520 Extension Table/Fence issue

algale · Post by **algale** » Sat Jun 23, 2012 1:25 pm

dusty wrote:Okay, I watched the video again this time paying a bit more attention.

Please, one more verification.

Lift the rip fence off the problem table. Now set it back on the table and forcefull hold the fence tight again the rail while sliding it to align with a rib (to get a good reveal). While still holding the fence tight, lock the bottom lever. Now lock the top lever while watching the fence. Does it relocate itself.

OK, I have posted another video, my greatest masterpiece so far

, with all of the tests you have requested (and more) being performed. Don't forget me when the Oscars roll around!! Here's the YouTube link: http://youtube.com/watch?v=sSmOf-TuwAk

dusty · Post by **dusty** » Sat Jun 23, 2012 1:51 pm

algale wrote:OK, I have posted another video, my greatest masterpiece so far , with all of the tests you have requested (and more) being performed. Don't forget me when the Oscars roll around!! Here's the YouTube link: http://youtube.com/watch?v=sSmOf-TuwAk

You are definitely the front runner for the next Shopsmith Oscar]Note: Using the conical disc and the rip fence (very carefully positioned), I cleaned up all the edges of my floating and extension tables for reasons that you demonstrated in your video..[/SIZE]

algale · Post by **algale** » Sat Jun 23, 2012 4:36 pm

dusty wrote:You are definitely the front runner for the next Shopsmith Oscar]Note: Using the conical disc and the rip fence (very carefully positioned), I cleaned up all the edges of my floating and extension tables for reasons that you demonstrated in your video..[/SIZE]

Uh oh. You know things must be very bad indeed when Dusty gives up! Unless anyone else comes up with an idea, I think I will remove all the rails, reinspect and reinstall.

Ed in Tampa · Post by **Ed in Tampa** » Sat Jun 23, 2012 5:06 pm

Put your square on the fence rail and the side of the extension table. It shoud be square however the rail may extend past the side of the extension table making this hard to measure.

Perhaps rather than the side of the table you can check a groove to see if the fence rail is exactly 90 degrees. Check the main table fence rail also.

Another thing you could do is take the fence rails off the extension table and see if the bosses where the fence rail set is parallel with the edge of the extension table or groove in the table.

One last thing take the fence rail off both the main and extension and see if bosses in the main are in the same plane as a extension table bosses.

I suspect one table boss is slightly proud of the other making the fence rail sit sightly out of parallel with the actual table. It doesn't have to be much to cause your fence end to telegraph that slight difference into a huge difference over the length of the fence.

Since both your extension tables and floating table seem to be off. It is possible the problem is the main table bosses. Again I suspect one boss preventing the fence rail from be perfectly parallel to the table it is mounted on. On the main table check the fence rail against a miter slot they should be 90 degrees.

Im guessing comtaimination or a slight metal burr has caused one or more of the table fence rails to be mounted slightly off.

Check you fence rail washers/spacers to make sure they are all the same thickness.

Remember a very slight variance on the front rail problem less than .005 will give you about 1/16 inch swing on the fence you are seeing. It multiplies over the length of the fence.

Ed in Tampa · Post by **Ed in Tampa** » Sat Jun 23, 2012 5:23 pm

After watching you second video I'm convinced the problem is one or more of the front fence rails is not parallel to the table.

This can be checked by placing the square in one of the grooves and checking the fence rail for 90 degrees.

Since everything seems to be off the same amount except your main table my guess is the main table rail is the culprit.

Problem could be dirty or a burr on one of the bosses, a spacer or washer not the same thickness, bent fence rail (slight indentation where it mounts), badly machined boss or magic

Check the main table fence rail, check the extension table fence rail you should find one or more not parallel to the table face. Then remove the fence rail check the spacers for the same thickness, make sure there is no blemish on the fence rail or machined bosses. Swap around the spacers to see if you can change the results.

I'm convinced the problem is the fence rail to table connection. And my money is on the main table.

Be sure and let us know what you find.

I think once you have this solved you will no longer have that slight catch as you slide the square's rule down the fence rails between tables. That is a major clue.

fjimp · Post by **fjimp** » Sat Jun 23, 2012 5:48 pm

I admit to not having followed the entire thread yet noted two questions occurring in my rather simple mind. First have you checked whether the blade itself is square to the main table? Secondly have you used the shims provided by Shopsmith to check how parallel the front and back extrusions are to the table tops? I assume this has all been verified so will apologize in advance for blubbering. Jim

algale · Post by **algale** » Sat Jun 23, 2012 5:53 pm

Ed in Tampa wrote:After watching you second video I'm convinced the problem is one or more of the front fence rails is not parallel to the table.

This can be checked by placing the square in one of the grooves and checking the fence rail for 90 degrees.

Since everything seems to be off the same amount except your main table my guess is the main table rail is the culprit.

Problem could be dirty or a burr on one of the bosses, a spacer or washer not the same thickness, bent fence rail (slight indentation where it mounts), badly machined boss or magic

Check the main table fence rail, check the extension table fence rail you should find one or more not parallel to the table face. Then remove the fence rail check the spacers for the same thickness, make sure there is no blemish on the fence rail or machined bosses. Swap around the spacers to see if you can change the results.

I'm convinced the problem is the fence rail to table connection. And my money is on the main table.

Be sure and let us know what you find.

I think once you have this solved you will no longer have that slight catch as you slide the square's rule down the fence rails between tables. That is a major clue.

Ed,

Thanks for these suggestions, which I will investigate.

