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cain8276

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Sep 22, 2020
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louisiana
started turning acrylics with negative rake tools and everything was going good. Now as I'm cutting, I get to about the middle of the blank and it starts chattering and gets worse as I move toward the tailstock. Any suggestions please?
 
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moke

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Dec 30, 2009
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Cedar Rapids, Iowa
Are you sure that the tool is level or tipped up in the back some? If you have the tool so the handle is down lower that the head, you have lost the negative rake aspect.....just a thought...
 

howsitwork

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Jul 9, 2016
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Thirsk
Welcome to the forum.

Depending upon your set up it maybe flexing of the mandrel or slightly too loose. Does it 8mprove if the cut the other way towards the headstock?
 

cain8276

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Sep 22, 2020
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louisiana
Are you sure that the tool is level or tipped up in the back some? If you have the tool so the handle is down lower that the head, you have lost the negative rake aspect.....just a thought...
Thank you. Ill definitely give it a try
 

cain8276

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Sep 22, 2020
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louisiana
Welcome to the forum.

Depending upon your set up it maybe flexing of the mandrel or slightly too loose. Does it 8mprove if the cut the other way towards the headstock?
It improves and totally goes away the closer I get to the headstock. Bought a new mandrel and tried but same problem
 

magpens

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Feb 2, 2011
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Coquitlam, BC, Canada
Part 1 of my comment ....

I was going to suggest going back to the cutting tool you previously used to see if you get any chatter, leaving all else the same.

Could you try that and report, please.

Part 2 of my comment ....

You wrote ....

started turning acrylics with negative rake tools and everything was going good. Now as I'm cutting, I get to about the middle of the blank and it starts chattering and gets worse as I move toward the tailstock.

It sounds like this was a sudden change.
When you started with the negative rake tool, things were fine at first.
Then, suddenly, you began to get the chatter.
Is that right ?

If so, something has obviously changed.
What type of acrylic are you using ? (the most common types are Acrylic Acetate (or AA ) and Alumilite) - if you don't know, then tell us where you bought the blank and the precise name of the blank and we can probably identify the type ourselves.

Is the cutter carbide, and if so, is it a round carbide cutter ?

Check it to see if there is any slight "build-up" of acrylic residue on that part of the cutter which contacts the acrylic blank.

If there is, you can gently and carefully scrape that residue off and try again. . I use an Exacto knife blade to do this. . But try to avoid scraping the "sharp" cutting edge itself ... just scrape the sloping parts on each side of the cutting edge.

This may seem rather "nit-picky" to you, but I have been using carbide cutters for years (but not negative rake) and I have found that residue can build up and it can affect the cutting action.

Hoping to hear back from you about this. . Thanks.
 

MPVic

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Joined
Dec 23, 2011
Messages
300
Location
Hamilton, ON, Canada
started turning acrylics with negative rake tools and everything was going good. Now as I'm cutting, I get to about the middle of the blank and it starts chattering and gets worse as I move toward the tailstock. Any suggestions please?
Had the same experience - getting closer to the tailstock increased the chatter. The live centre in the tailstock wasn't too tight against the end of the mandrel BUT .... I forgot to tighten the set screw onto the quill. After tightening the chatter went away immediately - hope this works for you.
 

leehljp

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Feb 6, 2005
Messages
7,534
Location
Tunica, MS,
I'm late getting in, but another item, do you know what kind of tail stock live center you have? It is critical that you have the correct one.

1. You stated that you ARE using a mandrel.
2. Mandrels REQUIRE that you use a 60° live center in the tail stock
3. Many wood lathes come with a sharper cone than 60°
4. The sharper cones fit into the dimple in the end of the mandrel in the tail stock and the tip-point 1. bends when pressure is put on it from pulling up the tail stock to the mandrel, or 2. when pressure from the chisel is applied to the blank - towards the tail stock end.
5. A slightly dull (but still "seems" sharp to a new user) chisel will require a tad bit more pressure. This in turn, works with the above to increase the chatter.
 
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