Main Table Tubes

[DLB]

I'm doing (attempting) a double tilt upgrade on a 520 and am stuck on the very last step, re-installing the main table into the carriage. The upgrade includes new main table tubes with racks on both sides that enables (in theory, not so far for me) the table to be reversed. Mine goes in normally to the point where it should engage the pinions. From there on I meet stiff resistance, it feels like it is trying to cut new gears. Same problem with the table reversed (both racks).

I tried each tube individually by using a '500 carriage' and both worked normally. I tried a 510 carriage and had the same problem as above. I tried a 510 table on both carriages and both were fine.

In looking at the tubes it looks like they are rotated slightly off true. I'm not sure how to quantify that and have no clue what the tolerance might be. This is my best theory right now.

Ideas? I feel like I'm missing something obvious. I waited on hold for a while with SS CS. Sent an email instead.

- David

[jsburger]

I'm doing (attempting) a double tilt upgrade on a 520 and am stuck on the very last step, re-installing the main table into the carriage. The upgrade includes new main table tubes with racks on both sides that enables (in theory, not so far for me) the table to be reversed. Mine goes in normally to the point where it should engage the pinions. From there on I meet stiff resistance, it feels like it is trying to cut new gears. Same problem with the table reversed (both racks).

I tried each tube individually by using a '500 carriage' and both worked normally. I tried a 510 carriage and had the same problem as above. I tried a 510 table on both carriages and both were fine.

In looking at the tubes it looks like they are rotated slightly off true. I'm not sure how to quantify that and have no clue what the tolerance might be. This is my best theory right now.

Ideas? I feel like I'm missing something obvious. I waited on hold for a while with SS CS. Sent an email instead.

- David

It sounds to me that the pin holes that attach the tubes to the table are drilled slightly out of square with the racks. Individually they work fine as you stated. There is no difference between a 510 carriage and a 520 carriage. There is no difference between a 510 table and a 520 table except the fence and the rails. The tables are the same.

When you pin the tubes to the table and it doesn't work, I don't think you are missing anything obvious. It can only go together one way. If the tubes look slightly off and they don't fit they are out of tolerance. I think SS CS is the only answer.

[DLB]

It is much easier to measure the error with the parts removed, but I don't know how many times those pins should be driven in and out. The angle between the holes and the flats at the bottom of the rack is 2.4 degrees on the 'bad' ones, both tubes measured the same. The original parts measured 0.3 degrees in the opposite direction, also both the same.

While I don't know part tolerance I confirmed that my machine will not handle a total error anywhere near this large.

- David

[reible]

I have a set of tubes waiting to be installed. If you can describe how you did the measurements I can see what they measure if it is an absolute measurement.

Those pins are a once use only. So if you contact shopsmith and they send you new tubes make sure they include the pins too.

I will dig the tubes out tonight to make sure I know where they are. It is one of my spring projects anyway so might as well get the stuff together now.

Ed

[JPG]

Two possible errors.

The pin hole is not perpendicular to the gear rack(s).

The two gear racks are not parallel.

Either one is a defect I believe.

I am guessing the pin hole. If so the error should be equal/opposite on the two gear racks.

[DLB]

The tracks are parallel with one another. The part of this that has me dumbfounded, why I thought I was missing something, is that it can be wrong, i.e. not controlled by tooling/process/quality. This is how I measured, note that the second photo shows more of the complete setup. All pictures have an original tube on the left and a new tube on the right. I put the tubes on a table with a long 3/8 inch drill bit through both sets of holes and zeroed the Wixie on the shank:

Zero Reference

IMG_7974.jpg (444.64 KiB) Viewed 11335 times

I then used a flat bar to feel the flat at the end of the rack. I used a T-Track guide that was handy. First measurement is the original:

Baseline

IMG_7977.jpg (369.35 KiB) Viewed 11335 times

Then the suspect new tube:

New Tube

IMG_7975.jpg (305.81 KiB) Viewed 11335 times

This setup isn't perfect but gave me repeatable results. It was easier to do than to photograph, that 'three hands' thing rearing its head. The sequence of events led to this being a confirmation and quantification of what I had already determined was the problem.

Note - my earlier comment about the original tube error being in the opposite direction appears to be incorrect.

- David

[JPG]

I am curious(and expect it to be so) if rotating the new post 180° produces the same result with the gear rack on the opposite side. That would mean only the hole is incorrect.


Good luck explaining this to CS!

[dusty]

If your tubes are removed from the table, can you lay them side by side with a rod (drill bit) through the holes of both tubes simultaneously. If you can, then measure the relative angles of the flats. These angles should be the same and should be the same as the angle of the rod (drill bit).

Done on a perfectly flat and horizontal bench top, the angles should all be identical. Any deviation identifies and quantifies your problem.

How do the holes in the tie bar look? Nice clean round (not elongated) holes with no burrs??

[DLB]

I am curious(and expect it to be so) if rotating the new post 180° produces the same result with the gear rack on the opposite side. That would mean only the hole is incorrect.

Yes, true for both sides of both tubes within a small error tolerance for my setup.

Good luck explaining this to CS!

Indeed. Thanks. CS said I needed to get an appointment for engineering support. I'm trying to remain optimistic, at the same time planning that this machine may be down a while. Sadly, I just did a PP DIY on the same machine and am itching to use it. Ideally with a table. So far I've used it to sharpened my carpenter's pencil! Working the problem...

If your tubes are removed from the table, can you lay them side by side with a rod (drill bit) through the holes of both tubes simultaneously. If you can, then measure the relative angles of the flats. These angles should be the same and should be the same as the angle of the rod (drill bit)...

How do the holes in the tie bar look? Nice clean round (not elongated) holes with no burrs??

Yep, all the same but all different from the rod. Out of tolerance which I'm only able to estimate, but I think +/- 0.5 degrees -ish. I don't expect to ever know.

For now I'm eliminating the tie bar holes on the table from consideration. They are not pretty, the pins are an interference fit, and it's steel pin Vs. Aluminum hole. They are neither clean nor without burrs, not technically round but not elongated. They are not made to take a large number of re-pinnings. We can say I have ruled out my plan to re-install the original tubes for now.

- David

[DLB]

I wanted to add some info to expand on my last post, possibly useful to others. The pins are tapered and also have three grooves down the sides, similar to flutes on a fluted dowel pin. These 'flutes' dig into the metal as the pin is driven in.

Tapered pins

IMG_7980.JPG (901.32 KiB) Viewed 11213 times

Since these pins are used you can see near the bottom that the edges of the grooves starts out sharp, then that sharp edge has flattened out some where the pin was driven into the steel leg. The part that remains sharp near the bottom is the portion that only goes into the aluminum tie bar.

Since the pins are tapered both the 'flutes' and impact are more pronounced at the outside of each hole. And since the tie bar is aluminum while the pin and leg are steel it is more pronounced on the tie bar. This is what my tie bar looks like from being pinned twice:

Tie Bar (Front Outside)

IMG_7978.JPG (734.17 KiB) Viewed 11213 times

- David