One might think this material really doesn’t need explaining but you would be astonished if you had seen people over time, destroy the work piece as I have seem them do.
First let’s establish what we are grinding for the purpose of this article. I want to focus on anything metal. Plate, pipe, iron, stainless, metal of any kind. I had the privilege of working with some of the most skilled fitters over the last quarter century. I was fortunate enough to pick up on their skills that helped me in my own career as a welder.
One of the things I learned early on was to use the proper tool for the job at hand. There is no need to use a seven inch grinder for a one inch pipe. Of course, that is an extreme example but proves the point.
When grinding there is not only proper tool consideration but also safety elements to ponder. Let us consider first the proper tool for the job.
There are air grinders as well as electric grinders. Most situations will call for right angle electric grinders that work off of alternating current (ac). This is the common household or construction type grinder that is purchased from most hardware stores all over America. I can not speak for countries outside of the United States. For normal service a four and a half inch electric model will be adequate. The next size up is a five inch that is designed for more industrial type service. After this is the six inch, 7″ and the 9″. A great all purpose grinder that can handle both light and heavy applications is the 5″ Makita model. I personally owned two Makita 5″ and modified the safety guard so it would fit a 7″ wheel.
The reason for this modification was for better coverage when grinding and longer lasting wheel life.
Now Makita makes a 6″ and a 7″ grinder but at the time I bought mine they did not offer those sizes. When working with metal the size of the work piece has impact on deciding what tool to use.
When grinding for speed to move through hardened materials or materials that are relatively thick, it is best to choose a wheel that can hold up to severe load requirement. Usually a grinding wheel with a thickness of quarter inch is suitable.
When grinding on materials that are non hardened and not over 3/8″ thick, I would prefer a 1/8″ thick wheel. The lighter thickness wheel is easier to control as well. This wheel is perfect for surfacing a bevel on a pipe material, whether hardened or not. When I say hardened I am referring to metal such as stainless materials.
Technique in grinding is extremely important when approaching the actual application of the grinder as it comes in contact with the material. When using the right angle grinder the wheel should not dig into the work piece when making contact unless a groove cut is desired. The ideal contact point on the grinding wheel is about an 1/8″ of an inch back from the edge of the wheel. This can not be accomplished when digging the edge of the wheel into the work element. The wheel therefore must be laid more flat to the surface of the work piece. Laying the wheel surface to the work in this way will allow for more control and transition in the actual grinding.
When grinding on a round surface such as pipe, it is better to go even further in on the grinding wheel toward the center of the wheel. This will ensure better control over a bevel approach. Keeping the wheel slightly inclined on the surface of the pipe until the desired bevel angle is achieved.
When working with pipe, this beveling approach will give a more factory type surface when grinding as if a machine put on the pipe bevel edge. Moving the wrists from side to side or front to back keeping the proper angel of the grinding wheel will give a better overall finished surface. Most of the time an experienced worker will have access to torch beveling machines that can cut the initial bevel before grinding.
When cleaning up this type of cut on the pipe there is no need to really work the bevel since it has been cut into the surface of the material. When cutting on plate or pipe that is not beveled more work will be needed.
Inside of the pipe has a different type of grinding abrasive that is used called a cone rock. We will save that for another article. Be careful as you near the portion of the bevel where the outside of the pipe surface is reached as to not dig into the outer pipe surface reducing the size of the outer dimension of the pipe. Take your time and do the job correctly the first time.
Please bear in mind that safety glasses, grinding shields, ear plugs, and guards are all put in place with the purpose of protecting the eyes, ears, and face from dangerous metal shavings that can run the individual for a lifetime of hurt in a moment of time.
Check out DVDs that demonstrate the techniques in my articles at http://www.thewelderslens.com