Fine-Tuning for Accurate Cross-Cuts

starting with zeroing in your square itself. July 28, 2007

I have been trying to find a way to get perfect crosscuts every time without success. My Kreg jig, miter saw, and crosscut guide on my table saw all have variations from cut to cut. The variation is very small but it still affects my face frames. Can anyone recommend a good machine or technique that you use?

Forum Responses
(Cabinetmaking Forum)
From contributor A:
First things first - that is, the device used to measure for squareness - the steel square. First, learn to check and adjust your squares. You need a good straight edge too. Use the straight edge to make sure you have a perfectly straight edge on the wood that you use to check your squares from.

Hold the square base solidly against the straightened edge of the material and mark a line with a knife or razor blade. Now, flip the square over and align it at the mark at the edge. Any variation or distance that the other leg of the square is away from the mark at its end point is exactly twice the error in the square. Adjust the square until it reads the same when it is flipped over.

Framing squares can be adjusted with flat hammer blows at the intersection of the two arms while against an anvil or other hard flat surface. If the arms are too far open to be perfectly square, strike with a flat hammer blow near the outside corner of the two arms. If the arms are not open wide enough to be perfectly square, strike with a flat hammer blow near the inside corner of the intersection of the two arms. While adjusting with the hammer, go back to your "testing scrap" and make new marks until the square reads perfect.

Other types of squares can be adjusted by carefully tapping the square on a bench until it reads perfect. Common sense will prevail as to adjust different types of small squares without damaging them.

With perfectly true squares, you are now ready to true up your crosscutting setups. I prefer a tight table saw sled over anything else to crosscut my face frame parts. Nothing is more rigid than a table saw so all that remains is for you to make a good and accurate jig. If you are using a factory miter gauge to cross cut, those are almost always sloppy in the slot and therefore very difficult to get consistent results with. They can be modified to perform better but my typing hand is tiring.

Whatever tool you decide to use to crosscut your parts with, remember that if the fence isn't straight or if the material you are crosscutting isn't straight, you cannot get reliably measured square results. When checking your setup, make sure to use a piece of scrap that is straight and check your results with a "tuned square". Square can only be measured accurately from a straight line with hand held squares. Corner to corner measuring is a good method for overall squareness of assembles and large rectangular or square shaped parts.

From contributor B:

If you follow contributor Aís advice, you will get square parts. I use my sliding table saw cross cut fence, and I get fantastic face frame joints with it. Chop saws and radial arm saws won't quite do the trick, but a CTD chop saw or another heavy duty industrial chop saw will work great. Sometimes I quick cut a cut on my Makita or old Dewalt Radial Arm saw, and I never get the same cut as the slider, or if I was to use my retired CTD saw. A sliding sled on a table saw should work very well.

From contributor A:
I forgot to mention that although you are trying to get square ends on the relatively narrow dimensions of face frame members, I am talking about framing squares. The reason is that if you can get your crosscutting set up to be accurate enough to where a true framing square shows that a cross cut 23" cabinet shelf is square, that set up will definitely be square for something narrow like stiles and rails.

From contributor C:
Contributors A and B are correct. I'll add that you need to have straight, flat and squarely S4S'd stock. The stock needs to be faced and edged on a real joiner, then planed all four sides in such a way as to preserve square. Alternately, you can have stock run out on a good 4 to 6 head machine. If you buy face frame material, inspect it all and accept only the perfect material. As you know, imperfections have a way of multiplying.

As for cross cut sleds, get the guides that can be width adjusted, then true up your t-saw grooves so they are smooth but with no sideplay. Miter saws are inherently problematic - they are disposable. CTD makes an excellent saw, just be sure to put CTD blades on it, or it's no better than a throwaway saw.

Patternmakers developed a methodology of making and keeping things square and true. You need to do the same. Some things will defeat you even if you do your best - like the toss out miter saws. A great blade will minimize the problems, but you have to hold tongue right for every cut.

From contributor D:
To contributor A: I like your method for adjusting a steel square. An old timer showed me the same thing years ago to true up my squares, except he used a nail set to make the adjustments. I have a lot of homemade jigs that I use for cabinetmaking and the only time that they will produce accurate cuts is if I fine tune them first with an accurate square. Once I do that the finished materials have some very close tolerances.

