Knurled Thumb Screws Buyer’s Guide

6 Things to Know When Buying Knurled Thumb Screws


  1. What is a Knurled Thumb Screw? 

Knurled Thumb Screws are generally classified as part of the electronic hardware or precision fastener family and are not governed by IFI, ANSI or ASME standards. They are solid one piece screws with a cylindrically shaped oversized knurled head, a fully threaded shank construction and a blunt machine screw style end. They are used in applications where periodic manual adjustment is required and finger pressure can supply sufficient tightening torque.

Knurled Thumb Screw

Knurled Thumb Screw with Washer Face

  1. What materials and sizes are available?

Knurled Thumb Screws are readily available off the shelf in type 18-8/303 stainless steel and Aluminum. Some manufacturers stock knurled thumb screws in brass or other materials. Parts are typically supplied without any coating or finish.

Standard stock sizes for the thread diameter are Inch from 4-40 to 1/4-20 with standard lengths up 1” depending upon the manufacturer.

316 stainless steel, alloy and other exotic materials, and special diameters and lengths are available in certain sizes and/or for special order and usually involve a lead time.

  1. What information do I need for ordering?

The easiest way to order is by manufacturer part number. If you don’t have one, you’ll need to specify thread diameter, thread length, head style and material. For example: 6-32 x 3/8″ Knurled Thumb Screws with a Washer Face in Stainless Steel 18-8 is a popular Thumb screw.

Typical head styles are a modified fillister with a flat top where the head diameter is about twice the head height and does not need to be specified. Low head fillisters are available in certain sizes.

  1. What are some of the popular Fastener Brands with Functional Equivalents?

Popular OEM fastener brands include: Amatom, Cambion, Concord, Globe, HH Smith, Keystone, Lyn-tron, Misumi, Pic Design, RAF, and WM Berg. A comprehensive selection of Knurled Thumb Screws is also offered by McMaster-Carr, MSC Industrial and Grainger.

One surefire way to save money and shorten delivery time is to cross the OEM brand part on your bill of materials to a functional equivalent.

Let’s take the above example of a 6-32 x 3/8″ Knurled Thumb Screws with a Washer Face in Stainless Steel 18-8 is a popular Thumb screw.

This part is offered by the Five brands (yes Five!!) listed below under the following part numbers:

  • Grainger 2KB93
  • Lyn-tron SS7603
  • RAF 7103-SS-0
  • Mcmaster-Carr 99607A116
  • Unicorp THS1004-M07-F16

Each manufacturer has a different price point, but the general physical and chemical dimensions make them functional equivalents or Brand alternatives.

  1. Helpful Hints about Categories of Thumb Screws

There are 2 distinct Thumb Screws categories:

1) Knurled Thumb screws, which are covered here, are part of the precision screw family. They are made 2 ways: Washer face/flared collar or plain/shoulderless. They are typically stocked in aluminum and stainless steel. Other options such as narrow, high profile, slotted may also be available in certain sizes.

2) Type A and Type B Spade style thumb screws are part of the Industrial fastener family per ASME B18.6.8, along with Wing screws. Spade style thumb screws may be available in steel and in diameters up to 1/2”.

  1. What level of certification is required?

Generally, a Certificate of Conformance or a COC is sufficient for your customer. Full certification with material certs and test reports are often available for USA-made and Mil-Spec parts for a fee.

Knurled Thumb Screws at MF Supply

We offer:

  • The full range of commercial and Mil-Spec parts, including parts that are DFARS and RoHS compliant.
  • Brand names and generic equivalents.
  • Custom made parts per print in non-standard and exotic materials and finishes.
  • Inch and metric sizes.

For more detailed information about Knurled Thumb Screws, visit our website. And if you don’t see it listed, as always, ask us. “Finding the right screw for you” is our tag line after all!

For more than 40 years, MF Supply has helped American manufacturers streamline operations, saving them time and money with our sourcing expertise and unique supply chain strategies. We are a WBE/WOSB certified stocking distributor of fasteners and electronic components.

We work with the best established factories in the United States and DFARS-certified countries, and stock a huge inventory including all major brands and equivalents. MF Supply provides solutions including: same-day drop ship direct from the factory; custom sizes, materials and plating options; and DFARS parts with full paperwork and Certificates of Conformance.

We creatively solve common problems including hard-to-find parts and long lead times. Our sourcing and reworking expertise includes fast turnaround for modification of existing parts, hard to find standards and specials, special threads, non-standard diameters and lengths, exotic materials, special platings and short runs. We provide functional equivalents to expensive brand name fasteners and help our customers save money while reducing lead times.

