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Having made pens for a while, the 7mm brass tubes that the kits come with have found their way into some of the pipes I have made as tenons. They have also been used to join shank extensions to the briar because the 7mm hole is a tight fit, and everything slides on nicely. My question is whether or not having a brass tube inside the pipe is big deal or not? I don't see why it would be, but I thought I would ask the experts.

And essentially isn't this basically what you would use a Delrin tenon for? Is there a big deal about using brass instead?

New member by the way, I've been doing a lot of reading thus far and it's nice to meet you all.

The metal of choice for tenons is stainless steel (hypodermic tubing). Brass is pretty soft. I would be worried about it being strong enough and matching the airway diameter closely enough. If its strong enough and the right diameter I don't think it will be a problem.

hey there and welcome,
from a newbie to newbie.

i think that 7mm is a little large of an airway for the north american market, since most people dont put filters in.
and as andrew said brass is soft and could possibly bend more than stainless. there is no health problem, just personal choice on whether you want to have that large of an airway or if you want the tenon material slightly softer.
evan

Also, I would be afraid that the brass would corrode.

No one wants a green tenon.

Todd

The only real problem with brass or any other metal in the airway is that the metal will cause condensation of the moisture in the smoke. This usualy makes for a poor tasting pipe, and always makes for a wet, gurgling pipe.

If you are going to use brass as a tenon, be sure to line the inside with a sleeve of briar, delrin, or whatever your stem material is. Just turn a scrap of that material into a rod that fits snugly inside the brass tube, glue it in there, and drill your airway through it. I have made more than a few brass spigot mount pipes this way, including the one seen below. I have no argument against this method!

I did a little research. Thought I'd share my math and thinking here

6 gauge surgical steel tubing is about as big as is made in the medical industry ... which is .203" ... and I'm pretty sure it's made that size not because it's an even number in any other measuring unit, but because it's the right size for a certain medical application.

Which means you're not going to be able to buy any drill bit that's .203" ... but 3/16" is close, and 5mm is closer, without going over.

Which sure makes the case for Delrin rods sound better. Just because of the availability in sizes that match up to forstner bits.

But the hypodermic tubing isn't too expensive, it just sounds like more work than Delrin, and I don't think steel is going to get you any better of a seal than Delrin either anyway, really. It also adds more weight to the pipe.

Which leads me to a question, forgive me if I'm hijacking this thread a little ... Andrew, what sort of glue do you use for gluing the delrin rod to the stem? Does the glue sometimes get into the draft hole, and if so, how do you solve that problem?

Hypodermic tubing works great if used correctly. It's really no more work than a delrin tenon, just different. The airway I commonly work with is 5/32". My drill bits and tubing are all set to use this tube size. It does not add additional weight, not appreciably so anyway.

I buy my drill bits from a tooling supplier. I can get bits that step a couple thousandths at a time. They're commonly called decimal bits. Different than number, letter or fractional.

You can use just about any two part epoxy for securing the delrin to the stem. Just keep in mind that you are only using mechanical bonding, not chemical. Unless you use some really scary adhesives not commonly available, you'll need to use a few quick swipes of some sandpaper on the delrin rod. Otherwise nearly zero adhesion. You will never get the "3500 psi bond" shown on the epoxy packaging (and that's ok). I also use the same epoxy for stainless tenons. There is no problem getting a good seal on a stainless tenon if you've drilled out your stem with the correct drill bit.

Keep glue out of the airway by putting glue on the tenon, not the mortise.

I think I caught all your questions, maybe

You can run a tapered drill bit into the stem after the epoxy for the tenon has dried to remove any epoxy that squeezed into the draft hole.

Todd

i know this has been dead for quite a while but i was digging back looking for useful bits of information. but if you are looking for stainless steel hypodermic tubing in a size above 6 gauge is get piercing needles. they run all the way up to 0 gauge and are made of great quality steel. plus you can get a box of 100 for 5-10 dollars they are 3 1/2 inches a piece so just grind off the tip and you have super cheap steel tubing for tenons and such.

Hopefully this link takes you where I intended you to go:
http://www.mcmaster.com/#stainless-steel-tubing/=rhu4bu

If not, look for "precision stainless steel tubing" on McMaster-Carr's site. You can find up to 3/8" there.

I do not suggest bare brass for tenons. Brass corrodes easily in wet environments, so if you do use it be sure to line it and treat it right as Walt did above.

Also, be aware that some alloys of brass have lead in them. Stay away from these alloys!