Name: MBF2120-8-400
Brand: Monogram

MBF2120-8-400 decoded
Family	Composi-Lok II (Monogram)
Head style	Low profile protruding head (source: Monogram drawing MBF2120 Rev U, title block, Table I, material notes)
Nominal diameter	1/4" (-8)
Grip	max grip .400" (grip range .350-.400", MBF2120 Rev U grip table)
Material	A286 CRES. Nut & screw: A286; sleeve: 304 stainless steel

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.

Dimensions

Dimensions as printed, inches
A	Head diameter	.546/.516
D	Nut shank diameter	.2595/.2575
G	Max grip + G: datum to the end of the nut shank	.055(ref)
H	Head height	.085/.078
L	Max grip + L: datum to the end of the screw	.700(ref)
Recom. Hole	Drilled hole	.263/.260

All dimensions (19)

E	SLEEVE and SCREW head diameter (2X)	.2595max
F	SCREW wrench flats, on the tail	.135/.130
R	NUT head-to-shank radius	.030max
T	DRIVE NUT hex across flats	.375(ref)
Z	Height of the cylindrical head edge	.040max
Min Avail. Grip	Min available grip dash	-150
J	Installed blind head diameter	.400min
K	Installed: blind side protrusion	.450max
Break-Off	Screw break-off, measured from the skin surface	+.103/-.000
Tensile	Tensile structural failure, min (lbs)	2100min, lbs
Double Shear	Double shear, min (lbs)	7900min, lbs
Locking Torque	Locking torque, min (in-lbs)	2.5min, in-lbs
Grip limits	Dash 8-400	.350-.400

As printed on MBF2120 Rev U sheet 1 ↗. Letters match the drawing.

Some features are scaled from the figure, not dimensioned.Scaled features

Scaled from the drawing's figure (not drawing dimensions)

Component / feature	Scaled as	Model (in)
NUTnut nose diameter at its end (diameter)	0.768 x D	.1985
NUTnut nose end, from the datum	0.162 x L - G	-.5595
NUTnut bore = screw thread crest diameter (diameter)	0.713 x D	.1843
SCREWscrew thread crest diameter (threads not modelled)	0.713 x D	.1843
SLEEVEsleeve bore over the nut nose and the insert (diameter)	0.839 x D	.2168
SLEEVEsleeve bore beyond the insert (diameter)	0.729 x D	.1885
INSERTinsert outside diameter (= sleeve bore)	0.839 x D	.2168
INSERTinsert inside diameter (= sleeve bore beyond the insert)	0.729 x D	.1885
INSERTinsert end, from the datum	0.368 x L - G	-.6921
SLEEVEcrimp line (start of the crimped band), from the datum	0.722 x L - G	-.9209
SCREWscrew head top (sleeve end), from the datum	0.828 x L - G	-.9889
SCREWscrew head corner radius	0.062 x E	.0160
SLEEVEsleeve top, from the datum (where the scaled nose meets the scaled sleeve bore)	0.112 x L - G	-.5275
NUTnut nose taper (included angle)	angle, as drawn	32.1°
DRIVE NUTdrive nut length	1.064 x T	.3992
DRIVE NUTdrive nut bearing diameter (cone end on the head)	0.684 x T	.2567
DRIVE NUTdrive nut bearing cone (half angle from the axis)	angle, as drawn	30.5°
SCREWscrew tail beyond the drive nut	1.071 x T	.4017
SCREWwrench flats run: tail end to the drive nut (as drawn)	as drawn	.4017
NUThead chamfer above the Z edge (angle from the axis)	angle, as drawn	44.5°

Measured on MBF2120 Rev U sheet 1 figure at 300 dpi and kept as a ratio to a dimension this part number prints. Figure scale 589.6 px/in, fitting row -8, taken from A and E; checked against D (+1.7%), T (+1.8%), F (+3.7%), L - G (+2.3%).

Also printed in MBF2120 Rev U for this part

Recommended hole	.260-.263 in (MBF2120 Rev U sheet 1)
Installed blind head	J .400 in min diameter (MBF2120 Rev U sheet 1)
Installed protrusion	K .450 in max (TYPICAL INSTALLATION) (MBF2120 Rev U sheet 1)
Break-off limits	+.103 -.000 in, measured from the skin surface (MBF2120 Rev U sheet 1)
Tensile	2100 lbs min (structural failure) (MBF2120 Rev U sheet 1)
Double shear	7900 lbs min (MBF2120 Rev U sheet 1)
Locking torque	2.5 in-lbs min (MBF2120 Rev U sheet 1)
Min available grip	dash -150 (MBF2120 Rev U sheet 1)
Material and heat treat	NUT & SCREW: A286 PER THE CHEMICAL REQUIREMENTS OF AMS5731, AMS5732, AMS5734 AND AMS5737. HEAT TREATED AS REQUIRED FOR PERFORMANCE. SLEEVE: 304 STAINLESS STEEL PER AMS5639, HEAT TREATED AS REQUIRED FOR PERFORMANCE. INSERT: ACETAL PER ASTM-D4181 DRIVE NUT: MILD STEEL. (MBF2120 Rev U material and finish notes)
Finish	NUT, SCREW & SLEEVE: PASSIVATE PER AMS-QQ-P-35. KAL-GARD ANN-RO #1013, CONVERSION COATING OPTIONAL. INSERT: NONE. DRIVE NUT: CORROSION RESISTANT COATING COLOR BLACK. (MBF2120 Rev U material and finish notes)
Lubricant	DRY FILM LUBE PER MIL-L-46010 TYPE I OR EVERLUBE #812 PER MIL-L-81329, PARAFFIN WAX, OR CETYL ALCOHOL PER MIL-L-87132. (MBF2120 Rev U material and finish notes)

Series and strength (datasheet)

MBF2110 · MBF2111 · MBF2112 · MBF2113 · MBF2120 · MBF2121 · e.g. MBF2112-6-500

Rated shear 75 KSI (catalog comparison chart, MBF2112-06-500); 3/16" (-6) double shear 4,600 lb min, tensile 1,400 lb min, all materials & head styles (MBF2003 Table 10A).

