excavater boom joints all loose line boring ?

[earthscratcher]

have a 135c, been on a hammer lots,all boom joints are 71mm and of course you know the price on that stuff from deere/Hitachi 80mm is way cheaper bushes and pin stock. was just going to line bore everything to 80 and rock on,would be a lot less welding with the boa-m1 if needed what are your thoughts? thanks

 

[skyking1]

Only works if the meat is there for it. Otherwise you opened a can of worms.

 

[Shimmy1]

have a 135c, been on a hammer lots,all boom joints are 71mm and of course you know the price on that stuff from deere/Hitachi 80mm is way cheaper bushes and pin stock. was just going to line bore everything to 80 and rock on,would be a lot less welding with the boa-m1 if needed what are your thoughts? thanks

Do you have your own line bore set-up? Time-wise, I think it would be foolish to mess around boring everything out when you can just replace existing? Is everything that pounded out that it needs welded up first? If so, sounds like new bushings were in order years ago.

 

[earthscratcher]

its been abused, I have a problem with buying heavily used stuff and fixing it. bushings are there but worn its hammered out on the fixed or boss side, I think there is plenty of meat at the boom base and stick to boom joints.would be taking out 4.5 mm per side.i guess, what would be enough meat? 1 inch around fixed/boss side ?

the two link belts I have 135/145 both run 75mm pins in these spots def a beefier setup, 80mm is the most widely used size all 200 size machines use it. was quoted 10ft 80mm 4140 tgp 1700.00 10ft 65mm 4140 tgp 2800.00 what's up with that.

options are line bore weld heavily bore it to 70mm can get bushes and pins for 1/3 cost

line bore weld bore to 71 at least on the fixed boss and pay balls for deere/Hitachi oem

line bore possibly no welding (Maybe) or not has much have all the pins and bushings already for my 200 size stuff here in house, if there is enough meat

or buy new equipment and keep it under warranty at all times and live happily ever after, without ever getting the satisfaction,of shoving a new pin in a tight hole, or using the wealth of knowledge here on the H.E.F forums

 

[terex herder]

4140 tgp isn't good enough for pins or bushings. The reason stuff is welded and align bored back to spec is so standard parts can be used. There are no off the shelf steels that will give anywhere the service of oem parts. Yes, with sufficient knowledge, machining, heat treating, and plating you could improve on oem performance, but at 4 times the cost.

 

[earthscratcher]

yes I have wondered why deere/Hitachi uses the bronze type bushing, yet others use steel.these zero radius 135/225 machines seem to where out quickly at the big boom joints though. my linkbelt 135 has more hours and has seen a hammer and has less movement but it also has bigger pins. been running this tgp rod on all my excavator buckets with thumbs on them for years,.have not had problem yet. just sold one to my neighbor who broke oem pin off breaking concrete,so that will be a good test.

 

[earthscratcher]

Terex,maybe I am off on the 4140 but I went to the web sight where I order it, and it said metric bucket pin stock they sell 40mm up to 100mm cut to what ever length you want. oem from deere was 1350.00 on a longer pin for thumb, just got one of these chamfer the edges and drill the hole on the mill 325.00.

I know what your thinking just go to work and dig for a few hours and pay for that,,I get bored doing that. LOL

 

[terex herder]

For cheap pins its hard to beat scrap cylinder rods from another piece of equipment.

 

[fastline]

For cheap pins its hard to beat scrap cylinder rods from another piece of equipment.

I'm curious to do some learning. How are OEM pins made? Chromed? 4140 can be cased to HRC 60+. Not as hard as chrome but close.

TGP can be purchased cased but once you go welding on it, you're hosed.

Usually something like 8620 is selected for a case harden situation though with reduced carbon.

 

[terex herder]

TGP is a surface condition/finish process, not a material specification, nor a hardness spec.

Most of the heavy equipment cylinder rods I've ran across are surface hardened 1/16-1/8 deep and chrome plated. Probably a 4140 type material.

I don't know what materials are used for equipment pins. 4140 case hardened would be on the low range of material cost, probably adequate. But the case hardened/induction hardened is important, the common pre heat treated materials are typically about Rc28 hardness, which is to soft for long life.

 

[Volvomad]

Sounds like a lot of work but having everything oem is boring.

 

[fastline]

TGP is a surface condition/finish process, not a material specification, nor a hardness spec.

Most of the heavy equipment cylinder rods I've ran across are surface hardened 1/16-1/8 deep and chrome plated. Probably a 4140 type material.

I don't know what materials are used for equipment pins. 4140 case hardened would be on the low range of material cost, probably adequate. But the case hardened/induction hardened is important, the common pre heat treated materials are typically about Rc28 hardness, which is to soft for long life.

Thanks, yeah, I was just trying to learn what OEMs actually use/do. I am very familiar from our eng/mfg side and I would think 4140 would be a great pin material but like I say, the processing can be very tricky because the carbon content lends it more to a thru-harden material, which is not ideal. Thus the reason 8620 is commonly used in gearing applications, which carburizing as the casing means.

4140 is commonly offered either as 4140AN(annealed) or 4140HT(HRC28-32), but that is a through harden. We make parts with an HRC55-58 for a non-certified application with flame heat and oil quench and very low tempering. It ends up with about an HRC30 in the center, which is great!

When I say cased, I refer to surface hardening in which they commonly use higher frequency induction to optimize the skin effect and heat the outside surface of 4140 and quench to achieve a fast case harden, but just not as hard as real chrome.

I very much like the idea of hydro rods though! Excellent!

