gap between shank and stem

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mikesan

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Have about 4 pipes which have a 1 - 2 mm. gap between shank and stem. All were perfectly flush when new and the gap has developed over time.

Question 1: what may be the cause?

Question 2: How to fix:
--dress the shoulder of the stem
--dress the end of the tenon or deepen the mortise (assuming problem is bottoming-out of the tenon.

Your recommendations please.
 
To determine which is the right fix a couple of measurements need to be made.  First, if you have a dial caliper or depth gauge, measure the depth of the mortise hole  and compare to the stem tenon length. That'll  tell you if it's a long tenon/short notice but not which. If you find a difference in measurement, the problem ma be just klag build up in the motice, since the tenon isn't  likely to have stretched. If so, try scraping the ledge of the mortice with something like a very thin bladed screwdriver to clear the klag. 

Another possibility is build up along the wall of the mortice making the tenon/mortice fit too snug and it's  just binding without seating. Can fix that by scrubbing the mortice with high proof alcohol and a small brush thst just fits the mortice. All the usual pipe and tobacco vendors sell mortice brushes for that job.

Don't  drill the mortice because the fit to the tenon is critical, and the bottom of the hole needs to be flat, not the usual bevel from the nose of a drill bit. Look it over and report back. If you're stumped, PM me.
 
I'm with Slowroll on this one. Give the pipes a good cleaning, especially in the mortise/airway. I'm betting good money that there is a buildup of tars and other goodies stopping the tenon from seating completely in the mortise.

I'll often use the square end of a needle file to scrape the mortise walls and end - tars like to build up in the corners, and it takes surprisingly little muck in the right (or wrong) place to throw off the stem fit.

Good luck and let us know how you make out!
 
That's odd in my experience. The advice you got above is good and I agree that it almost has to be a buildup in the mortise. But I'm curious if all 4 pipes have anything in common? Do you reassemble the pipe each time you clean it? 1-2 mm is a lot of buildup and it is more common that the tenon gets stuck rather than it fits but doesn't seat.
Mike.
 
My thanks to all who have responded.
Both prior to, and after receiving your advice I have tried all the methods which you have suggested. Visual inspection reveals no significant accumulation of "gunk" within the mortise. I agree that drilling out the mortise with anything but a proper square-ended bit would not be advisable, and I have no such bit.
What do you think of the other remedies?
 
How does the length of the tenon compare to the depth of the mortise-is it longer?
 
Just a WAG...

The square end of the mortise may be compromised. A small amount of schmutz may turn the square end to a chamfer. It wouldn't take much to keep the tenon from entering fully. May even be difficult to see.
 
I’ve noticed, since the temps turned coolish, that some of my briars have opened up a very slight gap. Very slight. So slight that I have to hold the pipe just right over a light background to find it. This gap, where present, has no effect for good or ill on smokability. So I’d venture the humble opinion that this is how the pursuit of perfection got a bad name. Just start a “The Hell With It” file, put this problem in it, and enjoy your smoke.
 
Wood shrinks when dry and expands when moist. Pipemakers that know what they are doing, leave a slight gap between the end of the tenon and the bottom of the mortise to accommodate natural swelling of the mortise floor. As mentioned, best bet is to measure the mortise depth and compare it to the tenon length. Chances are, your tenon needs 1 mm taken off of it.
 
Wayne speaks wisely here. Only other thing I can come up with is that the wood at the bottom of the mortise my have absorbed water from the smoke and swollen slightly. Witch would be cured by very slightly tapering just the very end of the tenon. I would advise trying Waynes suggestion first though.

I had a similar issue with one of mine and a couple of twists on emery paper at just the very end of the tenon did the trick. Don't go crazy and do the whole thing and you'll be fine.

Jim
 
Reading through all the suggestions gives me some hope.  This condition has shown up on one, and only one, of my pipes....on my favorite pipe, of course.  All my other pipes, are fine.

Thirty years ago, I designed an extra-large/jumbo size, pipe, and had it custom-made.  The pipe turned out perfectly, and I sure did get my money's worth!  Smoked that custom job for 10-15 years, and then lost interest in piping, and stored that pipe, in a special velvet bag, in a special wooden box, in a special drawer, until just recently.  I'm smoking it again.  The pipe looks just as good as the day it was made....except the perfect fit at the shank/stem interface has opened up by a few thousandths of an inch, and when held up to a light source, I can see a tiny space at the interface where no space existed before.  This tells me only one thing.....the shank/briar has shrunk at that interface, and opened up a slight clearance where stem-face meets shank-face.  Plastic-Acrylic/Delrin stems can't shrink.  Wood can.  Briar is wood.

The only things I am willing to do:

1- Live with it.  Best option.   or...

