Rotation fixture to rebuild worn pins - cheap but effective solution

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!

treemuncher said: They are made from DOM steel and easy to source. Click to expand... You mean they are hollow? DOM means "Drawn over Mandrel". What do these go to?

SLK001 said: You mean they are hollow? DOM means "Drawn over Mandrel". What do these go to? Click to expand... The DOM bushings ride over the solid pin (the part I built back up) and ride up and down the slotted holder on the end of the H frame that connects the carrier to the head. There are two of these slotted mounts. The picture below is of the original fixed mount that I cut off of the H frame (round with brass bushing) and the welded on part is the updated mount that I made that is slotted to allow vertical movement of the cutterhead. This pic was taken with the H frame off of the machine and in the shop while I was doing the retrofit work. The ends of the pins fit into round mounts on the cutterhead. Waterjet cut slot blank used for sizing up my first set of DOM bushings on the lathe. Initial test fitting of bushings & holders (full length rod only used for set-up and testing) I can take a pic of the mount and the head connection tomorrow.

For pins like that i have used old hyd cyl rods. They usually have surface hardening under the chrome and should last longer than mild steel

56wrench said: For pins like that i have used old hyd cyl rods. They usually have surface hardening under the chrome and should last longer than mild steel Click to expand... IF I had the right size chromed rod, that would be ideal. I do not have any junk rods around. Here is a better pic of the assembly to see how the head rides and is able to contour the grade without binding the H frame pins. Pin and bushing getting ready to install Bushing installed in its slot Assembled unit with head lifted Next time I will have to build up the slots as they are getting a lot of abrasive wear.

You could use build up wire to make the pins harder. It's medium hardness so can machine with the right tooling. I knew a place that used to weld special stainless steel cylinders on a lathe. They used a wire feeder control and belt drive to turn the lathe real show. Ground was with a copper strip running on the back of the spindle. A simple rubber band held the trigger on the Mig gun. It would nice if you could make a nice slide or even a screw jack for the Mig gun to get a nice uniform spiral build up.

I just found my spool of build-up wire yesterday. Too late for this go around but I am trying to consolidate all of my welding gear into one cabinet for next need. I like the feed screw idea but, unless I start using this often, it is hard to justify the time it will take me to design-layout-build that attachment. I was already planning on a remote switch as I can wire that in in a matter of minutes - it would be much better than a rubber band!

A remote switch would be better. I was thinking a manual screw feed but just having a nice slide with the Mig gun held at the proper height and angle would make it easier to get a nice even build up. Some small bearings running on angle iron would be easy to make.

Now that you mention the bearings, I have a linear bearing and slide set kicking around somewhere. I think it has about 24" travel. It would provide smooth, linear motion so even hand set, it would be smooth acting.

That would work great. A small rack and pinion could work too. Angle the gun just slightly backward (pointing to the left) and weld left to right so the bead overlaps the previous bead leaving a smooth surface. I worked at a place that did chromium carbide overlay inside of pipe for oilsands slurry. 7/64" open arc wire. Didn't want to get flashed by that. For straight pipe the welding set up had 4 welding heads welding simultaneously. For elbows they had a really complex machine to weld circumferential. It was designed in-house and cost about 3/4 of a mil $$$ to build the 1st one. Employee's had to sign confidentiality agreements and if anyone visited the shop, they put tarps over the elbow welders. All the competition welded elbows lengthwise which caused a lot more distortion.

Your a pretty clever guy. I think the Primetech pt300 used the same floating pin setup as the ftx and rayco machine. Seemed to work well.

