520 Extension Table/Fence issue

[algale]

I think i have a problem with the extension table or extension table rails on my 520 but I can't figure it out. I have aligned my main table and rip fence to within a couple of thousandths. Coincidentally or as I suspect by design, this means the fence also runs visually parallel to the machined lines in the table top.

When I move the well aligned rip fence to my extension table, however, the rip fence when locked down is no longer parallel to the machined lines in the top of the extension table and is no longer parallel to the blade. There is about a 3/32nds slant front to back. This stays constant whether I bring the main table up to the extension table and/or connect the extension and main tables with the extension tubes throughout the table rails. I have put a straight edge on the table rails and they do not appear to be bent.

The extension table rails appear to be well aligned to the main table rails as the connector tubes slide easily between them. Even, however, if the extension table was misaligned to the main table, I would expect that when the main table and extension table are disconnected and the rip fence is mounted on the extension table rails, the fence would be at least visually parallel to the engraved lines on the extension table.

If it were merely a cosmetic issue with the fence remaining parallel to the blade when moved to the extension table I wouldn't care that the fence was not parallel to the lines on the table. But the fence isn't parallel to either. What I want is for the fence to remain parallel to the blade when it is moved from the main table to the extension table.

[dusty]

I think i have a problem with the extension table or extension table rails on my 520 but I can't figure it out. I have aligned my main table and rip fence to within a couple of thousandths. Coincidentally or as I suspect by design, this means the fence also runs visually parallel to the machined lines in the table top.

When I move the well aligned rip fence to my extension table, however, the rip fence when locked down is no longer parallel to the machined lines in the top of the extension table and is no longer parallel to the blade. There is about a 3/32nds slant front to back. This stays constant whether I bring the main table up to the extension table and/or connect the extension and main tables with the extension tubes throughout the table rails. I have put a straight edge on the table rails and they do not appear to be bent.

The extension table rails appear to be well aligned to the main table rails as the connector tubes slide easily between them. Even, however, if the extension table was misaligned to the main table, I would expect that when the main table and extension table are disconnected and the rip fence is mounted on the extension table rails, the fence would be at least visually parallel to the engraved lines on the extension table.

If it were merely a cosmetic issue with the fence remaining parallel to the blade when moved to the extension table I wouldn't care that the fence was not parallel to the lines on the table. But the fence isn't parallel to either. What I want is for the fence to remain parallel to the blade when it is moved from the main table to the extension table.

I believe you are proclaiming that the main table miter slots and your rip fence are dead on parallel with the face of the saw blade. I would then conclude that the main table rails are perpendicular to plane of the saw blade. However, you MUST ASCERTAIN that fact because once you involve the extension and floating tables, you are dependent upon that relationship.

Install tubes in the front and rear rails and slide your extension table(s) onto the tubes and flush against the edge(s) of the main table. Secure the rails to the tubes and mount and check your rip fence.

The rip fence should slide smoothly from the main table to the extension table(s). Secure the rip fence to the extension table(s) and check for parallelism with the blade (grooves in the extension table(s). Everything should pass muster at this point.

NOTE: The extension table(s) should not be inserted into Base Arm or the Headrest at this point.

If everything passed muster, remove the extension table from the right side of the main table and install it into the Base Arm. Adjust it to be the same height as the main table and then position the carriage so that the right side of the main table and the left side of the extension table are flush. The tubes should slide smoothly through the front and rear rails. The groves in the tables should be parallel. The rip fence should slide smoothly back and forth from main table to extension table.

If not, loosen all four sets of nuts on the extension table. Secure the extension table to the tubes. Tighten the nuts on the extension table (finger tight) and recheck alignment.

It should pass muster and you should be pleased. If not, I am confused.

[algale]

I believe you are proclaiming that the main table miter slots and your rip fence are dead on parallel with the face of the saw blade. I would then conclude that the main table rails are perpendicular to plane of the saw blade. However, you MUST ASCERTAIN that fact because once you involve the extension and floating tables, you are dependent upon that relationship.

Install tubes in the front and rear rails and slide your extension table(s) onto the tubes and flush against the edge(s) of the main table. Secure the rails to the tubes and mount and check your rip fence.

