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May 26, 2020 - 10:09:02 AM
13011 posts since 6/29/2005

I just broke one of my precious 8-26 taps.


I keep thinking someone will step up to the plate and start offering them to banjo makers and repair people.  Does anyone out there know if they are being made again and if so, by who?

Does anyone know a place where they will make special sized taps at reasonable prices?

Victor Machinery sells 8-24 and 8-30, but not 8-26.  I was thinking about contacting them unless someone has a better idea.

Thanks,

Ken

May 26, 2020 - 10:57:12 AM

441 posts since 10/17/2006

I bought one last year or the year before, but can't find any information on it. I paid about $24 which hurt, but I now have one.
I probably don't have any use for it, so if you'd like to offer something in trade....

May 26, 2020 - 11:24:49 AM
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2199 posts since 4/7/2010

$24 seems like a bargain to me.

Seems every couple of years someone brings up needing 8-26 taps and dies. The last time my circle of banjo building friends had a conversation about this, there was no consensus as to exactly what to buy. Choices of cutting or forming, spiral point or bottoming, and likely a half dozen other picky details that we all could not agree on.

I am lucky enough to have a small supply I inherited from my dad, so likely, at my current use, I'll be able to finish my career with what I have.

One detail in my 8-26 notes is they can be made by Widell and ordered through McMaster-Carr. The more you have made, the better the price.

I'll post other tips as they pop into my head.

Bob Smakula

May 26, 2020 - 11:30:16 AM

13011 posts since 6/29/2005

quote:
Originally posted by banjosam

I bought one last year or the year before, but can't find any information on it. I paid about $24 which hurt, but I now have one.
I probably don't have any use for it, so if you'd like to offer something in trade....


What would you like to trade?  I'm also happy to buy it from you—Ohio's very close and it would probably get to me an a couple of days.

Ken

May 26, 2020 - 11:43:30 AM
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DRH

USA

480 posts since 5/29/2018

8-32 and 8-36 are the standards for national machine screw threads. 8-26 is certainly an oddball.

The machining manager where I worked has ordered custom tap sizes in the past. I'll call him and get back to you.

EDIT:  I could't reach the machining manager.  I did talk to the owner, a close personal friend.  He said they will find a source and get a quantity price.  They buy so much tooling I'm sure they can get better prices than any small business. 

So get together and decide how many of you need 8-26 taps.  I also need to know what type.

Edited by - DRH on 05/26/2020 11:58:46

May 26, 2020 - 11:58:13 AM

13011 posts since 6/29/2005

quote:
Originally posted by DRH

8-32 and 8-36 are the standards for national machine screw threads. 8-26 is certainly an oddball.

The machining manager where I worked has ordered custom tap sizes in the past. I'll call him and get back to you.


Thanks, Doug!

I used 8-32 for a while, but sadly, the 8-26s just work smoother for banjo nuts.  The odd thing about it is that 8-26 ought to be a standard size— the standard jumps from 6-32, which makes sense, to 8-32, which is actually fine, but is classified as "NC", then to 10-24 . You'd think that 8-26 would be a more logical transition for #8 from 6-32 to 10-24.  You can get 8-24 and 8-30 as "specials" for a reasonable price, but not 8-26.  I think some old banjos used to have 8-24.

May 26, 2020 - 12:05:56 PM

DRH

USA

480 posts since 5/29/2018

8-26 has the same problem as 6-32. The root diameter is proportionately so much smaller than the major diameter that the core is insufficient to withstand breakage.

6-32 is the most easily broken tap in the machine screw standard. I learned early in my career to never use 6-32 in my designs.

My neighbor has the weirdest collection of taps I've ever seen. He even found me a M9X1.25 helicoil for my wife's brakes. I'll walk over and ask him in a moment.

May 26, 2020 - 12:17:26 PM

13011 posts since 6/29/2005

quote:
Originally posted by DRH

8-26 has the same problem as 6-32. The root diameter is proportionately so much smaller than the major diameter that the core is insufficient to withstand breakage.

6-32 is the most easily broken tap in the machine screw standard. I learned early in my career to never use 6-32 in my designs.

My neighbor has the weirdest collection of taps I've ever seen. He even found me a M9X1.25 helicoil for my wife's brakes. I'll walk over and ask him in a moment.


