D1-4 on a PM1340

[Tired&Retired]

@Tired&Retired, I was sad to see that you took a grinder to that spindle register. Given that you set it to 7 degrees, even if you only ground a little bit off, no standard D1-4 chuck will interface securely to that spindle because the geometry is now off. I think you should have another discussion with Matt and let him know what you did; I suspect he will agree that the spindle needs to be replaced. Since you'll be in there anyway, you might consider upgrading the spindle bearings to a precision class set (ABEC 5-7 or metric equivalent).

I described exactly what I did to Matt, and he is OK with it. Heck, I dunno, but isn't there some difference between "grinding" and "polishing"? Spindle speed was at the lowest setting on the lathe, which I think is 40 to 50 rpm. As for time I held that 3000 grit rod to the spindle taper, no more than counting to 10, then looking at the finish. When I say it was at 7 degrees, that is + or - a hair. I lined up the rod with the spindle taper as best I could by eyeball and feel, as it was being held in a drill chuck mounted on my compound slide. Then looked at what the indicator on the compound slide showed and it was 7 degrees. As for it being exactly 7 degrees, etc, or 7.125 degrees, heck, I don't know. I don't think I have anything that could actually measure to that precision here.

Are you all forgetting this is hobbyist level, and I am posting this in a "hobby-machinist" forum? I guess my wife "said" it best with her expression when I told her that I wanted the lathe to be better than one thousandth of an inch tolerance when I showed her a 0.0015" feeler gauge and I wanted it BETTER than that. That was the "are you serious" look. LOL!

Yeah, I want the stuff I work with to be as accurate as reasonably possible, and will make reasonable efforts in that direction. But for someone(s) to be basically claiming that I ruined my lathe with a 3000 grit polishing stone on a hardened surface with minimal (and I do mean MINIMAL) contact duration and pressure, well, sorry, we are not talking on the save wavelength. 3000 grit doesn't remove all that much material even with a lot of elbow grease. I used to polish a lot of stuff in the past. I know the value of a light touch instead of getting TOO aggressive.

Anyway, Matt has no problems with what I described here and to him. He actually advised me to be MORE aggressive on the GRINDING of the spindle nose taper. And if that DOES ruin the spindle, he will send me a free replacement. So I don't have a lot to loose except perhaps not knowing what sort of headache I would be in for to replace the spindle, of course.

But quite honestly, I am thinking that what are the chances that I would be able to polish/grind the spindle taper and get all of my chucks to fit flush with the spindle face AND the spindle taper, when the gap I am seeing on four chucks is 0.002", 0.004", 0.006", and 0.008"? I don't see how I could do that with ALL of the chucks by addressing the spindle nose taper. Or am I missing something here?

Might it not actually be smarter for me to address each and every chuck and polish/grind THEM to get each one to fit as precisely as I am able?

Of course, mounting them on the lathe so I could grind/polish the female taper of the chucks would be a real challenge for me. Would mounting a rod in each chuck (which would be a MT5 alignment bar be safe? I am real leery of just that MT5 taper holding such a contraption in place securely without coming loose and bounding across the floor of my garage and bouncing off of my vehicles. So is there a better/safer way to do this?

 

[Ken226]

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Of course, mounting them on the lathe so I could grind/polish the female taper of the chucks would be a real challenge for me. Would mounting a rod in each chuck (which would be a MT5 alignment bar be safe? I am real leery of just that MT5 taper holding such a contraption in place securely without coming loose and bounding across the floor of my garage and bouncing off of my vehicles. So is there a better/safer way to do this?

It's easy. Polish with sandpaper/emery cloth. Not cutting forces involved.

First, chuck up a shaft.


Second, clamp the bad chuck onto the shaft.


It looks sketchy, I know. And it would be, if you tried turning or facing. But for just polishing inside the taper with emery cloth, it works fine. Just remove the camlock studs so ya don't break a finger.

