Pat, how did you measure with the dtiI that the tailstock was higher?
If the dti was mounted on the top slide and then the saddle traversed over the 8" there could surely be other explanations for the apparent rise of 0.18mm.
For example, unless you first had the talistock set perfectly aligned in the horizontal plane. you might have been running the dti plunger "off the line" (although that maybe would show a drop rather than rise).
Have you tried with the tailstock barrel extended (and locked) by different amounts?
From all the published methods of checking tailstock alignment in the home workshop, I believe taking cuts at both ends of a test bar is usually considered the favourite.

Possibly! I don't know if your Amadeal has the same adjuster system as my Warco did, but it certainly wasn't easy to adjust the tail-stock on that machine.

The effect I had was a kind of figure of eight movement high-low/right-left around perfection coupled with an unwanted jump at the last moment, usually when tightening up. Tweaking went repeatedly: poor, better, nearly right (hurrah), poor again(temper tantrum).

I never sussed out exactly why the adjustment was so awkward, but put it down to the relatively crude method and/or indifferent finish of the block inside the tail-stock. Chief suspect in my case was the uneven surface of the block causing the tail-stock to tilt. I never found out because after a wasted afternoon I suddenly got it right. There may be a knack to it, because thereafter I was always able to re-align the tail-stock fairly quickly – no more than 5 or 6 attempts taking about 10 minutes. Practice makes perfect, or possibly continued adjustment flattened a bump! .

Perhaps your easy adjustment of the tail-stock left the thing wonky and it's worth having another go?

Dave

I would fully extend the tailstock and (1) test along the top of the extended barrel to see if it is level and (2) see if it consistently locks in the same position.

I fitted a brass gib to my tailstock to make it easier to adjust alignment.

Make sure the screw under the tailstock is keeping it pulled down.

On my ancient Clarke CL300 (~20 years old now!) the tailstock needed a shim. JS gave me a SEIG one a few years ago, but it was high for the CL300 (perhaps not surprising it wasn't matched exactly!) so I machined the top part of it to fit my Clarke base without a shim.

Going back to (2) above the recent Seig tailstock barrel is a MUCH more accurate fit in the matching tailstock than the old Clark pair were/are. I had been planning to fit a guide collar around the old one.

Neil

No you can't safely do that. Reaming it in situ will not work when the misalignment is as much as you say (.18mm/.008" ) . The reamer will tend to follow the old hole. But the high headstock will tend to lift it upwards. So you will probably end up with an oval hole, or something worse.

Reaming on the bench is not going to move the hole down lower because again, the reamer will follow the existing hole.

What you need to do is machine just under .18mm/.008" off the base of the tailstock to lower the whole unit. Tailstocks are often set at the factory (on good quality lathes) to be a thou or two higher than the headstock spindle to allow for wear over time. (But 8 thou is way too much.) If your tailstock is in two pieces to allow for horizontal alignment adjustment, that interface is where to remove the metal from. (assuming all burrs etc have been removed already?).

But first there are a couple of things to check. 1 is to check tailstock height at different points along the bed to make sure the bed is straight. I have seen one small Chinese lathe with well over 10 thou bend at teh far end of the bed. In that case it sagged downwards, but upwards could be just as possible.

2 is to make sure your headstock spindle is aligned vertically with the bed. If it's not, the headstock mounting surface will need machining or scraping etc to bring it down parallel to the bed. No point in machining the tailstock to match a headstock that yet needs adjustment.

Edited By Hopper on 12/05/2019 11:28:39

In similar circumstances I've found it pays to trust nothing! Try putting a 25 x 300 mm bar in the chuck and positioning the DTI at the end of the overhang. You might be surprised how easily a hefty bar bends under finger pressure. As the tail-stock adjustment is done by screws pushing against a block, a poorly formed block could jack the tailstock up and bend the test bar enough to make your DTI reading suspect. Something's wrong but I'm not certain you've nailed the cause yet. So far the thread has suggested:

1. Headstock misaligned
2. Tail-stock high
3. Barrel taper off-centre
4. Measurement Error
5. Warped bed
6. Error due to crude adjuster mechanism and or finish.
7. Position/Locking inconsistency in the barrel

As fixing the wrong problem would introduce unpleasant new complications, I suggest it's worth narrowing the possibilities, for example a cutting test might eliminate measurement error or provide more clues.

Tracking down the cause of a 0.18mm error can be challenging. As Martin said ' I suggest you allow plenty of time, take a good note pad for readings and sketches, take readings twice to check consistency by rotating testbar and repositioning the DTI and in general try to trap or minimise all other sources of measurement error to fully identify the issue . ' Martin's advice fits with my experience – whenever the cause isn't bleeding obvious, it's amazingly easy to be led astray by misleading measurements.

Dave