What the heck are Standoffs and Spacers?

Volume 9
August 20, 2014

What the heck are Standoffs and Spacers?

We close out the summer of 2014 by introducing you to Standoffs and Spacers. According to the dictionary, a Standoff is defined as “a stalemate or a deadlock between two equally matched opponents.” In the world of manufacturing and assemblies, Standoffs, and their cousin the Spacer, have a different meaning which we will uncover today.

What are Standoffs and Spacers?
Often classified as Electronic Hardware, or Panel Hardware, Standoffs are hex or round shaped fasteners which have a body and two threaded ends. The threaded ends can either be an internally threaded opening (female) or an externally threaded post (male). They are commonly used to mechanically support and electrically connect and position components within assemblies.

Spacers are similar to Standoffs, however, Standoffs are threaded on both ends, and Spacers are unthreaded with an inside clearance hole.

Who uses Standoffs and Spacers?
Look inside an assembled circuit board, and you will be greeted by Standoffs and Spacers, because in the world of Electronic Hardware, they are the standard for connecting and mounting circuit boards, panels, doors, and gears. Both are commonly used to properly position parts within an assembly, to reduce component contact, to elevate stacked sections, to ensure enough room for heat to dissipate, and to separate or create space between two objects. These guys are workhorses!

What do I need to consider when selecting Standoffs and Spacers?
Standoffs and Spacers are available in a variety of styles based on four main attributes: 1) shape 2) outer diameter of the body 3) body length and 4) thread size or clearance hole. Standoffs have a fifth attribute, thread type (we like to call it gender), as defined below.

Standoffs and Spacers can be hex, round or square shaped. The most common diameter of the body is ¼, but many other sizes are available. Standard body lengths range from ¼ x 2″. Clearance holes and thread generally range from #2 through ¼. Special lengths and sizes are available – just ask!

Standoffs come in three main styles (genders):
1) Female-female: can be fully threaded or partially threaded on each end.
2) Male-female: have internal female threads on one end and male threads on the other. Threads are generally the same size.
3) Male-male: have external threads on both ends which may be of differing thread size.

What Materials are available?
Common materials include aluminum, brass, plastic/nylon, steel, and stainless steel. Common platings include clear anodized, nickel, gold iridite and zinc plated. There are over 20 common plating’s available! Here are some of the most common materials:

Aluminum is popular because of its ratio of weight to strength. It is light, non-magnetic, performs well in severe temperatures, and has insulating properties.

Brass is used in making high-quality standoffs. It is conductive, resists corrosion, and is non-magnetic. It is costlier and heavier than aluminum and is usually plated zinc or nickel. It can be soldered for grounding.

18-8 Stainless Steel is strong, conductive, and nonmagnetic, this stainless steel offers excellent corrosion resistance.
Steel is used for its strength, but it is heavier than aluminum and does not resist corrosion like Stainless steel, aluminum or brass. It is often zinc plated for added corrosion resistance.

Nylon 6/6 is superlight, nonconductive, and resistant to chemicals and solvents. Nylon absorbs moisture, which can affect dimensions and other properties.

Lesson Learned, considerations when selecting and using Standoffs and Spacers

  • Standoffs are sometimes referred to by their brand names, which can often be substituted by generic equivalents. Popular brands include: Amatom, Concord, Globe, H.H. Smith, Lyn-tron, Microplastics, Keystone, Pem, RAF, Unicorp.
  • To measure a Standoff or Spacer, measure the outside diameter of the body, the length of the body and the thread size. Determine if the standoff is a female-female, male-female or male-male. A typical Standoff might measure as follows: 1/4 hex X 1/2 long X 8-32 thread male-female aluminum standoff. This exact standoff is made and branded by at least 10 manufacturers. Note: the length of the male threaded post is standard and is not called out.
  • Standoffs and Spacers sometimes show up under their Mil-spec numbers, which can be crossed to commercial equivalents. Some common Mil-spec series include NAS42, NAS43, NAS61, NAS1056, NAS1057, NAS1829, NAS1830, NAS1831.

Standoffs and Spacers at MF Supply

Here at MF Supply, we supply some of the most common and unusual Standoffs and Spacers, including:

  • The full range of commercial and mil-spec parts in both inch and metric.
  • Specials sizes, materials and platings. Just try to stump us!
  • We are authorized distributors for Amatom, Concord, Lyn-tron, Microplastics and RAF and offer the full range of brand names and equivalents.

For more detailed information, visit us at

And if you don’t see it listed, as always, ask us. Finding the right screw for you is our tag line after all!