MAG-DRO Alignment Tool Option

[dusty]

With a dial indicator the 'zero' is manually set. Ditto the digital calipers.

My concern would be with those 4 'fingers that allow the body to meander across the miter slot.

I must be missing something here. When I get through setting the miter slot parallel to the blade (using the Shopsmith Dial Indicaor) do I know the distance of the blade from the miter slot???

[dusty]

Like Dennis I am thinking of other uses than just alignment. For one, once you know the precise distance from the miter slot to the blade as a reference you could use it to set the fence or any number of jigs dependent on the position of the blade...

I'm seeing this as a relative measurement, essentially the same as a dial gauge. Sure, the calipers give me an absolute number, but in reference to what? Can you explain how you'd use this to measure the precise distance from the miter slot to the blade? Seems like I need some precise way to position the caliper in the tool, and I'm not seeing that.

- David

An absolute number with respect to the "point of reference" when you zeroed. Zero at the edge of the miter slot or at a point known to be a specific distance from the edge of the miter slot (think setup blocks).

[JPG]

With a dial indicator the 'zero' is manually set. Ditto the digital calipers.

My concern would be with those 4 'fingers that allow the body to meander across the miter slot.

I must be missing something here. When I get through setting the miter slot parallel to the blade (using the Shopsmith Dial Indicaor) do I know the distance of the blade from the miter slot???

NO! The objective is to determine/make it so that the distance is the same both front and rear(which makes the slot parallel to whatever is being 'measured').

[stew]

I have this item and use it on my SS 520 table. It is a very tight fit in the miter gauge with no slop what so ever. The holder securely holds the calipers so no movement there. I would say that the accuracy is only limited by the accuracy of the caliper. I think this is a great option and it is always close at hand.

[DLB]

NO! The objective is to determine/make it so that the distance is the same both front and rear(which makes the slot parallel to whatever is being 'measured').

I agree. Same objective no matter how I do it. If I use this device with analog or digital caliper, the actual number it reads is not important, I'm just comparing the front and rear measurements. And the measurement it reads is also not the distance from the miter slot to the blade. If I wanted to measure the distance from the slot to the blade with precision, I think I'd do that with a caliper and not use this device. My earlier question was with the intent to get a better understanding of additional utility seen by others.

I have this item and use it on my SS 520 table. It is a very tight fit in the miter gauge with no slop what so ever. The holder securely holds the calipers so no movement there. I would say that the accuracy is only limited by the accuracy of the caliper. I think this is a great option and it is always close at hand.

Thank you, that is great to know. I don't know that I'd use it for alignment but I'd like to get one just to try it out.

- David

[miken]

So to try and answer a couple questions; it works best if you have a caliper that has a zero feature. I set the calipers depth gauge to touch a point on one side of the saw blade. I draw a point exactly where is contacts the blade with a pencil. I zero out the caliper to read 0.0 then slide the caliper in the miter slot to the other side of the saw blade while rotating the saw blade so the pencil point again aligns with the calipers depth gauge, which is now on the opposite side of rotation. This is supposed to be measuring the exact same point so its not supposed to even matter if the blade is slightly warped, it's the same point, same warp, etc.. You will then push the caliper to contact the same pencil dot and read the caliper. It will either show a positive or a negative number relative to zero. I then zero it again, and go in the opposite direction which yields the exact same number. Distance from the miter slot is not known or needed. It is really the exact same as the dial indicator (if you have a zero function digital dial indicator) but without the spring action (which you can fix with an elastic if it matters). I think it is a good solution for me at a fraction of the cost, but maybe it's not for everyone. It is a tight fit in the slot, but it does fit, and slide with effort, and has absolutely no slop. It is hard plastic and not at all flexible. The magnetic mount version works the same but you stick it to the miter bar on top of the lock screw to eliminate play. I wanted to use the magnetic base to tweak cuts using the fence. You make a cut purposely long, then use the depth gauge to measure it, subtract that number from the number (distance) you want, slap the magnet down anywhere near the fence, extend the depth gauge to touch the fence, zero it, then tap the fence over the amount you want to remove. Way harder to explain than watch on YouTube.

Thanks as always JPG and Ron for the picture taking tips.

[miken]

My concern would be with those 4 'fingers that allow the body to meander across the miter slot.

JPG, trust me, this thing isn't meandering anywhere. There are only two fingers on one side that push the device hard against the opposite side. On the other side there are two "bumps" one on each end that keep it parallel to the edge. Such a simple little device. When I saw it I thought I could easily make one, but not for $9.

[JPG]

2 fingers, 2 bumps = better than I thought as long as bumps are on the 'measuring' side.

[dusty]

2 fingers, 2 bumps = better than I thought as long as bumps are on the 'measuring' side.

Are the bumps on the 'measuring side'?

https://www.rockler.com/mag-dro-mitre-s ... 6dd1e86278

[miken]

Are the bumps on the 'measuring side'?

Hi Dusty, the device is reversible and can fit in the miter slot in either direction. Again, it is tight with no slop, and holds the caliper very rigid in either direction. For me, on my SS table, the measurements are completely repeatable as long as I don't move the table. Set the caliper, zero it with the depth gauge contacting the blade, slide the caliper back and forth along the miter slot a few times, go back to the original position and it still reads zero. It really cant get any better than that with my caliper (iGaging 6" OriginCal with Fractions).

For me, the device shows me the limitations of my saw more than anything. Once I move the table, or even unlock the trunnion, the measurement changes. I just did a test and locking the trunnion changes the measurement 0.005", unlocking it again brings the measurement back to 0.001", not to zero. Not enough to matter to me, but I can tweak the table for more precision when/if needed now.

Hope this helps, Mike -