Parallel Extension Tables

[JPG]

Just call it the Holy Grail!

[DLB]

Have you come to that same conclusion? Do you now have extension tables that you believe can be swapped back and forth? Has anyone who has read any part of this thread or of any of the others that exist been challenged to do the same? I would like some part of this community to achieve to that same level, I would like to be able to write a procedure that if followed by a newbe would result in the same.

I think that is a great but lofty goal. Not because I think it is important to be able to swap extension tables, but because I agree that the ability to do so represents a well aligned base. (Not including that giant anti-twist setscrew thing. But I also think this applies a very tight tolerance to a medium tolerance assembly.

I have achieved the same thing on a 520 using information provided mostly by Dusty and jpg in other threads. I have also failed subsequent to that on a 520 Shorty using the same knowledge. It ended up as close as I could get it until I later put home-made DT Bases on it. Based on the experience, I'm not convinced that it is a matter of being persnickety enough. Woodworkers in home shops are not going to have the sort of Precision Measurement Equipment (PME) on would need to confirm in-tolerance condition of components (assuming that we knew the tolerances) that would lead to success.

As implied in a couple of posts here, and consistent with my own experience, this comes down to assembling the Headrest to the Bench Tubes in a precise manner such that when it is locked to the Way Tubes its Accessory Mount Holes will be precisely aligned to replicate whatever error is present in the Accessory Mount Holes on the Base. IMO that is worth doing, but not to the level of precision necessary for table swapping. It was not designed to be precisely aligned in this manner. Somewhere along the line I've formed the opinion that it is most likely that Shopsmith assembles this on an alignment jig, but I seriously doubt that it produces the precision we are talking about here. In hindsight, now that I have a clear understanding of what this is and why it's hard, I would not try to align the Headrest for these results nor recommend it to anyone else.

- David

[algale]

Have you come to that same conclusion? Do you now have extension tables that you believe can be swapped back and forth? Has anyone who has read any part of this thread or of any of the others that exist been challenged to do the same? I would like some part of this community to achieve to that same level, I would like to be able to write a procedure that if followed by a newbe would result in the same.

I can not because ya'll can not.

I tried with my 520 and its extension table but could not get it close enough to swap if the goal was to use the rip fence safely. I even went to the trouble of disassembling everything and rebuilding it from the ground up, including squaring the headrest, and still it was a no go for me.

I'm skeptical this level of alignment can be achieve at all without a double tilt. And based on Reible's comment that his alignment with the double tilt didn't survive regular usage going to drill-press mode and back, I'm a little skeptical this alignment would hold for me even with a double tilt upgrade. I'm glad it seems to have worked for you. But if yours has been sitting with a jointer on it and hasn't been regularly tilted up and down, are you really sure your alignment has held?

[RFGuy]

Is this just an academic exercise? What I mean is there an overwhelming need/desire to install an auxiliary table in both left and right sides and have rip fence alignment on either side? I see it more as a right vs. left handedness discussion. Depending on whether you are right or left handed you can choose with the Mark V (or any tablesaw) which side you want to make your cuts on. Maybe I have never come across an application that needed the auxiliary table to be ambidextrous, so that is why I am asking the question here. From my perspective, I would prefer to continue to make tablesaw cuts on one side only to reinforce my muscle memory and hone my technique. Going back and forth from side to side just introduces another variable that might result in an accident, so I prefer to continue to practice on one side only.

IF the double tilt upgrade makes the Mark V base much more rigid then that is a good thing, but I wonder how many users have this upgrade? I certainly don't have it and never intend to purchase it. Even if a special alignment procedure could be divined that works to maintain left vs. right auxiliary table alignment, how many users would use it? I would guess only a small portion of Shopsmith owners have a double tilt, perhaps 5% or less, but I have no actual data to back this up...

IF there is a way to achieve this alignment, and a strong need for it, then why hasn't Shopsmith published this new alignment procedure in the last 70 years? Surely, they would have figured this out by now, right?

[dusty]

Have you come to that same conclusion? Do you now have extension tables that you believe can be swapped back and forth? Has anyone who has read any part of this thread or of any of the others that exist been challenged to do the same? I would like some part of this community to achieve to that same level, I would like to be able to write a procedure that if followed by a newbe would result in the same.

