Bent teeth in tooth bar

[Brad_Blazer]

The cold rolling process does produce some work hardening. It also leaves some residual stress so if you machine the surface of a cold rolled bar it will probably curl. Unfortunately, the actual difference in strength is hard to predict since the products we are comparing are not otherwise identical steels. The square bar I bought is listed as complying with ASTM A36 which means it has a minimum yield stressf 36,000 psi. The spec is pretty wide though. The average yield stress is about 50.,000 PSI and the maximum is 70,000 psi. Yield stress is the stress at which the metal deforms permanently. For a 1" bar my quick calculation shows 36000 psi equal to 500 ft-lb of bending moment. It seemed stronger than that when I was bending it but I do not have a pressure/force gauge on my press.

FWIW, According to my steel supplier the A36 HRS and 1018 CRS had about the same etrength.

I hope this makes sense

Brad

 

[Greenhouseray]

I made a variation on JohnF's toothbar.
http://www.tractorbynet.com/forums/showthread.php?t=76427&highlight=tooth
Instead of cutting and welding the 1" square bar teeth, I bent them. For the cross bars, my neighbor let me have a couple of worn out cutting edges from some type of scraper. The better one was 5-6" wide. the smaller one was about 3" wide on the most worn end. They both had 1 unused beveled edge. I welded the attachment bars and teeth to the larger bar. Then I welded the smaller bar under the teeth to capture the bucket edge and protect it.

Hi Brad
Did you heat the 1" square bar prior to bending it? I do not have a press. Do you think I could heat the bar and bend it in a vise with well placed heavy hammer blows and a piece of tubing to lever the mat'l? It would be helpful if you could provide all of your students with a line drawing of your bend profile. I like your addition of the bottom cutting edge, it locks the teeth rigidly and takes the load off the bucket cutting edge. Thanks
Greenhouseray

 

[JimR]

I too built a copy of Juohn's toothbar. It has worked out well for me. I like your idea with the cutting edge under it. To answer the last post. Yes you can heat these teeth up and bend them with a torch. I have used and abused mine to the point of snapping a few teeth off and bending a few real bad. I used my cutting torch to heat the stock up and bent them back into shape using my 4 foot extensions.

 

[Brad_Blazer]

Hi Ray.
It looks like JimR has more experience than me with hot bending. All I will add is you will need a stout bench and heavy vise. You might have a strong spot on an implement or a receiver hitch you can stick the hot tooth through to bend it between that and your cheater pipe. The trick there is handling the hot metal and getting an accurate bend.
In terms of a pattern I think it really depends on what you use for a cutting edge/bar. I took a smaller, easy to bend piece of steel and bent it to fit the cutting edges I had clamped to the bucket. Then I bent the first tooth and tweaked it to fit. After that it easy to copy the "master tooth" the way I was using the press. When I welded it all up, I welded the two end teeth first, then clamped a piece of angle iron spanning across the tips. The angle iron then made a great guide for getting them all in a straight line.

My press is the $49.99 12 ton model from Homier. It worked pretty good until half way through when a check valve failed on the jack. I slipped in a 20 ton jack to finish the project and was suprised I still had to pump pretty hard. I was careful not to reduce the 3-point bending span to avoid overloading the press frame with the bigger jack.

Coming up Next - Repair!

Brad

 

[Brad_Blazer]

Well JimR, It looks like you don't have a monopoly on tearing up teeth.
I tore up my tooth bar and learned a couple of things in the process.
1. The lower cutting edge helps the teeth support each other.
2. Really hard cutting edge material may not be the best choice.
3. If you weld to hard material, make a big hot weld to temper the Heat Affected Zone.

I bent the far left tooth pushing on a stump I was digging up. In working with the bucket, the teeth did seem plenty strong to withstand the hydraulic curl and lift forces, even with only one tooth. Pushing with an end tooth turned out to be another story. The tooth bent down, with the lower edge helping to resist the bend until the weld broke at the second tooth. The crack propagated from the weld into the edge allowing it to crack nearly in half.

