I have an issue that seems to be a can of worms i never intended to open...... Most ppl in the industry talk about mouldboard position when discussing cutting, I would like to know your opinions on the actual cutting edge shape. I operate cat 16(g+m) graders as well as cat 24(g+m) graders on a mine site in Canada and most of the time the cutting edge looks just like a "U" from operators rolling the MB back and forth "working the edges" (is the back edge really meant to cut??... does everybody chase their edges around like this?) It would seem to me that the edge was meant to be sharp, and would cut from the front, and maintaining sharpness is part of the skill. What do you call sharp? can and do you work with a cutting edge that is +/- 90%...... seems to make more sense to me if the blade looks more like a triangle than a square. any help is welcome, if you need more details just ask
I would agree with you. As far as I'm concerned the profile of the bottom surface of the cutting edge (circled in the sketch below) should be a straight line from the front to the rear. I had to take an illustration and rotate it a bit to illustrate the point, so don't read too much into the angle of the cutting edge in the drawing. I wouldn't normally expect to see the moldboard on a mine haulroad maintenance grader to be rolled back as far as that sketch indicates. What's meant to cut IMHO is the front bottom corner of the edge. In a way it's almost self-sharpening as it wears. The profile as shown in that sketch (albeit with a different angle) is what I'd expect to see on any grader coming to the shop for a cutting edge change.
I agree with Nige. I have heard of operators (some, not all) in mine-haul road applications rolling the blade all the way forward and even putting the controls in float, due to lack of ambition and the desire to learn in my opinion. This is possible only when the edge is rounded over. I prefer to do most of the work with the blade about 90% back which will tend to sharpen the cutting edge somewhat to look like the illustration in Nige's post. The blade will carry more material in this position. I roll the blade forward to aid in cutting hard material (assuming the edge is sharp), and to make finish passes where one can see the cutting edge better. I am not a full time blade operator though, so folks with more experience may correct me.
The one thing I see on grading mine haul roads that can be as hard as concrete is the apparent reluctance of grader operators to first drop the ripper/scarifier into the road surface to loosen the top 3-6" so that the material can be "worked up" so as to produce a properly-graded surface. Really the moldboard/cutting edge "angle of attack" relative to the ground is dependent on how the material rolls up and off the moldboard. The easier the material rolls the less energy is needed to cut. Therefore it would be logical to assume that an AOA that works perfectly on one type of material would not necessarily work so well on another. That's whay all grader operating manuals give a prewferred angle to start off with (the top front corner of the moldboard about 2" ahead of the cutting edge IIRC) and then roll the moldboard slightly forward or backward from that position to get optimum cutting perfromance and material "roll". Agree with Oxbow that rolling the moldboard over forwards when doing road maintenance work (as opposed to road construction finishing operations) as far as it will go is simply because the operator lacks ambition.
Thank you so much for your help folks, your info was very helpful. over the years it seems our mine team has developed a misconception about how a grader works. from the comments, it appears that someone down the road was a lazy operator and everyone has forgotten how to keep a sharp blade due to poor training,(by same operator) and after 40 years we are now basically large metal squeegees. i have tried to bring this up several ways to our team, to no avail.... they are convinced that this fella knows what he is doing, and cannot figure out why we are destroying graders.(picture a grader, MB fully rolled forward, front wheels barely touching the dirt due to the downpressure needed to cut with a rounded edge) any suggestions on how to educate the ppl who run the mine about this? any time i bring it up, it turns into a bs session about MB position and I am outranked and out-numbered. thanks again everyone, you have really put my mind at ease.
Hahaha, large metal squeegees, I love it. The only way to get through to closed minded, ignorant people is to write what you want to say on a 20lb. hammer and then hit them in the head with it.
