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I don't think so and especially when comparing 510 tubes and rails to those of a 520.

It is raining and cold outside so I took time to sketch the rails and tubes so that I could SEE the slop. I conclude from my sketches (and I was very careful making the measurements) that the "unwanted movement is not greater than 1/16" and even that would be alleviated with proper alignment.

Remember - the table tubes are not reference surfaces. They are there to help stability

Pictures are worth 1000 words.

520 design is better than 510 but both displace rather than zero out slop because both use setscrews. 510 slop is x-y where 520 confines the slop to x. As the drawing shows.

Setscrews and wedges are inexpensive but imperfect. A collet-chuck design would have been the best way to zero out all radial slop.

I wonder why you are concerned about whatever slop there is in the Table Rails.

Alignment is in no way dependent upon the Table Tubes If you believe otherwise, please explain.

Because I want location repeatability - I want to be able to mount and dismount aux tables so they mount repeatably.

510 nested circular tubes setscrewed in place allow some non-repeatability of tube to tube alignment. The 520 extrusion geometry attempts to remedy this.

Alignment in this case means repeatable co-planarity of all aux table surfaces with the main table, every time aux tables are mounted.

SteveMaryland wrote: ↑Mon Jan 16, 2023 3:24 pm Because I want location repeatability - I want to be able to mount and dismount aux tables so they mount repeatably.

510 nested circular tubes setscrewed in place allow some non-repeatability of tube to tube alignment. The 520 extrusion geometry attempts to remedy this.

Alignment in this case means repeatable co-planarity of all aux table surfaces with the main table, every time aux tables are mounted.

OKAY...but I would be very interested in knowing how you would propose this could be done. I obtain table top coplanarity relationshipwith a straight edge across all tables involved after the Main Table height has been set. Unless you believe you can tie the tables together and then adjust table height (depth of cut) I see no other way. Please show me if you have a way.

The 'issue' of the 510 clamping method(horizontal) is that there is no GUARANTEE the inner connecting tube will vertically align with the mid point of the outer rail tube. The clamping screw CAN cause the inner tube to be slightly displaced vertically(up or down) differently on tables being connected. The torque of the clamping screw essentially guarantees that depending upon the lack of a square end on the screw..

The later 510 version somewhat helped this by making the rails adjustable by bolts through somewhat sloppy holes similar to the attachment of the 520 rails. The early 510 used tapped holes in the table to attach the rails thus providing NO way to adjust. The connecting rail vertical variability remained.

The alignment criteria is a common horizontal plane for ALL connected table tops.

JPG wrote: ↑Mon Jan 16, 2023 8:11 pm The 'issue' of the 510 clamping method(horizontal) is that there is no GUARANTEE the inner connecting tube will vertically align with the mid point of the outer rail tube. The clamping screw CAN cause the inner tube to be slightly displaced vertically(up or down) differently on tables being connected. The torque of the clamping screw essentially guarantees that depending upon the lack of a square end on the screw..

The later 510 version somewhat helped this by making the rails adjustable by bolts through somewhat sloppy holes similar to the attachment of the 520 rails. The early 510 used tapped holes in the table to attach the rails thus providing NO way to adjust. The connecting rail vertical variability remained.

The alignment criteria is a common horizontal plane for ALL connected table tops.

Assuming that the 510 Table Tubes are not all in the same horizontal position after being tightened, what adverse effect does that have on table alignment???

SteveMaryland wrote: ↑Mon Jan 16, 2023 11:53 am Pictures are worth 1000 words.

520 design is better than 510 but both displace rather than zero out slop because both use setscrews. 510 slop is x-y where 520 confines the slop to x. As the drawing shows.

Setscrews and wedges are inexpensive but imperfect. A collet-chuck design would have been the best way to zero out all radial slop.

I understand what you are saying but does this have any direct effect on table alignment. I think not.

In another thread on the same subject, I made the observation (viewtopic.php?p=305196#p305196) that the 510 system was unlikely to provide the same improvement to main table stability as the 520 when tying the main table to the extension table via connector tubes. Those of us that use this technique do so to maintain alignment of the main table during use, when there is weight or other force on the table that may cause it to deflect. The theory, admittedly unproven, is that slop in the rails (510) adversely effects main table alignment stability compared to less slop (520).

As a 520 user, I also agree with the coplanar argument. I align table height of all tables relative to the extrusions using the 520 alignment jig. Tables are interchangeable among machines. While it has no effect on main table alignment, it is part of system alignment. While I think I could produce acceptable results on a single 510 using a straight edge, I don't think I'd have the interchangeability between 510 systems.

Both of the above are relatively minor concerns. And perhaps add to the unproven concerns that Scott raised in his video regarding table sag and 510 fence alignment of floating tables. I don't currently have a 510 fence, can't really test things, but I see some valid if unproven concerns here.

- David

David,

Thanks and well said. I agree. The whole point of an alignment is to make straight & square cuts with repeatability. To my knowledge there is NO Shopsmith procedure documented for aligning floating tables and this is the crux of the problem IMHO. Based on the other thread and Scott's video it appears that 520 rails eliminate some variability in floating table placement compared to the 510 rails which becomes a problem when the fence is installed for rip cuts on the floating table. Having a perfectly aligned main table is pointless if a floating table is skewed when the rip fence is placed on it because the fence won't be parallel to the blade. How big of an issue this is has to be determined, but it is a difference.