Long nose live center

Well, tried the MT2 long nose in the adapter today.
















It works but there's more runout than I'd like. Used the cheap MT3 live center for the second stick and it worked better, even if the tailstock has to be extended to almost 90mm, so I'll stick with that unless I need to get a thinner stick.

That said, I remembered that Sorby also makes a live version of their stebcenter so I ordered one to use with another adapter and see how that works, to get a good grip without too much pressure (which bends the stick and creates a bit of chatter and spiral away from the ends).

Today's result.
IMG_20201216_154005.jpg


Swarf City.

IMG_20201216_154510.jpg
 
I have a wood lathe :) A metal lathe is more appropriate for custom pens and I can't turn an almost 9 inch long stick to consistent exact size by hand on a wood lathe. That would definitely kill productivity. I shape and finish each part on a wood lathe.
 
Are you using an insert cutter?
Looking at the surface finish, maybe slow the feed a touch ?
 
Yah, insert cutter, with the uncoated insert that I would use on brass. I slowed down the rpms and it gives me a heavier string that falls down and away instead of getting caught on the piece, so that's an improvement. I don't like the spiral but it happens towards the middle of the stick, I think because it's so long and the rigidity is a bit less towards the middle. It doesn't happen on a 5 inch stick. After I slowed down the rotation (760rpm now), I increased the feed so it wouldn't take forever, but I can try to slow that down to see if there's less spiral, and do it in 2 cuts. I'm currently at 0.0027 r/inch. Can try that on the next blanks!
 
I am not familiar with insert tool, but maybe a different style insert ?
I only use HSS, my lathe is 73 yrs old.......
 
Yeah, it's possible. Unfortunately I don't have enough experience with different styles of inserts to know which would be best here. This is the set I'm using:

BXA Master Turning/Boring Tool Set – Precision Matthews Machinery Co.

www.precisionmatthews.com www.precisionmatthews.com

I used the coated (gold) insert to turn the steel adapter plate for the ER40 chuck I'm using and the uncoated one to make brass mandrels to hold my pen parts in the ER32 chuck on my wood lathe.

Turning the sticks down to size is the only time I'm using the auto feed for this. Everything else is by hand, except for parting. It's all working very well, but getting better results on the first step would be nice. More sanding later means more time spent and less consistent sizes.
 
You could try an insert with a larger nose diameter which should decrease the ridging, but most likely the material is flexing as oppose to cutting the full depth. A CCGT 32.52 may be worth a try, I use the Korloy on aluminum and softer materials, typically a 32.51, but on my ball turner I use a 32.52 due to the ridging with the former. A lot of inserts are counterfeit so always hard to know if it is the real deal, but at $29 worth a try.
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10 pcs KORLOY CCGT 09T308-AK / CCGT 32.52-AK Grade H01 Carbide Inserts | eBay

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I am not sure this will work any better than what you already have:
 
That live center is the one I've been using, the cheaper one that's working well. Would be perfect if it had an extended nose, and a bit more body length. Other than that, it turns without runout and fast enough.

I'll look into the inserts. They seem very similar to the ones I have, but maybe a different nose geometry? I might try that if I get an additional insert holder. The inserts I'm using now are working well for the other steps. I'm wondering if I could use the rounder ones for the other steps. Hmmm, maybe that won't make a difference for that. Worth a try. Thanks!
 
For some closure in this saga :)

The spiraling is not due to the cutter or speed. I'm already going at one of the slowest speeds on the lathe, and the one I'm using now seems to be the sweet spot. Any slower and the string will get wrapped around the piece, a little faster and I get a heavier "chip" that falls down and away from the cutter.

But today I cut a 5.5 inch long stick right after I cut some longer ones with exactly the same settings, and there is no spiraling at all. So it's really about the flex in the material at almost 9 inches long. I'm going to see about changing my workflow to try to cast and use 6 inch long blanks instead and that should eliminate that issue. Less practical but should work out better.
 
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