Put a indicator on the flat way of the saddle. Have to point riding the flat way while taking a cut and see if there’s movement in the cut. You shouldn’t get more than acouple TENTHS of movement on any sliding surface if not NO movement. Good luck
Turning a taper should not be affected by the cross feed lead screw or nut. Nor should the tailstock be the cause if not using the tailstock center.Follow up: Well I’m still contending with the issue. The manufacturer has been very slow to return calls and today I finally was able to put a parts request in although I have to wait to get a quote back in a few days it’s a painstakingly sloooowww process. In the interim I removed the compound slide and installed a machined piece of 4140 that has removed .22mm or .0085 so it has lessened the taper by 50%. Rather than two sheets of paper thick of taper it’s now one. It’s still too much for some parts I need to make that slide together. The next thing to do is to replace the y axis lead screw and nut. If that doesn’t fix it then a new carriage top. If that doesn’t work then I will call a local repair shop to come out and see what they can do. I suppose the lead nut could be moving that much under load it’s really hard to tell I cannot get anything to indicate that tells me I’m having an issue. I did cut a piece of tool steel and a piece of 6061 and both tapered identically so that was a good sign I suppose that it’s not affected by material and it’s a mechanical issue. After all this I think it’s time to upgrade to a 16” lathe if after a year of use we are wearing these parts out this fast. I would hope to get 3-5 years before replacing mechanical components.
I'm really tempted by a test bar, I was thinking of getting it in MT3 and have a sleeve so I can put it in the MT4 head stock and my tail stock.ps - I notice several of the same vendors also offer MT5 ended cylindrical test bars if you want to go that route if your spindle is MT5. This eliminates the MT5-MT3 intermediate sleeve, but I would assume they are pretty ground accurate too. My tailstock is MT3 so it can serve double duty there. Basically its acting as a big long lever exaggerating any angular deviation.
For example (no affiliation)
If I could only afford one, I'd buy the larger test bar for the headstock. A sleeve is probably accurate enough but will more than double potential errors (two mating surfaces for grit/burrs/whatever to cause you to pull out your hair).I'm really tempted by a test bar, I was thinking of getting it in MT3 and have a sleeve so I can put it in the MT4 head stock and my tail stock.
That's the beauty of being able to plug same MT# test bar into either head or tail stock. You can similarly check TS alignment by mounting a DTI in the lathe chuck & turn it around the OD. Yes, you can also do this with a regular dead center, but what the longer bar is providing is extended cantilever length so its going to exaggerate the angular discrepancy: up/down/left/right. Yes big drills & reamers might find their own drilling holes & such but its still better to have the TS aligned. Turning between centers depends on this. No sense having a 0.0002" live center when teh TS is in or out 0.002". Another example, after breaking 2 teeny carbide center drills in tool steel it finally dawned on me to check the TS, sure enough it had migrated off a couple thou. Actually that's not quite true. What I learned is that just tightening the TS down against the displacement grub screws while adjusting can drift it (on my particular lathe). So now I leave an indicator ball on the bar as I'm setting it up & just tweak it down while the needle is giving me constant reference.The tailstock is far less critical IMHO. Drills and reamers will tend to follow their own path anyway
Yeah , I think you are right about the sleeves, I have had my head stock off before but it does sit on the ways for alignment so I might just use the button on the face plate method fof double checking it and call it good.If I could only afford one, I'd buy the larger test bar for the headstock. A sleeve is probably accurate enough but will more than double potential errors (two mating surfaces for grit/burrs/whatever to cause you to pull out your hair).
The tailstock is far less critical IMHO. Drills and reamers will tend to follow their own path anyway (you'll need to use a boring bar regardless for accurate holes) and the tailstock is adjustable for cutting/not-cutting tapers when turning between centers. The spindle taper you want dead nuts aligned to the bed ways in both dimensions (horizontal and vertical, maybe ever so slightly pointing higher toward the tailstock — a few tenths over 12" at most).