2- Look for gunk in the mortise (not likely( and/or try to shorten the Delrin tenon by a few thousandths, and see if this will allow the joint to lock up properly.  This would be only a "last resort" remedy, and I have little confidence that this will work.  Why?  Because I think.... (see No. 3)

3- If the shank has shrunk, and the interface is no longer square....no amount of cleaning of the shank or sanding of the Delrin tenon will fix this interface.  Only a lathe will help....and those critical, precision, joint-interfaces will have to be re-machined/re-cut.  Good luck with that!  That's a job I will not do, and is best left to professionals.  I'll pass.

The pipe-carver, who originally made this pipe, machined chamfers/fillets in all the proper areas and was/is an expert machinist, so I know that interface was tight when the pipe was fabricated.  I notice these kind of things.

I am inclined, with great reluctance, to attempt to fix this problem, but I know by experience, that things can go downhill fast if the wrong remedies are tried.  I'm praying that some gunk has collected at the bottom of the tenon hole...but I truly doubt it. The pipe was stored for 20 years, and stored clean.  Where did the gunk come from?   My gut tells me the shank changed dimensions, or shrunk away from the stem by a couple of thousandths.  Hence, the tiny crack of daylight.

Hey....wood changes dimensions.... doors stick, chairs creak, panels crack, tight fits loosen over time.  Why should Briar behave any differently?

After sitting in a drawer for 20 years, I'd open up some clearances too.  


Frank
NYC

Pipe-Carvers....please help:

Upon further reflection, I remain a bit confused. Let me explain.  Let's assume that the shank/stem interface has changed dimensionally over time and the shank has shrunk, become out-of-square.  Here's where it gets confusing.  The shank (briar) remains at the original diameter, at this critical joint, and there is no measurable difference in diameter between the shank and the plastic stem, yet a space has opened at the interface joint?  So the briar has shrunk/pulled away away from the interface in only one direction?  Briar has no grain.  It's a burl. It's wood. And wood with a grain structure, like oak/pine, shrinks mostly across the grain... and the length remains almost the same over time, when compared to the width.  If briar is gonna shrink it will shrink in all directions....it has no conventional grain structure.  The shank should have also become smaller in diameter than the stem.  Presumably, briar is also seasoned before it is carved into a pipe and should be dimensionally stable. See the problem?

Bored yet?


Frank
NYC
 
The first thing you should always check for is crud in the mortise. No crud? Then there is something off with the fit. There must be some head space between the end of the tenon and the bottom of the mortise. Some guys say only a few thousandths, I opt to make mine a little larger, somewhere around 1/16."

Not the problem? Look at the stem very closely. Is the tenon end rounded or square? Is the tenon at the base of the stem a sharp 90 degree angle, or something else? Both of these places can rub on wood that has expanded over time. Round the end of the tenon gently and evenly with sandpaper, buff and done. Not the problem? Check where the stem rubs by covering the face of the stem in pencil graphite. Then insert the stem and take it out. The point of contact will obviously have some graphite on it now. A few quick strokes of sandpaper on the offending area and your problem is solved.

If the face of the shank is truly off, you wont see an even light gap all the way around. One side will be greater than another. By turning the stem you can tell which face it is. If the gap distance doesn't change sides it's the briar that is off. If it does, it is the stem. The pipe should be smoked regularly before attempting to solve these issues as the act of smoking the pipe may tighten up the fit a little. If the problem persists send it to a good repairman. Be prepared to pay $30-$50 for a precision job.

I hope that helps!
 
Ocelot55:

Many thanks for the detailed diagnosis.  After my last posting, I checked the bottom of the mortise area for crud build up, but that area was clean, and will, I think, allow the Delrin tenon to seat properly.  But with a dial caliper, I will take more careful head space measurements.  Maybe I need to shorten the Delrin tenon by more than a couple of thousandths, for a little more clearance and better lock-up.  I'll also rub some graphite onto the tenon/interface areas, as suggested.  Thanks for the tips.

I also looked more closely at the gap between the stem and shank interface and noticed that it is even all the way around this juncture.  There is a very slightly rounded fillet where Delrin insert meets the stem material.  However that tiny fillet fits into a corresponding chamfer that is countersunk into the shank... so I doubt there is any interference at that particular point.

I think you nailed it when you mentioned that if the gap difference is even all the way around, then the briar is off.  Since the stem material (Delrin and Acrylic) cannot shrink or change over the years, then, the briar changed dimensionally, over the last 25-30 years since it was originally machined.  The pipe is now, being regularly smoked again after a very long rest, so I'll wait and see if this gap closes up as a result of regular smoking.  I will be very surprised if it does.

I do appreciate the time spent to consider and answer my technical questions.  I must admit, I am somewhat frustrated by this interface development, and gap.  This custom-made pipe was very expensive, and none of my cheaper pipes show any problems with the stem/shank fit up. Workmanship is definitely not an issue, but I think that briar shrinkage has caused my problems.  The pipe was perfect when it was delivered to my door 30 years ago. Something changed between back then and now.

