520 Extension Table/Fence issue

dusty · Post by **dusty** » Mon Jun 25, 2012 7:59 am

Okay, set me straight.

Is the problem with the Main Table resolved?

The front and rear rails are parallel to one another; and the miter slots are perpendicular to the front and rear rails; the table (miter slot) is parallel to the blade; and the bosses are 22" apart; and the rip fence has been properly adjusted to be parallel to the blade?

If the answer is yes, then you are about ready to make the rest of your table system ready to make saw dust.

Are all of the extension tubes are relatively straight?

Are all of the bosses smooth and do they measure 22"?

pennview · Post by **pennview** » Mon Jun 25, 2012 8:20 am

As a workaround for ripping, you could build an auxiliary fence somewhat like this one -- http://www.shopsmith.net/forums/showpos ... ostcount=6

If you make it wide enough, you'll be able to rip wood by mounting the fence on either the main table or the auxiliary table. For those in between rips that currently would require you to have the fence straddle the main and auxiliary/floating tables, you could attach the fence to the auxiliary table and clamp or bolt the auxiliary fence to it.

Simply measure the width of the widest board you can rip with the fence mounted on the main table, then measure for the narrowest board you can rip with the fence mounted on the auxiliary table, and make a fence a bit wider than the difference between those two measurements.

If you need a floating table between the main and auxiliary tables, simply attach it to one or the other, but not both.

While it doesn't fix your alignment issue, it will allow you to rip wood accurately and safely.

JPG · Post by **JPG** » Mon Jun 25, 2012 8:26 am

Translation: Boss pairs parallel(front to rear) and perpendicular to the slot and finally spaced correctly(22").

All shimming should be done to achieve those three goals(paying attention to anything else will be a distraction).

I think a sequence would be to determine perpendicularity first(if both front & rear bosses are perpendicular, then they are also parallel). Lastly shim to achieve 22".

I would suggest using aluminum beverage cans for shim stock. The cans are typically 0.003" thick.

Notice the attention is directed to the bosses, not the rails.

One other pesky detail: First glance suggests the rail to table 'front' need be the same for all tables, however it is the 22" spacing that will affect rail alignment. After all the floating tables are reversible front - rear(on a 510 anyway - I assume the 520 rails are the same f-r).

dusty · Post by **dusty** » Mon Jun 25, 2012 9:31 am

I would check the bosses in pairs to make certain that they are 22" apart and then mount the rails. Reason: Unless they have been modified by a PO, they are 22" apart.

Then I would then mount the rails and verify the separation of extreme front and back surfaces to be 25". If they measure 25" at both ends, I would then assume them to be parallel. If they do not measure 25", shimming may be necessary.

I would then do a standard table to blade alignment followed by a rip fence alignment and call the main table done.

NOTE: In Al's case, all the spacers need to be verified; spacers should be .314" +- .001". My specification NOT Shopsmith's. Al knows that at least one of his spacers (518403, Table Spacer(146), $0.80) is thinner.

The 510 and 520 tables are interchangeable and measurements are the same but be aware that there are at least three different vintages.

algale · Post by **algale** » Mon Jun 25, 2012 1:03 pm

Good Morning:

I can answer some questions and post some interesting video.

SPACERS

Yesterday I removed the front rail of the main table and measured the spacers with a micrometer. The left and right spacers were .314. The MIDDLE spacer was only .307, so I shimmed it and reattached. Seemed to make a negligible difference.

Last night I removed the main table rear rail and mic'd the spacers and they were all the reading the same .314. So the main table spacers are good.

This morning I removed the front and rear rails of the 2 floating tables and mic'd the spacers. All .314. No significant issue there.

I also pulled the rails off of the extension table and mic'd those. Interestingly, each rail had one washer measuring .314 washer and one measuring .310 washer. I decided to put both of the narrower washers on the rear rail and both the .314 washers on the front so if I go back and shim the extension table, I only need pull of one rail I set the extension table aside for purposes of figuring out my problem. If I can fix the problem on the floating tables I'll go back and shim the extension table.

