Dial Indicator, Shopsmiths' Modified

[JPG]

i.e. What holds the gauge a 'fixed' distance above the table?

Why TWO washers at each end?

[algale]

i.e. What holds the gauge a 'fixed' distance above the table?

Why TWO washers at each end?

Yep.

[dusty]

Forget slide. It looks like the entire jig would rotate/pivot up and down in the miter slot. The tip of the dial indicator can essentially move in an arc up and down. When moved from location to location (checking a tooth at the front and back of the blade) how would you ensure the jig had not rotated?

I guess I will have to use it some before I can respond with a reliable answer.

Keep in mind that this is not to be a universal tool. I put this together specifically to eliminate the Shopsmith setup that I opened this thread with. I intend to use it for nothing more than table alignment.

When I rest the jig in the miter track and push it it slides with the tip resting on the ZCI and restricted in length by the blade.

PS I added some images to show how I intend to make use of these. I zero both dial indicators in the same location (usually on the outfeed side of the table (blade) which is where I pivot the table for alignment). Then I position the indicators as you see they here and adjust the table to where the dial indicators both read the same. I rotate the blade and check the readings hoping for only minor changes. I do not subscribe to the "same tooth method".

[dusty]

i.e. What holds the gauge a 'fixed' distance above the table?

Why TWO washers at each end?

Nothing. The tip rest on the ZCI at the junction between the ZCI and the blade.

No specific reason for two washers. I suppose it would work just as well with one or even three.

Do you have a reason for why it should be something different?

[jsburger]

i.e. What holds the gauge a 'fixed' distance above the table?

Why TWO washers at each end?

Nothing. The tip rest on the ZCI at the junction between the ZCI and the blade.

No specific reason for two washers. I suppose it would work just as well with one or even three.

Do you have a reason for why it should be something different?

But if the ZCI is not dead flat and co-planer with the table top the indicator tip can move up or down at different locations causing inaccurate readings. Thinking a little more, I guess the ZCI does not actually have to be co-planar with the table top but it does have to be dead flat and be level with the table top front to back.

[dusty]

i.e. What holds the gauge a 'fixed' distance above the table?

Why TWO washers at each end?

Nothing. The tip rest on the ZCI at the junction between the ZCI and the blade.

No specific reason for two washers. I suppose it would work just as well with one or even three.

Do you have a reason for why it should be something different?

But if the ZCI is not dead flat and co-planer with the table top the indicator tip can move up or down at different locations causing inaccurate readings. Thinking a little more, I guess the ZCI does not actually have to be co-planar with the table top but it does have to be dead flat and be level with the table top front to back.

I have given no consideration to errors that might be created by a ZCI that is not flat.

How much variation must there be to create an erroneous reading in table alignment?

[algale]

I am struggling to understand what problem this solves compared to using a single dial indicator mounted in the miter slot and moved/slid between the two spots on the blade? I would think that would take less time to zero one jig and slide it in the slot versus zeroing both jigs against the exact same spot and then moving one to the back of the blade and hoping the geometry (tip angle) hasn't changed.

I understand the frustration that the jig sold by Shopsmith had some slop in the miter bar, but a little tape or paper should solve that problem.

I'm happy with my commercially made jig, which adjusts to the Shopsmith miter slot and has not slop. http://in-lineindustries.com/products/a-line-it-system/

[jsburger]

Nothing. The tip rest on the ZCI at the junction between the ZCI and the blade.

No specific reason for two washers. I suppose it would work just as well with one or even three.

Do you have a reason for why it should be something different?

But if the ZCI is not dead flat and co-planer with the table top the indicator tip can move up or down at different locations causing inaccurate readings. Thinking a little more, I guess the ZCI does not actually have to be co-planar with the table top but it does have to be dead flat and be level with the table top front to back.

I have given no consideration to errors that might be created by a ZCI that is not flat.

How much variation must there be to create an erroneous reading in table alignment?

I have no idea without some reference data. That is what makes the method suspect. You are using two difference reference points for the same measurement.

You have a horizontal reference for the gauge tip, the miter track. But you have an unknown vertical reference for the gauge tip, the ZCI.

[jsburger]

I am struggling to understand what problem this solves compared to using a single dial indicator mounted in the miter slot and moved/slid between the two spots on the blade? I would think that would take less time to zero one jig and slide it in the slot versus zeroing both jigs against the exact same spot and then moving one to the back of the blade and hoping the geometry (tip angle) hasn't changed.

I understand the frustration that the jig sold by Shopsmith had some slop in the miter bar, but a little tape or paper should solve that problem.

I'm happy with my commercially made jig, which adjusts to the Shopsmith miter slot and has not slop. http://in-lineindustries.com/products/a-line-it-system/

I am totally with you Al. I have the SS version and just push the assembly up against one side of the miter slot to make a measurement.

There is really no need for anything else but Dusty likes to reinvent things and that is fine. The discussions are fun and keep the mind sharp. Keep it up Dusty!!!

BTW, the jig in your link is almost exactly the same price as the equivalent Woodpeckers jig.

[dusty]

I am struggling to understand what problem this solves compared to using a single dial indicator mounted in the miter slot and moved/slid between the two spots on the blade? I would think that would take less time to zero one jig and slide it in the slot versus zeroing both jigs against the exact same spot and then moving one to the back of the blade and hoping the geometry (tip angle) hasn't changed.

I understand the frustration that the jig sold by Shopsmith had some slop in the miter bar, but a little tape or paper should solve that problem.

I'm happy with my commercially made jig, which adjusts to the Shopsmith miter slot and has not slop. http://in-lineindustries.com/products/a-line-it-system/

I might be content with your jig as well but I don't have your jig.

It does seem that the slop could be removed by shimming with tape but that did not work for me. Instead, I mage my own and have used it for some years now. The miter bar that I used on it came from my miter pro. When the need to use the miter pro arose and reassembled the miter pro and was left without a dial indicator. Last week I inadvertently created a need to realign the table thus the recent effort to redevelop the jig.

I understand the concerns/doubts stated by you and John but I feel I have this under control. Only time will tell. Can I align the table within a reasonable amount of time and to the self imposed specification of .005". We will see.

The two point method of table alignment has not been part of my procedure for several years now. I have no concern about that.