Bridgeport -- transportation and putting it on casters

Ignoramus18706 writes:


A machine that old (50 years or more, was last made in the 1950s) is almost certainly aged and worn to extinction. Takes oddball spindle tooling. Table and saddle are small. Articulation and rigidity of the head is better on the later J or 2J models. Essentially "version 1" of the machine that, like all first versions, should be (and was by Bridgeport) discarded. For the cost and effort of moving and maintaining such a machine, you should go for the proper type.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard J Kinch wrote:

I think you need to look at the pictures more closely. While it is a round ram Bridgeport, it looks to have a 1J head on it which is R8 spindle and perfectly good, not the much less desirable "M" head. My Bridgeport is the same was, round ram and 1J head.
As for wear and tear, that has little to do with age and everything to do with use and care. From the pictures it appears to be in pretty good shape. I doubt there are any problems with it that would be an issue for a home shop.
Pete C.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Pete C. writes:

You're right. I stand corrected.

Rare to see a machine of this vintage that isn't clapped out. Of course anything is possible and you may just find a gem. From the looks of it, with the sloppy redone paint, I would suspect worse rather than better. The knee ways are the worst wear point, reducing the machine to a glorified drill press.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Richard, is there some way to quantify whether a mill is clapped out. Such as to measure a backlash at some points, or the play in quill, etc.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus18842 wrote:

Inspect the ways for obvious wear and damage. Look at the table condition as well, if it's in good shape with few holes, gouges and divots in it the machine in general is likely in decent shape. One key thing to remember is that these things will have a fair amount of backlash. They came from the factory that way as did pretty much every other manual mill. Only the CNC mills get the preloaded ballscrews with hardly any backlash. If the leadscrew isn't badly worn, the lead nut has provisions for tightening and reducing backlash.
Pete C.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Pete, thanks a lot. The ways looked nothing special. I will post more once I get it home.
i
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus18842 wrote:

You won't find all the little problems until you start running it but you can look it over and get a good idea of how good or bad it is.
Things to check:
Automatic quill feed used for boring. Check high and low speed as well as manual.
Run spindle at the high and low settings and listen for any strange noises. If it is a J2 head vary the speed in the high and low range and listen for any strange noises. If there are noises as the speed is varied, the fiber bushings and associated parts are worn, as well as the bearings and timing belts. A days worth of work and about 300 dollars in parts and pieces to repair unless you need the main spindle bearings which, the last time I bought a set were about 250 each.
Check the scraping on the underside of the table. See how far in from the end the scraping dissapears. If you can see real good scraping at the end with no wear but nothing toward the middle you have at least .010 wear on the table and the same on the far ends of the knee side of the bearing surface.
Repairing worn ways is a cheap repair but time consuming if you rescrape the ways manually. Scraping is a pretty straight forward repair and other than a straight edge, some prussian blue, feeler gauges and misc other items it is mostly time and patience.
Look to see how far the gibs are screwed in. The further in the more wear there is on the ways. They can be repaired by an application of turcite and rescraping the mating surfaces.
The same as above for the knee and associated ways and gibs.
check the crank handle on the knee for wear on the meshing teeth.. Pain in the butt when they get worn and slip.
Check the spindle runout with a dial gauge. Feel inside the spindle collet hole for the driving tang if it is sheared off. simple repair but without it the collets will tend to spin. Also check for roughness in the collet hole where damage has been done from not cleaning out chips or inserting collets with chips on them.
Check for backlash on the worm screws. If only the nut is worn it can be adjusted since it is a split nut on most machines. While you were under the table you should look at any wear on the worm screw for wear. Look and measure the thickness of the thread at the end vs. the thickness at the middle. If you have a lathe you can recut the existing screw and tighten the split nuts, or you will have to replace the screw.
Look at the outside of the quill for wear and scoring. Check that the quill lock is working properly.
Make sure all the locks and handles are on the dovetail overarm are working properly as well as loosen the locking bolts and move the head angle left and right to make sure that the worm screws is not broken or stripped. Same thing for left and right angle of the head.
Make sure the spring loaded downfeed handle is working properly.
Check the automatic boring feed disengage is working properly... and check it in both directions... up and down.
A ' clapped out' mill is still a bargin if you can get it cheap enoughand have the time to fix it up.... cheap being under 500 dollars.
good luck
John
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
John writes:

My Bridgeport table has no flaking visible anywhere on its ways, so I don't know that it should be diagnostic, although its possible my 1980s vintage machine had been reconditioned by being reground instead of scraped. The saddle and knee ways are all flaked, though.

