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MS21042 Style B Jetnut, All Metal Locknut

Click for a larger picture of MS21042 Style B Jetnut, All Metal Locknut
View Catalog Page in PDF format

If you prefer the original style (which allow easier wrench access), we still have some available in -3, -4 and -5 sizes. They are about 40% less expensive.

MS21042 Jetnuts (Kaynuts) are all-metal, self-locking nuts. They are rated at 160,000 psi tensile strength and can withstand temperatures to 450°F. Because of their reduced hex dimension, they are widely used in limited space applications where wrench access is a problem.

Jetnuts are also lighter than AN365 Nylon Lock Nuts (an average of 63% lighter for -3 through -6 sizes). Replacing all of the AN365 nuts on your racecar with MS21042 jetnuts can result in a measurable weight savings!

These are the latest "Style B" specification, with a slightly thicker flange which reduces the likelihood of splitting due to nut dilation (especially if over-torqued). Plated mild steel construction; some lots have a moly lubricant coating over the plating at the manufacturer's discretion (sorry, no choice on our end). Plating color may vary from photo. Sold individually.
 

MS21042 Specifications
Dash No. SAE Thread Hex Size* Outside
Diameter
Height
(Max)
04 4-40 5/32" 0.206" 0.125"
06 6-32 3/16" 0.244" 0.141"
08 8-32 7/32" 0.290" 0.188"
3 10-32 1/4" 0.330" 0.188"
4 1/4-28 5/16" 0.420" 0.219"
5 5/16-24 3/8" 0.520" 0.266"
6 3/8-24 7/16" 0.620" 0.282"
7 7/16-20 1/2" 0.708" 0.328"
8 1/2-20 9/16" 0.814" 0.410"
10 5/8-18 3/4" 1.014" 0.550"


* The hex is typically deformed to produce the self-locking action. An unused nut may appear to have one hex dimension smaller than the others before installation.

Looking for metric sizes? We also offer (non-milspec) Metric Jetnuts which have similar temperature and strength ratings.

Reusing Locking Nuts
The FAA has issued guidelines on the reuse of locking nuts. Specific recommendations have been published for larger sizes (7/16-20 and up), but the general rule is that you should not be able to turn the nut by hand once the locking portion engages the male threads. If you can turn the nut with your fingers, it must be replaced. When in doubt, replace!

98%
of respondents would recommend this to a friend

Enter desired order quantities below, then click the "Add selected quantities to cart" button.

Order Qty
Part No.
Desc.
Price
Stock Status

MS21042-04
Condition: New
SKU: 52845

4-40 Jetnut, All Metal Locknut

1 to 11: $0.79 

12 to 149: $0.73 

150 & up: $0.66 

In Stock

MS21042-06
Condition: New
SKU: 47810

6-32 Jetnut, All Metal Locknut

$0.43
In Stock

MS21042-3
Condition: New
SKU: 33672

10-32 Jetnut, All Metal Locknut

$0.43
In Stock

MS21042-4
Condition: New
SKU: 33673

1/4-28 Jetnut, All Metal Locknut

1 to 11: $0.64 

12 to 149: $0.59 

150 to 1999: $0.54 

2000 & up: call    

In Stock

MS21042-5
Condition: New
SKU: 33674

5/16-24 Jetnut, All Metal Locknut

1 to 9: $1.19 

10 to 99: $1.09 

100 to 999: $0.99 

1000 & up: call    

In Stock

MS21042-6
Condition: New
SKU: 33675

3/8-24 Jetnut, All Metal Locknut

1 to 9: $1.29 

10 to 99: $1.19 

100 & up: $1.09 

In Stock

MS21042-7
Condition: New
SKU: 33676

7/16-20 Jetnut, All Metal Locknut

1 to 7: $4.69 

8 to 59: $4.30 

60 to 499: $3.91 

500 & up: call    

In Stock

MS21042-8
Condition: New
SKU: 33677

1/2-20 Jetnut, All Metal Locknut

1 to 7: $5.39 

8 to 59: $4.94 

60 to 499: $4.49 

500 & up: call    

In Stock

MS21042-10
Condition: New
SKU: 48469

5/8-18 Jetnut, All Metal Locknut

1 to 5: $24.99 

6 & up: $23.60 

In Stock
 

Review Snapshot

by PowerReviews

4.8

44 ReviewsWrite a Review
98%
of respondents would recommend this to a friend

Ratings Distribution

Most Liked Positive Review

Great Value, Great Fastener!

