quarter turn fasteners, aircraft, engine cowlings, racing fasteners, quick release, quick access
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Z-Lock  Fasteners  and  Accessories

1/4-Turn  fasteners  and  accessories

Ejecting racing chassis body panels and hood dzus fasteners.
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EHF Style, Ejector Head Studs
 EHF Wing Head Ejector Stud
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EHF Style, Ejector Head Studs

Aircraft fastener AJ series dzus studs oval head cowl fasteners.
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Retainable
Studs

 Aircraft fasteners cowling studs grommets and retainers for Cessna.
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Retainable
Studs
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Non-Retainable Wing Studs


 Racing fasteners from milspec panel fastener oval head AO not retainable..
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Non-Retainable
Studs

Dzus type quarter 1/4 turn racing fasteners. Race car body panel fastener.
Click for Larger Image

Non-Retainable
Studs

Full flare type aluminum dzus grommets for aircraft and racing fasteners.
Click for Larger Image		 Z-Lock Weld Tab
Click for Larger Image		 Dzus springs studs fastener quick release bolts for racing and aircraft.
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 Special tool for locking and unlocking dzus racing panel fasteners driver for race cars.
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Find detailed information on how to measure for Z-Lock stud replacement,
determine a part number, plus other useful technical information, here.

The important points to consider when selecting a fastener type are: Operational environment, required strength, mounting space available, weight restrictions and vibration. With these considerations in mind the next step is to take some basic measurements of the subject panel and mounting structure to make sure the components will fit in the space available. You will find dimensional prints in the following sections to use for this determination.

Next, measure the thickness of each panel and support (mounting) structure and add them together to determine the “Total Material Thickness” (TMT). This should also include any gaskets, seals, gaps etc. between panels. If using a gasket between panels we recommend using 1/2" of the gasket's uncompressed thickness for this calculation. Also, keep in mind that each fastener location may have different thickness due to the placement of doublers, reinforcements, or other structure. Make note of the TMT at each fastener location. This measurement is very important to assure a proper fit and accuracy is critical because most fastening systems only allow a small margin between sizes.

Use the charts below for determining which stud grip length ( - # ) and spring height should be used for your application. Please note that these combinations can be altered if necessary and that any combination can be greatly modified with our MS-7301 Spring Adjusting Tool.

COWLING FASTENER KITS COWL KIT STAINLESS FASTENER
Click on desired Part Number below to add the item to your shopping cart
(quantity can be adjusted after adding item to cart).

Z-Lock  -  EHF Style Ejector Studs, Flush Head

EHF Flush Ejector Stud Assy
Flush Head
EHF Style
Ejector Stud

 Ejector fasteners provide 1/4 turn action, with studs that eject from the receptacle when unlocked. They will not hang up when sliding or when curved panels are removed, and show a visual sign of an unlocked fastener. The stud assembly is mounted directly to the outside panel with 1/8" rivets or screws. Made from steel with bright Silver zinc plating. 



Gold zinc-plated and Wing Head versions
are also available, below.

#5 EHF Studs (Silver Zinc Plated)   #6 EHF Studs (Silver Zinc Plated)
Part Number Head Diameter Grip Length

EHF5-40

5/8"

.400"
EHF5-45

5/8"

 .450"

EHF5-50

5/8"

.500"

EHF5-55

5/8"

.550"

EHF5-60

5/8"

.600"

EHF5-65

5/8"

.650"
Part Number Head Diameter Grip Length

EHF6-40

3/4"

.400"
EHF6-45 3/4" .450"

EHF6-50

3/4"

.500"

EHF6-55

3/4"

.550"

EHF6-60

3/4"

.600"

EHF6-65

3/4"

.650"
 

    #6 EHF Studs (Gold Zinc Plated)
EHF Flush Stud Gold

Flush Head
EHF Style (Gold)
#6 Ejector Stud
Part Number Head Diameter Grip Length

EHF6-50G

3/4"

.550"

EHF6-55G

 3/4"

.600"

EHF6-60G

3/4"

.650"

 

     Z-Lock  -  EHF Style Ejector Studs, Wing Head

Z-Lock EHF Style Ejector Stud, Wing Head
Wing Head
EHF Style
Ejector Stud

 Wing Head Ejector fasteners provide tool-less 1/4 turn action, with studs that eject from the receptacle when unlocked. They will not hang up when sliding or when curved panels are removed, and show a visual sign of an unlocked fastener. The stud assembly is mounted directly to the outside panel with 1/8" rivets or screws. Made from steel with bright Silver zinc plating.

