Thread: Chasing accuracy and convenience with sleds and mitre gauges

Hum . . . . . wouldn't it be better to use the blade as the reference point?

I use a 400mm Japanese precision square and holding one arm along the full width of the blade (careful to ago between the teeth) and move the loose mitre slide fence snug up to the other arm of the square and then tighten the mitre mechanism.

I guess all that does is check for squareness at one position along the mitre T- track but I don't think I have a way of adjusting the blade relative to the T-track anyway - at least I don't think I do.

bobL you are right. Aligning the mitre to the blade is super important.

Here is my "screw" method as shown here. It is bang-on super accurate.

I absolutely do not endorse Instructables (I hate it) but it shows the method.

Once the blade and mitre is accurate, its on to the fence and sled

On the use of the blade, one can also use a "record" made of MDF to the very biggest size your saw can handle. The bigger the radius, the more accurate the result.

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Here is another instruction, but perhaps more clarity with a jig as I used it.....

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Originally Posted by BobL

Hum . . . . . wouldn't it be better to use the blade as the reference point?

No! Aligning a sled or miter gauge using the blade relies on that blade being 100% (or close to) parallel to the slots. Your sled is moving via a slot therefore the fence of that sled should be perpendicular to that slot/movement
I remember seeing a video from the woodwork web channel where he deliberately had his blade a long way off being parallel to the slots and the effect that had aligning a miter gauge fence to the blade. Also not all blades are perfectly flat (co planer).

Originally Posted by barri

No! Aligning a sled or miter gauge using the blade relies on that blade being 100% (or close to) parallel to the slots. Your sled is moving via a slot therefore the fence of that sled should be perpendicular to that slot/movement

If the blade is not close to parallel to the slots isn't that just going to cause major jamming problems when sawing, whether the mitre gauge is adjusted to the slots or the saw.

A very good substitute for a machinist square is a large plastic drawing/geometry square from office suppliers as they are very accurately made. Set it up on spacer block to get it above the table surface and use a large screw in foot on the DI and the results will equal a machinist square.

I posted the above link using a DI many years ago and I always thought he had left a step out and that was aligning the slot to the blade either parallel or slightly toeing out to prevent the back of the blade doing a second cut and then square the fence. In essence the sled is a substitute for a sliding table saw and all manufacturers of sliders recommend that the sliding table toe out about 4 thou to prevent secondary cutting from the back of the blade and the fence is then squared to the blade. It sounds a bit contradictory but it works.

Originally Posted by BobL

If the blade is not close to parallel to the slots isn't that just going to cause major jamming problems when sawing, whether the mitre gauge is adjusted to the slots or the saw.

Bob, my first table saw, before I adjusted it, was a fair bit off parallel but all that did was produce a wider kerf similar to what you get with a wobble dado blade. No jamming. It still cut straight but provided I used the slot as a reference not the blade my gauges were still 90 degrees although still having that wider kerf. Also there were a few more teeth marks after ripping. My initial blade was about 12 thou off parallel and after adjusting to about 3 thou (I read that was an acceptable figure) my cuts were slightly smoother and the kerf was much closer to the blade width. My current table saw (Sawstop) is sometimes under 1 thou dependent on natural expansion/contraction. Sawstop actually recommends 10 thou as being an acceptable figure but I found that too big.

Makes sense thanks

Originally Posted by Aussiephil

Though i guess if you own a dial indicator then you likely own one or more machinist squares

this

but i would recommend a machinist square for doing all your precision aligning, like jointer fences etc.

Originally Posted by havabeer69

this

but i would recommend a machinist square for doing all your precision aligning, like jointer fences etc.

Or a plastic drawing square which is just as accurate, there is no practical difference between my machinist squares and my drawing squares. I haven't checked them on a surface plate against a cylinder square but I reckon it would be a close thing. see here Re: Anybody know the accuracy of drafting triangle (woodcentral.com)

Thanks barri, I'd not seen that - clever idea. Now I have a good reason to get myself a dial indicator!

I got a cheapie, Charlie, but it works fine


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Bob and others , I found the video I mentioned before of why you shouldn't use your blade as reference for aligning a miter gauge or fence on a sled.

Squaring a Miter Gauge Correctly - YouTube

Interesting info, thanks all.

Curious - how often do you all re-check/re-calibrate things on your TS?
I recall spending about half a day dialling everything in when my saw first arrived. It's a cabinet saw, so somewhat fiddly to get the alignment perfect (because it's the table that is moved, not the trunnions). But of course, once it's aligned, it's not gonna move. Well, that's my assumption anyway.

Out of curiosity, I checked my fence the other day, for the first time in 6 months, and found that the face was slight off 90 to the table. Easy to fix.
It's probably time to check the blade runout with the dial indicator again, to make sure it's still okay.

I suppose there's potential for small movements caused by arbor/blade changes, dust build up etc. I've definitely noticed that the positive stops on the blade tilt adjustment are no longer correct...

can also use an angle plate if a square is a bit awkward to get a dial indicator on.

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