Minimum wall thickness of wood?

[Davince]

The design of the pen I'm working on uses no finials or adornments, closed tapered ends, cigar like.

If I'd had more time / had put more thought on how to do it, I'd probably have not used the brass tubes, but too late to change that now as I've bought the kit, so...

The brass tubes will finish and the wood will taper off at the ends. If I make the pen so it follows the lines of the kit I have (Mistral) then where it goes from tubed to non-tubed, it's going to be a bit weak, so what do you reckon the minimum thickness of the wood should be? It's going to be burr walnut. I was thinking if I make it thin, I could pour some resin down inside and then re-bore it to strengthen that area up a bit, but that'll give be a faff and increase likelihood of bits of pen flying about the workshop...

 

[Morse]

Hi Del.
I’m not sure I understand your “ from tubed to non-tubed“ question.
I’ve done a few Mistrals and Haven’t had any problem with them.
If your using the bushes for the Mistral I can’t see any “non tubed” areas.
Maybe I’m not understanding your question!

Dave
Having slowly re read your post, the first line says your not using the finials
And you want it to look cigar shaped, I’m not sure how your going to finish it.
Hope the experts on here are able to help.

 

[Davince]

Hi Del.
I’m not sure I understand your “ from tubed to non-tubed“ question.
I’ve done a few Mistrals and Haven’t had any problem with them.
If your using the bushes for the Mistral I can’t see any “non tubed” areas.
Maybe I’m not understanding your question!

Dave

I'm not building the pen as a full mistral, just using the mistral parts I need. I've drawn a rough diagram so you can see what I'm referring to - the wooden "skin" is, if you turn it to match the centre band, very thin, around 1/2mm I think at the point marked, it'll just get broken. I'm wondering what would be a good wall thickness to have at that point to give it enough strength, without it turning into a bit of a fat sausage.

 

[Curly]

He is making closed end pens and is wanting to know how thick/thin the wood can/should be past the point where the tube stops.

If it were me I would put thin CA in the the hole and let it soak in, pouring out the excess and leave to harden. Then carefully redrill the hole to clean it out before glueing in the tube. Once turning and getting close to size I would coat the wood with thin CA as I turned. I would use a CA finish too. Doing so will essentially plasticize the wood. Unless you plan on sitting on the pen often I would think anything over a millimetre preferably 1.5mm should be strong enough.

Pete

Dang I type too slow.

 

[Curly]

Depending on how far into the brass the parts inside sit when assembled you should be able to hold the pen vertically and pour a little high quality epoxy to a couple three millimetres above the "Very thin here!" point thus making the corner stronger.

Pete

 

[Davince]

Dang I type too slow.

But what you typed is very helpful! Much appreciated thanks Peter. The person I'm making them for is... a little accident prone, so being sat on isn't something I would rule out, indeed partly what prompted the question! She's extremely slender build with tiny hands though, so didn't want to give her a big fat pen.

 

[Phil Dart]

You only need the tube to hold one component in place - the nib connector on the barrel and the centre band on the cap. Cut the respective tubes to that appropriate length and drill a depth-measured hole to accommodate them. The remainder of the drilling to depth can be done with a narrower drill, thereby maintaining a greater integrity in the wood at the point where you would ordinarily run out of tube if it were full length

 

[Davince]

You only need the tube to hold one component in place - the nib connector on the barrel and the centre band on the cap. Cut the respective tubes to that appropriate length and drill a depth-measured hole to accommodate them. The remainder of the drilling to depth can be done with a narrower drill, thereby maintaining a greater integrity in the wood at the point where you would ordinarily run out of tube if it were full length

Thanks Phil! That had been my original intention, but then I worried about having the thickness-change point so close to where there would be most pressure in use. I think though I might combine the two ideas now - drill a small hole just large enough for the components further in, depth drill the correct size tube and cut, then reinforce that joint with a bit of epoxy.

 

[Phil Dart]

You could do that. The weakest point though, will always be where there is a change of direction, (at the bevel of the drill in your diagram) so by making it thicker down at the blunt end of the barre you will be overcoming some of the problem. The barrel and cap are both cylinders don't forget, so that in itself will lend some integrity, and if you turn the profile ever so slightly parabolically, that will also help. You've told me in an email that your blank is burr walnut - I would definitely give that a good soaking in CA once you've finished drilling, and gluing in tubes (or parts thereof)

 

[Penpal]

Once again Del your analysis of the future pen is timely and the remarks in time to apply the suggestions. Departing from standard invites the need for thought.

When I married I weighed 13 stone ,my wife 6 stone 7 fooling around as you do I picked her up and carried her across the threshhold,with that she said I can do that,picked me up and did just the reverse. On the 16th of July 65 yrs later my deep respect for my wife and other slim ladies never diminished. I applaud your tireless pursuit of excellence. It also can explain how seeming simple tasks can take on legs of their own hence the shelves of extra products i the workshop.

Kind regards Peter.