#8 screws that come with drawers slides are usually not the right screw. What’s so special about a good #8 wood screw? Well, it needs aggressive threads, a large truss head and a well made head for driving.
Otherwise, your perfect drawer adjustment will come out of alignment over normal use of the drawer. And nobody wants to install a drawer slide twice.
Consider these factors:
- Most cabinet sides are made from MDF (medium density fiberboard)
- Shallow threaded screws will strip easily in MDF and fail over time
- Aggressive threads, like found in the Rok #8 screws, will grab and hold in MDF and standard plywoods
And I’ve installed a lot of drawers. Bad screws are a top 3 frustration.
Contents
What is the diameter of a #8 screw?
- #6 screws: .138″ or ~9/64″ diameter
- #7 screws: .151″ or ~5/32″ diameter
- #8 screws: .164″ or ~5/32″ diameter
- #9 screws: .177″ or 11/64″ diameter
- #10 screws: .190″ or 3/16″ diameter
For a complete rundown of sizings check out this handy guide at Bolt Depot.
So what makes for variations in #8 screws?
Especially if they are all the same diameter, right?
The answer is the size of the shaft, which is the core of the screw where the threads terminate, and the cut of the threads themselves.
Consider:
- A large shaft will result in a shallow thread (less gripping area)
- While on the other hand, a thin shaft will allow for a deep thread
- And a deep thread will have more surface area exposed against the material it is inserted into
Now most #8 screws for drawers are too short to have advanced features like what GRK put into their cabinet screws, but the thin shaft and deep thread offer a distinct advantage in materials like MDF that are relatively weak.
But do I need to drill a pilot hole?
This isn’t a yes or no question, unfortunately. So here’s a starting point, and then make sure to test out your hardwoods and softwoods with the #8 screws you are using:
- For #8 screws under 3/4″ most can go into softwood, plywood and MDF without a pilot hole.
- However for any screws in hardwood a pilot hole is needed.
- All screws 3/4″ and longer that do not have a self-tapping design should have a pilot hole to prevent splitting of the wood
Failing to drill a pilot hole when needed can either split the wood or break the screw. And both are bad when it comes to needing to extract the screw or use the now damaged wood to hold a screw.
3 Reasons Screws Matter in Drawer Installation
Not everyone likes to plan the details, but if you’re willing to invest a few minutes in planning and buying the right screws it’s worth it.
Especially if your project involves a retrofit where you’ll be working in a cabinet with a counter already installed. Due to limited space and visibility the screw really matters.
Reason #1: Prevent stripping
Well hey, not that kind of stripping.
But instead think about deep threads vs. shallow threads and an analogy like trying to pull a heavy object across the floor and your fingers are the “threads”.
Would you grab the object with just the first joint of your fingers (shallow) or all three joints (deep)? Correct, you’d want all the leverage and holding force you could muster. Or your fingers might slip off.
So the same goes with drawers, which can hold upwards of 100 pounds with just 4-6 screws holding the weight.
Reason #2: Long term holding power
Maybe you enjoy repairing things, but I sure don’t.
15 years ago I built and installed 20+ drawers in my current kitchen. And I haven’t adjusted a single one because I used the right screws.
I did, however, use the factory screws in a cherry dresser with side mount ball bearing screws. And guess what? Yep, they have stripped and loosened as the 50 pound drawers have worked against the screw year over year.
Reason #3: Added safety
In my kitchen I have a rather large drawer in the bottom stack of cabinets. And it is stuffed full of kids coloring books, markers and I don’t know what else.
And watching my kids as they aged through 18 months up to 5 years lean on this drawer always made me nervous. While it was secured in with the right screws and well adjusted drawer slides (and never failed) safety is certainly something to consider.
Due to many drawers featuring up to 100 pound load capacity with full extensions just think of the force on that rear mounting bracket and the 2 screws typically used to hold it in.
Frequently Asked Questions for #8 Screws
What does a #8 screw mean?
The #8 refers to the overall outer diameter of the screw threads. For a #8 screw the diameter is 0.164″ or about 5/32″ of an inch. For reference, a #7 screw is smaller while a #9 screw is larger in overall diameter.
What size hole do you drill for a #8 screw?
That answer depends on the thread depth. The best way to determine the right size drill bit is find a drill bit that is close to the shaft size, then hold it up to a light. If you can see a lot of the drill bit it’s too big. If you can’t see the drill bit it might be too small. However, if the shaft (minus threads) and the drill bit are about the same size then you have the right size. Because thread differs between screws there is no single right size.
Which is bigger a #8 or a #10 screw?
A #10 screw is a larger diameter (or “bigger”) than a #8 screw. As the # increases the screws overall outer thread diameter increases.
Summary
Who thought there could be so much to a #8 screw? For more reading check out our articles on the best drawer slides.
