Getting a taper

S

SteveBrown

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Going left to right I'm getting .002 taper but not changing the depth of cut and coming back to the left it takes the taper out. This is using HS steel on aluminum. Speed is the middle pully on a 10L south Bend. And the slow speed setup on the motor pulls
Not sure of the speed I'll have to look up the chart. Why would going back to start with no change in cut take the taper out.
Steve
 
Does it do this no matter what angle the compound is set to? If it is dependent on the angle of the compound, I'd say it could be a loose compound gib.
 
Some pictures of your setup might help us diagnose it better, closeups of the tool you're using, etc.
How much taper in how many inches? Is there visible wear on the ways?
 
Dimension's of the work piece would help. What I think you may be doing is starting your cut near the chuck and going to the free end. If this is true there may be a certain amount of spring developed in your work piece.
 
Generally most all cutting is done from right to left, it is possible that wear on the fit of the saddle on the ways may cause the problem.
 
How long and what is the diameter of the workpiece? If long and slender are you using the tailstock? How heavy of a cut are you taking?

Sounds like the workpiece might just be springing/pushing away from the tool bit...

Ted
 
Sounds like it is taking out deflection in the part. Is there a larger contact area on the tool on the first cut and smaller on the second, this depends on the shape of the tool.

Is the compound locked?
 
Parlo said:
Sounds like it is taking out deflection in the part. Is there a larger contact area on the tool on the first cut and smaller on the second, this depends on the shape of the tool.

Is the compound locked?
Click to expand...
When you ask is the compound locked, do you mean to prevent it from changing the degree of the angle. I don't know of any lock on the feed of the compound.
I'm running this in a 3 jaw chuck with a live center on the tail stock. It's the first thing I've Run on the lathe after aligning the tail stock with an Edge aligning bar. The length of the part is about 7 inches but machining 3.5" from 1/2" to .380" in several passes of course. The tool was an old HS steel, not sure of the angles it was ground. I'll see if I can dig it up from the pile of tools in the bowl. The tool was centered on the diameter fairly well. And the finish was not a mirror but the best I've obtained on this material.
 
Very few lathes have compound or cross feed locks, most depend on a tight gib for the compound and just a snug gib on the cross feed I have personally only ever seen one lathe with a cross feed lock, it was on a heavy duty Axelson lathe.
 
SteveBrown said:
When you ask is the compound locked, do you mean to prevent it from changing the degree of the angle. I don't know of any lock on the feed of the compound.
I'm running this in a 3 jaw chuck with a live center on the tail stock. It's the first thing I've Run on the lathe after aligning the tail stock with an Edge aligning bar. The length of the part is about 7 inches but machining 3.5" from 1/2" to .380" in several passes of course. The tool was an old HS steel, not sure of the angles it was ground. I'll see if I can dig it up from the pile of tools in the bowl. The tool was centered on the diameter fairly well. And the finish was not a mirror but the best I've obtained on this material.
Click to expand...
I was referring to the screw to lock the gib. This is used when performing operations like parting to lock the compound slide from moving.
 
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