pto arm bolts

[Robins 26]

Hi all, 

 

I was just out fitting the PTO bits ive collected, but need the bolts that hold this type of PTO arm on

Any one know off hand the thread sizes? Im guessing its whitworth (unc) and are they both the same? assuming it is held on with two bolts?

 

cheers, Daniel

[gwest_ca-(File Mod) 11,493]

Is it a PT-6 pto?

https://lookup3.toro.com/partdex/index.cfm?xCaller=Toro

Item #2 is 908045-4 and 7/16"-14 x 3/4"

Item #3 is 920084-4 and listed as 3/8" but that is wrong. Should be 7/16"

Item #4 is 908017-4 and is 5/16"-18 x 3/4".

 

Garry

[Anglo Traction 761]

As Garry has said,  with one explaination. The bolt size error at TORO is a mix up. It is dependant on whether you are working on an 8hp or a 10-14hp?. The 8hp uses the 3/8" size. The rest are 7/16".

 

 Edit- missed your question ref Whitworth v UNC.

UNC  has thread angle of 60 deg. Whitworth is 55 deg. So a whitworth bolt  Will be a sloppy fit in a female  UNC nut or hole.

Also , you will have a problem trying to get a Whitworth nut on a UNC bolt.

Regards.

Edited August 25, 2013 by Anglo Traction

[Robins 26]

Thanks guys! I cleaned out the threads (full of crud) ready to get new bolts on my way to work. But in a moment of wanting to see it all together last night i picked up an M10 bolt and just finger tight wound it in to hold everything loosely, expecting it to go only a couple threads and stop, however it went all the way in   no forcing needed just light finger pressure, is that correct?

 

So in that case, are the sizes above for whitworth or UNC?

 

cheers, Daniel

Edited August 27, 2013 by Robins

[Martin 2,133]

still unc. like richard said, different thread angles.

 

havent heard of whitworth for many years. there was always whitworth bolts and nuts kicking around dads garage back home .......

 

the m10 will not suffice for a proper fit. use the proper size unc bolt.

[Anglo Traction 761]

Hi Daniel, As Martin says,  3/8" UNC is 16 threads per inch. A 10mm thread has a pitch of 1.5 tpi. The tpi is nearly the same, but every metric thread is .0034" smaller. This means that if you screw in a 10mm bolt into 3/8" UNC hole, you won't have full thread engagement over the length of bolt thread. If you apply any given torque to it, the cast iron threads in the engine block will give until they take the form of the bolt and or fail.

I personally would never use metric in unified, but that's only my opinion. It's your Tractor.

 

Edit- Sorry, I meant to type 10mm Thread pitch is 1.5mm (not tpi), so there are 16.9 metric threads to the inch on that size.  

 

Regards

Edited August 31, 2013 by Anglo Traction

[Robins 26]

Collected a 7/16 unc bolt on my way home from work yesterday and fits a treat  Thanks all, now i can adjust the PTO and try the deck out.

 

cheers, Daniel

[Stigian 1,234]

Hi Daniel, don't forget to post the action photo's of your deck working