Page 2 of 9
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 3:06 pm
by reible
If you look back to some years ago you will find that I was able to get a setup where the extension table could be mounted on either side and be within .005", my go to dimension. This was done with the double tilt but there is still movement at the tilt axis so for long term use and since I still have fix tables for each side it is much easier just to do as I have always done and have a right and left table.
Previous I was never able to get any where near that close so things have improved with the double tilt but still not enough for it to be fool proof.
BTW just getting the tubes to slide in is no proof that you have a good enough alignment. You also have to take into account that the rip fence is normally set with a slight off set for safer use. So getting accurate results from it from side to side is also an issue.
Anyway I no longer rip wider parts, a track saw does a so much better job of that task, like going from the dark into the light.
Ed
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 3:31 pm
by RFGuy
reible wrote: Tue Dec 08, 2020 3:06 pm
Anyway I no longer rip wider parts, a track saw does a so much better job of that task, like going from the dark into the light.
Ed
+10. Difficult to go back to a tablesaw after using a tracksaw, particularly for sheet goods.
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 3:41 pm
by dusty
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 4:17 pm
by algale
A couple more points.
1. What you've shown above Dusty is the leg bore holes and bench tube bore holes are perpendicular within the resolution/error specs on those angle cubes. Even a small error that is within the resolution/margin of error of those cubes is likely going to be enough to make your tables not swappable within the level of accuracy you aspire to.
2. The above doesn't address the issue of whether the horizontal line through the center of bore holes for the table legs are parallel. I for one highly doubt even the double tilt castings with their built in stops for bench/way tubes are machined to tolerances sufficient to achieve perfect parallelsim from end to end. And if the bench/way tubes vary even a tiny fraction of an inch in length or the ends are not cut perfectly square, that could impact that too.
3. I just think there are too many variables and tolerances involved. Even the extension table castings themselves including the machining and drilling of the holes for the threaded studs could impact things a tiny fraction as could the casting at the top of the legs that the legs fit into. As I was trying to say and JPG correctly summed up, when you align any of the tables you are compensating for all those tiny variable and it is a lot to expect them to swap out side to side and not get some kind of variance.
4. If this were achievable and maintainable with the double tilt, I have every confidence that either you or Reible already would have achieved it and maintained it already.
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 5:08 pm
by DLB
To me the most useful thing about having an extension table aligned for left/right on a conventional base (one Headrest one Base) is that it eliminates the variability of how the Headrest is connected to everything else. Without a way to align it, and there isn't one in any SS manual I've seen, the Headrest can have widely varying relationship with the rest of the Mark. But if you adjust how the Headrest mounts to optimize for the extension table, this results in very good alignment of the Headrest SPT mount to everything else. (An extension table aligned in the Base is very close to 'nominal.' In the dark ages, this was done with shims and in my experience the variation in shim thickness among the four mounting bolts was very small. Thus, the same table to align the Headrest is a good reference tool.)
- David
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 5:24 pm
by dusty
algale wrote: Tue Dec 08, 2020 4:17 pm
A couple more points.
1. What you've shown above Dusty is the leg bore holes and bench tube bore holes are perpendicular within the resolution/error specs on those angle cubes. Even a small error that is within the resolution/margin of error of those cubes is likely going to be enough to make your tables not swappable within the level of accuracy you aspire to.
2. The above doesn't address the issue of whether the horizontal line through the center of bore holes for the table legs are parallel. I for one highly doubt even the double tilt castings with their built in stops for bench/way tubes are machined to tolerances sufficient to achieve perfect parallelsim from end to end. And if the bench/way tubes vary even a tiny fraction of an inch in length or the ends are not cut perfectly square, that could impact that too.
3. I just think there are too many variables and tolerances involved. Even the extension table castings themselves including the machining and drilling of the holes for the threaded studs could impact things a tiny fraction as could the casting at the top of the legs that the legs fit into. As I was trying to say and JPG correctly summed up, when you align any of the tables you are compensating for all those tiny variable and it is a lot to expect them to swap out side to side and not get some kind of variance.
4. If this were achievable and maintainable with the double tilt, I have every confidence that either you or Reible already would have achieved it and maintained it already.
To my satisfaction, I have achieved that. I would show that on my shop machine except that I have a jointer at one end and I no longer move that jointer around unless I must.
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 5:28 pm
by JPG
I disagree that raising to vertical and returning will alter positioning of the moving parts to the stationary parts.
IF the surfaces the tie rod rests on AND the tapered locking pin are correct repeatability is adequate. That means NO slop between the parts when locked down.
Another persnickety thing to adjust.
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 8:28 pm
by algale
dusty wrote: Tue Dec 08, 2020 5:24 pm
To my satisfaction, I have achieved that. I would show that on my shop machine except that I have a jointer at one end and I no longer move that jointer around unless I must.
I'm glad you have achieved this. But now I am completely confused why you even started this post.
Re: Parallel Extension Tables
Posted: Tue Dec 08, 2020 9:12 pm
by JPG
The headrest end IS adjustable, but only in a single plane to eliminate twist in the way tubes relative to the bench tubes.
Re: Parallel Extension Tables
Posted: Wed Dec 09, 2020 4:14 am
by dusty
algale wrote: Tue Dec 08, 2020 8:28 pm
dusty wrote: Tue Dec 08, 2020 5:24 pm
To my satisfaction, I have achieved that. I would show that on my shop machine except that I have a jointer at one end and I no longer move that jointer around unless I must.
I'm glad you have achieved this. But now
I am completely confused why you even started this post.
Have you come to that same conclusion? Do you now have extension tables that you believe can be swapped back and forth? Has anyone who has read any part of this thread or of any of the others that exist been challenged to do the same? I would like some part of this community to achieve to that same level, I would like to be able to write a procedure that if followed by a newbe would result in the same.
I can not because ya'll can not.