The rip fence should slide smoothly from the main table to the extension table(s). Secure the rip fence to the extension table(s) and check for parallelism with the blade (grooves in the extension table(s). Everything should pass muster at this point.

NOTE: The extension table(s) should not be inserted into Base Arm or the Headrest at this point.

If everything passed muster, remove the extension table from the right side of the main table and install it into the Base Arm. Adjust it to be the same height as the main table and then position the carriage so that the right side of the main table and the left side of the extension table are flush. The tubes should slide smoothly through the front and rear rails. The groves in the tables should be parallel. The rip fence should slide smoothly back and forth from main table to extension table.

If not, loosen all four sets of nuts on the extension table. Secure the extension table to the tubes. Tighten the nuts on the extension table (finger tight) and recheck alignment.

It should pass muster and you should be pleased. If not, I am confused.

I rechecked and the main table miter slots are parallel to the blade. Given this is the case, like you i would have thought the fence rails on the main table of a 520 could not be anything other than perpendicular to the miter slots/blade. I always assumed the table edge casting and fence spacers automatically assured this. While the level and levelness of the fence rail can be adjusted relative to the top edge of the table, and Shopsmith provides an aluminum gauge block to make this adjustment, I am unaware of any adjustment to bring the rail in or out from the table edge on a 520 and thus to adjust whether it is perpendicular to the miter slots, although I suppose shims could always be added.

Having said that, I think you are on to something. I couldn't figure out how to mount the extension table without it being in the base arm because the support legs interfere with the way tubes. So, I did the next best thing: I mounted first one and then the other floating table. What I discovered is that when I mount a floating table, if I bring the edge of the floating tabke right up against the bosses on the edge of the main table, the rear bosses touch first. If I force the front bosses together, then the front fence rail on the floating table will not be totally parallel to the front fence rail of the main table, causing the rip fence to go out of parallel to the miter slot when placed on the floating table. If I let the rear bosses touch and then tighten the extension tubes without the front bosses touching, the floating table seems to align, the front fence rails are parallel and the the fence when placed on the floating table appears to be parallel to the miter slot again.

Now, this may a related problem to the one I originally described or a separate one. With the extension table mounted in the base arm, I am at a loss as to what could cause the rip fence to be so noticeably out of alignment to the grooves on the extension table when the fence is placed on the extension table only. I admit that the extension table may need to be adjusted to get the fence parallel to the blade/miter slots, but no matter how the extension table may be sitting on it's dog bone, the fence rails should still be parallel to the extension table edge and hence perpendicular to the grooves on the extension table and a fence mounted on these rails ought to be parallel to those grooves.

[JPG]

I think you need to remove two observations from any alignment procedure.

1) The relative positions of the side 'bosses' on the tables.

2) The orientation of the table top grooves to the fence.

Both of those cause you to assume their relative orientation to the rails.

Do as Dusty has suggested by attaching the ext table by way of the tubes(they are straight are they not?). Again ignoring the table edges and the grooves, check the fence to the main table/blade/miter bar slot while the fence is mounted on the ext table. If the fence does not check out to be correct, here and now is when to determine why it is not!

Then mount the ext table in the base with the table loose on its support and align the ext table(with the fence still attached) to the main table etc. At the same time make any vertical alignment tweaks as needed.

This should result in the fence being consistent with the main table and hopefully the main and Ext table rails will provide a smooth accurate transition as the fence is slid between them.

Accept the table sides and top grooves as they are!;)

The tubes should not be under any stress from the rails at any time other than gravity.

I am not convinced the table side bosses are a reliable reference surface for this procedure. I agree the grooves should be perpendicular to the rails.

In a perfect world all the floating tables and extension tables are consistent with their rails. FWIW, my world is not 'perfect' so we have to accept what is tolerable.

[algale]

Again ignoring the table edges and the grooves, check the fence to the main table/blade/miter bar slot while the fence is mounted on the ext table. If the fence does not check out to be correct, here and now is when to determine why it is not!

I have done that and the fence, which is parallel to the miter slots when it is on the main table alone, is way off when mounted on either floating table or extension table if the floating table/extension table is brought up flush to the main table. I am trying to determine here and now why this is. As yet, I can't figure it out.

