Help! Where to get these screws?

Jazid

Member
2009-12-15 7:02 pm
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
 

Jazid

Member
2009-12-15 7:02 pm
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.
 

Jazid

Member
2009-12-15 7:02 pm
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 ...
 

Jazid

Member
2009-12-15 7:02 pm
In case it helps, these are as good as I can do... View attachment 784894 IMG_20190930_193113.jpg IMG_20190930_194457.jpg


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....)
 

Jazid

Member
2009-12-15 7:02 pm
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