What to do about these blemishes?

[ndep]

This is a fauxstone pen and a majestic pen kit.
To prepare the blanks for turning, I first CA glued hardwood to the blank to strengthen the blank.
I drilled using 3 or 4 progressively larger bits.
When turning, I used reverse rake tools at 3600rpm.
I believe these problems occurred during turning on the lathe rather than drilling out the core.

My questions are:

(a) any thoughts on how to prevent these problems from occurring?
(b) are there any convincing ways to repair these flaws?

 

[Dalecamino]

The cracks likely occurred when you press the kit parts into the tubes which expanded the barrel.

 

[SabertoothBunny]

That looks like stress fractures from over tightening when assembling the pen.

Options to fix are disassemble and replace or see if CA glue van be used to fill those cracks and stabilize it some. Not sure what else you can do.

 

[magpens]

I concur with Chuck.

Try drilling out the brass tubes ever so SLIGHTLY at the ends where the pen parts are pressed in.

Carefully measure the portion of the pen parts that press into the brass tubes and upsize that by 5 or 6 thou.
Then, after drilling, use epoxy when inserting the pen parts.

I know that it is hard to select a drill bit for that purpose. . Not all desirable drill sizes are readily available.

It helps if you own several sets of drills ( SAE, Metric, and Letter-size ) and even if you have those there may not be a "most-desirable" size.

Gripping the "blank-with-tube" for drilling can also be a tricky business. . The best way to drill is on the lathe but even then, the pressure of the chuck jaws on the stone blank can crack it, so wrap the stone with masking tape and proceed very carefully . . it takes some practice.

 

[Curly]

The end cracks can occur, but not exclusively from.

A little glue inside the tube that wasn't removed. You can follow Mal suggestion or wrap a little sandpaper around a dowel and sand the inside a little. Or saw a small slit in the dowel, wrapping the sandpaper around the dowel away from the direction of rotation. Put the dowel in a drill. Basically making a flap sanding wheel.

The inside ends of the tube are sharp and the pen parts have a radius. The edge flares a touch when pressed home causing the blank crack. Deburr/chamfer the inside edge of the tube before assembly or better when you put the bushings in. Gives you a second opportunity to catch it.

The end of the blank isn't square to the bore of the tube. One side will hit the part and the pressure of pressing will cause a crack at that point. Greater care when squaring needed.

The pen part was cocked a little when pressing it in resulting in the crack. Excise care when pressing.

Catches while turning can also cause the cracks including the middle one.

 

[qquake]

When it happens to me, and it does, I turn off the blank and start over.

 

[duncsuss]

Since faux stone does not tolerate ANY expansion, the components must be a slip-fit, no pressure needed. You can sand the inside of the brass tube if you can't find a drill the exact size you need. Or you can sand the tenon of the components to get the same effect.

Use whatever glue you feel most comfortable with - epoxy, Loctite, CA - but if it takes any pressure to insert the components there's a high probability you'll crack the blanks during assembly.

 

[jrista]

The cracks likely occurred when you press the kit parts into the tubes which expanded the barrel.

To the OP: I recently had the same thing happen to me. I disassembled the pen, hoping I could salvage the blanks. In the end, I wasn't able to...however once I'd removed the parts of the pen kit from the tubes, the cracks vanished, or at least it took close scrutinization to find them again. The pen kit parts are often large enough to expand the tube, which is all but guaranteed to crack the blank with these trustone/faux stone blanks. I haven't found a solution yet. I ended up ordering some sets of 10.5mm and 12.5mm long brass tubes to replace the originals (I can just chop off the required length).

I have been trying to sand the tubes thinner from the inside, so that when I insert the pen parts they aren't expanding the tube. Not as easy as it sounds...still working on the best approach there. I've been using a dremel with a little drum sander bit hand held, which is not all that effective. I'm now wondering if I can find a way to use a jacobs chuck and my pen chuck on the lathe, to try do this more precisely...not yet sure how that will go.