 

[earthscratcher]

machinist/line boring guy that I first got this material from, rebuilds everything with it,, all pins thru out the machine. he said its harder but still some what machinable. he also said he likes harder bushings and softer pins, then when it gets some wear its pin change only.maybe its job security? but every body around here uses him.

 

[earthscratcher]

I just bought a bunch of OEM pins for the long reach you can see where they have been heat treated. I wonder if stuff can be to hard that it breaks ? any cylinder rod that is messed up is usually bent not broke. guess it would be like comparing hss cutters to carbide on the lathe or mill.

I would say this tpg stock is not that hard and will probably wear quicker, but how tough is it?.

talked with a guy who is the ultimate tester of equipment he has a case 9040b with this stuff on his main boom stick pin. its frankensteined out with a 3 plus yd bucket. said it closing in on 4000hrs with this pin.
he runs stuff like he fighting snakes and in a skid steer rodeo at the same time. so maybe this tpg stock might be tough?

 

[fastline]

You have to study mechanical properties and toughness curve in different HT states to arrive at the properties you desire. All those pins run in double shear, which can be simple to calculate, but then you have to assess the forces on the pin to arrive at an estimated fatigue life. In something like this, infinite should be the goal on those pins.

Case or surface hardening is solely a means to reduce wear, but it is common to push for a deeper case thickness to actually improve mechanical properties, but it is rarely advisable to through harden to a high HRC. Indeed you bring embrittlement with high HRC.

This is why I'd like to know what the OEMs do/use, to better understand their strategy. Personally, I would never want a pin case hardness higher than my bushings. I probably would not want chrome pins as that hardness is certain to be higher than the bush material. However, this would assume you could simply swap pins to "fix" a problem and I don't think that strategy is common. Even with dissimilar hardness, both components will wear. Another reason to never match hardness is galling. I would expect the bushings to be of a different alloy to further ensure that doesn't happen.

It would be interesting to cold cut a hydro rod away from any welds and analyze the hardness from the outside, inward. If I had to guess, I would say HRC 50-55 on the outside under the chrome, and HRC 35-40 in the center. The very standard 4140HT at HRC28-32 is actually still pretty soft for a friction wear item, but that temper gives good general mechanical properties. Any good OEM or MFG would buy annealed and do their own HT spec.

 

[earthscratcher]

here is a different pin its hardened on the boss area fixed movement spots, and polished where it rides on the bearings. its a ctp aftermarket,first one I have seen like this

 

[earthscratcher]

these bronze type bushings deere Hitachi uses don't like to be welded on, probably not the best thing to breath. how do you guys remove old bushings?

 

[Entropy1]

High quality pins are typically made from medium carbon steels, or chrome-moly steels. The core of the pin is typically 80-100-ksi yield strength. The outer 0.100" is induction-hardened to between 45 and 50 HRC. For extra wear resistance, and protection from the elements, they are sometimes plated in chrome (72 HRC). The pin has toughness for impact-resistance, while the case-hardening provides applicable wear resistance. If the pin were through-hardened (like bushings are) the pin would fail from impact-loading (brittle fracture) in short order.

High quality bushings are typically made from air-hardening tool steels (similar alloy to what iron worker dies are made from). The bushings are machined from annealed round-bar, then heat-treated (through-hardened with light-temper) to between 50-55 HRC. Note that bushings can still fail from brittle-fracture, but it takes appreciable abuse. The hassle with these types of bushings is that the bore interference-fit must be nuts-on (normally requiring line-boring operations). Large bushings are often installed with shrink fit (liquid nitrogen bath). Smaller bushings can be pressed.

If you do the math for a typical excavator/dozer pin joint, the compressive stress easily exceed 80,000 psi, which is beyond yield for most steels. Non-case hardened 4140 pins (30 HRC typical) will not last nearly as long as case hardened pins (extreme-pressure grease is your friend).

A good source for induction-hardened chrome-plated round bar for DIY pins (both US and metric sizes) is CRConline.com. The normal application for this rod is hydraulic cylinders, but this stuff works great for pin joints also - provided you don't have to drill any grease holes through the induction-hardening. If you need to drill a grease hole, you need to grind the hole through the induction-hardening, to expose the softer core of the steel - which can then be drilled/machined. This type of rod is generally considered non-weldable (too high of carbon content - welding will compromise the heat-treatment at best, or initiate cracks at worst).

 

[Entropy1]

Bushings | Parts and Accessories for Hydraulic Cylinders | Hydraulic Cylinders | Hydraulics | www.surpluscenter.com

Bushings,Parts and Accessories for Hydraulic Cylinders,Hydraulic Cylinders,Hydraulics, 2-3/8&quot To 2&quot x 1&quot Vogelsang Steel

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Another useful tip. An inexpensive bushing alternative for getting an old machine back online is to use split bushings (linked above). These are made from heat-treated spring steel. Although not as hard as the press-fit tool-steel bushings, these will hold up for quite some time against case-hardended pins, and also for a decent amount of time against non-case-hardened 4140 pins (extreme-pressure grease is your friend for all pin joints). The best part about these split bushings is that if your hole is slightly out-of-round, or a few thousandths too big, the bushings will work - very significantly longer than running with no bushing (aka never run a pin-joint within a mild steel bore - you need a hardened bushing of some sort).

 

[skyking1]

these bronze type bushings deere Hitachi uses don't like to be welded on, probably not the best thing to breath. how do you guys remove old bushings?

I lick a groove in it with the torch. It takes all the fight out of it.
The hot bushing cools and shrinks into the relief I made, and taps out easily.
The grease between bushings is the biggest pain.

There is a spacer in the boom butt that traps all that grease in there, so I had a nasty smoky mess but I was prepared for that.