A much more precise and quicker way.
https://www.flickr.com/photos/davidp...7635197231922/
A much more precise and quicker way.
https://www.flickr.com/photos/davidp...7635197231922/
Mike King: many thanks for the link!
Mike I will give you the quicker part. The precise would of course depend on the quality and tolerance the square is machined to as well as holding it in place exactly. The five cut is real precise when you want a machine absolutely dead nuts square.
You guys are both right. A good Long machinist square and a good accurate test machinist indicator (not plunge indicator made by fowler) like Starret, Brown & Sharpe, Verdict or Interapid. But every machinist knows how to certify the quality and accuracy of their own square and indicator by using cylindrical squares, serface tables, gauge blocks... Sure, Having all this machinist tools would be really nice, but they would come at a price that more than $10,000. I like to ask people sometimes how square is your square and can you show me how you check it? Don’t get me wrong, I am an indicator happy guy. But a half decent vernier and a set a feeler gauges will never hurt a woodworkers pocketbook to much.
The reason I brought this up is, this is about the second time I’ve use the five Process. I making adjustable mitre checking fixture. And I was wondering how often people use the five cut process, and/or understand the theory.
Mark, your way is actually pretty brilliant. The only problem is that the board would need to be perfectly flat and square around the outside before the cut. Your way would also check how much the saw blade angle is at. Your way you could use just a simple set of feeler gauges. Your way works on the exact same premise as a cylindrical Square, but as I said the board would need to be dead flat and perfectly square before the cut.
"The reason I brought this up is, this is about the second time I’ve use the five Process. I making adjustable mitre checking fixture. And I was wondering how often people use the five cut process, and/or understand the theory."
Matt
The beauty of the five step process is that it magnifies error to a point that can easily be measured,quantified, and corrected. It also does not require a super accurate, NIST traceable, vernier. It just requires one that is repeatable. ( I worked as Metrology Technician, in a mechanical standards lab, for a few years at work early in my career.( I have a pet peeve for seeing the word "accurate" thrown about. Repeatability, resolution, yes. Accuracy? Not without a NIST Cert.)
I've used the five step process, as presented by William Ng, a time or two, for purpose specific jigs, just to validate square, and test the method out of curiosity.
It works.
I've also made a quick sled, run it through the blade,set a speed square in the kerf and adjusted the fence to the speed square. That works too and is really quick.
I do find that the large triangle square I have from Brian Lamb, in concert with a dial indicator, will give me just as good a result, without turning the machine on or cutting any wood, as the five step process. That square I have is fairly expensive, and William Ng's method requires only a $20.00 vernier. Even the plastic $5.00 model at HF would do it, if you were careful with it.
I do agree that any wood shop should have feeler gauges, a nice vernier, and a quality dial indicator. These three things make machine setups so much faster and easier. I have a set of motor shims I picked up at a junk store. These are really nice for establishing a "known" reference, and since I have a whole box of them, I can leave them on the jig until I'm done.
Last edited by Mike Cutler; 08-12-2018 at 8:55 AM.
"The first thing you need to know, will likely be the last thing you learn." (Unknown)
I think the five cut process is more suited for sliding table saws. You need at least a one meter X one meter sheet that is stable. A sharp blade and do not take dust cuts to avoid deflection of the blade. For squaring a miter gauge or shop built sled for a table saw I think other methods would be better. When we used table saws and sleds I just used a square as Mike describes and had plenty of accuracy for the small workpieces cut on a sled. I never liked miter gauges for accurate crosscut and mitering work.
Mark’s method works really good for checking blade 90 and would think a good way to check a sled or miter gauge.
Matt, for checking miters you should look at Brian Lambs square that has provisions for this.
Last edited by Joe Calhoon; 08-12-2018 at 3:02 PM. Reason: spelling
Lamb square
http://www.lambtoolworks.com/products.html
I probably made a statement on my small slider post that there is no adjustment for the cross cut fence and its done with the bearing blocks and two of the three bearings in each block. These ride on the single bar. It seemed odd to me as even the mickey mouse sliding tables I had used for years have adjustment.
Last night looking at it or at least the one side the fence wasnt on I could see there is an eccentric block so you can adjust the fence as well. I guess the pins that drop in to locate the fence will move in doing so slightly as it must change the dimension between the two drop in points as well as you have a front and back fence position for the fence. On your bigger sliders do you have the ability and have to adjust for square in both the front and rear position.
Guys,
OK we have chewed this over pretty well, but nobody yet has mentioned the practical basis for choosing among the various methods. The practical basis is the tolerance within which you wish to work and the practical resolution of measurement (e.g., tape measure, dial indicator, feeler gauge). The most obvious place to start is the accuracy and resolution of the protractor on the miter gauge. The measurable angle on even a high-end miter gauge is too coarse for most narrow tolerance work. So, we find a way to increase measurement resolution. We use more cuts or longer test pieces to increase resolution. The "two=cut" method overlaps with the "five-cut" method depending on how large the pieces are. Unless you specify the tolerance and the resolution the argument about which method is preferable is pointless.
Maybe the best way to understand this is to decide on a maximum acceptable tolerance for the largest cut you plan to make. If you need to cut 48" wide pieces to a tolerance of 1/16" then trigonometry [tan(a) = rise/run] will tell you that the maximum angular error would be in the hundredths of a degree. You need a method like the "five-cut" to increase resolution. If you need to cut 6" wide pieces to the same tolerance, then you can tolerate more angular error and can use methods with lower resolution, such as the "two-cut" method.
Doug
There was an assumption on my part that if you are looking for square, you already have flat.
You can in fact use the same method to check the board faces are square; Joint two adjoining edges of a board, crosscut the boards in half and place one of your reference faces on a flat surface and the other face to face, you will see double your error from the squaring operation on a jointer. If you square faces from a table saw, refer to the first drawing to set your blade to table angle.
Wide sheet stock, i always just just crosscut then flip to verify, based on two parallel long edges from ripping. I don't do much sheet-stock and don't own a sliding panel saw.
assem1a.jpg
I check my saw once a year when I clean and lubricate it.
The 5 cut method works great for my saw, I check the fence in the fore and aft position....................Rod.