heritagebob
Member
About to get into turning bottle stoppers, it seems the most common hole size is 7-32.. my question ( due to inexperience ) is what size tap do I thread the hole with to make sure the stopper threads fit securely ?
Threading A Hole Question
- Thread starter heritagebob
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monophoto
Member
You need to check the threading on the stopper components you have chosen to use.
AFAIK, there are two standards. The most common (in my experience) is 3/8"x16tpi. I have purchased stoppers with that threading from both PSI and Ruth Niles. But there is at least one supplier (Berea Hardwoods) that uses 1/4"x20tpi threading. Obviously, the mandrel you use should match the threading of the stopper base you will be using.
The hole that you drill must be smaller than the diameter of the threaded hole. I use a 5/16" drill when I need a 3/8"x16tpi threaded hole. For a 1/4"x20tpi hole, a #7 drill is normally chosen.
AFAIK, there are two standards. The most common (in my experience) is 3/8"x16tpi. I have purchased stoppers with that threading from both PSI and Ruth Niles. But there is at least one supplier (Berea Hardwoods) that uses 1/4"x20tpi threading. Obviously, the mandrel you use should match the threading of the stopper base you will be using.
The hole that you drill must be smaller than the diameter of the threaded hole. I use a 5/16" drill when I need a 3/8"x16tpi threaded hole. For a 1/4"x20tpi hole, a #7 drill is normally chosen.
lorbay
Member
All the ones I've done so far are 3/8". For most woods, I drill a 5/16" hole & use a 3/8" tap as recommended in the PSI link that Lin gave. For really soft wood though, I use a 9/32" drill.
I have threaded the blank directly onto the mandrel without using the tap a few times, but I get more consistent results when using the tap - YMMV.
I have threaded the blank directly onto the mandrel without using the tap a few times, but I get more consistent results when using the tap - YMMV.
monophoto
Member
I prefer to mount my stopper blanks in a chuck and face off the end that will be the bottom, leaving a slight depression. The objective is to have a very small recess in the bottom so that there is an edge that covers the join between the turning and the top of the stopper base. That way, if for any reason the base doesn't fit tightly against the bottom of the turning, the gap won't be visible when the finished stopper is viewed from the side.
Then, I drill and tap the hole while the blank is mounted in the chuck. End-grain threads are notoriously weak. My experience is that after tapping, it helps to squirt a little thin CA into the hole, let it cure, and then run the tap in again This strengthens the threads so that they can withstand the stress of mounting on the mandrel, and later screwing in the stopper base.
I also squirt a little CA on the bottom of the blank and wipe it around the recess to seal the wood. I finish my stoppers on the mandrel, so it's not possible to get to the bottom. So finishing the bottom at this point - after the hole has been drilled and tapped but before the stopper has been turned - makes it possible to seal the wood at the bottom. That way, after the stopper has been used, it can simply be rinsed off with a little water..
I also sand
Then, I drill and tap the hole while the blank is mounted in the chuck. End-grain threads are notoriously weak. My experience is that after tapping, it helps to squirt a little thin CA into the hole, let it cure, and then run the tap in again This strengthens the threads so that they can withstand the stress of mounting on the mandrel, and later screwing in the stopper base.
I also squirt a little CA on the bottom of the blank and wipe it around the recess to seal the wood. I finish my stoppers on the mandrel, so it's not possible to get to the bottom. So finishing the bottom at this point - after the hole has been drilled and tapped but before the stopper has been turned - makes it possible to seal the wood at the bottom. That way, after the stopper has been used, it can simply be rinsed off with a little water..
I also sand
heritagebob
Member
Tech support at Woodcraft suggested " no need to tap the pilot hole, simply thread onto the mandrel, turn to desired form, then epoxy onto the stopper " ??? Sounds very simple............
monophoto
Member
There are two variables involved here. One is the wood - its much harder to thread holes in hardwood than it is in softwood. The other is grain orientation - holes in face grain are easier to thread (and the threads are stronger) than holes in end grain.
Screwing a blank with an unthreaded hole directly onto a mandrel might be possible with balsa or pine, or if the hole is in face grain.
My experience is that its hard enough to thread a hole in end-grain hardwood using a sharp (new) machinist's tap. I can't imagine how difficult it would be to an unthreaded blank onto mandrel.
Hmmm - If the WC guy has to use epoxy on the finished stopper, I wonder if he might be drilling the hole a little larger than 5/16" to more easily thread it directly onto the mandrel.
I think I'll stick with my tap. I sometimes use a little CA to strengthen the threads in soft woods as Louie suggested, but I've never had to glue a stopper into the finished blank.
I drill my holes on a drill press & use a forstner bit to drill a slight recess similar to what Louie described before I drill the stopper hole.
randyrls
Member
To join the thread; There are several drill and tap charts on the internet. This one is one of the better ones. Has both Metric and Imperial threads.
monophoto
Member
There is also an iPhone/iPod app called iEngineer. The version for imperial measurements is free, but there is a small charge for the metric version.
alankulwicki7
Member
I use the Ruth Niles stoppers exclusively and use the mandrel I bought from her for threading blanks. Her mandrel has a groove in it for to make threading easier. Sometimes I have to use CA on soft or punky wood but usually I just mount the mandrel in my lathe and then 'thread' the blank on. On harder wood I will have to use the mandrel as a tap and go back and forth a few times. I even use the mandrel to thread resin blanks that I make myself.
I've made well over 100 stoppers this way without a problem....
I've made well over 100 stoppers this way without a problem....
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heritagebob
Member
boy I'm all kinds of confused now... maybe trial and error is in store for me
TellicoTurning
Member
I rarely use the SS stoppers any more... I make mine with the little silicon sleeves over the hardwood dowels.... I just drill a 3/8" hole and put that on a pin chuck held in a collet to do the turning... it's fast, less likely to ever hit the mandrel and booger a tool, rarely slips....