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That takes care of one plane at some elevation.

Now about different elevations?

And the other two orthogonal plane(s).

Didn't Nick do a video on this issue? I know that once I went to the 520 I was able to switch the extension table to either end of the machine. However this requires the 520 to be aligned anytime I move the machine, push on the main table with enough force to move the machine(while up on wheels).
There is some flex in the machine on the left side that does not exist on the right side. I suspect it is because of being able to unlock the left side to lift it into drill press mode. My GUESS, is short of welding down the left side it would be impossible to adjust the machine and keep the alignment permanently.

Ed in Tampa wrote: Fri Dec 11, 2020 9:17 am Didn't Nick do a video on this issue? I know that once I went to the 520 I was able to switch the extension table to either end of the machine. However this requires the 520 to be aligned anytime I move the machine, push on the main table with enough force to move the machine(while up on wheels).
There is some flex in the machine on the left side that does not exist on the right side. I suspect it is because of being able to unlock the left side to lift it into drill press mode. My GUESS, is short of welding down the left side it would be impossible to adjust the machine and keep the alignment permanently.

Yes, Nick did a Sawdust Session Video with the intention of showing that the extension tables could be 'successfully' exchanged. However, I am unable to locate that video.

There is no doubt that a machine with double tilt is more easily assembled in a manner that will allow that interchange. I am in the process now of tearing down my 510 with the intention of reassembling it. The purpose being to convince myself that 510 extension tables are interchangeable.

I plan to assemble first with two [font=]Headrest Assemblies[/font]. This mocks the double tilt assembly without having spent the money. Purpose being to eliminate the effect that the Base Arm Assembly may introduce. Headrest should be Base Arm

Then replace a Base Arm Assembly with the Headrest Assembly. This makes it a legitimate 510/520.

If I was on a mission to determine why my e not be exchanged, one of the first things I would do is to make certain that ARE PROPER RELATIONSHIP TO ONE ANOTHER.

They should be at the same elevation and oriented so that the diagonal measurements are "equal" to one another. This diagram depicts only one way the diagonals can be measured. If they are not equal (or very, very close to equal) making them so is the first task at hand.

A certain amount of deviation can be over come by positioning the extension tables but this must not be done as a cure all. Get the Extension Table Legs square to one another first.
Note the relationship between the ends of the Bench Tubes and the legs of the Extension Tables. The legs could almost be used as reference points (stops) for depth of insertion of the Bench Tubes.

dusty wrote: Fri Dec 11, 2020 9:58 am ...I plan to assemble first with two Headrest Assemblies. This mocks the double tilt assembly without having spent the money. Purpose being to eliminate the effect that the Base Arm Assembly may introduce.

Then replace a Headrest Assembly with the Base Arm Assembly. This makes it a legitimate 510/520.

Did you say what you meant here? Two Headrest assemblies??? I'd say two Base assemblies is significantly closer as a mockup of a DT. And I don't understand the 'effect that the Base Arm Assembly may introduce" you refer to. Wouldn't the Base Arms introduce the same effect that they bring to the DT (goodness)?

- David

I THINK DUSTY HAS BASE AND HEAD REST FLIPPED IN HIS TYPING.

JPG wrote: Fri Dec 11, 2020 3:14 pm I THINK DUSTY HAS BASE AND HEAD REST FLIPPED IN HIS TYPING.

One of us has something swapped around.

I have three assemblies that I am playing with.

One is my 520 with double tilt. One is my 510 with the normal complement of Base Arm Assembly and the Headrest Assembly. The third is a Rube Goldberg that I through together with spare parts. In it I have the upper part of two Base Arm Assemblies. Corrected in the earlier post. This configuration was done originally with my Shorty to convince my self that extension tables could be swapped with no ill effect.

DLB wrote: Fri Dec 11, 2020 2:59 pm

dusty wrote: Fri Dec 11, 2020 9:58 am ...I plan to assemble first with two Headrest Assemblies. This mocks the double tilt assembly without having spent the money. Purpose being to eliminate the effect that the Base Arm Assembly may introduce.

Then replace a Headrest Assembly with the Base Arm Assembly. This makes it a legitimate 510/520.

Did you say what you meant here? Two Headrest assemblies??? I'd say two Base assemblies is significantly closer as a mockup of a DT. And I don't understand the 'effect that the Base Arm Assembly may introduce" you refer to. Wouldn't the Base Arms introduce the same effect that they bring to the DT (goodness)?

- David

I contend that getting rid of the headrest assembly and replacing it with Base Arm configuration is the salvation. It rids the system of the Headrest Lock mechanism. However, taking great care when locking down the Headrest minimizes the adverse effects that may exist.

dusty wrote: Fri Dec 11, 2020 3:51 pm ...I contend that getting rid of the headrest assembly and replacing it with Base Arm configuration is the salvation. It rids the system of the Headrest Lock mechanism. However, taking great care when locking down the Headrest minimizes the adverse effects that may exist.

I agree. The Headrest has a tenuous relationship with the rest of the system, in part because of the lock and in part because of how it mounts to the bench tubes. Those measurements I sent in the other thread represent what I consider typical, small but measurable rotational errors at the Headrest in two axes in reference to either the plane of rotation or the mounting plane at the Base end. Close enough for anything else, but not even in the ballpark for interchanging an aligned extension table. I can improve on that quite a bit, but the 'Holy Grail' was a one-time thing for me. I'd rather make another home-made DT if I thought I needed to solve it.

- David

DLB wrote: Fri Dec 11, 2020 4:41 pm

dusty wrote: Fri Dec 11, 2020 3:51 pm ...I contend that getting rid of the headrest assembly and replacing it with Base Arm configuration is the salvation. It rids the system of the Headrest Lock mechanism. However, taking great care when locking down the Headrest minimizes the adverse effects that may exist.

I agree. The Headrest has a tenuous relationship with the rest of the system, in part because of the lock and in part because of how it mounts to the bench tubes. Those measurements I sent in the other thread represent what I consider typical, small but measurable rotational errors at the Headrest in two axes in reference to either the plane of rotation or the mounting plane at the Base end. Close enough for anything else, but not even in the ballpark for interchanging an aligned extension table. I can improve on that quite a bit, but the 'Holy Grail' was a one-time thing for me. I'd rather make another home-made DT if I thought I needed to solve it.

- David

I understand and appreciate your assistance. This is an obsession for me, however, I will not drop it except maybe here on the forum. No one else seems to be interested.