Vertical Mill w/Bent Spindle - suggestions?

[Dave_S]

Well, the last laugh is on me. I'm putting the last pieces of the head together after a 3-month restoration on my Clausing 8520 mill, and, spinning the main spindle by hand, it's noticably bent. I'm trying to figure if there's any recourse.

Immediate thoughts -
1) New spindle from Clausing: Even if they had it, cost would be
prohibitive. If the cross-feed leadscrew is $450, um.....
2) Used spindle: Dreamer, eh? It took 6 months to find a head unit
alone (with bent spindle).
3) Straighten it: Is this even possible? I think it's my only hope,
and if it's > $100, I'm just throwing money away.
4) Retrofit a Rockwell/Delta or Bridgeport head: Only if someone's
giving it away.

I've already got $1,500 into an unusable mill.

Anyone else have any suggestions?

Dave

[mendoje1]

Hi Dave, I posted a couple suggestions over at the Yahoo group, but seeing your picture now (great job on your restoration!), you really should just go all out and repair or replace the spindle, and not retrofit a BP M-head (forget about finding a RW head!). $1500+ is not bad considering the current condition. Maybe you could borrow a hydraulic press and have a go at straightening it - what have you got to lose? In high school, I straightened bent fork tubes on my brother's motorcycle (a left turning car cut him off in an intersection). Just took my time, indicated carefully and constantly, and easily got them under a 'thou.

If you decide to make one (or have one made), I'm sure the lathe part is no trouble, I just dont know about the splines. Maybe you could find someone with a shaper who's just dying to use it (try the Yahoo group Metal_Shapers), who'll scrape in the splines for you for fun!. Of course it could easily be done with a horizontal mill, but again, I dont know how much it would cost to buy/grind the cutter. At least with a shaper you only have to grind one small cutting tool.

Good Luck!
Jeff

[Alan]

Dave,
I am sure no expert in this area but I have made a replacement spindle for a floor standing pedestal drill by using an end mill to cut the splines. Had a friend draw up the whole thing using a CAD program which gave me the depth of cut and dividing head rotation. Basically the 2 flanks were done first and then the middle bit was removed on the last pass. If I remember correctly it was only about a 6mm end mill so had to take it easy. Worked really well and was a good fit into the drive pulley spline after a touch up with the file. As mentioned the lathe side of things should not be difficult if you take your time, basically turn it between centre's so you can turn it around without loosing register. I didn't have to do a drawbar hole though. Hope this helps.

[Lou]

Dave,
Looks like you have done a nice job on the mill restoration. It is unclear to me about the bent spindle, is it bent
between the bearings or on the spline portion ?

[Dave_S]

This morning I put an indicator on the MT2 nose, and it indicated .004” out of round. I can visually see the bend in the splined portion, but can’t indicate easily because of the splines. I’d guess 1/8” out of round. At first, I had hoped the bend was only in the splines, but it’s tweaked throughout. Not an easy straightening job, although I’ll probably fuss with it for a while, just because it will only cost me time. Just fyi, I called Clausing Service Center, and they sell the entire quill assembly (quill and spindle) for $941.55.

Dave

[Marty_Escarcega]

You have a nice little mill. If you have $1500 in it, and you put in $1K you wouldn't be too bad. I have seen 8520's in good shape sell for over $2K. It would be worth it to you if you planned to keep it.

You can always find a job shop to make you a new spindle as you have a part to go by. Splines can be cut on the mill I believe.

If you or a local club member have a lathe, have at it. MT2 taper wouldn't be hard to turn and you can find finish reamers easy enough.

It will be a great machine when finished.
Marty

This morning I put an indicator on the MT2 nose, and it indicated .004” out of round. I can visually see the bend in the splined portion, but can’t indicate easily because of the splines. I’d guess 1/8” out of round. At first, I had hoped the bend was only in the splines, but it’s tweaked throughout. Not an easy straightening job, although I’ll probably fuss with it for a while, just because it will only cost me time. Just fyi, I called Clausing Service Center, and they sell the entire quill assembly (quill and spindle) for $941.55.

Dave

[jpfalt]

Straightening is not as bad as you might think.

I would suggest that you make up a dummy taper with a straight shaft if you don't have something like a 3/4 reamer that you can use for setup and measurement.

First thing, check the taper and get it back to a good fitup. Most likely the damage to the spindle happened in a crash and the bottom end of the taper got tweaked and pulled the OD of the spindle nose. The rest of the taper may not be so bad.

Once the taper is a good fit, then take the spindle to the lathe and chuck up on the reamer shaft or the dummy taper and zero it in.

Then map the runout from end to end using a dial indicator to see where the bends really are, paying particular attention to the bearing journals.

Then start tweaking from the spindle nose end using a tool like a shotgun barrel straightener. It is basically a strongback with two loops at the ends and a jack screw in the center to push against the shaft. Usually you go for the big bends first. The target is to get the bearing journals to run true and get any major whips out of the shaft. Anything past the journals and into the splines is much less critical and serves to make the dirve run smoother.

When you've got it as good as you want, you can chuck up and indicate one bearing journal, steadyrest on the other bearing journal and take a very light internal grind on the taper to get it back to 0 - 0.

The process is pretty much mechanical once yu get the hang of it. The big trick is to get repeatable mesurements so you can tweak and check and see progress.

[Dave_S]

Thanks for all the great responses. It seems straightening a spindle isn’t such a big deal. I set up some V-blocks under my arbor press (picture attached), and I’ll start applying corrective pressures after work tonight. My Starrett ‘Final Word’ indicator fits into the MT2 taper, although I’m starting with the outside of the nose to get myself close. In reality, it’s only going to set me back about one week from completing the mill, and that’s only because I reassembled everything before I noticed the problem.

I’ll add this one item to all the superb ‘head rebuilding’ writeups that inspired me to tackle the job: “Before reassembly, check spindle runout, and straighten if needed.”

Thanks again,

Dave