Into the Head - Bridgeport 2J2 Variable Speed

[ctwo]

here's a pic.

[ken572]

ctwo,

How are you doing with your rebuild.

Ken.

[ctwo]

Ken, I created a new topic here: http://www.chaski.org/homemachinist/vie ... =4&t=98752 because I'm not sure that those knowledgeable ones will muscle through 4 pages to find my important question there. But thank you for reminding me to link these topics together for those that are as passionate...

I'm just in a situation where ignorance hurts. I spent a part of this morning measuring all the balls I have in my Z-axis ball screw and separating/counting them. I had not disassembled the screw with enough forethought that might have answered some questions, such as how many balls belong in each of the two ball screw circuits. I made the assumption that I had all the balls, but I do not actually know. I also have an impasse on the true ball dimension that I need since the loose balls that I recovered are more pitted from rust than what seems suitable for a precision ball screw as this (the balls in the screw are good). The dimensions are too close for me to accurately measure. I have a total of 290 balls, or 145 for each circuit, and that leaves two larger balls adjacent, which is not what I would expect...

I will probably buy some ball screw balls from ebay and compare the size I get. I am confident that I can measure precisely enough to compare the new vs. the old ones, and that will tell me if I need a different size. Ideally I would be able to look up a reference for the correct size and number of balls and get the right stuff...

[ctwo]

The shaft wabbles on that bearing

That would send up a red flag for me---even if it made no noise.

and much of the sound seems to come from there, so I just wanted to check it.

Indeed! Even without noise, I'd be concerned, as a bearing should have the ability to keep a shaft reasonably erect. With noise? My money says there's something amiss. Looking forward to your report.

Harold

You got it!

The lower spindle pulley came into focus today. I noticed that its carrier bearing must have spun, so I installed it back on its shaft, reversed for machining. The first picture shows the damaged pulley installed on the lathe, ready for clean-up...

After that was done, I machined a sleeve to take up the slack, and pressed it onto the pulley. The bearing has a slight press fit to the installed sleeve.

[ken572]

ctwo,

Go here:

http://www.neme-s.org/Contacts_and_Info ... e.htm#Join

Now scrowl down to, Club Related LINKs

Check out: Bridgeport Mill Rebuild by Kay Fisher

Very Cool.

Ken.

[ctwo]

Thanks, Ken! It's nice to see a ground up project done all the way through the right way. I am far too lazy and cheap to do such a good job on the finishing. I finally hope to have all the parts I need to keep my project moving forward. At least I painted something...

[ctwo]

What do you call that part on the end of the ram? I'm calling it a knuckle. I took mine off for clean and paint prep. This was the inspiring view - most of the blue in this view is gone. They did a better job painting the other side...

[ctwo]

Didn't want to bore you guys with a bunch of pictures, so here's a video. of the assembled head running. I kept the old bushings in the pulleys, so they are knocking a bit. I have new ones to put in sometime when it really needs it.


https://www.youtube.com/watch?v=c8mJlr9dApo

I've moved on to the bottom end, it's all apart and getting paint... No issues there, just clean, lube, and etc...