I’m losing my mind trying to square up my crosscut sled.
I’m using the five-cut method and no matter how many times I make adjustments, I just can’t seem to dial it in. I’m always hovering around .003 – .005 “out.” I know there are plenty of people who are going to say that’s more than fine for woodworking and I’m not here to disagree. The problem I’m having is that when I hold up my 12” Starrett combination square against the edge, I’m seeing light at the end telling me I’m not square.
One thing that I’ve noticed is that I can’t seem to reproduce the error. If I were to repeat the 5-cut process without making any adjustments to my fence, things don’t match. It’s almost as if the sled is moving out of alignment while pushing past the blade.
I have checked my alignment to the blade and when measuring from the right miter slot, the blade is aligned within .002. I have no issues with rip cuts in any manner. I get zero burning on either side of the blade and my cuts measure up within a few thousandths end to end.
I’m hoping that I’m just so frustrated I’m missing something clear and obvious here that is causing me problems.
As far as sled details go, I’m using 1/2” Baltic birch as my base, Rockler miter bars as my runners and a 2” thick, 4” wide piece straight grained piece of Beech. The sled itself is about 27”x27” and the fence is just under that at about 25”. My saw is a 3HP PCS Sawstop that’s just about a year and a half old.
Anyone have any ideas on what my issue could be?
Replies
Have you checked the square of your Starrett? I prolly wouldn’t use a combo square if you are trying to dial in that much accuracy.
I have. It’s spot on.
You should be able to get it to more accurate than a Starret Square - those are reasonably accurate over smaller pieces, but that isn't how you should check for square of your sled - you do that by checking each end of an offset after the fifth cut...
Here is the link I use to do it which is well written and straightforward:
http://valleywoodworkers.org/wp2/wp-content/uploads/2014/01/5CutMethodSquare.pdf
Thanks for the link, they do a good job of explaining the process.
That is the method I’ve been using, I was just saying that I’m trying not to get hung up on numbers alone, but let the results of the cut dictate how much more “accurate” I want to get. For example, when jointing boards, just because all the pencil marks are gone, doesn’t mean the board is actually flat and true, there could still be a bit of a bow to it, but a straightedge would be able to verify.
As good as they are a Starrett combo square can still be less accurate than. 003 over 10-12" after years of use and drops etc.
A fool proof method of checking square is to take a wide straight board and make a crosscut leaving at least 6" of material on both sides then flip one piece over and butt them together and hold them against a known straight surface. This will have the effect of doubling the error making it easier to measure, so if you are truly. 003" out of square you should have a gap at the widest part of. 006". If you do I would call it a day and start building something. Oh, and maybe order a good quality try square from Woodpecker, Bridge City or other top shelf manufacturer. I love my Starrett but in my opinion no combo square is ever going to produce the accuracy of a quality fixed try square.
I’ll give that method a try, thanks.
Guys, his method does not rely on a square, it relies on a series of cuts that multiply the error. See the video by William Ng. Its actually much more accurate than a square.
That said, all I ever did in the past was use a square and flip the boards along the cut, see if they are parallel.
To adjust, pull the sled back enough to access the screw.
If the fence needs to go in (forward):
1. Clamp a block to the base tight against the fence
2. Remove screw and insert a feeler gauge between block and fence
3. Clamp fence to block
4. Redrill and re-screw., r between the fence and a block [firmly] clamped to the base, remove screw, clamp the fence to the block & refasten.
If it needs to go back (rearward):
1. Insert shim between block and fence and clamp
Repeat 3 & 4.
Note: Drill a new hole for each adjustment. I've tried using over sized or slotted holes and that doesn't work.
Don't get too crazy with it, .003" in 12" is plenty close enough! Personally I think a "3 Cut" method is close enough.
Yeah, this is what I’ve been doing in an effort to square up my sled. The process appears pretty straightforward and I understand what it’s doing/asking. Which is a large part of why I’m getting so frustrated is because it makes it feels as if the process should afford a more efficient way of getting the results. There have been times where the calculation tells me to move the fence back .008, which I do and then on the next series of cuts, it tells me to move it back .008 again.
