Bottlestopper Stripping Threads

[Anthony Welch]

I'm using a 3/8" threaded BS mandrel and 3/8" Bottom Tap form AS and using Ruth Niles SS threaded stopper. Out of the 15 or so stoppers I've turned since before x-mas only 4 of them I've been able to not strip the threads on the wood blank. These I've drilled out bigger and used the dowel/cork stoppers to keep them from being a total loss. I've seen the ways Ed Davidson has shown to mount the stoppers, this is the reason for I purchased the mandrel/tap.

Using what tools mentioned, what may be the steps that I should be performing that I'm not. Or, is there an instructional dvd that uses these tools. I've learned about pens this way, but don't want to purchase a dvd that doesn't use the tools mentioned.

I don't mind having threads strip, as I know this does happen. I'd rather have the failure ratio of the stripped threads be the other way or not at all. It gives me more of a market to sell cheaper stoppers. But I'd rather have my threaded blanks more predicable than they are.

Thanks!
Anthony Welch

[Jeffrey Fusaro]

anthony--

here's a few thoughts...

1 - don't thread the hole with the tap. just drill the hole and thread the wood on. i don't remember the root diameter for a 3/8"-16 thread, but something around 5/16" should do. just don't make the hole so small that you crack the wood when installing it on the mandrel.

2 - if you are using soft wood, the pre-threading with the bottoming tap will likely increase your failure rate.

3 - take small cuts when the blank isn't yet round. a good catch will be enough to tun the blank on the mandrel and strip the threads.

i made my own mandrel out of a 3/8"-16 bolt, nut and flat washer. i just cut the head off the bolt and i use my drill chuck to hold the bolt in the head stock. my home-made mandrels cost me $0.75 for three.

[Ed Davidson]

Anthony,

This subject/problem comes up fairly often. There are several potential causes that you should look into:
- The wood is soft...use a smaller drill bit, like a 11/32"
- Your drill bit is bent or not seated properly in the drill-chuck, causing run-out
- Your drill-chuck has rust or dirt on the MT, causing it to not seat properly...more run-out
- The stopper block is not being held securely while drilling, reaming out the drill hole and making it oversized
- When tapping the hole with your 3/8" x 16tpi tap, make sure you're not going in cock-eyed, thus making the hole oversized, or cross-threading the tap
- You might also check Ruth’s stainless stopper base to insure the threads are in fact 3/8” x 16tpi and that they are not damaged

Here is a link to an online video that shows this setup being used: http://content.penturners.org/video/3Dresin_3.wmv

[Frank Kobilsek]

Anthony

I alway use 5/16 bit, soft or hardwood to get the best threads.

For suspect or softer woods my trick is to drip thin CA into the drilled hole. Set the blank aside for a couple days to let the CA cure. This 'stabilizes' the wood around the hole to cut better threads.

Go easy tapping. Don't force the tap. Use fingers not your palm to twist the tap. I have a buddy that will stop by when I am turning and offer to help by tapping holes. He strips probably 10% but he is getting better. I might wreck 1 in 50 now. You'll get the hang of it.

Frank

[Ron Sardo]

Are you stripping the thread while tapping or when you place the turned blank onto the stopper?

I don't use a bottoming tap and I drill the hole a little deeper into the wood. This way the last couple of threads of the stopper bite into the wood better and the threads of the stopper doesn't bottom out in the hole.

If you are stripping the threads while tapping you just have to make sure you are feeding the tap into the wood at the proper rate.

[Anthony Welch]

What I've gotten down to so far is I'm drilling to 23/64's and tapping. Checking the fit w/the SS base. It is tight and I can't manually strip the threads. But, I have noticed w/the last 2 blanks when I had a catch, I backed the tail stock off and the blank would spin on the mandrel. This does happen more predictably w/softer woods than harder. Even had a Red Morrel blank spin on me and it turns like rock. Also I don't hog out my turnings, as I'm in no hurry to do these.

-Getting the hole cock-eyed does happen often. As I am manually tapping the hole, even when I think it isn't, it is. Can I just drill the hole and chuck the tap from the tail stock next time and this will fix this problem?

