EXPERIMENT

[Drcal]

I have started a few threads in the past in which I asked for help with bottle stoppers--- no matter what size I drill the hole if I tap it or not, 50% of my blanks spin on the screw mandrel (I use the AS MT2 mandrel). Some spin before I start turning, while I am screwing them on the mandrel, other spin half way into the turning. I always use the tlstock--still spin, etc.

Today I got the idea of inserting into the blank a 3/8-16 threaded insert. I got one at the hardware store and I was feeling real good about it; I knew it would work. Well, don't know if it will work because I could not screw the insert into the blank. Trying to get it into end grain was impossible. It has a slot that spans the whole piece for a screwdriver (see below). It is a rather big outside diameter and therefore a big slotted screwdriver is even too small. I never got it recessed into the blank. I am not the strongest woman! I even tried on the lathe and no luck.

It I could only get the insert recessed , I think it would work. Am I crazy? Any ideas?

Carmen

 

[LEAP]

Carmen,
Get a bolt with a hex head that matches the inside thread of the insert. Get a nut that fits the bolt. Screw the nut onto the bolt. Then screw the insert onto the bolt so that it the bolt almost but not quite protrudes from the insert. Now screw the nut down the bolt until it hits the top of the insert and tighten them together. This will jam the nut and insert together they will not be able to turn on the bolt. Now you can use a wrench to turn the whole thing into your wood. When you want to remove the bolt first loosen the nut away from the insert then the bolt will come out easily. Feel free to email me if you need a better explanation.

 

[Knight]

while it may be a 3/8-16 inside thread, it is larger on the outside and would need to
have the hole drilled with the proper tap drill for the outside diameter threads, whatever they may be.
And If you drill for those, would you be any better off than you are now in drilling for the 3/8 mandrel..
Forcing a too large thread into the wood may lead to other problems such as splitting or cracking.
Just a thought.

 

[monophoto]

I don't know that a threaded insert is the answer. Threaded inserts are primarily intended for applications where the need is for a set of threads that will be used repeatedly. In the case of bottle stoppers, the threads will be used twice - first to mount the blank on the spindle, and secondly (and finally) to install the stopper hardware. So the problem is getting an initial set of threads, not having those threads last for multiple uses.

But I am familiar with the problem of threading stopper blanks. In my experience, about 75% of the blanks spin on the mandrel (generally because the process of threading the hole in the blank actually enlarges the hole rather than threading it), and in about 75% of the cases, the hole is not exactly on axis so the blank doesn't seat squarely on the mandrel (and later, on the stopper hardware). And yes, the numbers add up to a pretty dismal assessment of my skills!

What I have learned through painful experience (and failure) is:

1. It is important that the bottom and top of the blank be absolutely parallel. You can't be assured that wood that is sold as 'stopper blanks' will be accurately cut with parallel faces. The way to solve this problem is to square the blank yourself.

2. Hard woods are hard to thread. I know that sounds wrong - metal is theoretically quite easy to thread, so why not hard wood? But what I've seen happening is that the tap simply spins on the hole, enlarging the hole rather than cutting threads. For a tap to work, the first threads that are cut must resist the axial force on the tap as it cuts deeper into the hole. As the tap penetrates deeper into the hole, there should be more threads to resist that axial force. But with hard wood, the initial threads aren't strong enough. In theory, drilling the hole smaller should mean that the threads are deeper [and stronger], but if that often means that the tap can't start cutting at all. Softer wood seems to thread better than harder wood.

3. Sometimes, drilling tan oversized hole and glueing in a dowel makes it easier to redrill and thread the hole. That way, you can control the choice of wood (the dowel) that must be threaded.

4. Watch out for dull taps . Yes - taps do become dull with use.

 

[randyrls]

Trying to get it into end grain was impossible. It has a slot that spans the whole piece for a screwdriver (see below). It is a rather big outside diameter and therefore a big slotted screwdriver is even too small. I never got it recessed into the blank. I am not the strongest woman! I even tried on the lathe and no luck.

It I could only get the insert recessed , I think it would work. Am I crazy? Any ideas?

Carmen; I am assuming that the insert is threaded on the inside. Some inserts have a hex shaped recess on the inside.

In either case, take a bolt with the same thread as the insert. Put two nuts on the bolt to act as a stop. Twist the nuts so they jam together. Now thread the insert onto the end of the bolt. Use the head of the bolt to turn the insert into the stopper. If you use a bolt that is only partly threaded, you can cut off the bolt head and put the bolt into a drill / driver and drive the insert into the wood at slow speed and high torque. Loosen the two nuts and remove the bolt.


Aside: The correct hole for the AS stopper mandrels is 5/16". You should use a tap to thread the hole, and you may need two taps. Taps can be had in a set of three.
Taper tap has a long tapered start to the threads.
Plug tap has a shorter and steeper taper to the threads.
Bottom tap has a a very short tapered section.
Like this:
http://cgi.ebay.com/3-8x-16-UNC-Tap...426?pt=LH_DefaultDomain_0&hash=item19bb7b4cfa

 

[rjwolfe3]

I have the same problem so I may try this myself! Thanks for the good idea.

 

[tommyd]

they also have threaded inserts that you just pound into the hole they have little nipples on the sided that dig in to the wood. but with these you still need to use ca on them.

