Exhibit 4.8



PRECISION CASTPARTS CORP. AND        THE GUARANTEEING SUBSIDIARY        TO        J.P. MORGAN TRUST COMPANY, NATIONAL ASSOCIATION        as Trustee

---

FOURTH
SUPPLEMENTAL INDENTURE

Dated
as of March 22, 2005



---





FOURTH SUPPLEMENTAL INDENTURE

Fourth Supplemental Indenture (this "Supplemental Indenture"), dated as of March 22, 2005 among Air
Industries Company, LLC, a California limited liability company (the "Guaranteeing Subsidiary"), a subsidiary of Precision Castparts Corp. (or its
permitted successor), an Oregon corporation (the "Company"), the Company, the other Guarantors (as defined in the Indenture referred to herein) and J.P.
Morgan Trust Company, National Association (as successor to Bank One Trust Company, N.A., which was successor in interest to The First National Bank of Chicago), as trustee under the Indenture
referred to below (the "Trustee").

W I T N E S S E T H

WHEREAS,
the Company and the other Guarantors have heretofore executed and delivered to the Trustee an indenture, dated as of December 17, 1997, as amended by indentures
supplemental thereto (the "Indenture"; which term as used herein includes the Second Supplemental Indenture dated December 9, 2003, establishing
the title, form and terms of $200,000,000 aggregate principal amount of the Company's 5.60% Senior Notes due 2013 (the "Notes"));

WHEREAS,
the Indenture provides that under certain circumstances the Guaranteeing Subsidiary shall execute and deliver to the Trustee a supplemental indenture pursuant to which the
Guaranteeing Subsidiary shall unconditionally guarantee all of the obligations of the Company under the Notes and the Indenture on the terms and conditions set forth herein (the
"Note Guarantee"); and

WHEREAS,
pursuant to Section 901 of the Indenture, the Trustee is authorized to execute and deliver this Supplemental Indenture.

NOW
THEREFORE, in consideration of the foregoing and for other good and valuable consideration, the receipt of which is hereby acknowledged, the Guaranteeing Subsidiary and the Trustee
mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

1.Capitalized Terms.    Capitalized terms used herein without definition shall have
the meanings assigned to them in the Indenture.

2.Agreement to Guarantee.    The Guaranteeing Subsidiary hereby agrees as follows:



1

---





3.Execution and Delivery.    Each Guaranteeing Subsidiary agrees that the Note
Guarantees shall remain in full force and effect notwithstanding any failure to endorse on each Note a notation of such Note Guarantee.

2

---



4.Guaranteeing Subsidiary May Consolidate, Etc., on Certain Terms.    The
Guaranteeing Subsidiary may not sell or otherwise dispose of all or substantially all of its assets, or consolidate with or merge with or into (whether or not such Guaranteeing Subsidiary is the
surviving Person) another Person other than the Company or another Guarantor, unless:



In
case of any such consolidation, merger, sale or conveyance and upon the assumption by the successor Person, by supplemental indenture, executed and delivered to the Trustee and
satisfactory in form to the Trustee, of the Note Guarantee endorsed upon the Notes and the due and punctual performance of all of the covenants and conditions of this Indenture to be performed by the
Guaranteeing Subsidiary, such successor Person shall succeed to and be substituted for the Guaranteeing Subsidiary with the same effect as if it had been named herein as the Guaranteeing Subsidiary.
Such successor Person thereupon may cause to be signed any or all of the Note Guarantees to be endorsed upon all of the Notes issuable hereunder which theretofore shall not have been signed by the
Company and delivered to the Trustee. All the Note Guarantees so issued shall in all respects have the same legal rank and benefit under this Indenture as the Note Guarantees theretofore and
thereafter issued in accordance with the terms of this Indenture as though all of such Note Guarantees had been issued at the date of the execution hereof.

Except
as set forth in Articles 8 and 10 of the Indenture, and notwithstanding clauses (a) and (b) above, nothing contained in this Indenture or in any of the Notes shall
prevent any consolidation or merger of
the Guaranteeing Subsidiary with or into the Company or another Guarantor, or shall prevent any sale or conveyance of the property of the Guaranteeing Subsidiary as an entirety or substantially as an
entirety to the Company or another Guarantor.