That's interesting.  I just had a case where someone with one of my banjos changed heads, and in doing so torqued some of the nuts down so hard that the end of the hook bottomed out on the solid-ball end of the nut, causing the hook to shear off. 

I am sending him replacement hooks and nuts, but at the same time, I have decided not to use solid ball end nuts any more and announced that on my website.  Now I know why Vega switched to open end way back when. Ironically, many of the people currently selling boutique hardware are using solid ball end ones, and people who make their own banjos must have hook lengths all over the map.

May 26, 2020 - 1:05:38 PM

DRH

USA

480 posts since 5/29/2018

The other problem with 6-32 and 8-26 is the small clearance flute. If you are blind tapping the removed material has to come out the top.

Spiral flute taps bring the chips out the top. Spiral point taps, sometimes called gun taps, push the chips ahead of the tap. These are the most reliable but you have to have a thru hole or the chips get packed in the bottom of the hole. Imagine trying to get packed chips out of a very small blind hole. I've had to do this many times when a spiral flute tap wasn't available. Not fun!

Hand taps just plain stink. Machine taps work better in nearly all cases.

My neighbor didn't have an 8-26. He also said the public transit system maintenance shops where he worked for 25 years didn't work on many banjos;)

Still waiting on a response from my friend. If we can get enough commitments to make a quantity order I will get them and pass them on at cost. In the short term I can't offer much help.

May 26, 2020 - 1:37:03 PM

DRH

USA

480 posts since 5/29/2018

quote:
Originally posted by Ken LeVan

I used 8-32 for a while, but sadly, the 8-26s just work smoother for banjo nuts.  The odd thing about it is that 8-26 ought to be a standard size— the standard jumps from 6-32, which makes sense, to 8-32, which is actually fine, but is classified as "NC", then to 10-24 . You'd think that 8-26 would be a more logical transition for #8 from 6-32 to 10-24.  You can get 8-24 and 8-30 as "specials" for a reasonable price, but not 8-26.  I think some old banjos used to have 8-24.


The 32 TPI series includes 6-32, 8-32, and 10-32, along with several specialized threads such as used on instrumentation.  The advantage of keeping one pitch is that it reduces tooling costs and setup time on automatic screw machines.

There is also a 12 TPI series that goes from one inch diameter up to somewhere around ten inches, again because of earlier manufacturing methods.

If you were having problems with 8-32 it may be because fine threads are more sensitive to diameter tolerances.  The wire used to make hooks and the tap drill size used for the nuts require tighter tolerances with finer threads.  There is less proportional difference between root and crest diameter with fine threads.

Finer threads, however, always produce a stronger connection when properly made.  The root diameter is larger and that is the only thing that determines tensile strength.  They are just a lot harder to make by hand.

May 26, 2020 - 2:48:53 PM

7676 posts since 1/7/2005

Ken,
I've cobbled taps in the past for one-off jobs by taking a steel bolt with the needed pitch and filing a groove on each side to make cutters. Follow this with a tapering on the end. Then I did a quick heat/quench hardening, and it worked just fine. But I don't think it would hold up well for any kind of quantity production.

DD

May 26, 2020 - 4:35:37 PM
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13011 posts since 6/29/2005

quote:
Originally posted by Dan Drabek

Ken,
I've cobbled taps in the past for one-off jobs by taking a steel bolt with the needed pitch and filing a groove on each side to make cutters. Follow this with a tapering on the end. Then I did a quick heat/quench hardening, and it worked just fine. But I don't think it would hold up well for any kind of quantity production.

DD


I appreciate that Dan, and Thank you.

Unfortunately, I  need to thread hundreds of nuts pretty quickly, so I need to find something that will hold up.  I think I broke the one I just broke because it overheated and got stuck in the nut.  Once I find some who can make them, I'll buy several so I don't have to go through this again.

If I had any sense, I'd buy a lot and sell them to everyone else who needs them

Ken

May 26, 2020 - 5:58:03 PM

DRH

USA

480 posts since 5/29/2018

I'm still waiting on a call about those taps. Will probably call him again in the morning.

If I ordered 20-30 taps, would I be able to sell them?

