Bridgeport Spindle - The Age Old Question: To Grind or Not To Grind?

[Fasttrack]

I'm rebuilding a 1.5 hp 2J Bridgy I bought at auction and will post a thread on it a bit later. For now, I have a few questions about the spindle but first the critical information:

1) I made a colossal mistake in tearing the machine down before even running it (at the time, I was just planning on replacing the worm gear shaft that adjusts the head tilt), so the head is off the machine.
2) I checked the runout (err... whompeyjawdness) by laying the head down on a massive cast iron setup block and indicating the taper with a 0.0001 DTI while I turned the spindle by hand. Provided I was gentle so as not to cause any motion of the head on the block, I got an estimated TIR of 0.0003".
3) The internal taper shows some signs of abuse with some score marks. Later today, I will blue up a new R8 collet and take a print to see just how bad things are. Further up the spindle, where the little dog screw / key normally keeps the collet from spinning, is very torn up (a fairly common problem when a collet spins and buggers up the key).
4) The nose of the spindle has a few dings, also indicating a hard life
5) The spindle feels a little strange to me - a bit "stickier" than the J-head I rebuilt previously. I suspect this one has sealed ball bearings instead of the open, oil lubricated bearings on the J-head. Can anyone confirm that the 2J heads used sealed, greased bearings? Also, because I did not run it first, I do not know how much heat these generate, which might have been a good indicator.
6) Last night, I removed the quill from the housing so I could clean, strip, and paint the housing. The spindle remains in the quill.

General questions:

1) What additional tests or improved setups should I explore to test the spindle?
2) I suspect the bearings are probably okay - not spectacular but likely good enough - but I'm anticipating a bad print on the collet. If that's the case, should I send my spindle out for regrind and ask them to go ahead and replace the bearings? If I send the spindle out, will they touch up the outer diameter with the dings? Will they clean up the interior where a collet spun?
3) I have a very nice 6x18 surface grinder I trust and a less trust-worthy (haven't actually gotten it under power yet but is very crusty and dirty) KO Lee T&C grinder... you know where I'm going with this ... grind my own spindle?? It would take a lot of trial and error on blanks to get the taper just right and I'm guessing it's probably best to just farm this out but thought I'd ask.

A new spindle, without bearings, looks like it's about $750. Any ideas what it costs to regrind a spindle? I saw some references to a cost of about $450 through Wells Index but not sure if that's still accurate.

Thanks!

[Dave C]

I've been into several Bridgeports and clones from the 60's to 90's, and have never seen sealed bearings in one. I would bet that if yours has sealed bearings in it, someone has been in there before and put them there. I currently have my Supermax (Bridgeport clone) apart and plan to replace the upper bearings with sealed ones. I haven't taken the quill apart yet but hope the spindle bearings are ok. If they do need to be replaced, I will use the OEM open type.

[Sparky_NY]

I've been into several Bridgeports and clones from the 60's to 90's, and have never seen sealed bearings in one. I would bet that if yours has sealed bearings in it, someone has been in there before and put them there. I currently have my Supermax (Bridgeport clone) apart and plan to replace the upper bearings with sealed ones. I haven't taken the quill apart yet but hope the spindle bearings are ok. If they do need to be replaced, I will use the OEM open type.

I on on my 3rd BP with a 2j head, all 3 had a tag riveted to the head that read "sealed bearings, do not oil". That plus there is no oil fitting.

[Fasttrack]

I on on my 3rd BP with a 2j head, all 3 had a tag riveted to the head that read "sealed bearings, do not oil". That plus there is no oil fitting.

Interesting - mine is missing that tag but it makes sense for the 2J since that whole backgear assembly is packed full of grease. No way to get oil down into the spindle bearings, although I noticed that the quill still included a felt "oil strainer" washer. What's up with that? Mine is all buggered up... the metal ring with the tab has become dislodged from the actual felt washer. I was going to replace it but ... is it really necessary? Maybe it's just a way of keeping goop out of the quill assembly...

[Dave C]

Later models than I've worked on?

[Toolguy]

I have done several BP and clone spindles over the years. The top bearing is usually an inexpensive sealed radial, the bottom ones are non sealed class 7 angular contact bearings. The best spindle grease is Kluber NBU-15 from Germany. I have tried several other kinds of grease in these bearings, and every time they would way overheat if you tried to go above 2500 RPM. Finally found Kluber. I can run 4000 rpm and they only get warm to the touch. At 3000, they are still room temp, below body temp.

I have refurbed a few spindles on the lathe. I put the splined part in the adjust-tru chuck and the bottom bearing in the steady rest. Check for runout with an indicator, straighten as needed. If the splines are twisted, it makes it hard to use the quill. They can be untwisted on the lathe. Once the spindle is straight, it's time to check the R8 taper. You can easily recut the taper on the lathe (if it's big enough - I'm using a 14 x 40). Set the compound slide to the correct angle by indicating the tapered part of a solid toolholder like a setscrew holder that's held in the spindle (as opposed to a collet). With the mill spindle held in the lathe spindle, and the bottom bearing held in the steady rest, you can recut the taper with a carbide insert boring bar. You need to do several spring cuts, but will end up with a very smooth, accurate and serviceable spindle. If you need to clean up straight parts above the taper, now is the time. I always remove the collet key screw, all it does is cause trouble.