I built mine using FW contributor Tom McLaughlin's 3 cut method and I achieved dead on results. Follow this link and about halfway down the page (second Tom video), is a video where he explains and demonstrates.
https://www.finewoodworking.com/2020/10/23/stl227-tom-mclaughlin-is-serious-about-square
Thanks for the link, I’ll take a look.
What is especially user friendly about Tom's 3 cut method is that all the adjustment can be made without relying of math,,, it's simply a matter of adding or subtracting layers of tape
If you are making multiple 5-cut runs without changing anything and are getting different results you need to fix that first. Something is changing. Your sled is not fit to the miter slots well, the fence is not held reliably, the material is not held reliably, or the something is changing in the saw.
You can eliminate the saw by making multiple samples with a miter gauge that is well fit to the slots or maybe even my doing multiple rips off a plywood or MDF blank. You need to find out what is changing and eliminate that before you will ever get a reliable result from your sled.
If the saw checks good then you can turn your attention to the sled. The important thing in troubleshooting is to be specific, sequential, and diligent. Don't assume anything. Test each component carefully. Don't assume your saw is OK, assure your saw is OK. Don't assume you are holding onto the material tightly, clamp it if required and so forth.
There are only so many components involved here. Getting to the point where you are confident in performing the 5-cut method shouldn't take too long. Cracked castings that move a smidge under stress have driven folks nuts till they took the time to take a full and careful look at everything.
My point is that the time spent to assure things are what they seem will be less than repeatedly testing something that is changing when it shouldn't ;-)
Thanks for the thoughts, I’m definitely going to start from square one and go over everything with a fine toothed comb.
When you say make multiple samples, you’re suggesting to be test being able to set either my miter gauge or rip fence to a specific setting and confirm there’s no deviation between cuts, yeah?
Yes, if the results are not consistent, you probably have some slop with the runners. Make sure that they ride tight to the inner sides of the slots.
Double check your fence it absolutely straight.
Double checked, the fence is straight.
Circling back here.. If it's any consolation, I'm also struggling to get my sled aligned with the blade after needing to take the top off my TS. Having a bear of a time getting that last cut to square up on the blocks.
Always helps to know I’m not the only one going through the same pain, hah. Sorry you’re in the same boat though!
When you made the sled did you cut a grove on on the base of the fence for the sawdust to go and if not are you clearing off the saw dust between cuts. I made the William Ng sled and my cuts are dead on but dust will cause an issue. Good luck
I did, yeah. Made that mistake on the first fence and have since corrected. I always check to make sure there’s no dust or chips on the fence or stuck to the edge of the board before lining it up on the fence.
Question for the cleverer people out there...
Is it possible to get a sled to cut more accurately than your mitre slots are aligned with the blade?
I would have thought that no matter how square your fence is to the blade, the lateral drift during a cut would surely ultimately result in an angled cut as the wood is dragged across the front of the blade...
There is no lateral drift when the blade and miter slots are not parallel, you get a wider kerf, and burning and chipping if it’s really out of alignment.
@Robb_SS normally you would but the sled is locked into a straight path, so what Gulfstar said is true.
Same think applies to a radial arm.
Sawdust in the corner is an issue - good point
Still sounds like an unstraight fence to me.
Are you .003-.005" out of square after 5 cuts or 1 cut?
That’s the calculation result after 5 cuts.
Seems like a major win to me. You're not making parts for the space shuttle.
Yeah, ^ this.
With the 5 cut method, your claimed error of .003-.005" is a 4x amplification of your actual error off of 90 degrees. So, your actual error ratio is somewhere in the vicinity of .001".
(And don't forget, you're calculating an error ratio. So that .001" is the error over whatever length of piece you've cut.)
You're good.
All of that is clear and makes sense to me and I absolutely would be happy with that result if it carried over to the workpiece. The reason I’m frustrated is because despite the calculation number the results I’m physically seeing are not in line. When checking the cut with a square, I’m seeing an actual gap and I can’t seem
To figure out how/where the issue is coming from.
