Statement of work.pdf

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Statement of Work for Fabrication of Replacement Drive Nuts for the 300 klbf Dead Weight Machine Compression Plate

Background

NIST has maintained and operated six (6) deadweight machines (DWM’s) since 1965. Thousands of measurements, through countless force calibrations, have been performed over the lifespan of these machines. Our second largest machine has developed a problem with the compression platen positioning system. After disassembly, the problem was discovered that one of the four drive nuts was stripped and locked onto the mating shaft. As a result, a new matched set of 4 drive nuts will need fabricated and machined (the drive nuts must be the same, cannot replace just one drive nut as it will not match the other 3 in the set and cause binding issues as the wear patterns on the originals will conflict with the new gear)

SCOPE

The Contractor shall deliver four (4) bronze drive nuts.

MINIMUM REQUIREMENTS

The Contractor shall provide four (4) bronze drive nuts.

Must be SAE63 original specification, superseded as SAE927 Leaded Tin Bronze

Machine the raw stock to parameters, specifications, and tolerances per the original drawings which are provided (Figure 1 drive nut drawing)

FAO “finish all over” Note required surface finishes on drawings (125 if not noted) Decimal dimensions to be held at + 0.01” Internal thread is a modified ACME thread: 3-1/2’ - 1-5/8’ Special Form 10o

Reference to Thread Handbook (Screw Thread Standards for Federal services) H28 (1957) Part III. Page 45 and 46, Figure XIX.1 These pages are included as Figure 2.

To mate the suspension rod bottom section (piece 1 in mating rod drawing, Figure 3) lead error specified for this piece is not to exceed 0.0025”/foot.

External thread is: 4-3/4”-8N-2A

External gear data 25 teeth, 4-Diametral Pitch, 20o Pressure Angle, 6-1/4” Pitch Diameter

NIST can also supply an existing drive nut that wasn’t damaged to help in copying/measuring and fabricating the new replacements, unfortunately we cannot supply the mating external threaded rod as it is unable to be removed. Therefore, a site visit will be likely necessary to test fit the drive nuts to the threaded rod (as the rods cannot be removed from machine). This can allow for tolerance checks and fits and will allow for final adjustments to be made after visit.

INSPECTION & ACCEPTANCE

In addition to the inspection and acceptance terms articulated in 52.212-4, the Government reserves the right to perform such performance tests and evaluations as defined below to verify specified system performance. Such tests and evaluations, if performed, shall be conducted within the environment that the system is to be operated.

The Contractor has the right to be present during the tests and evaluations, if performed, at the Contractor’s expense

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Performance Tests:

NIST may choose at its discretion to forego this part of acceptance testing. A visual inspection of the equipment will be performed by the NIST TPOC to identify surface defects or any form of indication that any equipment was damaged during transport to NIST. The Government shall have sole discretion to require repair or replacement of damaged and/or nonconforming supplies at no cost to the Government. The Government at any time prior to acceptance shall reject the equipment due to defects and/or nonconformance. The vendor is responsible for latent defects discovered at any time after the final inspection. However, the extent of its liability shall be prorated over the useful life of the equipment.

Ownership of the equipment shall transfer to NIST upon acceptance by the Government.

The Government will test, inspect, and accept or reject the equipment within 10 days of the receipt of the equipment unless otherwise indicated above. The Government reserves the right to conduct quality assurance testing to confirm that a given instrument(s) meets the manufacturer’s and/or the Government’s performance specifications. It is anticipated that the equipment will meet all manufacturer’s specifications and/or the Government’s performance specifications identified in the most recent operations and maintenance manual for each piece of equipment and/or in this document.

PAYMENT SCHEDULE

Advance payment is not authorized. The Contractor must invoice in arrears according to the payment schedule.

The Contractor shall be paid, in accordance with Net 30-day payment terms, upon receipt and acceptance of a proper invoice, in accordance with the following schedule:

1. After the successful completion of the testing requirements set forth in this document under section set forth in this document, AND

2. After successful demonstration by the instrumentation that it performs IAW the technical requirements set forth in this document AND

3. After receiving an invoice submitted properly, IAW the purchase order terms and conditions.

ATTACHMENTS

Other drawings included for reference and context:

Figure 1. Drawing of bronze drive nut Figure 2. Handbook pages specifying the thread callout Figure 3. Mating rod with external screw (reference mating rod drawing) Figure 4. Assembly drawing of final application (reference assembly drawing) Figure 5. Picture of existing drive nut on machine Figure 6. example of bronze specifications

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Figure 1. Drawing of bronze drive nut

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Figure 2. Thread reference pages called out in drawing

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Figure 3. drawing of the mating threaded rod that the drive nut will turn on. (Piece 1 in drawing)

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Figure 4. Assembly drawing of drive nut on thread in the drive train.

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Figure 5. Picture of existing drive nut.

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Figure 6. example of the specified bronze