Name: Radial-Lok
Brand: Monogram

Blind (one-sided), threaded blind bolt: “Torque is applied to the screw, while the DRIVE NUT is held stationary.” (Monogram Radial-Lok brochure, p.2, Installation Sequence)

Shear: 75 ksi
Blind bulb: large
Install: One-side install
Diameters: 3/16, 1/4, 5/16, 3/8"
Lead-time risk (SpecLok assessment): High

Typical applications

·"Composite and metallic structures" (catalog p.4)

Strengths

+"Radial expansion of up to .005\"" (catalog p.4; comparison chart: up to .006\")
+"Clearance fit before installation" (catalog p.4)
+"High clamp-up"; "highly resistant to vibration" (catalog p.4)

Trade-offs

−Monogram installation tooling (MRL1003)

Also called RadialLok. P/N: MRL3210 (low profile protruding head) / MRL3212 (100° flush tension head) · e.g. MRL3212-06-500

Datasheet strength: 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.

Standards

Monogram MRL series (install spec MRL1003)

Materials and galvanic compatibility vs CFRP

Alloy	Shear	vs CFRP	Notes	Source
Titanium	75 ksi	low	6-4 Ti nut body	Monogram catalog comparison chart, MRL3212-06-500: rated 75 KSI
Inconel	75 ksi	low	Inconel screw (stainless sleeve)	Monogram catalog comparison chart

vs CFRP: MIL-STD-889C Table I, graphite column: high = incompatible in all environments; low = compatible except sea-water immersion; unrated = SpecLok has not read a rating for this material.About derived ksi

Derived ksi values are min shear ÷ nominal shank area, computed from the datasheet's lbf/kN figures; the datasheet itself publishes no ksi.

Specs source: Monogram catalog (Radial-Lok page + comparison chart) ↗: p.4: 3/16"-3/8", .100" grips, radial expansion; comparison chart: materials, 75 KSI, 4,800 lb double shear min, 700 lb preload min. Lead-time risk is SpecLok's sourcing assessment, not a datasheet value.

2 head styles

Drawn from the -6 (3/16") row: (A) head dia, ref, H (head height), (D) .197 ref. Monogram drawing MRL3210 Rev AM, Table I, MRL3210-6 ↗

Low profile protruding head

MRL3210: Titanium. Nut: 6Al-4V titanium alloy; screw: Inconel 718-6 to -12; min / max available grip -100 / -600 at -6 (Table I continued).

Head-specific tooling

MGPRL-( ) Protruding head leaf gage (break-off check) (Monogram MRL1003, Figure 9, Table 6 ↗)

Source: Monogram drawing MRL3210 Rev AM, title block ↗

The two Radial-Lok drawings on file (MRL3210, MRL3212).

Head styles (manufacturer terms)

Low profile protruding head (MRL3210)
100° flush tension head (MRL3212)

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.

Key (how to read these diagrams)

Manufacturer figure: Monogram Radial-Lok brochure, p.2, Installation Sequence, panels 1-3 ↗Schematic cross-section at the source figure's proportions, not to scale. Terms are the document's own.

Compare every family's mechanism

Official manufacturer install demonstration: Radial-Lok installation.

Installation verification and preload

Installed preload

Minimum preload per diameter (brochure table): -6: 700 lb · -7: 700 lb · -8: 1,000 lb · -9: 1,000 lb · -10: 1,500 lb · -11: 1,500 lb · -12: 2,000 lb
3/16" Ti (MRL3212-06), catalog chart: 700 lb minimum · 1,000 lb typical

The best-published preload in the catalog: an explicit per-size minimum preload column in the Radial-Lok brochure. Values are fastener capabilities, not joint requirements.

What to check after install

Unique blind-side check: footprint diameter J must meet the minimum per MRL1003 Table 3 (-6: .290" up to -12: .560"); an undersized footprint is positive indication of improper installation.
Screw break-off limits per product drawing (MRL3210: -6/-7 +.275"/+.075" above surface, up to -12 +.335"/+.135").
Blind-side protrusion K max .500"-.625" by size.
Mandatory hole-edge chamfer or fillet radius before install (MRL1003 Table 3). No seating-torque table exists for this family.

Check gauges (2) and sources.Details

MRLG-6 through MRLG-12 GO/NO-GO hole gauges, required before installation (GO must pass completely through).
MGFRL flush barrel and MGPRL protruding leaf break-off gauges (rock / no-rock).

Sources: MRL1003 installation spec · Radial-Lok brochure (preload table) · MRL3210 drawing. Acceptance limits belong to the controlling spec; verify against your program's process documentation.

Print a shop verification card for the floor

Tool: Monogram installation tooling (install spec MRL1003)
Special / proprietary: Special tooling · proprietary
Training: Not stated in the cited documents.
Inspection: Footprint, break-off and hole gauging per MRL1003 (see verification below).

