Thread: cracking and chipping on the end of acrylic pen blanks

Originally Posted by redturner

can some one help me with chipping and cracking on the ends of acrylic pen blanks just before i get to the required size i get them on bought and home made ones, thanks steve

Steve

Try working from both ends towards the center rather than running the tool off the end of the work.

I like to use a small bowl gouge ground square across the end (like a roughing gouge).

Cheers

Tim

Drilling from both ends can cause problems if you do not line up the holes perfectly IMHO.

Stepped drills work better, but if you don't have access to one, don't drill all the way through. Most blanks are a bit long, so drill down to the required length, then cut off the excess (ie rather than cutting to length first).

Try using a kit which has big bushes and leaves a lot of meat on the tube. There is not much between the tube and the world with slimlines.

Oops, I had assumed the problem was while drilling, but perhaps you are talking about whilst turning. If so, use small cuts, also cut from inside out (ie from the middle of the blank towards the ends, not from the end).

Always take the ends down toward the bushings first and as others have said cut toward the center and not toward the bushing. No support there.

Had a similar problem myself recently. Was too hasty. Steady as she goes, with light cuts from inside to up outside as previously suggested. Having a sharp tool and cutting as the right angle helps as well. My experience was a bit like a dig-in at the end.

I've had the same problem. Some Acrylics are too Brittle..............possibly too much hardener was used during the mixing process............all of above suggestions from experienced guys will help eliminate chipping problem. take it real slow...............ensuring even pressure during turning.........also mandrell must be perfectly straight to avoid bouncing and that is when you will be guaranteed a chip................if you do get a chip anywhere on the Acrylic and it's still visible upon completion you can use wet sandpaper (400 & 600 grit) gently smooth out the chip then polish up using the Micromesh as usual.............Found this works for me and doesn't leave scratches. Some acrylics are harder then others to fix problems.

thanks guys well done

I agree with Neil and would add my experience. When using HSS chisels I found sharpening them at the start of a pen AND also half way through it as well helps. Resins blanks are hard and abrasive and quickly take the edge of chisels. I made up a sharpening jig using a small face plate , 5'' backing plate and a velcro starter disc to which I used a 5'' , 180 grit sanding disc attached . There is a 1'' hole through the centre of it so a pen mandrel can slip through which enables me to hone more than sharpen on the fly without having to stop the lathe and go down the back to touch up the chisels . Very cheap to make , easy to use and very affective.
Sometimes it's worth making sure there are no nicks or dents in the tool rest as this can cause judders which leads to chipping.

Cheers , Bruce
Wood N Workshop

https://www.woodworkforums.com/f207/r...3/#post1477040
Also check out this, Amos

Originally Posted by bruceh

I agree with Neil and would add my experience. When using HSS chisels I found sharpening them at the start of a pen AND also half way through it as well helps. Resins blanks are hard and abrasive and quickly take the edge of chisels. I made up a sharpening jig using a small face plate , 5'' backing plate and a velcro starter disc to which I used a 5'' , 180 grit sanding disc attached . There is a 1'' hole through the centre of it so a pen mandrel can slip through which enables me to hone more than sharpen on the fly without having to stop the lathe and go down the back to touch up the chisels . Very cheap to make , easy to use and very affective.
Sometimes it's worth making sure there are no nicks or dents in the tool rest as this can cause judders which leads to chipping.

Cheers , Bruce
Wood N Workshop

Hello Bruce Hows things been ? Just read your comment and wondered if there is any chance of you posting a pic of the little tool you are talking about to fine tune/Touch up Sharpening of lathe tools as I might have to look into it ?

Cheers Ian

Having had the same problem recently with chipping and cracking on an acrylic blank I have overcome the problem totally by sticking to timber blanks Not the right response I know

The actual cause of your problem 'MAY' be in the drilling process. I have (when in a hurry to drill) gone a bit too quick in drilling the last few millimeters of acrylic blanks, and introduced a hairline crack in the bottom 5 -8 mm of the blank. Some acrylics are more fragile than others. The crack is so fine that it is VERY hard to see on the square blank, but will always let you know it's there when turning down to the actual pens finished size. You can feel & hear it just before it breaks out, "DIRTY (^%#*&^)*^% " What I now do to control this is to drill more gently, clearing the swarf from the SHARP drill bit, to reduce heat build-up, and on the more fragile acrylic's, I cut the blanks about 8 mm longer, insert the brass tube into the top of the drilled hole, then when glue is set, remove the suspect bottom end of the blank on a sander. Haven't had an Acrylic break-out since doing it this way.

Hey Ian,
here are some pic's of the faceplate sharpener I use, I know it's not a convensional way to sharpen but I've been using this to sharpen all my chisels be they turning or butt for many years now . Every now and then I'll get out the waterstones but for a quick going over I cant beat it.
Cheers Bruce