My latest project requires me to rip some 1 1/2" Maple so I deicded to check blade alignment.
I cobbled together a jig similar to this
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check my setup
My alignment, which I think is OK, is 0.001". Not bad considering I used this method to align my blade
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(whoever came up with that technique is a genius)
The runout measuered on the body of the blade is 0.003". I think this is too much but it could be the 'silver' coating on the Avanti blade I just bought.
Is 0.001" alignment close enough? Is 0.003" blade runout too much? Is it OK to have the dial indicator angled so the measurement can be taken closer to the table or does it need to be 90deg? (as seen here, but not my site)
Hard to tell, I went looking for a decent combination blade over the weekend but couldn't find one. The Avanti (50T $30) blade cuts right through Maple but leaves hatchet marks. I will stop at the Lumberyard today and see what they have, I will probably end up ordering one of these:
Your measurements are only as accurate as the instrument you used to do the measuring.
If you mean the blade aligned to the miter slot, that real good. + .005 and it's generally considered that you have problems that need to be addressed
Are you sure that indeed measured "blade runout"/warp/flatness, and your measurement does not arbor or flange runout also?
There is a specific procedure for checking the flatness of a blade with that type of instrument:
With the instrument, find and mark the high spot on the blade; loosen the nut and turn the blade 1/2 turn on the arbor; re-tighten the nut check for the high spot again; if the high spot coincides with the marked spot, then the it's due to blade warp, if not, then it's arbor or flange runout.
Arbor and flange runout on a good table saw should be less than .001"
Personally, I'd consider that just fine. Before you judge any test rip cuts, you should also ensure that your fence is parallel to the blade and the mitre slot.
I love my WWII's, but a 24T rip blade is easier to use on thicker stock. When I have more than a few rips to do, I take the time to install the rip blade.
I've had Freud, CMT, and Ridge Carbide rip blades that I liked.
Happy with the results? Stop fiddling. A typical Forrest blade when new is with in .001". The arbor run out on my saw when new was .0005". When I check my fence alignment I make a test cut. If there were tooth marks on the keeper side I would slightly adjust the fence on the back side away from the blade. Tooth marks on the waste side, move the back side of the fence slightly towards the blade. Yeah, you waste "a" scrap piece of wood doing this and if your saw is decent you only have to do this once every 3 or 4 years, maybe.
Regardless of what kind of measuring equipment you use to set the saw up, you have no control over the fact that most wood does not remain dead flat or straight to the extent that those tiny measurements that you tweak you saw to come in to effect. They help but often wood can warp as you cut it. Wood often will move during the cut much more than the tolerances that you are looking at and then every thing becomes a moot point.
Or wait a little while and Ed will try to sell you an aligner that may or may not help with the results of your cut.
Good point, but to answer the question, NO ONE does that. However the closer to perfect you get the blade to being parallel to the fence or perpendicular to the miter slot the less sanding you have to do. Typically I NEVER have to sand a ripped or mitered cut.
You do not need fancy measuring equipment to set the saw up to make cuts like that. For some the measuring equipment makes it easier. For some it is an extra and unnecessary step. Results will tell you if the saw is set up right or not.
When fitting joints with a hand plane, it's fairly easy to take off a thou or two at a time. It's not so much measured as felt though...your fingertips can feel .003" fairly easily, it's roughly the thickness of a piece of paper.
Good idea. Like cherry, maple is prone to show scorch marks and any closed grain wood will make blade marks more obvious.
this
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to check my setup
That will do the trick for blade and fence alignment.
blade
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(whoever came up with that technique is a genius)
I'm wondering why you think the alignment is this close. See my comments below.
Is the "Ray Vojtash" of the Wood Mag article the same as "RayV" of this posted message? I'm not sure why you think the technique is special or better than any other "feel the rub" technique. It doesn't matter if you hold the stick (or bevel gauge blade) against the miter gauge or screw it onto the bar, it's the exact same technique.
It is a bit high, but not outrageous. It's probably not the silver coating on the blade (unless this coating is thick paint). This brings up the alignment question I mentioned above. How can you be sure of your alignment accuracy when the blade runout is three times higher? Did you mark a spot on the blade and make all your measurements on that spot (rotating the blade)? Or did you just run the indicator stylus along the surface of the blade?
Yes. In general, anything less than 0.005" is good enough. I've done a lot of testing with various blades and woods. Even with magnification, I could not detect any improvement in the quality of the cut surface for alignment error below 0.005"
It means that your cut surface will have ripples in it that are 0.003" deep. The size and shape of these ripples will depend on how high you raise the blade and how fast you feed the stock. This sort of defect can easily be seen and felt on exposed surfaces so expect it to require some extra cleanup. Good quality modern glues don't generally have any trouble filling 0.003" gaps between mating surfaces.
You need to determine if this runout is due to blade warp or an arbor/ flange problem. You can easily use your setup to check both the arbor and the flange. You will want to tilt the arbor so that the dial indicator can meet the surface of the flange at 90 degrees. You will want to leave the arbor at 0 degrees to check arbor runout. Hopefully there is a spot along the surface of the arbor where you can avoid the threads. You should see less than 0.001" runout on both of these.
