Do the Way Tubes Have an Effect on Alignment

[dusty]

There have been many discussions here on the forum regarding the overall alignment of a Mark 5/V. Seldom do these discussions spend any time on the significance of Bench Tubes and Way Tubes.

I think we each tend to assume that the tubes are all parallel to one another. Why might we do that? Simply because they are not adjustable.

This is exactly why I am writing this. I happen to know that my tubes are not all parallel to one another.

I know not why nor do I know that it is causing a problem of any sort.

I began looking into this because of a discussion regarding the set screw, in the Headrest, that contacts the underside of the Tie Bar.

To try to understand this, I built a simple jig that serves as a "Caliper for the Way and Bench Tubes".

[ATTACH]18073[/ATTACH]

With this caliper I have convinced myself that there is something different about one of my two Mark Vs. In one the tubes rest exactly like you would expect but in the other there is a gap.

[ATTACH]18074[/ATTACH]
Left End of the Shorty

[ATTACH]18075[/ATTACH]
Left End of Unmodified Mark V

[JPG]

There have been many discussions here on the forum regarding the overall alignment of a Mark 5/V. Seldom do these discussions spend any time on the significance of Bench Tubes and Way Tubes.

I think we each tend to assume that the tubes are all parallel to one another. Why might we do that? Simply because they are not adjustable.

This is exactly why I am writing this. I happen to know that my tubes are not all parallel to one another.

I know not why nor do I know that it is causing a problem of any sort.

I began looking into this because of a discussion regarding the set screw, in the Headrest, that contacts the underside of the Tie Bar.

To try to understand this, I built a simple jig that serves as a "Caliper for the Way and Bench Tubes".

[ATTACH]18073[/ATTACH]

With this caliper I have convinced myself that there is something different about one of my two Mark Vs. In one the tubes rest exactly like you would expect but in the other there is a gap.

[ATTACH]18074[/ATTACH]
Left End of the Shorty

[ATTACH]18075[/ATTACH]
Left End of Unmodified Mark V

That 'high' tube is the one not resting on 'the screw'!]parallel[/B]'.

The end casting should be positioned on the bench tubes(and indirectly the way tubes/tie bar) such that the mid point between the spt mounting tubes coincides with the upper rear shaft axis. This is adjusted by rotating the end casting about a vertical axis. i.e. the amount of intrusion of each tube into the end casting. This is applicable to the right end as well(that places the mid point between the right end spt mount tubes to coincide with the quill shaft axis.

When the way tubes become truly parallel with the bench tubes, the extension table can be made co-planer with the main table, and the rip fence reference edges made parallel on the right end.

Then since the left end aligns with the rear shaft the same as the right end, and, the way tubes are not 'twisted', the extension table will also be coplaner at the left end and the fence reference edge as well.

Those are my preliminary conclusions, but I do not have a dial indicator to be exact. I have added the stud/nuts mount to my original goldie extension table and have been eye balling with 2' combination square/straight edge. I also made a 'reference' jig to provide the spt mid point from a table leg sans table.

I will shows all this in a separate thread (with pix) after changing the tie bar end to a modified hinge end and again 'measuring' etc.

I am posting this here so you will have an opportunity to think how it may help you with your 'experiment'.

I have always maintained the parallelness of the bench/way tubes to each other is crucial to minimizing other alignment problems, especially spt alignment.

The spt shaft alignment should require little to none front-rear adjustment(assuming the spt shaft/mount tubes positioning[straight mounting tubes should align]), but the spts that are driven by the lower(Idler) shaft must have eccentric mounting tubes to accommodate the idler shaft repositioning front to rear created by belt tension adjustments.

[keakap]

There have be...is. I happen to know that my tubes are not all parallel to one another.

I know not why nor do I know that it is causing a problem of any sort.

I began looking into this because of a discussion regarding the set screw, in the Headrest, that contacts the underside of the Tie Bar.
...

Do they have an effect? DO they have an effect!

My "you betcha" moment came a few minutes after installing the "Lift-Assist" (the older weaker one, no less!) when I was going thru the table alignment checks. And that tie bar set screw? FUHgeddabowdit! The bar was now a good 1/4" above that screw, totally disengaged. The right Ext table was not just in a different plane from the left, I could see the misalignment from the front door of the 7-11 store a mile away. (WITH the shop door closed!)
So out came the Lift-Assist (and that's a lotta work, btw).

So far the most effective tool I've found for "aligning" the Mark V's foundational support members is a nice 2lb. ball peen hammer applied vigorously to the SS legs. {This therapy is best administered following your favorite professional sports team taking a monumentally important loss within their division AND your doctor having told you that cheeseburgers and beer are now taboo, for you.}

[algale]

The end casting should be positioned on the bench tubes(and indirectly the way tubes/tie bar) such that the mid point between the spt mounting tubes coincides with the upper rear shaft axis. This is adjusted by rotating the end casting about a vertical axis. i.e. the amount of intrusion of each tube into the end casting.

JPG,

I think I follow the point highlighted above in red. Just to make sure, let me restate this: I think you are saying that by inserting unequal amounts of the bench tubes into the holes in the head rest (left end casting), you are rotating an imaginary line between the two SPT holes in the head rest such that the imaginary line can be bisected by a line drawn through the axis of rotation of the upper aux spindle (coincidentally also the axis of rotation of the main spindle). Is that correct?

