SidecarFlip
Well-Known Member
Why try to make a silk purse from sows ear?
Doge like 'em.
Doge like 'em.
Cutting dovetails, how hard can it be...
- Thread starter Jinx-)
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Trickymissfit
Well-Known Member
you can't fix them long term. Many a person has tried in the past. Untill they find a way to stop the droop in the table, the gibs will suffer. There is a way to help it a bunch, but also creates another problem. The other isse with the gibs involves the narrow span of the saddle ways on the W axis. Plenty of way area, but to close together to counter act the leverage caused by the table over hang. I Mogliced one once thinking I had a solution to all the issues. The table was ground to less than .00025" compound error, and I used Moglice screw and nuts. Worked fantastic for about eight or ten inches of travel then locked up solid. Had to go back and seriously loosen everything up with regular ball screws. Machine ran great, and the compound error was less than half of the factory error. The other issue with Bridgeports that I never told any of you about is the lack of lube to the slides. Their system is prone to clogging up and also the oil lines will come out of their ports under any serious vibration. (they are only held in place by swedged lead pieces on the end of the oil lines. You can fix that with an afternoon of work, but then your faced with oil dripping all over the place. Why they never engineered an oil return system into the lube system I'll never know, and the wear on the gibs shows it after a few hundred hours of use. Moglice only needs about 1/4th the amount of lube to work well, but cannot handle missalignment caused by the table sag. Turcite would be far better, but in the end wouldn't last nearly as long as Moglice. Plus Moglice is what you want for accuracey. I'd rather use Rulon than Turcite, but it's also about ten times the cost. Yet it will last much longer than Turcite. I've rebuilt about 25 of them over the years, and had to learn about them the hard way. The factory rep told me once they were designed as throw away machines, and never ment to be rebuilt. I've built some pretty nice machines out of them, but nothing to compete with other milling machines of a different design.
gary
Trickymissfit
Well-Known Member
a lot of folks would like to know how. They are a one thousandth machine in 12" in new condition. I got .0003" on a 16" grainit H Block a couple times, but most times it was in the .00075" range. Still better than a factory machine in new condition
hary
Trickymissfit
Well-Known Member
the gibs tend to develop a warp when your dealing with long ones (all machines do this). You can straiten them out, but I won't tell you how, as you may destroy the gib doing this (I've seen more than one guy actually break them in half). There's another way to do it with a pencil torch, but have never tried it. You'll also need a good surface plate. If the gib has excessive wear in it, you can epoxy a brass strip to the backside. Then rescrape it flat again. Then you can scrape that gib back in. (often will be too long on the big end) If you buy a new gib, it will always be too long, and this puts right back where you started at. The otherway is to weld a piece of cast iron to the big end and cut it off at the small end. I recommend Exron 223 or 222 welding rods and a torch to help cool it down slowly. Either way you gotta rescrape it. By the way if any of you ever buy new gibs, always hang them vertically. Coat them with light spindle oil and wrap them in tin foil. Never allow the sunlight to come in contact with it, or it will warp
gary
Bullet bumper
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Then it is definitely not going to handle Climb milling .
I think ball-screws work great in climb milling, but I think it must be a problem with this particular set, just today I had few occurrences while conventional milling with 3/4 endmill when feeding on Y axis table shifted on X, almost 1/2 an inch at 45 degrees and doing pocket for toolholder I've seen few dives on Z while quill and knee was locked. So there is something going on with that mill, it probably needs a mill doc to pinpoint its problem
SidecarFlip
Well-Known Member
Sounds to me like the ball screws have lost their balls......
Interestingly, I read Gary's comments and took them with a grain of salt (to coin an old adage).....
Both my mills pee way oil all the time, actually the only machines that do that. I'm religious about stroking the oiler prior to and after using and regularly, I have to sop up extra lubricant laying in the saddle area... and I'm always watching the screws (gotta get down underneath the table and look) to make sure that they are getting oiled properly, but that is just me. I'm critical of my employees when it comes to maintenance too. Nothing focks up accuracy and/or machines faster than the 'I just work here and I didn't pay for the machinery, so what the hell, just run it attitude'......
Sounds like a combination of shot Gibs (got any adjustment left?) and dry screws that have eaten up the balls. Me, I want 'fluid' movement (fluid being the boundary lubricant between the metal and the metal.
Way oil is cheap. I use a lot, on everything with slideways. Of course that means tramp oil skimmers on flood cooled machines but that is a small price to pay for way longevity.
