Extension tables

JPG · Post by **JPG** » Tue Aug 25, 2009 3:03 pm

dusty wrote:I have been silent in this discussion because I do not undertsand how wall thickness makes a difference. Keakap and I have worked this issue offline and we were unsuccessful obviously.

The location of the inner wall with respect to the edge of the table (machined platforms) or the diameter of the rails is not critical to table alignment. The rails simply need to be aligned so as to be in line with one another (outer edge). This can be done by shimming the rails when they are installed. Tedious, yes - impossible, no.

Will you be able to secure the tables in position on the rail? That may be another story.

WHY does it make a difference?

O.D. they ARE the same on both 'variations'. Combined with the spacer dimensions, BOTH versions have the SAME over all dimension(outside wall to outside wall[front to rear]). This therefore does NOT affect the operation of the fence.

I. D. This is where the rub exists. If you have ALL the same size rail tubes(I.D.) there is also NO problem. Only when you try to use tables of both sizes(I.D.) with each other does it matter.

Consider what happens at the 'joint' of two different sized(I.D.) rails. If you tighten the extension tubes at the front of both, there will a slight offset of the OUTER surface of the table tubes. As Keakap has already pointed out this seems small, but IS easily seen. If you attempt to slide the fence across the 'joint', the fence will tend to hang on the rail extending past the adjoining table rail at both the front and the back of the front rails(the 'thick' rail will stick out in the front, and the 'thinner' rail will stick out in the back.. This is because the extension tube(pushed tight against the inside front of the table tube) will cause the outer front surface of the table older/thicker) rail to extend 1/64" beyond the same surface on the newer/thinner table rail. A similar but opposite condition is caused at the rear of the front tubes. The thinner table tube will stick out since to O.D.s ARE the same. This assumes the extension tube IS straight etc.

After also tightening an extension tube to the back table rails, a similar situation will occur, but the non-alignment will be twice as great. There is going to some flexing of the extension tube as it attempts(unsuccessfully) to align the two table rails(both front and back)[tightening the rear tubes will cause deflection of the front extension tube also]. This flexing will likely occur between the end of the newer/thinner table rail and the screw clamp.

If the deflection of the two extension tubes is the same at the front and the rear, the tables will be aligned correctly(assuming they would be with same sized table rails). The 'problem' then is the step on the outer surface of the table tubes making fence sliding and fence alignment across the 'joint' between adjacent table tubes difficult/unreliable(the fence WILL be cocked).

So far we have only considered the effect of ONE pair of table tube sets. Moving across the table(S) we have additional opportunities to repeat the mis-alignment.

Is all this a REAL problem?; 1) not if you have only one kind(size) of table tubes. 2)IMHO yes! if you DO have table rails of differing I.D. with the same O.D. and spacers.

How severe? The fence sliding across the 'joint' is a relatively minor aggravation(you gotta loosen the clamp more and 'jiggle' it across the joint.

The cocking of the fence when bridging the 'joint' is severe enough to cause accuracy problems. Knowing this it can be avoided by NOT bridging the 'joint' with the fence.

SO! Real problems can be avoided by selectively positioning the 'joint' relative(away from) where you want to set the fence.

This leaves us with the aggravation of a non-smooth sliding of the fence across the 'joint'.

Is all this discussion necessary? I think so for those who DO have both old/thick and new/thinner table rails. It makes us aware of the 'problems' so that we can avoid the 'gotcha's' that go with it. For those fortunate to NOT have a variety pack(for whatever reason(s)); They couldn't care less since they do not have the 'problem'.

dusty · Post by **dusty** » Tue Aug 25, 2009 3:50 pm

JPG40504 wrote:WHY does it make a difference?

O.D. they ARE the same on both 'variations'. Combined with the spacer dimensions, BOTH versions have the SAME over all dimension(outside wall to outside wall[front to rear]). This therefore does NOT affect the operation of the fence.

I. D. This is where the rub exists. If you have ALL the same size rail tubes(I.D.) there is also NO problem. Only when you try to use tables of both sizes(I.D.) with each other does it matter.

Consider what happens at the 'joint' of two different sized(I.D.) rails. If you tighten the extension tubes at the front of both, there will a slight offset of the OUTER surface of the table tubes.

........

