D1-4 on a PM1340

I took video the other day to show the various measurements I took.


I've been speaking with Matt via email and he agrees that likely the spindle taper is out of spec. He suggested that I lightly and carefully stone the taper at the area it is contacting the chucks prematurely. I have already used a 3000 grit stone mounted on the tool post at a 7 degree angle to deburr the taper, and in the case of the 3 jaw chuck that did seem to help a bit by reducing it down from 0.004" to 0.002". The worst of the bunch is the 4 jaw chuck that I bought at the same time as the lathe, which I can just fit a 0.008" feeler gauge between the backplate and the spindle face. I have already sent back 1 chuck that I mistakenly rejected as being out of spec for runout (I have already apologized to the seller), but the four remaining chucks are showing 0.002" (3 jaw), 0.004" (5C), 0.006" (ER40), and lastly 0.008" (4 jaw).

So I am wondering if I stone the taper to get the 4 jaw (0.008") to fit correctly, what does that do for the other chucks? Or conversely, if I aim for the 3 jaw (0.002"), will that mean I will still have problems with the other chucks fitting? So what is best to do here? I'm guessing that I should shoot for the least amount of metal to remove and then just see how things look with each of the chucks. Going to be tedious, I think.

I will say here that Matt told me that if I screw up the spindle taper in this pursuit, he will send me a free replacement. But heck, replacing the spindle is probably not something to be taken lightly, so I am doing to be REAL careful about this.
 
What I would do is ask for a new lathe don’t do any thing to the spindle or the chucks until you are sure where the lathe is out of spec. I would bite the bullet buy a top of the line chuck, Bison, Gator or pull the back plates and re machine them to you lathe spindle. I did that to my PM12x36t lathe and most of my chucks ha less than a.001 TIR my go to chuck is a Bison 8” with3 tenth run out.
buy good quality and you want have these issues.
CH
 
COMachinist said:
What I would do is ask for a new lathe don’t do any thing to the spindle or the chucks until you are sure where the lathe is out of spec. I would bite the bullet buy a top of the line chuck, Bison, Gator or pull the back plates and re machine them to you lathe spindle. I did that to my PM12x36t lathe and most of my chucks ha less than a.001 TIR my go to chuck is a Bison 8” with3 tenth run out.
buy good quality and you want have these issues.
CH
Click to expand...

So it is your position that the PM-1228VF-LB is NOT a good quality lathe?

Please bear in mind that this is for HOBBYIST level "work".
 
@Tired&Retired For hobby work, PM-1228VF-LB will do just fine. My 12X36 lathe is only a hundred pounds more, and I do some pretty accurate work on it. Depending on who made it, to what spec, it will vary in quality, but I think PM offers pretty god value for the money.

It is possible to accurately measure your spindle and make the backplates conform to it. If you screw up, you can always get another backing plate for your chuck. If you mess up your spindle, then you're hooped. As I suggested, make sure the nose is concentric, then make your bakcing plates for your chuck conform to it. Now if you have an eccentric speindle or it is not running radially true, than I'm pretty sure PM will try to make it right.
 
@Tired&Retired, I have a couple of comments for you.
  • Taking run out readings on a running machine is fraught with inaccuracies and cannot be relied upon to give you meaningful data.
  • There are only two surfaces that must be accurately assessed on a lathe spindle - the inside taper and the chuck register; ideally, they will be the same. The run out on each surface is typically checked by rotating the spindle by hand and then using a specific procedure to assess run out. If you want to discuss this, we can.
  • Checking run out on the camlock part of the spindle or the chuck body tells you nothing useful .
  • Measuring run out of a test rod held in a 3 jaw scroll chuck is totally useless as well because it reflects the accuracy of the scroll and jaws at that single point of the scroll; it is not a reflection of the accuracy of the spindle or spindle mount or the chuck.
  • How tightly a chuck fits on the spindle depends on how the spindle is ground. It also depends on how the chuck recesses are ground. Given that the accuracy of the chuck is determined by how well it fits the spindle register/taper, how tightly it backs up to the face of the camlock part of the spindle is not that critical. In point of fact, you want full contact with the spindle's taper and the chucks female taper when the chuck is locked down. If the rear of the chuck happens to contact the face of the spindle at that point then that's good but if it doesn't then that is secondary to full engagement of the spindle and chuck's tapers. Does that make sense?
  • Tightening a camlock chuck is simple. There is typically an index mark on the face of each cam. When tightened, each mark should fall between 3 and 6 O'clock. If a particular cam does not fall inside this range then the depth of the stud on the chuck side has to be adjusted to bring the locked cam within this range. You also do not need to serially tighten the cams so many times. Just lightly snug each one once as you install the chuck so it doesn't fall off, then go around again and fully tighten each cam, making sure the index marks fall inside the range I mentioned above.
  • Given how critical the accuracy of the spindle is, I would be very cautious about touching it unless you have the ability to precision grind it in place. If it is off, better to just replace it but first make sure it is actually off.
 
Tired&Retired said:
So it is your position that the PM-1228VF-LB is NOT a good quality lathe?

Please bear in mind that this is for HOBBYIST level "work".
Click to expand...
If it is made china, yea the quality kind of sucks. Chinese stuff is almost always a project. Their electrical is unreliable, the motors are a joke and the machine finish is really poor. Oh and don’t let me forget the castings and cast iron is very low quality, as well. It for sure. Taiwan machines, I have not had any problems with them. They are really good vs Chinese.
CH
 
@Tired&Retired, we seem to have lost you. Looking over my previous comments, I wonder if I offended or intimidated you somehow. I assure you that was not my intent; I actually want to help you sort this out so you and Matt can have a meaningful discussion and take appropriate steps to resolve this issue. Then you can move on to learning to use your new lathe.

Measuring the run out of a spindle, be it a lathe or milling spindle, is simple once you understand the methodology. If you are interesting in going through this process, please re-engage and I'll stick with you until the end.
 
@Tired&Retired

Mikey's giving you good info. He knows what he's talking about.

Think of it like having your fly unzipped, or a cliffhanger stuck in your moustache. It's a little embarrassing, and you'd rather noone noticed, but in the end your glad someone told you.

Have you tried measuring your spindle nose and comparing the dimensions to published specs? Its always better to be certain than guessing. Even if it's a really good guess. I'll go measure mine in a minute, and post the results.
 
OK. This is a quick n dirty drawing, based on measurements i took in a few minutes with a caliper. figure + or - a thousandth or two.

If your spindle nose is really close, this might not help much. But, if its way out, you should be able to tell. If you can take a diameter measurement @ two points, and the distance between those points, calculating the taper will be pretty easy.

 
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Re-read first post, if it is crooked on the taper then the taper is not correct.

It should go on straight.

Have not messed with dx tapers so just guessing, assuming they do not fully seat on anything flat as the taper is the interface.

Maybe there should be a measurable space behind?

Maybe someone with a monarch can provide some reference here.

Sent from my SAMSUNG-SM-G930A using Tapatalk
 
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