Lathe allignment HELP

[Jedi]

Hello friends. Im trying to align a pin that will be in a live centre in the tail stock. It will be automated to clamp and unclamp through the centre of 1000's of washers and will align them. While using the live centre on a test bar im getting a .0001 taper over 3/4 of an inch, which isnt the problem i believe. When i put a dial on the chuck and rotate it with the finger on the tailstock im getting a .0010 taper on the x and theres a .010 on the z height which is really gets me thinking. Is the head alignment off? The boss and I are gonna realign the Head and tailstock monday morning so any help would be much appreciated.

[sid8ball]

First of all the lathe must be level.
The following is Dependant in the lathe capacity but you get the idea.

Use a 2" Diameter bar in the chuck and take 1 cut to clean the length of the material, then a very light cut 6" in length. Use a mic on either end. The tolerance on a Harrison lathe is 0.02mm over 6". If it needs aligning place a clock on at the end of the bar.there should be 2 bolts on the front and 2 at the back of the head stock. If its not to far out you may get away with just loosening the back 2 bolts. There should be an adjusting fixture for moving the head round. When u tighten the bolts back up, the head stock will move a bit. Machine bar and remeasure to test. Repeat until its right.

[Jedi]

So I would align the head with the z axis of the machine first? How about if the tailstock seems to be off in the z axis? I guess im wondering what would I set first as a reference to set the tailstock and the tool turret may be out also?

[sid8ball]

Align headstock first, then a bar between centres to align the tail stock and then the tool post in the x axis with a clock on the chuck.

[HuFlungDung]

Don't fiddle with the headstock adjustment unless the machine has been crashed. I've set up 6 lathes of my own many times, and never touched a headstock bolt on a single one of them yet

The typical lathe can easily be aligned by adjusting the levelling feet at either end of the bed. If the taper of the chucked part is smaller towards the tailstock end, this means the bed is twisted toward the back of the machine, causing the carriage to approach at an angle to the headstock. Adjust the levelling screw downwards (or shim upwards on the floor) on the backside of the bed, at the tailstock end.

This is a delicate miniscule adjustment to make. You think your lathe bed is rigid? It's as flexible as playdoh

This has nothing to do with adjusting the tailstock setover. The test bar that Sid8ball described is the proper method to detect the alignment of the bed with the spindle. You need a good quality chuck with an accurate set of jaws to grip the stock along the entire jaw length, otherwise a wobble factor will set in when you take the test cut, rendering it useless. I usually neck the stock down leaving an inch at the end and an inch of width near the chuck jaws to take the test cut with. A very sharp tool with plenty of positive rake is necessary to prevent tool deflection from messing with your head on this.

[Jedi]

Today i levelled the machine, and put in a 2" piece of mat'l. It was magnetic and im pretty sure it was stainless so im thinking its a 404 or a 1040 but it wasnt mild steel. Anyhow the problem now is getting a clean cut on it. I keep getting vibration after 6" and ive changed from 300 to 2500 rpm and .5 ipm to 20 ipm. Ive changed clamping pressures and roughing bits to finishing bits. There is a .001 taper over 2.5", getting smaller towards the tailstock. Any help would be great as ive just finished cnc/machinist diploma and havent attempted something like this. And the boss isnt a machinist.

[sid8ball]

What machine is it?

[Matt_S]

Originally Posted by Jedi Today i levelled the machine, and put in a 2" piece of mat'l. It was magnetic and im pretty sure it was stainless so im thinking its a 404 or a 1040 but it wasnt mild steel. Anyhow the problem now is getting a clean cut on it. I keep getting vibration after 6" and ive changed from 300 to 2500 rpm and .5 ipm to 20 ipm. Ive changed clamping pressures and roughing bits to finishing bits. There is a .001 taper over 2.5", getting smaller towards the tailstock. Any help would be great as ive just finished cnc/machinist diploma and havent attempted something like this. And the boss isnt a machinist.

2 inch barstock with 6 in. overhang?You shouldnt be getting chatter.Are you using coated carbide inserts?If so try switching to a cermet small nose rad.

[Jedi]

yeah im using coated carbide and theres a nice finish the first 6" inches and theres vibration marks last three inches towards the tailstock.The machine is a Dainichi f20.

[ctate2000]

There could be many things going on with your machine. Your description sounds like simple run outto me. However I have not seen the set up. The first question I have is why are you traversing towards the tailstock? If you are crossing centerline with the tool you will get a concave shape which can look like true taper. If this is a CNC machine don't screw with any alignment issues for .001 over six inches. Program it out. If you are getting a concave shape from the tool crossing centerline then it will be impossible to program it out. You typicaly have this problem from being out of level. If it is a boxway machine wear in the ways can cause the same issue. No way to tell without seeing set up.

.001 over six inches is not bad. Remember this is a turning machine. Holding less than .001 on a turning operation is not impossible but becomes very difficult. In a production environment less than .001 is usually reserved for grinding operations.

[jody pitts]

try new bar stock after leveling but make it a couple thoudandthds over 6"

[Jedi]

I think the reason that i was getting vibrations was from the stainless steel i was using so i used 1018 and it was much better. Anyhow the boss thought i should just make sure everything was fine so first i levelled the machine, then i alligned the head stock. and its been cutting within .0002 over 6 ". I gave the machine a good overhaul and its working really well.