I do not have one available, but I believe that this is addressed in the Cat operators manual. Perhaps you could find that page, copy it, and post it somewhere conspicuosly without taking credit yourself for posting it. Then maybe one of the higher ups will read it and take credit for the "new way of operating", and implement the technique. My Dad used to tell me, "if you have a really great idea and want to see it come to fruition, whisper it to someone else and let them take credit for it". One of the past forum contributors, a gentleman by the name of Randy Krieg I think, had worked for Cat in the development of graders and I believe he co-authored the current operators manual. I have not seen him on here for awhile, but he has contributed extensively to a thread in this forum entitled "Operting Techniques" or something like that, in the motor grading section. I believe that you can still find it, and it is well worth reading if you have the time. I came across it one night about 9:00, and before I knew it it was 4:00 in the morning and I had read the entire thread, which is quite lengthy. Some very bright and creative people contributed to that thread over the years, and in my opinion it was a treasure to find. The problem you face is that if someone on another shift runs with the moldboard rolled forward all the time you do not get the opportunity to run with it sharp when it is your turn, unless the cutting edges have just been replaced. Good luck enlightening the powers that be!
I found the thread that I mentioned above, and here it is: HeavyEquipmentForums
I like the hammer idea, might keep it for later though. I have pointed out the manual to the training dept and only got blank looks and more MB rolling bs, these guys do not like change, too much work maybe? ah well looks like Oxbow's dad had the right track and I intend to find a way to try just that. could be they are resisting the idea due to years of being the go-to guy and can't allow someone to have better ideas as it would threaten their percieved "position". besides, who likes to admit they are wrong? I know l don't. thx for the link Oxbow, every little bit helps
You bet graderhead, enjoy the reading!
This is the paragraph from Cat's "Motor grader application guide" on moldboard tip. 7. Moldboard tip. This is a very important feature: its proper use will increase machine productivity, increase cutting edge life and could prevent machine damage. The top of moldboard can be tipped ahead of or behind the cutting edge. This helps position the cutting edge at its proper angle to obtain the desired material cutting and rolling action. Maintaining a rolling action on the material while working will reduce horsepower required and provide maximum productivity. Normally start with the moldboard top positioned approximately 2 inches (5 centimeters) ahead of the cutting edge. From this position, tip the moldboard forward or back to obtain and maintain the desired cutting-rolling action. Tipping the moldboard forward will increase moldboard throat clearance (distance between the top of the moldboard and the bottom of the circle). Generally, a wider throat opening allows better material flow along the moldboard in all soil types. Material buildup into the circle area may increase circle wear. It can also stop material rolling action and cause it to be bulldozed. Bulldozing material requires more horsepower, more traction, and reduces motor grader productivity. To cut hard material or for finishing work, tip the moldboard further forward than the start position. When finishing, tip the moldboard top 4 to 5 inches (10.2 to 12.7 centimeters) ahead of the cutting edge so the cutting edge is approximately 90 degrees to the cut surface. This moldboard tip position will generally position the drawbar parallel to the finished grade. When the drawbar is parallel to the finished grade, circling the moldboard will have little effect on the cross slope being cut. The amount of tip required will change slightly depending on the machine, tire size, cutting edge size (6 or 8 inch [15.2 or 20.3 centimeters]) and if cutting edges are new or worn. Tipping the moldboard forward or back will change cut depth or blade height off the ground across the entire moldboard length. The tip control, for example, can be used to raise both ends of the moldboard for feathering material at the end of a cutting pass or for increasing cut depth over the entire moldboard length by use of a single control. Cutting high bank slopes or deep ditches requires more forward tip on the moldboard to obtain the proper cutting-edge-to-material contact. Attempting to cut with the moldboard in the full rear position in these applications, or with worn cutting edges, could result in difficulty penetrating and cutting the material. N O T E Use caution when working with the moldboard at full back tilt. Damage can occur to the moldboard tip pivots, cutting edge attachment bolts and support area for the cutting edge. This may cause a reduction in cutting edge support. For maximum cutting edge life in road maintenance work, maintain a near constant tip angle. Frequent changes to tip position in this application result in accelerated cutting edge wear. In general, tip the moldboard rearward for heavy clays and cutting packed snow or thick ice, after first penetrating the material with the moldboard tipped forward. In snow removal work, tip the moldboard so the cutting edges are approximately 90 degrees to the work surface. This allows the moldboard to slide over the road surface with less damage TO THE ROAD and over many obstructions without damage to the machine.
Don't tell anybody, but you can sharpen your edge on a length of asphalt road. Just lay your edge down carefully, and sharpen it over a distance. Some sparks will flow as u go, but the edge will then be good to go. I see the problem doing this with the 24 though...
