28 or 30 tpi x 1/8″ thread. Any ideas?

Advert

New Replies

Report Bug

Help/FAQs

28 or 30 tpi x 1/8″ thread. Any ideas?

This topic has 12 replies, 8 voices, and was last updated 29 January 2014 at 14:18 by Tom Sperrey.

Viewing 13 posts - 1 through 13 (of 13 total)

Author

Posts
28 January 2014 at 12:50 #141899
Tom Sperrey
Participant
@tomsperrey81641
I have a US-made 12-string Gibson guitar manufactured in 1985. The tailpiece (the part that retains the non-tuner end of the strings) is broken (see picture). The part that's broken is formed from 1/8" chromed brass rod threaded at each end and bent into a 'U' shape to retain the string holder. Gibson no longer hold this part and no-one there seems to know the thread used.

I can shorten each end by half an inch and then rethread to repair it. As I'd like to retain the original acorn nuts I need to know the thread in order to purchase the appropriate die. The threaded part is half an inch and by my count has either 14 or 15 threads to it (so 28 or 30 tpi).

Does anyone have any idea what thread this might be?

Regards,

Tom S.
Advert

28 January 2014 at 12:50 #17280
Tom Sperrey
Participant
@tomsperrey81641
28 January 2014 at 16:50 #141913
KWIL
Participant
@kwil
What is the diameter of the rod?
28 January 2014 at 16:52 #141915
JasonB
Moderator
@jasonb
Can't think of much in those tpi

You could have 1/8 x 26 brass but unlikely on a US item

At the other end of the scale #5×36 UNS is 1/8" but unless you have undercounted too far from your 28-30 tpi

Edited By JasonB on 28/01/2014 20:23:30
28 January 2014 at 16:54 #141916
JasonB
Moderator
@jasonb
Kwil

"formed from 1/8" chromed brass rod"

What is the dia of the thread as if its a bit smaller maybe #4x32UNS which is 0.112"

Edited By JasonB on 28/01/2014 16:59:58
28 January 2014 at 18:06 #141921
Gray62
Participant
@gray62
Hi, a possible source for parts is Stewart-MacDonald in the USA they do replacement trapeze tailpieces and they may also be able to answer your query regarding the thread size, a wealth of knowledge on guitars there.

Out of interest, Which guitar is this for?
28 January 2014 at 19:12 #141926
Tom Sperrey
Participant
@tomsperrey81641
Kwil, JasonB, Coalburner – thanks all.

Yes, rod diameter is 0.126" and thread, curiously, 0.128", according to my digital calipers.

Coalburner, thanks for the link to Stewart-MacDonald. I've taken a look there, but they have only a generic trapeze which I've seen on another site. The guitar in question is a Gibson Heritage 12-string, or at least that's what it was sold to me as. I may have the date of manufacture wrong………..

Tom S.
28 January 2014 at 19:20 #141927
Roderick Jenkins
Participant
@roderickjenkins93242
Tom,

Your larger diameter for the thread suggests that it has been rolled rather than cut. My guess is that it's a spoke thread of some sort but it doesn't fit any of the cycle threads listed in Ian Bradley's screw threads and twist drills.

Touchstone tonewoods are good for instrument spare parts but are likely to be generic.

Rod

Edited By Roderick Jenkins on 28/01/2014 19:22:31

Edited By Roderick Jenkins on 28/01/2014 19:23:01
28 January 2014 at 19:53 #141928
Jeff Dayman
Participant
@jeffdayman43397
You might check if it is #5-40 UNC. That is a common thread on US made guitars.

There is a 28 TPI series of US threads, the UN and UNR series, but they usually start at #12 or 1/4" which are much larger than 1/8" dia.

Good luck, JD
28 January 2014 at 20:37 #141929
KWIL
Participant
@kwil
Jason, I just thought the diameter might be as approximate as the pitch choice given by the OP
28 January 2014 at 23:06 #141941
julian atkins
Participant
@julianatkins58923
hi tom,

i would remake the part broken with 1/8" stainless rod bent to shape after threading the ends 1/8" BSW or 5BA. you can make new dome headed nuts to suit out of stainless.

at some time in the future you might be able to acquire a spare, or get a chrome plated part made with the correct thread to re-use the original dome nuts.

i am rather surprised at the design bearing in mind the force applied by the strings. doesnt seem up to Gibson standard. are you sure this part is original?

there are much better designs of these parts. the older Gibsons certainly had a much better design.

cheers,

julian
28 January 2014 at 23:47 #141950
Nathan Sharpe
Participant
@nathansharpe19746
Tom,

Have you tried Janikas music store on Ebay? Looks like they have a good selection of trapeze tailpieces. I have bought from them and am happy enough with their service/quality.

Nathan.
29 January 2014 at 14:18 #141985
Tom Sperrey
Participant
@tomsperrey81641
Rod, JD, Julian, Nathan, Thanks all.

Touchastone and Janika's both look like excellent guitar parts resources but neither offer the original or even a close copy. As I'm trying to keep the guitar in original shape I'd like to avoid a pattern part.

It's definitely not a 40tpi thread, JD, but thanks for the thought,. Closest I can get is an old Brass Thread which is 1/8" x 32tpi, but only Tracy's list it and they're out of stock.

Julian, I think your stainless rod solution is the direction I'll have to go in. My skills and equipment aren't up to makingstainless 5BA dome nuts but I've found a source for them. Looking through Google images I note that does indeed seem to be the original design and that it's the older Gibsons 12-strings that have it. Maybe they abandoned it in view of similar failures – who knows?

Grateful for all your help, anyway.

Tom S.
Author

Posts