My guess would be that the resin handle was injection-molded onto the blade, and therefore it's probably not possible to remove the blades with the handles intact. And as they appear to be from different makers, even if you could remove the fittings, those from one might not fit on the other. Specifically there's no little indent for the crest badge on the sgian brew, so it'd just be floating on the surface and would likely look like it doesn't really belong there.

If it's a sgian brew with a jeweled pommel and a crest badge that you want, you can get them directly from Gaelic Themes (via their parent company, St. Kilda): https://stkildastore.com/Clan-Items/...Scottish-Crest There's a choice of six stone colors, thistle or knotwork fittings, and just about any crest badge...and the sheath is included. I'd recommend simply getting one of those and selling or giving away the ones you have, rather than risk destroying both of them in an attempt to recreate it.