Turning tennons on pre-formed stems

ASB · Post by **ASB** » Thu Apr 02, 2009 1:38 pm

I searched and searched for an easy way to do this and couldn't find one here on the board, so I decided to drill it out to accomodate the Pimo tool (which I now hate as I have a metal lathe and can get way better tennons on it, as long as I can chuck the stem). As I was drilling (slowly by hand w/ 1/8 bit chucked in head) it grabbed at depth of about 1 inch, not quite far enough for the Pimo tool, but lightning struck, why not leave it "grabbed", turn the lathe on and try to reduce OD. Well low and behold it worked, I had to fight the bit flexing, but after compensating for that angle by adjusting the angle of the cutting tool it worked. I had to put slight back pressure on the spinning tennon (used fingers with a bit of "slippery" cloth) to keep it from flexing too much, and looking back probably could have backed the bit into the head a bit further, but it worked.

FWIW,
Aaron

RadDavis · Post by **RadDavis** » Thu Apr 02, 2009 1:50 pm

Hi Aaron,

Why aren't you chucking the stem in the lathe to turn the tenon?

Rad

ASB · Post by **ASB** » Thu Apr 02, 2009 2:06 pm

Very ovalesque smallish pre-formed stem that 1) my 3-jaw self-centering plate cannot grab (at least on center) and 2) my 4-jaw "manual centering" plate can't grab b/c the jaws won't go in far enough.

RadDavis · Post by **RadDavis** » Thu Apr 02, 2009 2:08 pm

ASB wrote:Very ovalesque smallish pre-formed stem that 1) my 3-jaw self-centering plate cannot grab (at least on center) and 2) my 4-jaw "manual centering" plate can't grab b/c the jaws won't go in far enough.

Ah! You need a 4 jaw self centering chuck. Makes thing much easier.

Rad

ASB · Post by **ASB** » Thu Apr 02, 2009 2:16 pm

Would that work for an oval though? Seems like it would have to be round, or am I missing something. Seems to me the 4 jaw self centering would just grab two sides of the oval, what to keep it from breaking loose or exploding? or can you adjust each plane (the two jaws opposing one another (1&3) together, but seperate adjustment for the other two (2&4))seperately?

jeff · Post by **jeff** » Thu Apr 02, 2009 2:17 pm

Or you can make a tool to do this. Essentially take a piece of 1.25-1.5" round stock (wood, vulcanite, or something hard) and bore or turn a "V" into it that is roughly 1" across and 1" deep. Then cut a notch down the sides of the "V" on two opposing sides. This will allow you to wedge the button into the "V" so that the jig will grip that end of the blank. Then use a live center in the hole of the tenon, and cut your tenon with a cutting tool as you would with a handcut stem.

I hope this helps.

Jeff

jeff · Post by **jeff** » Thu Apr 02, 2009 2:18 pm

And Rad meant an independent 4-jaw chuck. You can adjust each jaw independently.

RadDavis · Post by **RadDavis** » Thu Apr 02, 2009 2:33 pm

jeff wrote:And Rad meant an independent 4-jaw chuck. You can adjust each jaw independently.

No, Rad meant a 4 jaw self centering chuck, you bozo.

Just run your tail stock with a pointy center thingy up near the chuck. Stick the pointy thingy in the hole in the tenon end of the stem. Close your jaws on the stem. See if it spins true. if not, give it another go. It usually only takes one or two tries. When it spins true, cut your tenon.

BTW, you want an oval stem to lie flatish in the jaws, so that the jaws are gripping the top and bottom of the stem out near the edges of the oval.

Rad

ASB · Post by **ASB** » Thu Apr 02, 2009 2:45 pm

I see now, doh! Guess I'm buying a new toy sometime soon. Or I may just grind one part of each of the washers that keeps my independent 4 jaw from closing in enough if I run in to this again.

Sasquatch · Post by **Sasquatch** » Thu Apr 02, 2009 3:02 pm

Don't know if it helps you or not, but all I do for stems is mount a chunk of plywood on the face plate of my lathe, and mark concentric circles on it with whatever tool - make a bullseye. Then I take it off, carve a slot in the center to accept the fishtail on the mouthpiece, and then mount it up, and put the hole in the tenon on the live center. I do this on a wood lathe, and cut the tenons freehand, which is slow and stupid, but so am I.

Frank · Post by **Frank** » Thu Apr 02, 2009 4:22 pm

jeff wrote:Or you can make a tool to do this. Essentially take a piece of 1.25-1.5" round stock (wood, vulcanite, or something hard) and bore or turn a "V" into it that is roughly 1" across and 1" deep. Then cut a notch down the sides of the "V" on two opposing sides. This will allow you to wedge the button into the "V" so that the jig will grip that end of the blank. Then use a live center in the hole of the tenon, and cut your tenon with a cutting tool as you would with a handcut stem.

I think I have a mental picture, just not 100% sure. Any chance of a rough sketch?

jeff · Post by **jeff** » Thu Apr 02, 2009 4:22 pm

Rad doesn't know what he means. Maybe by the time he waxes up his 2000th pipe, he'll get it.

Jeff will let Rad speak for Rad. I must have lost something in the translation from Alabaman to English.

Post by **KurtHuhn** » Thu Apr 02, 2009 4:53 pm

When I turn a tenon on a pre-form stem, I use a collet chuck. Works for oval, round, square, diamond, etc. I used to use a wood chuck with is called #1 Spigot Jaws on it, and that also worked very well, but took some fiddling to get things just right sometimes.

ckr · Post by **ckr** » Thu Apr 02, 2009 5:22 pm

This works well. Basically what Jeff is suggesting.

Take rubber stopper (.39 @ Ace), cut in half, cut Vee, center tenon and tighten. The jaws press into the rubber and hold it very firmly on center.

staffwalker · Post by **staffwalker** » Thu Apr 02, 2009 5:35 pm

If I use a preformed stem I first open the draft to 5/32. I chuck up a tapered 5/32 in the self centering chuck, use low speed on the Taig and drill the stem by hand. It's easy to do, use both hands to hold the stem and go very slow. Pull the stem off the bit often to clear the hole, the bit will easily follow the smaller hole already in the stem. When I drill to approx 3/4" of the button the bit will be quite tight by this time and will turn the stem when you take your hands away. If it doesn't, grasp the stem and while turning clockwise force it further onto the bit. Now put a live center into the hole in the button and cut your tenon. Since you are using the bit chucked in the lathe everything comes out square, the tenon will be centered with the draft hole. I also cut a new shoulder on the stem which will be square with the hole and tenon.

bob gilbert

Frank · Post by **Frank** » Thu Apr 02, 2009 5:49 pm

Bob, I've been using a method similar to yours and it works well enough, but I've been looking for a better method with the tenon at the tailstock end, such as ckr and Jeff describe.

Thanks ckr.

kkendall · Post by **kkendall** » Thu Apr 02, 2009 6:43 pm

maybe something like this?

kbadkar · Post by **kbadkar** » Thu Apr 02, 2009 6:45 pm

Kim, there's a locating pin gauge in the center of that jig, right?

kkendall · Post by **kkendall** » Thu Apr 02, 2009 10:52 pm

of course!

staffwalker · Post by **staffwalker** » Fri Apr 03, 2009 4:50 am

Yeah, see what you are trying to do now. That system should work well. For myself I prefer the tenon at the chuck end. I use a Taig, which, while sturdy still has a certain amount of slop. I have found the closer to the chuck I can get with whatever I am turning the greater the accuracy as there is less vibration there which allows for cutting closer tolerances.

bob gilbert