Lines under resin

[philb]

Hi,

Fairly new to Resin blanks, and on some of my resins when finished there are a few lines. These arent it the finished barrel but almost under the PR.

Its only happen on upper barrel on a Jr.G both times its happened? Do you guys reckon the drill bit is to blame, as thats the only differnce between the upper and lower barrels and the lower show none of the lines?

The blanks are painted on the inside, with water based acryclic and drilled as normal on a drill-press?

PHIL

 

[rizaydog]

You don't have any pics of this do you?

 

[philb]

Im trying to get one, will have to wait till tomorrow for the light though!

 

[philb]

Does anyone sand the inside of the barrel before painting or gluing?

 

[Akula]

I paint the tube and brass...if you scratch the blank when inserting the brass, it will leave a "line" on a transparent blank

 

[ed4copies]

Phil,

Try reading this: http://www.penturners.org/forum/showthread.php?t=79204&highlight=lucite,+cracks

I realize this is regarding lucite, but if you have PR that has been poured with a high "dose" of MEpK, I suspect you are getting a similar problem.

FWIW

 

[philb]

This is a quick pic from my phone, you can see the lines going across the blank?

 

[ed4copies]

No picture that I can see.

 

[philb]

Hows that?

 

[ElMostro]

Seems to me that what you are seeing are the lines left on the brass tube from sanding the tubes or on the iside of the blank from sanding the hole...the resin appears to be a bit translucent so you can see the tube through it and whatever marks are on the tube show through. The cap area may be thicker so you can't see through the resin on the cap.

Eugene

 

[philb]

Well the blank was painted in the inside, so cant be anything on the tube?

So it's got to be on the blank itself, and that has just been drilled not sanded? I'm assuming it is from the drill bit, maybe the drill bit is cutting a slight groove and that why it's still there even after painting?

The blank is transparent-ish, but I know for sure it's not the tube you can see, as I don't sand them in the same direction as the lines present.

Phil

 

[GoodTurns]

just because the blank is painted on the inside does not mean that all of the "drill tracks" have been filled with paint. I have seen painted blanks that show a layer of resin, layer of scratches/lines, then a layer of paint!

I sand the interior of my translucent blanks before painting to minimize/eliminate the lines.

 

[Curly]

Phil are you lubricating the bit when you drill the blank? Soap and water or cooking oil work well and make for a much improved surface finish in the hole.

 

[philb]

No I havent tried lubricating or sanding!

How do you recommend sanding, as you wouldn't want to take of too much from the inside of the hole! Also you would then want to add lines in the other direction!!

Would two coats of paint help?

Thanks PHIL

 

[philb]

I sand the interior of my translucent blanks before painting to minimize/eliminate the lines.

Do you have a specific method for sanding them? As i dont want to add even more lines inside!!

 

[Dan_F]

I've done this a few times for transparent blanks, put the drilled blank in a collet chuck, applied sandpaper 220,320, and 400 on a dowel with 3M #77 adhesive (peel and stick papers would stay on better). With the lathe turning the blank, I insert the sanding dowel and apply a back and forth motion, making sue to vary the pressure on the dowel so that the blank is evenly sanded. This should take out the drill marks, but will make for somewhat larger holes. Remember that if you need to paint the inside of the blank, you can give a few extra coats, which will take up a little of that extra space. I use epoxy, which fills the gap pretty well You could also consult a chart to see if there is an ever so slightly smaller bit that could be used.

Dan

 

[GoodTurns]

I sand the interior of my translucent blanks before painting to minimize/eliminate the lines.

Do you have a specific method for sanding them? As i dont want to add even more lines inside!!

wrap 400 grit paper around an appropriately sized transfer punch and work it back and forth a couple times...kind of like sanding both directions on the surface, just doing it inside the tube!

 

[Dan_F]

Just using 400 probably won't take out any significant scratches.

Dan