Match Masking Caps to Common Threaded Studs
The correct caps for SAE/UNC/metric threads - see chart below
Engineering drawings typically call for masking threaded pins and features to protect them during finishing processes. This protects them from powder coating, paint, anodizing, plating, ecoating and other metal finishing processes so the threads stay clean for when a nut is added later.
The core challenge is determining the correct cap size for a given thread.
Cap Types Available
Standard and Expandable Silicone Caps
- SC line: Straight wall caps for common thread sizes
- SCE line: Expandable caps featuring an internal rib design that allows a single cap to fit multiple thread diameters, reducing inventory
Silicone Caps with Flange
- VFC line: When masking these features, a fast and easy way to accomplish this is with a flange cap that creates metal-to-metal contact points for electrical grounding
Thread-to-Cap Matching Chart
| Thread Size | Straight-Wall Caps | Expandable Cap | Cap with Flange |
|---|---|---|---|
| 4-40 | SC100-0500, SC100 | — | VFC100-0500 |
| M3 | SC100-0500, SC100 | — | VFC100-0500 |
| 6-32 | SC125-0500, SC125, SC125-1500 | SCE-118-236 | VFC125-0500 |
| M4-0.7 | SC148-0500, SC148-0750, SC148 | SCE-118-236 | VFC146-0472 |
| 8-32 | SC156-0500, SC156, SC156-1500 | SCE-118-236 | VFC156-0500 |
| M5-0.8 | SC180 | SCE-118-236 | VFC180-0600 |
| 10-24 | SC172-0500, SC172, SC172-1500 | SCE-118-236 | VFC172-0500 |
| M6-1.0 | SC223-0500, SC223-1000, SC223 | SCE-118-236 | VFC220-0590, VFC220-0787, VFC223-0720 |
| 1/4-20 | SC234-0500, SC234, SC234-1500 | SCE-236-354 | VFC240-0500 |
| 5/16-18 | SC281, SC281-2000 | SCE-236-354 | — |
| M8-1.25 | SC295-0500, SC295-125, SC295 | SCE-236-354 | VFC295-1000 (N/S) |
| 3/8-16 | SC355 | SCE-236-354 | VFC350-740 (N/S) |
| M10-1.5 | SC375-0750, SC375, SC375-1500 | SCE-354-472 | VFC376-0825 |
| M12-1.75 | SC456-0500, SC456-1000, SC456 | SCE-354-472 | VFC460-700 (N/S) |
| 1/2-13 | SC468, SC480 | SCE-472-591 | — |
(N/S) = Non-stock items, available with no tooling cost
Measurement Instructions
If you don’t know the thread size but can measure the diameter across the threads with calipers, use that dimension to select your cap. For a snug fit that won’t fall off during powder coating, choose a cap with an inside diameter (ID) that is slightly smaller (approx. 2% to 5%) than your stud diameter.
Frequently Asked Questions
Can these caps withstand powder coating oven temperatures?
Yes, our silicone caps are rated to withstand up to 500°F (260°C) and can often handle intermittent spikes up to 600°F.
Are these masking caps reusable?
Absolutely. Silicone caps are highly durable and can be reused multiple times. Routine cleaning of powder buildup is recommended.
How do I create a grounding area on a threaded stud?
Use our VFC line of flange caps. The flange creates a metal-to-metal contact area around the stud for electrical grounding during the coating process.
What is the benefit of an expandable cap?
Expandable caps feature an internal rib design allowing one cap to fit multiple thread diameters. This is beneficial for reducing inventory — fewer cap sizes to stock while still covering a wide range of threads.
Will these caps work in plating or anodizing tanks?
Yes, silicone has excellent chemical resistance. They are ideal for Type II and Type III anodizing, as well as most plating baths including nickel and chrome.
What if my stud is longer than your standard caps?
For studs longer than standard caps, we recommend using silicone tubing cut to length.
Email us at info@viadon.com or give us a call at 866-534-3900 (7:30 am to 4 pm Central Time).