Hi all,
I have a Calrad FK12 arm which I want to get running as it is cute and I've a VR11 gathering dust.
The arm is Japanese from turn of the 60s and has a non-standard headshell. The machine screws that attach the cartridge appear to be 1/4" long, 3/32" diameter, with a 46tpi gauge. I need longer screws as the headshell sides interfere with the cartridge and it needs a spacer, but can't find this diameter with this pitch, the closest seems to be 3-48 unc. Would this work if only screwed in a few turns? Any ideas folks? Also any ideas where to get such screws in small quantity in the UK/EU?
Thanks in advance
I have a Calrad FK12 arm which I want to get running as it is cute and I've a VR11 gathering dust.
The arm is Japanese from turn of the 60s and has a non-standard headshell. The machine screws that attach the cartridge appear to be 1/4" long, 3/32" diameter, with a 46tpi gauge. I need longer screws as the headshell sides interfere with the cartridge and it needs a spacer, but can't find this diameter with this pitch, the closest seems to be 3-48 unc. Would this work if only screwed in a few turns? Any ideas folks? Also any ideas where to get such screws in small quantity in the UK/EU?
Thanks in advance
3/32" 48tpi is a BSW thread.(2.38mm diameter) Your 3-48 UNC is 2.5mm diameter.
These guys are good for small qtys and obscure fixings
Thread Data
These guys are good for small qtys and obscure fixings
Thread Data
Thanks for the replies. I'm not up on screw thread standards but it certainly doesn't fit any of the metric pitches on my gauge., but does fit the 46tpi. The 'brochure' which is wrong in an alarming number of areas (arm length for starters ��😉 has all measurements in inches FWIW.
M2.5 is 0.45mm pitch, about 56 tpi, so it definitely isn't metric.
Normally headshell screws and nuts are free (not captive), so you can just replace both with whatever you want, and it sounds like M2.5 would fit.
Normally headshell screws and nuts are free (not captive), so you can just replace both with whatever you want, and it sounds like M2.5 would fit.
Thanks for the reply. This tonearm is not normal! The screws go into sockets in the headshell so I have no option but to use correct bolts. I will investigate the Whitworth pitch next and report back.
Are these Whit or BA/BSF threads?
my money is on 6BA
I may even have a handful of 1/4"x 6BA in the shed, but its absolutely torrential outside right now!
my money is on 6BA
I may even have a handful of 1/4"x 6BA in the shed, but its absolutely torrential outside right now!
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Well little help from my end, they are 2.4mm wide including thread, or about 95/1000" according to my calipers. My Whitworth gauge is too coarse and I haven't got a BA one so I can't check, but what I can say is the threads fit perfectly into a 46tpi gauge on the tool marked V-U-Amer-NAT, with 4-84 underneath and not into my metric gauge (which are fine enough). These are not expensive gauges however ...
In case it helps, these are as good as I can do... View attachment 784894
Edit: It crosses my mind that whilst the thread might work well enough 6BA are too thick for the job I believe, 0.11" against 0.098?
Edit: It crosses my mind that whilst the thread might work well enough 6BA are too thick for the job I believe, 0.11" against 0.098?
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You've only got 5 threads engaged in the thread gauge, so for 48TPI vs 46TPI you'd only be 1/5 of a thread off. My bet is 3/32" Whitworth.
(Note also how the threads look "sharper" than normal. Whitworth is a 55º threadform instead of 60º for metric or UNF/UNC. Although BA is even narrower at 47.5º....)
(Note also how the threads look "sharper" than normal. Whitworth is a 55º threadform instead of 60º for metric or UNF/UNC. Although BA is even narrower at 47.5º....)
Thanks, you look to have nailed it there. Now I can't find any 3/32 Whitworth pan head screws for sale, seem to start at 1/4" boo hoo! Any good tips guys, and thanks for the help everyone, fantastic response!
I was going to suggest drilling the existing holes for M2.5x.45 Heli-coils, but the kits are over $140 USD, so maybe that's not such a great idea.
jeff
jeff
They are brass inserts into? Bakelite?
I don't trust myself to do anything beneficial there. But I do have a very nice pillar drill so happy to try if given the baby steps first.
I don't trust myself to do anything beneficial there. But I do have a very nice pillar drill so happy to try if given the baby steps first.
Bakelite of that age is going to be extremely brittle. The brass inserts will be reasonably soft, though, so you could tap them out to UNC 3-48 (with a bottoming tap).
Except I can't get the screws. I'd tap them to something easy to get though, a metric size I suppose.
Thank you,
Had a look, I will explore properly tomorrow, it seems one will, one won't sell to UK, others probably will.
Had a look, I will explore properly tomorrow, it seems one will, one won't sell to UK, others probably will.
And if you consult these people?
There is a thread on this same tonearm ....🙂
https://www.lencoheaven.net/forum/index.php?PHPSESSID=vke93293hbcbjomosgbj8o7pa6&topic=24915.15
Or in the Vinyl Engine forum :
Vinyl Engine -Index page
There is a thread on this same tonearm ....🙂
https://www.lencoheaven.net/forum/index.php?PHPSESSID=vke93293hbcbjomosgbj8o7pa6&topic=24915.15
Or in the Vinyl Engine forum :
Vinyl Engine -Index page
That is now my tonearm, I think the owner at the time decided to go in a different direction and sold it. It's been sitting around for a while, approximately 60 years as its essentially new in its box, so time to do something with it!
I have located some 3-48 UNC stainless from Accu group UK, I will try them, the BSW seem to be a little 'niche' 🙁, not having any luck with that. Hey ho, onwards and upwards
I have located some 3-48 UNC stainless from Accu group UK, I will try them, the BSW seem to be a little 'niche' 🙁, not having any luck with that. Hey ho, onwards and upwards