A Large Project For My 12" Atlas Lathe

[Provincial]

I needed to deepen the grooves in a hydraulic cylinder piston for a log loader. The cylinder bore had been honed oversize, so the piston measures 7.025" and it really maxed out the capacity of the lathe. To get the compound to clear, I had to turn it 90 degrees to the cross slide, and also move the AXA toolpost as far away from the spindle axis as possible. This resulted in poor rigidity. The piston is made of aluminum, which helped a lot, but I had to take it easy in order to minimize chatter. I held the piston in my 6" Buck Adjust-Tru 3-jaw with the jaws reversed. It was pushing the capacity of the chuck!

I used my parting tool with a HSS blade for all operations. I had to fight chatter when plunging to get the cut started, and ran the spindle at 164 RPM for all cuts. I was reducing the diameter of the bottom of the groove from 6.525 to 6.275" to accommodate a replacement seal, since the original cross-section seals are no longer available. I plunged to 6.325" and then made a series of plunge cuts, dialing in .100 on the cross-feed. Each plunge cut was about 1/3 the width of the tool. I encountered chatter if I tried to take a bigger bite. I hand-fed across the bottom of the groove and blended the cut to the existing sides of the groove. I followed this up by repeating the process twice. Once to get within .005 of the finished size, and again to the finish diameter. Each time I did a plunge cut, it was in an area where the seal lip would not contact, in case I got a rough finish. I hand-fed every cut, and got a nice finish every time. All cuts were done dry.

I had to flip the piston end-for-end to cut the second groove, but I had dialed in the Buck and did not have to change the setting. It took a long time to do this, but it was a favor for a neighbor, and I was not on the clock!

The lathe is one of the last ones made by Atlas, and was saved from a scrap metal yard when the Bureau of Indian Affairs disposed of it. When I got it , I could not close the half nuts because the lead screw was still coated with Cosmoline!

 

[wa5cab]

Provincial.

For many years I've maintained a database of Atlas, AA and Atlas-Craftsman machines here and on Atlas-Craftsman@groups.io. My 3996 has always had the highest reported serial number @ 106781. What is yours? And what model?

Largest thing that I recall boring on it were Land Rover 10" brake drums. Tried to do 11" ones but they were too large (I once owned an 88 and two Diesel 109's).

 

[maspann]

Provincial.

For many years I've maintained a database of Atlas, AA and Atlas-Craftsman machines here and on Atlas-Craftsman@groups.io. My 3996 has always had the highest reported serial number @ 106781. What is yours? And what model?

Largest thing that I recall boring on it were Land Rover 10" brake drums. Tried to do 11" ones but they were too large (I once owned an 88 and two Diesel 109's).

Robert, just a FYI I have an 12" Atlas. Model 3996, Serial 105153. Its in excellent shape, no bed wear and I have recently changed the cross slide nut and half nuts.

 

[kcoffield]

When I cast and machined the pulleys for my lathe, I used a similar approach........at 9" turning diameter. Easy does it!

Atlas/Craftsman Lathe Motor and Countershaft Pulleys

Randy, please let us know if Clausing still has the pulley. Kelly, please post photos of your setup when you machine the large pulley casting. I could not think of a way to do it myself, but I am not very creative. And yes, if you machine it yourself as you describe it should run true. I...

www.hobby-machinist.com

Best,
Kelly

 

[Provincial]

wa5cab, my Atlas 12" is a model 12700, serial number 106412. I also have a QC42, serial number 001692.

 

[wa5cab]

OK. What State do you actually live in?

From the examples that we have, it would appear that the 3995, 3996 and 12700 must have shared the same S/N pool. The actual lathe in each, except that the 3995 was a 12x24, is the same. I read somewhere that the 12700's were intended for schools. On the 12700 Both the motor compartment and the countershaft compartment are lockable. Whereas on the other two, the countershaft and belt just has a swinging cover.

Confirm that on your QC42, the FWD/OFF/REV selector lever has a spring-loaded pin instead of a clamping bolt.

 

[Provincial]

My QC42 has a spring-loaded pin in the selector lever.

My 12700 is a 12x36 and came from the Chemawa Indian School near Salem, Oregon. That school is run by the US Department of the Interior, Bureau of Indian Affairs. You can see that from the label I posted. It is indeed the school model, with the thick ways. It came with a 3-phase 1/2-hp motor and reversing switch. lathes.co.uk/atlas/ has a brief description of this model.

I live in Oregon, near Salem. When I signed up here, I put that information on the questionnaire thinking it was for management use only. I wanted to explain why my location varies when advertisers send me targeted ads because Centurylink sends my internet traffic out of their phone system at various spots. Probably where the traffic is least congested. This can be anywhere from Vancouver, Washington to Redmond, Oregon, but mostly Portland, Oregon. I'll have to contact administration and get that changed, but it is low on my list of things to do.

 

[Orangetruckman]

That dang chatter monster just shows up in the worst places sometimes. Way to stick with it and accomplish your favor! That’s a nice looking machine. People just don’t know what they have sometimes, but lucky for you then. And hello from a neighbor of sorts, as I live in the Portland area.

 

[Alcap]

What type of seal did you end up getting ?Years ago I had to machine two pistons on a old backhoe that used Chevron style .

 

[Provincial]

Single lip U-cup seals. Pretty common, with no 0-ring expander. I had to use a 1/8" nylon back-up ring because the original grooves were too wide.