Tube Size

[Smitty37]

We talk a lot here about drilling and tube sizes etc., I have often wondered about what problem a slightly oversize hole will cause - I know if you don't drill big enough the tube won't fit.

But, using wood, I've never really seen a problem with the hole being a little too big - now I know that totally oversized the tube might flop around and get a little off center in the hole - is that the problem folks are worried about.

Glue distribution should not be a problem with wood because, it seems to me, there is very little stress applied that would be between the barrel and the tube. Am I missing something.

Where do failures occur? The only tubes I've had break loose has been because of some epoxy left inside the tube causing a problem when I am squaring the barrel.

 

[Carl Fisher]

Here is the way I look at it.

The glue is only there to hold the tube and blank together while spinning on the lathe and ultimately to keep the blank from spinning once assembled.

If you epoxy the tube into a slightly oversize hole and it's a bit off center, so what. You are spinning on the axis of the tube when you turn it and unless you are making something like a sierra where the ends are paper thin, you'll never notice that the tube is not perfectly centered in the original hole. The turning of the blank will accommodate this just fine.

Once assembled, the component ends of the pen hold everything where it needs to be so at that point the glue's only purpose again is to keep the blank from spinning on the tube.

In a rambling way of answering, no I don't see a problem with a slightly oversized hole within reason.

 

[DestinTurnings]

As Carl stated, at the end of the day, concintricity will be achieved during pen shaping. An off center tube will make no significant difference once the pen is assembeled with one caveat...

The off-center portion must be concealed by the component parts to hide the glue joint.

 

[BSea]

It's kind of funny that you brought this up today. I had a change of plans on a blank. It started out with a 10mm hole, but I had a little problem, so I decide to make something else that needed a 3/8" hole. So I just added some sawdust to the epoxy when I inserted the tube, and it is as solid as anything else I've glued. Just be sure that the pen you make has enough meat left so as not to be a problem.

As for the squaring problem, I square all my blanks on the lathe.

 

[1080Wayne]

Only a problem if the glue layer is not thick enough to fill the gap between wood and tube , which is why I use gorilla glue rather than epoxy or CA . Generally only a problem when drilling softer woods where there is significant variation in wood density across the width of the drill bit , or along the length of the hole , but a drill bit can become misguided for a bunch of reasons . Frequently a problem on a crosscut blank where a thin section must be totally supported as you get close to final diameter . Sometimes a problem for me who seldom uses square blanks or round blanks , and almost never drills dead center , because I try to read the grain and maximize visual appearance (Off center puts bit more impact stress on the glue bond until roundness is achieved .) Although I don`t do it , I would think very critical for a segmented blank .

 

[PenMan1]

An oversized hole is a nightmare on acrylics, PR, urathane resins, etc. On many of the component sets, the material is only a few thousandths thick. If the hole is too large, this frequently allows the alternative materials to disfigure or not polish exactly right.

With wood, as long as the hole size is "in the same zip code" of the correct size, the problems can usually be fixed without starting over.

 

[Smitty37]

An oversized hole is a nightmare on acrylics, PR, urathane resins, etc. On many of the component sets, the material is only a few thousandths thick. If the hole is too large, this frequently allows the alternative materials to disfigure or not polish exactly right.

With wood, as long as the hole size is "in the same zip code" of the correct size, the problems can usually be fixed without starting over.

I understand that there are a whole different set of problems gluing the plastics Andy, and I prersonally don't have much of a reference point with them, having done only a half dozen or so pens in the plastics.

I've read of problems with glue mingling with paint, showing through the barrel if the tube is not fully covered, and numerous other things that I don't have any experience at all with....that's why I kind of kept my question in the wood arena.