Match Masking Plugs to Common Threaded Holes
The correct plugs for UNC/metric threads - see chart below
A typical call out on engineering drawing is to mask threaded holes. This protects them from powder coating, paint, anodizing, plating, ecoating and other metal finishing processes so the threads stay clean and perhaps provide a good grounding area. But masking those holes presents a challenge: How to mask them effectively? Viadon can help with our wide selection of masking plugs - and even the occasional cap - to keep threaded holes masked properly.
Plugs for blind holes with threads
When the thread does not go through the part, it is called a blind hole. Typically these are masked with tapered plugs (STP), alternatively with selected tapered plugs with a handle (STP-H) or if the lead-in thread must be masked as well, a first thread plug (VTMP). Scroll to the bottom of page for our threaded hole / plugs chart, then use the links below to get the right plug to mask common UNC and metric thread sizes.
Plugs for thru holes with threads
For threaded holes that go all the way through metal - typically 1" or less - then a pull plug (SPP) is often used for quick and effective masking. When the lead thread must be masked as well, a specialized pull plug with a flange on one end (SFPP) is used. Scroll to the bottom of page for our threaded hole / plugs chart, then use the links below to get the right plug to mask common UNC and metric thread sizes.
Download the chart below in PDF format for printing / quick reference
Don't see the thread you need a plug for listed below? Email us at [email protected] or give us a call at 866-534-3900 - we actually pick up our phone during business hours - for real! (7:30 am to 4 pm Central Time)
Common threads & plugs for blind and thru holes
| Thread size |
Plugs for blind holes |
Plugs for thru‑holes |
| Tapered plug |
Tapered plug w/handle |
1st thread plug w/handle |
Pull plug w/handle |
Pull plug w/handle and flange for first thread |
| 4‑40 |
STP100 |
STP100‑H |
N/A |
SPP11 |
N/A |
| 6‑32 |
STP101 / STP101XL |
STP101‑H |
VTMP‑0107 |
SPP14 |
N/A |
| M4‑0.7 |
STP101 / STP101XL |
STP101‑H |
VTMP‑0141 |
SPP18, SPP20, SPP21 |
N/A |
| 8‑32 |
STP101 / STP101XL |
STP101‑H |
N/A |
SPP18, SPP20 |
N/A |
| M5‑0.8 |
STP1012 / STP102XL |
STP102‑H |
VTMP‑0178 |
SPP22A |
SFPP‑0173‑RED |
| 10‑24 |
STP102 / STP102XL |
STP102‑H |
VTMP‑0178 |
SPP22A |
SFPP‑0173‑RED |
| M6‑1.0 |
STP103 / STP103XL |
STP103‑H |
VTMP‑0208 |
SPP30 |
SFPP‑0210‑WHITE |
| 1/4‑20 |
STP103 / STP103XL |
STP103‑H |
VTMP‑0208, VTMP‑0218 |
SPP30 |
SFPP‑0218‑BLUE, SFPP‑0230‑GREY |
| 5/16‑18 |
STP104 / STP104XL |
STP104‑H |
VTMP‑0278 |
SPP40 |
SFPP‑0285‑YEL |
| M8‑1.25 |
STP104 / STP104XL |
STP104‑H |
N/A |
SC172 cap (nose-in / use like plug) |
SFPP‑0285‑YEL |
| 3/8‑16 |
STP106 |
N/A |
VTMP‑0336 |
SPP42, SPP43 |
SFPP‑0335‑OR |
| M10‑1.5 |
STP106 |
N/A |
VTMP‑0358 |
SPP50 |
SFPP‑0350‑PINK |
| M12‑1.75 |
STP00 |
STP00‑H |
VTMP‑0426 (non-stock) |
SPP66 |
SFPP‑0420‑GREEN |
| 1/2‑13 |
STP108 |
N/A |
VTMP‑0451 |
SPP66, SPP67 |
SFPP‑0445‑PUR |
Want to print this chart do you can keep it handy? Download it here in PDF format.