End Bolt 43tpi die

[4to5to6]

Does anyone have a source for a 43 tpi die, that cuts a 0.081 outer thread diameter on a 0.088 shaft?  Overall total bolt length is 2.22 inches.  I was told these are 5BA threads on a smaller 8BA shaft if this helps.

 

I have offered to build a few end bolts for a large bass to help someone out.

 

Thanks

.

 

Note: Actual specs are 43TPI on a 0.086 shaft - see page 3

Edited September 15 by 4to5to6
Official specs added.

[Chris Ghent]

BA taps and dies are available in the UK, Chronos is a business that comes to mind. I can’t imagine how you would put 5BA threads on an 8BA shaft, 5BA is about 40 thou larger than 8BA. 8 BA (86thou) would be thin for a regular bolt (usually around 7BA) let alone one more than two inches long. 5BA at 126thou would be more likely.

 

Sounds like you need to put a micrometer on the shaft and a thread gauge on the threads. 

 

 

[4to5to6]

 

5 hours ago, Chris Ghent said:

BA taps and dies are available in the UK, Chronos is a business that comes to mind. I can’t imagine how you would put 5BA threads on an 8BA shaft, 5BA is about 40 thou larger than 8BA. 8 BA (86thou) would be thin for a regular bolt (usually around 7BA) let alone one more than two inches long. 5BA at 126thou would be more likely.

 

Sounds like you need to put a micrometer on the shaft and a thread gauge on the threads. 

 

 

 

Measurements were made with a digital caliper and a set of pitch gauges.  I am sure they are accurate.

 

5BA is 0.126 and 43 tpi.  8BA is 0.086 from the chart so “5BA threads on a 8BA shaft”.

 

We’ll have to go back in time and ask Swiss engineer Mr. Louis Lachenal why he chose this particular thread.  They seem to have stood the test of time.

 

I’m going to butcher a 5BA die by cutting it into three pieces then make a special holder so I can adjust these down to 8BA.  Necessity is the mother of invention?!?!?!

 

Wish me luck 😂

.

Edited September 10 by 4to5to6

[Clive Thorne]

Is this a "Wasted" bolt, i.e. the shaft is narrower tha the thread? possibly to stop it binding in the hole. Or it could have the original have been rolled, which will produce a thread diameter bigger than the original shaft.

 

[adrian brown]

Some years ago, I made my own die in order to make a set of new end bolts for one of my Jeffries Anglos. It goes without saying that you have to make a tap first, but if you have access to a screw cutting lathe and a milling machine, it's not too difficult, just quite time consuming!

 

One of the problems with the Jeffries thread is that it's not a "normal" V section thread, but looks almost sinusoidal in profile. I used a rounded bit to cut the thread and then ran a stone over the peaks to try to mimic it. Once I had made a thread that fitted snugly in the "nut plates", I hardened the tap and ground the clearance flutes using a mini grinder attached to the milling machine.

 

The nerve-wracking bit was using the tap to cut the thread in a piece of gauge plate to make the die, but once that was done, it was easy to drill clearance holes and file them to shape.

 

Adrian

 

 

[Stephen Chambers]

5 hours ago, 4to5to6 said:

We’ll have to go back in time and ask Swiss engineer Mr. Louis Lachenal why he chose this particular thread.  They seem to have stood the test of time.

 

There is no possible way that Louis Lachenal could  have chosen to use a BA thread - he died in December 1861, whilst BA threads were only developed by the British Association in 1884, and in use since 1903.

 

"Concertina threads" go back before there was standardisation of threads, and small workshops produced machine screws with various non-standard threads.

[4to5to6]

3 hours ago, adrian brown said:

 

Some years ago, I made my own die in order to make a set of new end bolts for one of my Jeffries Anglos. It goes without saying that you have to make a tap first, but if you have access to a screw cutting lathe and a milling machine, it's not too difficult, just quite time consuming!

 

 

Adrian… Wow! Very impressive.  The idea of making a tap and die crossed my mind but I don’t have acetylene so annealing/tempering would be difficult.  If the adjustable die doesn't work, I’ll have to go this way.

 

The BA threads are very rounded off at the peaks and valleys. “sinusoidal” is a good way to describe them.

 

Clive… These bolts are not rolled.  The thread OD is the same size as the shaft.

