Dumb Question

T

tinnerjohn

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A couple questions about using my Atlas 612. When reversing the lead screw, should the power be disengaged? Second, can the cuts be made in both directions or is it better to cut toward the headstock only? I haven't used the lathe much yet, made some bushings and a speed reducer for my Dunlap drill press, but I've got a lot ideas on the back burner waiting for some free time and extra cash! Thanks,
John
 
Yes, stop the spindle before reversing feed, trying to shift with it running is how gears are broken.
Its best to cut toward the chuck. having said that there are times you have to cut away from it, so yes, it can be done.
 
Like Tom said, yes, stop the spindle before changing the direction of the lead screw.

As for cutting in both directions, I never do simply because I can disengage the power feed and return the carriage to the other end using the hand wheel. I am ready to start a new cut faster that way than stopping the lathe to reverse the lead screw. Additionally, if you are using a tool set up for a left handed cut, it doesn't work too well going the other way. The only time I make right handed cuts is when I am working up to a shoulder or something similar that requires it.

I almost forgot... there is no such thing as a dumb question. Your question was quite valid and it has been asked before, proving that it has been on the minds of more than one person. Getting an answer helped you to learn the proper way to do something, plus half a dozen or more other members learned from it as well. That is what this place is all about!

Thank you for taking the time to post your question!

:clapping:
 
Thank you very much, both of you. These are two things I hadn't found answers to in the printed material I've found. Stopping the spindle seemed like the proper technique, just like using a clutch, but I've also heard of being able to shift a tranny without using the clutch, so I thought I'd ask. I tried to "power shift" the lathe once, but I prefer not to "grind coffee" with a geartrain. I also know the only "dumb question" is the one that isn't asked, especially if it results in personal or property damage. I haven't posted much on here, but the info I have gained is priceless to me. Thanks to everyone for a great forum!

John
 
tinnerjohn said:
Stopping the spindle seemed like the proper technique, just like using a clutch, but I've also heard of being able to shift a tranny without using the clutch, so I thought I'd ask.
Click to expand...

Yes, you can shift a manual transmission without the clutch, I do it all the time, BUT semi-truck transmissions are built way differently than manual car transmissions. Shifting gears in a car or pickup transmission without the clutch induces lots of extra wear on the synchronizer rings. Additionally, we're never trying to reverse directions without coming to a complete stop first. Clutchless shifts are always done while moving in the same direction.
 
To add a couple of additional reasons for normally cutting toward the headstock, the headstock and its spindle bearings will handle safely considerably more end and side load compared to the tailstock and live center bearings. Think of the relative size of the headstock and its spindle bearings compared to the tailstock and the live center bearings. And especially if using a QCTP, it is usually mounted so as to maximize stiffness or minimize reaction and to maximize clearance when cutting to the left. Cutting toward the tailstock on my machine takes 10 to 15 minutes of setup time. Plus almost as long to reverse directions again.
 
Terry, Very good point. But you did give me a good chuckle with the thought of the noise going from even granny to rev would make, and the reaction of the mechanic when he tore into that tranny. I have known some drivers that would try that though. BTW, I've ground my share of gears over the years, on straight trucks though. I thought about driving a semi when I was younger, then I came to my senses! Too many nuts loose on the road to want that responsibility. John
 
There will be times to cut away from the chuck. When doing that you must make sure the part is held securely in the chuck and if possible use the tail stock to help hold the part in position. I have done this many times when cutting left hand threads or the back side of shoulder with no problems.
 
I am about to cut away from the chuck on a pulley that I am making. This discussion may have saved me from ruining my part. Thank you!
 
One other reason on some lathes to only cut toward the tailstock when you really need to is that on babbit and sleeve bearing lathes, in addition to the two spindle bearings, you also have one thrust bearing. The thrust bearing only works in one direction. Thrust toward the tailstock is only taken by the tailstock and live center (if you are using them) or by whatever there is on the left end of the spindle that keeps the spindle from coming through the left bearing.

On the Atlas 10" and Craftsman 12" babbit bearing lathes, this is I think the 9-78 Spacer rubbing against the left face of the 10-4 bearing cap and Headstock.

On the 101.07301 I think it would be the L9-78 Spindle Gear Spacer rubbing against the left end of the Headstock (although the flat parts photo does show the Spindle Gear and Spacer in the other order).

Would some 07301 owner please confirm that the Spacer is between the Gear and the Headstock?
 
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