#5 EHF Style - Wing Head Studs   #6 EHF Style - Wing Head Studs
Part Number Head Diameter Grip Length

EHF5-40W

5/8"

.400"
EHF5-45W

5/8"

 .450"

EHF5-50W

5/8"

.500"

EHF5-55W

5/8"

.550"

EHF5-60W

5/8"

.600"

EHF5-65W

5/8"

.650"
Part Number Head Diameter Grip Length

EHF6-40W

3/4"

.400"
EHF6-45W 3/4" .450"

EHF6-50W

3/4"

.500"

EHF6-55W

3/4"

.550"

EHF6-60W

3/4"

.600"

EHF6-65W

3/4"

.650"

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Z-Lock  -  AJ and FJ Style Retainable Studs
Aircraft fastener AJ series dzus studs oval head cowl fasteners.
AJ Style
(Oval Head) Retainable
Studs

 Aircraft style, retainable studs insure that the fastener stays with the panel when unlocked. A simple groove under the head allows  for the installation of several types of retainers. Full (flare-type) Grommets protect the panel hole from enlargement due to vibration, while also retaining the stud in the outer panel. Simple snap ring and nylon washer type Retainers insure that the stud stays with the panel when unlocked but, do not offer hole protection. Available in oval head or countersunk flush head. Materials include steel, stainless and aluminum (please call to order materials not listed below). Several other stud sizes and styles are also available by special order. Please call for further details and ordering information.
Aircraft fasteners cowling studs grommets and retainers for Cessna.
FJ Style
(Flush Head) Retainable
Studs
  FA Style, 6.5 Series Flush Head Studs for Warbirds
and other vintage aircraft can be found below.		  

  Use with "GA" Type Grommets    Use with "GF" Type Grommets 
AJ Style, Oval Head Studs FJ Style, Flush Head Studs

Oval Head Part Number
(Stainless)

Shank
Diameter

Grip
Length

 

Flush Head Part Number
(Stainless)

Shank
Diameter

Grip
Length

AJ3-25SS

3/16"

.250"

 

FJ3-30SS

3/16"

.300"

AJ3-30SS

3/16"

.300"

 

FJ3-35SS

3/16"

.350"

AJ3-35SS

3/16"

.350"

 

FJ4-30SS

1/4"

.300"

AJ4-30SS

1/4"

.300"

 

FJ4-35SS

1/4"

.350"

AJ4-35SS

1/4"

.350"

 

FJ4-40SS

1/4"

.400"

AJ4-40SS

1/4"

.400"

 

FJ4-45SS

1/4"

.450"

AJ4-45SS

1/4"

.450"

 

FJ4-50SS

1/4"

.500"

AJ4-50SS

1/4"

.500"

  

FJ5-30SS

5/16"

.300"

AJ5-30SS

5/16"

.300"

 

FJ5-35SS

5/16"

.350"

AJ5-35SS

5/16"

.350"

 

FJ5-40SS

5/16"

.400"

AJ5-40SS

5/16"

.400"

 

FJ5-45SS

5/16"

.450"

AJ5-45SS

5/16"

.450"

 

FJ5-50SS

5/16"

.500"

AJ5-50SS

5/16"

.500"

 

FJ5-55SS

5/16"

.550"
AJ5-55SS

5/16"

.550"

 

FJ6-45SS

3/8"

.450"
AJ5-60SS

5/16"

.600"

 

FJ6-50SS

3/8"

.500"
AJ5-65SS

5/16"

.650"

 

FJ6-55SS

3/8"

.550"

AJ65-40SS

13/32"(.406")

 .400"

 

FJ6-60SS

3/8"

.600"

AJ65-45SS

13/32"(.406")

 .450"

 

FJ65-40SS

3/32"(.406")

.400"

AJ65-50SS

13/32"(.406")

.500"

 

FJ65-45SS

13/32"(.406")

.450"

AJ65-55SS

13/32"(.406")

.550"

 

FJ65-50SS

13/32"(.406")

.500"

AJ65-60SS

13/32"(.406")

.600"

 

FJ65-55SS

13/32"(.406")

.550"

 

Z-Lock  -  FA Style Retainable Studs (Warbirds)

FA6.5 series fasteners for Warbirds and other vintage aircraft.

