Allen Timmons We will often get requests for wire of a specific length that has a diameter that is not in stock. When this happens we could procure some additional material through our supply chain but this could result in a lead time longer than the customer is willing to wait. In addition, we may not be able to locate a specific diameter of the material the customer is requiring. Often this is because the diameter is not a standard size.
In these cases, we can centerless grind. This can apply for any material, i.e., Music Wire, OTMB, and Stainless. We will first find a wire diameter that we have in stock that is slightly larger in diameter and of the same material. As an example, let’s say the customer requires .224” Music Wire, S&C 10 ft. We might select .226” Music Wire. We would first straighten and cut the .226 to 10 ft. Then using one of our centerless grinders, we would grind off .002” from the diameter along the entire 10 ft. piece.
The grinding time and cost is a function of the amount of material to be removed, the tolerance, finish and the length of the part. So continuing with our example, if we only have .230 Music Wire in stock, this would require us to remove .006” off the diameter. This would generally take two passes on the centerless grinder. In other words, we would pass the entire 10 ft. part through the centerless grinder one time to remove some of the material, then have to pass it through again to remove the remaining material. Obviously, this would take more time and of course the selling price would have to reflect this increase. Conversely, if the wire was only 5 ft. in length, the amount of time to pass through the centerless grinder would be less and the price would be less.
We do our very best to keep a large inventory of material so that we can minimize the amount of material we may have to remove in order to keep the cost down and be competitive.
Please note, we cannot centerless grind any wire in a coil or that has not been straighten – it must be straighten and cut first and to tight straighten tolerances.
Our centerless grinders can meet +/-.0002” tolerance and surface finish specifications from 5 – 16 Ra with 5 being very fine. We find that most wire has an existing surface finish of > 25 Ra which is usually acceptable for most applications. We use Profilometers to measure surface roughness (Ra) and Laser Mics to measure diameter. The Laser Mics can measure up to +/-.00001”. We can centerless grind up to 20’ in length.
This centerless grinding process requires machine operator expertise and experience as there are many machine parameters that have to be set, monitored and adjusted. First piece and pieces produced during and at the end of the process would be tested for customer conformance using the Profilometers and Laser Mic.
