Shear bolts

[DanL99]

What are shear bolts? I hear a lot of people talking about breaking them? Where are they and what do they do? Apparently when I was muck spreading I nearly broke one, can exactly remember what I done but I think I left it at 540 then turned of the PTO, enlighten me on what they are and how not to break them, thanks.

 

[bovine]

They are built into rotating machinery as a point of weakness. Commonly found where the PTO shaft joins the machine. Designed that if something stops the turning force the shear bolt goes and and leaves the tractor PTO in effect freewheeling. I've snapped one in a feederwagon with a bale of wet silage.

They look like a normal bolt, but cost a lot more!

They generally break when something PTO driven is trying to turn and you do something to stop it.

 

[JD-Kid]

realy just a safety part to stop sudden over loads
old fellas years ago on rocky or stump ground used to use wooden pegs on ploughs etc so if they hit a stump the plow would stop and not shock load the horses
older set up realy most modern pto's etc will have cam clutchs or slip clutchs BUT say baler knotters etc were it has to stop dead shear bolts will be used to total remove the input drive

 

[Kevtherev]

See the bolt?
Designed to break to protect the tractor and machine driveline.

 

[Grassman]

They are built into rotating machinery as a point of weakness. Commonly found where the PTO shaft joins the machine. Designed that if something stops the turning force the shear bolt goes and and leaves the tractor PTO in effect freewheeling. I've snapped one in a feederwagon with a bale of wet silage.

They look like a normal bolt, but cost a lot more!

They generally break when something PTO driven is trying to turn and you do something to stop it.

His veterinary skills isn't exclusively just animals!

 

[Lincs Lass]

Not just pto /rotating equipment ,also through plough and subsoiler legs

 

[jamesy]

Just watch out if you have a shear "pin" they can cause problems I believe!

 

[Lincs Lass]

Remember them on a lely power harrow ,,shear pin cascate with ten pins to shear 4 times each one ,,they were very handy

 

[Paddington]

They're what you buy from the dealer in lots of say half a dozen at a time as you will always need one when the dealer is closed. The dealer puts them in a plastic bag and you store it on the tractor, then when you need to replace one you find you have lost the bag. There must be dozens lying out there somewhere.

 

[Dry Rot]

And when you need one, your dealer doesn't have any, so you have to import from thousands and thousands of miles away! If buying a machine that needs shear bolts, make sure there are supplies locally! (Still waiting for mine to arrive from the USA).

 

[Tomtrac]

When you get fed up replacing them
get the welder out and weld it up then you can get on faster until it goes bang and blows a shaft /gear box
Its surprising if you check at sales etc how many are welded up generally can get away with a grind round to free off

 

[neilo]

Are they not generally just HT bolts, and much cheaper anywhere other than a main dealer with a 'shearbolt' label?

You should use the same spec bolt as the original, unless of course it's a pan mixer......

 

[JD-Kid]

And when you need one, your dealer doesn't have any, so you have to import from thousands and thousands of miles away! If buying a machine that needs shear bolts, make sure there are supplies locally! (Still waiting for mine to arrive from the USA).

have a ozzie made subsoiler here useds 19 mm steel rod for shear pins cheep as chips and about 4-5 ton break out even the point is held on with 4 mm mild steel fenceing wire ...
like neil is saying shear bolts mostly HT bolts ones on plow legs etc should be spun up on a lathe to have shear marks on them so yer don't get bur's when they break

 

[Paddington]

Once spent an annoying day breaking loads of shear bolts on a topper after not breaking one for years. The bolts were M8 and the hole was 9.5mm, so I reckoned the amount of slack down to the hole size was causing the bolts to break, perhaps the hole on the UJ needed to be reamed out to 10mm ? I even used a torque wrench to tighten them, perhaps it was down to snatch in the PTO clutch ? It couldn't be the bolts as they were still in the proper bag which I hadn't lost yet.
Problem solved next day as I realised dealer had given me bolts just too long to clear the yoke which was snapping them off...
You just can't get the dealers these days.
@neilo has the right idea.

 

[7610 super q]

Once spent an annoying day breaking loads of shear bolts on a topper after not breaking one for years. The bolts were M8 and the hole was 9.5mm, so I reckoned the amount of slack down to the hole size was causing the bolts to break, perhaps the hole on the UJ needed to be reamed out to 10mm ? I even used a torque wrench to tighten them, perhaps it was down to snatch in the PTO clutch ? It couldn't be the bolts as they were still in the proper bag which I hadn't lost yet.
Problem solved next day as I realised dealer had given me bolts just too long to clear the yoke which was snapping them off...
You just can't get the dealers these days.
@neilo has the right idea.

Have you not read the panmixer topic.?

 

[jamesy]

Had a new Mchale wrapper this year, one day at the dealers I remarked that I was in for shear bolts as I had gone through all that came supplied with the wrapper, I mentioned my surprise as I hardly went through any with previous wrapper. I was seemingly the third person that week to have the same problem. Got new bolts from dealer & put one in & no more problems. So you can get below spec bolts it would appear!

 

[Bury the Trash]

For our different ploughs from the same company we have different colour coded bolts - different tensile strengths - they are grooved as JD-kid described- but even then they dont always 'shear correctly' -the battle is then to punch them out without doing damage.

 

[Nearly]

Our West muckspreader had a sticker, use 12.9 grade shear pins. Still used to buy them from dealer as he bought them by the 25kg box from ironmonger so was cheaper than original parts.
Bought a plough last year and made a point of freeing all the rust off the legs and making sure the shear bolts could break before I ploughed our stony field.

 

[Wombat]

Remember them on a lely power harrow ,,shear pin cascate with ten pins to shear 4 times each one ,,they were very handy

Shame about the rest of the power harrow

 

[Lincs Lass]

Shame about the rest of the power harrow

Ye I think ours met a grizzly end after the oil escaped from the top gear box and all the casting suddely changed color