Bottle Stopper Problem

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JCochrun

JCochrun

Member
Joined
Sep 13, 2010
Messages
230
Location
Penn Valley, CA
I'm running into a slight problem. I've drilled two blanks and tapped them. The problem arises when I thread it onto the mandrel. There is a gap on one side between the mandrel and blank. After looking at it some more, it looks like the hole is at an angle. Any ideas?

Thanks,

Jim

Penn Valley, CA
 
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I use a forstener but the size of the stopper to drill a hole about 1/8" deep so the stopper sits down into the blank a little. That gives a better blank to stopper transition & helps to hide those little imperfections. It's difficult to get the tapped hole perfectly square to the blank - with this little trick you don't have to worry about it so much.
 
If that happens to me, I will take a thin parting tool and cut between the blank and the mandrel while turning it on the lathe. Be careful when doing this because you can get a catch. Also, I try not to get all the way down to the threads on the mandrel and then I will remove the stopper from the mandrel and flatten it the rest of the way on my disk sander. Remount the stopper and finish turning....
 
All of the above - - -

I mount the blank between centers and turn a small mounting tenon on one end. Mount it in a scroll chuck and face off the other end (which will become the bottom). I used to use a forstner bit to turn a mortise in the bottom, but more recently I've just been turning a recess. I drill the hole with the blank still on the lathe, and then thread the hole using the tailstock to keep the tap centered. I always reinforce the threads by saturating them in thin CA, and also smear some CA on the bottom to finish and waterproof the recess at the same time since I won't have simple access to the bottom when the blank is reversed for turning.

Usually (but not always) that results in a threaded hole that is perpendicular to the place of the bottom of the blank when I thread it on the mandrel. But I still sometimes have to trim just a bit off the bottom with a thin parting tool.
 
JCochrun said:
Thanks all. I never thought about putting the tap in my drill chuck. I'm guessing that you have the lathe set to slowest speed for that?
Click to expand...

Frankly, I wouldn't attempt to power-thread a blank. Threading is really a very simple task, so I always do it by hand.

You certainly can mount the tap in a Jacobs chuck in your tailstock, and that might be a smart thing to do if your tap doesn't have a centering dimple. But if it does have a dimple, then you can you a cone-type live center to keep that dimple centered as you advance the tap into the wood.
 
If I don't drill a recess with a forstner bit, the other thing a local turner showed me awhile back is to put a couple of washers (smaller OD than the flat on the stopper itself.)

Then you can turn a chamfer down to the washers, which effectively "hides" a bit of non-orthagonality. This works pretty well.

-gary
 
I've got the tap set from PSI. The tap fits into the rachet head. If I put the tap into the drill chuck, how do you turn it by hand? Sorry if I'm making this more complicated than it needs to be. I put the blank between centers and turned a tenon on one end. Mounted it in a chuck and squared the other end, then drilled my hole. Now I am ready to tap it but the tap and rachet are a little loose where they meet. There is a little (very little) wobble in them when placed together.

If the hole is straight, the tap will just follow the hole, right? It won't change the angle of the hole, will it?

Jim
 
JCochrun said:
If the hole is straight, the tap will just follow the hole, right? It won't change the angle of the hole, will it?
Click to expand...

Unfortunately, the tap won't necessarily follow the hole. That's why higher-quality taps have a centering dimple in the end that you can use to center it on axis. With the blank in your chuck, you can either bring the cone center in your tail stock up to that dimple, or you can mount a centering device (which can be as simple as the end of a nail) in your Jacobs chuck in your tailstock, or you can actually chuck the tap into the Jacobs chuck. But the idea is that you use your tailstock to keep the tap on axis as you thread the hole.

I'm not familiar with the PSI ratchet driver. But you can use an ordinary tap holder to drive the tap, or I typically just use a crescent wrench to advance the tap into the blank while turning the scroll-chuck-mounted blank by hand and periodically advancing the tailstock ram to keep the centering device in the dimple. I know - that sounds like you need three hands, but its really not all that complicated. You are typically tapping a 3/8x16 thread, perhaps only 3/4" deep, which means only 12 threads.
 
JCochrun said:
I've got the tap set from PSI. The tap fits into the rachet head. If I put the tap into the drill chuck, how do you turn it by hand? Sorry if I'm making this more complicated than it needs to be. I put the blank between centers and turned a tenon on one end. Mounted it in a chuck and squared the other end, then drilled my hole. Now I am ready to tap it but the tap and rachet are a little loose where they meet. There is a little (very little) wobble in them when placed together.

If the hole is straight, the tap will just follow the hole, right? It won't change the angle of the hole, will it?

Jim
Click to expand...
Edit: re-read your post, you do have a Jacobs style chuck, the "drill chuck", substitute the words "drill chuck" for "Jacobs style chuck" below.

From "tap it" above install your tap into a Jacobs style chuck in the tail stock. Move the tail stock and tap up to the part. Apply a little pressure to the tail stock(no need to lock it or turn the tail stock handle), just press it against the part and hole lightly. Grasp the Scroll chuck on the headstock and start turning the top of it toward you ,DO NOT POWER UP THE LATHE, and continue with pressure on the tail stock. The tap should tap its self into the hole. Continue until the tap bottoms out then reverse the pressure on the tail stock and the direction of the scroll chuck. You should now have a nice "straight" tapped hole in your blank.

Also get yourself one of these SPRING-LOADED TAP GUIDES. They can provide a 3rd hand in a lot of taping situations.
 
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I drill a 3/4" hole in the blank 3/4" deep (on the lathe). I epoxy a 3/4 x 3/4 plug into this hole and let the epoxy 'set up' I then drill my hole, tap it out twice, the first time with the regular tap from PSI and a second tap with a 'bottoming' tap. I then use a diamond point carbide cutter to give a slight convex cut into the hole I've created. This has eliminated any gap between the blank and the hardware.
 
So I am doing this a little bit differently than I have before. I took Louie's approach. I mounted between centers, turned a tenon, mounted in chuck, squared the end, and then drilled. I tapped the hole like I had been doing. When I put the blank on the bottle stopper mandrel, there were no gaps. I'm thinking that it wasn't the drilling/tapping but maybe it was that my blanks weren't as squared up as I thought.

Thank you all for the ideas and suggestions. I really appreciate it.

Jim
 
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