The Ford Barn - View Single Post - Perch Bolt Diameter? Drop in or Press in?

Joe K · 10-19-2014, 07:10 PM

It has been my experience that Perch typically are "pressed in" so your hard to fit one is probably closest to original.

Not to say that the lesser diameter one will not fit directly. IIRC, the perch emulates a cone at the top (below the spring and contacts the upper radius rod yoke) and the nut at the bottom is a virtually identical situation with the cone part being machined on the nut.

Thus when both perch and nut are in place, the perch is held as tightly as it ever will be.

I would use it.

I certainly would look at the bolt diameter charts and do a torque on this equivalent to a SAE 5 bolt. I would like to say a SAE 8 bolt, but VERY few commercially available fasteners rate at SAE 8 unless they're specifically qualified - and repeatedly tested for maintenance of quality during manufacture. The Model A spring perches are no where near this well made methinks.

Nor is it really necessary?

Looks like a 5/8" nut on that so torque will want to be perhaps 150 ft-lbs?

See http://www.engineershandbook.com/Tables/torque.htm

Joe K

10-19-2014, 07:10 PM	#3
Joe K Senior Member Join Date: Jul 2010 Location: Cow Hampshire Posts: 4,188	Re: Perch Bolt Diameter? Drop in or Press in? It has been my experience that Perch typically are "pressed in" so your hard to fit one is probably closest to original. Not to say that the lesser diameter one will not fit directly. IIRC, the perch emulates a cone at the top (below the spring and contacts the upper radius rod yoke) and the nut at the bottom is a virtually identical situation with the cone part being machined on the nut. Thus when both perch and nut are in place, the perch is held as tightly as it ever will be. I would use it. I certainly would look at the bolt diameter charts and do a torque on this equivalent to a SAE 5 bolt. I would like to say a SAE 8 bolt, but VERY few commercially available fasteners rate at SAE 8 unless they're specifically qualified - and repeatedly tested for maintenance of quality during manufacture. The Model A spring perches are no where near this well made methinks. Nor is it really necessary? Looks like a 5/8" nut on that so torque will want to be perhaps 150 ft-lbs? See http://www.engineershandbook.com/Tables/torque.htm Joe K __________________ Shudda kept the horse.