Taper on a new lathe during a normal turn.

[sr71xjet]

Checking taper is a given anytime a lathe is fastened down. Any lathe, it need not be new. And on occasion as time passes, the frame may not stay straight. Having less than a thou in 12 inches on a new machine is a good start. How much you can tolerate is a matter of your personal tastes and needs. If it has too much to suit what you do, adjust it. If you can live with it, leave it alone. Be aware that there are two axes for distortion, one side to side, that can be adjusted with the offset of the tailstock. And the vertical, where the headstock sometimes needs shimming as well as the tailstock. Setup the indicator for both dimensions when you check.

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That’s good advice thank you

 

[ddickey]

What kind of level did you use to make sure there is no twist.

 

[sr71xjet]

Delete

 

[sr71xjet]

delete

 

[sr71xjet]

This is what I used.

 

[rabler]

Just remember that lots of things can cause taper. Just because you are using the tailstock doesn't mean it is the only factor effecting taper. I probably wouldn't worry too much about .0008 over 12", but if you do, use a systematic approach, or you may end up very frustrated.

 

[mksj]

One cannot assume that any machine will cut perfect after being shipped and installed. There are also a multitude of factors that effect cutting diameter and linear diameter along the length of a work piece. General rule when holding stock in a check is the unsupported stick out should be no more than 4-5X the diameter and is material and diameter dependent. The type of cutter, the DOC, feed rate will all effect the finished diameter when you are targeting diameters in the sub thousandth. If you need to hit high accuracy you need to do a series of cuts before your target to determine actual diameter removed vs. what the the dial/DRO says.

The first thing to check would be to check the headstock alignment without the tailstock, there are a number of different methods to evaluate this. If you are measuring a 1.5" bar 12" out supported by the tailstock, then it is a simple matte of adjusting the tailstock set screw X position. I have a similar lathe, and when the tailstock is perfectly centered with an alignment bar and I do a test cut, I can still get a very small taper and I need to ever so slightly adjust the tailstock position to compensate and this is specific to the cutting dynamics. This assume you are chasing sub 0.001" accuracy over the length of the work. There will also be some deflection of the system/materials/thermal effects/etc.

The Sunmaster lathes (1440TL) tend to be very well aligned from the factory, but if you look at the tolerance spec. sheets they are typically in the +/-0.001" ranges. It takes careful adjustment to get tolerances below that point and it will be only applicable for the circumstances under test. Although some of my work requires sub 0.001" accuracy, I need to setup my turning process specifically for that target. There are quite a few posted videos on the subject.

You also should recheck the level of the lathe shortly after setup, I tend to do weekly x2, then every 3 months.

 

[ddickey]

And rest the level on your cross slide so you never have to move it.

 

[sr71xjet]

And rest the level on your cross slide so you never have to move it.

Yes sir, i did that and it is spot on as far as i can tell. Im still learning all of this so ill keep asking questions. Thank you.

 

[sr71xjet]

One cannot assume that any machine will cut perfect after being shipped and installed. There are also a multitude of factors that effect cutting diameter and linear diameter along the length of a work piece. General rule when holding stock in a check is the unsupported stick out should be no more than 4-5X the diameter and is material and diameter dependent. The type of cutter, the DOC, feed rate will all effect the finished diameter when you are targeting diameters in the sub thousandth. If you need to hit high accuracy you need to do a series of cuts before your target to determine actual diameter removed vs. what the the dial/DRO says.

The first thing to check would be to check the headstock alignment without the tailstock, there are a number of different methods to evaluate this. If you are measuring a 1.5" bar 12" out supported by the tailstock, then it is a simple matte of adjusting the tailstock set screw X position. I have a similar lathe, and when the tailstock is perfectly centered with an alignment bar and I do a test cut, I can still get a very small taper and I need to ever so slightly adjust the tailstock position to compensate and this is specific to the cutting dynamics. This assume you are chasing sub 0.001" accuracy over the length of the work. There will also be some deflection of the system/materials/thermal effects/etc.

The Sunmaster lathes (1440TL) tend to be very well aligned from the factory, but if you look at the tolerance spec. sheets they are typically in the +/-0.001" ranges. It takes careful adjustment to get tolerances below that point and it will be only applicable for the circumstances under test. Although some of my work requires sub 0.001" accuracy, I need to setup my turning process specifically for that target. There are quite a few posted videos on the subject.

You also should recheck the level of the lathe shortly after setup, I tend to do weekly x2, then every 3 months.

Thanks for the great advice. Im sure ill have other questions.