[4to5to6]

16 minutes ago, Stephen Chambers said:

 

There is no possible way that Louis Lachenal could  have chosen to use a BA thread - he died in December 1861, whilst BA threads were only developed by the British Association in 1884, and in use since 1903.

 

"Concertina threads" go back before there was standardisation of threads, and small workshops produced machine screws with various non-standard threads.

 

Stephen… I stand corrected.  Indeed BA threads were standardized after Louis Lachenal’s days although BA threads have a strong metric influence long before the metric standardization so I presumed the Swiss influence.  Then again, that’s only 23 years difference so the threads could have been around before the standardization.  Bolts!  Threads!  Standardization.  It’s like discussing A440 versus A453 Philharmonic pitch.

 

I’m more interested in how to get this job done then the history.  

[Chris Ghent]

7 hours ago, 4to5to6 said:

 

 

Measurements were made with a digital caliper and a set of pitch gauges.  I am sure they are accurate.

 

5BA is 0.126 and 43 tpi.  8BA is 0.086 from the chart so “5BA threads on a 8BA shaft”.

 

We’ll have to go back in time and ask Swiss engineer Mr. Louis Lachenal why he chose this particular thread.  They seem to have stood the test of time.

 

I’m going to butcher a 5BA die by cutting it into three pieces then make a special holder so I can adjust these down to 8BA.  Necessity is the mother of invention?!?!?!

 

Wish me luck 😂

.

Then they are not BA

[Chris Ghent]

4 hours ago, adrian brown said:

Some years ago, I made my own die in order to make a set of new end bolts for one of my Jeffries Anglos. It goes without saying that you have to make a tap first, but if you have access to a screw cutting lathe and a milling machine, it's not too difficult, just quite time consuming!

 

One of the problems with the Jeffries thread is that it's not a "normal" V section thread, but looks almost sinusoidal in profile. I used a rounded bit to cut the thread and then ran a stone over the peaks to try to mimic it. Once I had made a thread that fitted snugly in the "nut plates", I hardened the tap and ground the clearance flutes using a mini grinder attached to the milling machine.

 

The nerve-wracking bit was using the tap to cut the thread in a piece of gauge plate to make the die, but once that was done, it was easy to drill clearance holes and file them to shape.

 

Adrian

 

 

Nice job…

[4to5to6]

Sounds like the only way to get this die is to custom make it. 

 

Thanks everyone for your feedback.

[Stephen Chambers]

1 hour ago, 4to5to6 said:

I’m more interested in how to get this job done then the history.  

 

I guess that's at the root of your problem then. The thread you're describing sounds very much like the traditional (085" x 44 TPI. 1927 bolt; 0.083" x 44 TPI 1975 bolt (Dickenson) 0.084" x 44 TPI - according to Geoff Wooff) "concertina thread" as used by Wheatstone's to this day. 😉

 

If you examine the thread on what was formerly my amboyna TT, you'll probably find it conforms to spec.

Edited September 11 by Stephen Chambers
Edited to give credit where it's due

[Stephen Chambers]

9 minutes ago, 4to5to6 said:

Sounds like the only way to get this die is to custom make it. 

 

I'd suggest asking Steve Dickinson...

[alex_holden]

As I understand it the BA standard was based on the Swiss Thury standard, which was in turn based on a study of various non-standardised threads in use at the time by Swiss watch makers. Louis Lachenal was a Swiss watch maker before he came to England. An important feature of this family of thread forms is the rounded crest and root, which reduces stress risers.

 

I think it is fair to describe the 'concertina thread' as having a form like BA, approximately the same major diameter as 8BA, and approximately the same pitch as 5BA. That doesn't mean it is a BA thread. A complicating factor is that there are slight differences between the various manufacturers which make them incompatible with each other. e.g. a die for Jeffries end bolts probably won't make bolts suitable for Wheatstone nut plates.

 

A few years ago I tried to commission a specialist firm to make a tap and die set to replicate Wheatstone threads. They were quite difficult to deal with and quoted me an astonishing price (I suspect they simply didn't want to take the job). I also briefly experimented with making my own tap but was much less successful than Adrian.

 

@4to5to6: you don't need/want an acetylene torch to harden tool steel. A propane torch and a few fire bricks arranged around the part gets plenty hot enough for hardening. You want to heat it gently and sustain the temperature for a while so it has time for the molecules to rearrange all the way through, but don't overheat it because that causes large crystals to form. You can temper it either with a low flame and watching the colours, or you can do it in a conventional kitchen oven if you trust the thermostat (I've also used a deep fat fryer!). I also have a proper temperature-controlled electric heat-treating oven but rarely use it because it's a bit of a faff to set up and takes a while to get up to temperature.

