Milling and Grinding Tolerance
In flamecutting and sawcutting of steel plate, we define tolerances
for the dimensions of the cut shape or profile. Squareness of the cut
is also important. Finishing the surface of the part by milling or
grinding brings into play an additional set of definitions, qualities,
and tolerances that vary depending on the application. These are most
commonly spelled out in one of the following ways:
- One side
Clean up only
- Two side (top & bottom)
Clean up only
To finish size
To finish size, and parallel
To size, flat, and parallel
- Four side or Six side
To finish size, parallel, and perpendicular
 It
is important to remember that none of these qualities (clean up, finish
size, flatness, parallel, perpendicular) is ever
assured or
implied by another. For example, it is quite possible to produce a
part to a finish size and parallel, but not flat. Or to produce one
that is to a size, flat, and parallel, but not 100% cleaned-up. Also,
each quality requires different steps and has different costs associated
with it. The more specified, the higher the grinding costs.
Size tolerances
are generally expressed as plus-or-minus (denoted as + / -). Flatness
and parallelism tolerances are defined in terms
of overall allowance. Thus, a part ground to a dimensional tolerance
of +/- 0.003 might have a flat and parallel tolerance of 0.005
|