[The Metal Butcher]

Not an expert, but FWIW our 1hp Bport has a large gouge all the way around in the middle of the taper, and it's never caused any problems.

[Sparky_NY]

Later models than I've worked on?

70's and 80's machines

[tom_d]

I always remove the collet key screw, all it does is cause trouble.

Yes, that collet screw tends to cause more trouble than it's worth. If the threads on the draw bar and collet are clean, which should be the case anyway, the screw is not needed.

Blue the taper and check against a solid end mill holder, not a collet. You'll get a better picture of the taper's true condition. Things need to be seriously whacked before re-cutting is justified. A little time spent with a half-round stone and some oil should address most of the sins.

Before you get too worried about the spindle run-out it's best to remember that you're dealing with a Bridgeport, world renowned for its flexibility, not its ultimate accuracy. While 3 tenths TIR isn't perfect, it's not the worst Iv'e ever seen. It's a Bridgeport, not a Sip jig borer.

[wierdscience]

The last 3 I rebuilt I just bought the bearing kit from H&W and used the supplied grease that came with it. No problems with heating, all three stabilized around 110*f after run in.

Have you seen Stan's video on regrinding your own spindle?

https://www.youtube.com/watch?v=CFAkb93_V3M

[reggie_obe]

I'll ask this, what's your goal and what's your budget? If you want the spindle as good or better than new, maybe send it to a company specializing in rebuilding spindles. You're in New England, maybe call J&L Scraping and ask who he would use for a spindle rebuild and taper regrind.

[JRouche]

I am solly, too busy to read all the replies so... I have two spare good spindles. That in my ventures is easy to get. The bearings. When ever I saw an auction for these old machines I always went. Always looking for bearing sets, they have to be a set and I think there is a third one that is also of a serious tolerance.

Dang bearings. And new OLD stock. Why? I want to make a mill that takes the same tooling as my BP. JR

[Fasttrack]

So I learned a few things tonight and probably should have taken more pictures but didn't. Anyway, the top bearing and the two matched bearings were open. Not only did this machine not have the "no oil" placard that Sparky_NY showed, but it actually has a small oil cup (which was completely blocked up with grease). The whole spindle was just a big greasy mess and the felt "oil strainer" washer (pictured below) was so caked with grease that, even if oil made it through the oil passage to drip onto it, it never would have made it to the bearings.

After cleaning the spindle thoroughly in the parts washer, I've given it a careful spin by hand and I do notice some slight "coging" on the spindle bearings, indicating wear spots. I thought at first it was just some crud in there so I spent quite a bit of time flushing it with clean solvent and then flushed it with thin hydraulic oil and it still has a slightly hiccup feel to it. I'm still on the fence... I may re-install and use it as is for a while and just figure that I'll pop it out in the future and have the bearings replaced and the spindle ground. Or I might decide to go whole hog and just do it now... haven't decided.

Before you get too worried about the spindle run-out it's best to remember that you're dealing with a Bridgeport, world renowned for its flexibility, not its ultimate accuracy. While 3 tenths TIR isn't perfect, it's not the worst Iv'e ever seen. It's a Bridgeport, not a Sip jig borer.

Understood. I've got a Kearney Trecker 2D for precision stuff and, as of just a little while ago, upgraded from my Cincinnati #2 horizontal mill to a Milwaukee 3H that is in really nice shape (it came out of a shop that specialized in rebuilding Kearney Trecker machines). This Bridgeport is intended to be a bit of a "beater" for quick and dirty work. The trouble is, I'm a perfectionist so it grates at me that the spindle is a beat up. If it's really only a few tenths of runout, well that doesn't bother me, much. It's more the general ugliness of the spindle and knowing that it isn't as good as it could be. Sort of a feeling that I've gone this far, I might as well go all the way.

[Fasttrack]

The last 3 I rebuilt I just bought the bearing kit from H&W and used the supplied grease that came with it. No problems with heating, all three stabilized around 110*f after run in.

Have you seen Stan's video on regrinding your own spindle?

https://www.youtube.com/watch?v=CFAkb93_V3M

Thanks for the link! I had not seen that before.

[JRouche]

flushed it with thin hydraulic oil and it still has a slightly hiccup feel to it.

Bummer. Prolly a burn in you cant dent them. Id still soak them!!! Might still be a lil clump of grease grime that your cleaner wont do. I have a 2000W ultrasonic cleaner for these types of issues. Shoulda came over, I said I had beer?

My unit heats (1000w) the solvent and the transducers or what ever they are called use a kilo watt also.

Kilo..Hahaa. Our electric system along with most systems are Metric. Thats the only reason I know it. They told us in the 70s, learn metric. I love it.

Anyway. Get it to a large heated US tank. Its might pull the crap out. I have never heard of a BP bearing set get a flat spot. Ultrasonic bath is what it might need? JR