Insert Centerline

[JPG]

Hmmmmmmm. 1 3/8 + 3/32 = 1.469

[heathicus]

Dusty, I'm sort of confused about why you're putting so much work into getting the saw dead center in the insert. Wouldn't consistency of location be more important than it being dead center? If it's 1/4" off center, but it can return to that spot every time, it's that sufficient?

[JPG]

Dusty, I'm sort of confused about why you're putting so much work into getting the saw dead center in the insert. Wouldn't consistency of location be more important than it being dead center? If it's 1/4" off center, but it can return to that spot every time, it's that sufficient?

I cannot answer for Dusty, but as for myself, it is a matter of coming to understanding.

It is logical to expect centering of the quill to the table inserts, and the saw blade to those inserts.

There is a possibility that the enlarging of the rear trunion holes has introduced an offset due to increased range of motion when aligning the table.

The goal is to perform the table alignment such that all default(design) positioning is obtained in addition to blade parallel to the miter bar slots.

As Dusty has so often pointed out, when one zigs something, you run the risk of zaging something else inadvertently.

As a result of this discussion, the scope of parameters in aligning the table has increased.

Tis true that repeatability does not rely upon those added parameters, nor adherence to any particular method, but this is all a matter of defining the goals for the table alignment procedure.

Yes we may be seeking perfection or an unattainable result. Understanding it all makes acceptance of falling short of 'just right' possible if we understand why we fell short and realize the result is as good as can be obtained.

Understanding removes that nagging doubt that lack of it causes.

Trouble is, today's understanding may be incomplete. It is the desire to not have to alter our understanding in the future due to that incompleteness being exposed that drives me.

[reible]

Red has some good points here. But I think my thoughts would go along these lines.

A) We also need to remember that shopsmith was willing to replace the part so the likely hood of it being a design or manufacturing error goes way up, other wise why offer to change it for free.

B) When I got my 520 upgrade it came with the all the same size holes as did a 510 Ebay table I got. We have no idea how many "problem" ones exist but they seem to be related to 510's so far as I recall.

C) The over size holes or slots for table mounting exist on all shopsmith products so all table have a possible "center spot" but shopsmith doesn't include that in alignment instructions.

D) I feel that to get the other alignments done correctly is essential, not so the slot centering. In fact replacing a blade can effect the location of the slot as can a lot of other factors even if you do establish a "master" location.

E) I also think this is one of the reasons I have never been able to have a single fixed extension table align perfectly on both sides of the machine. Close yes, but I think it might be more getting lucky. I don't think it was ever designed to work that way. Even shopsmith says this in their manual. (If would be interesting to see with the new double ends on the new version if that was fixed.)

F) I did notice this because I built an insert for doing profile sanding and later finding that was not in the correct location. I traced that back to an alignment which had the location at a slightly different place. My solution was to make a flexible jig that allow me to match the output shaft to table location. I can't at this point think of anything this would not cover as a way to achieve adjustment for this issue.

E) If one were to assume that there is a single point where such a reference hole could be placed in the table for their machine then doing an alignment of all the parts could be though of as one of the needed alignment points. leaving on two more needed for that plane. I have no idea what points should be selected...

F) Has anyone looked to see the alignment/axes of the tilt mechanism? Might that not be yet another critical piece of the pie?

So anyway it has been a long long day and I'm out of here. Maybe tomorrow we can start on the 12 degrees of freedom and maybe move in to 3D world or is that a mountain too far?

Ed


[quote="JPG40504"]I cannot answer for Dusty, but as for myself, it is a matter of coming to understanding.

It is logical to expect centering of the quill to the table inserts, and the saw blade to those inserts.

There is a possibility that the enlarging of the rear trunion holes has introduced an offset due to increased range of motion when aligning the table.

The goal is to perform the table alignment such that all default(design) positioning is obtained in addition to blade parallel to the miter bar slots.

As Dusty has so often pointed out, when one zigs something, you run the risk of zaging something else inadvertently.

As a result of this discussion, the scope of parameters in aligning the table has increased.

Tis true that repeatability does not rely upon those added parameters, nor adherence to any particular method, but this is all a matter of defining the goals for the table alignment procedure.

Yes we may be seeking perfection or an unattainable result. Understanding it all makes acceptance of falling short of 'just right' possible if we understand why we fell short and realize the result is as good as can be obtained.

Understanding removes that nagging doubt that lack of it causes.

Trouble is, today's understanding may be incomplete. It is the desire to not have to alter our understanding in the future due to that incompleteness being exposed that drives me.]

[algale]

A) We also need to remember that shopsmith was willing to replace the part so the likely hood of it being a design or manufacturing error goes way up, other wise why offer to change it for free.

Very good point.

