08-15-2012, 04:06 AM
Hello again Walter,
When I said judicious use of the straight line cutter, what I really meant was that I made a "roller carriage" out of skateboard wheel bearings, that located directly onto the square tubing and held a Urethane drive wheel fitted to the straight line cutter's drive pinion which gave the unit an unlimited cut length and most importantly gave good accuracy to the lateral location of each cut, something like this might be an idea for your job.
The carriage that I made was really quite basic, the main section was really just an 8mm 5/16" plate with some 8mm bolts tack welded to it to make the axles for the bearing/guide wheels of which there were four riding against the "Cut" face, two on each side of the faces adjacent to the cut face and a last single wheel on the back to keep every thing tight , I used an old rubber trolley wheel for this one as the give in the rubber was enough to provide tension without any elaborate spring systems, the torch was held by a really rough home made clamp which was attached to the carriage by a c bracket with threaded rod perpendicular to the axis of the cut face, the torch bracket itself was attached to four nuts welded together to make a really long nut so turning the threaded rod could adjust the location of the cut across the tube, my plan was to cut all of the right sides then adjust the torch position with the threaded rod gizmo then do the left sides, as it happened, I just turned the carriage around and went back the other way, without any adjustment at all.
Two points to consider;
1, the square tube will spring when cut, mine wasn't cut through the ends so was somewhat protected in this case, but having done this sort of cutting on other jobs with cutting discs, milling machines, (H & V), Oxy acetylene and Plasma, they all spring either open or closed, and it's simply due to the manufacturing stresses, I did a smaller guide rail out of 1 1/2" x 1 1/2" x 0.060" wall, that was twenty or so feet long, we cut this one using a cutting disc on a grinder, using a fence to retain accuracy, as soon as the last 1/4" of the first side was cut, the length "cork screwed" itself, this piece was also curved in a section roller to conform to a long curved concrete wall, and the piece was usable but we had to twist it into shape while bolting it in, the straight pieces usually spring open or close up on the cutting wheel as the last bit is cut through.
and finally;
2, if using plasma or Oxy, the spatter/swarf sticks to the back wall really hard sometimes, I used a strip of hardboard which eventually caught fire, but it was cheap enough, and saved a load of work, ideally a piece of thin sheet metal folded into a channel and sitting inside the square will work wonders. I suppose a piece of tough string and a couple of pulleys could automate the movement of the channel, but this is probably over kill with a capital OOO.
I hope this helps, best regards
Rick
When I said judicious use of the straight line cutter, what I really meant was that I made a "roller carriage" out of skateboard wheel bearings, that located directly onto the square tubing and held a Urethane drive wheel fitted to the straight line cutter's drive pinion which gave the unit an unlimited cut length and most importantly gave good accuracy to the lateral location of each cut, something like this might be an idea for your job.
The carriage that I made was really quite basic, the main section was really just an 8mm 5/16" plate with some 8mm bolts tack welded to it to make the axles for the bearing/guide wheels of which there were four riding against the "Cut" face, two on each side of the faces adjacent to the cut face and a last single wheel on the back to keep every thing tight , I used an old rubber trolley wheel for this one as the give in the rubber was enough to provide tension without any elaborate spring systems, the torch was held by a really rough home made clamp which was attached to the carriage by a c bracket with threaded rod perpendicular to the axis of the cut face, the torch bracket itself was attached to four nuts welded together to make a really long nut so turning the threaded rod could adjust the location of the cut across the tube, my plan was to cut all of the right sides then adjust the torch position with the threaded rod gizmo then do the left sides, as it happened, I just turned the carriage around and went back the other way, without any adjustment at all.
Two points to consider;
1, the square tube will spring when cut, mine wasn't cut through the ends so was somewhat protected in this case, but having done this sort of cutting on other jobs with cutting discs, milling machines, (H & V), Oxy acetylene and Plasma, they all spring either open or closed, and it's simply due to the manufacturing stresses, I did a smaller guide rail out of 1 1/2" x 1 1/2" x 0.060" wall, that was twenty or so feet long, we cut this one using a cutting disc on a grinder, using a fence to retain accuracy, as soon as the last 1/4" of the first side was cut, the length "cork screwed" itself, this piece was also curved in a section roller to conform to a long curved concrete wall, and the piece was usable but we had to twist it into shape while bolting it in, the straight pieces usually spring open or close up on the cutting wheel as the last bit is cut through.
and finally;
2, if using plasma or Oxy, the spatter/swarf sticks to the back wall really hard sometimes, I used a strip of hardboard which eventually caught fire, but it was cheap enough, and saved a load of work, ideally a piece of thin sheet metal folded into a channel and sitting inside the square will work wonders. I suppose a piece of tough string and a couple of pulleys could automate the movement of the channel, but this is probably over kill with a capital OOO.
I hope this helps, best regards
Rick
Whatever it is, do it today, Tomorrow may not be an option and regret outlasts fatigue.