A wee bit of advice, especialy to new pen turners.

[Woodfreak]

Hi. Just a small piece of info to impart to the more novice pen turners. I have made a fair amount of classic fountain pens and roller balls. I am talking about the ones with center bands in the middle. I found that when you come to turn a 5mm tenon down to the brass tube for the centre band to fit on, its fine to just use a small parting tool to cut it back. I am talking of wood here. If you do the same with acrylic, or a plastic based product, I found as soon as I got down to the brass tube, in acrylic it spoilt the cap by chipping it. I got over it by measuring the distance that I needed to take the acrylic of, and with my skew turned perpendicular, cut a line down to the brass tube. The once you have cut the line, when you take the rest of the small band size piece of acrylic,, it will not chip, therefore not spoiling and expensive acrylic blank. Hope this helps.

 

[monophoto]

Paul -

I'm just speculating here, but I suspect that your parting tool experiencing some lateral (side to side) vibration when you are cutting the tenon up to the edge that meets the center band of the pen. Wood is resilient and can absorb that vibration, but plastics tend to be brittle, and the vibration causes some cracking.

The effect of your suggestion to make a cut down to the tube first, before starting to slice back the unwanted material to make the tenon, means that the parting tool is confined within that cut and therefore is unable to vibrate, thereby eliminating the cracking.

Your suggested approach is problem prudent regardless of the material being turned. If nothing else, adopting that as a routine practice means that you don't have to stop and ask yourself what material you are turning.

 

[Woodfreak]

Very aptly put, and perceptive. Thanks Louie.

 

[qquake]

I've never had a problem cutting tenons in acrylic with a parting tool, but that's still good advice.