Yep
Actually, I am.
Just kidding. But I do prefer to not have gaps in my joinery that are avoidable.
I've had luck aligning crosscut sled fences by using a large square against the fully raised saw blade. I put one screw in the fence and rotate it till square, then lock in the squareness with a second screw. You can then do test cuts and evaluate them with the square or by putting two cut boards with their cut ends facing each other. I use a Woodpeckers 20 inch square for this, not my combo square.
Yes, thats what I did as well.
Don't forget that a crosscut sled that cuts true today may not tomorrow, depending on the materials you use and how they are put together. Getting a true 90 means a perfectly flat fence, and that's hard to achieve, even using plywood. A lot of shop tools are like that. The fence on my Powermatic jointer is square to the table in some locations and not others. Yet it does a good job.
I just saw an ad for a Woodpeckers crosscut sled that also cuts miters. An incredible piece of engineering, except it costs a cool thousand dollars. Made of phenolic and is of the one-miter-slot variety. The fence pivots to 60 degrees and the protractor is graduated in half degree increments. Woodpeckers claims a stop block on the fence set at X inches at 90 degrees will be the same length throughout the fence's pivoting range. And it seems to have an excellent stop block and ruler system. If I hadn't just bought a new miter gauge I'd be interested.
Did you ever check the fence for straight?
I did, yeah. Straight across it’s entire length.
The first thing you should do is tune your saw 100%.
The last sled I made was perfectly on with the five cut method right out of the gate. If you are looking for machinist type results you have to think like a machinist. Buy a MACHINIST square. I have two and only use them to check other squares etc. as they are heavy and don't ever want to drop them. Buy a plate made to replace your blade during set ups. Buy a tablesaw alignment dial caliper and get your blade plate 100% true to your miter slot.
I made my fence out of two layers of birch plywood as plywood will move less and then glued and screwed a jointed piece of maple on edge to the back side to straighten it and keep it straight. I then clamped a machinist straight edge across the face of the fence, clamped my square against the straight edge and table saw plate and locked the fence with clamps and screwed it in place. Cut was perfect. Checked the cut with the machinest square and five cut.
I forgot to mention, and I guess it's pretty obvious, but this method allows you to slide the table along the runners to check the fence before final screw down with just the clamps holding it. Just undo the clamp holding the square to the plate and slide back and forth. If it binds or gaps then your saw is not in tune or your runners are not properly adjusted.
I make my own runners because the darn things are so expensive and I make lots of sleds. Mill a piece of ash (if you have some, very straight grain, stable and very hard) 1/32 or so smaller in width than your miter slot and slightly less depth. I purchase E-Z lock 6-32 knife threaded inserts for hardwood 0.375 from Amazon. I use my dowling jig to drill a 5/16 hole in the side of the runner and screw in as many inserts as you want. This also allows you to make the runners as long as you want rather than use the stock sizes. Wax your miter slots and table top lightly and start out with the runners where they almost won't move. Slide the table back and forth until its smooth. You might have to tweak the inserts but as they are brass they'll wear in. If you have any movement of the wood as time goes on just tweak them.
Hi all. I'm new here, having found this really helpful thread. I've recently made a cross cut sled, and tried out the 5 cut method. I keep getting very inconsistent corrections: 0.32mm back, 0.501mm forward and just wavering between an acceptable tolerance.
I don't have a pressure gauge to check my saw's blade, and it is just a basic contractor (DeWalt) saw. But I have checked with a manual method (checked with a square by clipping a tooth of the blade from the mitre gauge and testing the same tooth at the rear of the table, it feels acceptable, but I could be too optimistic). I hope I've explained that well.
So having made no progress, I'm thinking off all the variables here, and did notice there was slight movement between the two halves of the bed, from when I cut the saw slot through the bed. So it appears the two halves of the bed are moving to accommodate pressure either in the sliders, blade or something when I'm performing cuts. Is this a common problem? Do I simply drive more screws into the leading (furthest) fence to lock in the two halves?
I hope I have explained this well -
Thanks in advance for any advice.
Best
John
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