Gentlemen
I have just bought a '16' insert size Stellram threading toolholder from an Ebay vendor, with 13 assorted inserts thrown in. I can identify 11 of them readily, but two puzzle me (and also the bloke who sold them, when I asked him today).
Two are marked 18 N 16 ER, they have a sharp, Vee profile with no radius at crest or root.
From what I have learned recently, I would expect the 18 to mean 18tpi, full profile type, metric full profiles quote a pitch here like 1.25: N - don't know, but if it was UN then that would be Unified at 60', W is Whitworth at
55' etc, 16 is the size of the insert and the ER is external, right hand.I'm aware of the partial profile type which will be best for me in the long term, but the inserts were better than free compared to a JL toolholder price and the 20UN insert I wanted for a job in hand was included.
It's not the end of the world, but does anyone know what they are?
Steve (Sheffield)