Shimming an Atlas lathe bed

graham-xrf said:
Please forgive that get sidetracked here, but what I get from your picture is..
.. is that a bookcase, and a Hi-Fi speaker, and carpets??

For a minute there, I thought you might be the kind of hero who sets up his machine in his lounge living room, or maybe has turned his shop into a multi-purpose living space, but then I see the wall blocks behind the motor, and the surface plate gauges near what looks like a W2AXZ QSL card!
:)
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LOL... that is our unfinished basement. My wife lets me have it to myself because there are some spiders. I discovered that when we shut off the lights their eyes will glow for a few seconds. I showed this phenomenon to my wife and the basement has been all mine ever since. It serves as study, machine shop, woodworking shop, electronics shop, ham radio shack and billiards room. W2ANZ is my call sign, but the card on display is from 1941 from the previous assignee of the call.
 
FOMOGO said:
Much of what your seeing is probably in the chuck it self. Mike
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I did mention in post #3 that getting into this kind of measuring checkout should be done between centres because "Chucks have their own separate alignment and run-out issues". Jon has no problem when turning between centres.

He was getting 0.005" and then 0.001" taper along only a few inches. I am thinking that is surely too much, but I my expectations may be too stringent. I don't know what is generally "normal" for these. Pierre @pdentrem has mentioned that Jon might be chasing wear, and also that his own lathe placed on the heavy wooden table needed leveling adjustment as seasons passed. This would presumably be because of the table changing underneath with the seasons.

I know this is Jon's lathe over which we are indulging in "armchair diagnosis", but I am finding the thread useful as well. Getting the bed set down without twist from end to end is the first and most basic step. Since there is no problem turning between centres, then it is the chuck that needs scrutiny. Turning a convex when facing is logically a cross slide problem. It might be gib adjustment setup.
 
I will mention two significant differences between all of the the Atlas 10" and all of the 3/8" bed Atlas-Craftsman 12" (as shipped from the factory). The 10" countershaft is mounted to the stand or table behind the bed whereas the countershaft on the 3/8" bed 12" is mounted on the rear of the bed. And the right leg on the 10" has two mounting holes to the the stand like the left one whereas the right leg on the early 12" has only one. I mention this as it isn't perhaps a well-known difference and to keep someone familiar with only one of the two machines from discounting the rest of someones post because of the perceived description error.
 
wa5cab said:
I will mention two significant differences between all of the the Atlas 10" and all of the 3/8" bed Atlas-Craftsman 12" (as shipped from the factory). The 10" countershaft is mounted to the stand or table behind the bed whereas the countershaft on the 3/8" bed 12" is mounted on the rear of the bed. And the right leg on the 10" has two mounting holes to the the stand like the left one whereas the right leg on the early 12" has only one. I mention this as it isn't perhaps a well-known difference and to keep someone familiar with only one of the two machines from discounting the rest of someones post because of the perceived description error.
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It seems counter-intuitive that the (smaller?) 10" puts the weight of the drive assembly onto the table behind, and the (bigger?) 12" supports it all off the bed structure. Did I get that wrong? Jon has not mentioned which is his.

From the size of what might be an ER32 collet in the picture, I might take a guess how much room there is from axis to the ways, but clearly, the whole drive is on the lathe structure. Thank you. I just knew there would be folk here fully knowledgeable about Atlas machines. :)
 
The countershaft can be above, vertical version, or behind like the OP has, horizontal. My lathe in photo is a vertical countershaft.
Pierre
 
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my th42 (10") motor is mounted to the table, not the bed:

fr_3846.jpg

It's also a "wee" bit bigger than the orginal. I run a Baldor 3/4 hp dc motor.
 
My lathe is a 12". It has 3/8" ways and three mounting holes - two at the headstock end and just one on the right side. The motor and counter-shaft are attached to the bed as shown in post #6. And yes, this does seem wrong. Common sense would be that the 12" lathe should have a more robust means of supporting the motor and counter-shaft than the 10" lathe, but that is not what Atlas did.

Atlas may have over-economized with my lathe (circa 1954). I believe (Robert, please correct me if necessary) that later models had 1/2" ways.
 
I did a test cut earlier today. I faced a 3.5" disk of 6061. The cut is not convex or concave - it is very close to flat. I need to repeat the cut with a better surface finish in order to tell better. This is an improvement from the situation prior to shimming. Prior to shimming my facing cuts were slightly convex - perhaps by .001 or .002 on a 3.5" diameter.

I'm not pleased with the shimming that I did. I suspect I have just treated the symptoms at a particular distance from the headstock and I have not fixed the root cause. Pdentrem may be correct - part of the issue may be bed wear. But I still feel that the motor arrangement and flexibility of the bed are contributors.

I would very much like to hear from others with 3/8" ways with motor and counter-shaft hung from the bed. Do you have a similar issue? If so, what have you done to correct it?
 
Do you have a face plate?
I would stick an indicator on the cross slide and check that the slide is parallel to the face plate. Lock down the carriage so that it does not move. Hopefully the face plate or the largest chuck face is flat! Do it twice, once and then rotate the face plate 180 degrees and do it again. Chart the readings and do an average of the two readings at set points as you move across the surface. This will remove error in the face plate.
Another test is I would take readings of the thickness of the ways at the outside edge closest to you from the head stock and tail stock areas. The wear will show easily if there. Mine had .010” in the first 10” after that it swiftly reduced to about zero which matched the thickness at the tail stock end. The effect when turning is measurable as the tool drops below center line. Math is involved of course!
Pierre
 
BTW on my 10” lathe, I did nothing about how the motor was mounted. The motor was replaced at some time in history with a heavier 3/4 hp as well.
Pierre
 
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