightly rough) tape measure, and make julienne fries.
2 runners are best for me. I work in the garage, environment is constantly changing. Use hardwood for runners, these provide the most stability.
This forum post is now archived. Commenting has been disabled