New Lathe...Changed from PM 1127-VF To a PM1236

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Hi guys,

I have a question about setting up the lathe and leveling it.

The lathe is supported by two pillars, each pillar being supported by four leveling feet.
So how do you make sure each pillar is evenly supported by the four leveling screws ?

While leveling the lathe, how do you know if you should touch-up the inner or the outer adjusting feet ?

If the feet are really unevenly supported, one foot will stop touching the ground. But before that happens, probably the pillar can allow some twisting and I'm juste guessing while doing so not providing the most firm and rigid support the the lathe.
 
tino_ale said:
While leveling the lathe, how do you know if you should touch-up the inner or the outer adjusting feet ?
Click to expand...

You will "feel" the pressure being fairly even (we are talking about 1200+ pounds), so you "will" know if you have adjusting feet that are not doing anything. As to how to fine tweak them to get level? You know by alternating the machinist level to sit along the bed and also across the bed, at two points: near the headstock and the end of the bed (where the tailstock usually rests while it is not being used. Keep in mind that eliminating (minimizing) twist is the more critical thing - the lathe does not have to sit perfectly level to work accurately, as long as the twist is minimized.

And after you do all that, you probably have to re-do it after a few weeks/months as the mounts settle/compress with time. It is a pain in the but to do, but necessary for accurate work 😉

Will
 
I ended up only using 4 leveling feet on the inboard side of the stands. I welded up a frame for both stands to put my feet on the outside of the stands. Worked out great. I was able to get to within .0002" of level/twist and cut evenly. Taking the twist out ended up shifting the gap a little and I had to pull the pins and move the gap about .001" to get the vee way to line up. Also you don't have to use a .0002"/10" level either. I started out with a Starret #98 machinist level and and then went to my china precision level and it was good enough. (to say china and precision in the same sentence is just wrong) I did try to get that last .0002" out but their is to much twist and I'm pulling the other side's foot of the floor. I have to shim the lathe base to get any more out of it.
 
Many later lathes use only 4 or 6 holes for mounting. The PM1236 has 8. Drove me crazy the first time I tried to level it using all 8 feet. Later on I replaced the inner four with solid mounts. Post 187

I use the solid mounts for leveling & the rubber feet on the outside to prevent the lathe from moving. Much easier to level & no need to readjust since it does not need to "settle". Since then I've replaced the outer feet with larger diameter mounts.
 
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Interesting approach in your post 187, leveling the lathe with the four inner feet only then using the outer feet only to touch and lift as little as one thou. Do you think one thou is enough to actually provide support or is the lathe basically resting on four feet only ?

About bed twist, I have one more question.
I understand a twist-less bed is important to avoid unwanted tapper when machining a long part. On the other hand a bed that has ZERO twist while resting cannot have zero twist while machining a part. It's against nature. While machining there are twisting forces applied to the bed, so no matter how rigid it is, some minor twist must occur (I guess ?).
For this reason I was wondering if a "twist offset" approach could be used ? Meaning the bed would be lightly twisted while resting, in order to come right in alignment (or as close as it gets) while machining.

Just a thought but that might not actually be practical or realistic ?
 
tino_ale said:
On the other hand a bed that has ZERO twist while resting cannot have zero twist while machining a part. It's against nature. While machining there are twisting forces applied to the bed, so no matter how rigid it is, some minor twist must occur (I guess ?).
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Absolutely. You will always have some amount of deflection, proportional to the forces involved. That is inevitable, but as the machine gets bigger and heavier, with better materials, a single piece base made of cast iron, better bearings, higher tolerances, etc., the amount of flex becomes smaller. This is precisely why I went away from the 7x lathe I started with to the heavier/sturdier 8x lathe, and then quickly to my current 12x "class" machine - because I was after a more rigid/firm platform. All of this still does not negate starting with a balanced and twist-less bed - that still has to be the starting point, regardless of the machine being used.