It takes some work, you have to keep pulling it apart and test fitting. But once it fits, it fits forever.




To answer your question. No, definitely don't attach a chuck to a test bar that's only held inside the spindle taper.

If that's all you have to work with, run the test bar all the way through the bad chuck, so you can get at it with a tailstock center. A tailstock live center securing the end of the bar would be prudent, to prevent anything from coming loose. You just wouldn't have as much room inside the taper to work with.

 

[Ken226]

@Tired&Retired

I just want to clarify something.

When you say you have a gap of .002" to .008", how much approximate torque do you have the 3 spindle cams tightened to?

When a chuck is placed onto a properly manufactured, in-spec, d1-4 spindle, loosely, there should be about a .001 to .002" gap between the spindle face and chuck.

I have mine set up with about a .001 to .002" gap when loose. When the cams are tightened to about 20 ft lbs, the gap disappears. Some chucks take a little more than others.

 

[mikey]

I described exactly what I did to Matt, and he is OK with it. Heck, I dunno, but isn't there some difference between "grinding" and "polishing"? Spindle speed was at the lowest setting on the lathe, which I think is 40 to 50 rpm. As for time I held that 3000 grit rod to the spindle taper, no more than counting to 10, then looking at the finish. When I say it was at 7 degrees, that is + or - a hair. I lined up the rod with the spindle taper as best I could by eyeball and feel, as it was being held in a drill chuck mounted on my compound slide. Then looked at what the indicator on the compound slide showed and it was 7 degrees. As for it being exactly 7 degrees, etc, or 7.125 degrees, heck, I don't know. I don't think I have anything that could actually measure to that precision here.

Are you all forgetting this is hobbyist level, and I am posting this in a "hobby-machinist" forum? I guess my wife "said" it best with her expression when I told her that I wanted the lathe to be better than one thousandth of an inch tolerance when I showed her a 0.0015" feeler gauge and I wanted it BETTER than that. That was the "are you serious" look. LOL!

Yeah, I want the stuff I work with to be as accurate as reasonably possible, and will make reasonable efforts in that direction. But for someone(s) to be basically claiming that I ruined my lathe with a 3000 grit polishing stone on a hardened surface with minimal (and I do mean MINIMAL) contact duration and pressure, well, sorry, we are not talking on the save wavelength. 3000 grit doesn't remove all that much material even with a lot of elbow grease. I used to polish a lot of stuff in the past. I know the value of a light touch instead of getting TOO aggressive.

Anyway, Matt has no problems with what I described here and to him. He actually advised me to be MORE aggressive on the GRINDING of the spindle nose taper. And if that DOES ruin the spindle, he will send me a free replacement. So I don't have a lot to loose except perhaps not knowing what sort of headache I would be in for to replace the spindle, of course.

But quite honestly, I am thinking that what are the chances that I would be able to polish/grind the spindle taper and get all of my chucks to fit flush with the spindle face AND the spindle taper, when the gap I am seeing on four chucks is 0.002", 0.004", 0.006", and 0.008"? I don't see how I could do that with ALL of the chucks by addressing the spindle nose taper. Or am I missing something here?

Might it not actually be smarter for me to address each and every chuck and polish/grind THEM to get each one to fit as precisely as I am able?

Of course, mounting them on the lathe so I could grind/polish the female taper of the chucks would be a real challenge for me. Would mounting a rod in each chuck (which would be a MT5 alignment bar be safe? I am real leery of just that MT5 taper holding such a contraption in place securely without coming loose and bounding across the floor of my garage and bouncing off of my vehicles. So is there a better/safer way to do this?

