Lathe Test Bar - Someone's in error

[lynnl]

I have several of the Village Press hard cover books from HSM and PIM, and in browsing through the Projects Three book came across an article by Edward G. Hoffman "Wiggler Bar and Test Bar."

Confusion sometimes comes easy when dealing with left vs right, in vs out, etc. So I'm wondering if my mind is tricking me here.

In describing the test bar, Edward says "...take a 10 to 12" bar .875 to 1.00 dia., center drill both ends, mount between centers, take a light skimming cut until it's cleaned up all around. Then measure at both ends. If larger at tailstock end, the tailstock should be moved AWAY from you. If larger at headstock end, the tailstock should be moved TOWARD you."

That seems bass ackwards to me! Did Edward make a mistake? Or is Lynn making one now?

[metalmagpie]

Buy the lathe buttons from Brownell's. When you measure over them and get the right number, your headstock center and tailstock center are aligned. Then make your test bar.

metalmagpie

ps I think I agree with you

[TGTool]

I have several of the Village Press hard cover books from HSM and PIM, and in browsing through the Projects Three book came across an article by Edward G. Hoffman "Wiggler Bar and Test Bar."

Confusion sometimes comes easy when dealing with left vs right, in vs out, etc. So I'm wondering if my mind is tricking me here.

In describing the test bar, Edward says "...take a 10 to 12" bar .875 to 1.00 dia., center drill both ends, mount between centers, take a light skimming cut until it's cleaned up all around. Then measure at both ends. If larger at tailstock end, the tailstock should be moved AWAY from you. If larger at headstock end, the tailstock should be moved TOWARD you."

That seems bass ackwards to me! Did Edward make a mistake? Or is Lynn making one now?

You're right. If the part is larger at the tailstock end, it needs to be moved closer to the operator.

[lynnl]

Thanks. I was pretty sure it was just a typo or editing error in the book, but there's always that little niggling doubt in challenging something you see in print. "...am I overlooking some little detail..?"

Edward Hoffman was a talented guy, so I know it was just one of those little gremlins that crept into his description.

[J Tiers]

Yes...

Moving away puts the center farther from the tool, making the diameter larger. Moving toward does the reverse.

[doctor demo]

You're right. If the part is larger at the tailstock end, it needs to be moved closer to the operator.

Unless you are making the measurements while standing behind the lathe, I agree with you.

Steve

[Illinoyance]

I imagine Hoffman is plenty embarrassed. Apparently Hoffman didn't proofread or the proofreader didn't know anything about lathes.

[lynnl]

Errors seem all the easier when dealing with pairs, e.g. tailstock/headstock, larger/smaller, toward/away.

[George Bulliss]

I imagine Hoffman is plenty embarrassed. Apparently Hoffman didn't proofread or the proofreader didn't know anything about lathes.

I imagine he did proofread his work, but it's easy for things like that to slip by when proofreading your own words. Knowing what the words are supposed to be can sometimes get in the way of seeing what the words actually are. It happens with every author and every article, just how it goes.

Now, the editor definitely should have caught that one. I would like to think I would have spotted it, but things slip by me sometimes as well. However, by the time it hit the book, the editor had two chances at catching it; once in the original magazine article and once when compiling the book.

The editors from that time in the magazine's history were far better than me at spotting grammar and stylistic errors, but had no machining experience and simply trusted the authors on things like this. When reviewing old material I see a lot of similar errors that made it to print.

[QSIMDO]

Buy the lathe buttons from Brownell's. When you measure over them and get the right number, your headstock center and tailstock center are aligned. Then make your test bar.

metalmagpie

ps I think I agree with you

Wouldn't that be inaccurate if (when) the ways have wear near the chuck?

[Toolguy]

What I do is have a test bar that it the same diameter for the full length. Instead of turning it down, I use a dial indicator on the carriage to get the same reading at both ends. If the tailstock needs adjusting, the indicator is right there to tell you how much and which direction to move it. This is way faster than doing test cuts and saves the bar in perfect condition, rather than turning it into chips.

[old mart]

It's worse than just back to front, just cleaned up either end is not good enough. It should read turned down each end to the same cross slide reading, not till just cleaned up which could mean anything.

I use an eleven inch test bar between centres, the chuck end one being freshly skimmed in a collet and a lever type dti on the saddle. Also, with the dti reading the top of the bar, the height of the tailstock can also be checked. The museum's Smart & Brown has shims between the two halves of the tailstock for the height.
These tests can be repeated with the tailstock quill in and extended.

[Baz]

yes but the assumption is that you don't have a bar with perfectly centred ends, let alone known to be constant width.
(edit: replying to post before last)

[Mcgyver]

It happens with every author and every article, just how it goes.

its the author's lament, get 999 things right and the one that slips through is where the buzz is . George is modest, he does a tremendous job with the whole job of editing, tip of the hard hat to him.

What I do is have a test bar that it the same diameter for the full length. Instead of turning it down, I use a dial indicator on the carriage to get the same reading at both ends. .

I do the same. you're there quickly vs the test and retest needed with test cuts.

[lynnl]

I should point out, for any here not familiar with those Project Books, that this error/book was printed about two editors before George Bulliss'es time at Village Press.

I also should mention that the author's described purpose for that "test bar" was mainly for resetting the tailstock after it had been set over, e.g. turning a taper.

(added) I have a couple of really nice chromed piston rods from a pair of McPherson struts that serve such purposes nicely. Far more precise than any I'm likely to produce.