Thread: Lathe spindle nose protector !

Hi Guys,

I decided to install my ER32 collet chuck the other day to do a small job and realised that all the tiny bits of swarf landed all over the spindle nose threads and register. Not only do they scratch the register when cleaning them off but they are quite hard to remove from the threads even with a tooth brush. I've heard too many tragic stories of people struggling to get the chuck off the spindle and doing damage to the back gears and other parts of the lathe.

I had a short piece of Nylon 60 that was 50 mm diameter ! So I decided to use it to make a spindle nose protector. Now the Myford S7LB has a Whitworth, 1.125" inch by 12 tpi spindle thread, so it was no problem facing off the Nylon and drilling a 1" inch hole through it. I then bored it out to 1.080" Based on 50% engagement. Then I single pointed it from one end to the other using the threading tool upside down and from the inside towards the tail stock. I did wind the saddle back by hand after threading at around 270 rpm.

Having checked the threads with a plug that has the correct thread on it I then bored it out to suit the spindle register to a depth of 1/2" so the the new protector would screw on right up to the register seat.

Now before you guys have a laugh at my expense ! I screwed the protector on to the spindle and it fits exactly as it should
But there is a problem... I now can't get it to unscrew Yes, I did lubricate it first !

It went on real nicely by hand and tightened up against the spindle face !!!

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This is the spindle nose on my Myford S7LB.

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These pictures show the threads and the recess for the register.

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Last but not least the protector firmly stuck on the spindle nose. I put it on there by hand and expected to be able to unscrew it just as easily. But not so it appears.

I would try warming it up with a heat gun, the use a rag around it to undo it.

Try to grip it as close to the left as possible, so it expands rather than contracts when torque is applied.
Maybe some slip-joint pliers over some protective material.

Ditto for Dave's suggestion John, was the Nylon warm when you put it on?......

Will offer my suggestions/explanations if you'll bear with me....I've found that certain acrylics can actually gall on threads irrespective of the fit - how the threads are initially cut can leave minute rough bits that break off in the threads and can cause binding, especially internal threading such as your job ....usually pressure will loosen them but sounds like you tried that already.....if you applied lubricant then you may have compounded the problem and perhaps created a suction with the lube when you screwed it on and after it's dried out etc ???.......also could ask what sort of lube you used and whether it was rated for acrylics.....some lubes will actually dissolve the surface on a few acrylics and that could also be adding your woes.....not familiar with the properties of Nylon 60 at all....??? .

I've found the best lube for delryn and synthetics I've used - if you have to use them at all; is usually a lanolin base such as that made by Inox - (is it Lanox ??)....but try to steer clear of oil based lubes with synthetics - some cause problems

Either way, I would use a heat gun and gently warm up the exterior while blowing cold air from your compressor through the bore to create the temp differential....then have at it with some attitude ..........good luck!......Lee

Nice work with the spindle nose protector and great idea. It does sound like your spindle nose has been protected.... forever!

Just kidding. Sounds like more of a short-term inconvenience than a disaster. Some of the suggestions above sound worth while trying.

Another option (perhaps a last resort) would be to drill two holes in the face of the nylon and then make a spindle C spanner to undo it?

Simon

IIRC nylon is notorious for swelling when exposed to moisture. Try wrapping it in a wet rag overnight?

Graham.

Hi Guys,

Thanks for all your suggestions ! They are appreciated.

I actually used a strap wrench to loosen it. I'm coming to the conclusion that it vacuums itself onto the spindle, probably because I used oil to lubricate it, the same as I would do when putting the chuck back on. It unscrews just as easily as it screws on ! If I don't nip it up to the flat face behind the register, it doesn't stick. Maybe half a turn and its free.

Though I did find that there was some debris in the threads after I got it off.

Thinking out loud, I'm not sure whether to drill a couple of barring holes in it or not since the strap wrench works fine. It would be nice to knurl it !

Originally Posted by BaronJ

Thinking out loud, I'm not sure whether to drill a couple of barring holes in it or not since the strap wrench works fine. It would be nice to knurl it !

Stick it in a rotary table, DH or super spacer and flute it with a ball nose end mill.

PDW

Originally Posted by PDW

Stick it in a rotary table, DH or super spacer and flute it with a ball nose end mill.

PDW

Thankyou for this suggestion !
I like it, and I have a new 6 mm ball ended slot drill that I've had forever and never used.

Pictures will follow.

Originally Posted by BaronJ

.. I'm coming to the conclusion that it vacuums itself onto the spindle, probably because I used oil to lubricate it, the same as I would do when putting the chuck back on. It unscrews just as easily as it screws on ! If I don't nip it up to the flat face behind the register, it doesn't stick. Maybe half a turn and its free.

Maybe remove a turn of thread in the plastic part - it is not a structural part so the thread length is not important, but you might just be running the two thread run-outs together so they are binding slightly.

Michael

Originally Posted by BaronJ

Thankyou for this suggestion !
I like it, and I have a new 6 mm ball ended slot drill that I've had forever and never used.

Pictures will follow.

In the past I have used the lathe to broach grooves into a plastic handle for grip. But then you have to be able to index the spindle to do that.

I would just cut a suitable groove (6mm?) across the face of the protector and use a piece of the same sized bar in the groove to unscrew the protector. Not pretty, but simple and guaranteed to work.

Chas.

Originally Posted by Michael G

Maybe remove a turn of thread in the plastic part - it is not a structural part so the thread length is not important, but you might just be running the two thread run-outs together so they are binding slightly.

Michael

Hi Michael,

You are spot on ! I took just over 2.5 mm out of the threads at the back behind the register. It doesn't stick any more.

I can screw it right back to the face behind the register and can nip it, but no sticking.

However I'm a little disappointed because I was looking forward to milling some nice grooves in the outer surface.

Originally Posted by BaronJ

Hi Michael,

You are spot on ! I took just over 2.5 mm out of the threads at the back behind the register. It doesn't stick any more.

I can screw it right back to the face behind the register and can nip it, but no sticking.

However I'm a little disappointed because I was looking forward to milling some nice grooves in the outer surface.

Make another couple and mill the grooves in them anyway. You are sure to lose at least one.

Originally Posted by BaronJ

I was looking forward to milling some nice grooves in the outer surface.

I differ from you BaronJ....I would have looked for the easiest way out...I wouldnt want to have done any more work than what was really needed