Bridgeport Saddle way wear. How much wear is normal

I'm in the process of rebuilding my Bridgeport. The upper ways look ok, but I found quite a bit of wear common to the lower interfacing surfaces of the table Saddle.

How bad does this look? How much is normal? Does this warrant mitigating action at this point?

When you deal with measurements in the thousandth of an inch it is almost impossible to tell the condition of something from a picture. We can see that there is some wear but is it .001 or .051 and more important is the wear even.

Do you have a indicator and surface plate to measure with?

It's not worn below the relieved area in the middle. I would regard that as normal to minimal. Run it.

I don't have a surface plate unfortunately. I can tell you that it looks like the pad on the bottom left hand corner has worn down to the point that on the left side of that pad is even with the under-flush (relieved area) middle surface of the way. It looks like a similar condition exists on the right side to a lesser extent.

I guess my question is how bad does it get before you decide to send it out for scraping, or find a new saddle?

Thanks

It depends entirely on the work you do and what you can put up with.

I have somewhat similar looking wear on my machine (which I recently tore down like yours). If you have chrome ways (as my machine did), what you'll find is that where two pieces of metal come together, one side is chromed and the other is not. Since the chrome side is harder, it wears much more slowly. The non-chrome side is the more "sacrificial" side.

I'm not a machinist nor am I a machine rebuilder, so take my advice for what's it's worth (i.e. nothing ;-) but IMO if the chrome side of the ways are still pretty good, then I would take that as a good sign the machine may still be capable of making accurate parts. If you still see good flaking on all parts of the mating chromed ways, that means it hasn't been worn into a dished or banana shape and it is still almost perfectly flat. Since the saddle shown is constantly riding on that flat part, I would be hopeful and expecting the worn part to probably be worn down pretty evenly, thereby maintaining relative squareness with the rest of the machine (as long as it hasn't been worn to or below the factory relieved sections in the middle).

Bottomline is to see what kind of cut the machine makes on a long workpiece when fully assembled. It may make perfectly usable and good parts, especially if you're an amateur hack like I am, where the limitation is more with the operator than it is with the machine. That was the advice given to me when I asked the same question you did a few months ago. So I cleaned my machine up, adjusted everything and put it back together. Unless you see major wear, I'd do the same thing and see how it does at producing parts that are similar to what you plan on using it for. Good luck.

Jeremiah L said:

I don't have a surface plate unfortunately. I can tell you that it looks like the pad on the bottom left hand corner has worn down to the point that on the left side of that pad is even with the under-flush (relieved area) middle surface of the way. It looks like a similar condition exists on the right side to a lesser extent.

I guess my question is how bad does it get before you decide to send it out for scraping, or find a new saddle?

Thanks

Click to expand...

I don't mean to sound like a pedantic PM jerk, but the question isn't "is the wear normal". Yes, its normal. The question is "will this wear effect the performance/accuracy of your mill".

For that, you need to measure it. Take this as a sign from God that you need to procure a 18X24" min. surface plate. Before anyone can speculate about mitigation, we need hard numbers. Stone the upper side slowly and carefully. Wipe it clean with lint free cloth. Then flip it over onto a surface plate and run a DTI across that lower surface of the saddle. It could be worn evenly, in which case only flaking would be compromised. And depending on the top surface of the knee, that could be okay.

If you have an old mill, you need a good surface plate. Its not a luxury item or a nice to have. Its an absolute necessity.

Seeing your new and seems short of funds, I will try to help you a way you can use the machine until you can afford to do it the right way. The bottom of the saddle looks bad and if you can't afford to buy a plate, you probably can't afford to do anything accept to clean, stone and assemble it. Those brass jets on the left in the manifold are called BiJur metering units and depending on where you buy them they cost between $8.00 to $20.00 each. They are difficult to clean and even when new the oil flows slowly through them. If I were you I would clean out the pump reservoir and fill it with kerosene, set the saddle on a stool next to the machine, carefully attach the hose and and pump the handle and clean the oil lines out and when clear kero flows out empty the tank and fill it back up with Vacta 2 way oil.

It does look like it has chrome ways and with the saddle ways worn that bad I would bet money the top of the knee where it rides in messed up too. The top of the knee even if it is chromed is worn in the middle 2/3's and not worn at all on the front and back of the travel. If you have a Micrometer...I believe it's a 8 to 9" you can lay 2 dowell pins on opposite sides of the flats up against the dovetails and measure them. If you don't have a Mic, after you clean everything up assemble it and when you tighten the saddle gib up in the middle and you try to move the saddle to the unworn ends, it will bind up. Many times the gib is worn and you run out of adjustment.

If you could post a picture ofthe top of the knee, it would help take one of each side so we can see the flats and dovetails...a picture of the gibs too.

How about you do that and then come back and let us know. If you would prefer send me a private message and we can talk on the phone. Good Luck. Rich

PS: Steve Watkins can rebuild your machine if needed. He has a sweet planer he can machine the parts for you.