Source of runout on chuck

adamsgt

adamsgt

Jerry Adams
After assembling and mounting my set tru chuck I put a piece of brass round in the chuck and had too much run out that could be handled by the set tru feature. So I removed the chuck body from the back plate, mounted the back plate and spun it with a dial indicator. Now, I just placed the tip of the indicator in the bearing surface of the back plate and rotated the back plate noting the low to high readings. There was a difference of .0115. That implies that I would have to take of about .000575 from the surface of the backplate. Does that sound like the correct method and does the amount sound excessive. Just to check I had another larger back plate and mounted it. It showed .009 low to high. So, does that imply that the face of the spindle is out? On this lathe, for some reason, the threading dial is mounted on the left side of the saddle. This limits how close I can get the carriage to the spindle. I had been using a tool post mounted indicator to do the initial measurements but can't reach the spindle with it. Finally removed the threading dial but the spindle was still out of reach for the tool post mounted indicator. Tried to set up a dial indicator on a mag base on the carriage but couldn't seem to get all the parts connected properly. Not sure if I'm missing pieces or knowledge or both. I thought I knew what to do until I tried it. So far I can't find anything in the books that I have that details methods for using and setting up dial indicators. Time to hit you tube and the web for help on that.
 
Chuck

Second what Butch states. Turn your face plate cut just what ya need too. Also mark your relationship chuck to back plate and backplate to spindle cams. That way when you dissemble to clean it all goes back together the same way.
 
I would check the spindle first. Use a magnetic base and put the base anywhere close to the spindle. Check it without any chuck or face plate mounted. If that's ok then the mtg plate is out. If your spindle is a D spindle make sure the pins are installed into the plate properly. A lot of plates have pins that are too long and bottom out in the spindle bores. If all is well with the spindle and the mounting plate , then, cut it. Always find why it's out before cutting away at chucks and mounting plates.

From what you are saying you have the chuck off center as far as it can be and you still have runout. That's a bunch.
 
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How much you can adjust the "set true" feature is determined by how much clearance you have between the male and female portion of the chuck mounting plate. I may be wrong, but I think about .015 is about normal.

You don't want much more than this because remember, the set true feature results in the entire chuck running out on the Lathe, resulting in vibration, depending on how much you have to kick it off to make the piece run true, and the RPM of the spindle.
 
Butch Lambert said:
Did you turn the face of your chuck adapter first?
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No I didn't. I wanted to see what I had before taking off any metal. I'm concerned that after checking the run out it appears to be too much. When I was checking against the brass rod I had chucked up I got about .020 run out. I didn't expect that much and was more than a little disconcerted. But I have no experience at doing this, so I don't know what is reasonable and how much I can safely take off the back plate. As it comes, the mating surface of the back plate appears to be only about the outer third of the face. Is it designed that way on purpose to allow more metal to be removed as necessary? Again, would .006 be an excessive amount or is it in a normal range?

The skills that I had in setting up dial indicators seem to have evaporated through non-use over the years so I've got another learning curve to climb. Last night while trying to get to sleep the thought came to me, "dummy, you could have just rotated the compound ninety degrees to use the tool post mounted indicator." The thread dial being on the left side of the saddle has been an impediment when trying to do things close to the head stock. I finally took it off as I need to get closer to the head stock for another task. I bought off ebay a lathe dog plate to use when turning between centers. However I discovered that the hole was not quite large enough to allow the 5MT center to fully seat in the spindle. So I have to bore that out a bit. Seems like it always something
 
jackie schmidt said:
How much you can adjust the "set true" feature is determined by how much clearance you have between the male and female portion of the chuck mounting plate. I may be wrong, but I think about .015 is about normal.

You don't want much more than this because remember, the set true feature results in the entire chuck running out on the Lathe, resulting in vibration, depending on how much you have to kick it off to make the piece run true, and the RPM of the spindle.
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From what I saw when I originally tried to take out the run out it looked like the range of adjustment was more in the .005 range. Before I go any further I think I'll mount the chuck that came with the lathe and see what it shows. I don't remember it bring near this bad.
 
adamsgt said:
From what I saw when I originally tried to take out the run out it looked like the range of adjustment was more in the .005 range. Before I go any further I think I'll mount the chuck that came with the lathe and see what it shows. I don't remember it bring near this bad.
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Jerry, let me strongly suggest that before making any cuts or modifications of any kind to your lathe or chuck, get someone to help you with it, someone familiar with both the machine and the Bison chuck. I don't have time right now to come to you but if you'll drive out to Odessa soon, I can show you what you need to know in no time at all. There's nothing like one on one instruction with the actual aircraft (oops, machine) you'll be flying (oops again). Don't you agree? :p

How 'bout driving out this afternoon? You can go home tomorrow evening.

