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PostPosted: Sat Dec 10, 2016 7:30 pm 
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I recently experienced an issue with stem fit on a pipe I keyhole drilled. The stem fits flush, but due to the keyhole, it rocks in the mortise, causing the stem fit to have a gap. Has anyone else had this issue? Is this caused by me counter sinking the mortise, or possibly because the mortise hole isn't deep enough? Any help from prior experiences would be greatly appreciated.

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PostPosted: Sat Dec 10, 2016 8:54 pm 
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Pics?

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PostPosted: Sat Dec 10, 2016 10:52 pm 
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Is the tenon fairly short? Cut or delrin?

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PostPosted: Sat Dec 10, 2016 10:53 pm 
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Another possibility is the mortise is a little wider near the end of the shank, a little runout from the drilling as it got seated....

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PostPosted: Sat Dec 10, 2016 11:48 pm 
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I've had this issue before. I think it may have been from wobble on the lathe while drilling the mortise. You can fix it with a chucking reamer and make the mortise slightly larger. Of course, you'll need to redo the stem or tenon, but it should resolve the mortise issue. Now, when I drill first, I usually ream the mortise both for the sake of getting it centered better and for the sake of a smoother mortise. A drill bit only cuts at the tip. A chucking reamer cuts on the sides.

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PostPosted: Sun Dec 11, 2016 12:56 pm 
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Here are some photos of the issue. I wasn't sure if I counter sunk the mortise too much, like Sas said, making the mortise wider at the end, or because the tenon is short. Or like Jeremiah stated, caused by the drilling on the lathe.

Jeremiah, do you drill the entire mortise with a chucking reamer, or just get it started with one?

Also, is there a specific order that you guys use to drill your keyhole drilled pipes? I did the air hole first, then went back and did the mortise, and then faced it with a forstner bit, and then used the counter sink. If there is a better order as to how to go about it next time, I would greatly appreciate any and all advice.


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PostPosted: Sun Dec 11, 2016 3:17 pm 
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I don't think the keyhole is causing your problem, but it's hard to tell.

Like Jeremiah said, chucking reamers can be used with great effect to open up the mortise to a consistent diameter. The problem here could be a number of things. I usually face before I do anything else, then drill the mortise with an undersized bit, ream to just under my desired diameter, and then drill the draft hole. If I need to keyhole something I start with a very short bit for stability or in severe cases start the keyhole with a round file. Delrin tenons can also flex or not be seated correctly in the stem stock. You may need to ream the mortise to a consistent size, and chuck up the pipe on a pin gauge and reface the shank end with a ground tool (on a metal lathe) or a chisel on a wood lathe. Make sure your tools are sharp! Then you would have to cut a new tenon, but that should fix the issue.

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PostPosted: Sun Dec 11, 2016 9:18 pm 
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I don't drill with the chucking reamer. I face the shank, start the hole with a hole starter, drill the mortise, then chucking reamer. Then I use a hand tool (instead of a countersink) and then the airway. And if I need to keyhole, I use a dremel/foredom to extend the airway to the bottom center of the mortise. I'll also sometimes use a needle file if I need to.

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PostPosted: Sun Dec 11, 2016 9:32 pm 
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I've been following this, and can't see how it is possible to drill a non-cylindrical hole (on any axis---keyhole, funnel, or jug) unless something is either loose or not aligned on the lathe. The procedure/process/technique (except for center spotting) shouldn't matter.

PS --- The tenon in the pic is too short

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PostPosted: Mon Dec 12, 2016 12:19 am 
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Based on the pics there is essentially zero chance the keyhole is causing your issue. It's either a funky drilling of the mortise, or a bad delrin joint.

P.S. The tenon length is fine.

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PostPosted: Mon Dec 12, 2016 1:32 am 
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P.P.S. Tyler likes tenons that are too short.

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PostPosted: Mon Dec 12, 2016 10:06 am 
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So from your collective advice and from tinkering with things last night, we have determined that the issue is with the mortise. I believe that for some reason the 5/16 bit didn't seat well in the wood when it began cutting, and made the mortise hole slightly larger than the normal 5/16. I don't know if it is because i drilled the air hole first, and then the mortise on this one, or if it was caused by the speed at which I drilled.

