Hi All Working on doing some repairs on a friends dozer. Its a 700K. We are working on the moldboard. The moldboard is OEM and is starting to show signs of wear. Does anyone have any idea what grade of material would have been used on the moldboard on this dozer from the factory? Is it just a mild steel like A36? Or do the factories use a high wear resistant steel like AR400 that I've seen mentioned on the forum before. Looking to stay with whatever factory used as it has held up good so far. Thanks.
Any input on this before the weekend? Thanks for any help people could pass along.
It's probably something a little better than plain mild. May not be full Hardox 400. See if your steel house has A514 or A572 in stock. A572 will be much easier to form in place if skinning the existing blade. Trick for anything is to get it on tight so it can't flex and crack. AR plate will need to be bump formed on the press brake. Have them roll it up tighter than you template. Stick the bottom on first, and work up using chins or whatever to pull the sheet against the blade.
Structure is not likely to be full-blown Hardox, that's generally kept for wear facing. As GT says above something of a good-quality 28,000-pound tensile structural steel like A572 will likely be the material of choice. I just had a look at some drawings for a similar size blade for a different manufacturer and the material is to all intents & purposes A572.
Great. Thanks for the feedback guys. I can definitely get a similar grade of steel to that. Thanks again.
Where you are talking about the "mold board" do you mean the face of the blade or the area at the bottom that supports the cutting edges? All the dozer blades I've had to rebuild were mild steel from the factory usually in the form of castings welded into place. I've re-skinned blade faces with something tougher, before access to hardened plate we used T-1 but now there are plenty of wear resistant materials. Ask your steel supplier for advise and pricing. On the small dozers with six way blades we use 3/16" plate and dogged the plate down to the base skin for a tight fit. On the larger machines we would made a template of the curve of the face and send the steel out for bending. You still have to dog the plates in but it isn't so much work. We usually were working with 3/8" to 1/2" plate for the bigger machines with straight or U blades.
Dozer Blades do not have moeboards. Dozer Blades have Edge supports
Tell that to some fifty year or older owner that grew up with the edge support being called a mold board.
**Pedantic Mode On** I'm looking at a factory drawing of a certain large-model dozer SU blade. The 3 main curved plates that make up the front skin of the blade are referred to as "moldboard LH, moldboard Center, and moldboard RH". **Pedantic Mode Off**
Nige, I literally had to look up several definitions of "pedantic" to come to a conclusion on your post. Well done.
Back with I started working for the International dealer the moldboard held the cutting edges on a dozer blade. As long as we know by context what someone is saying I don't care what it is called. If I don't understand I'll ask. See above.
What's a moeboard?
I put a new blade skin on my D6c....removed all the old and replaced with ⅜ AR400. The original seemed to be better than mild steel. Had the AR400 rolled at a local tanker trailer manufacturer. (They could roll ⅝x12' wide) Made the curve a little wide, ran chains around the blade, put jacks between the chain and the skin and flexed it into position for welding. Worked well.
Most likely so. A572 and its equivalents are a step up from mild steel. While your method of making the curve a little wide and pushing down the centre appears to have worked in your case with the tooling you had available to you and the thickness of the skin plate you were installing, I would caution against it. The reason being that if a chain breaks or a jack slips, solid lumps start being propelled at high speed in all directions. I saw a safety briefing not long ago where a curved liner plate that was being forced down in the centre came loose suddenly. Something that flew when it broke free killed the boilermaker who was working on it - sobering. The more usual method is to slightly over-bend the curve, fix the plate at the lower edge above where the cutting edges bolt on, then work upwards dogging the plate into position. The older the blade and the more dings it has, the more difficult the dogging process becomes.
Does anyone have picture of what is meant by dogging the plate? It would go a long way toward making the job quicker and safer for those private owners and hobbyists who haven't worked in a weld shop.
