Bent spindle on a BIG Gisholt?

lc · Aug 30, 2003

I've been working on a big Gisholt at work, disassembling till we find the cause of the stuck spindle. After loosening the rear bearing we could turn it with a 8' 2x6. It turns on a constant loosening and tightening cycle as it goes around. There isn't a "hitch" at all, it's very smooth all the way around. Indicating the front and rear chuck mount faces we got .002" and .001", respectively. This is on the 24"(+/-) diameter of the outer ring of the chuck mount. I can't figure how anything but a spindle can make it do this 180 degree tight to loose pattern. Anyone? This is a 19 1/2" spindle bore tracer, about 75' of bed length when bolted together.

winchman · Aug 30, 2003

How do the positions of the highest and lowest runout readings line up between front and rear chuck mounts? Are the two mountng surfaces closer together on one side of the spindle than on the opposite side?

If that's the case, I'd suspect the spindle is bent AND one or both of the bearings are skewed. That would explain the 180-degree loose/tight pattern. If it was just the spindle, the binding would be consistent all the way around. The bent spindle lines up perfectly with the skewed bearing(s) at one point and has the maximum mis-alignment 180 degrees away.

Please be advised this analysis is from someone who wouldn't know a Gisholt if it ran him down, but it seems like a reasonable explanation for the problem you've described.

Roger

icehd81 · Aug 30, 2003

You could also have a gear problem. Bending a spindle that size would have been a feat in itself. However, years and years of use and a lot of fretting corrosion could cause too loose a fit of the spindle gear on the spindle. Secondly, a sheared key or spline caused by a sudden forced stop could result in the spindle gear or it's mating gear to run out of round. Same symptoms of a bent shaft, but in this case it's the gear backlash that is changing as you turn the spindle. About the only way I can think of to bend the spindle is for a gear tooth to break off and go through the gear mesh. Either way, you are looking at significant tear down to repair.

lc · Aug 30, 2003

The runout high spots on the spindle are 180 out, throwing a wrench in the bent theory for me. There isn't an gear tooth vibrations form the straight cut gears when it binds... Haven't measured the "length" situation yet, sounds like a good idea. This lathe was a government military job and seeing as how the bed length is so long I'd guess maybe used for the BIG gun barrels. If they had a wreck with one of them onboard there'd probably be plenty of momentum to pretzel the spindle, or anything else inside?

icehd81 · Aug 31, 2003

That could indicate the intermediate shaft or gear. Have you poped the top yet? I'd venture a guess that your gear ratio between the intermediate gear and your output gear is 2:1. If that's the case check for backlash at the tight spot. There probably won't be any. Then rotate the spindle 90 degrees and check again. If you have considerable backlash at that point your problem is likely there.

JRIowa · Aug 31, 2003

We have a lot of Gisholts, and I have never seen a bent spindle yet. I have seen the tool posts knocked off the cross slide and jaws torn out of the chuck, but the spindle was still good.

You need to check the clutch/brake assembly for binding. The gearing in the headstock could also be a problem.

My guess, somebody already had it apart and didn't get the bearings back on square.

JR

lc · Sep 1, 2003

I have the headstock on 4x4's on the floor because someone was sure there was something jammed in the gears underneath, nada. There is nothing connected to the spindle (gears or otherwise) at this point. It has to be the spindle bearings/hedstock/spindle at this point. Wondering about a misalignment of one or more bearings, but I can't figure how that can produce a tight/loose cycle. Seems it'd be tight all around for that problem. It looked like it was apart before we aquired it, duh! The only thing I've found interesting in this direction is that the front bearing nut is a split tpye and the socket head screw for that weren't tightened down. There's a nut that holds the gear and spacer stack tight that also pushes against that same bearing nut, and it was tight. I say whomever had the lathe before knew they wrecked pretty serious and did a quick bearing adjust and gave up. Hmm. sounds a lot like the mechanic work I quit for this job. "Can't figure it out?, let this fool work on it!"

drof34 · Sep 1, 2003

Pop the top and put an indicator on the spindle as close to the center as uou can get, if you can get to the spindle at all. Then you will know whether the spindle is bent or not.
Jim W.

lc · Sep 2, 2003

I'll try that tomorrow but the best I can do is about 6-8" in from the left end. It's stacked with gears and spacers the rest of the way.

scottie · Sep 2, 2003

is there a possibility that one of the gears
on the spindle is cracked,thus binding on its mating gear? just an idle thought.
scottie

winchman · Sep 3, 2003

I'm having a hard time getting the scale of this thing. Sounds like the spindle may be several feet long and about two feet in diameter. Is that anywhere close? I sure would like to see a photo of this machine.

Measuring something that size to the accuracy required to determine the source of the problem must be a challenge in itself.

Roger

lc · Sep 3, 2003

Scottie, there aren't any gears connected to the spindle gears at this point. We have "neutraled" everything to eliminate that possibility.
Winchman, you're pretty close. The spindle ID is 19.5", I trying to remember but I think the swing is 37". The headstock's rough outside dimensions are 50"x44". There's about 75' of bed length with all sections hitched.

adammil1 · Sep 3, 2003

Ic

While I really can offer no advice as the largest lathe I've worked on is a 13" leblonde which from what you've described may be able to fit into that headstock. None the less I enjoy reading about fixing such a beast. I've always been fascinated with these large machines. I'd love to see one in operation but in the mean time is it possible for you to post some pics for those of us who are just fascinated with such machinery. Also just out of curiosity what is a machine of this size being used for and where is it?

Thanks in advance,

Adam

lc · Sep 3, 2003

I don't have any simple way to get pics of the darn thing onto the www. Maybe I'll stop and pick up a disposable and get them disk'ed.
We're located in Eugene,Oregon, and for sure won't be using it to anywhere near it's potential. We're drilling equiptment manufacturer(pipe, hammers, bit's, reamers)and probably won't ever have a reason to reassemble the bed sections. Most all we do is 20' or less.
The worst part about this fixing situation is that I've been there just at a year and it's been there, doa, longer than I. Noone in the shop has ever seen it move. A couple of the fellas got to wiring it and when the go switch was touched, clutches smoked. Apart it goes.

DMSentra · Jan 10, 2015

lc said:
I don't have any simple way to get pics of the darn thing onto the www. Maybe I'll stop and pick up a disposable and get them disk'ed.
We're located in Eugene,Oregon, and for sure won't be using it to anywhere near it's potential. We're drilling equiptment manufacturer(pipe, hammers, bit's, reamers)and probably won't ever have a reason to reassemble the bed sections. Most all we do is 20' or less.
The worst part about this fixing situation is that I've been there just at a year and it's been there, doa, longer than I. Noone in the shop has ever seen it move. A couple of the fellas got to wiring it and when the go switch was touched, clutches smoked. Apart it goes.

Just ran across this again, from my previous posts. ^^^^

We (boss) pretty determined to just readjust the spindle bearings as good as we can and try it. It's been in use since this last post above. The clutch is an electromagnet job, and messing with it all we could it never did get to grab enough to make the high range gears useable, so we modified it to a locked up drive and brought in an electrician that converted it to VFD. Works great, kinda, now as it is. At least it does what we ask.

I did get a few pics of it quite a time back.

Notice the 6" riser block under the spindle, steady rest, and tailstock if you can see it. Added an idler under the headstock and the swing is somewhere "just not enough" again. Oh well, that's how it works. LOL

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