520 Extension Table/Fence issue

dusty · Post by **dusty** » Sat Jun 23, 2012 7:48 am

algale wrote: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.

This theoretically can not be unless the face of the front rails on the floating and extension tables are not perpendicular to the miter slots. The rip fence orients itself to the front rail to which it is attached.

This orientation can be verified by placing a long straight edge on the front rails to verify they are in the correct plane (all the same plane).

[ATTACH]17809[/ATTACH]

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Sorry for the fuzzy picture. I could not hold the camera steady while holding the level in place.

I've been told that my Stanley Level is not dependable as a straight edge and that I need an expensive straight edge for this task. Be that as it may. Use whatever straight edge you have that you trust and check the rails with respect to the rail on the main table.

If you don't have a straight edge, make like an Egyptian and use a string stretched taunt across the rails.

algale · Post by **algale** » Sat Jun 23, 2012 7:52 am

dusty wrote:[ATTACH]17803[/ATTACH]
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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D'oh (insert sound of palm of hand slapping forehead). Thanks for the photo of the extension table hanging off the machine beyond the base arm. I feel pretty silly now! Anyway, I will give it a go and report back. Thanks for the help.

algale · Post by **algale** » Sat Jun 23, 2012 8:01 am

dusty wrote: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.

Please explain "tweaking." Do you mean that if the ribs of two table do not align perfectly when one table is tight against the other, parallelism can be achieved by opening a slight gap between the table at the front or rear before locking the extension/floating table to the extension tube?

dusty · Post by **dusty** » Sat Jun 23, 2012 8:17 am

algale wrote:Please explain "tweaking." Do you mean that if the ribs of two table do not align perfectly when one table is tight against the other, parallelism can be achieved by opening a slight gap between the table at the front or rear before locking the extension/floating table to the extension tube?

Yes. However, that should really not be necessary. Unless there is some sort of defect, parallelism should be achievable without tweaking. If you are doing segmented turnings or inlays, you may need "precision" but for what is usually done on a table saw I don't think so.

dusty · Post by **dusty** » Sat Jun 23, 2012 8:57 am

I just reread this thread and I need to verify something.

You have reported that all is well with the rip fence mounted on the main table but that when you move the rip fence to either an extension or floating table the rip fence is visually out of alignment (that is, it does not align with the ribs).

Is this a correct interpretation?

I just checked all of my 520 tables by mounting and securing the rip fence. They are all close enough to consider "visually aligned". That is to say, " I would use them as is".

algale · Post by **algale** » Sat Jun 23, 2012 10:53 am

dusty wrote:I just reread this thread and I need to verify something.

You have reported that all is well with the rip fence mounted on the main table but that when you move the rip fence to either an extension or floating table the rip fence is visually out of alignment (that is, it does not align with the ribs).

Is this a correct interpretation?

Exactly!

I have now posted a video on YouTube http://www.youtube.com/watch?v=pcBarKqOjdg&feature=youtube_gdata_playerwhich shows that (1) the fence is aligned to the main table miter slot and main table grooves, (2) the main table grooves are aligned to the floating table grooves. Yet when the rip fence is moved to the floating table, the rip fence is no longer aligned. Yet the rails seems to be aligned pretty well. I really can't figure this out.

beeg · Post by **beeg** » Sat Jun 23, 2012 11:34 am

Seems tome that since the groves on the main table and the extension table are in alignment. That the extension table fence rail needs to be shimmed? OR that the extension table isn't in align front to back since your ruler catches on the front edge.

dusty · Post by **dusty** » Sat Jun 23, 2012 11:39 am

algale wrote:Exactly!

I have now posted a video on YouTube http://www.youtube.com/watch?v=pcBarKqOjdg&feature=youtube_gdata_playerwhich shows that (1) the fence is aligned to the main table miter slot and main table grooves, (2) the main table grooves are aligned to the floating table grooves. Yet when the rip fence is moved to the floating table, the rip fence is no longer aligned. Yet the rails seems to be aligned pretty well. I really can't figure this out.

Okay, this is the way this is suppose to work. I just happen to be in the shop with the website displaying on the computer monitor.

I watched your utube video.

Try this please.

Isolate the carriage and table from the headstock and maintable so that you have clear access to the edges of your tables.

Lock the rip fence down and using your t-square, verify that the rip fence is equal distance from the edge of the main table all the way along.

Now move the the rip fence to either a floating table or a extension table and do the same thing. Theoretical, it will be dead on. Don't pay attention to the ribs at this point. Use the t-square.

If not, the front rail is your problem unless the rip fence moves when you lock it down with the top lever.

PS: I did this, after posting here, with a floating table married to the extension table using extension tubes. This gave me access to the edge of the extension table and the opposite edge of the floating table. I then lock the rip fence across the union between the two fences. Using the combination check that the rip fence is equal distant from the edge of one table and then do the same on the other side of the rip fence (using the other table edge).

With the assumption that the rip fence is dead on when mounted on the main table, this should demonstrate whether the small tables and their rails are proper or not.

You can actually do this without a combination square. Just hold the rip fence firmly against the front rail and slide it back and forth along the rails while watching the ribs with respect to the edge of the rip fence. Your eyes may go crossed but you will be able to see the parallelism or lack there of.

algale · Post by **algale** » Sat Jun 23, 2012 11:41 am

beeg wrote:Seems tome that since the groves on the main table and the extension table are in alignment. That the extension table fence rail needs to be shimmed? OR that the extension table isn't in align front to back since your ruler catches on the front edge.

That possibility has been discussed; although I don't know what problems shimming the fence rail may cause.

dusty · Post by **dusty** » Sat Jun 23, 2012 12:35 pm

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.