August 2013 Machining Tip



Finished Parts

Depending on the application of your part, there may be reasons to care about the finish of a machined part. Visible parts may have to be finished to meet cosmetic requirements. Internal parts—particularly moving parts—may require a specific finish in order to function correctly. At Firstcut, if your machined part is plastic, the choice of finish is simple: all of our machined plastic parts are left as-milled (see Figure 1), which typically means they show visible tool marks. Some metal parts, on the other hand, allow more choice.


  • Soft metals—brass, copper, and aluminium—can be left as-milled or can be lightly bead blasted (see Figure 2), leaving a fine matte finish. Note that this is a manual process, so variation should be expected both on areas of a single part and between parts.
  • Hard metals, both steel and stainless steel, can be left as-milled (see Figure 3). They can also be de-burred with a light bead blast (see Figure 4), which removes metal slivers and sharp or particularly rough areas.
Figure 1: Plastic parts are left as-milled (leaves visible tool marks).

Figure 1: Plastic parts are left as-milled (leaves visible tool marks).

Figure 2: Aluminum part with bead blasted finish, which gives parts a fine matte appearance.

Figure 2: Aluminum part with bead blasted finish, which gives parts a fine matte appearance.

Figure 3: Hard metal part shown as-milled which leaves visible tool marks as well as potentially sharp edges or burrs.

Figure 3: Hard metal part shown as-milled which leaves visible tool marks as well as potentially sharp edges or burrs.

Figure 4: Hard metal part that has been de-burred with light bead blast which removes any metal slivers or rough/sharp areas that may be left as a result of the CNC milling process.

Figure 4: Hard metal part that has been de-burred with light bead blast which removes any metal slivers or rough/sharp areas that may be left as a result of the CNC milling process.


Metal-class materials and finish selections are available when you select your options on your FirstQuote®.