Aircraft fasteners cowling studs grommets and retainers for Cessna.
FA Style
(Flush Head) Retainable
Studs
Flush Head Part Number
(Stainless)

Shank Diameter

Grip Length

FA65-45SS

13/32"(.406")

 .450"

FA65-50SS

13/32"(.406")

 .500"

FA65-55SS

13/32"(.406")

.550"

FA65-60SS

13/32"(.406")

.600"

FA65-65SS

13/32"(.406")

.650"

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     Z-Lock  -  Flare-type (Full) Grommets

Full flare type aluminum dzus grommets for aircraft and racing fasteners.
Flare-Type
Grommets

This standard style grommet is used in virtually every aircraft equipped with Z-Lock type (DZUS®-style) retainable fasteners. These popular flare-type grommets have been around since the early days of the 1/4-turn fastener. Today, because of MilSpec's highly efficient machining methods, we offer these fine quality OEM style grommets at the lowest prices around!  *Please Note: Special tools are required to install these grommets. Grommet flaring tools can be found below, and on our main Tools Page.

Grommets & Retainers are used with   "AJ"  &  "FJ"   Style Retainable Studs ONLY.
"AO" & "FO" Style Non-Retainable Studs  DO NOT  Utilize Grommets or Retainers.

  • Precision machined for a bright and shiny finish.

  • These little guys are stronger and more durable than the OEM parts.

  • Grommet sizing and installation is the same as OEM parts.

  • Available in any size, including rare Warbirds and other vintage aircraft styles!

  • The days of factory minimums and long lead times are over.
Oval head Z-Lock dzus fateners for racing and airplane panels.
Type "GA"
(Oval Grommet)
Used with:
  Oval Head, Retainable Studs Only
ga5-312 dzus flare grommet for oval head 1/4 turn aircraft cowling studs.		 Z-Lock dzus flare grommet stud retainers for aircraft fasteners.
Type "GF"
(Flush Grommet)

Used with:
 Flush Head, Retainable Studs Only
dzus flare grommets for flush retainable aircraft cowling fasteners.

Use this table to select the proper grommet(s) for your application.
 "GA" grommets are used with AJ Studs, ONLY  |  "GF" grommets are used with FJ Studs, ONLY

* Important Note: Wall-Thickness of the grommet should be included in your total-thickness
calculations when determining proper stud length.
"GA"  &  "GF"  Flare-Type Grommets

Stud
Size

Panel
Thickness

Type "GA"
Part Number
(for AJ Studs)

Type "GF"
Part Number
(for FJ Studs)

Outside Diameter
(O.D.)

* Wall- Thickness

# 3

.015" - .025"

.026" - .050"

.051" - .094"

GA3-175

GA3-200

GA3-250

----

----

----

7/32"

.015"

# 4

.015" - .025"

.026" - .050"

.051" - .075"

.076" - .100"

GA4-225

GA4-250

GA4-275

GA4-300

GF4-125

GF4-150

GF4-175

GF4-200

5/16"

.025"

# 5

.031" - .062"

.063" - .094"

.095" - .125"

GA5-312

GA5-350

GA5-375

GF5-175

GF5-225

GF5-250

3/8"

.028"

# 6

.040" - .065"

.066" - .100"

.101" - .135"

GA6-350

GA6-375

GA6-425

GF6-218

GF6-250

GF6-300

7/16"

.028"

# 6.5

.040" - .065"

.066" - .100"

.101" - .135"

.136" - .200"

GA6.5-350

GA6.5-375

GA6.5-425

GA6.5-500

GF6.5-218

GF6.5-250

GF6.5-300

----

1/2"

.035"

 

Z-Lock  -  Stud Retainers

Stud Size

 Part Number
(Plastic, Dimpled)

Part Number
(Stainless, Snap-Ring)

Part Number
(Plastic, Flat)
#3 GP3 SR3 ----  
#4 GP4 SR4 ----  
#5 GP5 SR5 MS15-5L
#6 GP6 SR6 MS15-6L

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Z-Lock  -  AO and FO Style Non-Retainable Studs
Racing fasteners from milspec panel fastener oval head AO not retainable..
AO Style
(Oval Head)
Non-Retainable
Studs 

These Motor-Sports Racing-Style, Non-Retainable Studs can be completely removed from the panel  when unlocked, which can be advantageous with sliding or curved panels. Unlike undercut studs, these studs Do Not have a groove under the head for a retainer, and Do Not require the use of grommets for installation. Available in oval head or countersunk flush head. Materials include steel, stainless and aluminum. (please call to order materials not listed below).    Several other sizes and styles are available by special order, please call for further details and ordering information.

 Dzus type quarter 1/4 turn racing fasteners. Race car body panel fastener.
FO Style
(Flush Head) 
Non-Retainable
Studs

Wing Head versions are also available.
See Non-Retainable Wing Head Stud selection, below.

