do you test your lathe's precision
- Thread starter Adonisy
- Start date
A few thoughts
First, please remember that I am not recommending that you start doing any of these things to your lathe without further research!
The first question is how are you testing run out? You need precision ground stock and it needs to be carefully placed in a clean deburred chuck. Then I take my measurements one inch from the chuck just to have a consistent test point. If your test equipment or procedure isn't up to the task you will get false readings.
Some lathes have adjustments to take lash(play) out of the spindle bearings, I suspect that the cuesmith doesn't. If not, the only option is better quality bearings, which can run into many dollars fast and may or may not improve your runout problem.
It may be possible to adjust how true the chuck is on the spindle, I don't know how the cuesmith chuck is attached. I am almost positive that the cuesmith uses soft jaws in the chuck so another option if the lathe is running off true rather than just having slack in the spindle bearings, is to take a very light pass on the inside of the jaws, truing them.
Do you have the two chuck lathe? You might try chucking in just the front and just the rear chuck and see which runs truer. Swapping the more accurate chuck to the front might be an option. Chris does mention only chucking in one chuck for best accuracy.
Using the cigarette paper trick or the steady rest when you need less run out may also be options.
Although you want your lathe to run as true as possible, don't get too wrapped up in this. For run out of about a half a thousandth guaranteed you are looking at about a $17,000 to $30,000 lathe in US dollars. When I trued my Jet metal lathe, cut a custom backing plate true with the lathe, and installed a new Bison eight inch chuck I found my total repeatability and runout was around .0015. A check of specifications showed me that all components were within tolerances, barely.
Hu
First, please remember that I am not recommending that you start doing any of these things to your lathe without further research!
The first question is how are you testing run out? You need precision ground stock and it needs to be carefully placed in a clean deburred chuck. Then I take my measurements one inch from the chuck just to have a consistent test point. If your test equipment or procedure isn't up to the task you will get false readings.
Some lathes have adjustments to take lash(play) out of the spindle bearings, I suspect that the cuesmith doesn't. If not, the only option is better quality bearings, which can run into many dollars fast and may or may not improve your runout problem.
It may be possible to adjust how true the chuck is on the spindle, I don't know how the cuesmith chuck is attached. I am almost positive that the cuesmith uses soft jaws in the chuck so another option if the lathe is running off true rather than just having slack in the spindle bearings, is to take a very light pass on the inside of the jaws, truing them.
Do you have the two chuck lathe? You might try chucking in just the front and just the rear chuck and see which runs truer. Swapping the more accurate chuck to the front might be an option. Chris does mention only chucking in one chuck for best accuracy.
Using the cigarette paper trick or the steady rest when you need less run out may also be options.
Although you want your lathe to run as true as possible, don't get too wrapped up in this. For run out of about a half a thousandth guaranteed you are looking at about a $17,000 to $30,000 lathe in US dollars. When I trued my Jet metal lathe, cut a custom backing plate true with the lathe, and installed a new Bison eight inch chuck I found my total repeatability and runout was around .0015. A check of specifications showed me that all components were within tolerances, barely.
Hu
Adonisy said:
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I usually say my chucks will turn within .002" total run out. What I mean when I say that is that your dial indicator needle only moves .002" total. Now when most manufacturers say their chucks will only have .002" total run out theat means it could move your dial indicator needle .004". So if your Bison chuck moved your needle .0015" it really only had .00075" total run out. Those that guarantee .0005" run out could move the needle .001" and still be within tolerances. If I were to say my chucks turn within .001" I would be telling the truth, but customers would think it had double that because it moves the needle .002". It is the same pricipal as removing material with a lathe. When you dial in .001" it takes off .002" because of the rotation. Your dowel pin being .001" off center will move the needle .002" because of the rotation. I will continue to say .002" when asked because that is how it will be perceived. But when buying metal lathes remember what they are saying in their specs is it can move the needle twice the amount of the number they are rating it at. If one of my chucks moves the needle on a 1/2" ground dowel pin more than .002" once chucked correctly it should be able to be trued up by touching up the jaws with a boring bar.ShootingArts said:
My Logan lathe and Bison 6-jaw chuck can get less than half a thou of runout.
I use a half-inch precision drill rod to indicate.
I use a half-inch precision drill rod to indicate.
Adonisy said:
I have Buck Adjust-tru chucks for and aft on my lathe. Dead nuts every time.
JoeyInCali said:
I have about 80 unbrako dowel pins that are 3/8 x 2-1/2, and those things are hard as a rock. I put one in the chuck ,and by eye It looks like It chucked up dead on the first time. Fixing to head out right now, but I'll indicate It later and see how far off the eyeballing was
.
you are right about the indicator of course
Chris you are right about the indicator of course. My dial indicator showed three thousandths movement. It was worse than that. I spent several hours one morning turning a shoulder on my backing plate that gave a slight interference fit to install the new chuck. It was way out then, with the indicator showing six or eight thousandths. I had to take the chuck back off the backing plate, a bear in itself, and turn down my carefully cut shoulder.