Datasheet (PDF) ↗

Section from Monogram drawing MBF2120 Rev U ↗ sheet 1.Drawing notes

Section drawn from the printed values in Monogram drawing MBF2120 Rev U sheet 1 (blind fastener, low profile protruding head). Letters are the drawing's. Manufacturer nominal: printed values, the mean where only two limits are printed. Head drawn as its A x H envelope: the drawing dimensions the head edge (Z max) but not the chamfer above it. Section through the axis: NUT, SCREW, SLEEVE, INSERT and DRIVE NUT as the drawing names them, each hatched on its own. Max grip .400 plus G .055 and L .700. The drive nut is cut through its hex corners, as the figure draws it; T is across the flats (dashed). Features the drawing shows without a dimension (nut nose, sleeve start and bores, insert, screw thread, screw head length and corner, crimp line, drive nut length and cone, tail length) are scaled from MBF2120 Rev U sheet 1 figure and are not drawing dimensions; the INSERT is all scaled (dashed outline). Threads not modelled.

Model: Monogram drawing MBF2120 Rev U

Envelope model, not manufacturer CAD.Model details

MBF2120-8-400, manufacturer nominal. Simplified component model from Monogram drawing MBF2120 Rev U sheet 1. Manufacturer nominal: printed values, the mean where only two limits are printed. Flush heads hold the printed head angle; the head depth is derived. Not manufacturer CAD. Verify against the current drawing before use. One named solid per component as the drawing calls them out (NUT, SCREW, SLEEVE, INSERT and, where the drawing has one, DRIVE NUT). Features the drawing shows without a dimension are scaled from its figure and listed as scaled in the STEP header; threads are not modelled. Axis +Z, head up, z = 0 at the face the head bears on. STEP (AP214) is in inches; STL has no units and is written in millimetres.

Other head styles, same diameter and grip

MBF2121-8-400 reduced protruding hex head
MBF2112-8-400 100° flush head
MBF2113-8-400 130° flush head

MBF2120 grip chart: 1/4" (-8)

32 grips

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:

MBF2120-5-400 MBF2120-6-400 MBF2120-7-400 MBF2120-9-400 MBF2120-10-400 MBF2120-11-400 MBF2120-12-400

Exploded view of the fastener.US 4,457,652, Composite buckling blind fastener (Pratt), Fig. 6 ↗ · US patent drawingWhy this family: Monogram's US 10,267,347 states: "the original Composi-Lok fastener is described in U.S. Pat. No. 4,457,652" (John D. Pratt, 1984; later assigned to Monogram). Shows the original Composi-Lok, not the Composi-Lok II drive-nut version.

Axial cross-sectional view of the assembled fastener prior to installation. — Exploded view of the fastener.US 4,457,652, Composite buckling blind fastener (Pratt), Fig. 6 ↗ · US patent drawingWhy this family: Monogram's US 10,267,347 states: "the original Composi-Lok fastener is described in U.S. Pat. No. 4,457,652" (John D. Pratt, 1984; later assigned to Monogram). Shows the original Composi-Lok, not the Composi-Lok II drive-nut version.

Install tooling

Install tooling: MP550BFP-8AA (Monogram MBF2003 Rev AG (Composi-Lok II install spec), p.4, Table 1) · proprietary

MGPCL Protruding head leaf gage (break-off check)
RM3118-08 Removal nose piece module, flush head style

Composi-Lok II tool tables

Decode details

Decode details
Series	Composi-Lok II
Decode confidence	high
Numbering source	Monogram drawing MBF2120 Rev U, title block, Table I, material notes

Composi-Lok II grips: "incremental 0.050\" grip lengths" (MBF2003 §2.1); the grip dash is the max grip, e.g. -300 covers .250-.300" (MBF2110/2112/2113 drawings, grip table).
Diameter dash per the drawing's basic-dimensions table (e.g. -6 = 3/16").
Suffix "A" "designates dual drive nut system for robotic installation" (MBF2112 drawing note 1); MBF2003's installation tooling "not applicable to Composi-Lok II which have an 'A' suffix" (MBF2003 §1.1).

Government reference cross-reference (DLA FLIS)

not listed under this PN

MBF2120-8-400 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.

Cross-reference MBF2120-8-400

Composi-Lok II by Monogram, blind bolt
Datasheet (PDF) ↗
Manufacturer page ↗
Numbering: Monogram drawing MBF2120 Rev U, title block, Table I, material notes ↗
Geometry: MBF2120 Rev U ↗

Lead-time risk for this family (SpecLok sourcing assessment): High

Supply signal

not in FLIS by this PN; no SpecLok quotes yet

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.