For furniture, choose a screw long enough to grip well into the second piece without poking through, thick enough to hold, and with a head and finish that suit the look. Always drill a pilot hole and follow the screw maker’s guidance. The sections below cover each factor.
Length and Diameter
A common rule of thumb is that about two thirds of the screw should sit in the receiving piece. Thicker boards allow longer screws. The diameter, often called the gauge, affects holding power and the risk of splitting. Thin or brittle wood needs a smaller gauge.
Head and Drive Styles
- Flat head: sits flush when countersunk, good for visible surfaces.
- Pan or round head: sits on top, used with washers or in hidden areas.
- Trim head: small head that leaves a tiny hole for filling.
- Drive shape: square or six-point recesses resist slipping more than slotted ones, so follow the maker’s recommended driver.
Decision Table
| Factor | Why it matters | What to check |
|---|---|---|
| Length | Grip without breaking through | Combined thickness of the pieces |
| Gauge | Strength versus splitting | Wood species and board width |
| Thread | Affects pull and speed of driving | Coarse for softwood, fine for hardwood, per maker advice |
| Material and coating | Resists rust and staining | Indoor or outdoor use |
| Head type | Look and clearance | Visible or hidden location |
Steps Before You Drive
- Measure the thickness of both pieces and decide on a screw length.
- Choose a pilot bit slightly narrower than the screw core, and a clearance hole in the top piece if the maker advises one.
- Mark positions away from edges and ends to lower the risk of splits.
- Add a countersink for flat heads so they sit flush.
- Drive the screw by hand with a well-fitted driver, stopping when the head seats. Over-tightening can strip the hole.
- If the wood is dense, a little wax on the threads can ease driving.
Care and Storage
Keep screws sorted in labeled containers by length and head type. Mixed bins lead to wrong choices and slow work. Store them dry to limit rust, and set aside any with chewed heads. When you buy, get a few more than you think you need, since a few will be lost or damaged during fitting.
It also helps to keep the screw maker’s chart nearby. Charts list the pilot hole sizes for common woods, and they save guesswork when you switch between softwood and hardwood. When in doubt, test on an offcut before you drive a screw into a finished part.
FAQ
Do I always need a pilot hole?
Hardwoods and areas near edges almost always benefit from one. Softwoods may not, but a pilot hole is a careful habit.
Can I reuse screws?
If they are straight and unbent, often yes. Replace any with damaged heads or threads.
The Short Version
Match length, gauge, and head style to the wood and the look. Make a pilot hole every time and tighten by hand until the head seats. Follow the screw maker’s instructions.