We have problems at the mine I work at with operators err um more drivers one sideing the blade and haveing 6 inches on left and 2 on the right. Also they all have different pitch ideas on the moldboard and rarely sharp. We also run the edges with the sandpaper looking stuff that I can't remember what they call.
graderhead. If you want a complete copy in pdf form of the Cat Motor Grader Application Guide referred above please PM me with your e-mail address and I will fire it off to you. Also - please post a photo of the grader being used as a "squeegee", asking for help to improve. I suggest starting a new thread for the photo for reasons that will become obvious. After a number of the more shall I say erudite contributors from on here (that's you CMark ......!!) have done, to quote the famous Chinaman, their best Raff out Roud impression and hauled themselves up off the floor (give it time, I'm sure it will be worth it, even for the humour value) show the thread to the naysayers at your place of work. You could come back later and tell us how it went .........
I have a copy of the guide, and l have had ppl quote it when argue-ing the issue. one thing l do notice is the size of the cutting edges we use. they are about 2.5 inches thick and about 20 inches tall as well as perfectly straight. when l look at pictures of other graders, the edges are never that tall. l believe that they are not compensating for the edge height when following the recommended operations, leading to the MB being way too far forward from the onset, also there is no edge coming out of the shop, both sides of the blades are shaped the same, bolt holes and all. we are not allowed to bring cameras onto the site, but l will see what i can do about a photo. BTW some guys here even brag about how fast they can burn through it (4 hours??? really?) just to sit in the coffee room while new blades are installed.
Intrigued about the cutting edge design. On our 16M we use 10" deep 1" thick straight (not curved) cutting edges. Reason is more wear material. I realise it may be difficult but any chance of a photo of the edges as a kickoff.....? On really abrasive material I've seen graders take a set of edges in 8 hours. Not terribly unusual then.
I just got finished on a job in Fort Mac Alberta. To get to where I was working we had to travel on the haul roads for the mine site. I noticed the Cat 24 "m" that was blading the road had his blade rolled all the way ahead. He had serrated blades on. The cutting edges were obviously dull and by applying more pressure to make the cut all he was doing was making a mess. The blade was nose diving on the weaker spots of the road and jumping back up on the hard ice. The road was very hard to drive on. Good information in this thread about proper blade angle.
In view of the post above I'd repeat the comment about loosening the top surface with the ripper before starting to grade. Roads travelled by heavy mining trucks can get compacted to resemble something like concrete.
In any other season yes I agree to rip them first, but these are winter haul roads (ice) and they just keep them scratched up for a smooth driving surface and traction. By using the correct blade angle you can always keep the blades sharp and do a good job scarifying ice roads.
we are not allowed to rip the haul road during winter here, the reason being that there are large rocks buried in the road and if you catch a ripper tooth on one of them it will damage the grader. this winter one of our rentals caught a big one and tore the whole ripper off of the assembly. blade photos on the way
I think your company wants to give somebody a paycheck to do it wrong. If you want somebody else to get that paycheck then by all means try to prove it to them that they're doing it all wrong. Seriously, you can't win on this.
I do have one small hope as the mine manager is actually trying to shake things up and realizes there is a certain "culture" here... but ya, you are probably right.
You've already given it a bit of a push, now I'd just sit back and watch for a while.
Especially in freezing conditions roads will "grow" rocks, the frost pushes them up to the surface. If they are really big a dozer is the only answer, smaller ones can be successfully hooked out with a grader ripper. Remember the 24 has a D6 ripper on it. You can't grade a road well if your moldboard is bouncing off semi-buried rocks all the time.