Bosses

Getting really accurate measurements on the bosses is difficult, particularly on the main table because each of the front bosses has a rough little shelf on the bottom. The distance between the front and bosses of the main table (not including the little shelves) appears to be exactly 22 inches. Adding the little shelf increases the width by a little more than 1/32 and a little less than 1/16th. While I think this might be enough to cause the problem, I no longer believe the shelves on the front bosses are interfering with the spacers sitting flush against the smooth part of the bosses, although it is VERY close. Perhaps I would be better off removing this shelf just to be sure. And I invite suggestions on how to do this without messing up the rest of the boss.

The two floating tables and extension table appear to measure 22 inches between the bosses. Incidentally my floating table and extension table bosses look like the left hand example on Dusty's drawing: http://www.shopsmith.net/forums/showpos ... stcount=57

Everything Is Parallel and Perpendicular (Until the Fence Is On Floating Table)

Checked blade to main table miter slot alignment with a dial indicator. Good to within 0.003. Checked fence alignment to slot. Good to within 0.002 while on the main table.

When I put the fence on the floating table, I still lose alignment by about a 1/16th of an inch.

I thought I had figured out what I thought was a pretty good way to demonstrate that the main table rails are parallel to each other and perpendicular to the miter slots and that the main table groove are very close to parallel to the main table grooves. Here's a video. http://www.youtube.com/watch?v=sIMd3_ha ... ture=g-upl

The next video demonstrates that the fence is perpendicular to the fence rails and that the extension tubes are also parallel to the fences. http://www.youtube.com/watch?v=yHinlXHW ... ture=g-upl

I mounted a floating table. The rails were parallel to the main table rails as shown in this video. http://www.youtube.com/watch?v=sXGjyAMD ... ture=g-upl

Finally I mounted the rip fence on the floating table. This appeared to show the fence was perpendicular to the rails (although still not visibly parallel to the grooves on the table. http://www.youtube.com/watch?v=eaGqHyRU ... ture=g-upl

I didn't take a video but this made me put the table back down, raise the blade and take some measurements of fence to front of blade and fence to rear of blade. With the fence on the main table, the distance from the fence to the front and rear of the blade are exactly even (I guess my square isn't graduated in thousandths because I know it is open .002 in the rear). Moving the fence to the extension table, the fence to blade measurements disagree by 1/16th of an inch (with the fence being 1/16th inch more open to the rear.

For a minute, I really thought I was getting somewhere but nope.

As I said, while I don't think the little shelves on the front bosses of the main table are the culprit (since the shelves don't appear to interfere with the spacers sitting against the smooth part of the boss) I am open to filing them off to eliminate them completely as potential source of error.

Al

algale · Post by **algale** » Mon Jun 25, 2012 1:16 pm

dusty wrote:Okay, set me straight.

Is the problem with the Main Table resolved?

Yes

dusty wrote:The front and rear rails are parallel to one another]

Yes.

dusty wrote:If the answer is yes, then you are about ready to make the rest of your table system ready to make saw dust.

Are all of the extension tubes are relatively straight?
No, just like Nick showed they have an arch but the arch is up and there doesn't appear to sideways deflection. I am considering getting some 1" EMT from Lowe's however to see if it is the tubes. Keep in mind however that the same error appeared on the extension table regardless of whether it was connected via the tubes to the main table and floating off the end of the Shopsmith or disconnected from the main table and tubes and just sitting by itself in the base arm.

dusty wrote:Are all of the bosses smooth and do they measure 22"?

They are not all smooth but the little shelf on the front rails isn't to my eye interfering with the seating of the spacer on the smooth part of the boss. All measurements to the smooth parts of the bosses appear to be 22 inches.

algale · Post by **algale** » Mon Jun 25, 2012 1:17 pm

pennview wrote:As a workaround for ripping, you could build an auxiliary fence somewhat like this one -- http://www.shopsmith.net/forums/showpos ... ostcount=6

If you make it wide enough, you'll be able to rip wood by mounting the fence on either the main table or the auxiliary table. For those in between rips that currently would require you to have the fence straddle the main and auxiliary/floating tables, you could attach the fence to the auxiliary table and clamp or bolt the auxiliary fence to it.

