Strange thread

Volker Borchert · 2015-07-15T21:24:49+00:00

In the replacement steering knuckle for an IHC 453 there are two threaded holes whose thread I can't make out: inner diameter about 10.25 mm and a pitch of 13 TPI [1]. WTF is this? It's obviously neither M12(x1,75) nor UNC1/2x13... Is there an UNC15/32x13? Or even a cross-over 12mmx13TPI? Any hints appreciated [2]. Volker [1] I screwed in a 11mm square wood rod to get that accurately. [2] Yes, I'll contact the vendor. But, I prefer not to appear totally ignorant on the phone ;-)