Let's Talk About Wear On Our Bridgeport Milling Machines

[Janderso]

Hi,
I am new to milling. I purchased my 1970 Step Pulley last winter. I really had no idea what to look for and the price was right so I bought it.
As I am learning about this machine and getting to use it more and more, I am finding a few things that concern me.
First of all, the Y and X tighten up on both ends. I find there is table movement (I haven't measured it yet). When I am in the highly used zone and enjoying free wheeling of the ball cranks there is quite a bit of table movement. As I move from side to side the movement is significantly less as the ball cranks tighten up against the gib.
I tighten up what I can when milling and so far the machine has performed well for me. When I make a cut, I check for squareness and depth consistency and I find little deviation and I am cutting right angles.
Now, maybe for this hobbyist the wear has not yet become an issue.
The head is quiet, the quill binds a bit but that's OK, the back gears are quiet and all the machine functions seem to work OK.
I have a hunch there are many of us in the same position.
What are you doing about the wear? When I tighten up the locking screw the table tightens up great.
Have you considered having yours ground/scraped in?
Have you considered doing it yourself? Cringe.
What options are available?
I'd like to talk about it.
Jeff

 

[markba633csi]

Yes it can be scraped in but it's a job. Maybe Rich King can elaborate on this, he's our resident expert
Do you have a long table version or a short one like 32"? Shorter the table the less work to fix I think.
Sometimes the gib can be shimmed to give some improvement

 

[Technical Ted]

Here are my feelings on this subject for what they are worth. Unless you are either very lucky or spend more money than I could justify for my use, you will most likely end up with machines that are either older, have more wear or both...

My 2J Bridgeport has wear in the Y travel and I ended up putting a shim behind the gib. This helped quite a bit and I have it adjusted so it travels the whole distance, but does get tighter on the ends. I have not measured slop in the center of travel with an indicator, but have not had any issues on any of the jobs I have done on it, so it probably depends a lot on the type of work you're going to do on it. For my use, a hobbyist, mine is fine and if I do see an issue I can use my Jet mill which is like new and very tight (but I don't really see this happening).

I don't have the knowledge or equipment to scrap the ways in. My feeling is if it's not broken (for my use) don't fix it.

You said the quill binds. Does it bind near the top? If so, try loosening the set screw on the very bottom collar of the quill (in the back). I had to do this and it freed mine up fine.

Ted

 

[Janderso]

Yes it can be scraped in but it's a job. Maybe Rich King can elaborate on this, he's our resident expert
Do you have a long table version or a short one like 32"? Shorter the table the less work to fix I think.
Sometimes the gib can be shimmed to give some improvement

It's a 42" table.
I would like to shim the gib. If I could take up the wear in the center only.
I am thinking you would loosen the gib to allow free table movement, then determine the amount of shim required?
How would you go about that? Trial and error, or is there a more scientific method?
Ted, I'll check the set screw, thanks.

 

[Technical Ted]

Is the front end of the gib (inside, smallest end) extending beyond the saddle and sticking out some? It shouldn't be. When I did it to mine, I tried getting the gib in about the center of it's intended position, leaning towards more towards the front of the machine where the adjustment screw is rather than in farther). I removed the gib and cut a shim to fit behind it and if I remember correctly cut the shim a little long on both ends so I could bend some at 90 degrees to help hold it in position. I planned on just using trial and error, but I hit it on the first try. Hopefully, you can get away with 0.005 - 0.010". You will also need to make holes where the oil grooves and holes are. I used a Dremel to do this and it worked well.

Now, I'm no expert here, but this is what I did and it seems to be working well.

Edit: It didn't seem like the collar set screw on the quill being too tight could possibly be causing an issue, but it doesn't take much to make the quill out of round because of the close fit. I loosened the screw and just barely snugged it and it works nice and free now where prior to doing so made it bind quite a bit.

Ted

 

[Cadillac]

What you want to do is first see if the gib has adjustment? Sounds like it’s worn if it’s tight on the ends of travel then nice and free in the center. Also check the dovetails underneath. They may be rusty or have debris on them causing it to be tight. Recommend pulling the gibbs and at least clean and inspect. Gives you a opportunity to oil and adjust to see where your at? Shimming is only necessary if gib has no more adjustment. And that still won’t take care of the hour glass shape in the ways probably.

 

[Janderso]

Is the front end of the gib (inside, smallest end) extending beyond the saddle and sticking out some? It shouldn't be. When I did it to mine, I tried getting the gib in about the center of it's intended position, leaning towards more towards the front of the machine where the adjustment screw is rather than in farther). I removed the gib and cut a shim to fit behind it and if I remember correctly cut the shim a little long on both ends so I could bend some at 90 degrees to help hold it in position. I planned on just using trial and error, but I hit it on the first try. Hopefully, you can get away with 0.005 - 0.010". You will also need to make holes where the oil grooves and holes are. I used a Dremel to do this and it worked well.

Now, I'm no expert here, but this is what I did and it seems to be working well.

Edit: It didn't seem like the collar set screw on the quill being too tight could possibly be causing an issue, but it doesn't take much to make the quill out of round because of the close fit. I loosened the screw and just barely snugged it and it works nice and free now where prior to doing so made it bind quite a bit.

Ted

I just found the video that H&W made about this same subject. Unfortunately it won’t solve my problem, I still have gib adjustment available.

 

[Janderso]

What you want to do is first see if the gib has adjustment? Sounds like it’s worn if it’s tight on the ends of travel then nice and free in the center. Also check the dovetails underneath. They may be rusty or have debris on them causing it to be tight. Recommend pulling the gibbs and at least clean and inspect. Gives you a opportunity to oil and adjust to see where your at? Shimming is only necessary if gib has no more adjustment. And that still won’t take care of the hour glass shape in the ways probably.

I should take the table off and check for items you mentioned. It couldn’t hurt.

 

[projectnut]

With a machine of that age there is likely a fair amount of wear on the lead screws and nuts. A good deal of the play at the center of the travel can be eliminated by either cutting or replacing the brass nuts. If it has the original nut on the X feed it is split about half way through in the middle something like this:

https://www.mscdirect.com/browse/tn...MIhJWj_4De2wIVAxBpCh2REgR7EAYYASABEgIFKPD_BwE

You can finish the cut, square the ends and reinstall them to eliminate a vast majority of the slop. Once that's done you can adjust the gib to eliminate even more. My 1972 machine had considerable slop in both the X and Y directions when I first got it. I cut the nuts, readjusted the gibs, and got the play down to .005" on the X axis and .007" on the Y axis. I've had the machine going on 20 years and both axis have about .010" play today.

I would contact these people for parts and advise on how to proceed:

https://www.mscdirect.com/browse/tn...MIhJWj_4De2wIVAxBpCh2REgR7EAYYASABEgIFKPD_BwE

They are extremely knowledgeable, their prices are more than fair, and they are more than happy to help out. I have done business with them since I first purchased my mill.

 

[Janderso]

That gives me hope Mr. Projectnut. I really do not want to get too carried away with my old mill and I do love the old Iron.
MSDirect and I are already acquainted $$$$$
Thank you.