Countersinking tenon?

Charl · Post by **Charl** » Mon Sep 01, 2008 2:50 am

Something that has been puzzling me since seeing Kurt's photo essay on stem making: Do you always countersink the tenon, or only do it in case of bent pipes where the airhole is not centered in the bottom of the mortise?
So far in all my pipes I have tried to get the tenon to fit as tight as possible against the end of the mortise, to try and get continious airflow without any gaps, from stummel to bit. And only with certain bents, I have countersunk the tenon.
I might be wrong, bit I've also assumed that the countersinking is to minimise sharp edges so that the pipe doesn't whistle.
Am I right?

Post by **KurtHuhn** » Mon Sep 01, 2008 6:56 am

I countersink every tenon. It might not be strictly necessary, but I think it provides a nice finish on the end of the tenon.

Charl · Post by **Charl** » Mon Sep 01, 2008 12:20 pm

Thanks for your reply, Kurt.
Do you other guys do it as well? Or is it a personal preference?

ArtGuy · Post by **ArtGuy** » Tue Sep 02, 2008 9:06 am

I always do it if for no other reason than it chamfers the hole at the end and takes off any sharp edge that could cause hairs from a pipe cleaner to gather in that spot.

wdteipen · Post by **wdteipen** » Tue Sep 02, 2008 8:31 pm

I countersink all of my tenons. I've heard that not countersinking the mortise can lead to moisture issues. It's really easy to do so I do it as a last step in drilling the stem on all my pipes.

Anvil · Post by **Anvil** » Wed Sep 03, 2008 8:28 am

Ok, I may be the only one here who is a little unsure of what exactly you are counter sinking here. Being new to pipe making, I'm not always up on all the small details that go into the craft. If someone could give a short description of what is happening in this process and where exactly it takes place, it would be very helpful. A picture would be good too. I'm sure that when it is described I will have a V8 moment, <hitting head with open hand> and say oh yeah, that part. Thanks for all the help and inspiration this site gives to people like me.

Post by **KurtHuhn** » Wed Sep 03, 2008 8:47 am

This is a pic of me countersinking the tenon end:

And a link to the entire photo essay:
http://www.pipemakersforum.com/photo_es ... cut_stems/

(note, when looking for the above image, I noticed the photo essay was a little messed up with captions not matching, photos no loading correctly, and photos out of order. I fixed that, so it will make sense now.

)

kkendall · Post by **kkendall** » Wed Sep 03, 2008 11:05 am

Frank · Post by **Frank** » Wed Sep 03, 2008 1:46 pm

Just to confuse you a tad more, most guys lightly chamfer the mortise as well as the outer edge of the tenon.

kbadkar · Post by **kbadkar** » Wed Sep 03, 2008 2:57 pm

kkendall wrote:

Man, you're quick and spot on with them illustrations!

Anvil · Post by **Anvil** » Wed Sep 03, 2008 3:58 pm

Ahhhh, much better! <hitting head with open hand> Thanks guys. I guess I was confused because I think of a countersink more like what the mortise looks like, as in a flat bottomed hole. I would call that a chamfer but that could just be the terminology I learned working in a small engine factory after college. The pictures are great too BTW.

If you are trying to eliminate sharp edges for better air flow or to minimize the area for pipe cleaners to catch or to minimize condensation points, should you also countersink the air hole at the bottom of the mortise?

kbadkar · Post by **kbadkar** » Wed Sep 03, 2008 4:10 pm

Anvil wrote:
If you are trying to eliminate sharp edges for better air flow or to minimize the area for pipe cleaners to catch or to minimize condensation points, should you also countersink the air hole at the bottom of the mortise?

If you use a S&D (rather than forstner) type bit for your mortise, the airhole is already kind of counter sunk/chamfered (especially if centered in the mortise bottom).

