PTO Shaft w/o Set Screw -- Safe/OK for Post Hole/Auger?

[Almonzo]

Recently purchased a used 3pt post hole attachment, at auction; it has a logo referencing Green Manufacturing, in Bowling Green.

PTO shaft says 53" compressed metric (6 spline on tractor end, smooth/round bore on implement end, with a roll pin shear pin and a set screw on implement yoke.

Since that PTO shaft appears not to expand (safety shield is single piece), and was approximately 6" too short to reach my JD 2640 spline shaft, I ordered a Vevor 51"-75" adjustable shaft (link below), which arrived, but does not have a hole/tap for set screw on implement side -- just a shear bolt hole. Amazon.com

Questions:
1. How important is having a set screw, when powering an auger/post hole digger? (Am envisioning shaft flailing around if shear pin breaks).
2. If it's important, why do other types of equipment often not have a set screw? I'm guessing it's related to greater possibility shear pin/bolt shears when in raised position, where shaft may be more likely to slide off the implement?
3. Assuming the set screw is important, am I better off ordering a different shaft and/or yoke, or drilling and tapping this one?
4. And is there a standard set screw size?
5. Re the shaft, am I correct in thinking a sliding 2-piece shaft is more useful or even necessary, for an auger, so it can extend or contract better while raising/lowering? If so, why would the auger have come with what appears to be a fixed 53" shaft?

Thanks for any help.

 

[sweettractors]

Recently purchased a used 3pt post hole attachment, at auction; it has a logo referencing Green Manufacturing, in Bowling Green.

PTO shaft says 53" compressed metric (6 spline on tractor end, smooth/round bore on implement end, with a roll pin shear pin and a set screw on implement yoke.

Since that PTO shaft appears not to expand (safety shield is single piece), and was approximately 6" too short to reach my JD 2640 spline shaft, I ordered a Vevor 51"-75" adjustable shaft (link below), which arrived, but does not have a hole/tap for set screw on implement side -- just a shear bolt hole. Amazon.com

Questions:
1. How important is having a set screw, when powering an auger/post hole digger? (Am envisioning shaft flailing around if shear pin breaks).
2. If it's important, why do other types of equipment often not have a set screw? I'm guessing it's related to greater possibility shear pin/bolt shears when in raised position, where shaft may be more likely to slide off the implement?
3. Assuming the set screw is important, am I better off ordering a different shaft and/or yoke, or drilling and tapping this one?
4. And is there a standard set screw size?
5. Re the shaft, am I correct in thinking a sliding 2-piece shaft is more useful or even necessary, for an auger, so it can extend or contract better while raising/lowering? If so, why would the auger have come with what appears to be a fixed 53" shaft?

Thanks for any help.

I have seen pto's that used no set screw if the implement used a snap ring on the implement input shaft that would keep the shaft from coming off when a pin was sheared. Ken Sweet

 

[2manyrocks]

My TSC PHD has a set screw. In my opinion, it is important to have a set screw or a snap ring in place given the number of shear bolts I've broken. When the shear bolt breaks, that set screw or snap ring is supposed to keep the PTO shaft from sliding off and then flopping around everywhere at 540 rpm.

 

[CliffordK]

Does somebody on foot operate the auger? In that case, I'd encourage prioritizing safety.