Craftsman/Atlas speed controls

[jagwinn]

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Hello,
1975 Craftsman/Atlas. I cannot set up to run the carriage feed speed anything different that the spindle speed.
I move the selection levers according to the chart, but the speed is always matched to the spindle speed, regardless of the speed I run the spindle.

The backgear selection lever, when pulled out, locks the machine up...the belts squeal and I cannot rotate the chuck by hand.

Any help on these two agrivations??

Thanks in advance,
John

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[steamer]

John,

The Cross feed is usually 1/4 the carriage feed and is not adjustable as they are geared together.

You need to pull the pin back on the front of the headstock to use the back gear or it will be locked.....that isn't a problem, but how the system works.

I mean this sincerely...
I would get the book " How to run a lathe" by Southbend and read up before you do some damage to yourself or your lathe.....
Check our downloads section for a book by Hercus that is very similar. and it's free...
Heres the link...

http://www.homemodelenginemachinist.com/index.php?action=tpmod;dl=get148

Dave

 

[joeby]

John,

Your first question confuses me a bit. The quick change gearbox changes the gear ratio between the spindle and leadscrew, as it is geared directly from the outboard end of the spindle, it is always "tied" to the spindle rpm. Therefore, if you set the gearbox for 20 TPI (.05" per revolution) it will maintain that ratio regardless of spindle speed.

Perhaps you were thinking it should work independently of the spindle as a Hardinge lathe, but these lathes had a separate feed motor for turning and used gearing for threading, two independent systems.

As for the back gearing, the bull gear (large gear immediately to the right of the spindle pulleys) has a pin on the right side of it that must be pulled out (toward chuck) to disengage the bull gear from the cone pulley, then the back gear is engaged and it should turn but with some effort. To disengage back gear, return the lever to direct drive, loosen the drive belt and turn the spindle so the locking pin is accessible. Holding the bull gear, turn the cone pulleys while pushing in on the pin. It should snap into place when the two parts are aligned properly.

Kevin

 

[black85vette]

When you say it "matches" the speed of the spindle do you mean it speeds up and slows down with the spindle or it turns exactly 1:1 the same speed as the spindle? Since the shaft is driven off the spindle through a set of gears it will always be proportional to the spindle speed. This allows you to cut threads.

I assume from your description that you have the quick change gear box, is that correct?

Regarding the back gears: On the bull gear, the largest and right behind the chuck. Rotate it around and look for a pin that you can pull back and disengage it from the pulley behind it. When you select the back gear lever you also have to pull that pin out.

Which lathe do you have? 10" or 12"'?

 

[jagwinn]

Thank you for the replies!

I turned some CR and the result was a finish like fine thread. I asked a machinist at work and he said run the spindle fast and the feed slow.

That is what lead me to look for a difference in speeds. The result is I get the exact same finish with any speed I select, and it 'appears' to me that there is no difference with any setting of the quick change levers.

The machne is a 12" Craftsman Commercial.

I have located the locking pin, thanks.

 

[joeby]

The left-hand lever on the quick change is A-E, correct. Left-hand lever in position E and right hand lever to the far right is as slow as you can go, I think.

It is entirely possible that the end gearing (between spindle and QC gearbox) has been changed.

Do you have the operators manual?

Kevin

 

[black85vette]

I have the same lathe. I can scan the page with the gearing set up or take a picture of it.

Try leaving the spindle at one speed and then set the quick change to A-1. Engage the carriage and time it over a couple of inches. Then move the setting to E-9 and time it over the same distance and let us know how they compare.

 

[jagwinn]

Thank you for the offer, but I have the original manual for the lathe!

Black85vette: I think your idea has showed me the error of my ways! I wasn't understanding what I was seeing.

Distance: 3.75in; levers set to E-1; time to travel distance was 15sec.
Distance: 3.75in; levers set to E-9; time to travel distance was 35sec.

Thank you for getting me thus far, I think I can make it work now.

Thank you for all that replied,
John

 

[steamer]

John,

I am glad you have the manual. Please take some time and read it carefully, the Atlas manual was very well written, it will tell you all that you need to know about your lathe.

Dave

 

[black85vette]

There were two "manuals" for these machines. The first was called the "Operating Instructions and Parts List" and was 8 1/2 x 11 and about 12 pages. The other was a black 5 x 8 1/2 format in a black leather-like cover called "Manual of Lathe Operation and Machinists Tables". That one is over 200 pages and is excellent. The first has the basic unpack / setup information and parts list but not much about how to run the lathe.

Do you have both of these?

 

[jagwinn]

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Yes, I have both manuals. In excitement, I jumped right in instead of testing the water. Thanks for the help...will keep posted when I can turn a smooth finish (still not there on that).

John

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[black85vette]

Hang in there. There is a lot of good wisdom on this board on how to do things. The lathe you have is a good one (I have some bias there) and capable of doing nice work. One of the nice things about this board is that you can use small engines as projects to learn new skills as you need them and you have common ground with others who enjoy building and helping others.

 

[JimM]

I also have an Atlas lathe, although I have the poor mans version without the quick change box. I also turn out work with a fine thread but this is down to my lack of skill and not the lathe

Are you using tipped tools or HSS, if the latter try putting a small radius on the tip of the tool. Also rather than feeding under power try using the hand wheel, you can then vary the speed on the same cut to see what affect different feed speeds make to the finish. One last thing is to use a known grade of stock, I started off testing on pieces of scrap with very poor results, when I got a piece of decent steel to experiment with the improvement was immediately obvious - not perfect but definitely better

Cheers

Jim