What would cause this?

tundrawolf

tundrawolf

Registered
Registered
Joined
Jan 5, 2018
Messages
28
So this is literally my first lathe operation. I'm cutting two tubes to join and weld them together. But I had to turn down a thick portion of one tube to get it through the chuck spindle.

I used 3 in 1 oil, and auto feed. It looks galled and forced, not clean at all. What am I doing wrong here?

IMG_20180105_135915721_1515185977030_1.JPG
 
Check your tool bit for proper geometry and sharpness, and you might want to use a heavier oil and maybe slower speeds
Mark
 
Tool bit might be too high, check it by pinching a 6" steel scale (ruler) between the bit and the part and adjust the tool height until it's straight up and down. The other thing is 3 in 1 oil is not good for cutting, you need high sulfer content found in Rigid pipe threading oil.
 
I agree with Mark.
Also, make certain the tool is on center. You can face a piece of stock and use its center to set your tool to or rotate
the tool holder to check against a center in the tailstock.
If that doesn't help consider the metal your using. Some won't turn well and it's hard to get a good finish.
The oil you used won't work well for cutting. Get some cutting oil. The stuff plumbers use, found in most hardware and lumber
stores, works well.
It could be the rigidity of your machine or bearings but everything else must be checked first.
 
Regular engine oil can be used; I use chainsaw bar oil, just cuz.
Mark
 
that may not be your fault but the time of material you are turning
 
+1 with Ed. Some steel does not turn well, tears and looks awful. I had to machine a piece of black iron pipe down once, this looked like your piece.

MrPete222 has a video on a shear tool which is meant to machine such difficult-to-machine material to give a better finish. Easy to make so I made one. It works but the chips are long thin and stringy.
 
Most steel tube and pipe is produced from rolled flat stock which is notorious for its poor machining qualities yet excellent formability.
The faster you turn it the better the results will be, if the machine is capable I would turn such a small part in that material at 3000 RPM's minimum at .006-.008 IPM feed using a negative insert with a smallish sub .015 nose radius as a start and go from there, the first few may be scrap but it appears to be a common material which is cheap so have at it.

I often make electrical conductors from Customer Supplied Material, if a mistake is made one can not simply saw off another piece of stock and start again, they supply just enough.

Like so, 6 5/8" copper pipe 19 3/4" long with a 3/4" deep counterbore on each end at 5.875" +.002 -0.000 diameter, I only get one try.

i-g2fdGW4.jpg
 
Last edited:
Wreck™Wreck said:
Most steel tube and pipe is produced from rolled flat stock which is notorious for its poor machining qualities yet excellent formability.
The faster you turn it the better the results will be, if the machine is capable I would turn such a small part in that material at 3000 RPM's minimum at .006-.008 IPM feed using a negative insert with a smallish sub .015 nose radius as a start and go from there, the first few may be scrap but it appears to be a common material which is cheap so have at it.

I often make electrical conductors from Customer Supplied Material, If a mistake is made one can not simply saw off another piece of stock and start again, they supply just enough.

Like so, 6 5/8" copper pipe 19 3/4" long with a 3/4" deep counterbore on each end at 5.875" +.002 -0.000 diameter, I only get one try.

View attachment 253089
Click to expand...

This is the case as well, it is a recoil spring tube from an expensive battle rifle, I am not sure what manner of steel it is. I'm using a slower speed, so that can be part of the problem...
 
You must log in or register to reply here.
Back
Top