Carriage Feeds?

[Tamper84]

I have been searching for a lathe, and an Atlas/Craftsman lathe may end up in my shop depending on what I can find locally. I have been watching Tubal Cains videos, he has said that the slowest feed on them is still too fast. Is that true? Does anyone use any of the faster feeds?

Thanks,
Chris

 

[PurpLev]

I think mostly people refer to lathe model running too fast (spindle speed), or more correctly - not having slow enough spindle speed for threading/reaming operations where you want to go real slow (under 100rpm) to prevent mishaps on the workpiece, or to the cutter (reamers).

this is something that is definitely worth checking on a lathe you are about to purchase, having a spindle speed option (with or without back gear) that can get you below 100rpm is a good thing to have.

in reference to feed rates, I think having something with a .005 and less for feed would be OK. the closer it can get to .001 the better finish obviously.

 

[Tamper84]

Thank you! From what I can find the slowest feed for the carriage is .004. Which does seem pretty fast. But then again, I dont have that much experience with any machine tools.:whistle:

Thanks,
Chris

 

[PurpLev]

.004 seems on the 'fast' end of things when it comes to finishing feed speeds, but depending on what you'll use with the lathe, this might just be OK. my previous lathe best was .005, and while the finish cut wasn't close to a ground finish (nor should it be) if you grind your cutter with a large enough radius, and/or use a surface grinder attachment you could still produce some nice finish cuts on it.

 

[Smudgemo]

I'm pretty sure I know which video you are referencing, and I'm fairly certain it was indeed in reference to the 12x36 carriage speed being too fast. He had hooked up an aux motor to drive the screw (while in neutral) at a slower speed than available from the machine itself. My 12x36 will run down to 28 rpm in back drive and .0042 for the carriage feed, and I can only assume his is the same. I haven't used this lathe a ton yet, but when I'm not threading (like in the photo) I seem to usually be at the very slowest end of the gear box, so he's probably spot-on.



-Ryan

 

[Tamper84]

Its hard to tell what I would do. But my primary goal is to build a live steam locomotive. The rpm range is good with me, its just the carriage feed rates I was wondering about. Hmmm, I could probably get an old wire feeder from work and make a variable speed lead screw like he did. :thinking:. But alas, I dont have a lathe yet lol

Thanks,
Chris

 

[Tamper84]

Here is a video where he talks about it.

[video=youtube_share;3DlPDr4f6xQ]http://youtu.be/3DlPDr4f6xQ[/video]

Thanks,
Chris

 

[rdhem2]

Might seem contrary but just by fooling around my experience is slow carriage feed is not always the answer to a good finish cut. I have found that stepping up the chuck rpm's a mite, give the carriage feed a little boost in rate, use a fine, not over .004" cut and a WELL formed, SHARP HSS tool with a little cutting fluid of choice and I can get a nice soft satin finish pretty much on demand.

When the day comes to sit and ponder the many wonders and secrets, chuck up a piece of scrap and experiment. Amazing the little unknowns that just run out on to the floor if you don't have a box to catch them all in! Translation: You can learn alot if you are not worried about messing up a 98% finished piece of work, and just go to cutting with only final finish in mind. This is how I figure out a lot of things on my own. Makes me look well, real smart sometimes! :thinking:

 

[Dranreb]

On my 10F, while changing the gears to do limited metric metric screw cutting (as per Lathes.co.uk ) I had to relieve the edge of the (AchornTools) QCGB casing a tad for clearance for the larger gear. When I had done that I noticed that if I relieved a bit more, I could move the banjo up enough to get a smaller gear to engage the tumbler gear and get a slower feed than the QCGB does as standard. Haven't used it for awhile or done the maths but if it is of interest I could take some pix and check the gear teeth numbers.