Could this be caused by the speed at which the mortise hole is drilled? I was under the impression that this was to be done in one pass, and to be done quickly, as to not expand the hole. I believe I may have drilled this one at relatively slow speed, below 500rpm. Could you guys shed some light on what speed would be appropriate?

Also, I haven't purchased hole starters yet, so I'm sure that might help the issue. Ill also look into the chucking reamers. Any particular set of chucking reamers you would suggest?

I was able to re do the stem last night, and used a 3/8 delrin tenon, and turned it down to fit the oversized mortise, which seems to have fixed the issue with this pipe.

Thanks for the advice.

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PostPosted: Mon Dec 12, 2016 10:19 am 
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Are you using a stub/machine length bit for drilling? If not, get one. Also speed is not really the issue, slow and steady will do a good job just clear the chips often.

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PostPosted: Mon Dec 12, 2016 10:27 am 
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If your lathe is even the slightest bit off center and you aren't paying attention when you start the hole it is really easy to have the bit not catch center and you end up with an oddly shaped mortise. It's actually really easy to see as the bit will be dancing in a circle as you make the cut. Ask George....he has fixed a few for me over the years by reaming them (Why should I buy reamers when he has 8,000! :lol: ) On the next mortise you drill make double sure that your bit is going to catch center when you start drilling. Start your feed slowly and make sure that the bit stays on center until it is deep enough that the briar supports the drill the rest of the way. Hopefully that will help a bit with the mortise being bigger than you intended.

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PostPosted: Mon Dec 12, 2016 11:08 am 
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I am using a stub 5/16 bit that I got from Steve Norse. It may be time for me to purchase a new one.
Should I be peck drilling a mortise hole? Or just drilling slow enough for the bit to clear the chips on its own? Im afraid that if i peck drill with my wood lathe, that I could end up causing the mortise to expand because of that as well.

scotties22 wrote:
If your lathe is even the slightest bit off center and you aren't paying attention when you start the hole it is really easy to have the bit not catch center and you end up with an oddly shaped mortise. It's actually really easy to see as the bit will be dancing in a circle as you make the cut. Ask George....he has fixed a few for me over the years by reaming them (Why should I buy reamers when he has 8,000! :lol: ) On the next mortise you drill make double sure that your bit is going to catch center when you start drilling. Start your feed slowly and make sure that the bit stays on center until it is deep enough that the briar supports the drill the rest of the way. Hopefully that will help a bit with the mortise being bigger than you intended.


Scottie, that makes perfect sense. I'll do some practice drilling when I get home this evening to check my lathe. It very well could be that my lathe is slightly off. I am using a wood lathe for all of my drilling and shaping. Ill give it a good cleaning again, make sure that my drill chuck is free of all dust and debris, and try it all again to see how it drills.

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PostPosted: Mon Dec 12, 2016 11:22 am 
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I still use a wood lathe. It's just something I am in the habit of doing...starting slow and making sure that the bit is on center. Makes a world of difference. Also look at getting a brad point bit for drilling the mortise and airway. I got mine from Woodcraft and they are awesome.

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PostPosted: Mon Dec 12, 2016 11:42 am 
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For chucking reamers, I just bought individual ones off eBay in 1/16" increments between 1/4" and 3/8" to cover my bases.

