Thread: metal lathe feed rate questions

Stuart,thats correct I was just throwing different thoughts about.

Generally the smaller the Stud and bigger the Screw the greater the reduction,resulting in a finer feed.

Peter,the photos you provided dont seem to relate to very much,inregards to what the feeds are.

The photo of the Metric pitches show the use of the 127/120 compound,as they are shown in your photo the compound is not being used,it is only functioning as an idler.

The chart on your quickchange would indicate that the lathe has an Imperial leadscrew,is there a diagram on the lathe showing the position of the change gears for imperial threads and feeds.If there is this should show the Stud and Screw gear running through the same gear on the compound,this gear will act as an idler,it dosent really matter if it was the 127 or 120 as it wont effect the ratio between the Stud and Screw gear.

i wonder ...... are you using the screw cutting feed or if theres a clutch feed maybe the lever below the dial when i first got my hercus i had this problem till i read the manual,
john

Peter

There are various grades of brass, steel and aluminium . The free turning grades are the type to look for . The free turning brass stock that I turned had a beautiful finish , I just used ordinary mild steel raking on the HSS tools. The non-free turning grades are more fussy about having the correct tool raking and speeds and feeds . MIKE. Looks like a nice lathe you have BTW

Originally Posted by tanii51

i wonder ...... are you using the screw cutting feed or if theres a clutch feed maybe the lever below the dial when i first got my hercus i had this problem till i read the manual,
john

Hi John and all.
I use the Clutch feed not the screw cutting feed .
the quick changing gears do affect this feeding . so i'm not sure how this machine setting combine the two feeding or is it not . if it not then where is the setting for the auto feeding ? . I don't have the manual for this lathe so a little confuse .
I will take couple more pictures about the Clutch feed section

cheers all
Peter

Hi Peter,
There is a keyway running the length of your leadscrew? Thats where the drive for the power feed comes from.
Screw cutting the halfnuts grip the leadscrew and are dragged along it.
Power feed the keyway drives a gear that drives either the crossfeed screw or the carriage rack wheel.
Also as you are in powerfeed gear the tables on your lathe wont be correct in absolute terms. So while E2 will be your slowest feed it wont be 112 tpi(assuming that you had the correct change gears on for that anyway)

Does that all make sense? (I hope its all correct)

Stuart

The lever on the front of the gearbox, that flips left or right, selects the leadscrew for threading or the feedshaft for feeds.

BTW the lathe is a rebadged Lantaine. There's a manual floating around if you want to google for it.

Originally Posted by Bryan

The lever on the front of the gearbox, that flips left or right, selects the leadscrew for threading or the feedshaft for feeds.

BTW the lathe is a rebadged Lantaine. There's a manual floating around if you want to google for it.

That is it Bryan.
just like you described . I will try to look for it manual.

Thanks for this
Peter

Hi Peter
Sorry for the bad guess on my part.

Stuart

p.s. thank Bryan

Originally Posted by Stustoys

Hi Peter,
There is a keyway running the length of your leadscrew? Thats where the drive for the power feed comes from.
Screw cutting the halfnuts grip the leadscrew and are dragged along it.
Power feed the keyway drives a gear that drives either the crossfeed screw or the carriage rack wheel.
Also as you are in powerfeed gear the tables on your lathe wont be correct in absolute terms. So while E2 will be your slowest feed it wont be 112 tpi(assuming that you had the correct change gears on for that anyway)

Does that all make sense? (I hope its all correct)

Stuart

Hi Stuart.
I found the manual online as Bryan find out this is the same machine as mine .
http://www.bbssystem.com/manuals/Pre...structions.pdf


Cheers
Peter

Originally Posted by thorens

Hi Stuart and PC.
I have just set it up on E/8 . look like it work good . much better finish on the surface .
however I may have another problem which is the run out of the chuck. I'm testing the cut on the brass bar . it stick out from the chuck about 70mm and cutting is about 50mm and I found in every 10mm cut I have about 2~3 thouds out . look like this.
17.50mm first 10mm and 17.47mm the next and then 17.44 or so in the next 10mm of cut.
is there anything's we can do on this run out ?

Thanks
Peter

On a piece 20mm in diameter, with 70mm hanging out I'd definitely be thinking deflection myself, assuming of course your biggest diameter is measured at the unsupported end. Got a steady or a centre you could use, see if things improve? Or even some bigger diameter stock would help you check this option, maybe something around 50-60mm sticking out the same 70mm...

If your readings are have the bigger diameter to the chuck end however, the more likely option, especially given you've just installed the lathe, is twist in the bed, although I don't know whether you'd notice it to that extent on such a short distance - I suppose it depends on how twisted it is. Someone else will have to comment on that, but in the meantime, I'll just float the perennial question - have you levelled the lathe?

Thorens,

Any chance you're using an incorrect tool while trying to get a surface finish?

I'm willing to stand corrected, but a finishing tool has a rounded nose while a cutting tool has a sharpish straight edge (my words) and using the cutting tool will always leave a trail of small spirals.

Cheers,

Originally Posted by Jekyll and Hyde

On a piece 20mm in diameter, with 70mm hanging out I'd definitely be thinking deflection myself, assuming of course your biggest diameter is measured at the unsupported end. Got a steady or a centre you could use, see if things improve? Or even some bigger diameter stock would help you check this option, maybe something around 50-60mm sticking out the same 70mm...

If your readings are have the bigger diameter to the chuck end however, the more likely option, especially given you've just installed the lathe, is twist in the bed, although I don't know whether you'd notice it to that extent on such a short distance - I suppose it depends on how twisted it is. Someone else will have to comment on that, but in the meantime, I'll just float the perennial question - have you levelled the lathe?

Hi JH.
I have found out why I have so much run out now. it is a twist in the bed like you said . I'm adjusting it now , so far so good , at the moment it is 2.5 thouds run out on the same bar .
I don't think i can get any better but will keep trying untill i happy .
Cheers all
Peter

Originally Posted by thorens

Hi JH.
I have found out why I have so much run out now. it is a twist in the bed like you said . I'm adjusting it now , so far so good , at the moment it is 2.5 thouds run out on the same bar .
I don't think i can get any better but will keep trying untill i happy .
Cheers all
Peter

Out of curiousity, what are you leveling it with? Carpenters level, or a machinists level (otherwise known to me as the most frustrating device ever invented!). If you are in pursuit of the best possible accuracy, a machinists level should help to get that last bit (assuming you're not already using one).

Originally Posted by Jekyll and Hyde

Out of curiousity, what are you leveling it with? Carpenters level, or a machinists level (otherwise known to me as the most frustrating device ever invented!). If you are in pursuit of the best possible accuracy, a machinists level should help to get that last bit (assuming you're not already using one).

Hi JH.
I use machinists level . i have re-adjusted to have the cut run out down to 1 thoud this afternoon.
I think that is good enough . the darn thing is so heavy evbery time you need to lift one end to get the shim in.

Cheers all for your help
Peter