If you look at the fillet weld on the second tooth in the first picture, you can see how it popped right off the surface. I should have known better when I welded that small bead because I had that happen with some tack welds while a big wide test weld I had made fared quite well when I beat it with a sledge to failure.

 

[Brad_Blazer]

I bent the tooth back by slipping a tube over the tooth and pushing down with the bucket. First I tried a piece of 1-1/4" sch 40 pipe but that bent before the tooth (gives an idea of the strength of the 1" stock). I then put together a piece of 2-1/2" square tube and 3/4x2" flat bar and that was able to withstand the bending force. When it bent back into position all of the breaks closed up.

Then I ground out the crack and broken welds plus all of the wimpy welds I had made in the lower cutting edge and re-welded. I cleaned it up, gave it a snazzy 3-color paint job (what happens when I don't have enough of any 1 color) and reinstalled it. I did some more digging tonight - so far so good!

Brad

 

[JimR]

Brad, I found that those longer teeth work great for popping brush, stones and almost everything else I shove at them. The only downfall I have had is that I push them too much for the size that they are. This leads to too much stress and lots of bending. So far I have broken off 3 teeth and bent 2 pretty badly. I have 4 foot extensions for mine which make it very easy to bend the teeth back once I heat them up. I can't bend them without the torch. I even tried jumping on the end of my extension. I guess that is why all the toothbars you see have short stubby teeth. I literally destoyed my short tooth toothbar beyond repair. It lacked the part that goes under the bucket. It was a very short lived toothbar, now a piece of scrap. I think if I ever need to build another, I will try yours witht he underside cutting edge. I found that I can't backdrag with my bucket without leaving 6 square indents in the ground from my toothbar. I guess that's why they make grader blades. Nice job on your toothbar. I wonder if Ray could weld all his 1" stock onto the top plate first. He could heat and bend them down first. Then heat it again to bend it back upwards. Getting the right angles will be the fun part.

 

[Brad_Blazer]

Jim, it sounds like you work your bucket pretty hard.
I guess the trick is to get a feel for how hard it can be pushed without damage and then make an informed decision with respect to repair time vs. git 'r done. Of course that's easier said than done when frustrated with a big rock in the iceburg position or a 40' weed lol.
I can always cut the teeth off short and shape them to mount replaceable teeth if the long ones prove too fragile but I don't think that will be the case.

The underside edge does seem to add strength by helping the tooth bar to act more as a unit as opposed to a series of individual teeth. Thanks for the positive feedback.

Bending the teeth after welding sounds like a good idea as long as you avoid overheating the original bucket edge.

Brad

 

[JimR]

Brad, I do work my bucket pretty hard. It only takes about 10-15 minutes to re-attach a tooth or bend one back into position now. After I broke the first one it is now like changing the oil, no biggy. I was thinking about them today again. I have broken four so far. Two of them twice. I don't think they will ever break again. I ground the two parts to be welded to a point and welded up the whole area with multiple passes. The original welds were only about 1/4"-5/16" deep. It is pretty hard to figure out what the teeth are doing when you can't see them. I like the long length as they get right down under the roots of bushes and trees. I can snap a 2-3" cherry tree root with these teeth with a few tries. Two of the broken teeth were done when I had my 4 foot extensions on them. The last two broke while trying to pop a small rock (I thought) that was about 4 feet across and 3 feet thick out of the ground. I don't mind fixing them as they are worth their weight in gold to me compared to short teeth.

 

[Brad_Blazer]

Jim, Sounds like an informed decision to me. The fully beveled welds should do the trick. Worry about my welds was a big part of why I went the bending route. The teeth are really impressively tough. When I bent mine I was trying to dig/ roll the remaining roots loose on about a 12" cherry tree I had pulled over using the drawbar and a pair of 20' chains (end to end) attached 6' up the trunk. Wild cherry trees are a bad weed around here. Wilted leaves contain cyanide and the trunks are typically covered with poison ivey vines. It seems like my whole property line is lined with them but the pulldown method is working well for me - as quick as the old backhoe I was borrowing earlier this spring.

I still need to make some tooth extensions to move some brush piles.

Brad.