Yes, I understand this is a hobbyist site and that you're a hobbyist. So am I. Speaking only for myself, I was trying to help you to understand a few things:

• It is important to understand what you're measuring and how you measure it so that you know where you are and if you have an issue or not. Making a diagnosis is important, especially for a hobby guy who doesn't have tons of money to throw around. I offered to walk you through the process and you chose to ignore it, which is totally fine but, well, here we are.
• It is important to know which things are critical, like the integrity of the spindle taper, and which things are not, like having the chuck touch the surface of the spindle face when the chuck is fully locked down. On lathes with precision spindles that utilize top tier chucks the back of the chuck mount usually does contact the spindle face when the chuck is locked down but not always. I currently have 6 high end chucks and all of them contact the face of my spindle. I have one Chinese ER-40 chuck that is accurate as hell but it does not touch the spindle face when it is locked down; it still has 0.0001" TIR and I don't care that it doesn't touch the spindle face.
• A D1-4 spindle has a specific taper that allows any D1-4 chuck with a matching taper to mount accurately. In order for that to happen, the taper MUST be accurate; if it is off then the chucks will not fit properly. Can you get a chuck to fit a taper that is off? Yes, you can. Will that chuck move under load? Probably. Enough to matter? Dunno. Should you now begin to modify your chuck tapers to fit your modified spindle in the hopes that they will fit? That's a hole that I would not like to step into.

Here is my best advice to you, and I mean it with helping you foremost in mind. I would stop what you're doing and replace the spindle. Do not modify your chuck tapers because there is a good chance they have an accurate female taper at this point and it is likely they will work fine on an accurate spindle taper.

In my opinion, it was a mistake to grind that spindle. Matt is complicit in this and I hope he makes good by sending you a replacement spindle because it should have been good in the first place.

 

[Just for fun]

Are all your chucks bad? That doesn't seem right to me. I don't know jack really, so just thinking out loud. But to me you were on the right track with the Spindle nose taper being the culprit.

 

[Ken226]

Are all your chucks bad? That doesn't seem right to me. I don't know jack really, so just thinking out loud. But to me you were on the right track with the Spindle nose taper being the culprit.

I have a suspicion that there may be nothing at all wrong with the spindle, possibly the chucks either. I was hoping to hear back about the cam torque question I asked earlier.

The probability of the spindle being out of spec, but giving such a drastic spread of gaps (.002"-.008"), on so many chucks, is very low. If the spindle was out of spec, the gap would be similar on most, or all of these chucks.

I knew a fellow once who had a similar problem with a new grizzly g4003. I went over to his house, and quickly realized what the problem was. He put the chuck on the spindle and, turned the cams clockwise untill he felt resistance. Zero torque, just turned them till they stopped.

Needless to say, he had non-repeatable runout issues, and a gap.

 

[Tired&Retired]

@Tired&Retired

I just want to clarify something.

When you say you have a gap of .002" to .008", how much approximate torque do you have the 3 spindle cams tightened to?

When a chuck is placed onto a properly manufactured, in-spec, d1-4 spindle, loosely, there should be about a .001 to .002" gap between the spindle face and chuck.

I have mine set up with about a .001 to .002" gap when loose. When the cams are tightened to about 20 ft lbs, the gap disappears. Some chucks take a little more than others.

If you watched the video I included earlier, I showed the procedure I used with all of the chucks I tested. I first turned the camlocks to just grab the chuck in place, then I went around all three in sequence gradually tightening them until they were "grunt" tight. Sure I have torque wrenches, but do you think that would make any difference? I am no hercules, but I think I put pretty good tugs on those camlocks. Even if torqueing the camlocks down to something like 50 ft/lbs would bring the two faces together, is it really such a good idea putting that much torque on those camlocks?

And btw, the chuck with the biggest gap (0.008") is actually the 4 jaw chuck that I believe is Taiwanese made that I bought from Matt when I bought the lathe. Which I would have though would have been the best of the bunch. And for the record, even though I believe I may have mentioned it before, with every chuck, the camlock indicators are all pretty much in the center of the arrow indicators on the spindle. The closest gap is on the 3 jaw chuck that came mounted on the lathe when I received it.

