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Deburring a 40 taper spindle

leeko

Stainless
Joined
Jun 30, 2012
Location
Chicago, USA
Hi everyone,

Now that my K&T 2HL is cleaned up, I've been accumulating tooling to use with it. I started measuring the runout of my toolholders, and was disappointed to see about 0.004" at 3" from the spindle face. Worse yet, that 4 thou is consistent across all of my holders, suggesting the problem is in the spindle rather than the tooling.

I blued one of the holders, inserted it and gave it a little wiggle. The blue was intact except for 2 small spots 180 degrees apart at the small end of the taper. I put a finger up into the taper and sure enough, there feels like are small burrs right where the contact points were. Looking with a light, there's a couple of small scratches visible at those spots, and a dark ring all the way around the taper at that level.

What's the best way to debur the proud spots? I have a couple of round India stones, one medium and one fine. Would those be appropriate? Or a small needle file? I'm looking for guidance so i can avoid buggering anything...

Thanks in advance

Lee

Sent from my SM-N920T using Tapatalk
 
Hi everyone,

Now that my K&T 2HL is cleaned up, I've been accumulating tooling to use with it. I started measuring the runout of my toolholders, and was disappointed to see about 0.004" at 3" from the spindle face. Worse yet, that 4 thou is consistent across all of my holders, suggesting the problem is in the spindle rather than the tooling.

I blued one of the holders, inserted it and gave it a little wiggle. The blue was intact except for 2 small spots 180 degrees apart at the small end of the taper. I put a finger up into the taper and sure enough, there feels like are small burrs right where the contact points were. Looking with a light, there's a couple of small scratches visible at those spots, and a dark ring all the way around the taper at that level.

What's the best way to debur the proud spots? I have a couple of round India stones, one medium and one fine. Would those be appropriate? Or a small needle file? I'm looking for guidance so i can avoid buggering anything...

Thanks in advance

Lee

Sent from my SM-N920T using Tapatalk

Get hold of or make a suitable male taper thats softer than the material youre working, its has to cover the surface you want to deburr as per pic. Cover the male taper in diamond paste and roll a bearing over it, this will charge the taper with diamonds, 400 mesh/grit is fine. You now have a decent lap that will maintain its form very well. Lube with some mineral spirits.
Boogers appear in a few swipes and disappear in another few. It will also give you a good indication as to the condition of the spindle taper, if its scored up / bell mouthed etc. With more work you can at least improve these situations too. This approach has worked very well for me.

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I'd like to try Demon73's suggestion. I have a cat40 toolholder i don't need, which appears not to have a hardened shank - a file will bite into it. Would that be an appropriate choice? How would i tell if it's softer than the spindle? A ginger file test of the spindle face suggests it's also not hardened...

Also: would the honing be done under power? If so, what rpm? And should i hand hold the hone? Seems like that might get dangerous if the hone decides to seat into the taper... but, if i fix the hone to the table or vise, then alignment becomes critical i.e. easy to mess up.

Thanks again for your advice,

Lee

Sent from my SM-N920T using Tapatalk
 
I'd like to try Demon73's suggestion. I have a cat40 toolholder i don't need, which appears not to have a hardened shank - a file will bite into it. Would that be an appropriate choice? How would i tell if it's softer than the spindle? A ginger file test of the spindle face suggests it's also not hardened...

Also: would the honing be done under power? If so, what rpm? And should i hand hold the hone? Seems like that might get dangerous if the hone decides to seat into the taper... but, if i fix the hone to the table or vise, then alignment becomes critical i.e. easy to mess up.

Thanks again for your advice,

Lee

You're making this way more complicated than it needs to be. Hit it with an oil stone and be done
 
Hi Sip,

I did do that first. I used the medium india stone in the area at the small end of the taper, where the bluing showed it was hitting. I ran the spindle at 120rpm, with a little mineral oil on the stone. After multiple 30 second cycles, there are still burrs in that area (though smaller). The bluing now shows contact around the circumference, but still only at the small end of the taper.

Never having done this, i dont have a clue how much is too much. Looking inside the spindle with a light, about a cm of the small end of the taper now looks shiny after being hit with the stone - yet the burrs are still there. The tapered hone seems like it might give a little more margin for error...

Lee

Sent from my SM-N920T using Tapatalk
 
Don't run the machine when you do this.
Just go in and stone the area that is high. If this doesn't fix the run-out you need to look someplace else.
 
I'd like to try Demon73's suggestion. I have a cat40 toolholder i don't need, which appears not to have a hardened shank - a file will bite into it. Would that be an appropriate choice? How would i tell if it's softer than the spindle? A ginger file test of the spindle face suggests it's also not hardened...

Also: would the honing be done under power? If so, what rpm? And should i hand hold the hone? Seems like that might get dangerous if the hone decides to seat into the taper... but, if i fix the hone to the table or vise, then alignment becomes critical i.e. easy to mess up.

Thanks again for your advice,

Lee

Sent from my SM-N920T using Tapatalk

As long as the tool holders surface covers the spindle tapers surface and is in as near new condition you should be good to go, be good if its not to weighty too.

Definitely dont do this under power. Is all done by hand.

Get your spindle so as you can see the taper surface, and lock it up. The darker and more grunged up it is the better.
Touch the lap with some mineral spirits and give it a few swipes, the shiny spots you see are the highest of the high points, as you work more will come in. If you get to the situation where 50% of the surface is shiny and equally distributed over the tapers surface, id stop there. In reality youll probably find itll take a bit more work to get the fat end of taper to hit. As long as youve something cleaning up there you should ok.

