5c collet chuck

Ok. I never ass u me any thing. Hard fact, the spindle has no measurable run out! Hard fact there is no light from around the spindle to back plate joint. Hard fact, there is no light gap between the chuck to back plate from an 850 lumin nitecore flash light. There is no measurable run out on the back plate. Now with these accual measurements on the back plate, lathe spindle and back plate, with multiple quality instruments. I now have the chuck off the back plate and have it in the house heated garage. I plan to use my granite surface plate and Sterrett. .0001 DTI and stand to check back to ground surfaces on the chuck nose and front shoulder. Now if I find the chuck out of parallel should I have the back presicision ground . I don’t think it can be turned true has the chuck is hardended from what I can tell it is about 50-55 Rc by file test. Plus I don’t trust the collets.

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Quick way to check back surface. Grab yourself a pair of parallels and measure them to see what they are in parallelism. Get your best pair and layout so they go the same way if not the same end to end. Then put the chuck on them, take your gauge and measure the chuck mounting surface. Take note of your parallels variances into consideration if not perfect.
 
Cadillac said:
Quick way to check back surface. Grab yourself a pair of parallels and measure them to see what they are in parallelism. Get your best pair and layout so they go the same way if not the same end to end. Then put the chuck on them, take your gauge and measure the chuck mounting surface. Take note of your parallels variances into consideration if not perfect.
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Yea I did that just did not take a pic. Every thing is parralle, front to back. I think I found the problem. The bolts used on the chuck to back plate are 5/16” threads and the shank is about 9.they fit tight in the hole on the chuck. When they tighten down one slitely off center and pushing the chuck off center off line with the spindle. This is a front through hole chuck mount and the back plate is threaded. So need a little room in through holes to align before locking it down. My idea is to turn down the shanks of the cap head bolts to 5/16 .3125” for a little room to make the chuck a little adjustable. I could not use my thread in transfer screws to mark the backplate for drilling which I drill to get enough clearance to do the poor-mans set true mount. The chuck holes are a stupid 9.12 mm so the 9mm transfer punch is loose and the 9.5 is to large so the threaded hole in the back plate is a off 3 times. I turned down the tightest bolt and got the T I R down to .005 but ran out of movement. We will see tomorrow about the other 2, another nice 70* day and shop time.
Stay tuned
CH
 
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Seeing how the chuck mounts you will have a better fighting chance if you torque the mounting screws and alternate tightening. So it sounds like you problem is chuck alignment to backplate center. Good to hear your getting it worked out.
 
Cadillac said:
Seeing how the chuck mounts you will have a better fighting chance if you torque the mounting screws and alternate tightening. So it sounds like you problem is chuck alignment to backplate center. Good to hear your getting it worked out.
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Yes that is the problem. The threaded holes in the back plate are not perfect. I didn’t think about the chuck holes and bolts being a slip fit. Where on regular chucks the clearance of the back plate holes allow the chuck to be aligned some, so pressure don’t misalign the chuck when torqued. So this is my way of getting it aligned. This is the idea I got from Darkzero here.
CH
 
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I had that issue with the 3 jaw that came with the lathe - the counterbores for the cap screws in the backplate were too tight, so tightening the screws moved the chuck. I ended up redrilling the holes and mounting the screws without counterbores. I also turned the backplate register down so that I true the chuck up by bumping it to center (poor mans set true).
 
Well the problem is that the counter bores are in the chuck body. So the opion of re boring is not available. Opening up the bores is not a good opion either, i do not want ruin the chuck by breaking in to the scroll mount with a bolt. Basicly front mount chucks suck, they are great for rotary tables but not for a lathe mount. I may just go to a er40 chuck. I don’t use collets that much any way. I use my set true 3 jaw or independent 4 jaw. Just figured I would use it, if it were available for multi parts runs.
Thanks
CH
 
you can turn down the heads of the bolts if you only need a little bit of clearance. there's usually more than enough "head" to hold things together. Wouldn't take but a moment to find out.
 
mattthemuppet2 said:
you can turn down the heads of the bolts if you only need a little bit of clearance. there's usually more than enough "head" to hold things together. Wouldn't take but a moment to find out.
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It is not the heads it is the unthreaded shank of the bolt and the hole below the counter sink. The holes are realy tight on thje shank part of the bolt.
CH
 
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