 The "AO / FO" Style Non-Retainable studs DO NOT  require Grommets or Retainers.

Our Retainable-Style, AJ and FJ Studs are available here.

AO Style, Oval Head Studs FO Style, Flush Head Studs

Oval Head
Part No. (Steel)

Oval Head
Part No. (Alum)

Shank Diameter

Grip
Length

 

Flush Head
Part No. (Steel)

Flush Head
Part No. (Alum)

Shank
Diameter

Grip
Length

AO4-30

AO4-30A

1/4"

.300"

 

FO4-30

FO4-30

1/4"

.300"

AO4-35

AO4-35A

1/4"

.350"

 

FO4-35

FO4-35

1/4"

.350"

AO4-40

AO4-40A

1/4"

.400"

 

FO4-40

FO4-40

1/4"

.400"

AO4-45

AO4-45A

1/4"

.450"

 

FO4-45

FO4-45

1/4"

.450"

AO5-40

 AO5-40A

5/16"

.400"

 

FO5-40

 FO5-40A

5/16"

.400"

AO5-45

 AO5-45A

5/16"

.450"

 

FO5-45

 FO5-45A

5/16"

.450"

AO5-50

 AO5-50A

5/16"

.500"

 

FO5-50

 FO5-50A

5/16"

.500"

AO5-55

 AO5-55A

5/16"

.550"

 

FO5-55

 FO5-55A

5/16"

.550"

AO5-60

 AO5-60A

5/16"

.600"

 

FO5-60

 FO5-60A

5/16"

.600"

AO5-65

 AO5-65A

5/16"

.650"

 

FO5-65

 FO5-65A

5/16"

.650"

AO65-40

 AO65-40A

.406"

.400"

 

FO65-40

 FO65-40A

.406"

.400"

AO65-45

 AO65-45A

.406"

.450"

 

FO65-45

 FO65-45A

.406"

.450"

AO65-50

 AO65-50A

.406"

.500"

 

FO65-50

 FO65-50A

.406"

.500"

AO65-55

 AO65-55A

.406"

.550"

 

FO65-55

 FO65-55A

.406"

.550"

AO65-60

 AO65-60A

.406"

.600"

 

FO65-60

 FO65-60A

.406"

.600"

AO65-65

 AO65-65A

.406"

.650"

 

FO65-65

 FO65-65A

.406"

.650"

AO Wing stud Dzus Z-Lock chassis fastener race car panel fabrication        

Z-Lock  -  Wing Head Style, Non-Retainable Studs

Wing Head
Part Number
(Steel)

Shank
Diameter

Grip
Length

AO5-40W

5/16"

.400"

AO5-45W

5/16"

.450"

AO5-50W

5/16"

.500"

AO5-55W

5/16"

.550"

AO65-45W

.406"

.450"

AO65-50W

.406"

.500"

AO65-55W

.406"

.550"

AO65-60W

.406"

.600"

AO65-65W

.406"

.650"

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Z-Lock  -  Weld Tabs
 
MS944
Ms946.jpg (9097 bytes)
 3/4" Rivet Spacing for #4 Springs		 MS945
Ms946.jpg (9097 bytes)
1" Rivet Spacing for #5 Springs		 MS945EHF Ms945ehf.jpg (7844 bytes)
1" RIVET SPACING FOR #5 SPRINGS
 		 MSX945
X945.jpg (7644 bytes)
1" RIVET SPACING FOR #5 SPRINGS
MS945CL
MS945CL Weld Tab
1" RIVET SPACING FOR #5 SPRINGS AND 
C-LOCK RECEPTACLES		 MS946
Ms946.jpg (9097 bytes)
1- 3/8" Rivet
Spacing for
#6 Springs		 MS-DP1 Ms-dp1.jpg (6713 bytes)
Panel Doublers (Spreads tensile load and adds strength to body panels)		  MS-6EDP
EHF Ejector Panel Doubler
 EHF Ejector
Doubler
Weld Tabs   

Part Number

Description

   Rivet Spacing

MS944 #4 Weld Tab 3/4"
MS945 #5 Weld Tab 1"
MS945EHF #5 EHF Weld Tab 1"
MSX945 #5 EHF Weld Tab, Long 1"
MS945CL #5 C-Lock Weld Tab 1"
MS946 #6 Weld Tab 1-3/8"
MS-6EDP #6 EHF Ejector Doubler N/A
MS-DP1 Panel Doubler, Round N/A

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Z-Lock  -  "S" Spring Receptacles
Dzus springs studs fastener quick release bolts for racing and aircraft.
Z-Lock
"S" Spring Receptacle
 
