Tear out on acrylic​.

[joshua_luther77]

So I was making my second acrylic pen, slim line, and as I was sanding it, I noticed a small chip at the end of it. I took great care in drilling but am curious as to what could have caused this? I'm thinking a combination of milling the end before turning too quickly, applying too much pressure while dry sanding with 220 prior to wet sanding. Maybe the skew caused the chip. Should I only use a carbide tool or is it ok to use a sharp skew for my final finishing pass? Is it ok to dry sand acrylic or does it build up too much heat? Did I just get lucky on my first pen being perfect? I turned it at my lathe's maximum speed then sanded at the lowest speed.

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[randyrls]

Joshua; Is the chip out on the inside or outside of the blank, next to the tube, or on the outside of the blank. I use a sanding jig to mill the ends of all my pens.

If inside, chip out occurred while drilling. If outside maybe not enough glue or small catch with tool.

Use the Cut Blank Long, Drill Blank Short, and Cut Off Far End method on this Wiki Page.

Sorry; Don't forget to paint the inside of the blank after drilling. White spray paint works well but you can brighten the color of the blank by using a similar color to the blank.

 

[ed4copies]

A picture is worth a thousand guesses.

 

[joshua_luther77]

Sorry I tossed it in the garbage. It was frustrating to say the least.

I read the wiki on preparing the blanks. If I make my blank longer than the tube and I have to Mill up the end anyway, what does it matter if it tears out when I'm drilling?

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[D.Oliver]

Depending on the severity of the chip out, it may be able to repair it with CA. I'll let you in on a secret. Very few pens are perfect. Good pen turners are just better at hiding their mistakes.

 

[ed4copies]

Sorry I tossed it in the garbage. It was frustrating to say the least.

I read the wiki on preparing the blanks. If I make my blank longer than the tube and I have to Mill up the end anyway, what does it matter if it tears out when I'm drilling?

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Don't mill the end, sand the end: https://www.youtube.com/watch?v=WA7yEkYtsHU

There are many ways you can increase your chance of success,
You'll find a lot of information here: https://www.exoticblanks.com/How-To-Videos.html

OR you can give up and stick to turning easy things---no harm in that!!

 

[luckyscroller788]

What Ed said is right. Watch a few of his videos, it will help a lot. But, keep in mind as you watch the videos that the one who made the video has had his/her share of disappointments , but practice, patience, and persistence leads to perfection.

 

[jsolie]

Since I stopped using a pen mill and started sanding, I haven't had a chip out like that.

If it happens again, use it as a design opportunity. You can turn the blank down to the tube and then epoxy either a matching or contrasting piece onto the tube. It'll look like you planned it.

 

[bpgoldo]

Josh, there are many ways to deal with a material fail. You can fill the hole, you can cut it back and replace it with another type of material, creativity and patience are the primary tools. Tossing is the most expensive.

 

[joshua_luther77]

I had better success yesterday turning these pens. I took the advice of sanding the blanks flush with the tubes on my disc sander and taking very light cuts once I got close to the bushings. I used a scraper near the edges to get it flush with the bushings and a spindle gouge on the main part of the blank. I finished it off with a skew scraping it lightly. I tried using carbide but got a lot of chatter. I noticed that when it started to chatter when I was cutting it was more apt to chip. My speed was at the highest speed.

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[OZturner]

Joshua, Scrapers, are Not a "Cutting" Tool, a Skew, a Detail Gouge and even a Roughing Gouge are "Cutting" Tools, they actually Cut the Material, whereas Scrapers, and Even Carbide Cutters, are not Cutters, in fact they tear or chip the material away.

If the material is not ductile like Acrylics, their resistance to Chipping or Tearing out a section relies wholly on the strength of the material, hence when you reach the outer edge where there is little or no mass to support the material, so it chips or tears.

What I do, is as soon as I have removed the Square section to a round, at the both ends of the Blank, I Taper then Ends down to near the Bush Diameter, probably back about 1/2" to 3/4", then I proceed to reduce the diameter of the blank.
I use only a Roughing Gouge to reduce the Square, then it is a Skew.

I recommend that you spend a little time with Ed's Youtube posts, you will find most things you need to know.

https://www.exoticblanks.com/How-To-Videos.html

Brian.

 

[joshua_luther77]

Joshua, Scrapers, are Not a "Cutting" Tool, a Skew, a Detail Gouge and even a Roughing Gouge are "Cutting" Tools, they actually Cut the Material, whereas Scrapers, and Even Carbide Cutters, are not Cutters, in fact they tear or chip the material away.

If the material is not ductile like Acrylics, their resistance to Chipping or Tearing out a section relies wholly on the strength of the material, hence when you reach the outer edge where there is little or no mass to support the material, so it chips or tears.

What I do, is as soon as I have removed the Square section to a round, at the both ends of the Blank, I Taper then Ends down to near the Bush Diameter, probably back about 1/2" to 3/4", then I proceed to reduce the diameter of the blank.
I use only a Roughing Gouge to reduce the Square, then it is a Skew.

I recommend that you spend a little time with Ed's Youtube posts, you will find most things you need to know.

https://www.exoticblanks.com/How-To-Videos.html

Brian.

Thanks again for these tips. His videos are helpful. Most of what I was doing when I was turning them, he was showing in his videos. I'm a quick learner and am good at troubleshooting problems with my techniques. I tried several different tools including a skew. I will definitely be using that as well as my roughing gouges in the future when I turn acrylics instead of a scraper. I think my scraper is a 3/8" and I was only using that on the ends taking very light passes. I was probably just lucky that I didn't get any chipping. I did notice that I need to raise my tool rest considerably when using the skew. Also listening to the sounds while cutting tells a lot. I probably won't turn to buffing using a wheel. I got really good results from wet sanding using micro mesh.

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