Best way to fix minor spindle taper scarring?

DeltaVTech · May 19, 2014

Hello,

I just crashed my new VF3 for the first time, broke a pull stud and scared the spindle taper on the top and bottom. This left corresponding scars on the tool holder shown in the attached picture.

I dont think its necessary/cost effective to regrind the entire spindle however I would like to remove the scars because they are causing small marks on my tool holders.

What is the recommended way to do this, is there a ct40 size finishing stone or hand tool well suited for the task?

Thanks,

tc1999 · May 19, 2014

Post a pic of the spindle. There are a number of guys that will come and re-grind and from the looks of that tool holder you need it.

Should be able to search this site for references on different strings.

sfriedberg · May 19, 2014

I would rotate the spindle at about 120RPM (possibly not under its own power), and hold a soft die/mold stone to the interior spindle taper to take off any raised burrs. Fingers don't belong in there, so back up the stone with an ad-hoc wooden or hard plastic holder. There are purpose-made manual stone holders, but I don't have any. Once the burrs are off, stop.

Got an assortment of Boride 1/8 x 1/2 x 6" die stones from Mold Shop Tools a while ago, and most often use a 320 grit AO stone (white) to take burrs and nicks off tooling. The AO stones quickly dress down to the tool profile/radius. Use fluid (plain water works, water with a little detergent is better, kerosene is usually good, actual honing lubricant is best) to keep the stone from loading. If your spindle interior is especially hard, you may need a different stone type than AO, perhaps CS-HD.

Hdpg · May 19, 2014

We had similar damage on a VF1 and one of my guys suggested lapping it with a piece of aluminum machined to the spindle taper mounted on the table. Started with about 200 grit grinding paste and wrote a little loop program to bring the spindle down just into contact spinning at 500 rpm, then lift up and come down again. Every few minutes he would lower the tool offset 0.001 and repeat the loop all the while watching the spindle load. After about an hour he had brought the tool holder runout down from more than 0.002" to a bit more than 0.0001" and we used the machine for another seven years without any problems.

I was sceptical but figured we had nothing to lose and it worked.

DeltaVTech · May 19, 2014

Here are some more detailed pictures, showing the spindle itself and the areas were it marks tool holders(that tool holder was essentially brand new).

michiganbuck · May 19, 2014

Much of the OD taper is still new.., only the high spots are in error. A flat stone can remove OD high places down to a layout die marking to very close to original then hard hone to just witness the original surface on both sides of the scar. A hard hone can take off .00001 or so with careful use so is closer than any machine.
We stoned spindle ID (with a rounded stone) to remove high places and then when almost smooth to bluing used an old taper arbor with keys removed and with 320 clover then finer if bright was wanted to wipe out the very last (almost none) of scaring last of scarring. You don't want to go lower than the original ID. Harder hones are much better than soft as the hold shape and can take only the high places.
If you have grinding ability make a taper a little longer than standard length perhaps a few thousandth under OD is better for the ID lap finish as it will lap the length a little longer than your holders.. but again you want to just make to original.

david n · May 21, 2014

There is thread here some place. PM member took a tool holder, turned off the flange to eliminate the stop notches and removed the pull stud. Coated it in lapping compound, started the spindle, and held toolholder in the spindle. Cleaned it right up. Said if it needed more lapping time, would have lowered the mill head, mounted it some how with a spring under it to provide upward pressure, and let it run for an extended period of time.

allloutmx · May 21, 2014

guy at work did something similar to what David is describing only prior to lapping he cut grooves up the tapper of the tool holder to aid in the lapping. I used the same technique to hone out a marred drill chuck tapper.

IAMATT · May 22, 2014

Grind it, don't mess around.

athack · May 22, 2014

This thread form 2007 is helpful.

http://www.practicalmachinist.com/vb/cnc-machining/spindle-taper-repair-122416/

Athack

Thomas Paine · May 22, 2014

whatever you do, don't forget to blue it to check for fit. that should be normal protocol, but nobody mentioned it yet. Just a reminder.

jimboe · Jun 2, 2014

ever try a "spin L mate "? they're hones made for minor dings

sfriedberg · Jun 2, 2014

I've got SpinLMates in several sizes, but none of the blade sets I've got would qualify as a hone for a solid burr. The "abrasive" blade set will take off varnished cutting oil, but would not be effective on metal. Maybe there's a blade set I don't have for these?

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Best way to fix minor spindle taper scarring?

DeltaVTech

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tc1999

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sfriedberg

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Hdpg

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DeltaVTech

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michiganbuck

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david n

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allloutmx

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IAMATT

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athack

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Thomas Paine

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jimboe

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sfriedberg

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