If youre worried about messing anything up, dont be, he process is very slow. That said, if the spindle taper is in good nick minus a ding or two, itll clean up in 30 seconds. No messing about with blue or stones required. If the spindle is horrible, you have the option to work further and get a result not possible with stoning.

Try it, ill bet youll be glad you did. ;)
 
I just checked my lapping compounds, and i dont have any diamond paste. I do have 500 grit silicon carbide (clover compound). Any reason not to use that instead? Will save having to wait for a delivery...

Thanks,

Lee

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I just checked my lapping compounds, and i dont have any diamond paste. I do have 500 grit silicon carbide (clover compound). Any reason not to use that instead? Will save having to wait for a delivery...

Thanks,

Lee

Sent from my SM-N920T using Tapatalk

Nah dont use that, wait and order up some diamond paste, cheapo off ebay will do fine. The diamonds will embed into the lap surface when you roll them in with the bearing and stay there, and only cut the surface youre working, thats what you want.
 
Ok....

I attempted to lap the spindle this evening.

I used the soft cat40 drill chuck shank
I cleaned it with acetone, made sure no high spots, rubbed 400 grit diamond paste in, ran a bearing over it to charge the diamond into the lap, wiped off the excess then wiped down the lap with acetone. I then put a few drops of naphtha, and put the lap in the spindle.

I turned the lap 10 times, then looked. The picture shows what I'm seeing. It looks like there is a LOT of contact.

2 things, though:

1) the spindle was crashed, and cracked, at some point in its previous life. I had forgotten this. It had been repaired by pressing a tight fitting ring around the outside, forcing the crack back together. The crack does catch on a fingernail, now that i can see it.

2) why do i have so much contact, though, when my blued toolholders only show contact at the small end? Am i doing something wrong with the lap?

I'm guessing the best course of action is to keep lapping until the crack is no longer palpable and the lap marks extend all the way around in the region of the crack. Just looking for some guidance before i do anything irreversible.

Oh, and if anyone knows of a spare spindle for a 2HL floating around, let me know!

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Well it comes out that your spindle is cracked. If it's cracked you can bet that it is also bent.

If it was hit hard enough to crack it, the bearings are trash.

You can lap from now until doom's day and that spindle will never run true.
 
Understood. I've posted a want ad in the tooling commerce forum. Until then, I'll make do with the cracked spindle. It was used daily for ~20 years in a vise factory with the spindle that way, so i guess it'll do until i find a replacement...

Meantime, any thoughts on why the lapping pattern is so different from the blued toolholders?

Lastly, what's the best way to clean the taper after lapping?

Thanks again

Lee

Sent from my SM-N920T using Tapatalk
 
The lapping pattern is different from the blueing because the lapping compound is sticking up much higher than the blueing.

You're just wasting your time trying to lap the spindle true. It's very difficult to lap a tapered hole. You have .004 runout that would take two lifetimes to correct by hand.

About the only way you could correct that much runout would be to mount a toolpost grinder on the table and regrind the taper.

But given you have a cracked spindle there is no guarantee that it would run true after being ground.

You plan of running it as-is until you can source a spindle is probably the best course of action.

Several applications of mineral spirits followed by clean rags will get the lapping compound out.
 
Thanks for the advice. I cleaned things up and reassembled. Actually got a decent improvement - reduced the runout from 0.004 to 0.0015 at 2" from spindle nose. Still not great, but better... the blued toolholder now shows a much more even contact pattern too.

Still going to be looking for a replacement spindle, but this will be better in the meantime. I won't be running tiny cutters so hopefully it won't be much of a problem.

Thanks again,

Lee
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wow, cracked spindle, thats a new one on me lol. Works to your benefit in a way cos you can have it with a clear conscience, and at the very least learn something :D
That socket looks mauled and spun up pretty much like MT3 was. Its only takes a ding or two to give you that 0.004" runout.

Just so were clear here, the idea of lapping (as suggested, imo and experience) can:
i) Quickly remove dings and and burrs.
ii) Remove runout caused by dings and burrs.
iii) Help restore the bearing area on a badly scored up / mildly bell mouthed socket.

If the runout is caused by the taper being physically out of position, for whatever reason, then lapping wont help much. Thats an onsite regrind or rebuild job. :scratchchin::scratchchin: Unless youre really adventurous, confident with a die grinder and dont like ya life :D

If that machine were mine, the first thing id do is not guess the condition of the bearings etc, Id put it down as an unknown atm. If im happy with how the machine runs and the only problem was the runout, id have a go at lapping that socket before going to the trouble of grinding it.

Would probably go something like this:
1) Make the lap and check for sure that it covers the entire surface of the socket.
2) Remove the drive dogs / drawbar and anything else thats getting in my way.
3) Lap the socket until im getting a clean up over the whole surface.
4) Wipe down and check runout with another as new tool holder. If id improved things from 0.004" to 0.0015 id be encouraged im on track and that at least some of that runout is caused by dings.
5) Continue lapping till im getting a good 50% clean up / bearing.
6) Wipe down, mark up the as new tool holder, see what I got and live with any runout till im ready to go further.

If I was in a hurry I might drop 4 and 6 :). Will put up a pic of my efforts if I get a mo, is pretty hard to convey some things over the webs.
 








 
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