Heavier cuts on victor lathe

[taiwanluthiers]

I've been trying to learn how to make a heavy cuts on a victor lathe (and it can handle the load).

The problem is I've not been able to produce good chips off the cut. I would run it at about 300 rpm or less, with a diameter removal of 4mm (2mm depth of cut), and at lighter feed rate I would get bird nest of strips coming off the stock, and that ends up being a problem. I tried to kick up the feed rate to get the chips to break but it ends up causing the tool post to move (resulting in broken inserts).

I had to reset the tool post, reset the compound at 0 degrees to give me the best rigidity and even then the chip doesn't look that good though it does break...

Is there any guide on how to properly take a heavy cut? I watch Abom's video and the feed rate he's making seems to be around B1-A5 setting on the feed rate dial (basically about 0.017" per rotation)

 

[twhite]

How about some info on material being cut. Along with the tooling being used. Pictures are always an added help.


Cutting oil is my blood.

 

[taiwanluthiers]

I'm cutting annealed 4140 steel with WNMG inserts

 

[rabler]

What diameter? You probably want around 400 SFPM on carbide inserts, so 300 RPM would be for fairly large stock, around 5".
Roughly RPM = SFPM * 4 / diameter, with diameter in inches.
@davidpbest has a good book on carbide inserts. Generally with carbide if it is not breaking a chip you need to turn faster and/or feed more. Feed sounds reasonable, so up your speed. HSS is not a bad option to try out also, generally HSS works good around 100 SFPM.

 

[taiwanluthiers]

It was 40mm in diameter. I have no idea what SPFM I'm aiming for. Is there any online guide on carbide inserts, not books I have to order and wait months to receive (shipping is kinda messed up because of covid).

 

[rabler]

It was 40mm in diameter. I have no idea what SPFM I'm aiming for. Is there any online guide on carbide inserts, not books I have to order and wait months to receive (shipping is kinda messed up because of covid).

Sometimes the insert case will have SFPM ranges printed on it, as well as feed rate. The range depends a bit on the cutter geometry, as well as material type. Carbide inserts tend to run around 200-800 SPFM, even faster in soft materials. Generally for hobby work you don't push the higher end of those ranges though. Manufacturing likes high speeds for fast production.

Google "sfpm calculator"

 

[ddickey]

Chart says 213m/min. or 700sfpm
1700 rpm and .018"/rev or .457mm/rev.
300rpm is way to slow.

 

[twhite]

RPM sounds a bit low depending on dia of stock. Feed might be a bit high also. SFM should be 300 to 400 from a quick look.

Go to the insert manufacturer site they have good speeds and feeds for their products.


Cutting oil is my blood.

 

[john.oliver35]

Try this for a quick general guideline

Speeds & Feeds

The premier source of tooling, parts, and accessories for bench top machinists.

littlemachineshop.com

 

[taiwanluthiers]

Chart says 213m/min. or 700sfpm
1700 rpm and .018"/rev or .457mm/rev.
300rpm is way to slow.

1700 RPM is like the high end of rotational speeds for most manual lathe, in fact many manual lathes can't spin that fast without problems (for example most chucks shouldn't exceed 2000rpm).

Surely they do not expect you to run this in a manual lathe right? I know a lot of CNC lathes can spin very fast, like even 5000 rpm.