I also need to correct something I previously said: only the main table has side bosses. Neither the floating table or extension table has bosses. So, as I was trying to figure out why the fence wasn't parallel to the miter slots I discovered that when the floating table is flush against the two bosses of the main table, the front rails are slightly out of parallel. When the floating table touches only the rear boss of the main table, the front rails are parallel and the fence is aligned parallel to the miter slots.

I will check the table tubes again. Last time I checked them they were as straight as Shopsmith makes em, per Nick's Sawdust session, which isn't perfectly straight but not bananas either. I had previously marked the high spots on the tubes and orient them up, as Nick showed in his sawdust session on alignment.

I will also realign the extension table since it can be turned onits dog bone and hopefully brought into alignment t with the main table. However, this won't resolve the issue with the floating tables.

[JPG]

I have done that and the fence, which is parallel to the miter slots when it is on the main table alone, is way off when mounted on either floating table or extension table if the floating table/extension table is brought up flush to the main table. I am trying to determine here and now why this is. As yet, I can't figure it out.

I also need to correct something I previously said: only the main table has side bosses. Neither the floating table or extension table has bosses. So, as I was trying to figure out why the fence wasn't parallel to the miter slots I discovered that when the floating table is flush against the two bosses of the main table, the front rails are slightly out of parallel. When the floating table touches only the rear boss of the main table, the front rails are parallel and the fence is aligned parallel to the miter slots.

I will check the table tubes again. Last time I checked them they were as straight as Shopsmith makes em, per Nick's Sawdust session, which isn't perfectly straight but not bananas either. I had previously marked the high spots on the tubes and orient them up, as Nick showed in his sawdust session on alignment.

I will also realign the extension table since it can be turned onits dog bone and hopefully brought into alignment t with the main table. However, this won't resolve the issue with the floating tables.

Again: Ignore the table sides and table top grooves. The rail alignment(by way of the tubes) is all that matters. If the rails do not provide consistency to the main table, then ya just cannot get there!



P.S. Shimming the rails to the table will create a whole new realm of frustration. I would not go there unless a minimal tweak will correct things.


P.P.S.
It is not clear to me if the floating tables are inconsistent re rail alignment, or the 'side' issue is the concern. Again: Ignore the sides and grooves.

[algale]

Again: Ignore the table sides and table top grooves. The rail alignment(by way of the tubes) is all that matters. If the rails do not provide consistency to the main table, then ya just cannot get there!



P.S. Shimming the rails to the table will create a whole new realm of frustration. I would not go there unless a minimal tweak will correct things.


P.P.S.
It is not clear to me if the floating tables are inconsistent re rail alignment, or the 'side' issue is the concern. Again: Ignore the sides and grooves.

Took me a while to understand what you were saying but I get it now: if all the rails line up via the extension tubes, then a fence that is parallel when on the main table will have to be parallel when on the floating tables and extension tables.

I agree there is not always a need for the tables to touch each other to be used for ripping and I have frequently used the tables with gaps between them. But from time to time in order to make a particular rip cut of the required width, I have had to but the tables up against each other and have the fence fully on the floating/extension table rail or even straddle the rails on two adjoining tables.

It would therefore be nice if the fence would align with the tables apart or together. I have to believe this is possible and would like to figure out why I am currently unable to do so.

[dusty]

Took me a while to understand what you were saying but I get it now: if all the rails line up via the extension tubes, then a fence that is parallel when on the main table will have to be parallel when on the floating tables and extension tables.

I agree there is not always a need for the tables to touch each other to be used for ripping and I have frequently used the tables with gaps between them. But from time to time in order to make a particular rip cut of the required width, I have had to but the tables up against each other and have the fence fully on the floating/extension table rail or even straddle the rails on two adjoining tables.

It would therefore be nice if the fence would align with the tables apart or together. I have to believe this is possible and would like to figure out why I am currently unable to do so.

It is possible. I rip with the fence on a floating table frequently. I double check for parallelism because of the propensity to be out but it is easily achieved.

I doubt the need for shims.

Make certain that your extension tubes are straight. I cut a set of 5' tubes into shorter sections because they were so bad.

I rely on the bosses because they are milled surfaces. These are the reference points used by the milling machines when the tables are being manufactured.

