greets all i have a bridgeport Jhead (varispeed pulley) not sure of its age.
i bought it recently and have been 'fixn it up' at any rate.. the table has alot of slop in it. if i push/pull the ends of the table it'll move maybe
+/- 5degrees. a heck of alot.
i can't adjust the dovetails any tighter. i removed the adjustment screw and pushed the dovetail key (?) in. it went down about
1/2" past where the screw bottoms out.
it is reasonable to assume that these "dovetail keys" are worn.. and not the ways? if so, anyone know where i can order a new (or barely used) set?
(the X, or short axis, is shot.. the Y is still good, but might as well change them both)
maybe this is a good time to change the brass nut, too? it seems pretty tight.. i have little backlash.. but its also at the bottom end of its adjustment range.
My old BP had had its ways rescraped and new X and Y nuts. The X axis gib as it came from the rebuilder has Turcite on it. If it isn't Turcite, it's something very like it. It's white and waxy looking.
A new tapered gib will need to be scraped in and it costs big bucks or is a giant hassle. I like the idea of removing it and putting in a shim. If there's a machinery rebuilder in your area I'd go talk to their service manager. It was great when Hallidie Equipment was a BP official service center - they worked on tons of them and had a "boneyard" they'd let guys like us pick through for free, and had great advice. Now not only are they no longer a Bridgeport service center, they went all the way out of business.
FWIW, to have them scrape my ways and replace the nuts and grind the table and clean and repaint the mill in 1997 was about $1400.
just got off the phone with a Mr. John Hernandez of Hardige-Bridgeport. He gave me the same bad news: the new gib will have to be scraped in.
the only thing i've ever scraped is my knee.
seems like a shim is my only way out.
wonder how long a shim will last / how often i'll have to change it.
at any rate.. my problem now is finding some shim stock. brass sounds like a good idea. but i'm living up in the remote italian hilltops with very little access to anything useful (like shimstock).
getting a bridgeport mill up here is another story unto itself.
is copper too hard? i can get 0.6mm copper sheeting (they use it for roofing in these parts). would hate to do (further) damage to the ways.
The shim will last forever, there's nothing to wear it out. I used brass because I have a load of it. On other machines I have super-glued paper onto gibs. Be creative, you can't damage anything.
Here is dating a Bridgeport info from an old post on this group Michael no xx's in address
From: Peter Reilley ( snipped-for-privacy@mv.com) Subject: Bridgeport Milling serial number list Newsgroups: rec.crafts.metalworking View: Complete Thread (5 articles) | Original Format Date: 1997/12/14
Here is the list of serial numbers for Bridgeport J head milling machines. This is straight from Bridgeport.
Also, I am looking for a Bridgeport class machine that is in reasonably good shape. A DRO would be nice as would a CNC attachment. The machine should be not too far from New Hampshire.
I would be willing to maintain similar lists for other machinery if people can supply the info. You can fax it to me if necessary. email me for my fax number.
This list was scanned in to my computer using OCR software so there might be some errors.
Pete.
BRIDGEPORT MILLING MACHINE "J" HEAD SERIAL NUMBERS
The serial number is on the knee of the machine. It can be obscured by the chip shield.
This file has been around for a long time. Since it goes back to
1938, it applies to ALL Bridgeport milling machines, not just J head. But, the serial numbers from 1940 to 1943 are scrambled. It seems impossible that they sold SN 656 in 1940, but didn't get SN 560 sold until 1942. I have a round-ram machine, SN 1399, which could have been made in 1941, 1942 or 1943!
Looking closer, it seems that 1943 should be 2944-4105, and
1942 might be 1560-2943, as there could be 11 machines that were overlapped in the production line between 1941 and 1942.
i, too, have seen this file before. though it hasn't been of much help: the serial number stamped on the knee (under the two chip guards) reads: J-013 thats it. the metal is in pretty good shape.. i'm pretty sure no other numbers were worn off. its clearly stamped J-013.
at first i wondered if i'd gotten bridgeport's
13th mill!
JohnHernandez, mentioned above, dated my machine at/around 1949.
There were some typos in the list. I actually scanned it and used OCR to get the text. It is pretty easy to see the error. In 1942 the 560 should be
1550. The "1" got dropped and the 5 was read as a 6. In 1943 the leading
2 was dropped from 944.
I think that there are some other errors in the list. People have pointed them out to me over the years. I believe that I posted a corrected list a while back.
Bridgeport did make special mills for people, mostly the government. I believe that they had different serial numbers. Is your mill normal for the year that you think that it is. J head vs. M head and round ram vs. V ram? Is the table size normal? I don't know all the variations that they produced.
It is very possible, that around 1955-1956, when the J head was introduced, and then mounted with the dovetail ram, that a short run of demo or test machines were made to find all the kinks that real shop use will always turn up. That could explain an out-of- sequence number like that.
Does your machine have a dovetail ram? The first J-head machines were built with the round ram, as they converted over to the modern design a step at a time. Does it have 9 or 12" of Y travel?
Note that the nuts are Bronze, not brass - big difference! On the older machines, they are solid. On the newer machines, they are either partially split into two, or are cut completely into two rings. The arrangement of screws that hold them in the bore in the yoke allows them to be squeezed together to take up backlash. When you do this, you need to adjust it until backlash nears zero on the outermost ranges of travel, where the screw is least worn. These nuts are so hard that the wear in the screw is about the same as the wear in the nut! So, if you have a lot of backlash, 30 - 50% is in the screw, and you won't be able to completely eliminate all of it. Typically, the Y screw and nut are worn much worse than the X, since the oil flow gets to the X first, and only what drips off the X nut gets to the Y.
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