[4to5to6]

Thanks Stephen.  I greatly appreciate your help.  And thanks for the push as usual and please forgive my impatience.  I’ll search for Geoff’s thread (pun intended) on concertina bolts.  He’s a highly respected craftsman and instrument builder who has set me straight countless times.  I wait to be humbled again.  I have a container full of spare bolts and bolt plates but often don’t have the one that fits.  Actually, most of the time. There was certainly no standard, especially in the early instruments.  I will check again but was quite convinced for this one that I was after the 5BA thread / 8BA shaft combo.  As stated in the OP, I was just enquiring to see if this threading die was commonly available somewhere in the world.

 

I will dig deeper…

 

I just checked and have the metric & America SAE type & British Whitworth & BA pitch gauges as well as a simple tpi gauge and will use my very nice Mitutoyo digital calliper to get the shaft sizes.

 

I still absolutely love your former 31xxx Amboyna TT.  Wow!  What a joy to play. Possibly the best concertina ever made although I am sure these can be fighting words.  All I know is that there is music I can only play on this instrument although also love my mint condition 1856 treble who’s serial is sandwiched between a Blagrove and Regondi purchase. I’m sure that I’m not alone in this but have reversed engineered countless concertinas trying to come up with the perfect reed scale myself and this Amboyna TT still tops the list in both design and craftmanship. The spread sheet curves don’t lie and back me up.  I’m actually currently measuring the reeds on my 1922 G to G, 56 button model 14 as I am thinking of selling it and the reeds are near perfect as well. Only half way done so haven’t seen the curves yet.  Steve Dickinson did an absolute perfect job of setting up air flows, voicing the reeds, sizing valves etc. etc. on the Amboyna TT.

 

Let’s please put this on hold for a few days until I get some time to do some reading and take some measurements.

 

I already split apart my 5BA die… It broke while trying to squeeze it down to size but I hope to turn lemons in lemonade so broke it again and started designing an adjustsble holder which I will soon CNC out.

 

I just checked a piece of the 5BA die with a bolt out of the large single action Wheststone bass, circa 1900 and the 5BA 43 tpi is a match.

 

Okay, okay…  my wife is mad but I just dug out my tools and took the end bolts out to measured them:

 

C. 1900 SA bass - 0.0855, 44tpi closest

1926 Amboyna TT - 0.0850 5BA closest

1927 ME TT - 0.0860 5BA closest

 

Although 44tpi, the bass bolt easily threads into both the 1926 and 1927 Aeolas by hand.

 

Overall bolt lengths are 2.218, 1.240, 1.162 inches respectively.

 

Interesting enough, my SAE thread gauge jumps from 42 to 44 tpi.  I’m trusting that my 5BA gauge and broken die are 43 tpi.

 

Maybe Jake can jump in here and come to my rescue. 😉 I’ve already had emails from both Steve and Jake but not sure what is proprietary info.

 

The true test will happen when I make the bolts with the die and also single point on the lathe.

 

Okay… I must go and put the end bolts back in and beg forgiveness from my wife.

 

Edited September 11 by 4to5to6

[4to5to6]

Thanks Alex.  The Swiss Thurly standard explanation helps me with the Louis Lachenal reference.  It was off the cuff but maybe that’s where I got the connection from as I understand he was a Swiss Engineer and screw maker. The time line is off as Stephen pointed out but practices are often put into place years before they become official standards.

 

Is it not true that a feature of the BA thread is the rounded crest and root versus the sharper peaks and valleys of SAE and metric threads?

.

Edited September 11 by 4to5to6

[alex_holden]

9 minutes ago, 4to5to6 said:

Is it not true that a feature of the BA thread is the rounded crest and root versus the sharper peaks and valleys of SAE and metric threads?

 

Yes, that's right. Incidentally Whitworth thread and its descendents (BSF, BSP etc) also have a rounded form.

[Theo]

9 hours ago, 4to5to6 said:

 

 I don’t have acetylene so annealing/tempering would be difficult.  

You don't need acetylene, a propane torch will give you the temperature you need for hardening.  Its not so easy getting the right temperature for tempering, especially for small items with complex shapes.