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 Post subject: Stem air hole size
PostPosted: Thu Jul 20, 2017 10:29 am 
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This may be a dumb question but here we go... After reading up on hand cutting stems the consensus seems that a 1/16' slot is drilled at the button, then a 1/8" airway is drilled for the remainder of the stem. Before you epoxy in a delrin tenon it is to be drilled out to 5/32". This leaves 2 shoulders, one at each junction which is removed with tapered bits. Here is my question, why can't the tenon be drilled to 1/8" along with the stem? Since the head of the tenon will be countersunk anyways, it would place the 1/8" to 5/32" junction at the tenon/mortise face. Is the 1/32" drop in this transition to blunt and not allow for a evenly tapered air hole? I attached a sketch of what I am trying to say.


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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 12:07 pm 
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Who said to drill the stem airway to 1/8"? That seems weird to me. I drill with a 5/32" tapered bit to within 1/4" of the other end, then 1/16" from the other end of the rod. I don't have any shoulders in my airway. It's 5/32" from the slot to the chamber.

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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 12:34 pm 
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It is in this method posted on the forum by Todd Johnson, step #5. Unless I am reading it wrong.

ToddJohnson wrote:
This is in response to the inquiry in one of the threads below. I thought it best to make this a new thread. I hope this is helpful for you guys. Hand cut stems can be made and made well *without* a lathe. It's slow, and imperfect, but you can get excellent results by following and practicing the steps below. Familiarizing yourself with your own tools and processes through practice and repetition is the best way to become a better pipemaker.

Bear wrote:
without the pimo tool, better to buy stems?


You can make a very high quality stem simply using delrin tenons.

1. Create some hardwood jaws for your vice that simply have a V-shaped notch in each jaw. Use some grit-tape on the jaws to help them grab the piece of rod stock a bit better.

2. Clamp the piece of rod stock in the jaws, and lock everything in place--the table, the press head, the vise jaws, etc. Make sure your table is low enough that you can remove drill bits without having to lower or move the table. This is very important.

3. Use a 1"-1 1/4" endmill or forstner bit with the center point ground off to square the face of the stem. Remove just enough material to face the rod stock. Remove the endmill and insert a 1/16" drill bit (or smaller if you can put hands on it). Drill into the rod stock about 1". Do this in several passes or the expansion of the compressed dust will enlarge the hole and burn its interior.

4. Remove the rod stock and flip it around in the vise. Repeat the squaring process with the end mill. Using a 5/16" drill bit, bore a mortise hole into the rod stock approximately 5/16"-3/8" deep. Be certain to do this in one single pass and preferably at about 1000-1200 rpm's.

5. Take a 1/8" drill bit approximately 8" long. A standard length bit typically won't be long enough for some of the stems you'll want to make. Take this bit and, using a standard bench grinder, grind each flute to a taper so that the bit tapers almost to a point. This will alleviate there being a "shoulder" where the 1/8" bit meets the 1/18" hole.

6. Using masking tape, mark your drill bit approximately 3/4" shorter than the total length of the stem. Using multiple passes, and frequently clearing the bore hole, drill your 1/8" hole, making sure it goes deep enough to intersect your 1/16" hole.

7. Cut a piece of 5/16" delrin about 1 1/4" long. Drill a 5/32" hole through the piece of delrin. If you have no way of drilling other than using your drill press, you'll want to prepare the piece of delrin *before* drilling your rod stock. After drilling the hole in your delrin, you'll want to chuck it GENTLY in your drill press chuck, and spin it at about 1000 rpm's. Using a file, square the end of the delrin and then put a chamfer on the end roughly equivalent to the angle of your drill bit tip. This is roughly 15 degrees. Using about a 16 TPI (teeth per inch) metal blade for a jigsaw, sawzall, or even a hacksaw, cut three to four grooves in the delrin about 1/8" apart. Turn the delrin around in the drill press chuck, and repeat the squaring/chamfering process. DO NOT cut grooves in this end of the tenon. Once the tenon is squared, remove it and set it aside.

8. Taking the same 16 TPI saw blade (you may need to grind it to a narrower profile) scrape some grooves in the 5/16" mortise that you drilled in the rod stock. At this point, you're ready to join the tenon and the rod stock.

9. Mix some clear 5-minute fast drying epoxy, and apply a generous amount to the grooved section of the tenon. DO NOT apply the epoxy to the mortise of the rod stock. If you do, the tenon will simply act as a plunger, pushing epoxy all the way through the 1/8" draft hole toward the bit end of the stem. When you insert the tenon into the rod stock, it should actually require the force of a small hammer or mallet to seat the tenon all the way in the mortise. You should get squeeze out on the face of the stem at this point. DO NOT TOUCH IT OR TRY TO CLEAN IT OFF.