A taper test bar isn't a mandatory tool unless you have reason to distrust the accuracy of your lathe (or are planning to rebuild it). It's kind of a one time use tool. (But I own both!).
I might be misreading, but whatever you do, do not rotate a test indicator around the horizontal axis such that you perform some readings with that dial facing up and some with it down. Gravity absolutely will affect your indicator reading significantly.You can similarly check TS alignment by mounting a DTI in the lathe chuck & turn it around the OD.
Those things are pretty cheap on ebay. MT3 bar is like $33 shipped all the way from India. I paid like $60 shipped for my MT5 bar. Been sitting in the tool box for years though but at least it's there.Although a shiny test bar ? who could resist that ? I will just keep my eyes peeled on ebay unless I find plenty of spare cash in my pockets for some reason
Well I finally had to try this for myself. I have 2 new-ish Mitutoyo DTI's. One is 0.0005" the other 0.0001". When I hold them by the body or by the dovetail mounted boss adapter & rotate in by hand, the dial goes nowhere in any rotation. It sits in the exact zero position. Do you think this is a fair comparison to Richards demo or should the needle be loaded?... whatever you do, do not rotate a test indicator around the horizontal axis such that you perform some readings with that dial facing up and some with it down. Gravity absolutely will affect your indicator reading significantly. It’s a common mistake but easily proven to be terribly imprecise - Richard King demonstrates this effect at the beginning of all of his classes:
I’m don’t know what percentage of the gravity effects are with the indicator itself vs the holder arm assembly. I even asked this very question during the class this week.Do you think this is a fair comparison to Richards demo or should the needle be loaded?
I was surprised the Noga flexed that much over the relatively short distance, next time I am at a loss I will try this with my rod and clamp type holders and see how flexy they are.I’m don’t know what percentage of the gravity effects are with the indicator itself vs the holder arm assembly. I even asked this very question during the class this week.
I wouldn’t be at all surprised if it isn’t almost entirely with the holding assembly. But since you always need some sort of holder assembly regardless, and there are many better ways to indicate the tailstock in, I’d still avoid rotating an indicator.
Richard said Stefan G. did some testing of this sort with various indicator holders to see which were most rigid with this type of testing, and that (quality) old-school rod and flexture clamp type holders were way more rigid than flexible mounts of any type.
I’m confused. I thought a dial test indicator is used to take a relative measurement. So unless there is flex in the arm caused by the spring tension from the indicator itself then things should be okay.I know this is detracting from the thread, but I'll post my pics & re-post elsewhere under something like Gravity vs indicator holder.
Noga Mini + Mitutoyo 0.0001: Level = 0.0000, 90-deg = 0.0005 - 0.0008", 180-deg (inverted) = .0011
Noga 14"? + Mitutoyo 0.001: Level = 0.000", 90-deg = .0042", 180-deg = .0055" (suspect a smidge more because it didn't return to zero & there might be some flex in my bar).
- I think the DTI by itself might not see much gravity effect, but the contribution of the DTI holder assembly sure can.
- if you have to use a holder, best to find something significantly more rigid. Or else find some independent way to DTI reference in an angled/inverted position. Reading DTI values at different rotation clock positions is a no-no.
- assembly weight is the enemy here. I suspect a dial indicator would be worse because it weighs more than DTI
I don't think any Asian made lathes have head stocks that rest on way vees.Just out of interest when I removed the headstock I was shocked to find there are no vees under the headstock. But what shocked me about it is that instead of being scraped in you could clearly see that they had used an angle grinder . There were actually big gouges taken out.
If you don't move the indicator base/arm the gravity acting on the arm should not change.Yes, that's the whole issue. Flex in the apparatus that is holding the indicator, not so much an issue with the indicator itself. Think of it this way - if you press your finger on the articulated arm, the indicator registers displacement. Well gravity is like your finger, its a force acting on the mass of the arm assembly. Its moving under its own weight vs. the assumption that it stays locked in position. So the indicator cannot distinguish this displacement from something that is out of round.