The best practice is to keep the dial indicator plunger at 90 degrees to the surface being measured (zero degrees tilt). When the dial indicator is tilted at an angle it introduces error into the reading. The error is going to make the reading look higher than actual changes in the surface being measured. It will also exaggerate any instability in your dial indicator fixturing.
site)
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can calculate the actual geometry from the dial indicator reading. It is equal to the dial indicator reading times the cosine of the tilt (away from 90). The cosine of zero degrees is 1 (best situation). If you are tilting your indicator by 30 degrees, then multiply your readings by 0.86 to see what it would read if there were no tilt.
Tilting the indicator is a better alternative than using one of those flat blade replacement plates. Apart from the monetary savings ($40 or more), and the time you save not needing to swap out your blade, you won't be introducing a reference surface with unknown errors. The specs on one popular plate seen in catalogs and online are +/-0.003". You could think that you've aligned your saw properly when all you actually did was align it to match the warp in the blade replacement plate.
> (whoever came up with that technique is a genius)
sure is.
yes
That makes sense.
I'm going to check it by rotating the blade and then checking the arbor and flange. I suspect that this $30 blade is warped because when I've ripped with a good 80T blade I've nearly finish ready surfaces.
Thanks. I'll see if I can modify my jig to get it closer to 90deg so I don't need to look for my calculator.
The indicator I have does have a pin 180 from the working end but I would have to grind the lug off of the back to make using that worthwhile. I might be able to get the back lug to go below the table if I measure from the left side of the blade.
Your point about the blade runout equaling depth of hash marks on the wood makes sense to me so I will investigate that further. Thanks Ed.
Looking at your site just made me realize that I don't need the indicator near the table to check blade runout. I can do that up high. I just need to get it close to 90deg near the table to check my alignment.
This is very true. Most wood just can't hold these sorts of tolerances. Even the heat generated by cutting will cause dimensional changes on the order of 0.001". But, like you said previously, we're not talking about working wood to within a few thousandths of an inch. We're talking about aligning a machine. The goal here is to make sure that the machine doesn't introduce additional problems (beyond those inherent in the wood). You want to avoid having to clean-up or re-work something that the machine could have done correctly to begin with.
Wood does change dimensionally over time. So, the wise and skillful woodworker will not to allow a lot of time between cutting and fitting parts together. In other words, don't cut out all the parts one day and then try to assemble them on another day - especially if you expect the weather to change. Also, if you notice a board warping or twisting during a rip cut, it's a very significant sign that the particular piece of wood doesn't belong in your project. It was improperly dried ("case hardened") and will be nothing but trouble if you use it (reminds me of an armoire my brother made).
There's a "definite maybe" if I've ever seen one! Spoken with true conviction.
Hey! What's that sharp steel thing hanging out of my mouth? What the?!?!? Heck Leon, are you fishing again? Geez! Can't a guy offer some helpful assistance without getting trolled? I didn't suggest that he buy anything. With regard to his setup I said: "That will do the trick...". Is that what you Texas boys call the "hard sell"?
Exactly and as I mention in another post, I seldom need to address cut edges other than to bring them to the same smoothness as the other project when sanding.
Snip
LOL, "definate maybe", the earliest that I recall using that comment was in the Fall of 1972 when speaking to the store district manager. I was in my first year of college and the "definate maybe" answer to his question brought a "College Kid Answer" from him. ;~)
LOL, Ed I was just seeing if you were paying attention. ;~)
"David Todtman" wrote in message news:aYSQi.66141$th2.25985@pd7urf3no...
I used thin kerf for years because they cut so "fast". I was not happy with the cuts. They were never quite true enough for me and even with a stiffener which limited the depth of cut I was not happy. In 1989 I talked to my local tool dealer and blade sharpener. They still sharpen blades but do not sell tools. I asked what he recommended for a good combination blade. He recommended a Systematic combo "Regular Kerf". He told me, and I agree with that statement to this day that a "good quality and sharp" regular kerf blade will cut just as smoothly and effortlessly as any thin kerf blade. Plus you get flat bevels, miters, and compound bevel cuts. At the time I was using a 1 hp Craftsman TS and never again put a thin kerf blade on my saw. About 8 years ago I up graded to a 3 hp cabinet saw and immediately upgraded to the Forrest WWII regular kerf 40 tooth blade. A few years ago I bought another Forrest WWII to have on hand while Forrest resharpens the other. I also strongly recommend Forrest for resharpening. They can retune the blade if necessary when they resharpen it. If you are buying a cheap blade, a thin kerf may be the better choice but if you have your sat properly set up and want dead flat cuts a "Quality" regular kerf blade is the way to go. Thin kerf makes it easier for a low powered saw cut through hard woods. A sharp good quality regular kerf blade can do this also.
As for why you should not use a thin kerf blade on a 3hp saw, probably because the blade will not deliver the precision that a better quality saw is capable of delivering.
I will be the first to admit that I go overboard, but since I work to .0001 or so during the day, going to a .001 or so, doesn't seem like that big of a stretch.
Absolutely...if you don't get the machine accurate, the part can NOT be accurate without fiddling with something somewhere....easier to do it on the first operation, I think.
Also very right...the finish of the ripped board is what counts...assuming that you'll make an adjustment if the size is off, if the finish is there, that's most of the battle.
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