Keyhole drilling causing bad stem fit

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LatakiaLover
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Re: Keyhole drilling causing bad stem fit

Post by LatakiaLover »

A final comment since this thread is winding down...

Highly Scientific Studies have shown that 100% of non-tool-using humans think drill bits are much stiffer than they actually are; and 99% of those who DO use tools think so too.

The damn things are practically buggy whips. They deflect EASILY when side loads are applied, and there are too many potential side loads in a briar block/mortise drilling situation on a lathe to list.

My point? Listen to Chris. (Yes, he's from the country which plagued the world with Smiths instruments for all those years, but even that lot produces an outlier every now and then.)

Get a stub length bit in each of your standard tenon sizes and give 'em a try (after starting with a spotting bit) before messing with anything else. It might be all you need.
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Rbraniganpipes
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Re: Keyhole drilling causing bad stem fit

Post by Rbraniganpipes »

So I have looked at drill bits, and reamers, as you have all suggested. I would like to focus on just working around the 5/16 size, as I will be using delrin for tenons, and not turning integral tenons, as I just have a wood lathe and the Pimo tenon tool, which isn't as accurate as a metal lathe.

I am looking into getting the carbide screw machine bit in size N (.302) and then sizing up as you guys have suggested. Does it matter what the degree angle is? 118, 135, or 145?
Then getting the reamers in and around 5/16 and the next size up, which i guess would be 8mm.

I found that this company offers multiple reamers in 5/16. I don't understand what they mean by dowel pin, as I have never worked with reamers before.

5/16 dowel pin (.3105)
5/16 undersize (.3115)
5/16 dowel pin (.3120)
5/16 oversize (.3135)

Can someone explain what is meant by dowel pin, and which of these 5/16 reamers I should purchase. Ill worry about working with other sizes of tenons and the tools required for that once I can accurately put into use the methods and tools we are discussing for the 5/16 delrin issue.
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Rbraniganpipes
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Re: Keyhole drilling causing bad stem fit

Post by Rbraniganpipes »

LatakiaLover wrote: Get a stub length bit in each of your standard tenon sizes and give 'em a try (after starting with a spotting bit) before messing with anything else. It might be all you need.
Hey Adam, I have been using a stub length bit in 5/16 since I began pipe making. It may be time for me to just get another stub length bit of the same size, as this one is two years old. Sometimes it works flawlessly, and other times, it drills larger diameter holes than it should.

I didn't know if it had something to do with the briar itself, lathe, tools, or human error. It could be all due to human error of not starting the holes correctly, or the order in which i drill the holes, as well as issues with lathe accuracy or bit accuracy.

While I do have a lot to experiment with here to try and get this issue corrected, I have found that when I use delrin tenons, it is never as tight of a stem fit as I would like, even when the 5/16 bit drills perfectly. I'm going to explore all possible options, as I can learn valuable lessons from all of them, and have gained a great deal of valuable information on how to fix these issues in a variety of ways.

I greatly appreciate your input, and will start out by trying just another 5/16 stub bit, as I ordered one earlier today, and will see where that gets me! If that doesn't work, I have lots of options to explore!
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Rbraniganpipes
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Re: Keyhole drilling causing bad stem fit

Post by Rbraniganpipes »

I just realized that I know what dowel pins are, and don't know why I didn't consider that these chucking reamers were used for other woodworking projects other than pipes. Thinking with a closed mind can be hard sometimes...
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Tyler
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Re: Keyhole drilling causing bad stem fit

Post by Tyler »

Before you buy anything, I recommend changing your procedure.

Go in this order:

Face with Forster
Drill mortise
Re-chuck for draft hole and drill airway. Make sure the keyhole is not deflecting the bit before drilling into the floor of the mortise.

This will help you, A LOT. If this change doesn't help, then consider your lathes alignment.

You shouldn't need all these reamers for a mortise and tenon to fit. The mortise might be NICER, but you don't NEED them.

Another lathe drilling tip, bring the tails stock with drill bit up to the spinning wood, and the bit will self-center. Once self-centered then lock the tail stock. Don't lock the tail stock before you drill. Wood lathes are sloppy. Right is in there somewhere, but it's flexible. Let it center then lock it.
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oklahoma red
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Re: Keyhole drilling causing bad stem fit

Post by oklahoma red »

Usually with Delrin I'm happy with the fit that comes from a mortise that is .0005-.0015 smaller than the tenon. Sometimes the hardness of the particular piece of briar will have an effect on the fit. Just to be on the safe side, after I drill the mortise under-size I start with the smallest reamer, check the fit and keep going up until I have what I want. Obviously you can always go up but good luck trying to put the briar back in the hole. If Delrin rods were always exactly the same diameter then life would be easy.
Tyler is absolutely correct in his statement about letting your cutting tool (drill bit or center drill or----) find its own center THEN lock down. Also, with most of the Chi-com wood lathes, keeping a little tension on the quill lock will help somewhat with the slop. Test: to get an idea of what you are working with, lock the tail stock to the bed then try wiggling the quill at multiple extension distances both with and without the lock engaged. Also be looking for lateral movement in the quill when the lock is applied. Because of piss-poor design and workmanship (or wear and tear) I've seen as much as .025 movement at the tip of a drill bit when locking the quill. So letting the lathe/bit find its own center before locking down anything is a must. These wood lathes were never intended to do some of the work that is demanded of them in pipe making.
Another problem that is common to old metal lathes (no matter the maker) is that over time the bed will wear to the point that the tail stock needs to be shimmed to compensate. I had to put .010 shim in my old 1943 Logan. This is often overlooked and will DEFINITELY screw up your drilling unless corrected.
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Re: Keyhole drilling causing bad stem fit

