Radial-Lok, Monogram
MRL3212-06-400
Hole-filling blind bolt: radial expansion fills a clearance-fit hole from one side.

- Head 100° flush tension head
- Diameter 3/16" (-6)
- Grip .350-.400"
- Material Titanium
MRL3212-06-400
- What it is
- Radial-Lok (Monogram), 100° flush tension head, 3/16" (-6) diameter, grip range 0.350-0.400" (drawing Table II)
- Equivalents
- No equivalent on file: no maker document names one and the government catalog lists none on its stock number.
- Install tooling, by who made the part
- Radial-Lok: MP550RL-6AA (complete tool)
The nose follows the maker, not the stock number: check the maker on the CoC or packaging.
Reference only: the drawing and its process spec govern. How to read this
Install tool MP550RL-6AA, proprietary · Exact nose, every brand · Variable stack? Plan grips
| Family | Radial-Lok (Monogram) |
|---|---|
| Head style | 100° flush tension head (source: Monogram drawing MRL3212 Rev AD, title block) |
| Nominal diameter | 3/16" (-6) |
| Grip | grip range 0.350-0.400" (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.
Reference only: the controlling drawing, its process spec and the manufacturer's installation instructions govern. How to use these answers
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: 3/16" (-6)
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.
Required tooling, every brand
MRL3212-06-400 (Radial-Lok, 3/16") installs with MP550RL-6AA (MP550RL with MPPBF-8 + MPBF-6) Standard.
Other tools that work1 process-doc listing
As the fastener's own process document lists them
- MRT550RL-6AA (MRT550RL with MRTPRL-8 + MRTRL-6) Right angle Monogram MRL1003 p.7 ↗
Sources2
- Monogram MRL1003 (Radial-Lok install spec), p.6, Table 1 ↗
- Wrench adapter (turns screw) MPBF-6; nose adapter (holds nut) MPPBF-8.
- Monogram MRL1003 (Radial-Lok install spec), p.7, Table 2 ↗
- Wrench adapter MRTRL-6; nose adapter MRTPRL-8.
Diameter -6 (3/16"): decoded from the part number.
Tool catalogs are the manufacturers' as published in the cited edition; confirm current PNs with the tool maker before purchase. Install per the OEM process specification.
Install tooling
Install tooling: MP550RL-6AA (Monogram MRL1003 (Radial-Lok install spec), p.6, Table 1) · proprietary
- MGFRL-6 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)
MRL3212-06-400 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 ↗
Family-level estimate, not specific to MRL3212-06-400: High (SpecLok sourcing assessment; no DLA lead time or stock on file for this part number)
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 2026-10-02.
Image credits: Monogram Aerospace Fasteners, Radial-Lok® product page (pennaero.com) ↗. Product images belong to their manufacturers.
Sources
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