5/16-18 joint mystery.

[T411]

Threads have a major and minor diameter which is not the same as the pitch diameter. The pitch diameter is why some shafts don’t fit properly on different brand cues. The pitch is critical in the function of the joint (joint as in any screw joint and not necessarily pool cue screw joint). How critical is to cue making? Im not going to get into it other than say I think it’s more critical than people think.

 

[DeeDeeCues]

Threads have a major and minor diameter which is not the same as the pitch diameter. The pitch diameter is why some shafts don’t fit properly on different brand cues. The pitch is critical in the function of the joint (joint as in any screw joint and not necessarily pool cue screw joint). How critical is to cue making? Im not going to get into it other than say I think it’s more critical than people think.

Okay, you are talking about a few different things here.

Major, minor, and pitch diameters are all related for any given thread profile. If you choose a thread profile, you only get to choose one of the other diameters. The other two diameters will be set based on those two pieces of information.

When you say, 'pitch' instead of, 'pitch diameter', I don't know if you intended them to be interchangeable or not, but they aren't. The pitch of a screw for a static joint really only comes into play in the case of vibration or shock. In a cue a third variable is at play in that some of the materials we thread are limited to how fine the thread can be before problems with stripping arise. It should be obvious to all but the most casual of observers that you can't screw a pin with 14 threads per inch into a hole threaded at 18 threads per inch.

This is a horrible case of de-evolution. Two hundred years ago was about the start of standardizing threads, where you didn't have to go back to the original machine shop to get a new screw made for whatever doodad you were working on. Thanks to idiots like stroud and mezz, we are now working in an industry that has sent us back in time to pre industrial revolution conditions for absolutely no benefit. It is well proven that the two most popular joints from the past forty years are sufficient for cue construction. The claims that any of the other garbage adds some value have not been proven.

I love the alignment barrels on pins. I don't hate the 3/8-10 modified because it still works well in a proper 3/8-10 hole. They can shove the gimmicks and I won't use them or work on any cue with them.

 

[3kushn]

It's been my mission aka nightmare learning about the different joint screws for 30 years. I still don't know them all and new one's are still coming.
Another new one that looks like the 5/16x18 is M8x1.25.
It's out there and looks very similar to Pechauer's quick release.

The OP derailed his own thread talking about other thread forms than a basic 60deg 5/16"-18 thread.
Cueman offered him the answer. I tried to offer ANSI Specs/Limits in support of Cueman, then he's talking about Acme and other thd forms.

Maybe the goal is 100 responses.

 

[T411]

It should be obvious to all but the most casual of observers that you can't screw a pin with 14 threads per inch into a hole threaded at 18 threads per inch.

I actually too casually misread the first posted question… but on AZ I try not assume what I think it is obvious.

It is well proven that the two most popular joints from the past forty years are sufficient for cue construction.

Yes maybe so but I try not to close my eyes to anything that could be more than sufficient. Forty years ago I would have never thought carbon fiber or something other than wood shafts would have ever caught on.

The claims that any of the other garbage adds some value have not been proven.

Agreed garbage never add value.

 

[Michael Webb]

The OP derailed his own thread talking about other thread forms than a basic 60deg 5/16"-18 thread.
Cueman offered him the answer. I tried to offer ANSI Specs/Limits in support of Cueman, then he's talking about Acme and other thd forms.

Maybe the goal is 100 responses.

One thing is for sure
There's eneogh variances in Joint screws to keep the conversations going for a long time!

 

[ShootingArts]

Only Acme threads I ever worked with were the big square ones on some industrial valves. I don't know if those more common looking threads are called Acme also or not. I considered Acme threads for a screw joint thinking I might be able to get the effect of a pilot and a screw in one. Nope, not going to happen. Acme threads are pisspoor when dealing with tolerances.