"Radial expansion of up to .005\"" and ".100\" grip accommodations" (catalog p.4); comparison chart: "up to .006\" via unique radial expansion during installation". Grip range per drawing: MRL3210 .100", MRL3212 .050".

The published install tool and nose for each size, other access options, and the gauges that check the install, from the manufacturer's own tool tables.

Dia.	Published tool + nose	Other access	Gauges
-6	MP550RL-6AA (MP550RL + MPPBF-8 + MPBF-6)	Right angle	RLS-1A, MRLG-6, MGFRL-6 / MGPRL-6
-8	MP550RL-8AA (MP550RL + MPPBF-8 + MPBF-8)	Right angle	RLS-1A, MRLG-8, MGFRL-8 / MGPRL-8
-10	MP550RL-10AA (MP550RL + MPP-12 + MPTRL-10)	None published	RLS-1A, MRLG-10, MGFRL-10 / MGPRL-10
-12	MP550RL-12AA (MP550RL + MPP-12 + MPTRL-12)	None published	RLS-1A, MRLG-12, MGFRL-12 / MGPRL-12

Full tool tables, envelopes, clearances and source notes Compare tooling burden across all 25 families

Monogram MRL1003 (Radial-Lok), §8.0, Figure 10 and Table 7

“Radial-Lok blind fasteners can be removed using the tooling shown in Figure 10 and Table 7 of this specification. Complete kits are available from Monogram Aerospace Fasteners. Contact factory for details.” Monogram MRL1003 (Radial-Lok install spec), p.5, §8.1 ↗
“Screw protrusion shall be shaved flush prior to drilling.” Monogram MRL1003 (Radial-Lok install spec), p.15, Figure 10, Removal Tool ↗
“A complete tool consists of the air motor middle (#RM3098), a nose piece module (see chart), and a carbide star drill (RM3050-( )).” Monogram MRL1003 (Radial-Lok install spec), p.14, Table 7, Removal Data ↗

Cautions

“If a fastener has been removed, the same diameter Radial-Lok can be reinstalled provided the hole has not been damaged. In the event that the hole has been damaged, the next larger diameter Radial-Lok shall be used (NOTE: for flush head fasteners the countersink will have to be deepened).” Monogram MRL1003 (Radial-Lok install spec), p.3, §4.6 ↗
“This kit is used to removed alloy steel, titanium and A-286 Visu-Loks or A-286 and titanium Composi-Lok and Radial-Lok fasteners. To remove H-11 and similar material, contact factory for details.” Monogram MRL1003 (Radial-Lok install spec), p.14, Table 7, Removal Data ↗

Removal data (Table 7)

Nominal diameter	Nose piece module	Carbide star drill	Drill size dia.	Depth gage
-6 (.1975)	RM3081-6	RC3050-6	.1890	RC3031-6
-7 (.2265)	RM3081-7	RC3050-7	.2180	RC3031-7
-8 (.2585)	RM3081-8	RC3050-8	.2500	RC3031-8
-9 (.2885)	RM3081-9	RC3050-9	.2810	RC3031-9
-10 (.3105)	RM3153-10	RC3050-10	.3020	RC3156-10
-11 (.3425)	RM3153-11	RC3050-11	.3320	RC3156-11
-12 (.3735)	RM3153-12	RC3050-12	.3590	RC3156-12

Monogram MRL1003 (Radial-Lok install spec), p.14, Table 7, Removal Data ↗

None of the removal procedures on file gives a composite-specific removal caution. The Monogram specs address composite at the hole instead: holes "reasonably round and free from burrs (metallic structure) and delamination (graphite/epoxy type structure)" (MBF2003 §5.1).

MRL3212
Diameters 3/16", 1/4", 5/16", 3/8" · 17 grip lengths
Every dash number Plan grips for your stack

Manufacturer: Monogram
Category: Blind bolt

Datasheet (PDF) ↗
Manufacturer page ↗
Monogram catalog (Radial-Lok page + comparison chart) ↗: p.4: 3/16"-3/8", .100" grips, radial expansion; comparison chart: materials, 75 KSI, 4,800 lb double shear min, 700 lb preload min.

Find the part number for your stack

DiameterStack thickness, in

Enter your stack thickness and diameter to get the MRL3212 dash number.

Dash numbers and grips: Monogram drawing MRL3212 Rev AD, Tables I & II ↗

QtyInclude install tooling

Sourcing

Lead-time risk (SpecLok sourcing assessment): High

Get quotes: SpecLok sources this from authorized distributors and returns price, lead time and certs.You buy from the authorized distributor, who is named on your returned quote. SpecLok is free for buyers.

Supply signalfor this family

42 NSNs carry a part number of this family, recorded by 6 CAGE codes (FLIS, March 2025).
Last DoD award for RIVET,BLIND items (FSC 5320): 2026-06-26; 3,082 awards since 2025-10-01.
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.