I apply the same principles to the air compressors (which are usually run hard and not maintained as a rule)..... Intake filters are cleaned every 3 months, I use K&N washable filters in the Solberg housings and lube oil is changed twice yearly and I use Mobil Rarus Synthetic in the reciprocating units and specified Mobil in the rotary screw.
Interestingly, I read Gary's comments and took them with a grain of salt (to coin an old adage).....
Both my mills pee way oil all the time, actually the only machines that do that. I'm religious about stroking the oiler prior to and after using and regularly, I have to sop up extra lubricant laying in the saddle area... and I'm always watching the screws (gotta get down underneath the table and look) to make sure that they are getting oiled properly, but that is just me. I'm critical of my employees when it comes to maintenance too. Nothing focks up accuracy and/or machines faster than the 'I just work here and I didn't pay for the machinery, so what the hell, just run it attitude'......
Sounds like a combination of shot Gibs (got any adjustment left?) and dry screws that have eaten up the balls. Me, I want 'fluid' movement (fluid being the boundary lubricant between the metal and the metal.
Way oil is cheap. I use a lot, on everything with slideways. Of course that means tramp oil skimmers on flood cooled machines but that is a small price to pay for way longevity.
I apply the same principles to the air compressors (which are usually run hard and not maintained as a rule)..... Intake filters are cleaned every 3 months, I use K&N washable filters in the Solberg housings and lube oil is changed twice yearly and I use Mobil Rarus Synthetic in the reciprocating units and specified Mobil in the rotary screw.
Trickymissfit
Well-Known Member
well, that thing doesn't have gibs, ball-screws that's all... But with new cutter all the problems what I had disappeared. Now I'm working on the tool-holder for that tool-post I made.
whatkind of tool holders have you in mind? Never seem to have enough boring bar holders Have you seen the setup that uses collets in it that are kinda like the ones used in a collet head on a lathe? Nice thing about that one is that it will pretty much fit any size boring bar up to about 1.25". Then Alourus sells them that use a set of rings with different I.D.'s, but still locks the bar down with several set screws. The thread cutting tool they sell that uses the high speed bit that can be reground is better than any carbide insert I've ever used (except for for the Acme stuff). Plus you can buy that cutter seperately, and the actual holder is pretty simple.
I've also used a square block deal that that uses the same Hardingh Brothers collets as they use in a lathe, but clamped in a mill vise. Worked so well that I built a six sided block and an eight sided block to use in a vise.
gary
The oilier on that mill is missing, there are pipes leading to the place were oilier once was, I did asked about the oilier and was told its fine without one, but I didn't buy it... So its ball-screws haven't been oiled since last summer... About toolholder, I have some HSS tools I made, just simple ones like facing, turning, cut-off-parting and 60 degree threading so I was thinking to make holder to fit them first.
SidecarFlip
Well-Known Member
Jinx...
Every table and cross has gibs. They are in there. Probably not one piece anymore in as much as you've been dry sliding the table and cross dovetails for so long and it sounds like the previous owner did too. Per chance was the feed crank hard to turn? If it wasn't, the gibs are long gone.....
Hope you didn't pay too much. Scrap price is about all she's worth. An alternative would be to find a lower in better shape (due diligence required) and pull the head and put it on the new (hopefully better) lower. That is, if the head is any good. The previous owner, if he fed you a line of dung about 'it don't need oiled' and the feed lines are missing (like Gary said, no easy replacement job in itself), then probably the head is shot as well. Those bearing packs like oil and plenty of it. I want to start the spindle and see a horizontal oil track across my shirt...every time. Thats why there is a large oil cup on the side (or should be........
I buy used machines regularly. First thing I look at is the condition of the gearbox oil, then the ways under the headstock and how many buggered screw heads there are. Finally, I take my trusty LSS Last Word indicator and take a reading on the spindle or mounting flange while hand deflecting the spindle to see just how abused the machine was...... and they all are, some more than others. When it's time to ge a new one, the old 'girl' is run hard and put away dry.
Used machinery is like going to a hay auction. Sellers tell you just what you want to hear because they know what you want.... a bargain. bargains don't mean squat if the bargain is a Sows Ear (to quote someone's signature line)......
Best tool I ever bought for a hay auction is a Delmhorst Digital moisture meter and hay probe. Makes a liar out of the best huckster, just like the Last Word does.
