Radial-Lok, Monogram
MRL3212-12-600
Hole-filling blind bolt: radial expansion fills a clearance-fit hole from one side.

- Head 100° flush tension head
- Diameter 3/8" (-12)
- Grip .550-.600"
- Material Titanium
- Lead-time risk High
Install tool MP550RL-12AA, proprietary · Variable stack? Plan grips
| Family | Radial-Lok (Monogram) |
|---|---|
| Head style | 100° flush tension head (source: Monogram drawing MRL3212 Rev AD, title block) |
| Nominal diameter | 3/8" (-12) |
| Grip | grip range 0.550-0.600" (drawing Table II) |
| Material | Titanium. Nut: 6Al-4V titanium alloy; screw: Inconel 718; sleeve: 304 stainless steel; expansion sleeve: A286 |
Decoded from the published numbering scheme; not a claim that this exact dash number is a stocked SKU, and not a certified design authority. Always verify against the controlling drawing, spec, and your stress group.
Series and strength (datasheet)
MRL3210 (low profile protruding head) / MRL3212 (100° flush tension head) · e.g. MRL3212-06-500
Rated shear 75 KSI; 3/16" double shear 4,800 lb min, tensile 1,600 lb min; "up to .006" via unique radial expansion": Monogram catalog comparison chart.
Datasheet (PDF) ↗MRL3212 grip chart: 3/8" (-12)
Every catalogued max-grip dash number at this diameter. Stack thickness must fall inside the fastener's grip range: see the design calculators.
Other diameters at this grip:
Expanding sleeve · 3 steps
1/3Inserted, tool placed
“The Radial-Lok fastener is first inserted into the prepared clearance fit hole. The installation tool is placed over the screw, simultaneously engaging the wrench flats and the DRIVE NUT.”
Monogram Radial-Lok brochure, p.2, Installation Sequence ↗
Drawing traced from: Panel 1.
Install tooling
Install tooling: MP550RL-12AA (Monogram MRL1003 (Radial-Lok install spec), p.6, Table 1) · proprietary
- MGFRL-12 Flush head barrel gage (break-off check)
Decode details
| Series | Radial-Lok (Monogram) |
|---|---|
| Decode confidence | high |
| Numbering source | Monogram drawing MRL3212 |
- MRL3210 and MRL3212 use different grip conventions (see each drawing's grip table); other MRL bases are not decoded.
Government reference cross-reference (DLA FLIS)
MRL3212-12-600 is not listed in FLIS under this exact part number (FLIS data as of 2025-03-18, March 2025 snapshot). FLIS may record it with a material or finish code, or under the standard part number.
Source: DLA PUB LOG ↗. Search any part number in the decoder.
- Radial-Lok by Monogram, blind bolt
- Datasheet (PDF) ↗
- Manufacturer page ↗
- Numbering: Monogram drawing MRL3212 ↗
Lead-time risk for this family (SpecLok sourcing assessment): High
Supply signal
Supply signalfor this part number
- Not listed in FLIS under this exact part number (March 2025 snapshot).
- No SpecLok quotes yet.
A signal from records SpecLok holds, not availability, stock or a lead-time promise. FLIS lists who has recorded a part number for the item, not who makes it today. DoD awards carry no NSN or part number, so award activity is for the item name's class.
Sources: DLA FLIS Data Electronic Reading Room (PUB LOG) ↗, DLA PUB LOG ↗, USAspending.gov award search API ↗; DoD award data 2025-10-01 to 2026-07-06; compiled 2026-09-28.
Image credits: Monogram Aerospace Fasteners, Radial-Lok® product page (pennaero.com) ↗. Product images belong to their manufacturers.
Sources
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