Fitting the new 4-jaw lathe chuck.

Machining the backplate

The real work to getting the chuck installed was really machining the backplate.  I first bored out the lip of the hub so that it would fit onto the spindle head properly.  Then I faced off almost a third of an inch from the hub to get it to engage the spindle threads.  Then I put the backplate on "frontwise" - the way it will be used, and proceeded to face off the front and bring the registration boss to the correct dimension to fit the inside of the chuck.  This registration boss had to be machined precisely to ensure the chuck would always mount true and run true to the backplate and hence the spindle.  All this machining took most of a day and produced a lot of iron shavings - well really more like sand!  What a mess!

TADA!  The new chuck is installed!

View from the side.  This chuck is screwed to the backplate form the front.

"Iron sand" from the machining of cast iron!

This stuff is everywhere!

I tried to keep it contained, but it still got everywhere!

This is the little that I was able to collect.  The rest got vacuumed up or wiped up when I cleaned later.

3-jaw chuck removal and the new 4-jaw chuck!

The old-stuck-3-jaw chuck

As I had mentioned at the end of the previous blog-post, I found that the backplate was attachd to the lathe spindle via a threaded connection.  A very tight and stuck threaded connection!

After reading many internet articles and advise on stuck-chuck removal I decided to try the hex-stock chuck and air-impact wrench approach to remove my stuck chuck.

The stuck backplate

1-inch hex stock chucked up tight

Used the impact wrench on the hex-stock to try to loosen the chuck.   It didn't work.

My next attempt was to just put a wrench on the hex stock and hit it with a mallet.  No joy that way either.  

After that, I recalled one article suggesting putting some hardwood under the chuck and extending one jaw of the chuck until it hit the hardwood block.  Then the article proposed running the lathe in reverse - using the backgears to get the highest torque (yikes) and allowing the jaw to slam into the hardwood block!   The idea initially scared me, primarily because of the use of the backgears - I could easily see that approach damaging the gears!  However, it seemed worth trying with just the pulley driving the spindle - the worst that can happen then is that the belt slips on the drive mechanism.  Instead of extending a single chuck jaw - which can't be done on a 3-jaw self-centering chuck - I removed the chuck itself from the backplate and then bolted a piece of angle iron to the backplate directly.   Then I engaged the lathe in reverse and BAMMM!  It didn't come off but it definitely made a solid impact - driving the angle iron into the hard oak over 1/4"!  After 4-5 attempts, which required moving new oak blocks into place because I didn't want the angle iron to break through and hit the lathe ways, the backplate finally spun off!  WHEW!!

The lathe spindle - the threads acutally look good and not rusty or amything!

The old-backplate.  UNSTUCK!  YAY!  The new backplate for my 4-jaw chuck is on the left.

The new backplate and 4-jaw chuck

To be clear, I am not getting rid of the old 3-jaw chuck, I just want the option to use the 4-jaw independent chuck.  The 4-jaw independent chuck is adjustable so that you can center items more precisely.    I bought a cheap 4-jaw chuck from SHARS along with a backplate to mount it to my threaded spindle head.  The backplate and the chuck came quickly - less than a week!  I was so happy to get these for the weekend!  

The new backplate.  

The new backplate will need some machining to get it to fit the new chuck correctly.  I did verify that the threaded part fits nicely on my spindle, however, the unthreaded collar section of the backplate will need to be bored out a little to fit over the spindle.  

The new 8 inch, 4-jaw chuck in its box - wood!

Box opened up.  The chuck key is on top there

Some documents, 4 hex-head bolts to attach the chuck to the backplate, and of course, the chuck itself.

The chuck! 

Here is the back

Showing the new backplate and the back of the chuck, The hub of the backplate has to be machined to fit into the depressed section of the chuck - exactly - this is critical for the precision and usabilty of the chuck.