in Vol. 6 - May Issue - Year 2005
It's Just A Holder...
Whoever is into shot peening, has to deal with Almen strip holders in one way or another. A customer expects rightfully to have no problems with such products. However, depending on use, a holder has to fulfil certain specifications and quality differences can be significant.
Almen Strip Holder according J442
If one is doing peening for the aviation industry, it is very likely that Almen strip holders according to the J442 are required. This specification belongs to the SAE (The Engineering Society For Advanced Mobility Land, Sea, Air and Space) and specifies test strips, holders and gages for shot peening.
In the case of the holders it defines the material, its hardness, dimensions as well as the position and size of the screws.
Abrasive Resident Screws
For the German company Peening Accessories GmbH, it was not just important to fulfill the J442, but also to offer a holder which can fulfill all the customers needs. Since holders are used in a very abrasive surrounding, the durability of the screws which are used to hold the strip in position is of great importance. Depending on the make of the screws, a user might have to exchange them every time an Almen test is carried out. This can be very time consuming since little pieces of shot may also get stuck in the thread so the thread of the holder has to be recut. After spending months looking for the right material and doing a number of tests, a screw was found, which can last in an abrasive surrounding for a very long time. It is custom made for Peening Accessories. The tests were carried out with a cut wire size of 0.8 mm. This larger size of cut wire is very abrasive, but ideal to simulate extreme conditions. The nozzle was placed 100 mm away from the screw in a still position for a duration of 60 seconds. The result speaks for itself. While other screws showed obvious signs of destruction, the Peening Accessories screws hardly showed any wear.
Besides the abrasive resident screws, the holders come with the following finish:
- the two main surfaces are polished
- lot number for identification- all edges receive a 45° grinding
- corrosion protection
- individual packing
- on request J442 certificate of compliance