A question for the people who tune and repair springers

I place the new seal on a flat surface, table, and while holding the piston in a vertical manner insert the piston seal LIP into the seal and push down while twisting at an angle. A small amount of GPL-205 helps. Then after lubing the piston/seal insert the piston into the receiver being very careful to not damage the seal front edge. Pic of a new HW95 seal, top view.

Current OEM HW95 Seal.1628363057.jpg
 
 
Aftermarket urethane seals that tend to be a little harder can be made slightly more pliable by putting them in hot water for a little bit. Coffee cup of water in the microwave, get it steaming, remove and drop in seal and wait till it softens up. Then install. But be advised, rough handling on dovetailed type seals can tear them easier this way so use a little caution and some kind of lube (TX200, Diana, etc)

As for sizing the seal to the compression tube, this is the most important part to a good, temp stable, and efficient tune. I use a lathe and a whetstone covered in emory cloth to remove material. A drill press will also work. 
 
Aftermarket urethane seals that tend to be a little harder can be made slightly more pliable by putting them in hot water for a little bit. Coffee cup of water in the microwave, get it steaming, remove and drop in seal and wait till it softens up. Then install. But be advised, rough handling on dovetailed type seals can tear them easier this way so use a little caution and some kind of lube (TX200, Diana, etc)

As for sizing the seal to the compression tube, this is the most important part to a good, temp stable, and efficient tune. I use a lathe and a whetstone covered in emory cloth to remove material. A drill press will also work. 




The hot water trick is what did. Even then they can be a b$%&h to get on.
 
Try this method for ANY seals that are "through the center/button type". Find an electrical wire nut that has a base slightly larger than the button itself. Lightly lube the wire nut and place the seal over the small end and the large end of the wire nut on top of the button. Then simply push the seal and piston together, the wire nut acts like a wedge to open the seal uniformly larger than the button head. You may want to do this on a wooden board that has been drilled out larger than the button or use a small pipe section with an inside diameter larger than the button. I install seals on a Diana's in seconds using this "wedge" technique without any need of heating or prying. 
 
No expert, just a home workbench wannabe tuner but the boiling water trick then the angled press on just like Raden does has worked for me.

For sizing, I'm probably doing it wrong but I usually measure the old piston seal vs the new one, then try to size the new one somewhere in between both numbers to leave myself wear in/settle in room.