B) When I got my 520 upgrade it came with the all the same size holes as did a 510 Ebay table I got. We have no idea how many "problem" ones exist but they seem to be related to 510's so far as I recall.

Nope. My 520 had the same size holes.

C) The over size holes or slots for table mounting exist on all shopsmith products so all table have a possible "center spot" but shopsmith doesn't include that in alignment instructions.

One could say the same of contractor saws, which also have oversized holes or slots for the trunnions. While the trunnions on a standard contractor saw hold the arbor and move it relative to the fixed position of the table top whereas the on a Shopsmith the trunnions hold the table and move it relative to the arbor, both methods change the position of the blade relative to the table insert and thus would permit alignment of the blade parallel to the miter slots without being centered in the table insert.

D) I feel that to get the other alignments done correctly is essential, not so the slot centering. In fact replacing a blade can effect the location of the slot as can a lot of other factors even if you do establish a "master" location.

Agree.

[dusty]

I appreciate all of the opinions and points of view. I also know that what I am doing seems to most as much to do about nothing. I realize that having that saw blade come up through the insert centered on the insert center line is absolutely unessential and that not doing so creates no real problem whatsoever.

BUT guess what, I am so very close. So close that I now believe that what I strive for is what DeCristoforo and whoever followed had intended.

I am sorta thick and I know that. I have been told that by many. I have been trained that way. As a test engineer (my civilian career) I had two objectives. Test it until it fails and then test it to find out why.

Unfortunately, I no longer grasp the facts like I once did. Right now, I am sorta groping in the dark on this one. Part of the reason, my old boss would tell me, is that I have kept piss poor notes. "Where are your notes"? he would ask. "The answer is in there"!

I am close though and when I think I am there, I will then attempt to explain what has changed. Whatever it turns out to be probably is of little interest to most but to me it will have been a good ride.

Thanks for the feedback.

[robinson46176]

OK, you made me go down stairs and look at a couple of mine.
How about this... there has been several mentions of the trunnions shifting when being tightened. Suppose you attach small aluminum blocks to the underside of the table, one on each side of the trunnions (and as thick as the trunnion base). Attachment would require drilling and countersinking the table and drilling and tapping the blocks. The blocks would have to also be drilled and tapped horizontally. The blocks would be attached using "good" countersunk machine screws like below not dime store stove bolts probably 2 per block.
[ATTACH]16307[/ATTACH]

The horizontal holes in the blocks would then get something like a long set-screw in it. The setscrews would be snugged against the trunnion base on each side and then the trunnion cap-screws loosened just a little. The table would be adjusted by loosening one set-screw and tightening the other to push the trunnion which ever way it needs to move. Once it is all in proper position and locked in place by the set-screws you can then tighten the cap-screws firmly. The set-screws would keep it from shifting and also help hold it in place in use.
As an option you could do much the same but not countersink the table and and use common bolts. Then after it was all adjusted and tightened in place back off the set-screws and unbolt the blocks. The blocks would then be placed in a drawer somewhere and probably disappear forever.

Just a thought.


.

[algale]

Whatever it turns out to be probably is of little interest to most but to me it will have been a good ride.

Some of us along for the ride are enjoying the scenery too.

[dusty]

OK, you made me go down stairs and look at a couple of mine.
How about this... there has been several mentions of the trunnions shifting when being tightened. Suppose you attach small aluminum blocks to the underside of the table, one on each side of the trunnions (and as thick as the trunnion base). Attachment would require drilling and countersinking the table and drilling and tapping the blocks. The blocks would have to also be drilled and tapped horizontally. The blocks would be attached using "good" countersunk machine screws like below not dime store stove bolts probably 2 per block.
[ATTACH]16307[/ATTACH]

The horizontal holes in the blocks would then get something like a long set-screw in it. The setscrews would be snugged against the trunnion base on each side and then the trunnion cap-screws loosened just a little. The table would be adjusted by loosening one set-screw and tightening the other to push the trunnion which ever way it needs to move. Once it is all in proper position and locked in place by the set-screws you can then tighten the cap-screws firmly. The set-screws would keep it from shifting and also help hold it in place in use.
As an option you could do much the same but not countersink the table and and use common bolts. Then after it was all adjusted and tightened in place back off the set-screws and unbolt the blocks. The blocks would then be placed in a drawer somewhere and probably disappear forever.

Just a thought.


.

Might be a brilliant idea but the question becomes "Can I pull it off". Precision would be essential and I don't have as many tables to use as you do. Maybe you have a table of to that could be used as prototypes?:rolleyes::rolleyes:

[dusty]

Some of us along for the ride are enjoying the scenery too.

I get myself involved in these matters because it is what I enjoy. I just hope that there is something beneficial for others that comes out of it all.