Then I started on the part that will make you shiver since you just sold me one of your lathes. I snugged up the bolts holding the chuck to the backing plate and put a piece of one inch drill rod in and started indicating and using a five pound dead blow hammer to adjust on the chuck until I got my minimum run out of about .001. The chuck wasn't 100% repeatable either, costing about another .0005 if I had to take a part in and out of the lathe even though I always index everything.
By the way, what size hammer do you recommend to adjust your lathe?
Hu
Chris you are right about the indicator of course. My dial indicator showed three thousandths movement. It was worse than that. I spent several hours one morning turning a shoulder on my backing plate that gave a slight interference fit to install the new chuck. It was way out then, with the indicator showing six or eight thousandths. I had to take the chuck back off the backing plate, a bear in itself, and turn down my carefully cut shoulder.
Then I started on the part that will make you shiver since you just sold me one of your lathes. I snugged up the bolts holding the chuck to the backing plate and put a piece of one inch drill rod in and started indicating and using a five pound dead blow hammer to adjust on the chuck until I got my minimum run out of about .001. The chuck wasn't 100% repeatable either, costing about another .0005 if I had to take a part in and out of the lathe even though I always index everything.
By the way, what size hammer do you recommend to adjust your lathe?
Hu
ShootingArts said:Chris you are right about the indicator of course. My dial indicator showed three thousandths movement. It was worse than that. I spent several hours one morning turning a shoulder on my backing plate that gave a slight interference fit to install the new chuck. It was way out then, with the indicator showing six or eight thousandths. I had to take the chuck back off the backing plate, a bear in itself, and turn down my carefully cut shoulder.
Then I started on the part that will make you shiver since you just sold me one of your lathes. I snugged up the bolts holding the chuck to the backing plate and put a piece of one inch drill rod in and started indicating and using a five pound dead blow hammer to adjust on the chuck until I got my minimum run out of about .001. The chuck wasn't 100% repeatable either, costing about another .0005 if I had to take a part in and out of the lathe even though I always index everything.
By the way, what size hammer do you recommend to adjust your lathe?
Hu
Sounds like you started off in the right direction and then did everything wrong from then on. If you got it to run truer using a hammer then what you have probably done is ruin the spindle. When installing a backing plate onto a spindle you want everything perfectly clean. You then bore your registration coller on the backing plate for an exact fit. This is for repeatability so if you ever take off that plate it can be put back on perfectly. Once this backing plate is installed on the spindle it needs to be trued in all directions by the tool cutter on that lathe. With the lathe running you make a passes across the face of the plate until it is running dead nuts true. This will insure the chuck is mounted at a perfect 90 degree angle from the bed of the lathe and carriage. Once this is done you cut a offset that perfectly fits the back of the chuck so that the chuck when mounted runs concentric with the spindle. You then clean up the rest of the backing plate to balance the chuck and plate.
You now have a chuck running as true as possible for the lathe and chucks specs. If the spindle bearings have play or if there is excessive runout in the chuck then of coarse you will have that to deal with. If the chucks jaws are not running true to each other then you can run a toolpost grinder or if they are soft jaws then an endmill to true them up somewhat. Often, the jaws in a lathe will not be true even though the chuck is fairly new. If you tighten down on something out near the edge of the jaws they can be scewed slightly which can ruin them for any precise work. The quality of a chuck has a lot to do with how accurite they are. There is a reason that the same size chuck may cost anywhere from 50.00 to a 1000.00
Dick
didn't hurt a thing
I can't resist harassing Chris a little. It is a bit of a running joke after I claimed I was going to take a hammer to my Cuesmith Deluxe to correct a minor problem that occurred in shipping.
With the Jet, I measured spindle runout and then mounted a D1-4 backing plate on it indexed to minimize runout. I cut the face down and left a shoulder pretty much as you describe. (the chuck had a big enough bore I left an inside shoulder.) The new chuck came with a used lathe I bought but was new in box, never been mounted. I didn't realize that it was a low end chuck since the same company makes some pretty decent chucks. When I found the run out was totally unacceptable, far worse than my stock Jet chuck, I did a little homework and found it wasn't much of a chuck. However it was what I had and I needed it for a particular job I needed to get out. So what I did was turn down my shoulder on the backing plate a few thousandths and bolt the chuck back on leaving the bolts just snug. All that was required to move it around was a bump, the five pound deadblow hammer was just the deadblow hammer that was handy, a two pounder or lighter would have worked just fine.
A first time for everything but I have trued many an assembly by the turn and bump method and have yet to damage one.
Hu
I can't resist harassing Chris a little. It is a bit of a running joke after I claimed I was going to take a hammer to my Cuesmith Deluxe to correct a minor problem that occurred in shipping.