I can not because ya'll can not.

I tried with my 520 and its extension table but could not get it close enough to swap if the goal was to use the rip fence safely. I even went to the trouble of disassembling everything and rebuilding it from the ground up, including squaring the headrest, and still it was a no go for me.

I'm skeptical this level of alignment can be achieve at all without a double tilt. And based on Reible's comment that his alignment with the double tilt didn't survive regular usage going to drill-press mode and back, I'm a little skeptical this alignment would hold for me even with a double tilt upgrade. I'm glad it seems to have worked for you. But if yours has been sitting with a jointer on it and hasn't been regularly tilted up and down, are you really sure your alignment has held?

Admittedly, my two machines do not get exercised the same way. As stated earlier, one machine is home for the jointer. The other machine routinely changes roles between drill press and table saw/router configurations.


Maybe I need to alter that routine but not before I investigate the heath and welfare of the Base Arm Assembly,

To answer a question - is there a demanding need to have interchangeable extension tables? No there is not except for the fact that I have been told, directly and indirectly, that it can not be done and I know better. I can do that and I am going to do my best to explain how anyone who wants to can do the same thing.

[reible]

Just in case you may have missed this before....... and yes this has been covered in many many posts..... this is the word from Shopsmith on the subject:

ai1.jpg (201.03 KiB) Viewed 1235 times

ai2.jpg (173.92 KiB) Viewed 1235 times

My shopsmith has to traverse the reasonably flat garage floor to find a not so reasonable much less then wonderful drive way for most ripping operations. The fact that it keeps alignment to the degree it does is interesting if not amazing. But subjecting the machine to what it has to do for me is a lot different then for a lot of you. If the machine is stationary and on a nice flat surface and the stars align just right it is possible that the dual alignment might hold for a decent amount of time. But you need to keep checking it and if it is out of alignment it maintenance time again, not something I look forward to. The way it is having the two extensions I can go for years without having to play around, I like that.

Ed

[dusty]

Thank you Ed. Yes. I knew that statement was there. The logic, at least my logic, just does not allow me to accept that at face value. If the author had gone that extra step to explain why they are not interchangeable I might relax.

Right now I have my tables upside down on a flat work bench and am looking for reasonable explanations. Upside down on the flat surface is the way that I always performed the majority of table alignments. With this done (with all tables that are to go into a specific system setup, all that remains is to align the miter slots to the blade. When that does not work, the only conceivable explanation for me is that the four bores (for the extension table legs) are not properly oriented with respect to one another.

Again, thanks for the feed back.

[DLB]

...the only conceivable explanation for me is that the four bores (for the extension table legs) are not properly oriented with respect to one another.

It seems like everyone agrees on this point. Or at least that no one has disagreed.

I'm much less sure about doing the alignment on a flat surface, but if it works for you that's great. I follow the intent of the manual, but I do deviate in several areas.

- David

[bainin]

You guys are way more serious than I about parallelism and orthogonality. A quick check before starting is about as far as I go.

I understand the curiosity side here, and the desire for precision, and the question of origin of variance but I have to wonder where is the point for diminishing returns on actual quality of work coming from the tool ?

I know in my case, its not ANY of the tools I own that limit the results...its me and my stupidity and mistakes

b

[algale]

Dusty: Don't get me wrong, I wish you nothing but success in this endeavor. If I thought I could achieve this on my 520 and that the alignment would last at least as long as my main table alignment, I'd probably do it just for the sake of doing it. But I tried and failed.

But the need for a second extension table on the left side is, for me, pretty much non-existent. If I want a table to the left of the head stock, I simply mount a floating table to the left of the head stock using the tubes that go through my 520 fence rails. I usually use my 3 foot tubes which came standard. But if I want to go crazy, or need really wide support, I've got a set of six foot connecting tubes.

Those six foot connecting tubes will go all the way through the right side extension table, through the main table and through the floating table and permit a wider variety of support settings than a second extension table mounted on the left side because the floating table can be moved anywhere along the connecting tubes. With or without adding the adjustable legs that can go on the ends of the connecting tubes, I find this setup quite solid. And if I choose to rip from the left side floating table, which I have done a handful of times, I have no rip fence alignment issues with the floating table set up this way.