Round Head Machine Screws, UNC (Slotted and Phillips) are used primarily for inch round head machine screws with UNC thread, slotted or Phillips. This page lists the industries and assemblies where they are specified, the selection criteria that matter for each application, installation practice, and the cases where a different fastener type is the correct choice. Parts are supplied to ASME B18.6.3. Stocked across roughly 1 to 12, they cover general to heavy-duty work.
Typical Applications for Round Head Machine Screws, UNC (Slotted and Phillips)
The most common settings where these are specified:
- Restoration: vintage equipment.
- Electrical: terminals.
- Hardware: hinges.
- Machinery: covers.
How to Specify Round Head Machine Screws, UNC (Slotted and Phillips) for Your Application
- Size: Match the nominal size to the mating thread or hole. This product spans 1–12; check the full table below for the exact dimensions of each size.
- Drive & head: Pick the drive (socket, cross, slot) and head style for the tool access and seating surface; a recessed drive resists cam-out under power tools.
- Environment: For damp, coastal or chemical exposure prefer A4/316 stainless or a suitable coating; indoors, plated steel or A2 is usually sufficient.
- Standard: This product is supplied to ASME B18.6.3. Quoting the standard on your order guarantees interchangeable dimensions between suppliers.
Installation & Assembly Practice
- Match the driver exactly to the recess (PH ≠ PZ; hex key sizes per ISO 2936) and keep the tool axial — side load is the main cause of stripped drives.
- In tapped holes, engage a thread length of at least 1× the nominal diameter in steel, 2× in aluminum.
- Set power tools to a torque that seats the head without embedding it into the mating surface.
Common Selection Mistakes with Round Head Machine Screws, UNC (Slotted and Phillips)
- Under-sizing the drive for the installation torque — a small recess at high torque strips before the screw is seated.
- Using a countersunk head in thin sheet where the countersink removes most of the load-bearing material.
- Specifying stainless in high-strength duty: A2-70 is roughly class 7 steel, not a 10.9 substitute.
Where Round Head Machine Screws, UNC (Slotted and Phillips) Are Not the Right Choice
Not for high-preload structural joints (use a property-class bolt and nut), and not in thin sheet where a self-drilling or self-tapping type suits better.
Custom manufacturing · Made to drawing
Need a round head machine screws, UNC (slotted and phillips) outside the standard range?
Lengths and thread lengths outside the standard table are the commonest request, followed by a drive the standard does not offer and a head marked with your own part number. Made by cold heading or warm forging.
Minimum order from 2,000 pieces; samples within 7 days of drawing approval.
