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KB'S TOOLS AND REPAIR

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BRIDGEPORT MILLING MACHINE REBUILD – PART I

STARTING THE REBUILD

The Bridgeport Mill rebuild has started. The very first steps in a rebuild is to gather all the information you can about your machine. This includes prints, exploded views, machine model numbers, serial numbers, parts lists, part suppliers and so on. Search the web for forums as these are an excellent source for information, and if you don’t have access to the internet, find some friends that do (also, make sure they are strong enough to help move some of the heavy parts).

Bridgeport Milling Machine Rebuild

The second step is to gather all the tools need for this job. It will take more then just a screwdriver and hammer. If you have a trades background you will probably have a good selection of tools already. You can pick up a lot of these tools used, saving you a ton of money. Then there are the measuring tools, also look for good used ones, precision is key. They are out there, but you need to hunt and be patient.

The third step is to dismantle the mill and clean it’s individual components. Make sure you bag,  label and (possibly the most important thing… ) recording each phase of the rebuild with a camera and accurate details. Creating accurate notes will assist you when communicating with others, such as part suppliers and any technical support services, plus they will act as a re-assembly guide for yourself .

My goal is to show the basic steps that I use for a rebuild, I post these items to share my experience’s with you. It  must be understood that I am not responsible, in any way, for what you do. So please make sure you understand what I’m saying… KBS TOOLS AND REPAIR assumes no liability or responsibility for your projects, rebuilds, or anything else you do. If you do not accept these terms please do not use this blog.

Rule #1 ……Safety.

This includes things like safety glasses, hearing protection, and lifting equipment. There are a lot of suppliers of PPE out there and the gear is not costly – it’s your responsibility to keep yourself safe, not someone else’s.

So let the games begin!

BRIDGEPORT MILLING MACHINE REBUILD – PART II

SETTING UP THE BASE

LAYING THE MILLING MACHINE DOWN

The base has been set on its back, which allows you to examine and preform any work needed on the dovetails. I used a number of slings and a portable engine crane to set the base on it’s back safely. Once it was in this position, a hole was drilled and tapped so an eye bolt could be used to move the base around without slings. The drilled and tapped hole is the balance point of the base. To find this location I simply wrapped the sling around the tower portion of the base, and kept lifting the base using the hydraulic engine crane, until the balance point was found. Make sure to use a properly rated eye bolt. No short cuts in this area!

The base will need to be leveled so a very positive three point adjustable system is used. The top of the dovetail flats are factory surfaces that should have no wear marks on them. A few passes with a fine honing stone will make sure there are no irregularities on these two surfaces.The Starret level is placed on the dovetail top surface. Adjust the base,end to end to get it 100% level using the turret adjuster.

STARRET LEVEL ON THE DOVETAIL SURFACE

The level is now turned 90 degrees and the base is leveled left to right. This is done by adjusting the two legs attached to the base. You should go back and check the levelness of the length. Then check it left to right again. It should be noted this base will need to be checked for level periodically as it will move as you work on it .

CHECKING LEFT TO RIGHT

Great care should be taken at the leveling stage, having sturdy adjustable legs that are well attached to the base will keep you from chasing your tail.

Now that the top surface of the dovetails are level, it will become the datum line for all the work that takes place on the base. I decided to check the top of the dovetails using a surface plate. Before I set the plate on the dovetails, I made a pass down the length of each dovetail top surface followed up by a quick hone which roughs up that surface for a better picture. I turned over my 24″x36″ plate and applied a thin coat of Prussian Blue to it. Next I applied a thin coat of red-lead that will act as a background on the freshly scraped surface. When I lift the plate off, the picture revealed I had some contact end to end and left to right. I decided I wanted a surface with more contact points, so I made several passes taking a reading each time. When I was satisfied with the picture, I rechecked the base for level, which needed a bit more adjustment in both planes (out by .0005). This newly scraped factory surface is now a very useful datum for taking measurement from.

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