Spring Receptacles

Part Number

Description

(H) Dimension
MS3-150 #3 Spring Receptacle .150
MS3-175 #3 Spring Receptacle .175
MS4-200 #4 Spring Receptacle .200
MS4-225 #4 Spring Receptacle .225
MS4-250 #4 Spring Receptacle .250
MS4-275 #4 Spring Receptacle .275
MS5-200 #5 Spring Receptacle .200
MS5-225 #5 Spring Receptacle .225
MS5-250 #5 Spring Receptacle .250
MS5-275 #5 Spring Receptacle .275
MS5-300 #5 Spring Receptacle .300
MS5-325 #5 Spring Receptacle .325
MS5-375 #5 Spring Receptacle .375
MS6-225 #6 Spring Receptacle .225
MS6-250 #6 Spring Receptacle .250
MS6-275 #6 Spring Receptacle .275
MS6-300 #6 Spring Receptacle .300
MS6-350 #6 Spring Receptacle .350
MS6-375 #6 Spring Receptacle .375
MS6-400 #6 Spring Receptacle .400
MS6-425 #6 Spring Receptacle .425

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Z-Lock  -  Fastener Installation Tools
MS-7301 S-Spring Receptacle Adjustment Tool MS-7301 S-Spring Receptacle Adjustment Tool, Exploded View Our  MS-7301  Tool bends Z-Lock "S" Spring Receptacles quickly and easily. One stud length fits all panels with this tool. Adjust more than 1/2" by pulling on the spring. Special legs thread in to the solid steel base to pull on the rivets instead of your panels eliminating the risk of pull through. Soft pads protect your paint from scratches. Made from premium steel and zinc plated for long life. Fits all #5 and #6 series (1" and 1-3/8" rivet spacing) springs. Complete easy to follow instructions included.  
Click for Pricing

Racing panel fastener driver for racie car fasteners.

 Our  MS-DRIVER  is the ultimate tool for locking and unlocking Z-Lock type fasteners. The large handle gives you plenty of grip and torque when fastening studs. The precision machined blade has a radius end to fit the slot perfectly with maximum contact area. Plus, it is heat treated and zinc plated to give you a tool that will last a life time. Fits #5, #6 and #6.5 series studs.
Click for Pricing

Panel dimpling tool for race car panel fasteners.

 Our  MS-DT1  tool quickly and easily dimples sheet metal panels with the exact countersink angle for FO and FJ series flush head studs. It is made from premium tool steel and bright zinc plated for long life. A grade 8 bolt and nut complete the assembly. Fits #5, #6, and #6.5 series. 
Click for Pricing
Part Number Description
MS-7301 Spring Receptacle Adjustment Tool, for #5 & #6 Series Springs
MS-DRIVER Stud Driver for #5, #6 & #6.5 Series Z-Lock Studs
MS-DT1 Panel Dimpling Tool for FO & FJ Series - #5, #6 & #6.5 Studs

 

Z-LOCK  Grommet Flaring Tools


Flaring tools for Z-Lock Grommets are required when installing Full Flare-Type Grommets. Each series (diameter) and head style (flush or oval) requires it's own set of attachment tools.

MilSpec Z-Lock tools are a little different than the original style tools you may be use to. MilSpec has greatly improved these tools at the request of A&P mechanics because they were tired of working with the original style that did the job but, were clumsy and hard to manage. So, we improved them by adapting them to snap into a modified C-Clamp which holds them securely while the fasteners are installed. The tools work the same way as the original but, are much more mechanic friendly. The grommets can be installed quickly and easily with no more fumbling around. * The clamp is required, sold separately and will fit any attachment set. The attachments are made from premium tool steel with nickel plating for years of service. A complete set of instructions and diagrams are included with each attachment tool set.
 Pricing
Part Number Description
MS-A3C Fits Stud Type #3 Oval Head, (including wing head) Attachments Only
MS-A4C Fits Stud Type #4 Oval Head, (including wing head) Attachments Only
MS-A5C Fits Stud Type #5 Oval Head , (including wing head) Attachments Only
MS-A6.5C Fits Stud Type #6.5 Oval Head, (including wing head) Attachments Only
MS-F4C Fits Stud Type #4 Flush Head, Attachments Only
MS-F5C Fits Stud Type #5 Flush Head, Attachments Only
MS-F6.5C Fits Stud Type #6.5 Flush Head, Attachments Only
* MS-ZC Specially Modified C-Clamp Grommet Flaring Tool
(Required and Accepts All Attachment Sets)

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Simply Superior !

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