This blade tip angle thing is interesting. All the accepted literature says to tip the blade forward somewhat, whether on a grader or dozer or whatever, for better penetration in hard ground. This is obviously knowledge gained from empirical evidence over many years. But this is counter-intuitive. As in Nige's pic ^^^ you would think a more backwards tip to the blade would cut better. We can compare the cutting edge to a cutting tool on (for example) a lathe. A lathe tool can be negative rake, neutral or positive rake. We are told that a positive rake lathe tool (comparable to tipping the moldboard back) gives easier cutting and requires less horsepower. But then we are told that a more 'neutral rake' moldboard is better for penetration on an earthmover. One thing a lathe tool has which a cutting edge hasn't is a clearance angle. Even a new cutting edge will quickly wear its clearance angle down to zero. So why is a more 'neutral rake' recommended for an earthmover? The only reason I can think of is that the more perpendicular the cutting edge is to the ground, the smaller the surface area of the edge of the blade, and the smaller the surface area the less downward pressure needed from the machine in order to penetrate the ground. If someone could come up with a cutting edge which kept a permanent clearance angle, then lathe tool theory would apply and a tipped back blade would give better penetration. (Possibly ?? ) One thing is for sure. Moving the blade backwards and forwards to give multiple angles to the edge like in graderhead's photos seems counterproductive whichever way you look at it. Edit: Maybe the operators are trying to grind a clearance angle on the blade? Run for a time with the moldboard back and then tip forward to use the clearance angle created??
Yup this works good, but just be careful of the grass in the ditches. I've heard of a few guys starting ditch fires from the flying sparks.( I will NEVER admit to starting any ditch fires myself, but have seen it within minutes of me driving by. Must have been the other guy! lol)
As far as better penetration when the blade is pitched forward......I believe it has to do with the width of the steel pushing down into the ground. If you run with the top of the blade approximately 2" ahead of the bottom, you get nice rolling action of the material. Remember, an earth mover has to move the earth, not just cut it. If you run the blade there most of the time, it will grind a nice sharp edge. Then, rolling the blade a head (a little, not all the way), will give you a nice sharp edge to cut with. Once your tough spot is cut, roll it back to your normal operating position. Rolling the blade all the way forward doesn't serve much purpose with the blade under the machine. This range of motion is mostly provided for highbank and ditch cut positions of the moldboard. In those positions, extra blade tip is often needed to get a decent cut, or to adjust your depth of cut. The skill level of many haul road maintainers mentioned in this thread is pretty low by the sounds of it. They wouldn't know about high bank and what a machine can do in that position. To them, blade pitch must be designed for their squegee use. Rolling the blade all the way to the rear serves a few purposes. Rolling the blade back is best for carrying material, or sorting out rocks. This position lifts material off the ground, and if left 1-2" off the ground can let small material pass under the blade while moving larger rocks off to the side. This is often used on haul roads when spillage clean up is needed without cutting into the road surface.
Maybe this diagram might help. It's basically the same as the one I posted before and expanding on posts that various contributors have made to date. Consider the "sharpen, cut, & roll the material" to be a 3-step process that goes something like this. That's what the 3 parts of the diagram are intended to show if you read them left to right. The thick black line represent the road surface. Step 1 - Roll the moldboard back and use the road surface to "sharpen" the bottom of the cutting edge if it's not already sharp. Note how the edge is parallel to the road surface. Think of the road surface as a sharpening stone if you like. Step 2 - Once you have your cutting edge to the desired "sharpness", roll it over forwards so that only the front corner (toe) is touching and the heel is well up above the road. Think of it as a chisel if you like. This is going to give you the most downwards cutting pressure on the road surface that the deadweight of the grader will support. Any more than that and you'll simply lift the front wheels in the air. Step 3 - As soon as you have penetration and the material is "rolling" up the blade nicely then the moldboard is rolled back slightly to decrease the angle of attack of the toe (and so prevent the cutting edge trying to continually dig itself into the road) but at the same time not so far as to allow the heel to touch the surface and thus lower the downwards pressure on the moldboard. The happy medium is somewhere in between. However while you are grading if you can actually roll the moldboard well back you will in actual fact be sharpening it ready for the next cut. Note: Whether you use either straight or curved cutting edges a brand new set are going to have a certain amount of "inherent sharpness" because of the way the edges bolt to the moldboard and the angle at which they present themselves to the road. The trick is maintaining that sharpness right from new to worn out. P.S. For obvious reasons the thicker the cutting edges the more difficult they will be to sharpen.
lol..been there but no grass fires....I don't think.. Keerym and Nige...good information and the diagram is perfect.
Nige, you are the man!!!!. was going to try and explain the same thing but you did it much better than I could have ever hoped. Right On!!
