Shopsmith Forums

sehast wrote:Extension table alignment is a concern for me as well. I thought it would be corrected when I upgraded from the 510 to the 520 but it didn't work out that way. I still can't get consistent fence alignment on the extension table (within .005"). So that is a consideration of killing two birds with one stone and justifying the additional cost and work of implementing the Double Tilt. Why do you think the new headrests will be better? Well, I guess we will know for sure in a couple of weeks after you get the upgrade done and do the measurements.

The original headrest is not a precision 'rest'. Indeed one side of it is adjustable. Improper adjustment of that is IMHO the cause(one anyway) of the incompatibility between the ends.

The double tilt has rigid commonality on both ends which should tend to eliminate 'differences'.

The goal of 0.005 is IMHO probably too optimistic. It depends upon the SPT bores. Same for the left right tilt of the table at both ends.

It remains to be seen if the legs/floor will affect all this.

JPG wrote:

sehast wrote:Extension table alignment is a concern for me as well. I thought it would be corrected when I upgraded from the 510 to the 520 but it didn't work out that way. I still can't get consistent fence alignment on the extension table (within .005"). So that is a consideration of killing two birds with one stone and justifying the additional cost and work of implementing the Double Tilt. Why do you think the new headrests will be better? Well, I guess we will know for sure in a couple of weeks after you get the upgrade done and do the measurements.

The original headrest is not a precision 'rest'. Indeed one side of it is adjustable. Improper adjustment of that is IMHO the cause(one anyway) of the incompatibility between the ends.

The double tilt has rigid commonality on both ends which should tend to eliminate 'differences'.

The goal of 0.005 is IMHO probably too optimistic. It depends upon the SPT bores. Same for the left right tilt of the table at both ends.

It remains to be seen if the legs/floor will affect all this.

In a way I disagree with this statement. I do not believe that a properly assembled Mark 5/V will be adversely effected by "typical" deviations in floor surfaces. Now if you run it out onto cracked and shifting drive ways or onto gravel/dirt areas that may be an issue. But not typical garage floors.

We will see, I hope soon.

I did not say it would. I am curious if it might. An old question in my mind.

My hypothesis on why the Extension Tables do not align so as to allow end to end swap may be getting shot down (by myself). Part of my theory has been based on the fact that the bench tube separation was somewhat uncontrolled. That is definitely not the case. While the bench tube openings (1 7/8") are larger than the bench tubes (1 3/4") then bench tubes are still properly located with respect to one another.

This sketch shows why I have come to this conclusion. I have been spinning my wheels on this one.

On the left is a tube installed in a hole that fits. On the right is a 1 3/4" tube in a 1 7/8" opening. But notice how the tube is pushed into the upper right of the opening. The top of the tube and the outside edge of the tube are still properly located.

The tube lock bar forces this relationship.

The rectangular area is intended to depict the limitations established by the end castings. The lock bar tends to push the tubes up and out toward those boundaries.

This may or may not apply, but I think it does... What i learned with my 700 pound all cast iron Powermatic 3520 lathe... I was having trouble with my drive center and tailstock centers lining up. The points should touch when the gap is closed... Alignment. There is no adjustment for that... but there is! Went to the manual. The lathe has to be level with the floor, dead level. That is where floor levelers come in, the little pesky ones that screw into the legs to adjust the height... (Which Shopsmith lacks). Even cast iron will flex and cause alignment issues. I had to simply adjust those feet until the points aligned. Took all of three minutes. Never have to do it again unless I move the lathe.
Now Shopsmiths twist much easier then cast iron, and are portable, and don't have leg levelers. Everytime I move any of my Shopsmiths, i risk throwing alignment out. How much depends on my floor. What I have done, and has help greatly, is marked my floor where the machine will be used. I do my alignments there. It has helped tremendously.

You are obsessing with the wrong part! The openings are clearance holes.

Look at the base casting where the bench tubes are installed. There is the base itself that determines the 'vertical' positioning.

Look to the outer side. There is a small rib that determines the lateral positioning. That rib dimension is different on the 1 7/8" tube bases(1/16" less protrusion).

The clamping bar does force the bench tube into that small rib 'stop'.

What is missing is a 'tube end stop'. That has been corrected with the dual tilt base.

Chris is unsettling the rigid base/leg theory.

I do not see how bench tube c-c distance would affect 'the problem'. Twist yep.

It won't be long now. I just checked online status and my Dual Tilt requisition status has changed from "backordered" to "being shipped".

JPG, You made a statement earlier in this post that I thought was incorrect. I am here now to tell you that I was wrong. The Tube Tie Down does not force the Bench Tubes outward until they contact the holes in the castings. The ribs, of which you spoke, establish the lateral limit.
This image, probably in addition to some you posted, show the ribs on the sides of the Bench Tubes. It also shows that the through holes are just a little bit larger than the tubes.

I am now ready for my Dual Tilt Kit. To reduce weight, I dropped the motor pan, removed it and the motor, removeds the headstock and carriage and removed the Base Arm Assembly from one end of the Tubes. The other Base Arm Assembly will come off when I am ready to install the new ones.

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JPG wrote:.

I don't know if that was intended as a question or not but yes there is a 1/16" gap on either side of the tubes. The holes are 1 7/8" in diameter and the tubes are 1 3/4" od.