Pentel Conversion: Acrylics Fractured at nose end?

[Knockologist]

Hello all. I'm still new here so apologies if there is another thread that discusses this. I was unable to find any info.

I'm making Pentel conversions and I like to make them pretty thin, like on the original Pentel P200 pieces. I've noticed that there's a bit of what appears to maybe a fractured line that shows up towards the nose end of the body where the taper goes down to the nose cone. It's hard to see but I've tried to show some examples in the picture below.

I've manually tested the strength and it appears to be strong and doesn't, at least easily, break off.

Is there anything I need to worry about with this?

Also, do any of you add the little lip that's found on the Pentel P200 barrel for the nose cone to sit in? I haven't attempted to add that lip.

 

[Oliver X]

I've never made a Pentel body, but I've been hoarding P205s for about thirty five years. What follows is a series of assumptions: I think what you're seeing isn't a fracture at all. It looks like any sharp edge on the inside of a piece of transparent plastic that hasn't been sufficiently polished. It may be showing up after assembly due to a mismatch in the mating surfaces as I'm assuming that corner is cut with a standard twist drill, and not a flat drill, and when assembled the bottom corners of the hex are gouging the corner and leaving that mark. If that's what it is, it could probably be mitigated by cutting the corner flat with a modified twist drill or by using a small washer. It may allow the mechanism to spin a little too freely, though.

 

[Knockologist]

I've never made a Pentel body, but I've been hoarding P205s for about thirty five years. What follows is a series of assumptions: I think what you're seeing isn't a fracture at all. It looks like any sharp edge on the inside of a piece of transparent plastic that hasn't been sufficiently polished. It may be showing up after assembly due to a mismatch in the mating surfaces as I'm assuming that corner is cut with a standard twist drill, and not a flat drill, and when assembled the bottom corners of the hex are gouging the corner and leaving that mark. If that's what it is, it could probably be mitigated by cutting the corner flat with a modified twist drill or by using a small washer. It may allow the mechanism to spin a little too freely, though.

Aha! Maybe it's the "final" cut of the step drill that I'm using. Thank you thank you!!!

 

[RichAldrich]

I've never made a Pentel body, but I've been hoarding P205s for about thirty five years. What follows is a series of assumptions: I think what you're seeing isn't a fracture at all. It looks like any sharp edge on the inside of a piece of transparent plastic that hasn't been sufficiently polished. It may be showing up after assembly due to a mismatch in the mating surfaces as I'm assuming that corner is cut with a standard twist drill, and not a flat drill, and when assembled the bottom corners of the hex are gouging the corner and leaving that mark. If that's what it is, it could probably be mitigated by cutting the corner flat with a modified twist drill or by using a small washer. It may allow the mechanism to spin a little too freely, though.

I was thinking it is the area where the blank is the thinnest. The line maybe the transition from really thin to thicker. Next one I try I will try to make that area thicker. my 2cents

 

[randyrls]

It is common to paint the inside of the synthetic blanks with either white, or color similar to the blank color. This prevents the brass tube from showing through the blank. It may not be appropriate in this case as it might highlight the difference in thickness.

 

[Penultimate]

I've made the tenon on the end of the blank and the bead on the outside diameter. It's easy with a metal lathe.