In fact, after a couple of years with the 12x, as I get more experienced, now I feel the 12x is not adequate - I would like to have a 3000+ pound lathe instead, a heavy 13 or 14 class lathe. Since I don't have the money for such a machine, I have been thinking about ways to make my 12x stiffer - I have mentioned before ideas about making steel beams to interconnect the two bases, filling the two bases with concrete, bolting the bases to the ground, etc.. - all of these things improve the stiffness of the machine, and are cheaper than a heavy 13/14 machine 😀

Will
 
Re: Seriously...My New Lathe...PM 1127-VF - NOT ANYMORE...

You will always have some amount of deflection, proportional to the forces involved. That is inevitable,
Click to expand...
Actually it is not 🙂

Take a look at this recent article from MMS about a machine tool that develops stiffness rated at infinity. Made to machine titanium, no surprise there.

http://www.mmsonline.com/articles/a-model-machine-for-titanium
 
wquiles said:
...snip...
In fact, after a couple of years with the 12x, as I get more experienced, now I feel the 12x is not adequate...snip...
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Heh - I have what is probably the heaviest duty Craftsman (read Atlas) 12" lathe (the short bed under drive cabinet base), but Atlas/Craftsman is probably one of the lightest duty lathes in it's size. I've resently been using a Southbend Heavy 10, and even nicer, a 13" or so Sheldon.

Anyway, it's brought back my dream of a heavier lathe, and I think it really IS going to happen this time. Yeah, it's limited to 11" swing, and only 18" between centers, but I really think an HLVH will follow me home sometime this year. Now how do I move a 1800 lb 11x18 lathe down the stairs
 
Thinking about getting one also. Would you buy it again?

Has anything broken or worn out yet?

Thanks,
Gary
 
gkemper said:
Thinking about getting one also. Would you buy it again?

Has anything broken or worn out yet?

Thanks,
Gary
Click to expand...

For the price, yes I would buy again (even though the price for the lathe & shipping is more now). I haven't had any issues that required me to buy a replacement part for it. Everything thing was just upgrading or adding on to it. And buying from Matt couldn't have been a better experience for me for both the lathe & mill.
 
darkzero said:
For the price, yes I would buy again (even though the price for the lathe & shipping is more now). I haven't had any issues that required me to buy a replacement part for it. Everything thing was just upgrading or adding on to it. And buying from Matt couldn't have been a better experience for me for both the lathe & mill.
Click to expand...

Thanks. That makes me feel a lot better. I just put a down payment on one.

Where did you buy your Sino DRO? Do you remember how much is was?

Gary
 
gkemper said:
Thanks. That makes me feel a lot better. I just put a down payment on one.

Where did you buy your Sino DRO? Do you remember how much is was?

Gary
Click to expand...

I don't have a Sino DRO & I did not get my DRO "unit" from Matt. I pieced my DRO system together, I only have Sino scales. I forget what I ended up paying in the end but it was under $500 total & I did the installation myself which is in post #196 in this thread.


Once again Matt has taken good care of me! I wasn't planning on getting a DRO for sometime for the mill but Matt gave me an unbelievable price for the 3 axis DRO that was taken of my mill. I'd be stupid to pass up on the offer so I got it. I was planning on getting something else & I still will but at least this way it will save me installation time since everything should bolt right back on & all I have to do is upgrade the display later.

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Thanks to Bob & a member of another forum for the reminder, I got me a 1μm scale for my cross slide too.

Easson doesn't make the size I need so I got one a Sino from the guy I get my DRO stuff from in China. Better for me anyway so I won't need any additional work mounting it, simply unbolted the old scale & bolted the new one onto the mount.

Not much to see since the scale doesn't look any different but I'll post some pics anyway.


1μm on top.
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Pic of the X scale mount that I missed in my DRO installation post.
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With .0001" resolution I'm not crazy to think I can actually try to achieve that level of tolerance, especially with this lathe, but it will help make things just ever so slightly easier. 🙂
 
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I find having the .0001 cross slide scale helps me tremendously when going for those "almost press fit" parts. I find it fairly easy to end up with two parts that smoothly slide together as air pressure builds up inside and slowly escapes around the OD of the smaller part. I had to bore a few thousandths from a piece of Garolite G11 fiberglass so that a 5/8" stainless ball would fit with no slop but no resistance. I ended up being able to hold the tube vertical, finger plugging the bottom, dropping the ball in the top and having it slowly ride the air cushion down.
 
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