Lathe Taper

S

srfallsallot

Registered
Registered
Joined
Jul 8, 2017
Messages
94
I am new to machining. I have a Logan820. Yesterday I started a project in which I needed about 10" of a steel 1/2" dia rod turned down to about .466" dia. The head stock runs true as does the ER32 collet as no runout is detectable with my .0005" indicator. It was chucked up in a ER32 collet on the head end and a rotating center on the tailstock end. As I was measuring my progress I realized I was cutting a taper. I have adjusted the tailstock until I drove my self crazy. I am now getting .4660" on the head stock and .4665 at the tailstock. What is an acceptable number for my lathe?

The steel is cold rolled 1/2"dia. The finishes I get are not pretty.
 

Attachments

  • Lathe Taper.jpg
    Lathe Taper.jpg
    478 KB · Views: 21
Doesn’t sound like very much to me. What’s the requirement for your part?

Your numbers sound like about .466”, what cutting tool are you using? Surface finish usually come down to tool geometry and feeds/speeds.

John
 
Last edited:
I would say that's quite an accomplishment. Cold rolled machines best (if you can call it that) with a good depth of cut (.020-.030 min.). Trying to remove the small amount required over that length would frustrate even the best, especially if you're trying to adjust to remove taper. Using a carbide insert instead of a dead sharp HSS was also working against you. I would say .0005 over 10 inches is an impressive feat, even more so considering how you were going about it. I would tell you to look into the "2 collar" method for removing taper, but you're already nearly as close as you could hope.
 
Sloppy... not...

I would be concerned about the middle. Without a follow rest the stock will just move out of the way.

How did you align your tailstock?

A 2 coller test, using a 4 inch or so length of 1 to 3 inch diameter stock turned between centers will allow you to get tailstock aligned to get equal diameters.

Even if it is slightly different elevations, the 2 collar method compensates as you measure the cut and adjust until both ends same.

Once done, you use dial indicator to adjust.

Sent from my SM-G781V using Tapatalk
 
I will use wet and dry paper to finish cold rolled , if it needs to be pretty. Cold roll doesn’t leave a nice finish with carbide on a light duty lathe. I like MrWooppee reply. If you are trying to take something into the tenths range that is what grinding is for. On a lathe I have been known to use a file and wet and dry paper to make a finial fit.
 
5 tenths in 10"?
I'd call that a win, especially in cold rolled at 1/2" diameter.
 
You must log in or register to reply here.
Back
Top