Oh yeah, about the countersink vs. chamfer issue - I believe you are right, it is correctly called chamfer... counter sink refers to a screw head flush with the surface, which is done using a countersink bit, which chamfers the surface for the screw.

kkendall · Post by **kkendall** » Thu Sep 04, 2008 10:30 am

Anvil wrote:Ahhhh, much better! <hitting head with open hand> Thanks guys. I guess I was confused because I think of a countersink more like what the mortise looks like, as in a flat bottomed hole. I would call that a chamfer but that could just be the terminology I learned working in a small engine factory after college. The pictures are great too BTW.

If you are trying to eliminate sharp edges for better air flow or to minimize the area for pipe cleaners to catch or to minimize condensation points, should you also countersink the air hole at the bottom of the mortise?

A countersink is an internal chamfer of a hole (like when you want to create a relief for a flathead screw so it would be flush with the surface). Knocking the corners off an external feature would be a chamfer. A flat bottomed hole that is concentric with a smaller hole (a mortise for instance) is a counterbore.

RadDavis · Post by **RadDavis** » Thu Sep 04, 2008 2:07 pm

kkendall wrote:
Anvil wrote:Ahhhh, much better! <hitting head with open hand> Thanks guys. I guess I was confused because I think of a countersink more like what the mortise looks like, as in a flat bottomed hole. I would call that a chamfer but that could just be the terminology I learned working in a small engine factory after college. The pictures are great too BTW.

If you are trying to eliminate sharp edges for better air flow or to minimize the area for pipe cleaners to catch or to minimize condensation points, should you also countersink the air hole at the bottom of the mortise?
A countersink is an internal chamfer of a hole (like when you want to create a relief for a flathead screw so it would be flush with the surface). Knocking the corners off an external feature would be a chamfer. A flat bottomed hole that is concentric with a smaller hole (a mortise for instance) is a counterbore.

All this technical talk is making me dizzy.

Rad

giospro · Post by **giospro** » Thu Jun 11, 2009 11:53 am

What size Countersink do you use for this? and it it the same as the mortise?

Post by **KurtHuhn** » Thu Jun 11, 2009 12:23 pm

Without trying to sound like too much of a buttmunch - the size that works.

Any size will do, as long it is larger than the tenon diameter. I think that's really the only requirement.

Olivier · Post by **Olivier** » Thu Jun 11, 2009 3:50 pm

Just to throw another spanner into the works........... Would it be "politically correct" to drill the mortise with a standard drillbit and then chamfer the outside of the tenon to the same angle as the tip of the drillbit to get a perfect fit or is a flat bottomed hole/mortise with a tenon as Kim illustrated in his pic the standard practice ?

And a question on the countersink. Just how deep should a countersink be ?
The way I see it a depth of more than 0.5mm is kinda overkill. Larger countersink = more turbulence = more space for goo to collect.

kbadkar · Post by **kbadkar** » Thu Jun 11, 2009 4:01 pm

I chamfer the tenon exterior to match my mortise bit. I like a nice snug tenon-mortise airhole junction. Some say leave a little gap to account for wood swell and tar absorbtion. I don't, but I have had to shave a little tenon off when I noticed a new light gap between stem/shank.

When I have a straight pipe with airhole centered in the mortise, I don't countersink the tenon because it seems counter-intuitive to the whole "no air gap, no turbulence, smooth uninterrupted flow" idea. I've never had pipe fuzz issues. When I make a bent and the airhole is not centered in the bottom of the mortise, I ramp the airhole and slightly countersink the tenon to make sure I have a good pipe cleaner feed, back and forth. I have kind-of noticed that these pipes tend to accumulate condensation slightly more rapidly, but this probably has more to do with the bent stem airway resistance rather than the tenon-mortise airhole junction "gap" turbulence. I don't worry about goo collection though, since I clean my pipes before they taste gooey, which isn't very often really. Perhaps it's more of an issue with aromatic tobacco smokers. Still, it's easy enough to swab a countersunk tenon and mortise bottom.