Using an angle grinder with a thin cutting disc is a popular way to cut various metal shapes. Channel, angle, round stock sheet metal, you name it and people seem to gravitate toward using a grinder to make the cut. I'm not sure why; is there some macho attraction to the sparks?

As someone who spent hours and hours for months on end using angle grinders to cut and bevel pipe I would choose any method available over an angle grinder if I could. My job then was to cut apart hundreds of feet of 3" and 4" SCH 160 316SS pipe because of changes that were being made to the system. The pipe was fabbed off site and we erected the spools, fit it all up, and welded them together. To revise the spools we cut certain joints apart per the drawings, then I ground J-bevels on all the joints and fit it all back up for welding. These all had to be fit to a consumable insert (EB Ring, named for the Electric Boat Div. of General Dynamics) and inspected by QA before you could even tack the joint up. The fit had to be within 0.016" and you used a mic to measure it and logged it on the joint record. Yup, every joint had a weld history but also info on the joint prep was recorded too. The ID had to match within 0.031". The EB Rings had a step in them to allow for a slight mismatch in the IDs of each half of the joint. The QA guy would show up with a fit gauge (I'll find mine and post a pic here) and check the profile of your J bevel all around. We usually went for a 3/32" land not 1/8" as shown below. When you passed the prep inspection you could fit up the joint and tack it, then get another inspection before you put the root in (pulled the ring) then yet another inspection before you put your hot pass on. When you fit the EB ring you drill three 1/8" holes about 120 degrees apart right through the ring so you can see inside. These holes served a couple purposes. First was a place to insert your O2 gauge so you could monitor the O2 level inside the pipe. We ran 100% Argon purge and the O2 level had to be minimal, I don't remember the amount now (40+ years ago) but less than 0.5% I believe. The other holes were so someone could 'look you in' as you pulled the ring to make sure you were consuming the ring completely and tying into both sides of the joint. If anything went wrong then it might all have to come apart and be fixed it.

Once you got the hot pass on you needed another inspection before you could weld the joint out to flush then cap it off where upon it was time for final inspection. If it passed the final visual inspection by QA/Weld Engineering then it was time for NDE, either a PT, X-Ray, or both depending on what the weld history called for. Usually I would have 3 or 4 of these joints progressing at the same time, so the Weld Engineer would inspect them all at once which saved time for everyone. We would get those joints all fit up, get the root and hot pass in, then pass the joints off to the night shift to finish out the welds. These joints were TIG welded all the way out.

Click image for larger version

Name:	05-Radii-and-Land.png
Views:	138
Size:	49.8 KB
ID:	753589

For an X-Ray welder if you had more than one joint go down in 10 you could be bumped off the list and have to re-qualify for X-Ray work. If you had too many joints go down then you would be removed the X-Ray welders list altogether. Many times working on X-Ray welds meant you'd get some OT to stay and finish the joint or would be picked to stay over and finish a weld someone else was working on and couldn't stay. That happened often as most guys were car-pooling with 2 or 3 others because of the long distances they traveled to get to the job. I had 4 guys in my gang who drove over 100 miles each way. This was over 3 hours (because of traffic congestion) on the road each way and we were working 10 hours a day for months. I don't know how they did it. Whoever wasn't driving was sleeping I guess. Made for along day.

Using a cutting disc on that heavy wall pipe (~5/8" wall thickness on 4" pipe) if you tried to cut all the way through and follow around you would burn out a disc in no time. But if you make a groove on the surface of the pipe all around then follow that making a deeper groove the disc would last much longer. For me getting maximum mileage out of a disc was important. Not because I was worried about the cost and saving the company money, it was about the long walk to the tool room to get more discs if I ran out. We didn't have electric grinders, almost all of our tools were air-powered. In the morning I would stop at the tool room and grab a couple grinders and a stack of 20 or more discs. Some were thin cutting discs and the rest were 1/8" and 1/4" wheels which were needed for grinding the J-bevels. Usually by lunch time I would be through more than half those wheels, so I would pick up more if I didn't have enough to get me through the day in my tool box. The tool room (which was a couple 45 foot semi trailers) on the job site was not close by. It took at least 5 minutes to get out of the building (climbing on scaffold most of the way) then another ~5 minute walk from the building I was working in to get to the tool room so you didn't want to make that trip in the dead of Winter or the rain if you didn't have to. When we got some Rockwell Porta-bands (the original portable bandsaw) on the job they were like gold. Everyone wanted them to use in place of a grinder where ever they could because no one liked cutting with an angle grinder and it was faster. Grinding is a noisy mess that clogs your nostrils with dust and rings your ears. No worse than a lot of other jobs out there so I'm not complaining.

Now-a-days this work is all done by machine. There are electric and pneumatic powered beveling machines to make just about any type bevel prep you need. When I was doing this work they brought a prototype beveling machine on our job and we got to play with it and feed back what was good and bad about it. It couldn't do the counterbore but machining the J-bevel it handled pretty well. It wasn't until 5 years later that I again saw one of these beveling machines on another job and this was still an early version that I would call a prototype. But a year later they were hitting the jobsite. They didn't get used on every joint but those that had to be made in place in difficult areas they were used. And later once the plant was operating you didn't want to spend any more time in there than you had to (because of the high temps and radiation) so the beveling machine got the job and our only exposure was setting up the machine and breaking it down at the end.

Granted most of that was ~40 years ago and long before anyone cared about silica dust or was fanatical about hearing protection but that's beside the point. We had no dust masks and hearing protection in the form of foam ear plugs didn't exist as I remember. Still, putting aside the negative aspects and logging hundreds of hours on an angle grinder you pick up on some tricks. One of them is how you make a cut matters with respect to longevity of that cutting disc as shown in this video by Fireball Tools.

OK I rambled enough, watch the video. :-)
​​​​​​​