Post by CondorPipes »

scotties22 wrote: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.
Scottie nailed it with the brad point bit, made a big difference for me. I have botched a few mortis holes because I was working to fast or was distracted. When I pulled the bit out and saw the tip making a circle I new I was in trouble. One case I didn't seat the bit in the chuck straight and in another the bit was slightly bent...that what get for using a cheap bit. As a side note, that is a nice looking pipe.
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Tyler
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Re: Keyhole drilling causing bad stem fit

Post by Tyler »

A comment on using a brad-point bit for the mortise, a brad point won't self-center as easily. The sharp point just cuts right in, and won't slide to center. For that reason I don't like them as much for the short drilling of the mortise unless your lathe is spot on and it doesn't need to pull to center to drill accurately. For the air hole, I think they a very important.
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Re: Keyhole drilling causing bad stem fit

Post by scotties22 »

I face with a forstner bit. The hole the spur on the forstner leaves gives the brad point a spot to grab onto. As long as I take the time to make sure my forstner is running true I don't have any problems with the brad point for the mortise running true.

A brad point for the airway is the best thing since sliced bread.
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CondorPipes
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Re: Keyhole drilling causing bad stem fit

Post by CondorPipes »

Tyler wrote:A comment on using a brad-point bit for the mortise, a brad point won't self-center as easily. The sharp point just cuts right in, and won't slide to center. For that reason I don't like them as much for the short drilling of the mortise unless your lathe is spot on and it doesn't need to pull to center to drill accurately. For the air hole, I think they a very important.

I'm tracking with most of what your saying but I'm a little unclear on what you mean about letting the drill bit and/or lathe find its natural center or self-center, then locking down the tailstock. I am doing most of my drilling and shaping on a Grizzly wood lathe and liked the brad-point bits because they seemed to wander less then the standard bits I was using. Would you be so kind as to break down what you mean about the bit finding center. Thanks in advance!
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W.Pastuch
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Re: Keyhole drilling causing bad stem fit

Post by W.Pastuch »

There's 2 aspects to consider:
1.The center of a drill bit will align towards the center when touching the workpiece because it takes the least force to dig in in that spot (if it's not on center it will try act as a lathe cutting tool and the forces become much greater than with drilling). However, it is not self centering, it is simply flexing a little bit with each revolution as the tip tries to stay on center - on deeper holes it will have a negative influence on the precision and finish of the bore.
2. There is basically no rotational speed at the center of the workpiece, so the chisel edge of a standard drill needs to push away some material before it can really start to cut. That's why center drilling with very short and stiff drills is used to make it easier for the bit to catch and start cutting with the edges without dancing around trying to find the center point (a brad point kind of eliminates that problem).

Tailstock-headstock alignment is actually really important on a lathe, not only for drilling but also if you want to support your workpiece with a live center- if you're not aligned the workpiece will be out of round and/or tapered. I've gotten crazy over this on my metal lathe and had some success with the alignment, a wood lathe is probably much more vulnerable to this problem.
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Re: Keyhole drilling causing bad stem fit

Post by CondorPipes »

W.Pastuch thanks for the explanation that makes sense. I have had issues with the drill bit wandering a little at times when I'm starting the hole with a full size drill bit. I may have incorrectly assumed the bit had gotten dull and wasn't bitting into the wood causing it to wander off center. I have had better luck with a brad-point. I will have to try starting a pilot hole with a short/stiff bit perhaps slightly undersized then follow up the full sized bit to finish drilling the mortis and airway.
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Re: Keyhole drilling causing bad stem fit

Post by caskwith »

As I said before, stub length drill bits will solve your problems. Also a centre drill for starting holes. An accurate, well set up lathe helps too, so definitely check this before discounting other reasons for trouble.
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Re: Keyhole drilling causing bad stem fit

Post by CondorPipes »

Thanks for the info Chris I greatly appreciate it!
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Re: Keyhole drilling causing bad stem fit

Post by Rbraniganpipes »

Hey guys and gals!. Thanks again for all of the advice and tool suggestions. Here is a update on my trials thus far.

I drilled another keyhole pipe using a mixture of suggestions from you all, and wouldn't you know, it worked perfectly. Tightest delrin stem fit I have had thus far. You all were right, it had nothing to do with the keyhole, and everything to do with the mortise drilling off center. Here is what I did this time.

First, faced the shank of the pipe with a wood lathe tool to get it flush.
Next, I used a center drill bit to start a small hole in the center of my drilling surface.
Next, I used my screw machine stub 5/16 bit to drill the mortise, making sure to let the tool begin cutting before locking down the tailstock.
I drilled it at about 1000rpm, and made two passes, and easily cleared all the chips. The stem fit perfectly.
Next, I went on to the keyhole, starting the path with a small round file, and then using smaller bits to increasingly open up the path for my 5/32 airway bit. This seemed to work perfectly.

I haven't messed with brad points just yet, as they haven't arrived in the mail. I will try them out as well and see how they do, but overall, I am very pleased with the result.

Thank you all for your willingness to share ideas, experiences, and encouragement. I truly appreciate all of your help!

Cheers.
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