 

[TonyL]

Unfortunately, I always had to discard and start over with a new blank. Very nice combination though.

 

[ndep]

To the OP: I recently had the same thing happen to me. I disassembled the pen, hoping I could salvage the blanks. In the end, I wasn't able to...however once I'd removed the parts of the pen kit from the tubes, the cracks vanished, or at least it took close scrutinization to find them again. The pen kit parts are often large enough to expand the tube, which is all but guaranteed to crack the blank with these trustone/faux stone blanks. I haven't found a solution yet. I ended up ordering some sets of 10.5mm and 12.5mm long brass tubes to replace the originals (I can just chop off the required length).

I have been trying to sand the tubes thinner from the inside, so that when I insert the pen parts they aren't expanding the tube. Not as easy as it sounds...still working on the best approach there. I've been using a dremel with a little drum sander bit hand held, which is not all that effective. I'm now wondering if I can find a way to use a jacobs chuck and my pen chuck on the lathe, to try do this more precisely...not yet sure how that will go.

If you sand the inside of the tube, then how are you making sure the pen parts still have a tight fit? Glue?

What about sanding the tube exterior down to a slip fit, and then sanding the ends of the tube to provide some expansion room during assembly?

 

[ndep]

Since faux stone does not tolerate ANY expansion, the components must be a slip-fit, no pressure needed. You can sand the inside of the brass tube if you can't find a drill the exact size you need. Or you can sand the tenon of the components to get the same effect.

Use whatever glue you feel most comfortable with - epoxy, Loctite, CA - but if it takes any pressure to insert the components there's a high probability you'll crack the blanks during assembly.

Would you slip fit all the components (tubes + pen parts)? If so, then would you use glue in final assembly or would you use a pen press?

 

[RichAldrich]

I do not try to repair the blank or try to save the brass. Discard both and start over.

Mal's suggestions are really good. Especially measuring with calipers. Sometimes there are variations in the sizes of the pen kit components.

I measure and write on paper the size of each component and the bushings and brass. Eliminates a lot of failures at assembly.

I like to dab a bit of 5 min epoxy to the pen components on insertion. I think it lubes it a bit. Ha.

 

[jrista]

If you sand the inside of the tube, then how are you making sure the pen parts still have a tight fit? Glue?

What about sanding the tube exterior down to a slip fit, and then sanding the ends of the tube to provide some expansion room during assembly?

With glue, yes. Its not ideal...but, I don't know how else to prevent tru/faux stone blanks from cracking, especially with the higher end rollerball and fountain pen kits. There are often parts, plastic usually, that have to slip pretty far into the tubes, and I think that is one of the main reasons I've been having the problem. Ideally, it would all be a tight fit...but I think thinning the tube down to a slip fit and gluing is the only solid way to avoid the problem.

Regarding sanding the tube exterior...I'm not sure how that would help. The tube fit in the blank isn't really the problem. One way or another, any gap between the blank and the tube will be filled with glue. The issue is the fit of the pen parts inside the tube. If you think the tube out from the inside, then you reduce the amount of outward pressure the pen parts exert on the tube and the finished blank.

 

[duncsuss]

Would you slip fit all the components (tubes + pen parts)? If so, then would you use glue in final assembly or would you use a pen press?

I don't understand the question the way it's worded.

Making pens isn't rocket surgery, let's not try to make it complicated: drill the blanks and glue the brass tubes in; turn the blanks to size and sand/polish; assemble the components of the pen into the brass tubes (which are inside the blanks.)

It's that final step - assembling the components into the brass tubes - which is causing the splits, simply because the components are a smidge bigger than the hole you are trying to push them into. Don't push. Sand the inside of the brass tube, or sand the part of the component that inserts into the brass tube, or sand both. Doesn't matter which way you do it - but the part must slide into the tube without force.

Which means it will slide out again unless you use glue to hold it in there. I like epoxy, but I have also used CA.