Couple years ago, an acquaintance bought a used Tree from a machinery dealer and asked me to haul it for him, which I did. I took one look at it b ut didn't say anything except 'are you sure'?? He was so geeked about the Tree, I wanted to break his bubble but thought better. We got it to his house, off loaded it and he hooked it up to a static (uch) converter and started it. The spindle sounded like an engine with piston slap. I left. It's probably at the scrap yard or he's posting somewhere asking for advice on how to 'fix' it.
Some things aren't worth fixing. Discretion is the better part of not ****ing good money after bad.......
Every table and cross has gibs. They are in there. Probably not one piece anymore in as much as you've been dry sliding the table and cross dovetails for so long and it sounds like the previous owner did too. Per chance was the feed crank hard to turn? If it wasn't, the gibs are long gone.....
Hope you didn't pay too much. Scrap price is about all she's worth. An alternative would be to find a lower in better shape (due diligence required) and pull the head and put it on the new (hopefully better) lower. That is, if the head is any good. The previous owner, if he fed you a line of dung about 'it don't need oiled' and the feed lines are missing (like Gary said, no easy replacement job in itself), then probably the head is shot as well. Those bearing packs like oil and plenty of it. I want to start the spindle and see a horizontal oil track across my shirt...every time. Thats why there is a large oil cup on the side (or should be........
I buy used machines regularly. First thing I look at is the condition of the gearbox oil, then the ways under the headstock and how many buggered screw heads there are. Finally, I take my trusty LSS Last Word indicator and take a reading on the spindle or mounting flange while hand deflecting the spindle to see just how abused the machine was...... and they all are, some more than others. When it's time to ge a new one, the old 'girl' is run hard and put away dry.
Used machinery is like going to a hay auction. Sellers tell you just what you want to hear because they know what you want.... a bargain. bargains don't mean squat if the bargain is a Sows Ear (to quote someone's signature line)......
Best tool I ever bought for a hay auction is a Delmhorst Digital moisture meter and hay probe. Makes a liar out of the best huckster, just like the Last Word does.
Couple years ago, an acquaintance bought a used Tree from a machinery dealer and asked me to haul it for him, which I did. I took one look at it b ut didn't say anything except 'are you sure'?? He was so geeked about the Tree, I wanted to break his bubble but thought better. We got it to his house, off loaded it and he hooked it up to a static (uch) converter and started it. The spindle sounded like an engine with piston slap. I left. It's probably at the scrap yard or he's posting somewhere asking for advice on how to 'fix' it.
Some things aren't worth fixing. Discretion is the better part of not ****ing good money after bad.......
Trickymissfit
Well-Known Member
The oil pumps were bought directly from Bijur (Allemite) by Bridgeport. You can also buy the little lead ferrals that go on the end of the oil lines. These are simply forced into the holes, and held in place by friction. Bijur also sells brass fittings with a strait #10-32 thread and a 1/4-28 thread. I replaced many of the fittings in the saddle and table with these. Most places that sell hydraulic and pneumatic valves and pumps also carry hose. If you go with steel line be prepaired to pay a little more. I recommend Nylicoil plasctic tubing with the standard wall thickness (about .03"). The 1/8th" and 5/32" stuff will handle 1000psi, so you don't need to worry about blowing a line. Bridgeport recommends Trueslide 300 oil (think it comes from Standard Oil which is now BP), but there is much better oil out there these days. 300 is a high parafin based oil, and I've seen it literally jell inside oil lines. Look for a non parafin equivalent (it's out there). Donot use automotive oils, or hydraulic oils!
Take a flashlight and look at the ball screw under the table. Is it black? Or does it look like it has a ground finish? If it's black you probably will see a groove about .025" wide on the center of the thread O.D. That means you have a roll thread screw. These are soft, and considered to be non precision. A ground screw should at least have some oil squirted on the thread O.D. every our of useage. I've seen Bridgeports with acme screws and both kinds of ball screws, but most come with an acme. If you need a new ball screw, the best out there is from Lead Screw International in Michigan. He sells both roll thread and precision screws. I could make you a list of shops to stay away from in this area, so beware.
gary
Gary, I didn't buy this mill and I don't own one so this is not my machine. It belongs to local college where precision machining and tool making are taught, so whenever I stop buy and see this mill available I have a permission to work on my little projects and believe me this one is the best they got from 7 other Bridgeports, at least this one got DRO with CNC Retrofit controller... I just don't understand when people pay high price to learn machining and have to work on the wrecks as such...