Simply measure the width of the widest board you can rip with the fence mounted on the main table, then measure for the narrowest board you can rip with the fence mounted on the auxiliary table, and make a fence a bit wider than the difference between those two measurements.

If you need a floating table between the main and auxiliary tables, simply attach it to one or the other, but not both.

While it doesn't fix your alignment issue, it will allow you to rip wood accurately and safely.

Thanks Art. If I can't resolve this I will build a jig like that.

algale · Post by **algale** » Mon Jun 25, 2012 1:20 pm

JPG40504 wrote:Translation: Boss pairs parallel(front to rear) and perpendicular to the slot and finally spaced correctly(22").

All shimming should be done to achieve those three goals(paying attention to anything else will be a distraction).

I think a sequence would be to determine perpendicularity first(if both front & rear bosses are perpendicular, then they are also parallel). Lastly shim to achieve 22".

I would suggest using aluminum beverage cans for shim stock. The cans are typically 0.003" thick.

Notice the attention is directed to the bosses, not the rails.

One other pesky detail: First glance suggests the rail to table 'front' need be the same for all tables, however it is the 22" spacing that will affect rail alignment. After all the floating tables are reversible front - rear(on a 510 anyway - I assume the 520 rails are the same f-r).

Answers to your questions are in the above messages so I won't repeat them all here. Thanks for the tip on making shims from a soda can.

Ed in Tampa · Post by **Ed in Tampa** » Mon Jun 25, 2012 1:23 pm

In my career as a trouble shooter for IBM I have seen bugs like this go missed for days because an ASSUMPTION was made. Don't assume anything prove each step in a logical Methodical manner and you have to solve the problem. The problem again has to be something is changing the relationship of the fence and fence rail as they relate to the table.

First let us prove we still have a problem. Since nothings says a properly working fence has to be parallel to ext table grooves let us make sure the fence is or is not in perfect alignment with the blade when on an extension table.
Do this is order and don't assume anything do it and see.

First using only the front lock down handle on the fence insure you fence is perfectly (as close as you can make it) parallel to the main table miter slot.

Second using connecting tubes mount one of the floating aux table and only tighten down the front fence rail to the connector tube. Still use the rear connector tube but don't lock down the rear fence rail to it. So nothing is pulled out of alignment.

Third using only the front lock handle lock down fence on the front aux table fence rail and check if the fence is parallel or not with the main table miter slot. If it is then tighten the rear fence rail to the connector tube locks. Is it still parallel? If not then the problem is something is canting the table when you tighten down the rear. My guess the bench and way tubes are off.

If the fence remains parallel then use the rear Fence lock if it moves the fence then problem could be table and tubes are not properly the right size force the fence to deflect or something.

If in the third step the fence isn't parallel and if it is still out of parallel about the same amount on all three ext tables it suggests the problem in with the main table.
And we have missed something there.

Double check the main table fence rail is perfectly perpendicular with the miter slot. Check both miter slots. Once that is done. Get out the SS maintaince manual on main table adjustment and go through each adjustment to insure the table is correct. DON'T Assume on any step either do it or check it to make certain.

Once that is done and using only finger pressure or the front lock make sure the fence is parallel to the miter slot. Using only finger pressure or the front lock eliminates all possiblities with table width or fence problems.

Now mount a aux table and check again. If the fence is off then the problem almost has to be connector tubes are bent or the ext/aux table fence rails have been deformed.

dusty · Post by **dusty** » Mon Jun 25, 2012 2:04 pm

I doubt that any of us have perfectly straight connector tubes.

I also believe that the connector tubes have to be really bad to create an alignment problem as significant as Al's. However, bent tubes are real easy to find. Just roll them on a flat surface like a kitchen counter top or the solid oak dining room table.