10. At this point you need to go back to the mixing palate you used for your epoxy and basically poke at it for the next several minutes until it reaches a certain curing point. Once it turns glossy and will no longer pull a thread when the mixing tool is pushed into it (a bamboo skewer works well if you don't want to make a permanent tool), you've reached the beginning of your "magic minute." During the magic minute, you can take your mixing tool and pull up the edge of your ring of epoxy "squeeze out." It will come up cleanly, and you can simply peel it off the face of the stem. If necessary, just use the bamboo skewer to scrape away any small slivers of epoxy that hang on at the joint of tenon and stem face. Some denatured alcohol on a shop towel will remove any residue left by the epoxy.

11. At this point, insert a 5/32" tapered drill bit into your drill press and drill the draft hole out stopping about 1 1/2"-2" from the bit end. At this point, you can remove your rod stock from the vise.

12. Now you must cut the inlet or slot in the bit end of the stem. Using a small 3/8" round saw blade for your Dremel tool, cut a shallow slot in the bit end of the stem with the 1/16" hole right in its lateral center. This can be done on a drill press using the Dremel blade if you don't have a Dremel tool.

13. Now chuck the 1/16" drill bit in your drill press or Dremel tool. If you have a Dremel with an extension arm and pen grip, chuck the pen grip in your vise, and chuck the 1/16" bit into the Dremel. NOTE: If you do have the extension, you'll also need the "quick change" chuck otherwise you won't be able to tighten the chuck enough to squeeze the 1/16" bit. If you're using your drill press, you will want to run it at its very highest speed. With the 1/16" bit in the chuck turn the machine on and drill back into the same 1/16" hole that is already in the bit end of the stem. Tilt the stem toward you so that the bit cuts laterally. Slowly pull the stem downward as you apply lateral pressure. Doo this several times until you reach the outer edge of your slit. Turn the stem around and repeat on the other side. At this point, you will have a thin smooth tapered slit that will allow you to file the bit to a very thin comfortable profile.

14. Now it's just time to clean up the inlet with needle files and sandpaper. For the remainder of the process, you're on your own. There are lots of ways to shape the stem, but ultimately you will end up using files and sandpaper to achieve the final profile.

Good luck!

Todd


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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 12:47 pm 
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I'm not sure why you'd want a 1/8" bit at that point. I guess it doesn't matter because you're still finishing the airway with a 5/32" bit. The reason for drilling delrin separately is that it tends to flex the further it is from the clamping area. Having a hole started helps it stay centered, I think. Todd's method seems overly complicated to me, but I guess it would do the job.

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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 1:24 pm 
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Quite a few of the cherished old English have 1/8 airways. And many highly regarded danish makers too. For airflow, if the slot is opened properly to the airway, 1/8 is plenty for good airflow. 5/32 is almost overkill when the slot is opened all the way to the airway properly, but most are not so there is a pinching effect.

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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 1:42 pm 
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Premal,

So you could use a 1/8" bit for the entire draught hole, even in the shank? Then just make sure the slot is opened up as wide as possible?


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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 3:10 pm 
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pmbattles wrote:
Premal,

So you could use a 1/8" bit for the entire draught hole, even in the shank? Then just make sure the slot is opened up as wide as possible?


You could and the pipe would smoke fine for most people. In my opinion it's good to have a larger hole in the briar to account for swelling and residue buildup. Where the slot meets the airway is where it is important to be opened up wide enough. The width of the slot at the opening does not matter except that it is stronger the more narrow it is and only has to accommodate the volume of the airway. I've found. Experiment with different sizes and smoke them to see the differences.

A properly opened 9/64 airway in the stem will have better airflow than an improperly opened 5/32 airway in the stem. I have seen this in more than half of the 5/32 airway pipes that have gone through my hands over the years.

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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 3:21 pm 
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PremalChheda wrote:

You could and the pipe would smoke fine for most people. In my opinion it's good to have a larger hole in the briar to account for swelling and residue buildup.


This my thinking too. I use 4mm in the shank and 3mm in the stem.

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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 3:30 pm 
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I use 5/32 in the airway all the way through and like how the pipes smoke for me. I've gotten good feedback from my customers on my pipes and their open draw. Not saying it's wrong to do it different, probably just a preference thing. My advise is to test it first for yourself and whatever you decide on, stick with it so your customers get the same smoking experience no matter which pipe they buy from you.

As Premal said, the slot being properly opened probably makes the biggest difference. You don't want the air to pinch at the end of the airway. That tends to cause condensation to accumulate and restrict the draw.

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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 3:48 pm 
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Image


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Premal Chheda
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Before the battle begins in a game of chess.
"I am going to defeat you with my left hand!" - Arvind Shamji Chheda
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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 3:53 pm 
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Grind a used up airway drill flat so it will fit freely in the slot and test your opening.

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 Post subject: Re: Stem air hole size
PostPosted: Thu Jul 20, 2017 4:40 pm 
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Awesome! Thank you all for your comments, suggestions, and clarification.


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