Arbor Alignment Tool Idea

[John Baum]

I woke up this morning with an arbor alignment tool in my mind. Has anyone seen anything like this?

We normally set the arbor alignment on a table saw by measuring as carefully as we can the distance from two extreme points on the largest blade we can mount to the table miter slots. It struck me that a piece of 1/4" thick sheet steel in a Tee shape, the top of the Tee being 2-3" wide and as long as the front-to-back dimension of the saw table and the downward leg of the Tee being long enough to accommodate a precise hole to mount on the arbor like a blade. One side of the long leg could be strengthened with a length of angle iron; the opposite side and the arbor mounting faces could be machined by a shop set up to dress engine heads.

I sketched up my trusty Sears 113 29940 10" table saw from 1971. The arbor is roughly 2/3 of the way from the front edge of the table or at 18.25" of the 27" table. My zero clearance insert tells me that my 10" blade cuts a 9.5" long slot. For a 0.1 degree error in the setting of the arbor from 90 degrees, the blade is off by 0.0168" or ~1/64" whereas the tool is off by 0.047" or ~3/64" (the ratio is 2.84) so the improvement in the accuracy of the setup is improved by almost a factor of 3.

Can someone see a flaw in my logic?

Has anyone seen a tool like this?

Thanks

baumgrenze

[John Baum]

I no more than got this posted and went to do my back exercises before dinner than I realized this does not need to be this complicated. All one needs is a decent straightedge with parallel sides to push against the blade, maybe a magnet to keep it snugly against the blade, and most of what I propose is available. Any errors from out of parallel edges could be compensated for by checking the distances to both miter slots, both fore and aft.

baumgrenze

[Stephen Cherry]

When I've aligned the blade to the slot, I measure from the left slot to one point on the blade, rotating to make the measurement. The intention is to remove arbor and blade runout from effecting the directional alignment of the arbor.

[Rick Lizek]

There was a steel bar marketed 1/4" thick,10" long and about 3" wide with 5/8" hole in the middle and that became your reference point to measure from. I made one from a 1/2" thick steel bar and it worked fine. In one shop I worked at we had a Giben beam panel saw and when we changed the blade we would check the alignment of the blade by test cutting a piece of mdf and when you could see the teeth marks of the front and back of the blade on both pieces of the mdf you knew it was aligned. I could use this technique on other panel saws to line up the carriage and even small saws like 10" cabinet saws by cutting a piece of mdf on the miter guide. Works fine for me and is very simple to say the least. There's a point of being too anal and wasting time. Regular cabinet saws and blades aren't up to the accuracy of metal working machines. Powermatic considered .015" we'll within tolerance for the flatness of the table. When I hear folks talk about skewing their rip fence .002" I have to roll my eyes...

[Roger Rayburn]

Here is one approach: http://www.garagewoodworks.com/video.php?video=v15&category=align

[Bob Wingard]

Something like this ???




254079


254078


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The extra holes are of no consequence, and were put there to help secure the plate in a mill. This one is about 1" thick Aluminum plate, and seems to be very straight and rigid.

The base plate for the dial indicator jig has a spring-loaded center bearing, which keeps constant pressure on both side of the miter gauge slot at all times ... never need to adjust the "fit" ... EVER !!! Makes it very portable and easy to use on more than one saw.

[Jacob Reverb]

Can someone see a flaw in my logic?

The error in the straightness/flatness of your 1/4" steel "T" piece is likely to be larger than the misalignment of the arbor.

I'd just use the same tooth on the same blade, as others have stated. Then machine the wood, measure "for effect," and when "good enough," call it macaroni.

Remember, this is woodworking, not metalworking, and the tolerances aren't that critical anyway.

When people talk about a few mils of runout, I can only smile. The wood moves more than that from humidity when you breathe on it.

[Bob Wingard]

When people talk about a few mils of runout, I can only smile. The wood moves more than that from humidity when you breathe on it.

It is difficult to make a direct comparison between quality of finished cut vs. how wood moves. When people try to compare apples to bananas, ... I CAN ONLY SMILE !!!

[Bruce Wrenn]

I use a dial indicator and a piece if 1/2" Baltic birch with 5/8" hole drilled into it, and a center line scribed on it. Get hold of a copy of John White's book "Care and Repair of Shop Machines."

[Mark Burnette]

Everything contributes to accuracy. The arbor washers that came on my RAS caused visible blade wobble.