Bridgeport J-Head Rebuild Question

[Rockabye74]

I am currently rebuilding a 1963 Bridgeport Milling Machine. While disassembling the J-Head I have come to 2 areas where I will need some expert guidance.

1) I was trying to remove the reverse feed gears, and have come to the point where I have 2 gears remaining, and not sure which one comes out first. The bevel gear that is vertical, or the bevel gear that is horizontal. I am alsmost sure that the vertical bevel gear needs to be removed first, but don't want to force anything.

2) I do not know what tool to use to remove the spindle locking nut inside of the quill. I need to change all of the quill bearings and this nut is my last hurdle (I think)

[machintek]

If you are removing the bevel gears, I remove the carraige first that holds the brass gear. There are two set screw that hold it in place. Then I remove the front assembly (casting) that has the push/pull quill feed reverse in the center. The trick here is to remove the little ball AND not lose it. Now onw bevel gear comes out. More set screws on the side and front are removed and the brass bushings for the verticle shaft can be removed. Usually at this point the head is taken off the machine so I can push the shaft out from the back with the remaining bevel gear. Note that this shaft comes out with a large brass bushing (set screw on side locking it).

Get a piece of pipe close the the dimensions of what you need and mill it away to leave teeth that will engage the bearing lock nut. I usually turn it in a lathe a bit to get maximum amount of teeth area and best fit.

George

[Rockabye74]

Thank you so much for answering. I have an image that shows where I am so far, including an arrow pointing to the gear in question. How do you post pictures here to have them displayed? I have tried "Manage Attachments" which gives me the ability to upload, but then what do I do with it?

I think this gear (8007146 J-146 Feed Reverse Bevel Pinion) and its associated Bearing (8007108 J-108 Bevel Gear Bearing) get shoved up into the casting to free room for the bevel gear and shaft behind it. I have removed all of the set screws I can find, and this is not a simple slip fit like the others, but I guess from what you are saying, I should be able to pull/push this up through the casting?

[machintek]

Remove set screw in the front, have all in front of it removed on the shaft, take a brass drift and tap it up from the bottom (not that easy as it is hard to rech and you will be tapping it at an angle) and it will pop up into the feed selector gear change cavity. I assume you have the shaft above it removed.

George

[Rockabye74]

THANK YOU SO MUCH!!! Gear is out and now I can start cleaning up the J-Head and getting it ready for rebuild!!!

[Rockabye74]

How does that thing go, you are supposed to LEARN from your mistakes?

I pressed the spindle out of my quill, then proceeded to press out all of the bearings, stacking them and their spacers nicely on the work table next to me so that I could be sure of the replacement order and orientation, then before I could snap a picture or take notes, the table fell over and sent them flying all over the garage floor. I know the order of replacement, and I know that the bearings are direction specific (hence the nice ordering on the shaky table), but for the life of me I cannot find any documentation that specifies the direction of the spindle bearings ... any help would be greatly appreciated.

My initial thought was that the thrust from the spindle would always be in the "UP" direction, so the bevel of the thrust bearings would be facing down, but I have heard the "preload" term enough, and worked on enough cars with spindle bearings to know that spindle bearings normally face opposite each other, so logic would dictate the same if true even for a mill spindle ... and if this is the case, then the spacers must be ground to a specific length to establish the preload. How do I ensure that with a new set of bearings that these spacers are ground correctly?

[machintek]

The bearings have to be arrainged to create ZERO play. Just like bearings for ball screws, etc. Some bearings have a 'V" scribed on them to know how they go. Others come with a piece of paper showing a cross sectional view of the races and how they should go. Still others have dots on the face of the races that need to face each other. Go to the bearing manufacturers web-site and do a search.
As a general rule, I do not rebuild spindles in the field. I send them to C & M Precision Spindles in Tualatin, Oregon. They put new bearings in, preload it and regrind the tool taper with the spindle turning in the new bearings so there is Zero runout. They also have a setup where the spacers are replaced with 2 additional bearings for more rigidity. This at a price that is very competitive.

George

[Rockabye74]

After two days of searching the web, I found the orientation to be just as I expected. The spindle bearings face each other just as in an automotive arrangement.

I have read where users have reground the sprindle taper with the JHead completely assembled and turned 90 degrees on it's side, then using a sliding table set to the 16.5/2 degrees for an R8 Taper with a grinder attached to get a true grind. I have also seen where people do this similar procedure on a large lathe, but my lathe is not nearly big enough.

I am a firm believer in using the tools you have on hand to fix the tools you have on hand, or as justification for purchasing a new tool. It's a simple philosophy, but has helped me acquire a LOT of tools. Hmm, maybe I just need a larger lathe ...

[mxtras]

Rock-o -

I like your philosophy.

Scott

[Rockabye74]

I just read a data sheet that discussed the spindle bearings used in the Series I Bridgeport Mill. The document stated that the bearings are designed and built as a set and that the preload is established for mounting between two identical length round spacers. So basically, this means that if your spacer lengths are exact, preload is set.

I have checked my spacers and they are within .0001 of each other which is within the limits of the bearing requirements, so it looks as though when my bearings come in, I will be good to go.

[Rockabye74]

I realized I haven't sent any pictures of my JHead. Thought I would include some here so people could see what it started as, and where it is going. I realize the yellow is a bit bright, but I just don't think I can put another industrial grey machine in my garage.

[Rockabye74]

Since this machine in its prior life was a Navy machine, it has seen some abuse in its day. Mostly due to being stored and moved improperly. Just to demonstrate my fix a tool with a tool philosophy, I have included a picture of the broken Gearshift Plunger that was on the machine, and the new one that I fabricated on my Atlas Lathe from a stainless steel bolt I had lying around.