Rotary Cutter King Kutter shear bolts.

[SF Mike]

I just put a brand new 6' King Kutter on my Ford 4000.

The shear pin/bolt broke the instant I engaged the PTO.

I have owned and used other rotary mowers.

How can I avoid this? Not sure what my RPM was at the time, but it was at least a fast idle.

Thanks for any comments.

 

[bullbreaker]

Welcome to TBN . Make sure you checked the gear box oil in your cutter , some have been known to come shipped dry . You cutter takes a King Kutter Grade 2 Shear Bolts 51 according to oem specs. Keep your rpm as low as you can . I 'am assuming your not engageing in heavy grass/weeds/etc .

 

[ruffdog]

Being that it is new, make sure a block of wood or some other object is not underneath. Also, some manufacturers tape the instructions under the deck.

 

[SF Mike]

I didn't see anything underneath except for the instructions.
I did fill the gearbox.
I was sitting flat on mowed grass.
Bolt broke the second I engaged the PTO.
I have some for an older mower but they are smaller.
I'll try to get some tomorrow.
I'll idle it as low as I can.
Thanks for the responses.

 

[Eagleview]

Quite possibly the blades were sitting on the ground if the skids have not been adjusted yet . I dont know why people bother with shear bolts, a PTO shaft with a clutch is only $160 and you never have the problem again . From then on the clutch does the work and protects the PTO system and slasher gearbox .

 

[Avenger]

Ahh yes. King Kutter rotary mower shear bolts. Horrible memories. I call them horrible memories because I added a slip clutch after I mowed 8 acres and went though 17 shear bolts. Sometimes it would snap after simply turning on the PTO at an idle, but once I put grade 3 in there, that went from breaking every other time to every 5th or 6th time. That electric over hydraulic PTO is violent, even at an idle. I have since replaced the shear bolts with that slip clutch.

The slip clutch I got:
https://www.amazon.com/gp/product/B01L9UZO64/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

Any bolt will work, so long as it is grade 3 or lower. Once I put the slip clutch in place, I put grade 5 bolts in.

When I was mowing that field, there were large gopher mounds in the high grass that I kept hitting, thus breaking a bolt. I got good at replacing them, but the time I took me to mow that field vs this year with the slip clutch, night and day. Save yourself the trouble and get the clutch.

 

[David Wayne]

On a ford 4000 you should be able to ease the PTO on slow then bring it up to RPM's. And I agree with getting a slip clutch.

 

[Avenger]

A quick note on my slip clutch: I had to trim the PTO shaft about 4 inches after installing the slip clutch. You will probably need to do the same, but a hack saw and 5 minutes, it is easily done.

 

[ruffdog]

I had a 1/2" shear bolt on my Behlen cutter and KK cutter. I never sheared a bolt and always started up slowly at idle when I had the TC33D. The Toolcat PTO is a hydraulic motor that is electrically activated and still have not sheared a pin.

 

[CobyRupert]

...... That electric over hydraulic PTO is violent, even at an idle. I have since replaced the shear bolts with that slip clutch.

Why did manufacturers go to electric over hydraulic?

It seems to have started with riding mowers, then I noticed them on SCUTs/CUTs. Now even 75HP utility tractors have them.
It can't be cheaper than a cable and a lever.

I can (sort of) understand if it started as a way to meet safety requirements on riding mowers so grandpa doesn't back over the kids with the mower blades on. That is, safety interlock are easier with electric. But why are they on utility tractors when so problematic for sheer bolts snow blowers, rotary mowers, choppers etc..?

Is it they think Americans want easy and convenient pushbuttons?