With the Jet, I measured spindle runout and then mounted a D1-4 backing plate on it indexed to minimize runout. I cut the face down and left a shoulder pretty much as you describe. (the chuck had a big enough bore I left an inside shoulder.) The new chuck came with a used lathe I bought but was new in box, never been mounted. I didn't realize that it was a low end chuck since the same company makes some pretty decent chucks. When I found the run out was totally unacceptable, far worse than my stock Jet chuck, I did a little homework and found it wasn't much of a chuck. However it was what I had and I needed it for a particular job I needed to get out. So what I did was turn down my shoulder on the backing plate a few thousandths and bolt the chuck back on leaving the bolts just snug. All that was required to move it around was a bump, the five pound deadblow hammer was just the deadblow hammer that was handy, a two pounder or lighter would have worked just fine.
A first time for everything but I have trued many an assembly by the turn and bump method and have yet to damage one.
Hu
rhncue said:
A 10 pound sledge hammer will solve all problems and promptly eliminate all warranty and relieve all desire to build cues.ShootingArts said:Chris you are right about the indicator of course. My dial indicator showed three thousandths movement. It was worse than that. I spent several hours one morning turning a shoulder on my backing plate that gave a slight interference fit to install the new chuck. It was way out then, with the indicator showing six or eight thousandths. I had to take the chuck back off the backing plate, a bear in itself, and turn down my carefully cut shoulder.
Then I started on the part that will make you shiver since you just sold me one of your lathes. I snugged up the bolts holding the chuck to the backing plate and put a piece of one inch drill rod in and started indicating and using a five pound dead blow hammer to adjust on the chuck until I got my minimum run out of about .001. The chuck wasn't 100% repeatable either, costing about another .0005 if I had to take a part in and out of the lathe even though I always index everything.
By the way, what size hammer do you recommend to adjust your lathe?
Hu
might give that a try!
Chris,
After I try building a few cues I may give that a try too! Right now I am into fine adjustments on it so the four pound mallet seems adequate.
Hu
Chris,
After I try building a few cues I may give that a try too! Right now I am into fine adjustments on it so the four pound mallet seems adequate.
Hu
cueman said:A 10 pound sledge hammer will solve all problems and promptly eliminate all warranty and relieve all desire to build cues.
running true
I also use a hardened dowel pin to check my chuck on my old southbend. It read almost .005 total indicator travel! The backing plate was true, so I had to hone two jaws to get it to run true. It is slow and tedious, but I did get it to within .001 in maybe an hour. It seems quite repeateble as well. I do not recommend that anyone hand hone parts unless you have patience, and make sure that the pressure and cutting action is carefully applied. Soft jaws like some of the dedicated cue lathes use should be a snap to true up.
Of course another solution for cues is to use custom collets indicated to one jaw. You can eliminate all wobble by making your own collets out of nylon or delrin.
I also use a hardened dowel pin to check my chuck on my old southbend. It read almost .005 total indicator travel! The backing plate was true, so I had to hone two jaws to get it to run true. It is slow and tedious, but I did get it to within .001 in maybe an hour. It seems quite repeateble as well. I do not recommend that anyone hand hone parts unless you have patience, and make sure that the pressure and cutting action is carefully applied. Soft jaws like some of the dedicated cue lathes use should be a snap to true up.
Of course another solution for cues is to use custom collets indicated to one jaw. You can eliminate all wobble by making your own collets out of nylon or delrin.
good idea about the custom collets
That is a good idea about the indexed collets. I may have to make some if I don't like runout after I test. Not practical for my general purpose lathe but would work great on the Cuesmith if needed. I'm not actually expecting any problems though.
The jaw honing idea is worth remembering for my other lathes too. I have spent a lot of time honing on gun parts though and know you can put in a lot of unfun hours with a stone!
Hu
That is a good idea about the indexed collets. I may have to make some if I don't like runout after I test. Not practical for my general purpose lathe but would work great on the Cuesmith if needed. I'm not actually expecting any problems though.
The jaw honing idea is worth remembering for my other lathes too. I have spent a lot of time honing on gun parts though and know you can put in a lot of unfun hours with a stone!
Hu
olsonsview said:
just remember
The accuracy you get by honeing is really only at the diameter of drill rod you test with. It may be better or worse at different openings with a scroll chuck. Though a bad chuck is usually at least somewhat improved at all the settings with a careful honing. I just test at the diameter i will be working with mostly, in my case a shaft. I like that as accurate as possible.
The accuracy you get by honeing is really only at the diameter of drill rod you test with. It may be better or worse at different openings with a scroll chuck. Though a bad chuck is usually at least somewhat improved at all the settings with a careful honing. I just test at the diameter i will be working with mostly, in my case a shaft. I like that as accurate as possible.