Bottom line.....No one can predict how natural materials will behave after machining.  Nothing can stop wood from moving.  

As you noted, a professional may, ultimately, be needed to remedy the sloppy fit problems that have developed with my beloved pipe.  :(   That's an option that I may have to consider.


Frank
NYC



Frank
NYC
 
If you're  reluctant to attack the pipe, just wait until spring. In the dryer colder winter months, mortises perversely shrink longitudinally and open a gap if there was not enough headspace in the original fitting.
 
Thanks for that last caution.  I'm hoping, praying on my knees, that the gap was shrinkage.  Maybe with some smoking and air moisture that problematic gap may close.

Didn't think that briar would/could move that much with temp and humidity changes.  I learned something new.

Thanks,


Frank
NYC
 
Here is a simple solution that worked for me. In my vast array of nuts, bolts, and washers, I looked through all the washers until I found one that fit the shank of the pipe, like the one that had the same problem you have. Fortunately, the one I found fit perfectly. The outside diameter was perfect also. Now this won't work all the time, but I guess I was lucky. It fixed the gap problem and also changed the look of the pipe with the "silver band" in place.
 
Very interesting. Up above, I think someone observed that he never had this problem with cheaper pipes. Could be that the expensive, handmade pipes with very precise fitments are more readily afflicted by minor changes in temperature, humidity and storage than their mass produced, more generously toleranced cousins. It’s another exhibit in the lengthy (though highly enjoyable) debate on the question: Is there a point at which the pursuit of perfection becomes an impediment to functionality and productivity? Usually, the other side argues, If you don’t strive for perfect, you won’t reach 90 percent. Good luck with your problem.
 
Not trying to debate this subject ad nauseam, but certain critical details about my annoying "shrinkage problems" don't quite add up.

1-  All my pipes, both cheap pipes and some expensive, all retired to the same drawer for storage.  Only my most expensive, custom-made pipe showed shrinkage at the shank/stem interface.  No other pipes have opened up up any gaps.  Same storage, same humidity, same everything.

2-  Shrinkage manifested only horizontally.  The shank pulled back away from stem, it seems.  The shank diameter remained the same as when originally machined.  This I know, because there is no difference between the shank and stem diameters.  Dial calipers confirmed this.

3-  The tenon could not change length over the years, it's made from Delrin.  I made absolutely sure that the Delrin inserted in the stem is still tightly glued and did not slip, or extend any further out from the stem.  Plastics can, and do wear, but that certainly is not the case here.  Bottom line: the stem remains in the original condition.

4-  The gap is even all the way around, and the stem fits just as tightly into the mortise as when the pipe was originally made.  I could easily spin that stem and it moves around the shank just as smoothly as the day the pipe was made.

5-  Humidity can't be too much of a factor.  I smoked this pipe for 2 months when I was down in Florida.  A state known for humid conditions.  But then again, the house is air-conditioned....ummmmmm????

Conclusion:  The original block of expensive, plateau briar -that the pipe-maker selected- probably needed more seasoning before being machined.  Over the last 30 years, the shank portion must have changed dimensions.  The whole bowl probably changed also, but these changes go unnoticed.  The shank/stem interface is critical, and a change in any dimensions at this one, special, point, shows up quickly, and reveals itself as a gap.

I'm going to wait for some more humid weather to arrive.  Perhaps the sahnk will elongate, and the gap will close up.  

Mr. Corn Cob... suggested an interesting solution to disguise the problem....i.e. interpose a thin washer at the gap, to close the clearances at the stem/shank interface.

Or...... I may have to take off a few thousandths from the length of the Delrin tenon, and see if the gap disappears.  I'd rather make changes to a Delrin insert, than to deepen the length of the mortise in the briar shank.  Its easier to replace a Delrin insert if I screw up badly.  But, I won't.  I'll work slowly and remove a only a few thou at any one time, and take measurements often.

If I really screw up, you'll hear the screaming coming from the direction of the North-East.

Kevein..I could very easily live with the pipe, as is...., and not try to correct, or reduce the clearances.  But it annoys the crap out of me.  The pipe was expensive.  If I ever hand the pipe over to anyone with an eye for detail, it would take only a millisecond for them to discover the gap where there should never be a gap.  But I'll wait, and give it some time to self-correct.  As suggested, maybe some regular smoking will be the remedy.  If not, I have a dial caliper and some sandpaper waiting in the wings.  By this time next year, that gap will be gone.  One way or another, it will be gone.  Then, I can rest.


Frank
NYC
 
I just held a favorite Castello up to the light. There is a hairline gap at the stem/shank junction--not all the way around, just half of it, as though the tenon were crooked. I do believe I will forgo examining others and pretend it never happened.
 
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