Anyway, here is the video again so you don't have to go back through this thread to find it ->

At timestamp ~2:00 I torque down the first chuck so you can see the procedure I used on all of them. I tightened the camlocks until they would not tighten any more and then used the feeler gauges to measure the gap.

 

[Ken226]

Even if torqueing the camlocks down to something like 50 ft/lbs would bring the two faces together, is it really such a good idea putting that much torque on those camlocks?

I did see your procedure in the video, it's just difficult to tell how much force someone is applying in a video. I didn't intend to come off as insulting, just trying to help.

Just based on what I could see in the video, I suspect I may apply a good bit more torque to my cams than you are. But, it's hard to tell.

I agree that 50 ft lbs would be abnormal, but it's not unheard-of. 25-30 is the norm.

This is an old thread, but has some discussion on the subject.

Torque Needed For D1-4 Cam Lock?

I have been working diligently on the used G4003 lathe that I bought a month or so ago. I still haven't made a cut with it, but it's getting closer. I need to start a thread on the project I've made out of it (teardown, repaint, rebuild, adjustment, refinement). Anyway, I put the 3 jaw...

www.hobby-machinist.com

I've had them require that much in the past, which is when I mounted the chuck backwards on a rod, dyekem the taper, and hold emery cloth against the taper with my fingers untill the dyekem was well gone, then re-tested the fit.


The square sockets in the cams will take a 3/8" drive extension. Perhaps grab a torque wrench and try it, see if 25-30 ft lbs helps at all.

I'll check mine right quick and post back the results.

Edited to add:

I tried 5 chucks. All of my well used old chucks (4 of them) pulled tight @ about 20 ft lbs. A new 6 jaw took 28.

All of them except the Kalamazoo 3 jaw have been mounted backwards on a shaft and had the tapers lightly sanded to get them to the state of fitment they are currently in.

 

[Tired&Retired]

For the record I didn't try the feeler gauge tests until I had tightened down the chucks as tight as I could get them by hand. So I don't know the gap on a loosely attached chuck on my spindle. Honestly, I didn't think it would be pertinent. For instance, if I were getting 0.008" of a gap with my 4 jaw chuck tightened down as tight as I can by hand, what would it matter what the measurement is with the camlocks barely engaged?

BTW, I did put Dykem on the spindle taper when I first started talking to Matt about this, and I believe I used the 3 jaw chuck at the time. There was just a very small wear ring at the back of the taper where the chuck apparently was engaging the taper. Sorry, I didn't think to take any pics of that at the time. The 3 jaw chuck appears to be the closest one to being fitted properly to the spindle, as it there is only 0.002" gap at one part of the contact area. Which perhaps you are right, that just tightening the camlocks further would snug it right up. But seems to me that the 4 jaw chuck with that 0.008" gap would need a LOT of convincing to snug up. I would hate to have to use a jackhammer to then break it loose from the spindle.

 

[Ken226]

But seems to me that the 4 jaw chuck with that 0.008" gap would need a LOT of convincing to snug up. I would hate to have to use a jackhammer to then break it loose from the spindle.

Yea, I suspect that one is going to be a bit of work, but totally doable. It takes very little material removal on the taper to get a big movement along the Z axis.

It's the same spindle, your mounting each of the chucks too. That the gap is different for each chuck strongly implies that the chucks are what vary in size. Even if the spindle is a on the MMC (max material condition) side of the tolerance, the chucks are clearly not all the same size.

The chucks will be the easiest to adjust.

For example, opening the chucks taper diameter by .002" will move the chuck .008" closer to the spindle.

Here's the calculation:

Tangent(7.125)(.008)(2)=.001999

Where 7.125° is the taper angle, .008" is the distance you need to move the chuck and (2) converts it from radius to diameter.

The chuck that's only .002" from fitting, would only need the diameter opened up by .0005". You could accomplish that with about 5-10 second of polishing with 220 grit.

Tangent(7.125)(.002)(2)=.000499