Having done a fair bit on graders I usually keep the blade fairly well back as this keeps the material alive so to speak and is easier to push a bigger load as u r carrying it rather than sledging it along, also moves across the blade quicker. Doing final trim work for asphalt laying I have it rolled forward as this lets u see the edge better and forces the material down on to the ground so u r sorta riding on a wedge of gravel in front of the blade. Moving a windrow across a road, usually have it fairly well back as it rolls a lot better, any large objects are lifted up and rolled out to the side of the blade rather than forced into the ground and eventually under the edge.Never tried the sharpening on the asphalt thingy, don't think the local councils would look at it to kindly if u did that to their roads. We put new edges on to do a final trim and throw the old ones back on to do the rough stuff.
this is the best explaination I could hope for, do you mind if I print it to hand out to guys at work?
When I was at albian I changed the cutting edge on one 24 twice in a 12 hour shift. Others said they had done the same. It boggeled my mind as here at home a cutting edge on a 140 will last a month.
Our company had a road job one year, and our second grader man who mostly did private work was off with an injury. They hired an older man that had worked doing woods roads all his life. At the time we had a 1989 730 Champion. For the job, they rented a 972D. I stayed local as I had experience with our Puckett, and Alitec mini graders. After A month or so' I was sent over to the road contract to help prepare the subgrade. The forman, and the government engineer didn't see eye to eye, and the engineer was making us string line the subgrade. There was a long section that was between 5 and 8 inches high. I sugested that the 2 graders work together. I took the lead with the old Champion, and the 972 came behind. After the first pass I could tell that I was cutting, and the JD was only moving my windrow. I cut the strip he had just done again, and again he just moved my windrow. So I walked back to clairify that he knew that we had to cut a fair bit off the road. He said ok, and we continued on. I looked back, and he was spinning and not moving a thing. Does your 6 wheel drive work....yep got her on. Are you rolling your moldboard ahead and back.....What do you mean.... I was moving twice the hard packed material with a worn out underpowered old champion, with a 14 foot moldboard, and no 6 wheel drive, and winter tires than a brand new 972 6 wheel drive new tires. I tried the JD, and it worked like a top, and made the old Champion look sick. In my opinion, one of the greatest features of a modern grader is the ability to roll your moldboard. I start the cut with the blade ahead, and roll back until I find the sweet spot. If I feel her start to break traction, just roll the blade back a bit to take the pressure off. I would like to try one of those black cat cutting edges with the rotating teeth that the government graders use. They say they they are great on the hard pack.
Does anyone swap sides with the cutting edges to even out the wear across the bottom edges and extend their life? I suspect that in a production setting this may not be economical. I watch for wear in the center, then swap sides when there is about an inch difference with the outside ends. Will do this once or twice in the life of a cutting edge, especially if the emphasis is on snow plowing. I generally wear out a set of edges in a year or so.
Once the blades wear up in the center, we just use the cutting torch to square them up. I have heard the argument that this ruins the hardness of the steel, but I have been doing it for 20 years without problems. As far as snowplowing, we just let them wear to the shape of the road. I mostly do asphalt prep, and not a lot of road maintainance, and it surprises me how fast a cutting edge can wear out on a hard packed road. I have always wanted to try http://www.blackcatblades.com/xContent/products/img/scarifierbits.jpg
If you have to cut a haulroad that hard you will damage your edge the lower the edge gets the thicker it gets it gets hotter wears more , harder to push . if a roads that bad it needs more than just trying to grade a hard surface ,rip and remix and lay out material you can work with this is time comsuming and very expensive not to add incovience to work routines,Have extra material on your shoulders and a water cart do maintaince .helps to do more often makes the job easier better finnish ,less wear and tear and edges,Edges last longer without scolloping and the need to change end for end to get the wear from them ,edges on bigger machines cost **** loads stuff em and you have a probelm for a long time .making your job and everone elses job hell . Big gear destroys road surfaces , and destroys tyres so more grading actuallys costs less and becomes easier ...
I should but out, as I know nothing of the subject. When I put hard surface on the underside of the cutting edge on a loader bucket it rubs on hard road surface protecting the edge from wear. The upper face wears slightly from material passing over it & remains sharp. Might there be a very hard material for the lower face of grader cutting edge? Certainly most towns here in VT use the carbide replaceable studs on cutting edges.
I never realized the blade on a grader was such an exotic piece of iron . Nothing like a dozer , excavator , backhoe , loader .