Not the best but all I could dig up at short notice. As tctractors would say, let's see if we can put some verbs to go along with the pictures/drawings........ First you need some dogs and some wedges. Here's a dimensioned drawing - I hope it's obvious which one is the dog and which one is the wedge. OK, so in the photo below you can see how the corner of the plate in the circle is not lined up with the plate next to it. It's probably sitting maybe 1" too high. To dog it down, weld a dog on the plate that does not have to move with the open end of the dog hanging over the plate that has to move. The drive the wedge into the gap to force the plate downwards to where you want it to be. Then the seam can be welded as you see fit. Only weld the dog on the side where you will insert the wedge, (where the weld symbol is on the illustration below) that makes it easier to remove afterwards. You simply hit it with a hammer (upwards in this case), and the weld will break off. In some cases of thick/stubborn plates it might be necessary to use multiple dogs & wedges to get the plate into the position you want it. It's 100% clear to me because I know what I'm looking at. Any questions shout out ..........
The moldboard is the curved part akin to a plow share. The frog is the piece that the cutting edges attach to. At least om a grader anyway.
Nige, I agree with you in instances where you're putting a lot of force on a plate to pull it in. In my case the curve was pretty close to fitting and the plate was pretty easily flexed with a 2 ton jack. I think the fit was within less than and inch so there wasn't any concern with flying parts. I know of a couple of instances where things got loose in a hydraulic press....very scary. There can be a lot more stored energy than you realize until something goes BANG!
The moeboard ls the 2x4 Curly would hit Moe with in the 3 stooges
This method of dogging is also used when fitting heavy pressure vessels together. I remember helping fit a 2 3/4" thick 10' dia. head onto a pressure vessel. The head alone was over 10 tons. I helped fit it the 2nd time because it fell off the 1st time. Nobody was hurt when it fell but a welding machine on a cart was crushed and it took a chunk out the floor. We heard the tacks start to ping but they were more than just tacks. You take a piece of 1/2" round bar about 2" long and weld it on both sides of the bevel. The "tack"s were about 4 to 6 inches apart all around the head. There was tons and tons of force on the head from using the dogs to align the head. Better to have to take a torch to the dogs (welded all around) than risk having them fly off or your wedge go flying when the dog breaks off. I think depending on the thickness and type of steel used on the blade preheat when fitting may be necessary as well. The reason I mention this is because when there is more force needed to pound the wedges than a couple blows with a 5 hammer you need to fully weld the dogs on both sides and around the ends to they don't come flying off. The nice thing is dogs usually start to move if they don't have enough weld to hold them. Also make sure to use 7018 or better and put good tacks on when using dogs. I also got the job of welding the MIG root pass and 7018 hot pass before the head was sub-arc welded. Had to have a tiger torch for preheat but had enough grinding of the tacks on that one seam to last a lifetime! Weld 4 inches, grind for 2 minutes, weld 4 inches grind for 2 minutes. You had to feather the root pass after every stop as well. That said having to repair a weld where the sub-arc burnt through because the root was too light isn't fun at all.
I prefer a 12" to 2" wedge, less chance of it being spit back out at me.
I thought the wedges in the sketch I posted were 8" long, but I agree with your principle. The longer and more shallow the taper on the wedge, the less chance of it being spat back out at you.
I certainly wasn't trying to say you were doing it wrong. Sometimes it's kinda hard to get into your head that not everyone uses 3/4" or 1" wear plates like the larger stuff does, and as a consequence it doesn't take much to get the metal where you need it to be. Even a fat bloke jumping up and down on it is often enough to get the plate into place.......
8"-12" long wedge often can't be used, like dozer end corners. Wedge-bolt; tighten down with impact to align plate(s) AWS sketch dog & wedge with brief written usage description MSHA inspectors will question you about any modified or DIY tools.
Got 6 screw dogs just like that in my truck. I used 1"NF tall nuts for axle u-bolts. They will crank stuff down, but I won't use an impact on them... stuff happens too fast when a weld pops. And I know what you mean about the inspectors. I built a little bracket to hang heads on V71 series Detroits once and the shop had to have it sent out and magged and the whole 9 yards of NDT to certify it.
Doesn't **** like that make you wonder what kind of people sit around and dream this stuff up? You can't even make stuff like this up. And further, how deep are they digging into your life that they'd even find your "specialty" tooling???
If OSHA saw the half ton of stuff I built to work on Wabco scrapers I bet somebody's head would explode.