Help help and rescue - Tenon fit

Irish Flute
1

Hi All,

I’ve got a keyless deKeyzer in blackwood that is modeled after a Pratten. so basically I have thread wrapped 2 tenons to deal with. The lower is fine, but the upper seems to have gotten way too tight – the wood at the end actually swells out and contacts the socket when I start to insert it. Yikes.

I figure there are two choices…

  1. chuck it up and turn it down so it is straight

  2. dry it out a bit and see what happens

I mention #2 because I’ve been storing it in a ziplock with a lil’ humidifier in the bag.

What is the likelyhood of #2 working?

Thanks
Dave

2

davemoffsite wrote:


“I’ve got a keyless deKeyzer in blackwood that is modeled after a Pratten. so basically I have thread wrapped 2 tenons to deal with. The lower is fine, but the upper seems to have gotten way too tight – the wood at the end actually swells out and contacts the socket when I start to insert it. Yikes.”

Yikes indeed.

“I figure there are two choices…”

I can think of at least 4, but lets start with your 2.

“1) chuck it up and turn it down so it is straight”

How are you going to chuck it without buggering the outside of the piece to get chucked? What you’d really need is an expanding mandrel, or a properly fit full length mandrel, if you you’re going to do any turning.

Could be another way I’m forgetting at this point, but I can’t recally any good way to chuck a finished piece… Well, actually, come to think of it, if you have collets a draw bar and the facility to make a delrin clamp to fit in the proper size collet, then you could fashion holder to clamp on the small tenon and then support the other tenon on a point center and turn, but the risk of shattering the tenon when turning this way is a reality, although I have done it on occasion.

Anyway, that’s more work than necessary, I think.


“2) dry it out a bit and see what happens”

Might work, but what happens if the tenon swells like crazy again while you’re playing it at some point?

My sugggestion is to let the flute acclimate to whatever humidity you’re going to keep it at in the future, then proceed on to dealing with the tight fitting socket/tennon joint, if that is still a problem. Which leads me to the other options that immediately come to mind in terms of dealing with the tight fit:

Option A. It sounds like you have a lathe, so one option is to mount the center section between point centers (GENTLY! So as not to crack either end) and then sand the offending tenon to fit the socket. I’d go 400 - 600- and finally 1200 grit, using an orbital sanding motion, so as not to leave sanding lines. Finish by buffing with compound on cotton buffing wheel, if you have one. Of course you would have to use a buffing wheel you’ve never buffed metal on. (forgive me for stating the obvious, just making sure for others reading)

Option B. Hand sand the Socket to fit, instead of, or in addition to, sanding the tenon.

My preference would be to do a little of both A and B, especially if the fit is more than just a little tight.


Having said that, alot depends on how much “excess” material there is to work with on both the socket and tenon in question. Better a slightly too thin tenon, rather than a slightly too thin socket, since compresson forces on a tenon are less likely to cause cracks than expansion forces on a tenon, if you see what I mean. So it really all comes down to the looking closely at the instrument in question and determining which part (the socket or tenon) can stand to survive the material loss.


Just my 2 cents.

Loren

3

Heh, heh - I see Eilam is signed on, and bet he’s typing away right now :laughing:

4

This happened to my Schultz flute, which I sent back to Glenn. It’s happening to my Bleazey, which I’m gonna sand down. It’s not as though it will require much material to be taken off – probably a thousandth will make the difference.

I’m beginning to think I’m the problem, since it happened to both flutes that I bought new.

5

Loren - Is this the problem you used crazy glue on the end of the tenon to fix (glue on the end grain which soaks up the most moisture)?

Eric

6

Eric,

More or less ses, this is the sort of thing that sealing the end grain of the tenon can help in many, but not all, cases.

Sealing the end grain works best when the fit is fine while the instrument is dry (before playing), but then expands to scary tight proportions after playing for a reasonable period.

Some woods seem to soak up more wood through the end grain than others, and of course some people are wetter blowers than others, which can help explain why some people can have more problems with tenon expansion on the same flute than others playing the same instrument.

I also think it may, in a few cases, have something to do with the length fit of the socket to tenon joint - meaning how much of a gap did the maker leave between the end of the tenon and the shoulder inside the socket. You can leave them butting directly agains one another because once the tenon absorbs some moisture you get an ugly gap at the socket tenon joint as the tenon expands slightly. OTH, I can’t help wondering if leaving too much of a gap leads to pooling of moisture at the juncture - which could cause (in theory) more moisture to be absorbed by the tenon, particularly on the earth facing side, which (again in theory) could cause cracks due to uneven expansion of the wood on side vs. the other…however I admit that last to be a bit of a stretch, and both of the scenarios in this paragraph are purely speculation on my part, so take that fwiw.

Never the less, sealing the end grain does (in many cases) help combat the “swelling when wet” tenon syndrome, of that I’m sure.

Loren

7

This makes sense. I always make sure put a lot of oil on the end grain, whenever i oil a flute.

8

How much clearance should there be in the tenon/socket fit?

oh - and my intent was to use an expanding mandrel and mount sand paper on a paddle to keep things flat - my understanding is that the tenon is actually tapered, and the end that has swollen on me is supposed to be a hair thinner - is that correct?

Again thanks for all your help

9

Okay - I took it outside to some better light and lo and behold the tenon had been repaired at one time (this is a 2nd or 3rd or ??? hand flute) … and evidently the Krazy glue hadn’t all been removed from the outside of the tip of the tenon. So I (yes carefully) took out my pocket knife and scrapped it down a little - still touches but I have a little ways to go. It is quite likely that when I get all the glue off it will be alright.

Of course it wasn’t sticking when I got the flute, so I might be over humidiying it still, but this is starting to look like less of a project than I thought. Of course I will likely have to rewrap it and that scares me! Wood I understand, but sewing?!?!?!?! Yikes!

In anyevent I am off on a 2 week vacation with my dixon (does better in a hot car) and will finish this up when I get back.

Cheers and Thanks a Million

Dave

OH - and yes I will sand the remainder - I only used the knife on the drip marks :slight_smile:

10

davemoffsite wrote:

“How much clearance should there be in the tenon/socket fit?”

This depends on a variety of factors, including how long the tenon is, how much it’s tapered (and where), how much of the tenon area is corked (ratio of corked to uncorked) and so on.

If it were me, I would remove the thread and sand just until the was no longer any wood to wood contact, then rethread, play for 20 min and see how the fit is.

Repeat as necessary.

If you are feeling brave, sand until you think the difference between the socket and tenon is 5 thousandths…but be aware it’s easy to go too far, and often simply adding extra thread at that point won’t solve the problem of having a wobbly joint, not fun.


Have to sign off before I get logged off the library pc…

Loren

11

Rewrapping tenons is a piece of cake
http://www.flutes.fsbusiness.co.uk/tenon.html

For thread wax, i use the stuff sold in hardware stores (in the US) as “toilet bowl sealing gasket”. It’s 100% beeswax, i’ve been told. One piece will last you a lifetime.

12

Just got more PC time.

Glad to see it’s probably just the glue. Sand paper is good, but a fine file, if you have a narrow mill smooth or very fine nicholson, is even quicker, but only a good idea if your filing skills are up to the task, otherwise go with the sand paper and more elbow grease.

Best,

Loren
P.S. Like Glauber says, thread lapping tenons is a piece of cake, however I personally would suggest avoiding waxing those threads, especially if you flute sometimes is exposed to heat… At Von Huene we rarely ever wax thread lapping, if you use the right thread, it really isn’t necessary, and it’s a lot less messy than waxing. No offense to you waxers out there :wink: