Should I use a hammer here?

[mojoinco]

Penetrating oil -- KanoLabs.com for Kroil is the best I have ever used. Worst case (after applying heat) would be to drill out the push pin, which will not matter if you go to it from the hole at that point. If you can get it to drill out. FYI, it is spring loaded (not that much spring). Less risk of scarring your pto shaft with the grinder, but a little scarring wont matter.

To heat it, use a propane torch. Propane has the advantage that as a gas it wants to flow along the perimeter of the metal (it's cheap and portable too). The other most common process is oxy-acteylene (cutting torch type set up with a 'rosebud' tip). Propane is cheaper. You will not care if you get it real hot -- nothing wrong with red, but you will likely not need to get that hot. Do it on a cold day and your pto shaft will be smaller -- if you can heat the adapter fast enough then you will get results faster. Try no to get the flames on the pto seal. That wouldn't be good.

 

[Bill Hoffman]

For rusty stuck stuff, mix equal parts of ATF and Acetone and apply.
Works better than anything else I've tried. Have an old rusty JD
harrow. Discs on one frame wouldn't turn. Let this mix work its way
in over a couple of days, and the disc would turn by hand.

Bill

 

[Tig]

I've found that a press or puller works much better than any hammer.
Look at tie rod removers or a bearing puller.

 

[Egon]

I've found that a press or puller works much better than any hammer.
Look at tie rod removers or a bearing puller.

It would probably be best to remove the retaining pin before a puller is used.

 

[jenkinsph]

I agree with penetrating oil and time for a good soaking first. The large releasing pin can be held down with a hose clamp to facilitate removal of the coupler from the shaft, this frees up a hand to allow you to work more easily.
I would not beat on this but a few light taps might be in order.

If it is still stuck I agree with the above poster to use a puller, this would be the least damaging way to deal with it. Much better than prying against the housing and or beating on the coupler as this transfer to the pto stub and tractor..