Machine Screw Selection Guide
Understanding the different types of machine screws and their uses is key when selecting the right screw for the job. The chart below is meant to help understand the differences and common features of our machine screws.
Common Features of Machine Screws
| Machine Screws |  Flat Slotted Machine Screws |
 Flat Phillips Machine Screws |
 Pan Phillips Machine Screws |
 Round Combo Machine Screws |
 Round Slotted Machine Screws |
 Flat Phillips Undercut Machine Screws |
 Hex Washer Unslotted Machine Screws |
 Hex Head Serrated Flange Screws |
 One-Way Tamper-Resistant Machine Screws |
 Pin-In-Hex Socket Tamper-Resistant Machine Screws |
 Trident Tamper-Resistant Machine Screws |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Description | Flat-slotted machine screws have a cone-shaped depression underneath the head, which creates a flat surface. Slotted screws have a basic slot that accommodates a flat-bladed screwdriver. Flat-slotted machine screws are designed to be seated in countersunk holes and align flush with the surface of the assembly when installed. | Flat Philips machine screws have a cone-shaped depression beneath the head, and the top of the head is flat. Flat Philips machine screws are designed to be low-profile. The countersunk head works well in applications requiring a strong fastener with a flush mount. | Pan head machine screws are slightly rounded with short vertical sides. Pan head machine screws achieve a neat, finished look on metal applications. | Round Combo Head Machine Screws are an incredibly versatile fastener type that is widely used by electricians and contractors. Round Combo Head Machine Screw features a combination drive that accepts both Phillips and slotted drivers and are often used with a hex nuts. |
Round Slotted Machine Screws are often used with nuts as well as driven into tapped holes. Round Slotted Machine Screws are good for low-torque low-speed applications when being fastening with a flathead screwdriver. | Flat Phillips Undercut Machine Screws have a flat bottom underneath the head, creating a flat surface Flat Phillips Undercut Machine Screws are designed to be seated in countersunk holes and align flush with the surface of the assembly when installed. | Hex Washer Unslotted Machine Screws have a built-in washer at the screw head. This allows for the distribution of weight and load over a wider area and hex cap screws allow for greater torque than that of traditional screws with a circular head. | Hex Head Serrated Flange Screws have a built-in flange (integral) lock washer. The serrations on the hex head machine screw prevent the bolt from back spinning from vibration, and the serrations lock the bolt in place when torqued to the correct specifications. | One-Way Tamper-Resistant Machine Screws are slotted screws and can be installed with a standard slotted screwdriver. However, removing them with the proper one-way removal tool is easier. Half of each side of the slot is smoothed down during manufacture. | Pin-In-Hex Socket Screws feature a small metal post in the middle of the screw head that prevents a standard hex driver from engaging. Pin-In-Hex Socket screws can only be installed with the correct security bit or key. | Trident Tamper-Resistant Machine Screws offer a unique head design that makes removal extremely difficult without the correct security socket and tool. The Trident head is conically shaped with three notches around the perimeter. |
| Material | Carbon Steel | Carbon Steel, Stainless Steel & Steel | Carbon Steel & Stainless Steel | Carbon Steel | Stainless Steel | Stainless Steel | Stainless Steel | Steel | Case Hardened Steel & Stainless Steel | Stainless Steel | Case Harden Steel |
| Diameter | #6, #8, #10, #12 & 1/4" | #6, #8, #10, #12 & 1/4" | #6, #8, #10 & 1/4" | #6, #8, #10, 1/4" & 3/8" | #6, #8, #10, #12 & 1/4" | #0, #2, #3, #4 & #5 | #4, #6, #8, #10, & 1/4" | 1/4", 5/16", 3/8" & 1/2" | #4, #6, #8, #10, #12, 1/4" & 5/16" | #4, #6, #8, #10, & #12 | #6, #8, #10, 1/4" & 3/8" |
| Length | 1/4", 3/8", 1/2", 5/8" & 3/4" | 3/16", 1/4", 3/8", 1/2" & 5/8" | 3/16", 1/4", 3/8", 1/2" & 5/8" | 1/4", 3/8", 1/2", 5/8" & 3/4" | 3/32", 1/8", 5/32", 3/16" & 1/4" | 1/4", 5/16", 3/8", 1/2" & 5/8" | 3/8", 1/2", 5/8",3/4", 1", 1-1/4", 1-1/2", 1-3/4", 2", 2-1/2" & 3" | 3/16" thru 3" |
6mm ,thru 60mm 1/4" thru 2-1/4" |
3/8", 1/2", 5/8",3/4" & 1" | |
| Thread Type | Coarse and Fine | Coarse and Fine | Coarse and Fine | Coarse and Fine | Coarse and Fine | Coarse and Fine | Coarse and Fine | – | – | ||
| TPI | 13, 16, 20, 24 & 32 | 18, 20, 24 & 32 | 20, 24 & 32 | 16, 20, 24 & 32 | 16, 20, 24 & 32 | 16, 18, 20, 24 & 32 | 16, 18, 20, 24 & 32 | 13, 16, 18 &20 | 18, 20, 24, 32 & 40 | 16, 18, 20, 24 & 32 | 18, 20, 24 & 32 |
| Security | No | No | No | No | No | No | No | No | Yes | Yes | Yes |
| Material Note | 18-8 Stainless Steel | Zinc Finish | 18-8 Stainless Steel | 18-8 Stainless Steel | 18-8 Stainless Steel | Zinc Finish | 18-8 Stainless Steel | Zinc Finish | |||
| Technical Specifcations | – | – | – | – |  |
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