Table saw alignment: How close is close enough?

[Marty Tippin]

Just got a new A-Line-It tool and in checking my Grizzly hybrid saw, I find the blade to miter slot alignment is off by 0.0025" (25 ten thousandths) - that seems pretty close to me, and I'm betting that if it loosen the bolts on trunnion and start moving things around, I'll either end up worse off or no better than my current measurement.

So how close is "close enough"? Any reason to tempt fate and try to get the alignment any better?

[Mike Chalmers]

I would definitely call that close enough.

[paul cottingham]

I've got a delta contractor saw. Never adjusted it. My woodworking problems don't stem from my saw. Wood is too dynamic, and life is too short, unless aligning tools is one of the joys of the hobby for you. And if it is, more power to you!
It sounds like you have it dialled in perfectly.

[Richard Wagner]

Now if it was me, I would attempt to dial it in to .000" but that is just me. I love to tinker with opportunities such as you have. If you was do dial it in to anything closer than you already have, I seriously doubt that you could tell the difference in any wood working that you might do.

Go get a feeler gauge and check to see just how thin .002" or even .003" really is. I would call that "dead on" for a table saw.

[Bryan Wiesendahl]

I think the blade wobbles more than .002 when it's spinning through wood...

[Bruce Page]

I'll either end up worse off or no better than my current measurement.

That's exactly what happened when I tried to dial in my old Craftsman contractor. I never could improve it and I'm pretty good at dialing in machinery.
I was able to dial in my Unisaw but tapping a cabinet saw top around is a lot easier than tapping a trunnion around.

[Don Jarvie]

Set the fence to x inches and rip a board. If it measures x inches the whole length then it's fine. If it isn't then fix it.

Like you said you'll probably make it worse.

[Jim Becker]

It depends if that variance is toward or away from the fence at the back of the blade...

[William A Johnston]

I've been a carpenter most of my working career and am just getting into the craftsman side with working with all hardwoods and wanting to start building furniture etc.. with all different types of wood joints, and I keep reading posts of machinery adjustment to thousands of an inch. Isn't wood going to expand and contract more than .0025 inch? Or isn't human error going to come into play when pushing a board through a table saw or jointer. That's about the size of a human hair.

I would say you are good and I l need to learn how to really calibrate all my equipment.

I guess I'm truly amazed how accurate some of you can dial in a piece of equipment.

[Marty Tippin]

I guess I'm truly amazed how accurate some of you can dial in a piece of equipment.

My saw is as it came from the Grizzly factory; I didn't expect it to be nearly as well aligned as it was.

I'm definitely not going to mess with it - but I will spend some time getting the rip fence aligned...

[Jim Becker]

I've been a carpenter most of my working career and am just getting into the craftsman side with working with all hardwoods and wanting to start building furniture etc.. with all different types of wood joints, and I keep reading posts of machinery adjustment to thousands of an inch. Isn't wood going to expand and contract more than .0025 inch? Or isn't human error going to come into play when pushing a board through a table saw or jointer. That's about the size of a human hair.

I would say you are good and I l need to learn how to really calibrate all my equipment.

I guess I'm truly amazed how accurate some of you can dial in a piece of equipment.

While it's true that the material we all work with is ornery relative to seasonal movement, there's still a lot of value in making sure our machinery is adjusted accurately. Things often work smoother when adjusted to accuracy. And there are some adjustments that do affect safety, such as the relationship between the rip fence and the blade and the blade to the miter slots on a table saw. And the challenge to adjusting "that close" can even be "fun"... ...at least for some folks.

And interestingly, you don't necessarily need fancy equipment to "dial things in" very close...even some simple shop-made jigs will do very well with some thoughtful execution of the same.

[Art Mann]

If you bought a saw with the trunnion mounted to the table top rather than the cabinet, then I predict that getting it any closer than 0.002" will take approximately forever. I spent hours with my contractor saw getting it down to 0.003" The problem is that no matter how much time you spend getting the trunnion just in he right position, you will get greater than 0.002" of movement just when you tighten the fasteners. You literally have to guess how much the trunnion moves with respect to the table and adjust in the error so that it comes out right after its tightened down. If you check it again a week later, it may very well be off by that amount in either direction. Table saws are not machine tools and aren't made to hold that kind of accuracy.

[Jay Radke]

in general this thread overall, not just this post reminds me of my first class of college chemistry. it was accuracy vs precision. many people think they are the same when in my work a day world (basic science research) the two are far from the same. lucky for us as wood workers we have ways of making things more accurate that I have at times at work.

so if your worried about being off 0.0025" use a shooting board to square up and end up at the exact right dimensions. just make sure you always use the same measuring device however, because not all are as accurate as the next...and some make it hard to be precise every time you read them.

[Thomas L. Miller]

What Jay said! A good shooting board, a good plane and marking gauge and you can get bang on .0005" at a time. Get close with the machines and then dial the fit with the hand tools. Avoiding working from measurement and using directly marked parts works well too.
As you get older seeing 1/64" marks on a steel ruler gets harder and harder!
Tom

[Art Mann]

Remember, 0.002" is about half the thickness of a sheet of common notebook paper. The wobble of the blade will create a kerf wider than the tooth width plus 0.002".