We were buying dozens of pieces of Acme threaded stock at a time. Ten or twelve feet long, two inch stainless. Some of the threads wouldn't fit our shopmade threaded hubs which we were using standard Acme taps to cut the threads in. The threaded stock makers told us not their problem. The standard was a threaded stud had to thread in a standard Acme nut. Fitting our longer hub wasn't their problem. A little research proved them correct.

While on the subject of fit and contact, standard threads usually have less than fifty percent contact. Where that contact is at can have a lot to do with fit. Some cue builders also take a little off of the inside or outside diameter of threads so their thread is unique. Not better but easiest to come back to them.

The three-eighth ten threads used in a cyntergy shaft won't match the three-eighth ten threads on a G-10 pin. I suspect that it is a pitch issue. They will go on further than something miss threaded but will take two people to get back apart. Sooner or later things are gonna get ugly!

Hu

 

[DeeDeeCues]

I actually too casually misread the first posted question… but on AZ I try not assume what I think it is obvious.

Yes maybe so but I try not to close my eyes to anything that could be more than sufficient. Forty years ago I would have never thought carbon fiber or something other than wood shafts would have ever caught on.

Agreed garbage never add value.

Good post.

I will say that if a joint doesn't loosen during playing, the pin is doing everything that is should, and as far as I can see, it is doing the only thing it can. Different diameters and materials make for options to change balance and weight, maybe some feel. The shape of the thread has nothing to offer in benefits. Due to this, the logical answer is to stick with the easiest thread to manufacture and develop some sort of standard--either off-the shelf bolts (ala a NC 5/16-18), a small common thread (ala 5/16-14), or the 3/8-10 which allows great strength when tapped in wood.

 

[chuckpilegis]

Only Acme threads I ever worked with were the big square ones on some industrial valves. I don't know if those more common looking threads are called Acme also or not. I considered Acme threads for a screw joint thinking I might be able to get the effect of a pilot and a screw in one. Nope, not going to happen. Acme threads are pisspoor when dealing with tolerances.

We were buying dozens of pieces of Acme threaded stock at a time. Ten or twelve feet long, two inch stainless. Some of the threads wouldn't fit our shopmade threaded hubs which we were using standard Acme taps to cut the threads in. The threaded stock makers told us not their problem. The standard was a threaded stud had to thread in a standard Acme nut. Fitting our longer hub wasn't their problem. A little research proved them correct.

While on the subject of fit and contact, standard threads usually have less than fifty percent contact. Where that contact is at can have a lot to do with fit. Some cue builders also take a little off of the inside or outside diameter of threads so their thread is unique. Not better but easiest to come back to them.

The three-eighth ten threads used in a cyntergy shaft won't match the three-eighth ten threads on a G-10 pin. I suspect that it is a pitch issue. They will go on further than something miss threaded but will take two people to get back apart. Sooner or later things are gonna get ugly!

Hu

Cynergy shafts use a 3/10 mod (flat) and regular 3/8x 10, which one are you using?

 

[chuckpilegis]

acme pin not the 1993ish pin used on a Schon

 

[garczar]

acme pin not the 1993ish pin used on a Schon

View attachment 791068

Not a 'screw guy' (got one loose i'm sure) but just what was this pin/screw designed to do? Does it have an application where these 'squarish' threads have an effect on the required connection/snugness?

 

[DeeDeeCues]

Not a 'screw guy' (got one loose i'm sure) but just what was this pin/screw designed to do? Does it have an application where these 'squarish' threads have an effect on the required connection/snugness?

Acme screws are a drive screw, used for moving loads. Most common on lathes and milling machines.

They are also typically used in c-clamps and jacks that come with cars. Both of those are because the screw is cycled through it's entire path often and because the thread profile makes it very strong.

Generally they are high precision and polished for accuracy and wear reduction.

 

[iusedtoberich]

I did see with my own eyes a Scruggs cue with an acme thread form. The cue was made in about 1999.

 

[garczar]

I did see with my own eyes a Scruggs cue with an acme thread form. The cue was made in about 1999.

The so-called ACME Schon's were just a pilot-nose 5/16x14. They did not have the square profile threads of a true ACME screw.