Can this offset not be compensated for by shimming the standoffs where they fit against the machined pads on the mating table. That is, move the entire rail out away from the table by an amount equal to the offending offset.

If this is done to every offending rail, the outer edge (circumference) of every rail would be inline with one another.

Drawings or photos would sure help!

PS: An attempt at drawings.

[ATTACH]5756[/ATTACH]

This drawing is intended to depict the relationship of two rail sections (abbreviated length). The two segments have ODs of 1 1/4" while the IDs are 7/64" and 6/64". My extensions tubes are a nominal 1" OD with a wall thickness of .065". The gap between the extension tube and the inside walls of the two table rails would be 1/32" on one and 1/64" one the other. The extension tube, when locked into the rails would be forced outward to the point where the outer surface would be forced against the inner surface of the rail with the smaller ID. This would leave a gap of 1/64" between the extension tube and the inside surface of the other table rail (the one with the larger ID).

What problem(s) does this create?

JPG · Post by **JPG** » Tue Aug 25, 2009 4:16 pm

dusty wrote:Can this offset not be compensated for by shimming the standoffs where they fit against the machined pads on the mating table. That is, move the entire rail out away from the table by an amount equal to the offending offset.

If this is done to every offending rail, the outer edge (circumference) of every rail would be inline with one another.

Drawings or photos would sure help!

The two 'varieties' should have the same dimension over all(assuming the table 'depth' and the spacer 'length' and tube o.d. are the same. They would vary only by manufacturing tolerances which IMHO should be far less than 1/64". I am assuming that your attempts were to shim the spacers so that all the table rails have their outer surfaces aligned.(with 510 hardware) This alignment of the OUTER surfaces of the table rails IS desirable regardless of whatever tube variations one might have.

That WILL work if all the table rails ARE the same wall thickness.(their manufacturing tolerances should be very small).

Therefore the only thing different between the two varieties is the location of the inside wall. The thicker table rails will have their 'reference' wall 1/64" closer to the table(the reference wall is that portion which the extension tubes contact when tightened into place). This reference wall is what aligns the tables to each other. This is why 'bent' tubes are a problem.

I had first thought shims were the 'answer', but I overlooked the resultant expansion of the outer (front to rear) dimension which would affect the positioning on the curved 'pad' on the fence(sets on top of the rear rail) and the clamping(rear) tension adjustment.

Since the ONLY difference IS the location of the 'reference' wall it needs to be brought into line with the other variety. Shimming the inside of the 'thinner walled' table rails seems the only logical/practical(?) choice.

dusty · Post by **dusty** » Tue Aug 25, 2009 5:48 pm

dusty wrote:Can this offset not be compensated for by shimming the standoffs where they fit against the machined pads on the mating table. That is, move the entire rail out away from the table by an amount equal to the offending offset.

If this is done to every offending rail, the outer edge (circumference) of every rail would be inline with one another.

Drawings or photos would sure help!

PS: An attempt at drawings.

[ATTACH]5756[/ATTACH]

This drawing is intended to depict the relationship of two rail sections (abbreviated length). The two segments have ODs of 1 1/4" while the IDs are 7/64" and 6/64". My extensions tubes are a nominal 1" OD with a wall thickness of .065". The gap between the extension tube and the inside walls of the two table rails would be 1/32" on one and 1/64" one the other. The extension tube, when locked into the rails would be forced outward to the point where the outer surface would be forced against the inner surface of the rail with the smaller ID. This would leave a gap of 1/64" between the extension tube and the inside surface of the other table rail (the one with the larger ID).

What problem(s) does this create?

Another attempt at expressing the situation as I see it.

[ATTACH]5757[/ATTACH]

reible · Post by **reible** » Wed Aug 26, 2009 2:35 am

This has been an interesting post. When ever you get used gear you really have no idea how it has been modified. I got a used 510R a few years back, One of the first things I did was take the bolts out of the extension table and change to studs. I also have 500 extension tables with studs, so if I sold these it was updates I did, not necessary changes shopsmith made.

When I went to upgrade my 510 to a 520 I had no idea when the upgrade of the 500 to 510 happened so to be safe I called about the 85 or 86 and up version. In my case I had an upgrade done in 86 or up. An upgrade that I think was well worth it especially if it is on sale.