From contributor E:
I third, forth and even fifth the motion about how important it is that your squares are "square". Too often, people think that just because it's a brand new tool, it must be square. NOT! I had a brain fart day a few years back and could not for the life of me figure out why my pieces were not cutting square, even after I re-set it. I completely forgot to check and see if my square was square and sure enough, it was out a good 1/16", which over 24" is a lot.

For those of you who made your own sled, it's been a long while since I made mine and wasn't too happy with the way it turned out. I used solid wood for the miter slots and screwed it into the plywood sled. Do any of you have pictures of yours or can refer me to a site to get some ideas on how to make a better one?

From contributor A:
To contributor D: I read the same thing in a book a long time back about using a punch to adjust a steel square. About 8 years ago, I bought a really fine old square at an estate sale. It was the real deal with high quality steel that tapered from really thick at the junction of the arms to a bit thinner out at each end. I like to use the used tools I buy and I wanted to true it up but I hated the thought of marring it up with a punch like I had always done to my modern squares. So, I decided to see if just flat non- marring hammer blows would work on the anvil to adjust it. Well, sure enough it worked fine and I am sure any blacksmith could have told me it would.

From contributor F:
Thanks for all the great advice. I went out and purchased a good machinist square so that I could recheck some of the equipment around the shop. The biggest problem I'm having is my crosscut sled. I own a Jessem and no matter how much I adjust it, it is not so accurate on wider cuts. I am cutting shelves for a custom built in and over 9-1/2" I am off a good 32/ which adds up. I have mailed CTD and am waiting for a quote on there 20" cut off saw. Do any of you have any experience with this saw?

From contributor G:
I agree with all that was said about squares. That's where it ends. I have a 1943 Dewalt radial arm saw that I took the time to set up for perfect 0 degrees. Thatís all I use it for. I never change anything on the setup and it gives me perfect face frames on a consistent basis.

From contributor H:
I agree with contributor G on a dedicated set-up. We have a slider also, and an Excaliber attachment. We get great clean crosscuts on these, but we always check them for square at the beginning of every run. I finally broke down and bought a Dewalt 12" compound saw and Biesmeyer 8' fence system and called it good, for me, but guys were always complaining about cut.

Here's the low-down. The saw has got to come up to speed - indicative of the table saws and radials, and of course the upcuts. Next, the stock has got to be held tightly against the fence also. It works great with the table and radial saws. Of course the upcuts get the air clamping treatment. You should be able to get a relatively square and true cut with about any of the saws on the market and the right blade combination, but as contributor G stated, dedicated helps a lot.

From contributor I:
I agree with everyone on the squares. I bought a new framing square at a big box - 1/8" out (1/4 between scribed lines). Youíve got to check them. But I agree with contributors G and H about mitre saws and radial arm saws. Like any other tool, they are only as good as the setup. We've got an old 12" DeWalt radial arm (25+ years old) that will crosscut 18" as dead on as you can measure. 16" x 36" door panels are to within 1/128" (as small as my eye can see). Our face frames and door are cut on a newer Dewalt 12" mitre saws with Tigerstops. Yes, we've had people not check square on the radial after moving it from 90 degrees, and pay for it. But any tool needs to be checked at some interval, and any time either the cutter or the indexing mechanism is changed or adjusted. Itís funny that with a Homag beam saw, Weeke p2p, we still use the old radial.

From contributor J:
I use a 14'' Maggi RAS that is set as above post and never moved and checked often, even with a new 14'' CMT blade I will get a small amount of blade deflection, but if I use a sacrificial board that get the deflection the FF stock is square, with the big RAS's you can cut all the stiles in just one pull of the saw. I also have found that blade deflection shows up when you have all deflection assembled in the same direction, mix it up and it will pull against itself and give square face frames. It's harder to explain than to do. Many people use a $300.00 10''chop saw and get fine FF cuts, but when you use a true industrial RAS that cuts square and you learn a system that is fast for you, you will never want to work without one.