Are Your Extension Tubes Straight

pennview · Post by **pennview** » Wed Jul 04, 2012 8:24 am

The misalignment when swapping an auxiliary table from end to end could also be the result of the headstock being the culprit. If it is canted ever so slightly in relation to the tubes, the fence could be at a different angle when moved to the opposite end of the Shopsmith. I'm guessing that one could counteract this by reversing the table when mounting the auxiliary table at the opposite end.

dusty · Post by **dusty** » Wed Jul 04, 2012 8:41 am

pennview wrote:The misalignment when swapping an auxiliary table from end to end could also be the result of the headstock being the culprit. If it is canted ever so slightly in relation to the tubes, the fence could be at a different angle when moved to the opposite end of the Shopsmith. I'm guessing that one could counteract this by reversing the table when mounting the auxiliary table at the opposite end.

This is a strange phenomena. It seems as though careful assembly would result in the capability to do a perfect alignment that would allow the interchange. However, this has not been my experience.

It has become something of an obsession for me. Having interchangeability is absolutely not necessary.

There are weak points (like the Tie Bar to Headrest) that contribute to this but I have gone so far as attaching the Headrest and the Base Arm Assembly to my work bench and have not achieved any improvement to speak of.

In theory, if the Base Arm and the Headrest are properly positioned (in respect to one another) absolute interchangeability would be possible. I would even be satisfied if I could do this without interjecting the headstock into the setup but I have not been able to do even that.
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This, for me, has become one of those things that I just must do. A "Don't tell me that it can't be done" sort of thing. If I succeed, I will have accomplished nothing that is of interest to this community but I will be satisfied.

robinson46176 · Post by **robinson46176** » Wed Jul 04, 2012 10:28 am

Watch 2 episodes of Roy Underhill's show and call me in the morning...

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JPG · Post by **JPG** » Wed Jul 04, 2012 2:32 pm

dusty wrote:This is a strange phenomena. It seems as though careful assembly would result in the capability to do a perfect alignment that would allow the interchange. However, this has not been my experience.

It has become something of an obsession for me. Having interchangeability is absolutely not necessary.

There are weak points (like the Tie Bar to Headrest) that contribute to this but I have gone so far as attaching the Headrest and the Base Arm Assembly to my work bench and have not achieved any improvement to speak of.

In theory, if the Base Arm and the Headrest are properly positioned (in respect to one another) absolute interchangeability would be possible. I would even be satisfied if I could do this without interjecting the headstock into the setup but I have not been able to do even that.
"
This, for me, has become one of those things that I just must do. A "Don't tell me that it can't be done" sort of thing. If I succeed, I will have accomplished nothing that is of interest to this community but I will be satisfied.

I unnerstan, but disagree with the last part. I have been obsessed myself with supposedly unattainable goals.

Re a canted headstock mentioned above]are[/B] capable of pulling the base out of alignment if they become 'helical'.

pennview · Post by **pennview** » Wed Jul 04, 2012 4:12 pm

Originally posted by JPG: Re a canted headstock mentioned above; if such a thing exists, the cant would be the same end to end as long as the way tubes do not form a helix, but rather be co-planer along their long axis.

All of that may be true if one ignores the alignment of the fence in relation to a sawblade. Toe out of the fence on one side of the headstock, begets toe in on the opposite side if things are true. If the headstock were canted, the problem is magnified.

JPG · Post by **JPG** » Wed Jul 04, 2012 11:15 pm

pennview wrote:All of that may be true if one ignores the alignment of the fence in relation to a sawblade. Toe out of the fence on one side of the headstock, begets toe in on the opposite side if things are true. If the headstock were canted, the problem is magnified.

I guess I need to understand what you are referring to as 'canted'.

If it is the quill shaft not parallel to the way tubes, all the table alignments are to that cant angle(perpendicular to the quill). That angle will be the same at all positions on the headstock along the way tubes if they are co-planer(not 'twisted').

Assuming the spt mount bores are the same angle to the way tubes at both ends(that assumption being invalid is what is bugging Dusty), the cant angle of the extension table will be the same on either end.

One cannot 'ignore' the alignment of the fence to the sawblade(quill). A fence that aligns correctly to the right side mounted extension table will also align correctly to the left side mounted extension table(same table) if the table is correctly aligned to the blade(therein lies the problem-getting the single table to align correctly at both ends).

A properly aligned fence IMHO has NO toe 'out', but is totally perpendicular to the quill(parallel to the blade sides).

Yes potential kick-back can be reduced by having the rear end of the fence having more clearance, but that does have the opposite effect when mounted to the left of the blade. That is why IMHO the 'extra' clearance should NOT be attempted.

A second extension table for use only on the left has been discussed. A second fence adjusted for exclusive use to the left would also 'work'.

pennview · Post by **pennview** » Thu Jul 05, 2012 7:24 am

If you can get a fence perfectly aligned to the saw blade, you better at aligning things than 99.44 percent of woodworkers.

dusty · Post by **dusty** » Thu Jul 05, 2012 9:07 am

pennview wrote:If you can get a fence perfectly aligned to the saw blade, you better at aligning things than 99.44 percent of woodworkers.

We must always remember, in these alignment discussions, that "perfectly" is relative.

I have previously stated that for most of my alignment requirements I consider anything within +- .005" to be perfect. I must admit that when doing tasks like main table alignment, I will strive for a tighter tolerance but I won't dwell on it. Conversely, for the main table and for the drill press, nothing greater than .005" is tolerable.

What is tolerable for you is strictly up to you. I just hope that everyone realizes that when the table saw fence and blade are part of the discussion, being out of alignment can be a real safety hazard.

pennview · Post by **pennview** » Thu Jul 05, 2012 9:37 am

By Dusty: I just hope that everyone realizes that when the table saw fence and blade are part of the discussion, being out of alignment can be a real safety hazard.
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You're right here, Dusty. Some discussions on this subject get too convoluted when the real point is woodworking and getting things done safely. Ripping wood requires careful attention to alignment.

JPG · Post by **JPG** » Thu Jul 05, 2012 11:40 am

pennview wrote:You're right here, Dusty. Some discussions on this subject get too convoluted when the real point is woodworking and getting things done safely. Ripping wood requires careful attention to alignment.

Any machining endeavor requires rigid attention!!!!, but sawing and more so rip sawing can become injurious if one is not fully engaged in every moment.

Knowing the exposures and avoiding them are a must!!!

Now back to 'alignment'!]perfectly[/B] aligned.

It is as good as I can get it with the tools at hand(no dial indicator). That said there have been times when it became evident that perfection was nowhere near. Those times resulted in modifying the 'procedure'.

One can get very close if attention is paid to NOT making invalid assumptions(verifying everything) and at times using feel or feeler gauges.

One assumption to not make is that the fence sides are straight! My original M5 is concave front-rear, so adjustments are determined at the ends. The depressed center is no doubt the result of repeated bolting add on fences to it 'securely'.