If so, what you say makes makes sense but is contrary to what I thought was the standard assembly procedure, which was to make sure the same amount of bench tube is inserted in both the head rest (left end casting) and the base arm (right end casting).

Are you also suggesting that one should, if necessary, insert unequal amounts of the bench tubes into the base arm (right end casting) if needed in order to have the axis of rotation of the main spindle bisect the hypothetical line between the SPT holes in the base arm (right end casting)?

This is quite an interesting and radical idea to me and seems just the opposite of the the approach taken with the double tilt upgrade, where both castings have affirmative stops to ensure the bench tubes are inserted precisely the same amount in both castings (and which Reible reports has greatly improved his ability to move a table from right to left).

However, once I got my head around what you were saying, it makes sense to me. Incidentally, could this not be accomplished by mounting a SPT in the head rest or base arm on straight (not eccentric tubes) and bringing the headstock up to the SPT to see if the main spindle or upper aux spindle aligned to the spindle in the SPT?

Al

[JPG]

JPG,

I think I follow the point highlighted above in red. Just to make sure, let me restate this: I think you are saying that by inserting unequal amounts of the bench tubes into the holes in the head rest (left end casting), you are rotating an imaginary line between the two SPT holes in the head rest such that the imaginary line can be bisected by a line drawn through the axis of rotation of the upper aux spindle (coincidentally also the axis of rotation of the main spindle). Is that correct?YES But it assumes the correct positioning of the headstock which WILL be affected by a twist in the way tubes

If so, what you say makes makes sense but is contrary to what I thought was the standard assembly procedure, which was to make sure the same amount of bench tube is inserted in both the head rest (left end casting) and the base arm (right end casting). In a perfect world that should produce the same result. That however is not readily attainable with out observing the effect out at the spt drive shaft position(tolerances etc.)

Are you also suggesting that one should, if necessary, insert unequal amounts of the bench tubes into the base arm (right end casting) if needed in order to have the axis of rotation of the main spindle bisect the hypothetical line between the SPT holes in the base arm (right end casting)?Yes Same reasoning. The objective includes left/right table mounting compatibility. Therefore BOTH ends must have a common reference(the drive train axis)(and tubes parallel to the drive train Axis)

This is quite an interesting and radical idea to me and seems just the opposite of the the approach taken with the double tilt upgrade, where both castings have affirmative stops to ensure the bench tubes are inserted precisely the same amount in both castings (and which Reible reports has greatly improved his ability to move a table from right to left).I think Ed's results illustrates(and the seed for my current 'thinking') the need for the end castings to be 'proper'. The combination of the 'hard' stops for the bench tubes(makes that imaginary line perpendicular to the drive train axis) and the hard stops provided with the way tube casting(eliminates tie bar/screw stop confusion) create the necessary alignment that I have described undertaking on a M5. i.e. All 4 tubes parallel and (each tube pair) equidistant from the drive train axis.

However, once I got my head around what you were saying, it makes sense to me. Incidentally, could this not be accomplished by mounting a SPT in the head rest or base arm on straight (not eccentric tubes) and bringing the headstock up to the SPT to see if the main spindle or upper aux spindle aligned to the spindle in the SPT?Yes - assuming(reasonable) that the spt tolerances place the spt drive axle equidistant from the spt mount holes. Height individual tubes will afford some front/rear adjustment. NOTE: repeating your condition - eccentric tubes will not work for this.

Al

Geez I must be lucid after all. Many things have now come together for a more complete understanding of this beast and the reason for multitudinous alignment interactions.

I have been convinced for some time re the 'screw' and the need for parallel tubes, but it took Ed's thread re double tilt and table alignment(extension table both ends) to realize the rest.

SS touting the 'screw' as an spt/drive shaft alignment method added unfortunate confusion. Bill Mayo's recommendation to rotate the end casting(tube insertion distance effect) added sanity.



Sorry Dusty! I did not mean to hi-jack your thread, but I did intend for my initial post to be helpful to you.

[algale]

Geez I must be lucid after all.

Not necessarily; I might just be getting better at deciphering your particular brand of insanity.

[JPG]

[quote="algale"]Not necessarily]

We shall all go together when we go!:D Now ain't that a rapturous thought?

[dusty]

Don't relax yet and don't put the thinking cap away.

I am about to tell you that the tubes (bench to way) are not really parallel.

Way to way are parallel (that's obvious because the spt slide there).

Bench to bench are also parallel.

But the separation (bench to way) on one end of the tubes is different than at the other end.

More to follow, unless I turn out to be wrong and then I'll go hide in the tool closet.

[dusty]

Contrary to my longtime assumptions, the bench tubes are not parallel to the way tubes. I don't know if this is by design or if my two machines are screwed up.

[ATTACH]18082[/ATTACH]
Right End
[ATTACH]18083[/ATTACH]
Left End
[ATTACH]18084[/ATTACH]

[algale]

Contrary to my longtime assumptions, the bench tubes are not parallel to the way tubes. I don't know if this is by design or if my two machines are screwed up.

[ATTACH]18082[/ATTACH], [ATTACH]18083[/ATTACH]

I do not understand this test set up and how it demonstrates a lack of parallelism between bench and way tubes.