The 85 version I have never seen but if the necessary holes and locations match with the newer version couldn't one simple drill out the threaded holes in the floating and extension tables and go to a 86 version set of rails with nuts??? I've still got mine set somewhere and I bet a lot of others do to so you might be able to locate a set to try........

Anyway just a thought, now I got to go.

Ed

JPG · Post by **JPG** » Wed Aug 26, 2009 11:21 am

dusty wrote:Can this offset not be compensated for by shimming the standoffs where they fit against the machined pads on the mating table. That is, move the entire rail out away from the table by an amount equal to the offending offset.

If this is done to every offending rail, the outer edge (circumference) of every rail would be inline with one another.

Drawings or photos would sure help!

PS: An attempt at drawings.

[ATTACH]5756[/ATTACH]

This drawing is intended to depict the relationship of two rail sections (abbreviated length). The two segments have ODs of 1 1/4" while the IDs are 7/64" and 6/64". My extensions tubes are a nominal 1" OD with a wall thickness of .065". The gap between the extension tube and the inside walls of the two table rails would be 1/32" on one and 1/64" one the other. The extension tube, when locked into the rails would be forced outward to the point where the outer surface would be forced against the inner surface of the rail with the smaller ID. This would leave a gap of 1/64" between the extension tube and the inside surface of the other table rail (the one with the larger ID).

What problem(s) does this create?

When the OUTSIDE surface of the table tubes(rails) ARE aligned, there is NO problem. However they do not stay aligned when the extension tubes are inserted and tightened. They will stay aligned only if the thinner table tube is compensated for. If the 1/64" to 1/32" misalignment does NOT affect your work, then there is NO problem. If it 'gets in the way' of 'getting the job done' then there IS a problem.(aggravation of difficulty of sliding fence across the 'joint' and the 'cocked fence')

I think Keakap has the experience of trying to 'put up with' this due to the circumstances relative to his table replacement. Wonder what he did with the old table rails. Longer screws and nuts would allow putting the older(thicker) table rails on his 'new' table.

P.S. I just reread(more carefully) Ed's post#44. He makes a very good suggestion. By 'updating' the older hardware to the 'current' version, future potential problems are eliminated. As he inferred, there are probably a lot of 'newer' 510 rails out there with the folks who upgraded to 520 from 510.

Will you folks please stand up and be recognized so that us with 'older' version 510 tubes can PM you re possible negotiations. TIA

dusty · Post by **dusty** » Wed Aug 26, 2009 12:16 pm

[quote="JPG40504"]

P.S. I just reread(more carefully) Ed's post#44. He makes a very good suggestion. By 'updating' the older hardware to the 'current' version, future potential problems are eliminated. As he inferred, there are probably a lot of 'newer' 510 rails out there with the folks who upgraded to 520 from 510.

/quote]

I have reread Ed's post too and I I don't believe he is commenting on the "rail problem" at all. He (Ed) makes mention of the studs for the extension tables being changed (to bolts) but I don't see any inference to the rails.

Incidently - it sure is good to have Ed back into these discussions.

keakap · Post by **keakap** » Wed Aug 26, 2009 2:46 pm

Excellent description. If I didn't know better I'd think you were watching over my shoulder.
I would add only a couply 'minor' points:
>fence sliding-- it became almost an unconscious (dangerous) thing to "jiggle" it across;
> it's amazing how often the fence position comes to be in the worst place;
> "accuracy" is the biggest problem (along with burning) UNTIL the first time you move the fence and don't notice it's cocked, then go ahead and rip-- Watch Out!;
>I agree with your conclusions.

[quote="JPG40504"]WHY does it make a difference?
Is all this a REAL problem?]

keakap · Post by **keakap** » Wed Aug 26, 2009 2:51 pm

dusty wrote:The rails simply need to be aligned so as to be in line with one another (outer edge). This can be done by shimming the rails when they are installed. Tedious, yes - impossible, no.
.

Actually, in this peculiar case, shimming to the table is impossible as a fix. We got close, Dusty, but your collection of odds n ends didn't quite agree with my mixed bag.

But I thank you and everybody for the help. I now know enough to proceed, with Linda's help as well.

keakap · Post by **keakap** » Wed Aug 26, 2009 2:58 pm

JPG40504 wrote:T. Shimming the inside of the 'thinner walled' table rails seems the only logical/practical(?) choice.

Or wrapping that part of the extension tubes for same effect. I can't think of anything else (save replacing parts).