Gene
 
Gene Beggs said:
Jerry, let me strongly suggest that before making any cuts or modifications of any kind to your lathe or chuck, get someone to help you with it, someone familiar with both the machine and the Bison chuck. I don't have time right now to come to you but if you'll drive out to Odessa soon, I can show you what you need to know in no time at all. There's nothing like one on one instruction with the actual aircraft (oops, machine) you'll be flying (oops again). Don't you agree? :p

How 'bout driving out this afternoon? You can go home tomorrow evening.

Gene
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Thanks Gene, I have no intention of removing any metal on this chuck until I am sure of what I'm doing. Discussed this with my Friday Posse lunch bunch and got some suggestions to follow. I'm scheduled for a Myelogram on Wednesday to investigate the source of debilitating lower back pain so a long road trip isn't in the cards right now. In the meantime I can do a lot of investigating and measuring until I learn more about what's going on. I would like to come out to your place after the end of May and my back is better. Thank goodness this is only a 6 1/4 inch 3 jaw chuck. Right now I wouldn't want to be manhandling that big six jaw chuck on your lathe. ;)
 
Bison

My set true is a Bison 8". The backing plate for this chuck is not meant to be turned before mounting the chuck, that's why it costs what it does. My chuck is perfect, whichever way I check it it is always bang on. Maybe remove it and check the lathe first.
 
Butch Lambert said:
Ian,
Sounds like you have the same as I, but I think the backing plate will always need a light truing cut.
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Butch, maybe there are those that do not understand that the "set true" feature of these chucks affects only the radial runout. It has nothing to do with how square a check is when mounted on the Lathe spindle.

On ours, we take the backing plate off, mount it on the Lathe, (cam lock), match marked it, and then take a light skin over the face so the church body will run square when mounted on that Lathe's spindle.
 
jackie schmidt said:
Butch, maybe there are those that do not understand that the "set true" feature of these chucks affects only the radial runout. It has nothing to do with how square a check is when mounted on the Lathe spindle.

On ours, we take the backing plate off, mount it on the Lathe, (cam lock), match marked it, and then take a light skin over the face so the church body will run square when mounted on that Lathe's spindle.
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You are correct Jackie. I also have a 3jaw set tru on my 10EE Monarch.
 
I've been getting some help on the Home shop Machinist web site. One suggestion was to use a feeler gauge to check for clearance between the back plate and the spindle. When I did this I got .002 to .012 difference.This implies that the plate was askew. So, I used Prussian blue on the back plate to check for contact. This revealed full contact on the hub of the spindle but nothing on the face of the spindle. I got the same results using a lathe dog plate I had. So it appears that the spindle hub is a tad oversize for the plates. I'm in the process of trying and measuring everything I have that mounts on the lathe to see if this is consistent.
 
adamsgt said:
I've been getting some help on the Home shop Machinist web site. One suggestion was to use a feeler gauge to check for clearance between the back plate and the spindle. When I did this I got .002 to .012 difference.This implies that the plate was askew. So, I used Prussian blue on the back plate to check for contact. This revealed full contact on the hub of the spindle but nothing on the face of the spindle. I got the same results using a lathe dog plate I had. So it appears that the spindle hub is a tad oversize for the plates. I'm in the process of trying and measuring everything I have that mounts on the lathe to see if this is consistent.
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Hi Jerry
Glad to hear you're becoming more familiar with your lathe and Bison adjust-tru chuck. I still don't think you are on the right track and strongly suggest that you don't make any cuts on the lathe spindle or on the chuck until someone who is familiar with it has looked at them. You may not wish to continue our exchanges here on the forum and if so, you have my e-mail address. I'll be here to help.