 

[iusedtoberich]

The so-called ACME Schon's were just a pilot-nose 5/16x14. They did not have the square profile threads of a true ACME screw.

The Scruggs I saw did. It looked like a standard 30 degree included angle acme thread. I think he was calling it a 3/8-10 acme. Idk how common it was.

 

[iusedtoberich]

I found one on a search Check out the joint picture it shows the acme thread.

FS: Tim Scruggs Custom 4 Point Pool Cue Ebony, Ivory 2 Shafts

I will be listing some cues for sale in the next few weeks. I'm selling off a collection for someone in my area. The first one is a Tim Scruggs custom cue built in the year 2000. The cue has four veneered points with Ivory and what looks like...

forums.azbilliards.com

 

[Cornerman]

Not a 'screw guy' (got one loose i'm sure) but just what was this pin/screw designed to do? Does it have an application where these 'squarish' threads have an effect on the required connection/snugness?

Drive screws and motion control. They (along with the carriage that rides on the screw) can provide very little backlash, which would be important for motion control. The trapezoidal profile can provide strength as well.

Not all trapezoidal profiles are Acme. What makes this particular thread an acme is that both the thread and the “notch” are the same profile dimensions, as well as some other dimensions that specific to Acme.

 

[cueman]

Hello all.
Posting this here bcuz I searched forums for answers, but found none. Can an expert solve this for me once and for all... Why do some 5/16-18 fit certain cues and not others with same diameter pin and joint?? Example: Players 5/16-18 fits Meucci and Mali, but not Heubler.
Heubler 5/16-18 won't fit Meucci or Players.
These are all supposed to be 5/16-18 thread cues. Somebody rise up and tackle this please.
This is why I've always gone 5/16-14. Lol. Only diff there is piloted varies. Help!!??

You asked the same questions over in the cuemakers forum and here is the answers I posted there for the benefit of those on the main forum.

The thread angle on all mentioned is 60 degree. But the outside diameter varies. Thus Huebler shaft goes on Meucci, but Meucci does not go on Huebler. Common 5/16-18 outside diameter is .310" only two thousandths undersized to true 5/16. But Meucci is often closer to .300" and .304' or so its very common also. Also sometimes the threads are not rolled as deep which makes them fit tighter. Some use a 17/64 (.266") hole in the insert before tapping or threading and others use an F drill (.256") and others use a 1/4 (.250"). So yes thousandths matter and the combination of factors matter. The .300" john screw will go in any of the above tapped inserts, but only the .300" pin will go in the insert tapped into the .250 hole. I wont even go into H factor taps since most use CNC lathes to cut threads now instead of tapping brass parts. But they still use factors to decide how tight the fit is.

 

[straightline]

Wonder if Dr. Dave has any opinions on this.

 

[Michael Webb]

You asked the same questions over in the cuemakers forum and here is the answers I posted there for the benefit of those on the main forum.

The thread angle on all mentioned is 60 degree. But the outside diameter varies. Thus Huebler shaft goes on Meucci, but Meucci does not go on Huebler. Common 5/16-18 outside diameter is .310" only two thousandths undersized to true 5/16. But Meucci is often closer to .300" and .304' or so its very common also. Also sometimes the threads are not rolled as deep which makes them fit tighter. Some use a 17/64 (.266") hole in the insert before tapping or threading and others use an F drill (.256") and others use a 1/4 (.250"). So yes thousandths matter and the combination of factors matter. The .300" john screw will go in any of the above tapped inserts, but only the .300" pin will go in the insert tapped into the .250 hole. I wont even go into H factor taps since most use CNC lathes to cut threads now instead of tapping brass parts. But they still use factors to decide how tight the fit is.

The Question in Posting in both Forums is,
Is More, Less?
Or Less More?

 

[garczar]

Wonder if Dr. Dave has any opinions on this.

I think DD is smart enuff to see all the pertinent info has been duly covered and will avoid diving in.