Here I go again with another rebuild. I needed to build up the floor support rails on the Deere 862B. They don't appear as available on Deere parts or other sources anymore and a quick resurfacing will bring them back to service. They had significant wear on the original top sides. After milling down the new upper sides (flipping the rails over - old bottom side is new top side) to make sure that there was a square surface for the slides to ride on, I needed to rebuild the worn sides that would become the lower edges. Might as well do it right while I have the time available. I took the MIG holder from the project in the beginning of this thread and built a quick mount for the vertical mill. The mill has an adjustable power feed on the horizontal. This is working perfect for a fast and clean rebuild. Just a minor repurpose of a fixture and some protective covers for the ways of the machine and I was in business. Using an ER70s-6 filler wire so that I can machine it back down to spec with a 3" carbide insert fly cutter. Copper buss bar acts as a heat sink and retains a sharp edge for the steel. First couple of passes looking perfect for my needs.

Excellent! Too bad you couldn't make it weave about 1/2". The shop I worked at the automatic machines weaved about an inch with the bead about 1 1/4" wide. Did you get any warping of the bars?

Welder Dave said: Excellent! Too bad you couldn't make it weave about 1/2". The shop I worked at the automatic machines weaved about an inch with the bead about 1 1/4" wide. Did you get any warping of the bars? Click to expand... Yes, a slight banana shape to it but nothing I can't jack into place like I did when I installed the first side. This second side did not need as much build up but it needed more work over a longer distance. I had more time to think about how to do this one. I also tried to keep the amperage down, let it cool between passes to under 150 degrees and narrow passes to minimize distortion. Rather than taking a chance on my carbide inserts and cutter, I will likely grind this down to shape. The banana shape will be more difficult to clamp down into the mill. As another solution, I pulled out my mower blade sharpening jig that uses a 4.5" grinder. I can clamp that down to the bar on the milled surface to keep it true. The jig will keep the grinder at 90 degrees from the side as I grind it down smooth. Once my sizing gage passes over the bar without restriction, I should be good to test the fit with the slider for any tight spots. A little bit of spatter on the previous runs but I'm happy with the results of the weld build up.

You could flip the bars over and heat with a rosebud to help straighten them. In hindsight heating the backside and prebending them before welding would help limit distortion.

I measure the bend after I finished it up this morning. A little over an inch over 107.5" length. Easy to jack into place with a small bottle jack so no problems. I think the other side would have measured more bend when I did the freehand work with wider puddles and more heat. This is the lawnmower blade sharpener jig stripped down and clamped against the freshly milled squared up surface. It held the grinder at the correct angle. Although I did not get enough build up to fill everything 100%, this surface is more than sufficient to keep the sliders tighter than they were. The slides will only carry the weight on the top side (milled surface that is upside down in pic) and the rough bottom side (shown as being ground smooth) should never see much wear unless the pan is dragging the ground heavily while sliding the floor. The wooden block is my sizing gauge for rough in. Slide shown in position as it will run. Shop built new slider shown on the bottom - old one was worn in half and past the bolt holes. Old slider on the top will run on the rough surface. Entire assembly is shown upside down from the way that it will be installed on the machine.

Not sure if it works with any MiG wire but have proven to myself over the years, something taught to me by an old oil field worker. If you immediately quench 7018 with water, enough to sizzle it but not lose the heat, you can get some decent hardening, as you keep welding.

It would depend on the specific piece you were quenching. It could cause it to crack and/or fail. If you want something harder that's what they make hardfacing rods/wire for. For something not too critical you could try quenching the hot weld.

Another rebuild. This time, debris blocking rings on an FAE cutter head. The rotator was tack welded into place on the welding table - no easy way to clamp it next to the vise. The two pieces were clamped around an old tire hub off of the pressure washer, centered up on the lathe and clamped firmly. This wheel was in the scrap pile looking for a reason to be put into service. It had 3/4" plastic bushings to roll on. 3/4" bolt for an axle and just the friction of the belt to drive the wheel assembly. Simple, basic and most importantly, on hand at the shop! The rotating ground was the only difficult part. I have a junk pressure-washer brass swivel that is waiting for this application but I could not find it. So, I tried a SAE to PIPE adapter with a bolt run through the center. Works just fine but likely not good for a high amperage job.

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.