 

[tommyd]

here is a ulr for the inserts i'm talking abouthttp://www.hweckhardt.com/threadedins/Yardley/StandardizedMolded_typeA.htm
hope this helps

 

[rjwolfe3]

http://www.hweckhardt.com/threadedins/Yardley/StandardizedMolded_typeA.htm

thought I would make it clickable for ya

 

[aggromere]

Carmen, I live in Carrollwood in Tampa. I have only made a few bottle stoppers but didn't have any problems and I use the mandrel, tap and drillbit from AS. If you would like to come over one Sat or Sun and bring a couple blanks and your kits I will see if i can help you. You can PM me if you want.

 

[tommyd]

http://www.hweckhardt.com/threadedins/Yardley/StandardizedMolded_typeA.htm

thought I would make it clickable for ya

thanks how do you do that?

 

[rjwolfe3]

Copy the link from your thread, hit the icon above that looks like a blue globe and a chain and pasted it there.

http://www.hweckhardt.com/threadedins/Yardley/StandardizedMolded_typeA.htm

thought I would make it clickable for ya

thanks how do you do that?

 

[maxwell_smart007]

When I first started with bottle stoppers, I'd have a lot that spun - usually after I rounded them out with a heavy hand...

The solution for me was to gather up a bunch of the dust and small shavings that resulted from the round-out, cram 'em in the hole, saturate the heck out of them with thin CA...then in a day or so when it was cured completely, I'd redrill and return. The CA seemed to make it harder than the rest of the wood, so it would hold up to the rest of the turning.

 

[juteck]

I mount the stopper blank in a 4 jaw chuck with grain running parallel to the lathe bed, so the face of the blank is end grain. True the face grain end of the blank on the lathe with scraper, then put a small dimple in the center of the blank. Still mounted on the lathe, drill a 5/6" pilot hole to the depth of the threaded post on the stopper plus a little. Saturate the hole with CA and let cure or use accelerator. Re-drill with 5/16" drill to clean out the hole. The 3/8-16 tap I have has a little dimple in the back center - I use my live center in my tailstock inserted into the dimple to keep it aligned and a wrench to hold it, then hand turn the lathe while advancing the tailstock to tap the threads into the wood - I make a couple of turns, then back it out a turn -- repeat until to right depth. I haven't had a problem with this method, but you still need to take light cuts with sharp tools. You could always saturate the tapped hole with CA, let cure, and re-tap, but I've found that stabilizing the drilled hole with CA before tapping gives me enough strength for the wood to hold the thread.

Good luck!

 

[Skye]

I've used those brass fittings to make beer tap handles. Worked well at holding the wood, but I'd really have to say there's something wrong with the way you're drilling or something.

Are you drilling on the lathe or a drill press? Is it possible you've got wobble in your drilling practice and it's reaming out the hole? (crap, just read John's post, kinda what he was getting at)

 

[monophoto]

When I was at the public library today, I checked out a copy of Mike Darlow's Woodturning Techniques. This book has an entire chapter on threading techniques and issues.

This statement caught my attention because it addresses the specific question being discussed here: "With all but the hardest woods, the wood thread shears with the grain when using a tap." He goes on to say that when threading a blank axially (ie, the hole to be threaded runs in the same direction as the grain) a "superior thread is produced by deforming the wood with a screw."

In other words, Darlow's recommendation is that instead of trying to cut threads using a tap, it is better to drive a threaded bolt into the wood to deform the wood into something approximating a thread.

He also notes that threading is much easier if the grain is radial - that is, the grain of the wood is perpendicular to the axis of the hole being threaded.

 

[Drcal]

I have gotten some great ideas. First of all, the instructions on inserting the threaded insert were new to me, even thought I painstakingly inserted some before in other non-turning projects. I have learned something new and useful.

Also, I was enlightened by many of the suggestions for going back to my tap and screw set up which I will also try. I am going to get this. I will not give up!!!

Thaks everybody.

Carmen

 

[nava1uni]

I have found that using a 5/16 drill bit has stopped any spinning. I also don't tap all the way to the bottom until I have finished turning. I use a bolt with a wedge files out of the end to tap. I learned this in a class and have many taps made this way. They work well in making handles and other turned items.

 

[jtdesigns]

You might try dripping water thin ca into the drilled hole prior to and after initial threading. Then run your tap through one more time to clean up threads.

 

[rtodasr]

make cork stoppers... cheaper and only a 3/8 hole and dowel

 

[65GTMustang]

I would recommend the same as aggromere...I have the AS tap and mandrel I have never had an issue with the blank. From Resins, TruStone, M3, soft domestic woods, hard exotics, loose or tight grain I have never had one issue….knock on "wood"…lol – really the tap and mandrel they have is great and does not cost too much. However I was starting to have one issue and after turning about 60 stoppers I found the fix...My mandrel would work it's self loose and want to come out of the head stock...Not exactly an ideal situation while turning anything! With the tail stock back and your speed up to about 3000 while you make the last few finishing cuts to the top of the stopper, If I did not see it or feel it happening you can in vision the type of bullet that can make. I figured out that I could hold everything in by using a threaded rod through the head stock opening into the mandrel. AS's mandrel has a threaded opening on the opposite inside of the mandrel mine takes a 1/4" rod - A couple of rubber and stainless steel washers / grommets along with a wing nut handle or something to glue on the other end of the rod to use as a handle. When putting the mandrel in I screw it in on the other end of the head stock, now it is nice and tight with no more slipping.
I may not have described it very well in words so if you want to PM I can take a couple of pictures when I get in the shop tomorrow and then email them to you in the afternoon when I finish turning.