5.Releases.



3

---





6.No Recourse Against Others.    No past, present or future director, officer,
employee, incorporator, member, stockholder or agent of the Guaranteeing Subsidiary, as such, shall have any liability for any obligations of the Company or any other Guarantor under the Notes, any
Note Guarantees, the Indenture or this Supplemental Indenture or for any claim based on, in respect of, or by reason of, such obligations or their creation. Each Holder of the Notes by accepting a
Note waives and releases all such liability. The waiver and release are part of the consideration for issuance of the Notes. The waiver may not be effective to waive liabilities under the federal
securities laws.

7.NEW YORK LAW TO GOVERN.    THE LAW OF THE STATE OF NEW YORK SHALL GOVERN AND BE
USED TO CONSTRUE THIS SUPPLEMENTAL INDENTURE.

8.Counterparts.    The parties may sign any number of copies of this Supplemental
Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

9.Effect of Headings.    The Section headings herein are for convenience only and
shall not affect the construction hereof.

10.Trustee.    The Trustee shall not be responsible in any manner whatsoever for or
in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Guaranteeing Subsidiary and
the Company.

[Signature
page follows.]

4

---



IN
WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed and attested, all as of the date first above written.

| |  | AIR INDUSTRIES COMPANY, LLC                                
| |  | -----------------------------------------------------------
| |  | By:                                                        
| |  | PRECISION CASTPARTS CORP.                                  
| |  | By:                                                        
| |  | J.P. MORGAN TRUST COMPANY,
NATIONAL ASSOCIATION,
AS TRUSTEE
| |  | By:                                                        

5

---





NOTATION OF GUARANTEE

For value received, the undersigned Guarantor (which term includes any successor Person under the Indenture) has, jointly and severally, unconditionally
guaranteed, to the extent set forth in the Fourth Supplemental Indenture, dated as of March 22, 2005, among Precision Castparts Corp., undersigned Guarantor and J.P. Morgan Trust Company,
National Association (successor in interest to Bank One Trust Company, N.A., which was the successor in interest to the First National Bank of Chicago), as trustee (the
"Trustee"), and subject to the provisions in the Indenture dated as of December 17, 1997, as amended by indentures supplemental thereto (the
"Indenture", which term as used herein includes the Second Supplemental Indenture dated December 9, 2003, establishing the title, form and terms
of $200,000,000 aggregate principal amount of the Company's 5.60% Senior Notes due 2013), among Precision Castparts Corp., the other Guarantors (as defined in the Indenture) and the Trustee,
(a) the due and punctual payment of the principal of, premium, if any, and interest on the Notes (as defined in the Indenture), whether at maturity, by acceleration, redemption or otherwise,
and the due and punctual payment of interest on overdue principal, premium, if any, and interest on the Notes, if lawful (subject in all cases to any applicable grace period provided therein), and the
due and punctual performance of all other obligations of the Company to the Holders or the Trustee, all in accordance with the terms of the Indenture and the Notes and (b) in case of any
extension of time of payment or renewal of any Notes or any of such other obligations, the same will be promptly paid in full when due or performed in accordance with the terms of the extension or
renewal, whether at stated maturity, by acceleration or otherwise. The obligations of the undersigned Guarantor to the Holders of Notes and to the Trustee pursuant to the Note Guarantee and the
Indenture are expressly set forth in Article Fourteen of the Indenture and reference is hereby made to the Indenture for the precise terms of the Note Guarantee. Each Holder of a Note, by accepting
the same, (a) agrees to and shall be bound by such provisions and (b) appoints the Trustee attorney-in-fact of such Holder for such purpose.

[Signature
page follows.]

6

---



IN
WITNESS HEREOF, the undersigned Guarantor has caused this Notation of Guarantee to be signed manually or by facsimile by its duly authorized officer.

| |  | AIR INDUSTRIES COMPANY, LLC,
a California limited liability company
| |  | -------------------------------------------------------------------
| |  | By:                                                                

7

---



QuickLinks