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A scraping mystery

Your asking for help and then it seems from the length of your replies your arguing with our advice. I'm sure it's simple and if I was there I could figure it out in 5 minutes. Move the table to each end and check it with the sweep. Bad bearings could be the issue. Take the table off and flip it over TSluts down and tap it with a softblow hammer. It should have a thud sound if its flat. Hinge it. See what happens. Use a micrometer and measure the table top to bottom. Or use a surface gage and measure the flats. In and out and the length. The picture of the scraping top looks like 2 PPI in 3". Those cheap Asian made machines has terrible workmanship. I'd never buy one. Remember were trying to help you. You asked for it.
 
I absolutely promise to tell you if a particular issue is provably not the problem.

If that is "arguing" and offensive, then so be it, I can't help the facts.

Could I be wrong about one of the things? Sure, anyone can be wrong.
But, many of them are measured, with tools that are known accurate. If it is suggested that a measurement that has been made several times in different ways with different tools is "wrong", I'll measure it again. And if it is still OK, I'll say it is not wrong as far as I am concerned for the moment, until and unless I can find that it is wrong after all.

I'll stop "arguing" now. In fact, I will stop posting in the thread, so you won't have to look at it.
 
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The column may have a crack. Simply broken material. You don’t see anything but it could be there. Do you have an outline?
 
I've read your conditions above. Option one, the table is equal thickness across it's entire length on both sides, but one side is offset from the other side. Table would spot correctly top and bottom but it could be shaped like a trapezoid with angle caused by the 0.003 difference. For this to blue up for full contact on the table ways, the inner way would have to be 0.003 taller than the front way. Can't quite tell from the observables listed if you've checked that both front and rear ways are exactly the same height, with the table taken off.
 
I absolutely promise to tell you if a particular issue is provably not the problem.

If that is "arguing" and offensive, then so be it, I can't help the facts.

Could I be wrong about one of the things? Sure, anyone can be wrong.
But, many of them are measured, with tools that are known accurate. If it is suggested that a measurement that has been made several times in different ways with different tools is "wrong", I'll measure it again. And if it is still OK, I'll say it is not wrong as far as I am concerned for the moment, until and unless I can find that it is wrong after all.

I'll stop "arguing" now. In fact, I will stop posting in the thread, so you won't have to look at it.
We can see your frustrated. I'm sure it was hard for you to ask for help as your one of the pros on here and have helped people over the years. What I asked or told you is something I would do to troubleshoot for a PM member know matter who they were. Why not try what we suggested even though you already done it.
 
It is fixed.

Can't tell you what the problem was...... because I don;t know for sure. I can tell you what I DID, though.

First, I decided that I was getting nowhere, since nobody but me can see the thing, and I had it to do.

Then I recalled a very wise statement made by the father-in-law of a former employer. He owned and operated one of the best auto repair shops in town, and was known for fixing tough problems.

His rule was "fix what you know is wrong, NOT what you think is the problem".

So I simply went through the thing again, and any time I saw ANY repeatable measurable deviation, I re-scraped that part to take it out. Column, knee, saddle, and table were checked. It was a marathon session, but I had the time available today.

And, at the end of the process, there was no longer any significant tram error.

Nothing was very far out individually. So, I figure the issue was probably that most of the small deviations were in the same direction, and they simply added up. That would align with my inability to find a single and particular cause for the error.
 
The errors were spread around pretty much. A big chunk of it may have been wear, since the old scraping was less distinct in a number of places.

Yes there was some lower PPI, although probably not below 15. I don't recall what axis had the lowest. It has had a good deal of use.

It's no Moore, but I did want it back to in-tram. If the head nodded, I could have done fine for a while just adjusting that tram.
 








 
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