Eh? You speak from experience?
My experience was that it took a long, long time of backbreaking labor to scrape off multiple thousandths off a quite large area of cast iron, and it takes a lot of expensive precision levels and custom made gages to do it right.
For example, there is no way you can get the knee ways coplanar with each other using just a straight edge. It took me three custom jigs, a precision level, a height gage, among the more expensive tools, as well as gage blocks and other more common items.
Scraping just the X and Y axes involves 22 separate surfaces! All must be scraped flat to less than a thou, and level in two degrees of freedom, and coplanar in another degree of freedom, each to all the others, and so on. For reliability, you must have at least two independent methods to confirm each such alignment (for example, a level across gage blocks, confirmed by a height gage on a reference surface). A lot more than just time and patience with simple tools. The scraping itself is quite a chore, but proper alignment is a complex and frustrating process that compounds the effort enormously.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard J Kinch wrote:

I would not recommend using a level while scraping since one little piece of scraped material under the level will get you into trouble in a hurry. A surface plate and a tenths dial indicator will do the job. Having two independant methods of measuring is nice but if you don't trust either method by itself you shouldn't be using either of them. The final check is when I machine a couple of test pieces before I deliver the equipment.
I've been doing it for 20 years on and off. I normally machine them first and then scrape them in it they are out over .010. I use power scrapers escept for final work and have all the equipment including a 5 x 10 granite surface plate to do them fast and right. I bought all the scraping stuff at the Bridgeport auction several years ago when they closed the plant.
The last couple of tenths is what takes the time. Getting everything absolutely parallel or perpendicular as the case may be is usualy not that hard if the original job was done right. If it wasn't you got to spot in some reference points and work off of them untill you get it close, then go back and remeasure and check your surfaces for parallel and on the same plane.
One thing I have notices on some tables is that they tend to bend down on each end if you measure across the top surface. Mostly seen it on older machines with a lot of parts put on and off the table. The dings and abrasion must expand the top surface and give it a bow on the top surface or someone tried to cut the top at one time with a bad set of ways. In any event you got to map out all the surfaces before you start to find where the metal must be removed to bring the thing in spec.
I have G&L hbm coming up to do that is in real bad shape. Saddle W axis is worn on one end of each way, the x axis is worn down on the spindle side way and the tailstock need some work on it too. The gibs have to be redone and a bunch of other things.
It will also need the x, y and z Quill axis to be squared up as well as the column.
John
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
John writes:

I don't know how you can check two separated surfaces (such as the knee ways) for coplanarity and squarness without a level. A dial indicator only indicates heights, not angles.
With six degrees of freedom on the two knee ways alone (two surfaces, two tilts and one height each), you need at least six independent measurements to prove them coplanar, and you just don't get that with a dial indicator.
Specks under the level are not a problem. They are easily detected if missed in the routine cleaning. Since you are reading the level as it bridges gage blocks, anyway; the level is not flat on the ways themselves where specks would tend to interfere.

This flatly contradicts basic principles of metrology. You trust your measurements, but you check them against each other, as much to catch your own dumb errors as instrument problems.
"If you don't trust"? Error is *never* impossible, trust is never 100 percent, so you diminish likelihood of error by compounding reliable and redundant measurements.

Well, of course the proof is in the pudding, but if such a test fails, it gives you next to no diagnostic information about where the problem is, so it is not really a metrological test, it is simply a pass/fail proof of performance.
I may wholly trust my calipers and micrometer when machining a part to a tolerance, but I am sure gonna apply them both before making that final cut.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard J Kinch wrote:

Optical measurement
cylindrical square
Granite square
for starters

no wonder it took you so long.
A dial indicator,and a surface plate will give you all the measurements you need to determine flatness and establish the amount of wear on each way.

