This week’s question comes from Peter from Charlotte, NC. He writes:
“I have purchased a used General International cabinet saw from a professional shop that was going out of business and I have a question regarding its set up. Using an alignment tool that I borrowed from the Charlotte Woodworkers Association I have been able to measure the alignment of the saw’s 10″ blade to the miter slot. According to the dial indicator, the back of the blade is 0.011″ further away from the miter slot than the front of the blade. In your opinion, is this amount significant enough to warrent loosing the bolts holding the cast iron table top and trying to get it to line up perfectly (say +/- 0.003″)? Or should I leave it like it is and just try to line the fence up to the blade as best I can? That actually brings up a follow-up question: should I try to have the fence align with the blade perfectly or should I have the fence slope away from the plane of the blade at the back so that wood doesn’t get pinched between the blade and the fence and kick back? How much of a gap does one put on the back of the fence if you do this?”
And here was my reply:
“Hi Peter. First off, congrats on the new saw! Now down to business. Let me start by saying that I tend to fall on the “less picky” side when it comes to machine setup. Personally I don’t believe that a pair of calipers or a dial indicator is necessary to set up any woodworking tool (ok there may be a few). But I don’t consider the tablesaw to be one of them. That being said, I would never discourage someone from trying to get things as close to perfect as possible. Its your machine and your time, and obviously better is better, right? But in my shop, a pair of magnifying glasses and a 1/64″ graded ruler work just fine.”
“So the heart of the question is, “How much error is too much?” And please keep in mind that this is only my opinion based on my experience. You will find MANY different opinions on this topic. And many will vehemently disagree with what I have to say. But after all your research, you have to do what your gut tells you. Now I find it easer to judge these numbers when I see them in the form that I use everyday: fractions. So 0.011″ is just about 1/90th”. The smallest measurement I ever use in the shop is 1/64th”. So 1/90th in my mind is about the same size as dandruff off a dust mite. Ok, maybe it’s not that small. But if my saw had an error of 1/90th”, would I ever even notice it?? Probably not.”
“But there are two other components to this issue that we need to consider: safety and cut quality. From what I can see, a blade that is slightly further from the fence at the back really accomplishes the same thing as a fence that slopes away from the blade. So having the blade off ever so slightly doesn’t strike me as a hazard in any way. And I am theorizing that it might actually be safer when ripping. (Emphasis on theorizing).”
“Now cut quality is the one area that might concern me. The blade tilting in that direction means that your rip cuts will be squeeky clean. Anything cut from the right side of the blade will be perfect because there is no significant contact with the teeth at the rear end of the blade. And a little known fact is that certain tool companies actually use this technique on their circular saws in order to get the best cut quality possible. But what about the left side of the blade? Think of a cross-cutting operation with a miter gauge. The work piece will be cut ever so slightly by the back teeth, which means increased tearout since the back teeth cut upwards. And remember, when you line up your cut at the front of the blade, the actual cut will be 1/90th” off after you pass over the back teeth. Again, is that enough to be concerned about? Probably not in my shop.”
“So now you are even more undecided than you were before. lol. Let me just tell you what I would do at this point. You already have the dial indicator. Get the saw in position, loosen the bolts for the top, and try to get the blade as parallel as possible to the miter slot. This isn’t something you are going to do all the time, so you want to take your time and be a little picky. This way you are starting out on the right foot from day 1. And in all likelihood, this saw will hold its setting for a very long time. Furthermore, you will get to know your new saw. And whenever you check alignment in the future, you can make the decision on how picky you want to be based on everything you’ve learned.”
12 Responses to “Table Saw Tuning”
Although I certainly don’t think your wrong about a table saw not requiring a dial indicator, Marc, I do think it makes thing much easier. I fought for years to get my conractor saw aligned. I also thought I didn’t need a dial indicator. After much frustration, I finally bought a dial indicator recently and saw my best efforts were resulting in an error of over seventy thousands.
Thus, while not necessary, a dial indicator sure is a nice tool to have. Mine is just a cheap example; around $20. It was well worth it to get finally get my blade parellel to the miter slot.
Hmm Marc, I think you misread the author a little bit. I think you assumed that currently his blade is further away from the fence at the rear edge but that doesn’t seem to be the case. It seems that it’s further away from the mitre slot meaning he could have a higher chance for kickback from the workpiece getting wedged between the fence and the blade. Although at that small of a difference it’s probably unlikely.
I think the most important advice given to Peter is to ‘get to know his new saw’
I shoot for less than .010 and have gotten to .003 on some occasions but that is partly my sometimes anal nature – But since I work on both sides of the blade – I always have the fence aligned with the mitre slot and the blade dead on.
