The Acme thread form has a 29?thread angle with a thread height half of the pitch; the apex ( or " crest " ) and valley ( or " root " ) are flat.
12.
The line of General Purpose ( GP ) Acme threads ( ASME / ANSI B1.5-1988 ) are not designed to sustain external radial loads and both the nut and bolt are, ideally, independently supported, the nut by a linear guide and the screw by shaft bearings.
13.
This adds the requirement that the sum of the allowances and tolerances on the pitch diameters ( PD ); the drawback is that, for a given amount of end play ( axial clearance, due solely to PD deviations ), closer tolerances and cleaner work environment are necessitated in the application of a centralizing Acme thread.