Some other little tips on drilling.
1. Face the end of the shank with either a hand tool or (if you're using a metal lathe) the lathe tool. Facing with a forstner bit means you're covering a lot of surface area at the same time, which tends to cause vibrations. If you have a perfectly flat face, you'll have a much easier time getting the drill bit to center.
2. If you can't use a hole starter for the mortise, use the corner of a scraper on the wood lathe (or the appropriate metal lathe tool) to make a slight indentation at the very center of the shank face. This will help you get the drill bit to center.
3. Drill speed matters only in relation to how fast you're feeding. If you're spinning the shank at low speed, feed the drill bit at the appropriately low speed. I usually do just about everything between 1100 and 1800 RPM on my wood lathe. If you don't clear the chips, you'll get a lot of friction and burning and the bit may start to wander. I find that I can drill the mortise of most of my pipes in 1-2 passes while I need to clear the chips for the airway about every 1/4" to 1/2".
4. You can use a brad point bit for drilling the mortise and it will help with staying centered, as long as you get the very tip in the very center of the shank. The one downside of a typical brad point is that it leaves a dome at the bottom of your mortise. You can start the hole with a brad point bit and then use a split point bit to get the bottom closer to flat.
5. Start with the largest hole first. This means if you're using a countersink, start with the countersink, then the mortise, then the airway. Remember it's the tip of the tool that keeps it centered. If you countersink after your mortise is drilled, the tool is unsupported in the center. Same thing with the mortise and airway. If you drill the airway first, the split point of the drill bit doesn't have any contact in the center, so it may wobble. I think that's the story on your pipe this time.

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PostPosted: Mon Dec 12, 2016 12:58 pm 
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I always drill undersize and ream up. Providing the reamer is not dull, it will make the mortise diameter accurate and smooth. For .312, drill with a letter "N" bit (.302). For .375 drill with a letter "U" bit (.368). If you are making stems with integral tenons one reamer for each tenon size is all you need as you will be cutting the tenon to fit the reamed mortise. Delrin is another story. Delrin rods are extruded but will vary in diameter (not much but enough to give you trouble in creating a proper mortise/tenon fit) from batch to batch, manufacturer to manufacturer and over the length of the rod regardless of maker or batch. Here you want to accurately measure the diameter of the piece of rod at hand then ream the mortise to accommodate the fit you are looking for. This will require at least a couple of reamer sizes over and under nominal to cover your arse.
Reamers cut mainly at the tip and the flutes help make the hole smooth. The tips are ground at a 45 degree angle and this is what you will be left with at the bottom of the mortise. Cut the end of the tenon slightly to accommodate this chamfer.
A chamfer in the end of the shank at the mouth of the mortise is not necessary if there is no corresponding fillet at the base of the tenon where it intersects with the face of the stem. A fillet of some sort is normally left at the base of an integral tenon for added strength and thus requires a clearance chamfer at the mortise opening (only big enough to clear the fillet). I thread all of my Delrin tenons and as such have no fillet at all at their base. For a .312 size I will cut a 1/4-20 thread which will leave a square shoulder that comes to rest on the stem face. I bugger the internal and external threads so that the glue has somewhere to go and create a mechanical lock. Without this step you can unscrew the tenon fairly easily due to the lack of glue adhesion to the Delrin.
Extremely sharp bits/tools and rigidity are paramount. The typical Chi-com wood lathe is pretty sloppy inre the fit of the tailstock to lathe bed and in the fit of the quill in the tailstock. Both of these issues have a profound effect on drilling accuracy and are probably at the root of your problem. Center drills and short bits are a must. I would peck drill the undersize hole and ream to size in one quick pass. You want to clear the initial chip build up to prevent the drill flutes from packing and thus getting hot. The reamer is only taking out a few thou so heat is not an issue. I usually don't even crank the reamer in and out, I just slide the tailstock (carefully so as not to hammer the bottom of the mortise). On a straight drill I will usually square the end of the shank and drill the mortise then drill/ream the airway then finally ream the mortise. The drill point at the bottom of the mortise automatically makes a start point for the airway drill. Yes, I ream the airway too, to make it smooth. Everyone obviously has their own way of doing things. All of this works for me.
Hope this helps and good luck!


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PostPosted: Mon Dec 12, 2016 3:47 pm 
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When you buy your stub length drill shell out for a solid carbide, it will probably cost about 2-3 what a decent HSS bit will but if you take care of it then it is likely you will never buy another again.

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PostPosted: Mon Dec 12, 2016 4:08 pm 
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Thank you all for your advice and hints as to what my issue could be. I greatly appreciate your willingness to help with this issue, and all other issues I have had in the past.

I will be taking all of this into consideration, as I go forward to purchase some much needed tooling, as well as implement your suggestions in practice. Ill be sure to let you all know how it turns out once I get a chance to put the new tools to work.

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