There are two usual methods to align a lathe tailstock.
1. Put a bar between centres and take a cut along its length, measure each end, adjust tailstock and repeat procedure until it is within acceptable limits. This is time consuming and you reduce your bar to swarf.
2. Get a standard ground alignment bar made for the purpose. Mount it and traverse its length with an indicator. Adjust tailstock to suit. This can be much quicker than method 1. but you need to have an alignment bar.
Having been born with a hefty dose of the lazy gene I wanted something with less work and this is how I do it.
Just rotate the chuck and watch the clock. Adjust as required.
This works as to the centers, when adjacent. Alignment bars determine this too, along with an indicator, that detect alignment and parallelism regarding both planes to the ways. Taper when machining originates in one or all.
C-Bag just tested his, and regulated from .004 something to a couple tenths. In a part of any length that's a reduction of 20x.
...we'll learn more by wandering than searching...
Thanks Tony, I like the method you use when machining shorter parts. I use several different methods for tailstock alignment for longer parts and have come the conclusion that no matter how well it is initially aligned, there are too many other production factors that can still cause a slight tailstock misalignment when machining a batch of the same parts to be within +/- 0.0005" of spec.
I also recommend learning to use a good lathe file and emery cloth, and taking periodic micrometer measurements along the length of the part to finish the part to a tight spec. I found that even after waiting for the part to cool down after machining, the hot halogen work light can throw your part off spec and may need to be turned before taking the final measurements.
I didn't have an alignment bar and that left me with the No.1 method in my post, that is OK for checking the adjustable lateral alignment but not so much the non-adjustable vertical. I was suspicious of the vertical alignment on my lathe and that was really the motivation for checking that with the dial gauge method. I was right, the tailstock seems to have been let out of the factory lower than the headstock. Shimming was the only way to fix it, not ideal but needs must, unless I machine the base of the head stock and that wouldn't be too easy. I wish that the tailstock had been high, I could have fixed that easily.
I had a guy come in and scrape the ways on one my old lathes. Ideally we should have removed the head stock then trued the entire bed but time and money really didn't allow this extensive of a repair to be done. Jack specialized in truing up machines for a living and although I knew the process and had done 1 or 2 bed scrapes on smaller lathes like Atlas and Craftsmen, but for my Victor 16/22x 60 I felt that a professional could do a better job a whole lot faster than I could have done at the time.
He rolled in a couple of wooden boxes and his tool chest then we started in. First he opened 1 8ft long box with a hollow 1.70" diameter truing bar in it and a polished thin wall tube about 18" long the thin tube went in the spindle bore to protect the truing bar as it was slid through the spindle My lathe had a back thread on the outside of the spindle where I kept a small 4 jaw chuck mounted for when I machined long cylinder rods so this was a help in checking the head alignment to the bed He put on a pair of nitril gloves than a pair of soft cotton gloves before he handled his truing bar after checking the bed in dozens of places he determined that about .003" would be the minimum that needed removed but that would still leave a slight dip of about .002" in one small 12" long area We opted to remove the full .005" Then he trued the cross slide but did not remove the carriage top from the apron which he felt really needed attention I just couldn't afford that extensive of a repair If I could have we would have removed the head stock to set everything perfect. After the work on the bed and cross slide was completed we removed the tail stock from its base and shimmed it back to the proper height it took nearly .015" apparently it had been low for along time or someone had scraped the bed long before I got the lathe.
I don't have a problem with a shimmed tail stock just like I didn't have a problem with paying the $1,500.00 for the work he did because it would have cost me twice that to have tried to do the job by myself even if I could have rented the necessary equipment that I didn't own for the task
I can understand where you are coming from. I've never offset any of my tail stocks I did at one time have an adjustable live center which could be offset that I found quite handy a few times.
Thanks for your excellent postings I shall be following them with great interest, lovely bike buy the way, I cant recall the Italians ever making a bad one. Re tailstock alignment every production lathe I have used has had a dropped tailstock due to wear of the base casting having a smaller footprint than the saddle, and probably sliding along the bed a lot more in use. One of my earlier posts was reboring the tailstock in sit u and making a new barrel, been great ever since.
Given your obvious expertise in machining morse tapers etc I am sure you could do this if you wished.
The Italians didn't make that, I did. That's what I use my tools for.
Just an idea but I could permanently dowel and bolt the two halves of the tail stock together to essentially turn it into a single piece.
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