Before I read your message I had likewise reached the conclusion that the problem must be coming from the interface between the main table and either the rear of front fence rail. This is the only thing that would explain why the rip fence can be aligned when on the main table yet be off when the fence is placed on either floating table or the extension table.

I will investigate and report back, hopefully with the summer blockbuster YouTube smash hit video "Table/Fence Alignment 3 -- Revenge of the Squares"!:D

Whether I resolve the problem or not, the time you and JPG and Dusty have invested in trying to solve my table/fence problem is proof positive of what makes this forum a gem.

Al

dusty · Post by **dusty** » Sat Jun 23, 2012 6:01 pm

Ed in Tampa wrote:Put your square on the fence rail and the side of the extension table. It shoud be square however the rail may extend past the side of the extension table making this hard to measure.

Perhaps rather than the side of the table you can check a groove to see if the fence rail is exactly 90 degrees. Check the main table fence rail also.

Another thing you could do is take the fence rails off the extension table and see if the bosses where the fence rail set is parallel with the edge of the extension table or groove in the table.

One last thing take the fence rail off both the main and extension and see if bosses in the main are in the same plane as a extension table bosses.

I suspect one table boss is slightly proud of the other making the fence rail sit sightly out of parallel with the actual table. It doesn't have to be much to cause your fence end to telegraph that slight difference into a huge difference over the length of the fence.

Since both your extension tables and floating table seem to be off. It is possible the problem is the main table bosses. Again I suspect one boss preventing the fence rail from be perfectly parallel to the table it is mounted on. On the main table check the fence rail against a miter slot they should be 90 degrees.

Im guessing comtaimination or a slight metal burr has caused one or more of the table fence rails to be mounted slightly off.

Check you fence rail washers/spacers to make sure they are all the same thickness.

Remember a very slight variance on the front rail problem less than .005 will give you about 1/16 inch swing on the fence you are seeing. It multiplies over the length of the fence.

Very Interesting.

:(

To test that theory:

[ATTACH]17812[/ATTACH]

[ATTACH]17813[/ATTACH]

[ATTACH]17814[/ATTACH]

[ATTACH]17815[/ATTACH]

algale · Post by **algale** » Sat Jun 23, 2012 6:08 pm

fjimp wrote:I admit to not having followed the entire thread yet noted two questions occurring in my rather simple mind. First have you checked whether the blade itself is square to the main table? Secondly have you used the shims provided by Shopsmith to check how parallel the front and back extrusions are to the table tops? I assume this has all been verified so will apologize in advance for blubbering. Jim

Thanks, Jim. In response to your first question, yes the table has been aligned to the blade using a dial indicator in the miter slots referencing off of a tooth (actually a gullet) on a blade.

In response to your second question, I assume by shims you are referring to the aluminum thingy that Shopsmith sends. If so, the answer is yes. In fact, over the last two days I have carefully checked and realigned as necessary the front and rear fences on all the tables. They are now all very well aligned to the table tops and in the same vertical plane. Now the story is different in the horizontal plane where there is a slight catch and that may be enough to be the problem because, as Ed points out above, a very slight horizontal misalignment of the rail will translate to quite large error over the length of the fence.

Al

JPG · Post by **JPG** » Sat Jun 23, 2012 6:42 pm

Been away from this all afternoon and the videos are 'enlightening'.

1) They illustrate the apparently uncontrolable fetish with the table top grooves. Yes from a visual perspective(pun intended) they should be consistent between the main and the other tables, but really are not relevant to the objective of the fence being consistent regardless of which table the fence is attached to.

2) The starrett square edge against each of the main and aux table(I will not distinguish between extension and floating table here as the extension table only differs by the inclusion of the mounting tubes which is an independent alignment adjustment) was informative, but did not illustrate what is relevant here. What 'matters' is the straightness from the left end of the main table rail all the way to the right end of the aux table rail. That 'straightness' will illustrate the parallelism of the two rails to each other.

3) No attention is being paid to the straightness of the connecting tube. None of all this will work if the tubes are not straight. The tubes must be tight against the reference surface(s) on the inside of the rails. The 520 screws force the tubes against the top of the inside of the rails. This differs from the 510 which forced the tubes against the inside front of a pipe(rail). It is crucial that the inner top surface of the 520 rail extrusion also force the tube into a position parallel with the outer front surface of the rail extrusion.

Now for some prognosticating:

What will cause the aux table rails to not align parallel to the main table rails?

There are two sources of possible mis-alignment; The internal rail surface that the tube presses against, and the tube surface itself. Notice I have not mentioned differences in the rail extrusion or mounting hardware and surfaces on the table. The object is to make the rails parallel. Assuming reasonable tolerances on those differences, that should be adequate. Besides those things are constant and not something we can change.

Now since all the aux tables exhibit a similar trait of misalignment to the main table we need to direct our attention to those things which always relate to the main table that can affect the aux table positioning.

Main table rails(inside(tube) and outside(fence)).

I have mentioned the tube straightness, but we must also pay attention to more localized defects(burrs, dents, out of round. . .).

The rails need to be examined for similar defects, but the most likely place is the ends of the rails. Probably the most incidious would be a slight movement of the front of the rail bent inward thus skewing the tube relative to the front. Now although that makes sense, realize the 520 is not dependent upon the front inside surface of the rail, but rather the top. That top surface could get dinged however.

So for current lack of any better places to 'look', the tubes and the top inside of the rails.

Do keep in mind that both the front and rear rails must also be parallel to each other. That makes 8 rails relevant here!

OVER!:)