We have a club match in Midland Saturday, why not drive out Friday and shoot with us on Saturday What do you say? :p

Later, Gene Beggs
 
Gene Beggs said:
Hi Jerry
Glad to hear you're becoming more familiar with your lathe and Bison adjust-tru chuck. I still don't think you are on the right track and strongly suggest that you don't make any cuts on the lathe spindle or on the chuck until someone who is familiar with it has looked at them. You may not wish to continue our exchanges here on the forum and if so, you have my e-mail address. I'll be here to help.

We have a club match in Midland Saturday, why not drive out Friday and shoot with us on Saturday What do you say? :p

Later, Gene Beggs
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I'm still not ready to cut anything. I have been scouring the web for info and came across a thread on Practical Machinist that was posted in 2008 where the person had the same exact problem as I do. You say that I'm not on the right track. What would you suggest is the right track? What I know for sure is that the back plate will not fully mount on the spindle. The cam lock bolts give the right indications of locking with the index between the 2 V"s as they're supposed to. I installed cam lock pins on a generic back plate and adjusted the pins on the lathe dog plate I had. I learned that there is only one rotation of the pin that will work I get the same indications with two other D1-4 back plates. On one try I really tightened the cam lock bolts on the Bison. Had a helluva time getting the plate off after that. Felt like it was really wedged onto the spindle. One thing I haven't tried yet is to remove the camlock pins and check the fit that way. I don't think that would prove anything though as the purpose of the pins is to pull the plate onto the spindle. I also have two other chucks that I haven't measured yet. There's one guy who usually shows up for our Friday lunch that is well versed in machinery and if he shows tomorrow I'll put the problem to him and see what he thinks.
 
Take a stone and lightly run it around the taper on the spindle nose to look for any dings or high spots. Then do the spindle face. If you find any, gently work them down. Something is not right here, but it is very unlikely, though not impossible that your spindle taper is slightly oversize. That's like getting an engine with an oversize piston or something.
 
James Lederer said:
Take a stone and lightly run it around the taper on the spindle nose to look for any dings or high spots. Then do the spindle face. If you find any, gently work them down. Something is not right here, but it is very unlikely, though not impossible that your spindle taper is slightly oversize. That's like getting an engine with an oversize piston or something.
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After my previous post I had to go by my shop so I decided to play around with the cam lock pins. I tried rotating the pins to see how close I could get the bolt index marks to the same position. I did get better results in that the gap was not present all around the joint and was not larger than .005. While an improvement, it's still too much. I'm going to explore this some more another time. My shop has no HVAC and my sweat was dripping on too many metal things. I did try the 3 jaw that came with the lathe and It mounted with no gap at all. However, that's not saying much because looking at the recess of that chuck doesn't reveal any precision machining. A guy emailed me a pdf of ISO 702-2 which contains the connecting dimensions for spindle noses of camlock chucks. At least I've got some standard to compare measurements against.
 
Check the pins

Check the pins. I'd bet the pins are too long. Bison is known for that. If the pins are too long the chuck will never pull up tight to the face of the spindle. This ain't rocket science, guys.

Take the pins out one at a time and check them in their proper hole and see if the locking cam turns past the register marks. If it does not, then the pin is too long.

The adapter registers on the taper and is tight to the large surface of the spindle, not the front surface of the spindle taper. Usually there is a gap between the taper nose and the recess in the chuck. If there is no gap and the chuck is bottoming out on the spindle taper nose, you have other problems.
 
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TRA said:
Check the pins. I'd bet the pins are too long. Bison is known for that. If the pins are too long the chuck will never pull up tight to the face of the spindle. This ain't rocket science, guys.

Take the pins out one at a time and check them in their proper hole and see if the locking cam turns past the register marks. If it does not, then the pin is too long.

The adapter registers on the taper and is tight to the large surface of the spindle, not the front surface of the spindle taper. Usually there is a gap between the taper nose and the recess in the chuck. If there is no gap and the chuck is bottoming out on the spindle taper nose, you have other problems.
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Good point. We have ran into that more than once on a new chuck. Also, we had one new chuck that pins were clocked too far in, and the cam locks would barely engage.

All of these dimensions are supposed to be set to industry standards, but the occasional mess up does get through QC.
 
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