Rotation fixture to rebuild worn pins - cheap but effective solution — Machinery, page 2

treemuncher · 2024-12-24T02:01:21.000Z

I have a couple of pins that my tracked mulcher cutterhead rides on. There are outer bushings that roll on these pins in the center portion of the pins. These bushings ride up and down an elongated slot on each side of the mounting frame to allow the head to contour to the grade. This mount allows about 15-20 degree difference in the machine's track angle vs head angle and allows a much better ground contouring cut. It is a custom design that I built to reduce the amount of stress on the carrier, unlike the OEM fixed mount version. I borrowed the design idea from the FTX140 that I used to run. The pins take a lot of hammering and abrasive wear from the bushings as dirt gets in and mixes with the grease. The bushings get hammered out of shape from all of the shock loading - eventually I need to see about getting these heat treated to last longer but they are cheap enough and easy to make on the lathe. They are made from DOM steel and easy to source. This recent change out had the usual hammered bushings but the pins were wore down close to 0.250" in the worst areas. New bushings were not going to seal well while new with this kind of slop and they will get hammered out/distorted much faster. I either need to build or repair the pins to make the repairs last for a while. Making new pins is easy enough with the lathe and welder but this time I decided to try building up the worn areas with weld and then cutting back down to size on the lathe. New pin stock has become quite expensive and I thought I should try something new to rebuild the surface and make the pin surface harder. I had an idea in mind to use some old componets that I had kicking around to make a part turning fixture with an adjustable speed controller. I have needed one on several occasions so I got to thinkin'. I wanted cheap - just about everything built from stuff already on hand. Nothing permanent - just a clamped up fixture I can use anytime. Nothing fancy - no bearings to ride in, just vee blocks with oil and a strap to keep the rotor held in place. Something fast - I cobbed this up in about 2 hours making the custom shaft bushings and mounts. I already had a 90vdc motor with an angled speed reducer output and a variable speed controller with 120vac input/ 90vdc output. I purchased this on a fixture at an industrial auction in the early 90's - time to put it to work. I also had a small timing belt drive with 1 large and 1 small sprocket, each with taper-lock bushings, that were ordeded as a set really cheap from a surplus site 15-20 years ago for another project. I custom cut the bushings I needed to make the sprockets work on the shafts that I had. A slight clamp action is good enough for this low speed, low torque application so no need to worry about keyways or perfect fits. The timing belt assures positive drive without the need for a tight belt - simple and smooth solution for rotation. For the shaft bearing blocks, I cut a couple of vee blocks out of wood on the radial arm saw. These vee blocks were stapled down to a scrap of shipping plywood for a base. I used a scrap piece of aluminum as one of the vee block locks which also works as a sliding ground while welding the rotating part. The other lock down was just a piece of heavy copper wire with adjustable pressure via screw depth. The plywood base gets clamped to the welding table with the driven gear overhanging. The drive arbor is a 1" bolt tack welded to the end of the worn pin. A plastic bushing keeps any heat or electrical continuity from the shaft to the gear. I bolted down the motor output to a scrap piece of 5/16" steel and that steel plate is clamped down to the welding table at proper alignment of the sprockets and proper belt tension. Easy on, easy off and adjustable for different sizes as needed. Just what I wanted. Once I started welding on the shaft, I realized that a mig gun holder would make it so much easier and much more consistent overlays. I had some extra 1.5" Ram ball mounts so I cut a mig tip holder from some 1" black iron pipe and attached that to one Ram ball. The other ball was mounted on the inside of a vee block. This made for very consistant beads with the holder. Freehand laid up beads not as good as the beads done with the holder. Not 100% coverage on the build up but near the same as a new pin with even more grease retention area. Good enought to put it back together and see if the pins hold up after being welded on. Pins were preheated to 200-250 degrees before weld passes were made. New bushings fit perfectly over reworked areas of the pins. Hopefully, this idea will help others. Some fixtures don't need to be fancy to work just fine!

treemuncherSenior MemberDec 14, 2025#21

Welder Dave said: A ground clamp attached to a flat strip of copper wraped partly around a smooth clean shaft will work for a ground where the piece needs to turn. I saw it being used on a lathe when welding high pressure stainless oil sample cylinders. A wire feeder motor and control was used to turn the lathe real slow. Some people use braided copper like some cars have for ground cables. Click to expand... Great idea but this steel wheel was running on nylon (plastic) bushings. That's why I did not try to ground via the axle, vise or table. I had to have something that could rotate while attached direct to the parts on this project. After watching this video here: I knew that I could bypass the whole start of this process with an old brass rotating fixture that I saved from a pressure washer reel and still make up the rotating ground fixture out of the old part. Problem was that I could not locate the saved parts, so I used the fitting instead to get by on this one time. I'll make up the ground fixture when I run across the part again. Cleaning up the shop has gotten it temporarily misplaced. If you have not seen any of Kurtis's videos, you need to check out his channel at https://www.youtube.com/@CuttingEdgeEngineering I learn more every time that I watch something that he and his wife have put together.

Reply