On Atlas Billiard Supplies I see 3/8 x 10 modified taps with .308 and .312 pilots. The 3/8 x 10 modified pins have exclusively a .308 minor. Understanding that the modified 3/8 x 10 pin's centering barrel is .381, which bore establishes pin alignment, which tap pilot is preferable? Thanks for your input!
3/8 x 10 modified pin tap with .308 vs ,312 pilot
- Thread starter shankster8
- Start date
I'm not really sure what you are asking.
The alignment barrel that you referenced being .381 is to align the pin in the butt when installing it.
The .308 is the minor diameter of the threaded portion of the modified pin. The tap for that pin has a register on the front so that the tap follows the bored hole nicely. So, the .308 minor diameter of the pin is involved with keeping the tap straight and helping to align the shaft to the pin when the shaft is screwed on.
The alignment barrel that you referenced being .381 is to align the pin in the butt when installing it.
The .308 is the minor diameter of the threaded portion of the modified pin. The tap for that pin has a register on the front so that the tap follows the bored hole nicely. So, the .308 minor diameter of the pin is involved with keeping the tap straight and helping to align the shaft to the pin when the shaft is screwed on.
Sorry if my question is not clear. The pin has threads on each end, and an alignment barrel in the middle. The end threads are .308 minor. Is it preferable to screw them into a hole tapped with .308 or .312 tap?
Ok. That helps.
The alignment barrel is there to align the pin. The threads behind the alignment barrel that go deep in the butt are there to secure the pin via a mechnical method in addition to the glue. There is no need to make those threads tight. In fact I believe those threads on the pin itself are slightly undersized to begin with. If your bore and threads deep in the butt are too snug they might want to fight against the alignment barrel doing it's job. Bore the hole to 5/16".
I live thread, so I can't say which tap I use down there because I don't use either, but I suspect with a 5/16" bore you can use either one for those threads without a problem.
The alignment barrel is there to align the pin. The threads behind the alignment barrel that go deep in the butt are there to secure the pin via a mechnical method in addition to the glue. There is no need to make those threads tight. In fact I believe those threads on the pin itself are slightly undersized to begin with. If your bore and threads deep in the butt are too snug they might want to fight against the alignment barrel doing it's job. Bore the hole to 5/16".
I live thread, so I can't say which tap I use down there because I don't use either, but I suspect with a 5/16" bore you can use either one for those threads without a problem.
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I can understand that a little slop in the threads beneath the alignment barrel would be OK. But would one also use that tap on the shaft? And if the .308, only, is appropriate for the shaft, seems it would also be appropriate for the butt.
Then what is the purpose of the .312. I've always been confused by this.
Kelly is right on with his offering and has described it very clearly.
If you are new to installing a pin it is imperative that before your center drill, drill, then bore the hole you need to get the cue running true by indicating the joint collar to as close to zero as possible. After shimming to get it running true when you bore the hole it will be completely concentric with the OD. So getting the cue running true is the challenge. Most chucks have run out with some error. It's your job to overcome it if you wish to see a very true pin concentricity.
Good luck,
Rick
Take what ever time it takes to get your cue running true. If will get easier every time thereafter.
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None of the 3/8 10 I've come across need 5/16 hole.
My 3/8 10 tap has a .295 head.
The .308 minor screw is a flat-bottom screw. A copy of the SW but smaller
minor and has one less thread.
Make some mock ups and you will find out what works.
My 3/8 10 tap has a .295 head.
The .308 minor screw is a flat-bottom screw. A copy of the SW but smaller
minor and has one less thread.
Make some mock ups and you will find out what works.
I started a lengthy bit about how what Rick describes as being overkill. HOWEVER, with a less than "optimum" lathe, I can see where it could be necessary. I have a reamer I run after a .377 carbide drill and it takes alot of "Randy" error out of the process. YES, I can bore a hole to specs...... I've also bored a couple out of spec accidentally. The combo I use makes it nearly foolproof and quite repeatable.
Your quite right, I too use 2 chucking reamers in my process. One for the minor after boring undersize and one for the barrel clearance after taping and boring.
I use nine inch long reamers so they find and locate to the bored hole. McMaster Carr sells then in .0005 increments so you get the clearance you desire.
Trying to measure a bored hole is no fun unless you use a gauge pin. Much easier to ream.
Rick
When you make the shaft and use the .308 tap with the .307 hole. This ensures the tap not walking with the .308 nose on the tap. I then use the .312 or 5/16 bit since they are very snug on the .308 pin. The .312 will make it fit snug but not tight.
You might want to experiment to see what works for you.
