CORRECTION/UPDATE: Regarding JD 413 brush hog driveline shear bolts...The 10mm bolts in from Lowes or most sources are almost always found in the "8.8" grade marking on the head. So are the Deere OEM bolts. They are $2.86 at Lowes if you can find the length/size you need. That was for a M10-1.50 100mm length. (between 3.5 and 4" long.) I just bought a couple OEM Deere shear bolts and they are just 3" long which means 75 or 80mm length is fine.
If you get other thread sizes (like 1.25 instead of 1.50) you have to be careful to get the same thread nuts. 1.25 is considered 'metric fine' while 1.50 is normal threads.
Deere OEM replacements are part number 19M7329 and are also marked 8.8 Note that 8.8 is the same tensile strength as Grade 5 SAE bolts. That is 120,000 psi. They are not Grade 2 as some people have said.
Being available at a well stocked Lowes (or ACE hardware, or the Deere dealer, etc.) takes you out of being in a special order or 'custom made' category. None are really custom made but I knew what you meant.
These shear bolts from Lowes or the Dealer or several places are $2.30 each, NOT $5 or $6 or $7 as I have seen people talk about. Being 10mm thick and grade 8.8 metric covers all strength factors -- the more expensive ones ARE NO BETTER.
I much prefer to have the right size that does not wiggle in the hole and lasts way longer before shearing. One factor is that rattling around in the hole wears the steel it is intended to fit and very slightly damages/distorts the hole. VERY minor, probably never know it in the life of the machine, but just one more of several reasons I use the closest/best fit I can get.
If I had a reasonable choice I would certainly never ever use a shear bolt in a rotary cutter/hog. With an older used JD413 that needs a seal on the main shaft and is never going to get one ... I'm not going to go make the changes to put on a slip clutch. And slip clutches are not very common on smaller cutters like the 413.