I have also come to trust the ribs in the table top. I don't align to them but they are reliable for eye ball reference.

Note: I speak here only with regard to the newer tables. I don't have any that are in the 40-50 year old range. Some techniques have changed in the last few years.

[dusty]

I rechecked and the main table miter slots are parallel to the blade. Given this is the case, like you i would have thought the fence rails on the main table of a 520 could not be anything other than perpendicular to the miter slots/blade. I always assumed the table edge casting and fence spacers automatically assured this. While the level and levelness of the fence rail can be adjusted relative to the top edge of the table, and Shopsmith provides an aluminum gauge block to make this adjustment, I am unaware of any adjustment to bring the rail in or out from the table edge on a 520 and thus to adjust whether it is perpendicular to the miter slots, although I suppose shims could always be added.

Having said that, I think you are on to something. I couldn't figure out how to mount the extension table without it being in the base arm because the support legs interfere with the way tubes. So, I did the next best thing: I mounted first one and then the other floating table. What I discovered is that when I mount a floating table, if I bring the edge of the floating tabke right up against the bosses on the edge of the main table, the rear bosses touch first. If I force the front bosses together, then the front fence rail on the floating table will not be totally parallel to the front fence rail of the main table, causing the rip fence to go out of parallel to the miter slot when placed on the floating table. If I let the rear bosses touch and then tighten the extension tubes without the front bosses touching, the floating table seems to align, the front fence rails are parallel and the the fence when placed on the floating table appears to be parallel to the miter slot again.

Now, this may a related problem to the one I originally described or a separate one. With the extension table mounted in the base arm, I am at a loss as to what could cause the rip fence to be so noticeably out of alignment to the grooves on the extension table when the fence is placed on the extension table only. I admit that the extension table may need to be adjusted to get the fence parallel to the blade/miter slots, but no matter how the extension table may be sitting on it's dog bone, the fence rails should still be parallel to the extension table edge and hence perpendicular to the grooves on the extension table and a fence mounted on these rails ought to be parallel to those grooves.

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The tables are NOT quite touching. I tweaked them to emphasize alignment of the ribs in the next two images.

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You just have to trust that the aluminum block is square.

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[dusty]

I rechecked and the main table miter slots are parallel to the blade. Given this is the case, like you i would have thought the fence rails on the main table of a 520 could not be anything other than perpendicular to the miter slots/blade. I always assumed the table edge casting and fence spacers automatically assured this. While the level and levelness of the fence rail can be adjusted relative to the top edge of the table, and Shopsmith provides an aluminum gauge block to make this adjustment, I am unaware of any adjustment to bring the rail in or out from the table edge on a 520 and thus to adjust whether it is perpendicular to the miter slots, although I suppose shims could always be added.

Having said that, I think you are on to something. I couldn't figure out how to mount the extension table without it being in the base arm because the support legs interfere with the way tubes. So, I did the next best thing: I mounted first one and then the other floating table. What I discovered is that when I mount a floating table, if I bring the edge of the floating tabke right up against the bosses on the edge of the main table, the rear bosses touch first. If I force the front bosses together, then the front fence rail on the floating table will not be totally parallel to the front fence rail of the main table, causing the rip fence to go out of parallel to the miter slot when placed on the floating table. If I let the rear bosses touch and then tighten the extension tubes without the front bosses touching, the floating table seems to align, the front fence rails are parallel and the the fence when placed on the floating table appears to be parallel to the miter slot again.

Now, this may a related problem to the one I originally described or a separate one. With the extension table mounted in the base arm, I am at a loss as to what could cause the rip fence to be so noticeably out of alignment to the grooves on the extension table when the fence is placed on the extension table only. I admit that the extension table may need to be adjusted to get the fence parallel to the blade/miter slots, but no matter how the extension table may be sitting on it's dog bone, the fence rails should still be parallel to the extension table edge and hence perpendicular to the grooves on the extension table and a fence mounted on these rails ought to be parallel to those grooves.

With the floating table tight against the main table, the ribs are parallel to within 1/32". If you need it dead on parallel, that can be done by tweaking before you lock the floating table to the extension tubes.

I rip fence mounted on this floating table should be equally square with the floating table as it is with the main table.

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