DIY Oxy-Acetylene Profile Cutter

Editor's Note: CR4 would like to thank Johan van Niekerk for sharing this DIY story and picture. Many thanks, Johan!

I have never had a steady hand with a cutting torch, and felt that this was a problem with which I needed some help. Then one day, I stumbled upon a 12-volt motorcar windshield-wiper motor, and a round cylindrical magnet that was about 50-mm in diameter and 50-mm long. I knew then that I had to make my own profile cutter!

The picture below shows how my profile cutter looks now. No template is shown, but the follower is positioned on the template bracket to indicate how it works.

The principle is simple and works well. The electrical motor drives the magnet (which has a small wheel on top; the Allen screw-head that fixes it to the shaft) and follows a metal template. A pivoting, hinged arm allows the magnet to follow any contour. A cutting nozzle below the follower cuts the metal to the shape of the template.

Looking around, I found a 30-mm round steel-bar, about 600-mm into which I cut a square thread on almost the whole of the shaft, except for 100-mm in the middle. On this section, I cut two grooves about 50-mm apart for steel ball-bearings to run on.

A piece of hollow bar (100-mm in diameter and 100-mm long) was turned to an internal diameter that would accommodate 3-mm steel ball-bearings and allow the hollow bar to rotate easily, but without play on the shaft. A second piece of hollow bar of these same dimensions was machined to fit closely over the 30-mm shaft's square threaded section. Five nuts were made to run on the square thread of the shaft.

Next, a 40-mm square tube was used to make a pivoting arm. The pivot of the arm is made to pivot to one side only, to prevent the arm from locking in the straight position. One side was welded to the hollow bar with the ball bearings. The other side was welded to a metal box I made from 2-mm steel plate to take the electrical motor. There is also a 25-mm round bar which I drilled and machined to take two bearings contained by a Circlip. It holds the shaft on which the magnet was mounted and fixed by a 10-mm Allen cap screw.

On the second piece of hollow bar, I welded a 30-mm square tube which has a 25-mm square tube-extension inside, locked by a 10-mm screw in a nut welded on the larger tube. On the end of the 25-mm tube, a piece of 50-mm angle iron is welded with some holes onto which the template is bolted.

A piece of 12-mm plate (200-mm square) makes the foot of the stand and gives it some weight. One nut was welded onto this in the middle, after making a hole for the shaft to pass through. Four 12-mm holes were drilled and tapped to take four set screws for adjusting the plate.

A variable-voltage power supply was made to control the speed of the motor. A triple- throw, double-pole toggle switch was used to switch the motor on and off, and forward and reverse. The power supply contained in a mettle box is mounted opposite the arm on the pivot point, and used as a counter balance for the arm.

Two pieces of the hollow bar were machined to about 20-mm long to fit over the shaft. They were kept in place by a grub screw on both sides of the pivot, to position the pivot on the shaft over the two ball-bearings. The lower piece was grooved to take 3-mm balls as a thrust bearing.

I found the cutting nozzle from a discarded straight-line cutter, which I mounted with the nozzle directly under the centre of the magnet. An O-ring is used to drive the magnet from the motor.

The height of template arm is adjustable by two nuts on both sides running on the square thread. I drilled 10-mm round holes in the nuts on the flats to use a piece of round bar for tightening and loosening the nuts. This saves on using a huge spanner for the job.

Maybe my profile cutter isn't a five-star job, but it works well, gave me much pleasure to make, and saved me plenty of money.

Editor's Note: Do you have a DIY story to share with CR4? If so, please message Moose or frankd20. We'd like to hear from you!