Combines 500 Head

I am not argumentative here but, I have cut a metal 't' post in two, have cut a cable off a guide wire on power pole and still have never broke a knife head; I tore the heck out of gaurds and sections many times.. We sell very few head assys. I say this to deduct you have an alaignment problem or some other problem. The knife head and bearing should be strong enough to pull the sickle apart at a bolt hole. The belt will slip on most any head I have seen if one runs into a bunch of green grass or down wet wheat. The plume of blue smoke from the lH side will be the evidence of slippage. IF you have a SCH cutterbar the fix for the early head problem has been discussed below in other posts. Check it out.

like tbran we have taken on old chain links from the horse days, plough shares, bits of machinery from who knows where and lengths of old 1_4" thick fencing bull wire. We generally run no-choke Crary or the Aussie "Adapta-gap" guards. It is rare indeed to break a knife head. I think we have done it twice in 9 years of flex front work. None at all since the high tensile bolt mod on the knife head bearing housing in "Hyper mods". The guards and the knife sections often take a severe beating but that is all. We have never damaged a wobble box through a knife problem. This may not help but check that the first 2 or 3 wear plates next to the knife head are pushed right back against the bar to allow the fore and aft movement of the knife as the knife head goes through the arc of it's stroke. Cheers!

I had a 800 25 foot head and I broke the head off about 3 or 4 times and then after looking closer the plate that goes under the wobble box to the header frame was broke. Just a thought.

I agree with you guys, it is more than likely an alignment problem. I would also go one step further regarding wear plates. I remove the first 2 or 3 so the sickle is not restricted in any way in its fore_aft movements. Watch the sickle from the wobble box end when someone pulls gently on the belt. You will see front to back flexing to demonstrate the importance of doing something about the first few wear plates. Maybe you can get by with pushing them back as far as possible but that wasnt enough on my 300 and 500 series heads.

Memories going! Should have included this above. Adjust the height of the knife head so that the knife rests only very lightly on or just clear of the first guard's cutting ledger. Check this through the full stroke as it is rare for the box to be absolutely level with the knife bar. To heavy a pressure on the first guard causes the knife to bow hard up against the top of the guards a couple of feet along the knife. The knife head has no capacity to flex vertically and an incorrectly adjusted knife head height can cause knife head breakages.

Just got in from doing beans all day and had to comment when I saw your post. I'm running a 520 head with an SCH knife installed upside down...In the field I was in today I managed to jam the knife 3 times, first was an old horsehoe, second was 5_16" round steel fencepost and the third was some old rusted piece of a bracket off..except for minor knicks to the section where each thing got caught all that happened was the drive belt started to slip. This was just what I picked up today..other times this year I've picked up a rake tooth, an old bolt and had a rock get jammed in it a couple of times. My head is a 1994 model and have never broken a knife head...sounds like your problem may be caused by something out of alignment.