Ken;
I've used every tapping fluid on the market, even did torque measurement studies on our cnc machines. The best we tested is Castrol Moly-Dee. It stinks and stains but it was the only one we found that would give us clean cuts in A36 plate. I did another study for wear and was able to get 2400 holes from one tap in gummy steel. That was a 1/2-13 tap at 390 RPM, tapping a 2 inch deep thru hole. That tap is still sharp. I kept it as a trophy.

The current product has been reformulated for environmental reasons. Don't know how well it works compared to the old stuff. I'll ask when I call about the taps tomorrow. They buy it in case lots.

May 26, 2020 - 6:25:45 PM

RB3

USA

709 posts since 4/12/2004

This subject has been discussed previously, and, as I have pointed out in the past, the use of "8" in combination with a pitch of 26 threads/inch does not conform to any recognized thread standard.

There is however a company named British Tools & Fasteners in Lyons, NY that sells taps and dies that have a thread specification of BSC 5/32-26. The price of the taps is $19.80/each. That thread specification is consistent with the major diameter and thread pitch of the tension hooks used on pre-war, Gibson banjos. Below is a link to the British Tools & Fasteners web site.

British Tools & Fasteners

May 26, 2020 - 6:45:19 PM

DRH

USA

480 posts since 5/29/2018

The major diameter of a #8 is 0.164 = (.060 + (8 X .013)).

5/32 = 0.156

I wonder if BSC 5/32-26 is what luthiers have been using all along.

Time to get out the micrometer.

May 26, 2020 - 7:42:35 PM

RB3

USA

709 posts since 4/12/2004

According to the Unified Screw Thread standard, the actual range of the major diameter of an 8-32 UNC-2A external thread is .1571-.1633.

I believe that the BSC 5/32-26 thread is associated with wheel spoke components used on old, British motorcycles and I suspect that somehow in the distant past, that that thread profile was incorporated into the tension hooks and nuts that were used on the old banjos. I do not, however have any documentary evidence that would prove that.

But, I did measure one of the tension hooks on my pre-war, Gibson banjo. The body diameter of that tension hook is: .1565". The major diameter of the thread on that tension hook is: .1545"

I also have another banjo that is a Gibson copy, parts banjo that I acquired about 40 years ago. I believe that all of the hardware on that banjo came from Stewart-McDonald. A tension hook from that banjo also has threads with a pitch of 26 threads/inch. The body diameter of that hook measures: .1585". The major diameter of the thread on that hook measures: .1610".

May 26, 2020 - 9:23:47 PM

nakigreengrass

New Zealand

5075 posts since 5/16/2012

My old trusty machinist handbook doesn't help much either. The nearest is a number 8 x 24 tpi "cycle thread "....however you may want to consider this....

.if your number series 8 tap measures .164" o.d... it should be 4.16 mm od.... and, your pitch of 26 tpi should be .038"...which is very close to a 1mm pitch (.039" ).....if so....then I would suspect a 4mm dia x 1mm pitch tap would do the job.

I wouldn't at all be surprised that 8-26 isn't actually 4mm x 1mm....stranger things have happened....like.... the metric pipe threads are actually just the imperial British threads...just given a new name....but they are identical.

Edited by - nakigreengrass on 05/26/2020 21:32:47

May 27, 2020 - 4:21:09 AM

2659 posts since 12/4/2009

Hello,

Would this site help in the quest?
 

https://www.tracytools.com/taps-and-dies/cycle-%20taps-dies

Also, this thread says Bill Rickard makes them. 

https://www.banjohangout.org/archive/307004

Edited by - Aradobanjo on 05/27/2020 04:27:14

May 27, 2020 - 4:28:25 AM

13011 posts since 6/29/2005

quote:
Originally posted by nakigreengrass

My old trusty machinist handbook doesn't help much either. The nearest is a number 8 x 24 tpi "cycle thread "....however you may want to consider this....

.if your number series 8 tap measures .164" o.d... it should be 4.16 mm od.... and, your pitch of 26 tpi should be .038"...which is very close to a 1mm pitch (.039" ).....if so....then I would suspect a 4mm dia x 1mm pitch tap would do the job.

I wouldn't at all be surprised that 8-26 isn't actually 4mm x 1mm....stranger things have happened....like.... the metric pipe threads are actually just the imperial British threads...just given a new name....but they are identical.


Thanks a million!

I was trying to figure if there was a metric close equiavalent but could not find a comparison chart because the thread pitches are measured differently on the two systems.

