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Damaged BT30 spindle. grrr

Houndogforever

Hot Rolled
Joined
Oct 20, 2015
Location
Boring
Had an issue, crashed and broke the pull stud in my speedio 16k RPM machine.

I got it out and have been trying to clean up any damage inside the spindle taper.

It blue's up pretty good, but there are a couple areas that are pushing it sideways.

I've been using a small 1/4" fine stone and laying in there working looking up.

Any tricks to doing this well and not fucking things up worse than I already have?

Using a maritool standard, I was getting almost .003" TIR at 5" from gage line.

Got it down to .0015 TIR at 5.0" from gage line.
edit:
0.0013 at 5" I'm gonna run it and see how she sounds. At a 2" gage line, that should be about .0006.
I'll give it some run time and then recheck after a few hours run time.
 
That sucks! Having dealt with these things myself I guess all I have to say is to only work on the high spots avoiding all other areas, blue tape to mask the good areas is not a bad idea. If the damage is very local I would tend to make the high spots low instead of trying to make them flat again. Get comfortable laying on your back looking up into the spindle, which is hard to do if the vise is in the way. Oh, good lighting too! A small headlamp can be pretty useful for stuff like this.
 
I hate to be a hater, but either have the spindle reground or replace it. It just seems a little HSH to be trying to repair it this way.

Not a hater IMO, this is the way. No shame in regrinding a spindle.

Can just get someone out there to grind it on the machine, no?
 
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I hate to be a hater, but either have the spindle reground or replace it. It just seems a little HSH to be trying to repair it this way.

I don't get out much. What is HSH?

I'll take another look at it tomorrow before I go out of town. I think there is a guy within 30 miles that does the regrind. Maybe I can get an appt next week.
 
Home Shop Harry perhaps?

How do the bearings sound? And change in noise if you spool it up? If there's a regrind guy close you may be in luck, I think most of the cost is usually just travel.
 
There is still hope :)

Put a turning tool with sharp tip on the work table, pointing up.

Program the toolpath, so it takes a shallow cut inside taper. Very shallow, as you dont want to remove much material. Of course, spindle is revolving and your toolpath is on XZ plane, diagonal.

Cross the fingers.

I did it 10 years ago on my Robo and result was fine, still in operation and no taper problems.
 
There is still hope :)

Put a turning tool with sharp tip on the work table, pointing up.

Program the toolpath, so it takes a shallow cut inside taper. Very shallow, as you dont want to remove much material. Of course, spindle is revolving and your toolpath is on XZ plane, diagonal.

Cross the fingers.

I did it 10 years ago on my Robo and result was fine, still in operation and no taper problems.

I did this years ago on a 40 taper spindle and had great results too, but I don't think I would do it for just a few high spots. Especially not if there is a spindle grinding outfit 30 miles away, we don't have anybody local to do that.

I also don't think OP is doing anything wrong by just whittling away at the high spots by hand. Keep going with that, if the runout doesn't improve any further at this point then call in the grinder.
 
If you decide to go the grinder route get a quote first.

I don’t think a new brother spindle is too much. I’d don’t get any firm numbers but I heard about 6k or so on the 27k spindle replaced. Figure the 16k ine must be cheaper

Hey maybe they can upgrade you to dial contact while you are at it and then maybe it will take just a little more of your jokes
 
Hey maybe they can upgrade you to dial contact while you are at it and then maybe it will take just a little more of your jokes

What?! Nobody uses dials anymore, it's all that newfangled push button digital stuff.

Me? I miss ringing up the operator. "Hello, Mabel - get me Lake Side 4-3329. Thanks!"
 
I have hand-dressed to about the best I can ..Then take a taper holder with compound and lapped the last bugs.

Checking it is good to plate check your gage giving it a few 90* turns and marking +- places.

Then putting the spindle at 90* turns and draw a map or the error.

Blue up and a compound turn takes a little off high spots and tell where the high spots are. High spots made a bit under is better than high. If nothing is bent you can get very close this way.
 
Seems like MariTool has “super-strong” pull studs now, (made from H13 maybe?).

Might be worth the investment going forward...

Those are all I use. These might be some of the original Maritool studs that were not High Strength, but he doesn't sell those any longer.
 
The local place doesn't do in place grinding, but there is a guy in Bend that will travel for only a couple hundred.

He will be here Wednesday to re-grind.
 








 
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