PTO on 8N won’t attach to mower shaft. My 8N PTO has a kind of slight flange around it that keeps the u-joint from sliding on enough to engage the

[Cycledude]

I suspect the problem is 8N Ford comes standard standard with a smaller diameter PTO shaft than newer standard sized PTO shafts, he needs to buy an adapter to make the tractor PTO a bigger diameter. Places like Tractor Supply or Fleet Farm usually have those adapters in stock.
I just don’t recommend using a 3 point hookup mower on a 8N Ford tractor because the angles the PTO has to run at when raising-lowering the mower are just to sharp and lead to expensive to fix problems.
When I bought my rear 3 point hookup Bush Hog type mower over 40 years ago the dealer specifically warned me not to use it on 8N Ford tractor because it would lead to serious PTO problems.

 

[Bentrim]

That flange is used to screw in a safety cap when the hydraulic is needed but nothing is driven by the PTO, yea I know most of those caps have been relegated to the scrap heap many years ago. The cap also keeps grass and strings from wrapping around the shaft.
Originally those tractors were equipped with an 1 1/8 shaft, many extensions were made to convert them to 1 3/8 which became the standard for 540 PTO's.
Dad had an 8N and it used an extension that boled on where the sway chains bolted on, don't remember but it was between 8 or 12 inches long, the tractor was 1 1/8 the extension was 1 3/8

https://ntractorclub.com/manuals/accessories/Accessories%20for%20the%20Ford%20Tractor%20-%201948.pdf

2nd page top center


Why an over running clutch?? On a rotary mower the blades act as a flywheel, and on a transmission driven PTO the mower can "drive" the transmission so when you depress the clutch the mower will continue to keep the tractor moving. Oh you wanted to stop at the fence, sorry the mower pushed you thru the fence. THINK SAFETY!!

Overrunning Clutch-PTO Overrun Clutch

An overrun coupler attaches to a tractor's PTO shaft and drive shaft of the implement. It has a 1-3/8

www.agrisupply.com

https://www.tractorsupply.com/tsc/product/speeco-over-running-clutch-adapter-male-spline-1-3-8-in-x-6-27114899--1

The above over running clutches are for 1 1/8 tractor to 1 3/8 implement -- If your tractor has been converted to 1 3/8 they will not fit.

But these will,

Overrunning Clutch-PTO Overrun Clutch

An overrun coupler attaches to a tractor's PTO shaft and drive shaft of the implement. It has a 1-3/8

www.agrisupply.com

https://www.tractorsupply.com/tsc/product/tool-tuff-direct-overrunning-clutch-1-3-8x6-female-to-1-3-8x6-male-75hp-quick-release-27-027

 

[Shady oak]

I prefer NeverSeize for lubing splines. A little goes a long way, and that includes your shirt, hands, arms, pants and most of the rear of the tractor!

 

[Bentrim]

I prefer NeverSeize for lubing splines. A little goes a long way, and that includes your shirt, hands, arms, pants and most of the rear of the tractor!

Some if not all never seize is full of lead although some may use copper-- Be careful where you use it, and don't eat or smoke with it on your hands.

 

[Cycledude]

I prefer NeverSeize for lubing splines. A little goes a long way, and that includes your shirt, hands, arms, pants and most of the rear of the tractor!

Lots of good uses for never seize but in my opinion PTO shafts Is not a good place to use it.

 

[jwmorris]

What you need is an over-running coupler / clutch.
1. Will help keep the momentum of the mower blades from "driving" the tractor when you throttle down.

Not just throttle down. It you push in the clutch, to stop power and don’t have an over run clutch, the momentum of everything spinning will power the tractor back through the PTO.

Ford comes standard standard with a smaller diameter PTO shaft than newer standard sized PTO shafts, he needs to buy an adapter to make the tractor PTO a bigger diameter. Places like Tractor Supply or Fleet Farm usually have those adapters in stock.
I just don’t recommend using a 3 point hookup mower on a 8N Ford tractor because the angles the PTO has to run at when raising-lowering the mower are just to sharp and lead to expensive to fix problems.

As I said earlier, one can buy over run clutches that convert from one shaft to another.

The female is one size, the male, the other. This is it.

Over-Running Coupler 1-1/8" 6 Spline Female 1-3/8" 6 Spline Male

Over-Running Coupler, 1-1/8" 6 Spline Female, 1-3/8" 6 Spline Male.

www.tractorpartsasap.com

Or he can remove 4 bolts and simply change the shaft to the larger 1 3/8 diameter if he wants.

1-3/8 INCH 6-SPLINE PTO SHAFT, 30-7/8 INCH LONG - FOR TRACTORS 9N, 2N, 8N

qualityfarmsupply.com

I guess that guy must have not owned a 8n, we have a ‘48 and a ‘52. One almost always has a bush hog on it and the other often gets used with a flail mower. They are lower than our other tractors and allow us to mow around under the trees better than anything else we have.