Negative rake

[CMC75]

I turned my first acrylic the other day and had a hard time making smooth finishing passes with the tool. Using EasyWood tool on an Inlace Acrylester. It came out really nice but I had to sand starting at 180 to make it smooth.

Would a Negative Rake do me better? My 10 year old son wants to turn acrylic, so this is also a question for make things easier for him as well. Thanks

 

[CMC75]

This is the finished piece. Other than a crack from a blowout while drilling it seems like it came out well. Any advice will greatly be appreciated.

 

[BHuij]

In theory, yes.

I have found my regular radiused square carbide cutter leaves quite a nice surface on synthetics if I simply tilt the handle up to present the cutting edge with a negative rake angle on my finishing passes.

 

[egnald]

I am a firm believer in negative rake, especially on the very brittle Inlace Acrylester material. The material is owned and produced by WoodTurningz. They blanks are cast using a polyester based resin, much like Reichhold PolyLite and they are usually heavily filled with pigments, powders, and other optical grade materials.

The manufacturer/s instruction sheet (link to it here) recommends only using carbide tools with Negative Rake Cutters to turn the material or by using a fingernail bowl gouge or a skew held to give a shear cut to slice the material from the blank. Sharp tools and light cuts to prevent chipping.

Rather than using carbide cutters that are specially ground to have a negative rake, and since I build my own tools, I have made tools that use standard, "flat" carbide cutters. The cutters are fastened to the tool at an angle so that they present a negative rake to the material when the handle of the tool is held flat on the tool rest.

Pens made with this material are usually quite stunning!

Dave

 

[JohnU]

Like said above, negative take will work very well on acrylics but it's not for removing lots of material at one time, It's for shallow and finishing cuts.

I would suggest starting your son on commercial acrylics and not acetate or anything that comes pre chipped. That material is usually very beautiful when turned but the resin is mixed to cure very hot and fast so it's chippy and not a good material to learn on.

 

[randyrls]

Synthetics don't turn quickly. You should get endless ribbons. Present a flat topped carbide bit below center. The further below center the more aggressive the cut and the more force you apply to the blank. Start the cut in the center of the blank and work your way to the ends. Chippy blanks get the corners sanded off on a 5" sanding disk on my lathe. Use the tool rest to support and steady your hands. Do half of the blank at a time. The idea is to remove that sharp corner.

 

[CMC75]

Lots of helpful advice from you guys. Thank you.

I would suggest starting your son on commercial acrylics

John are these all commercial type categories of blanks you speak of? Im still trying to understand all of the blank material. This is from exotic's website. Are the Resin blanks easy turning? There are 3 subcategories under resin?