You have given me a Rosetta Stone.  So far I can only find 4mm x .7mm or .75mm but I will keep searching.

May 27, 2020 - 9:25:04 AM

2659 posts since 12/4/2009

Hello,

Hmm... something is not right with marketing or the math. When I look at my thread gages, 1.25mm looks closer to 20 TPI. 1.0mm is nearly the same as 36 TPI

That is also confirmed by marketing. I see no analogous mm to match 26 TPI. 26 is really shallow compared mm threads. I would suspect the value to fall between 1.0 mm and 1.25mm.

May 27, 2020 - 10:45:01 AM

DRH

USA

480 posts since 5/29/2018

One inch equals 25.4 mm. A pitch of 1.0 mm would be 25.4 threads per inch, very close to 26 TPI.

BSC stands for British Standard Cycle. The Wikipedia article explains it.

en.wikipedia.org/wiki/British_...ard_Cycle

May 27, 2020 - 11:31:33 AM

2659 posts since 12/4/2009

Hello,

Yes, close is good with hand grenades and horseshoes. With threads, they work or they don’t. Like equals like. When I compared 1mm to 26 TPI in sunlight, I could see similarities. The SAE appears more rounded. With metric, the angle is to a point.

May 27, 2020 - 12:29:04 PM

DRH

USA

480 posts since 5/29/2018

quote:
Originally posted by Aradobanjo

Hello,

Yes, close is good with hand grenades and horseshoes. With threads, they work or they don’t. Like equals like. When I compared 1mm to 26 TPI in sunlight, I could see similarities. The SAE appears more rounded. With metric, the angle is to a point.


The differences you see in thread profile are usually due to manufacturing methods.  Rolled threads almost always have a rounded root.  Thread rolling is less costly than cutting and improves tensile strength.

ISO, SAE, and Unified standards use nearly identical thread profiles.  A sharp root or crest is always a deviation, even though it is common in mass produced fasteners.

May 27, 2020 - 1:19:48 PM

13011 posts since 6/29/2005

I want to thank everyone, and I thought this has been a lively discussion.

At this point, I have arranged a trade with a BHO member for one he has and is willing to part with, so I will have an actual 8-26, and I have also ordered a bicycle one from England that purports to be the same thing.

IF, and "if" is the operative term, the English one works with the banjo threads I have, I will be able to report that this problem has been solved.

I still have not been able to find a source for 4mm x 1mm taps & dies.

One nagging question is that you can buy fake Mastertone hooks and nuts from several Asian suppliers, on eBay, which they call "replacements" or something similar —what is the thread pitch on those?—did those guys go to the trouble of getting 8-26 thread-making equipment?  I know some of the Asian ones that don't look like Gibson style are really fine pitch, nothing like 8-26.  In the past, I have bought some of the "replacement" ones and they looked just like the Gibson style, had a coarser thread, but I didn't think to cross-check the threads with 8-26 ones.

Thank heaven the dies don't break so easily, but I'm sure not going to thread any steel with my 8-26 die.

Edited by - Ken LeVan on 05/27/2020 13:23:03

May 27, 2020 - 1:22 PM

nakigreengrass

New Zealand

5075 posts since 5/16/2012

Yes...the thread angle's are likely to be different....8-26 is probably 55 degree's ...and metric will be 60 degrees. It is the same as between Whitworth and UNC. which also have the same tpi ( except 1/2" ). The angle difference shouldn't be a problem, most machinist these day;s pretty much ignore thread angles for anything other than precision uses.  You American's really know how to cause trouble in the engineering world.

Edited by - nakigreengrass on 05/27/2020 13:34:18

May 27, 2020 - 1:28:23 PM

13011 posts since 6/29/2005

quote:
Originally posted by nakigreengrass

Yes...the thread angle's are likely to be different....8-26 is probably 55 degree's ...and metric will be 60 degrees. It is the same as between Whitworth and UNC. which also have the same tpi ( except 1/2" ). You American's really know how to cause trouble in the engineering world.


I remember back in the 70s when I was really interested in bicycle racing, and I had a Raleigh, the French builders had a reputation for making up their own thread pitches, so the bottom bracket (and every other part) on a Peugeot was not interchangeable with a Gitane or a Motobecane or any English, Italian, or Japanese bike, and I had thought the French were the ones who invented the metric system.

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