# Chipping Workpieces At Headstock



## hobby ist (Apr 1, 2016)

I am very much a metal lathe newbie and I am running into a problem using my LMS Deluxe 5200. I am trying to turn a plastic pen parts but on the headstock end the plastic always chips out right at the end. The tailstock doesn't have this issue. And I really have no idea why it's causing it. I am using a QTCP and tried the triangle cutters that angle both "away" and "toward" the headstock. The lathe is pretty much in factory settings/condition. Thanks for any help.


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## TommyD (Apr 1, 2016)

What kind of chip you trying to take? It almost sounds like you are turning on centers? What rpm's and cutter feed rate?


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## Wreck™Wreck (Apr 1, 2016)

You have not mentioned how you are holding the parts at the spindle.


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## derf (Apr 1, 2016)

Insert tooling won't work well with acrylics. Use a sharp edge HSS tool.


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## hobby ist (Apr 1, 2016)

I forgot to  say, I tried it at very slow speed and high speed and in between and it still would happen.

I am turning between centers as well.

_"Insert tooling won't work well with acrylics. Use a sharp edge HSS tool."_
The inserts are these: TCMT-21.52 Carbide http://littlemachineshop.com/products/product_view.php?ProductID=3417


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## seasicksteve (Apr 1, 2016)

Wild guess on my part but it looks like the center is flaring the metallic tube causing the acrylic to chip. If your turning with the carriage moving toward the HS the tool pressure could cause the flaring effect on the HS end. If you have a chuck try to turn a tight fitting mandrel with a shoulder so end of the pen body can butt up against it. +1 on the High speed steel tool


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## hobby ist (Apr 1, 2016)

seasicksteve said:


> Wild guess on my part but it looks like the center is flaring the metallic tube causing the acrylic to chip. If your turning with the carriage moving toward the HS the tool pressure could cause the flaring effect on the HS end. If you have a chuck try to turn a tight fitting mandrel with a shoulder so end of the pen body can butt up against it. +1 on the High speed steel tool


I tried with and without bushings but it didn't help. As far as that flare effect I think that's just from debur/reaming it to clean up the inside and it pushes into essentially "empty" space as the tolerance is not super super tight between the tube and the plastic.


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## ARKnack (Apr 1, 2016)

My son use to do a lot of pen turnings. They are really ment to be done free hand on a wood lathe using a skew chisel. Crank the speed up and use a high angle HSS tool bit that is very sharp. Maybe even a vertical shear bit grind. Also be sure you have 100% glue coverage on your brass insert. Personally I think you are also taking to heavy if a cut. 

You could make a tool rest for your metal lathe and use a skew chisel free hand. I have an old metal lathe converted like that.


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## hobby ist (Apr 1, 2016)

ARKnack said:


> My son use to do a lot of pen turnings. They are really ment to be done free hand on a wood lathe using a skew chisel. Crank the speed up and use a high angle HSS tool bit that is very sharp. Maybe even a vertical shear bit grind. Also be sure you have 100% glue coverage on your brass insert. Personally I think you are also taking to heavy if a cut.
> 
> You could make a tool rest for your metal lathe and use a skew chisel free hand. I have an old metal lathe converted like that.


I thought taking even a tiny tiny fraction of a mm off would solve it, but it still chipped out on the headstock end. I was just baffled why this is happening... took a light cut and used a brand new insert and it would happen. I'm still trying to learn the thing so it's hard if not impossible for me to diagnose the issue on my own.


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## hobby ist (Apr 1, 2016)

I'd just like to say I really appreciate all the input as well!


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## hobby ist (Apr 2, 2016)

So this begs the question... if HSS is, perhaps, the key solution, is there a preferred choice for best results (best at maintaining an edge)?

Are there presharped HSS inserts by chance?


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## TommyD (Apr 2, 2016)

Can you dig up a hss toolbit from somewhere and freehand grind it? If you have a way to hold it you can grind a drill bit to make a cutter or even an endmill. 

If you can, you may be able to grind one of your inserts dead sharp, just make sure you grind your clearances.


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## seasicksteve (Apr 2, 2016)

I agree with the above just grind your own. If you prefer insert style tooling here are H.S steel inserts and holders
http://www.arwarnerco.com/c-5-tool-kits.aspx


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## ARKnack (Apr 2, 2016)

Another thing you can try is to start at the ends and work towards the center. That will provide more the material more support while cutting. Also, I'm not sure you want a sharp pointed tool. More like a round nose with a positive or neutral rake may be may be better.


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## TommyD (Apr 2, 2016)

What is the remaining thickness of the plastic at the insert end?

I have seen stuff crack when there isn't enough material left to stand up to the compressive pressure of the centers OR sometimes the pressure of the glue overcomes the material it is bonded in or to. The glue builds pressure against the two diameters and swells upon setting.

Can you turn the diameter up to the insert then rechuck it so only the insert end sticks out and machine that end and, if needed, blend it in with emery?