Another thing to check before loosening the saw is chect the alignment front to back with the blade tilted to 45 degrees. If the saw has had a hard life (does happen) it may need to be shimmed. That misalignment can be more sever for kick-back since you pinch cutoffs under the blade .
I think you have the prime opportunity to really go through everything and once set I have not needed to change alignment on my Unisaw in the past 3 years
personally that 0.011″ is small. I admit that 0.004 would be better. But i don’t think have you have to worry about it. Just keep checking it every so often to make sure the number does NOT get bigger. If it does get bigger, than i would adjust it!
thanks
I see what you are saying Cody. Peter’s original email didnt specify which miter slot he was measuring from. Fortunately, I think my explanation and advice are still valid regardless of which miter slot he is referencing from. Subsequent emails with Jim confirmed that he completely understood and is enjoying is new saw.
It is no wonder the name The Woodwhisperer has stuck. Your opinions are always given with the caveat of “whatever ends up working best for you”. While some of us are fine with very close, others of us like to take things to the extreme. You always offer
the best way to do both. It always boils down to our own experience or lack thereof. At least your site gives us a place to get a seasoned opinion and many, many more from your loyal, often opinionated, fan base.
Just so everyone knows: vibration from the table saw itself can cause the lower trunnion assembly to move over time. So if there is possibility of danger thu the assembly moving around or coming loose, that 1/90th of an inch can be dangerous. As long as it stays put (the 1/90th that is) then you should be okay. Make sure everything is tight. If not, use semi-permanent (blue loctite) on the bolts to make sure your saw stays put! “cough”+”Cough” safe.
lates
This is a good reminder to check the alignment of the blade to the miter slot. I have not done it in over a year and have never had to adjust it. I am a little intimidated with the idea of adjusting my jet cabinet saw. It could be one of those things that sounds straight forward but ends up being a long frustrating day and the tool is more out of alignment in the end. Hopefully the saw is still in alignment and I can do what I enjoy most, making saw dust.
I tend to agree with Dave. I always shoot for less than .010 when I’m tuning up my Unisaw. I think the first time tune-up of a newly acquired saw should be “complete” tune-up to so you know exactly what you have. This may take longer and you will need help taking the table off, but I think you will be better off with this first time tune-up. If the blade isn’t aligned to the miter slot at 45 degrees, a cut made with the blade tilted can be dangerous at worst and have burned edges at the least. FineWoodwoking.com has an excellent article on this procedure by Roland Johnson from issue #179 of Fine Woodworking.
Good Luck
One thing to keep in mind with respect to tolerances is that they can multiply on themselves. A 1/90″ gap can soon become much larger with successive passes. Depending on the joint involved, it could become a visible gap. As Marc eluded so well, we all develop our own level of tolerances. I don’t own a dial indicator but often use the right lighting and my own eye to judge tolerances. An interesting discussion.
Is .011 out of alignment too much? Probably not, but then I have always adjusted my saws to .003 or less. For what it’s worth, my Jet saw came with a spec sheet on actual measurements and allowable tolerances and the allowable blade-to-miter slot tolerance is .0118. Given that, your saw would be within spec for Jet’s quality control.
However, it’s also worth mentioning that your total error will probably be greater than .011. Blade runout will add to the total, so if your blade has say .010 of total runout, then add .005 to the .011 and now you are out 1/64″. I’d rather have the alignment better than the .011 number so that a less than stellar blade doesn’t create burn and/or the potential for kickback.
Also worth mentioning is that there is one school of thought that advocates having the fence taper away from the blade at the back. The people that like their fence set up this way typically mention .010 to .016 (1/64″) as the amount of total taper. It might appear to be about the same as having the blade misaligned by .011, but that’s not the case. A taper of .013 over the length of a 40″ fence is about .001 for every 3 inches. Measuring the blade above the table with a dial indicator, you are measuring somewhere around 6″ length, give or take, from the front to the rear of the blade. That figures out to nearly .006 for each 3 inches, which is 6 times the amount of taper in the fence in this example.
Having said this, I wouldn’t get hung up on all the numbers. The quality of the cut will tell you more about what needs adjusting than the dial indicator will.
Ironically, I just went through this same process on my old craftsman and found it was out about .010″. I didn’t think this was terrible, but thought I could get it a little better and after about three hours of cussing, standing, kneeling, and laying on cold concrete, I ended up at .003″. Was it worth it? I am not sure, but as I am a relative newbie, I wanted the saw tuned as close to perfect as possible. That way, when things come out unsquare or generally “off,” I know its my technique and not the saw’s setup.