-Maybe making this a two step process, which I was hoping to avoid, make a mandrel out of bolts that Jeffery suggested only smaller than 3/8". Get the blank turned down, then drill to 23/64", tap, mount to the 3/8" mandrel and do the sanding and finish from there?

-If all else fails, could filling the hole w/epoxy and redoing the process. Would the epoxy hold?

-I'll also try a 5/16" hole. If this works for me, it'll keep it to 1 step turning and finishing.

[Ron Sardo]

I made my own mandrel and the bottom of the wood blank is right up against the mandrel.

If your tail stock is not perfectly align to your headstock your problem may be there.

I hold the tap in a tap handle, turn off the lathe and just before the spindle stops spinning I insert the tap. (I know someone is going to ream me out for this). Just about every time I need to move the spindle a turn or two to finish up the threads.

If you are getting catches all you need to do is practice a little more, I never get a catch

[Frank Chaffee]

….-I'll also try a 5/16" hole. If this works for me, it'll keep it to 1 step turning and finishing.

Anthony,
Use the 5/16” drill for your pilot hole before you seek another solution to your problem. The 3/8-16 tap you are using must have material to cut threads into, and a 23/64” drill leaves only a very few thousands of an inch on each side of a screw for thread engagement.

Next, and please know that I am not privy to the manufacturing schedule for Ruth Niles’ bottle stoppers, most RH taps require a frequent partial counter-clockwise turn several times in each inward cutting rotation to clear chips cut from the hole. While taps are available for continual machine rotation, it does not appear to me that you would be using those.

[Bobby Perry]

I also use a 5/16 drill bit and have had no thread problems

[Robert McGowen]

I have made quite a few of the Niles stoppers. I use a 21/64" drill bit on a drill press. Drill the hole about a 1/4" or so deeper than the top of the stopper is long. I just use an ordinary 3/8" tap bolt about 4" long that is mounted into the chuck. Hold the handle on the lathe and just screw the piece of wood onto the bolt until it bottoms out. I never use the tail stock, as the fit is quite tight, but I guess you could. Round the stock and then square up the bottom. (which is why the hole is an extra 1/4" deep to start with.) Turn the stopper to your design. You can now use the bolt as a handle when you finish the stopper or buff it. Unscrew the top and screw it onto the stopper threads. I only use a very, very small amount of epoxy as the threads make a tight fit and too much epoxy will make it difficult to screw all the way on. I have never had the threads strip or cracked the wood, even when using very dense woods.
Just my way to make them.....

[Gary DeWitt]

Yet another possibility:
Rough the blank round between centers, then drill and tap the blank and proceed using your screw mandrel. The blank won't be perfectly centered when you start your finish turning, but it will be a whole lot closer, so not as much stress on the threads from catches while roughing.
I suspect a combination of two or more of the above mentioned solutions may be needed, and you'll work out your own best way in time.

[Barbara Gill]

Anthony, go to Ruth's website. She has a Bottle Stopper Turning Process link. There are instructions for making a mandrel; it is very simple to make. Maybe that will help. If you need the address for her website, let me know by e-mail.

[Johnathan Bussom]

I guess I should be using 5/16 drill myself but have been using 21/64 which is really tight when threading on both the BS screw and on my scroll chuck screw!

Another thing I need to do with this tight fitting is rub the threads with a piece of used bar of soap and then like another mentioned go a couple threads then unthread then start again keeping it aligned.

I have not had any strip, but I think I will try the 5/16 since sometimes I hold my breath when taking a piece off though cause I didn't get enough soap on the threads.

John

[Robert McGowen]

Hi,

Maybe I am missing something, but it seems like using a 5/16 bit instead of a 21/64 bit would make things just that much harder, as the hole will be smaller to start with. The 21/64 that I use is very tight on dense woods and I would try a 11/32 bit before going down in size to 5/16. Like I said though, I might be missing something here.....

[Johnathan Bussom]

No Robert you not be missing a thing, maybe the old man's mind is really loosing it, Yep by golly 5/16 x 4 = 20/64 and as tight as my BS's have been I better try the 11/32 like you say!

Thanks for the electric, now the bulb is lit! At least I did say maybe!

John