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## Kevin J (Apr 2, 2016)

You can get HSS inserts from Little Machine Shop.  They are made by Warner but I don't think Warner will sell direct.
Try the link below.

http://littlemachineshop.com/products/product_search.php?critFast=hss+insert&B1=Product+Search


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## dlane (Apr 2, 2016)

Cut blanks, drill hole, light sand tube , paint, let dry,  I use 10 min epoxy ,dental wax tube ends, make sure tube has full glue coverage inside drilled blank, let dry 2 hrs
The ends of said tubes / acrylic must be square, I use a pilot counterbore,  mount with correct bushings for that pen type on each end of tube , should use a pen mandrel with bushings , you are probably useing square pen blanks and turning them round " interrupted cuts" I tried carbide for about 2seconds , not sharp enough ,use hhs ground honed sharp, turner chisels are best , when your close to final size take light cuts with sharp tool and sand to bushing diameter 320-400-600, polish with micro mesh, done
Hope this helps


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## Paul in OKC (Apr 2, 2016)

Carbide inserts are really not good for this type of turning. I am a pen turner myself, but have not done much on the metal lathe. Either a brazed on carbide sharpened to a point, then very lightly 'bumped' to radius the edge, or a HSS blank done the same way will make much easier work of this. You may also try feeding from head stock to tail stock direction, not so much on finish pass, but in roughing go close to the end, then come off and reverse direction.


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## Wreck™Wreck (Apr 2, 2016)

I have had similar effects occur when turning brittle plastic materials in the past, POM (Delrin) for example.


Picture what is happening as the tool nears the end where it will run off of the part, the tool is making the part very slightly smaller in diameter via tool pressure. Not just from the material being removed, it is actually deforming the material.
This works fine at the beginning of the cut for several reasons, it also works well during most of the rest of the cut because the material is constrained by itself on either side of the cutting zone, when the tool point reaches the end where the material is constrained on only one side it will return to its original diameter if in doing so it contacts the tool it may cause a chip. One thing to try is putting a small chamfer on the part at the head stock end, also try a tool with a very high back relief and virtually 0 nose radius,

Good Luck


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## derf (Apr 3, 2016)

Or... you could grind that end with a dremel and a small sanding drum. Stick a boring bar in your tool post for a rest to guide the dremel.


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## Jimsehr (Apr 3, 2016)

I would use a high speed tool with a VERY high positive rake.
jimsehr


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## hobby ist (Apr 6, 2016)

Thanks for the feedback to everyone.

I ordered some HSS and hopefully my lessons can advance


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## Paul in OKC (Apr 6, 2016)

When I taught at the votech, I used a 2x2 piece of wood on a sander as an example of what the tool bit should look like. Made a good visual. Might try that to get a visual on what you want to do with the HSS.


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## Tozguy (Sep 11, 2016)

hobby ist said:


> I thought taking even a tiny tiny fraction of a mm off would solve it, but it still chipped out on the headstock end.





hobby ist said:


> I tried with and without bushings but it didn't help. As far as that flare effect I think that's just from debur/reaming it to clean up the inside and it pushes into essentially "empty" space as the tolerance is not super super tight between the tube and the plastic.



From the picture above it looks to me like the flare on the brass insert may be putting too much outward pressure on the end of the plastic. There has to be some pressure to hold the pen between centers but then the cutting tool adds pressure in the direction of the cut.
Whats more is that the work has probably heated up a bit towards the end of the pass which puts even more pressure on the centers.

Any news on how things got sorted out?


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## 4GSR (Sep 12, 2016)

Tozguy said:


> .........snip...........
> Any news on how things got sorted out?



He hasn't posted since April, just another one that comes and goes as he needs something!

One thing that wasn't mentioned was how he had this set up in his lathe.  Was he chucking on one end and a center in the other end?  If he was, probably had the center tightly driven into the end of the pen blank.  That right there would have messed up the end along with using carbide.  Who knows.....


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## Paul in OKC (Sep 13, 2016)

My guess is he was chucking on a bushing used for the particular pen he was turning. Plus a bushing in the other end with the center into it.The bushing is a size guide for the diameter. If he was doing strictly between centers, he was pushing a bit too hard. Either way, his best bet is HSS. Lots of pen turners use metal lathes for doing their pens.


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## Bill Gruby (Sep 13, 2016)

As said, don't use insert (carbide) tooling with acrylic material. Carbide inserts cut better at high speed. If you run at the extreme low end the chipped end is going to happen. Been there, done that. Use HSS bits and them you can set the speed to your hearts content. Have Fun.

 "Billy G"


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## TakeDeadAim (Sep 13, 2016)

There is one of the pen turning companies that sells an adapter to use wood lathe tools on a metal lathe toolpost.  Not much really but a  rod that clamps in the toolpost to rest your tools on.  I can see from your photos you had no epoxy or CA bond between the brass and plastic material.  I used to scuff the outside of the tubes up with 60 grit then glue on the wood or plastic with a generous application of thick CA.  Granted most of what I made were razors and shaving brushes but I also did quite a few shop pencils for friends as gifts.


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## 4GSR (Sep 14, 2016)

Yeah, I remember my brother getting into the pen making craze way back years ago.  I made several different mandrels for some of the blanks he needed that the common mandrels would not work for his needs at the time.  I haven't looked lately, probably have any mandrel configuration imaginable available today.


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## dlane (Sep 14, 2016)

Tip : if turning a square blank round, try a hand belt sander traveling opposite direction than lathe, get it close to final diameter then use sharp chisel. Gota go light and use corse paper ,lots of dust.


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## dlane (Sep 14, 2016)

Old new pen blank material, it stinks working it tho, 


Thi


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