How good do you think a level is? The best ones I've seen are +- .0002 in 15 inches. You got to hold the surfaces better than that if you want to hold .0001 . A dial indicator will read flatness a lot better than that. A .0001 dial will be as good as your granite surface plate.

When is the last time you saw a machinist have two of each sized mike in his toolbox and using both on the same measurement. You use one that has been calibrated with a known history and check it with a B grade standard on the shop floor.

So if you get two different readings which one do you throw out?

The final pass/fail test is a crosscheck on all the work done. Each step is checked as it is done by one set of calibrated instruments that have a calibration history that shows no continual out of calibration conditions. Also, if required you could recheck the instruments after the measurements are done to recertify that the instruments are performing properly. Every new machine shipped or installed of any quality comes with a final inspection sheet with the measured and guaranteed minimum accuracy listed. Squareness of the ways for instance is measured by cutting a square block and checking the squareness of the block.

I would suggest that you rather check the mike against a NIST traceable standard and not rely on the calipers since they aren't good for any quantitative measurement with a tol. of less than .002 in most cases, especially with larger dimensions.
John
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
john writes:

You must be assuming that you have a surface plate large enough to envelop the work, so you can take the work to the gage. Most of us don't have that luxury, and have to use gages we can lift at arms length; we take the gage to the work. In which case, you gotta have other means to gage angles and coplanarity than a reference surface and height gage.
See Connelly. He's very fond of levels.

When I've invested hours in a part, I'm checking the last few cuts with confidence-increasing techniques like redundant measurements with redundant instruments. But then I'm not infallible, and the devil of entropy hovers over my left shoulder, with his friend distraction on the right.

Both. Check your instruments and try again.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ignoramus18842 writes:

Simply visually you can see if the knee ways are worn by comparing the fish-scale flaking pattern at the ends versus the middle, and inspecting for grooves made by trapped swarf, gouges from dropped tools or work, and brazed repairs to the like, on the way surfaces.
If you have a scraped straightedge, such as a machinist's precision square that you have scraped to fine-tune the flatness, which fits along the exposed portion of the knee ways, you can quantify the way wear with feeler gages slipped underneath. One thou is a lot, and a few thou are trouble. The flaking is only about a thou deep itself, so if it is worn off in the middle that's an ominous sign.
You can take along a magnetic-base dial gage and quickly measure the TIR on the spindle. You can run the head (if under power) to listen for noise and test all the power feeds and backgear.
These simple tests are all that is usually practical when going to inspect and evaluate a candidate used machine. You can't typically be laying inked-up flatness gages on the table. But like a woman's hands, a quick inspection usually tells the true age of the specimen, even though the rest of the apparatus may have been painted up or surgically altered to look younger, or may look older than apparent due to some hard tasks in life.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard J Kinch wrote:

While all this is true, also bear in mind that an old Bridgeport with even moderately worn ways is still vastly superior to any new asian bench top mills as none of them even have scraped ways to begin with and none have the mass or rigidity or true HP of a Bridgeport.
Pete C.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Pete C. writes:

The Harbor Freight mill-drills and large lathes certainly have scraped ways.
(Not that the mass and rigidity of a mill-drill compares to a Bridgeport.)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard J Kinch wrote:

Not any that I've noticed in the two HF stores in my area.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Pete C. writes:

Really? They don't have that frosted look around the dovetails? It's not the fish-scale pattern for oil retention like on a Bridgeport knee.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard J Kinch wrote:

I think hardened (hopefully) and ground is about the best any of those machines will get. Certainly the lower end models don't appear to even get that. The higher end stuff like the full sized Bridgeport clones that Grizzly sells are likely scraped properly or at least semi properly, but HF doesn't carry those.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Pete C. writes:

You're mistaken. I have these two in my shop and their dovetail ways are certainly hand-scraped:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber3686 http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber3274
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Richard J Kinch wrote:

I'll take a closer look at them on my next HF visit.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.