Machined Threads in ZA-27 Casting

[toes112]

I'm having trouble holding minor diameter tolerances and major diameter tolerances in a ZA-27 Casting. The casting includes a hole (.349" Min .359" Max" - 3/8" in length) and we are trying to thread the entire length M10 X 1. Using cutting taps and form taps, we struggle to hold standard machinery tolerances. Any background on a type of process that would enable us to hold tolerances consistently?
Ream first to .XXX"?
Cutting tap vs. From Tap?
Any help is appreciated.

 

[MikeHalloran]

Is the hole blind or through?
What's the diameter of the as-cast hole? How much taper?
In what way are you struggling?
How many holes per tap?
Are you using coolant?
What's the casting temperature at the threading station?




Mike Halloran
Pembroke Pines, FL, USA