What is "Work Tolerance"?

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dml66
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Re: What is "Work Tolerance"?

Post by dml66 »

Better advice has yet to be furnished Harold_V, well taken!

Thank you.
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Harold_V
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Re: What is "Work Tolerance"?

Post by Harold_V »

Welcome! I just hope it's suitable for your circumstances.

One of our readers, Patio, is a close friend. He obtained a SB Heavy 10 and was the reason he and I made acquaintance. I told him that he would, in due time, outgrow his lathe, which he did. He now owns one of the finest of engine lathes (a Cazeneuve), of which precious few were made. It has features not found on any other manual engine lathe. His experiences with his Heavy 10 have allowed him to benefit by the improved features. I have high hopes that you, too, will have a similar experience.

H
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RONALD
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Re: What is "Work Tolerance"?

Post by RONALD »

Here is the chart for my Harrison VS330TR, which I purchased new off the floor at IMTS 1994, it was a retirement gift to myself; I got a lot off because it was an on floor demenstrator.

Anyway, their Accuracy Chart has no mention of "Work Tolernce", but it does have an exhaustive amount of measurment methods some of you might want to use on your lathe.

That VS330TR, was made in the UK, so measurements are in millimeters, I converted some, in red, to FPS.
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Bill Shields
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Re: What is "Work Tolerance"?

Post by Bill Shields »

As I previously asked ..what is the native language of the person writing "work tolerance" ?
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Steggy
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Re: What is "Work Tolerance"?

Post by Steggy »

Harold_V wrote: Wed May 25, 2022 11:07 pm One of our readers, Patio...obtained a SB Heavy 10 and...I told him that he would, in due time, outgrow his lathe...He now owns one of the finest of engine lathes (a Cazeneuve)...

I’d give my left nu...er...lung for a Cazeneuve. In particular, the feed system shows some very innovative thinking. Having one would be like dying and going to heaven.
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dml66
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Re: What is "Work Tolerance"?

Post by dml66 »

Taig Tools says the following about their micro lathes:
Overall working accuracy 0.0005 in.
Max. headstock normality to bed 0.0004 in.
Max. taper bed dovetails over pins 0.0001 in.
"Overall working accuracy" sounds a bit like "Work Tolerance".
rrnut-2
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Re: What is "Work Tolerance"?

Post by rrnut-2 »

I just went onto Cazeneuve's website, looked at their milling machine, WOW. Doesn't have a price though. And you really have to look for
their manual lathe. Again, no price.

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dml66
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Re: What is "Work Tolerance"?

Post by dml66 »

I decided to try an learn more about the taper which appears to be baked into this machine's cake.

I wondered what the outcome would be if I skim turned the 1-1/4" aluminum round workpiece from the top rather than from side. I was able to bubba a HSS cutter into place using the QCTP cam lock to set the "depth of cut", as I said a skim cut. Once I made sure I would personally survive the procedure, starting from the last tapered turn, I made a 200 rpm turn with power feed over the 3" workpiece.

I could see a difference in the chips as the cutter encountered the thicker (spindle) end of the taper. The end result is a taper-free, 3" long workpiece.

I think this shows that the headstock suffers from a horizontal lack of parallelism to the ways; it appears to be vertically parallel to the ways.

Even if I'm right in my assumptions, it's unclear that there's anything I can do about it. I thought about implementing the opposite taper angle in the tailstock but my head started hurting just thinking about it, lol.

The headstock is attached to the ways with two M8 bolts, a third M8 bolt secures the opposite side of the headstock. I thought about shimming the single bolt so the headstock rides higher on the ways allowing me to twist it parallel. If that works, without ruining rigidity, then I'd have to deal with vertical offset at the tailstock. Probably a fool's errand.
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Bill Shields
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Re: What is "Work Tolerance"?

Post by Bill Shields »

in an attempt to keep this as simple as possible:

get the bed of your lathe level from one end of the other - so that there is as little twist in it as you can fix with whatever mechanical adjustments you have available.

get a piece of ROUND GROUND STOCK...maybe 1" in diameter.

put it between centers (assume you can create a center in each end)

then run a DTI with a flat button nose on it -> along front face of the rod and adjust the tailstock to get it as close as you can front to back

then run the DTI along the TOP of the rod -> and see how much it moves.

this will tell you if you have a 'fixable' situation.

if there is a lot of top to bottom deviation -> well....I would decide how much time and $$ and type of work you are going to do...
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Harold_V
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Re: What is "Work Tolerance"?

Post by Harold_V »

The problem with Bill's suggestion is that unless the piece of material is ground concentric with the centers, the small amount of error that is likely to be associated with the test piece will yield less than useful results. You're looking for error that is miniscule.

I ground small precision shafts (parts for guidance systems) for several years---and know from personal experience that the likelihood of centers running true to a part is highly unlikely. A tenth deviation results in two tenths error. It takes very little to invalidate readings from the test he suggested.

You don't think this is true? Drill centers in the ends of a ground piece of stock. Install the drilled piece between two DEAD centers. Apply a DTI to each end of the material (or one end at a time---makes no difference), then spin the piece by hand. Any eccentricity will become apparent. That eccentricity invalidates the readings established by Bill's test.

H
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dml66
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Re: What is "Work Tolerance"?

Post by dml66 »

I ordered a 12" piece of tight-tolerance tool steel rod from McMaster-Carr. I chose 5/8" diameter since that's the largest diameter that will pass though the spindle. The rod is held to +/- 0.001" diameter tolerance, 0.005" per foot straightness tolerance.

Whether I use the ER-32 collet chuck, or the 3-jaw, I plan to grasp the rod in it's middle so that half is inside the spindle, half outside, that should assure gravity doesn't want to tilt the rod while it's being chucked.

At this point, I don't feel confident I can use something made by this lathe to figure what's wrong with it, and if it's fixable. Some of that confidence shortage is the result of my own skill level, or lack thereof. Maybe I'm on the wrong diagnostic track but, if the rod meets or exceeds it's own specifications, and I'd be satisfied if I could make that rod with this lathe, using it to indicate seems like a good idea. If it's useless, it won't be the first $10 I've wasted 😒.
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Bill Shields
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Re: What is "Work Tolerance"?

Post by Bill Shields »

I would hope that if someone that is as worried about tolerance would be able to indicate a rod in a 4 jaw chuck and drill a center in each end 😀

If that feat cannot be accomplished then all of us are playing ring around the Rosie
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