Why Screw Machining?

Tolerances vary depending on the type and grade of the raw material we are machining, the material that we make the tools out of and the machine we use to make a particular part. For example, on certain features utilizing machine-grade steels, we can achieve tolerances in the tenths of an inch (0.0001”).

Tighter tolerances can also be achieved using secondary operations, such as grinding, honing and lapping. A detailed answer to this question is difficult to provide and it is best to answer this question on a part-by-part basis in an engineering review.​

​Screw machines are best used for parts with batch volumes of 2,000 pieces or more. Part geometries that are best for screw machines are parts with features that are put onto the part in the same plane, or perpendicular to the part.

When screw machining, the bar is turning and the tools are stationary, so certain features are achieved with secondary machining or the part can be machined completely on our rotary transfer equipment thus eliminating the secondary operations.

CNC describes a lot of different machine types, the common denominator being that there is a computer that controls the machine’s axes. CNC lathes are typically faster to changeover than screw machines, but depending on the features of a part, may have longer cycle times to complete the machining than a multi spindle screw machine.

Seward Screw also has CNC multi spindle screw machines. For example a machine could combine six spindles with three axis of machine movement so it is essentially an 18 axis lathe providing screw machine production throughput with tighter tolerances.

A rotary transfer machine makes parts with multiple features. The bar is cut off and the starting piece of material is held in one of twelve collets and as the machine indexes, the part travels between each station (1 through 12 Stations).

Each of the stations in a rotary transfer machine has an independently controlled motor and feed system, making it possible to do many features. The rotary transfer machines at Seward Screw, LLC have 10 or 12 stations. These machines typically require higher part volumes with multiple features.​

Since we have so many different types of machines, the minimum runs vary by the type of machine we have. We are willing to vary the run quantities to what makes sense with the individual customer’s needs, and the quoted prices reflect that.

Low and medium carbon steels, alloy steels, stainless steels, copper and copper alloys such as brass and bronze, aluminum. These can be in bar or tube form.​ We can also machine cold-headed blanks from our sister company Slidematic Precision Components.

Yes, we do. In fact, we have had a lot of success with engineering assistance for many of our customers, providing them with a totally optimized production process.

Screws can be made on screw machines, but common screws and bolts are typically made on much more efficient machines like headers and threaders. Our company is named for the type of machines we have but we make very few parts that even look like screws.​