Any suggestions on how to get the props on this 10 inch build tight?  Never had this problem until now.  I'm thinking it just needs some sort of friction material to give the props something to bite into.  Maybe the Graupner props are just fussy.

I used to use a strand of dental floss (between shaft and prop) on some small micros where the prop hole was slightly oversized. Those were press-fit though. Seems like on a big motor you could just use nylok nuts tightened down (with a washer if you run out of threads).

Yeah....not working.....plenty of threads...using nylocs....still slip...and using a substantial amount of torque.  It's like the props are rock hard and the knurling on the mating surfaces can't get a bite.  Maybe a thin rubber washer will work.

Some of the sandpaper for mechanical sanders that has the adhesive on on side. Cut a disc and crate a doughnut for between the prop and the motor?

Maybe just rough up the surface that the bottom of the prop sits on a bit?  Weird though. in this pic of my big bird that runs 12" props, they just go on normally with a standard nyloc nut and I've never experienced any slippage

Weird....the top and bottom surfaces are lightly knurled, or fluted for grip....iI'll take some pics.

I'm a little embarrassed I didn't see this before.  The Graupner spacer is a little too long for the Graupner prop.  After trimming it down the props tighten like they should.  I think Graupner should be embarrassed as well.

So the spacer is too tall??? Who would have thunk that! Do they work okay once trimmed down?

Yup, all is good now...

Nice find.

Outrageous I tell you! for the price they charge for Graupner props, you'd think they could at least get the spacer length correct. Glad you got it sorted