I use these nuts for my TiAL wastegate vband clamps. The clamps come with really small locking nuts just like these Jetnuts, but their locking ability is lacking. The TiAL supplied nuts had eventually gotten loose after a few times removing and reusing them. They are made of a plated copper and aren...

Versus

Most Liked Negative Review

i would buy this but I like the old ones better

There is a bump on the surface so your socket can't grip them as good as the original ones

Reviewed by 44 customers

I have bought many different sizes of these and work great

Submitted 9 months ago

By Sean K

From Fresno , Ca

Verified Buyer

Comments about Product

I use this type for the race cars that I rebuild. Great selection and always work great for my application.

Comments about the Service

My orders are always processed very quickly. I have had some issues with me ordering the wrong parts and customer service has always helped me in the right direction.

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Hardware

Submitted 9 months ago

By Kent S.

From Florida

Verified Buyer

Comments about Product

Great product, holds firmly no worries of bits working apart.

Comments about the Service

Always excellent service, no issues what so ever.

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Fast service! Fast shipping! Always in stock!

Submitted 10 months ago

By James R.

From Sequim, WA

Verified Buyer

STD aircraft part.

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Great place to shop whether a racer or enthusiast

Submitted 1 year ago

By Mark O

From Florida

Verified Buyer

I order from Pegasus because it's easy, they have it and it's shipped fast 2-3 days

User submitted media

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Buy again

Submitted 2 years ago

By Chris X

From Maryland

Verified Buyer

Comments about Product

Limited special use on a race car

Comments about the Service

Good delivery

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Great product

Submitted 3 years ago

By DWC

From Adirondacks USA

Verified Buyer

Comments about Product

Will depend on these to hold the wheel adapters on my race car!

Comments about the Service

Quick delivery.

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Lock nut... by who's standards ?

Submitted 3 years ago

By Ken R

From orlando fl

Verified Buyer

Comments about Product

The lock nut torque value is ok on about 60% of these nuts. The rest, you can just about turn them with your fingers. Not a lock nut.

Comments about the Service

service was quick

Merchant Response

This review refers to Part No. MS21042-08 (8-32 thread size). These nuts are made to stringent military specifications and undergo extensive quality control testing throughout the manufacturing process. If the screws on which they are used are not also made to military specifications, undersized male threads may contribute to lower retention torque. We would like to receive a few samples of nuts that seem to have low retention torque so that we can return them to the manufacturer for testing.

Bottom Line No, I would not recommend to a friend

Was this review helpful to you?

I would buy this again, good product!

Submitted 3 years ago

By Scott

From Okemos MI

Verified Buyer

good quality

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Nice to find the right hardware

Submitted 3 years ago

By Jeff Werth

From Campbellsport, Wi

Verified Buyer

When you are dealing with brake systems, precision is key

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

why jetnuts

Submitted 3 years ago

By Kurt L

From Fort Worth Tx

Verified Buyer

Comments about Product

I needed a strong but light nut for some suspension attachment bolts. the nuts are installed within a lighten recess attachment that a wrench and regular socket were not able to be used. the reduced wrench feature of the jet nut made the smaller socket size a perfect application for a secure and tight fit.

Comments about the Service

delivery as on time and all ordered parts were delivered as requested.

Bottom Line Yes, I would recommend to a friend

Was this review helpful to you?

Reviewed by 44 customers