To be honest, I'm not sure of what "the .312" is that you are referring to. I use the 3/8-10 FB .308 modified pin. My answer was regarding that. Regarding your "little slop" reference in the threads behind the alignment barrel, as I said, those threads are undersized anyway...they are designed to provide a "little slop". The major diameter of the threads that goes into the shaft of my (from Tommy) pin is .373. The major diameter of the threads below the alignment barrel is .359. The minor diameter is undersized as well. There will be no benefit to using the piloted .308 tap down there. It won't hurt either.
Use the correct tap with a correct bore (.308/3.09 bore with a .308 piloted tap) to tap the shaft. Use whatever tap you want to use to tap the threads in the butt. If it feels right to you to use the same exact tap (again, I live cut threads so my perspective of your question is slightly different) then use it. It isn't necessary down there though, what is key during the joint pin installation is the .382 bore for the alignment barrel. I'm not advocating wallowed out threads down there...but thinking you need tight thread tolerances down there is wrong.
EDIT: I looked at Atlas' site. It has been so long since I looked at their taps I guess I forgot or never knew they sold a 3/8-10 tap listed as having a .312 pilot. I guess that is what you were referring to. I don't know when you would want to necessarily use that tap.
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An optimal lathe will have that dead center within a thou.
A 9.7MM drill after a 3/8 spot drill will get that hole straight.
If you have a little wiggle ( less than .382 barrel ) , dead center on the pilot's center hole overnight while the epoxy is drying fixes it .
I'm flexible on my use of the reamer. If I nail it with live tooling, I'm done. The pin tells me that quickly. If I'm real close, the reamer is way safer than trying to take a super small cut with live tooling. Touching up with an endmill isn't the same as touching up with a bit. Well...at least for me.
One thing about reamers is there is a thinking that they will jump in the hole and locate well if the chuck is a little off or the tailstock is a little off. With a long reamer (some guys get them shortened), a lot of chucks won't be accurate way out there, even if the tailstock is centered. I believe when this is the case and the reamer jumps in, a slight taper to the hole results. I think this is why floating reamer holders exist. My .382/.383 reamers are a little long. Sometimes I see a whisper of a jump when they enter the hole, sometimes not.
Thanks for the input! You and MVP are the only ones who seem to understand my question. Since the 3/8 x 10 FB pin is supposed to locate the shaft on the minor diameter of the pin (per DZ Cues), then using a tap that is .004 oversize to the minor seems a contradiction. KJ discussed the rammifications of an interference fit of the pin to the wood in 2010 (http://forums.azbilliards.com/showthread.php?t=153286). So, is the .312 piloted tap more appropriate than the .308?
No. The .308 piloted tap is the correct tap for the .308 pin for the shaft threads. While Brick stated he follows everything up with a 5/16" drill bit, he still used the correct tap to make the threads.
I suspect the .312 piloted tap was made to sell taps. Maybe a few people who were boring to .312 asked for a piloted tap for that bore after the .308 piloted tap for the FB pin came out. I don't know. IMO, if you are going to use the .308 FB pin, ignore the .312 piloted tap, unless you simply want another 3/8-10 tap in your arsenal for other 3/8-10 tapping where you don't need the .308 locating diameter.
There will be small variances from cuemaker to cuemaker regarding the exact numbers. Experience, methods, tooling, shaft insert type (if there is one), shaft thread treatment after tapping, etc all have an influence on the gnat's ass level. How you arrive to the gnat's ass should be decided by you over time after some experimentation and testing.
If you bore to .307, you are forcing a piloted .308 tap in. The wood will be giving way. Actually, if the bore is .30800000000 and the tap's pilot is .3080000000, that won't fit either and something has to give. The tap will win. The result is a very snug fit. If the pin is too tight when screwing the shaft on, environmental changes can cause the pin to seize. That happened to one of my local cues after the customer left the cue in the car all day during a lengthy rain. Brick won't have that problem since he chases everything afterward with .312 drill. He is in Memphis I think. Bad humidity. Maybe he has found a very snug tapping procedure and then opening the minor a little afterward is best for him.
Personally, I bore to .309. I believe a .0005 clearance on each side of the pilot will not prevent the pilot from doing its job. I live tool. I check the fit. I sometimes run a tap in after live tooling. I sometimes don't. The fit tells me whether I need to or not. I treat the threads afteward. Then I burnish the threads.
If you are going to use the .308 pin, use the .308 tap for tapping the shaft threads. Exactly how you arrive to a good bore for the tap and a good fit of the shaft on the pin should be dictated by your experience, methods, and tooling.
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Tom Migliore(he makes the pins for Atlas)suggests a 7.8mm(.30708)bit prior to tapping. I have used that method for every pin I've installed with no problems at all.
Thanks. That is good to know, and good advice to the OP.
I might do the same if I tapped, but I use a thread mill. Since I use a thread mill, a .30708 bore would be too tight for me because after threading it would still be .30708.