How tight should new master pins be?

Hi, Mschwartz.
A LOTTTTT tighter than that. I think I'd be running a few beads of HOT weld around the outsides pin bosses with a cooling period between each bead to try to shrink the bosses onto the pins.

Just my 0.02.

I'm not saying this is a good way to do it, but I built up the ends of the master pin with weld and turned them down a little oversize. Did this for 955H several years ago, still tight.

What causes the pin bosses to be loose? Or did I get the wrong replacement master pins from caterpillar? The fit seemed about the same into both a cat link and a Berco link.

Sounds like more stuff from the "land of almost right".

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[quote="phildirt"]Some of the information above is bull shit.

A couple of weld beads on the outside of the pin and you will be fine. Will last as long as the chains and can be ground off if it is necessary to separate the chain.[/quote]

ya...we're talking about interference fit aren't we..........? and what it takes to keep things in place... is there any side load on a pin?😄

Yes, interference fit. No specific side loading other than the rails clanking around the rollers, idler, sprocket during turning and maneuvers over uneven ground

If you can drive master pins in with a 2lb hammer, they will fall out again within a couple of weeks of work. Normal interference fit means the pins should be at least 0.005" oversize, compared to the link bore.

The normal interference fit of master pins means you should need to freeze the pins in newspaper overnight, then take 10 mins of slugging with a 14lb sledgehammer and drift, to get them fully home, before they warm up.

Track pins rotate back and forth in the links continuously, so they come out rapidly if even remotely loose. It's the same technique you use to remove anything stuck in a hole, you turn it back and forth, to loosen it up.

Welding a loose pin in, by welding a circular weld on the end of the pin is useless, the weld will fracture within a few weeks due to the constant twisting movement of the pin and link.

A quick pin-tightening technique that does work, is welding about 4 beads of weld along the pin lengthwise, evenly placed at 4 points of the circumference, over the area of pin in contact with the link.

Once you've applied the 4 beads of weld, take a 4" angle grinder and carefully grind the weld beads to a tapered wedge shape, with the sides of the bead smoothed evenly to about 20° - 30° angle, and the wedge tapering from nothing on the inside end, to the full height of the bead, at the outside end of the pin.

Freeze the pin overnight, and then drive it in full depth with a 14lb sledgehammer and drift. The welded wedges provide a good tightening effect, and they provide good resistance to the constant screwing action of the track.

Naturally, this damages the pin bore, only use this technique as a last resort on old links, where you don't need to remove the pin again, and don't want to re-use the links.

No guarantees from me this is the total answer, your mileage may vary according to your workmanship, and the style of use the tractor undergoes (heavy dozing and rock conditions will soon find the loose pins).

Hard-won advice from an ex-contractor who bought his first Cat in 1966, and who had to deal with totally worn-out, beat-up Allis-Chalmers tractors, before that! LOL