Ya know how you learn more, then do something you have done plenty of times, but now that you know more, you notice things that you never noticed before? Well thats what happened to me! I took apart a bunch of the lathe to clean everything up and found some trouble. I also tried using the 4 jaw to indicate something in true and found a bunch of run out, so much so that the whole chuck is visibly eccentric when the lathe is on, and at higher speeds, its shakes the lathe as if I am turning off center.
Lets start from the beginning. The compound. I took off the tool holder and loosened the gib then walked the top of the compound off the bottom of it. Looking at the compounds base dovetails, I see that there is a very thin wear strip on both sides, and it doesn't look like it is wearing anywhere else. I am wondering if there are burrs on the top dovetails that are preventing decent contact and causing that strip of wear. I just got a granite surface plate so once I figure out how to do the dye transfer thing I see in a lot of videos, I will find out how flat it is. Pics of that:
Also, the base a has very nice ground finish on the top... But that doesn't touch anything. Why is that ground but the ways themselves are just machined (and somewhat roughly I might add)? I saw a video about the Seig X2 mill where the guy said the Chinese were getting a reputation for very poor quality so they started grinding the dovetails instead of machining, except they ground the surfaces that don't touch anything and left all the contact surfaces roughly machined. I wonder if thats the case here...
Moving on, I took the cross slide off ,and noted a few things.
-There are gouges in the bottom dovetails
-There are corresponding dings in the top dovetails
-The gib is only spotted twice even though there are 4 gib screws and 1 locking screw
-The nut for the lead screw is a split nut with tensioning screws, but they were not tensioned
-The cross slide ways are scraped, but there is still rough machining left in some areas. Shouldn't that have been ground first, then scraped?
-There is play in the lead screw end block that seems to be on par with the 20 thou movement I couldn't seem to remove, though I am not certain thats what is causing it. I can't find any other play in the assembly.
Picture of the bottom dovetail gouges. It was tough to get the picture, but the gouges are along the right side running almost the full length of the dovetail.
Picture of the dings that caused those. I looked back at the pictures from when I first got the lathe, and the dings are there, I just didn't notice them. I think this happened before I got the lathe because the picture of the assembly from 6 months ago was taken when the slide was removed, wiped off, then the picture was taken. No where for it to have gotten that.
Picture of that split nut. The machining is pretty rough, but this is the bottom and it doesn't touch anything. The top is better, but not by much. When I put it back together, I will try to tension the screws and see how much backlash is removed.
Picture of the gib. You can see it is ground very nicely, but only 2 spots, despite the 5 screws. Is that normal? All the gibs I have ever come across are spotted for each screw.
Here is the rough machining on the scraped ways. I wonder if that is just a low spot or an oversight. Seems like a waste to go through the effort of scraping to leave a few sections of rough machining. Also, is scraping always done by hand or was this done by a machine?
Here is a picture of the play I found in end block. I am not sure if it is supposed to have play, but I haven't been able to find anywhere else that the movement could be coming from. Is there a way to call users in this forum? Maybe
@qualitymachinetools could have a look and tell me if that looks right.
Now on to the 4 jaw. I took it apart to see if I could find whatever is causing the run out. It was really bad. After indicating a part in true so there was less than .00025" ecentricity at one point, about .150 inches farther out from the chuck, it was out .003". No amount of tapping with a dead blow or adjusting the jaws could get it to run within .001 at both points .150 inches from each other. The part that was grasped in the jaws and the part being indicated where machined together, in 1 set up, one after the other. As in I roughed both diameters, finished one, then finished the other, so its very unlikely that the part was bumped or shaken loose between those two cuts. It was also consistent among 3 different but identical parts.
As a side note, is there any way to check that the cross slide travel is perpendicular to the spindle bore? I am not sure how I would measure that.
I measured the spindle again, both inside the taper and on the face. There was the faintest wiggle from the taper with a .0005" DTI, but it must have been under .0001". Though when I first got the lathe, I checked the same spot with the same indicator and got absolutely zero movement. The face was also perfectly square. The indicator showed almost no movement, less than the spindle taper. I also pushed on the spindle to check the bearings and even leaning into it fairly hard, it didn't move at all. Thats a good sign right?
When I took the chuck apart, I noted several things.
-There are a few dings on the rear of the chuck with the backplate removed. The first thing I did when I got the lathe was clean the faces and remount the back plate. I don't recall scuffing it up at all, and I was specifically careful not to drop it or place it on any rough surfaces. The lathe did ship with the 4 jaw assembled and the back plate installed if I recall correctly. I think the dings and scuffs are from carelessness from the manufacturer.
-The backplate has a ground surface and a machined surface on the face that faces the back of the chuck. Again, the ground surface doesn't contact anything and the register surface is machined.
-The bore that registers on the spindle nose is machined, not roughly, but definitely not as nice as a ground finish
-The face that registers on the spindle face is ground, though the 3 jaw that shipped with it isn't ground on that face if I remember right
-The rear of the 4 jaw is ground, though there are some dings on the register surface and a deep gouge on the back of the face that doesn't contact anything.
Here is picture of the back of the chuck. Note the dings, gouges, and scuffs, as well as the nice ground finish.
Tried to light up the gouge so you can see how deep it is. That sucker is nasty and I am trying to imagine a way that it got in there.
Here is the backplate on the end that contacts the chuck. You can see the ground surface where it touches nothing, but the machined surfaces where it contacts other parts. You can also see what looks like chatter marks in the bore.
So thats how it looks after 6 months of use. I want to figure out how to check the contact in the dovetails and see if the ground surface is worthwhile, or if the rough edges defeat the purpose. I also want to see if the cross slide is making decent contact in the ways, or if those wear marks are really the only areas where it is touching.
So a few questions if anyone has gotten this far:
1. Whats with the very nicely ground non contact surfaces, and less nice machined contact surfaces everywhere?
2. Where should I look to find the 4 jaw run out?
3. How do I check that the apron travels parallel to the spindle bore and cross slide is perpendicular?
4. What is the right way to measure flatness and squareness of the dovetails?
I hope the updates and pictures are worthwhile to people considering the machine, as well as those who already have one. I am learning as I go and I am still pretty new to machining. I got my 7x12 lathe in February 2016 and the PM 1030V in August 2016, so I only have a year of experience with lathes. Though I learn more and more and I am doing my best to pass that on.