Quality Services: FAQs

As a calibration laboratory concerned with helping you maintain and understand how to best care for your gage blocks, we have compiled the following list of commonly asked questions with answers. Usually you will find an answer to your gage block questions here. If not, please call. We will be most happy to answer your individual questions.

Question 1:

What is the difference between a long form and short form certification?

Answer:

Many calibration labs and gage manufacturers offer a simple statement with their work that indicates that the gages meet their requirements or comply with some standard. No actual values for each gage member or block are provided. Often a SI traceability number may be included. This type of “certification” is often called “Short Form Certification”.

We do not provide the Short Form Certification because it does not provide the necessary information required by MIL-STD 45662A and ISO Guide 25. These standards are explicit in their requirements for actual values, conditions of calibration, equipment and masters used, and SI traceability among other requirements. We will only provide you with a certification that meets the full requirements of ISO Guide 25 and MIL-STD 45662A at no additional cost.

Question 2:

Why should I have new blocks calibrated before use?

Answer:

Some gage manufacturers do not offer proper certifications or SI traceability when you buy sets of gage blocks. Do not be fooled, a set of gage blocks may not be properly calibrated or accurately calibrated just because they are new.

Gage blocks are often made far in advance of sale. This is especially true of imported gage blocks.

During the time that has transpired between the manufacture and delivery of the set to you, as much as a year’s times may have passed. During the year temperature changes and storage may have caused the blocks to change size to the point that the values the blocks had at manufacture are not now the same.

Additionally some countries who are major exporters of gage blocks are not involved in proper programs of standards exchange with SI to be able to provide you with proper SI traceability by agreement.

Question 3:

How often do I need to have my gage blocks recalibrated?

Answer:

The answer to this question is one of the long standing issues of metrology. The period of time between calibrations must be determined by you, the user, based upon many different considerations such as degree of use, conditions of use, conditions of storage, and handling practices. As a starting point we offer the following suggestions:

Grade 0.5 and Grade 1.0 – Annually

Grade 2.0 – Semi-Annually or Annually

Grade 3.0 – Semi-Annually or Quarterly

Question 4:

How long does calibration take?

Answer:

Normal turnaround will be 10 to 15 days after receipt based on the grade of the blocks to be calibrated. We require time to properly clean, demagnetize, and stabilize gage blocks prior to calibration.

Question 5:

Is there a best time to send my blocks in for calibration?

Answer:

Our busiest times of the year are March to May and July to October. In order to obtain the fastest response, send your blocks to us during other times of the year. Normal turnaround will be 10 to 15 days after receipt based on the grade of the blocks to be calibrated. This allows time to properly clean, demagnetize, and stabilize gage blocks prior to calibration and also allows time for rechecks during calibration.

Question 6:

How should I package my blocks for shipment to you?

Answer:

As we all know gage blocks are expensive and you will want to do all that you can to see that they are properly packaged and shipped. Best method for packaging and shipping includes these points.

Lightly lubricate steel blocks with a good light oil such as Starrett M1.

Place a sheet of wax paper inside the box over the blocks.

Place sheets of soft pliant packaging materials or paper towels over the wax paper to insure that the blocks are unable to move in the box during shipment.

Seal the gage block box with reinforced tape. Don’t depend on the box latch to hold during shipment.

Wrap the gage block box inside bubble pack or similar cushioning material so that the box is protected on all sides by at least two inches of packaging material.

Place this into a strong box with enough additional packaging materials to withstand shock in transit to us.

Question 7:

What tolerances do you use and how do you determine if a block is good or bad?

Answer:

The existing specification used to define tolerances for gage blocks is stated in the current Federal Specifications and ANSI B89.1.9. Flatness, parallelism, and size of a gage block is checked for conformance with these specifications. If the block fails to meet these requirements, we consider the block to be bad.

Question 8:

Can you rework worn or damaged blocks in my set?

Answer:

Only if you instruct us to do so on your order. We will contact you with information about any bad blocks we find prior to returning them to you. At that time we will also provide you with cost for replacement blocks. If you wish, we will replace them and update your block set certification.

Question 10:

Can you rework worn or damaged blocks in my set?

Answer:

The actual worth of the material in a gage block is very small. It is not economically feasible to rework blocks that are worn or damaged. The extra work to convert a bad block to a good block would cost far more than to buy a new one.

Question 11:

Since you check flatness and parallelism, will you include that information on my certification?

Answer:

If you need actual values reported for flatness and parallelism, we will gladly provide that information on an additional certificate at extra cost.

Question 12:

Can you check a set of blocks to a tighter grade level and certify them to that tighter grade?

Answer:

Gage blocks are graded according to size, flatness, and parallelism. Unfortunately, the accuracy of a gage block set cannot be changed by calibration.

Question 13:

What is the accuracy of the calibration of a gage block set that I would send to you?

Answer:

The accuracy depends on the size, grade, parallelism, flatness, and surface condition of each block in addition to the equipment used and human factors involved. New sets can be calibrated to the accuracies stated in ANSI B89.1.9. Used blocks, however, may have uncertainties of measurement as high as 5 micro inches per inch or .13 micrometers per 25mm.

Question 14:

What equipment will you use to calibrate my set?

Answer:

Calibrations are performed by utilizing dual opposed transducer comparator systems. Measuring pressure is 2 ounces. Blocks are allowed to stabilize a minimum of three days prior to measurement. Blocks are moved by use of plastic tongs so that body heat is prevented from disturbing the blocks. Blocks are checked for temperature prior to measurement. Any temperature deviation between block and master are recorded and corrected.

Tool & Gage House Quality Services Departments