Technically reviewed by Vincent, Founder at HEXVARO
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Quick answer
Quick answer: self-drilling screw sizes
Choose the gauge for the load, and the drill point for the total steel thickness. A longer drill point is needed for thicker steel.
| Size | Diameter (in) | Diameter (mm) | Inquiry |
|---|---|---|---|
| #8 | 0.164 | 4.2 | Quote this size |
| #10 | 0.190 | 4.8 | Quote this size |
| #12 | 0.216 | 5.5 | Quote this size |
| #14 | 0.250 | 6.3 | Quote this size |
Sourcing these sizes? Hex washer head self-drilling screws Pan and wafer head self-drilling screws
Self-drilling screw diameter chart
#12 and #14 are also called ST 5.5 and ST 6.3 in metric sizing.
| Size | Diameter (in) | Diameter (mm) | Inquiry |
|---|---|---|---|
| #8 | 0.164 | 4.2 | Quote this size |
| #10 | 0.190 | 4.8 | Quote this size |
| #12 | 0.216 | 5.5 | Quote this size |
| #14 | 0.250 | 6.3 | Quote this size |
Drill capacity by size (mm)
These are example maximum steel thicknesses for one maker's type BSD screws, before the thread engages. Capacity changes with thread form and maker, so confirm it for your product.
| Size | Point 2 | Point 3 | Inquiry |
|---|---|---|---|
| #8 | 2.5 | 3.6 | Quote this size |
| #10 | 2.5 | 4.5 | Quote this size |
| #12 | 3.6 | 4.5 | Quote this size |
| #14 | 4.4 | 6.3 | Quote this size |
How to choose a drill point
Published limits vary between makers, so use the list as a guide. Add stacked layers together when you work out the thickness.
- Tek 1: very thin sheet.
- Tek 2: light gauge steel and common cladding work.
- Tek 3: heavier sheet and thin plate.
- Tek 4: heavier plate and purlins.
- Tek 5: thick steel, up to about 12.7 mm on suitable screws.
Point length and thread start
The drill must finish the hole before the thread engages. If the thread reaches the steel too early, the screw can bind or snap. This is why thick steel needs a longer drill point, and why a screw must also suit the fixing's overall length.
Heads, washers and finishes
- Hex washer head with EPDM washer: roofing and cladding.
- Pan or wafer head: steel framing and low-profile fixing.
- Countersunk with wings: wood or board to steel.
- Coating: state the salt spray hours you need, not only the coating name.
What to state in an RFQ
- Gauge, length, head type and drive.
- Drill point and total steel thickness.
- Washer, coating and salt spray target.
- Quantity per size. MOQ is 500 pcs per specification.
Order these sizes from HEXVARO
Send your size list with grade, finish and quantity — we reply within 2 working hours with price, lead time and shipping terms.
- Reply: within 2 working hours
- MOQ: 500 pcs per specification
- Lead time: 10–15 days stock items
- Payment: T/T · L/C · PayPal
- Shipping ports: Tianjin · Ningbo · Shanghai · Shenzhen
- Incoterms: EXW · FOB · CFR · CIF · DAP
- Experience: Founder with 10+ years in the fastener industry
Frequently asked questions
What size is a #12 self-drilling screw?
About 5.5 mm, or 0.216 inches. It is also called ST 5.5.
What size is a #10 self-drilling screw?
About 4.8 mm, or 0.190 inches.
What size is a #14 self-drilling screw?
About 6.3 mm, or 0.250 inches. It is also called ST 6.3.
What is the difference between Tek 3 and Tek 5?
Tek 5 has a longer drill point for much thicker steel. Tek 3 suits sheet and thin plate.
How do I choose a self-drilling screw for stacked sheets?
Add the thickness of all the layers, then choose a drill point with enough capacity for the total.
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