lapping compound ?

Please explain this lapping procedure for installing a prop.What lapping compound is good to use & were do you get it. Do I just put it on the shaft & spin the prop by hand for a bit without the key in place ? What does this do ? Allow the prop to go further up the shaft? Thanks , Dan.

after done lapping and when installing the nut i will put a small amount of grease or never sieze on the nut face that contacts the prop, it wont gall and will allow the nut to turn easier once it makes contact,

Thanks for the advise. I guess I got lucky cause my 1 year old 542 popped off with two taps on a piece of wood against the prop. Two light taps on both sides off the back of the prop.Question - Can I reuse the key? It's 1 year old & the shaft put a line down it. It still goes in easy. Thanks, Dan

Dan, You can reuse the key. Remember that it is the taper that does all the work. The line in the key as well as you being able to remove the prop with "two light taps" on the prop tells me someone didn't put in on correctly! The reason prop pullers are made is because they are required to pop the prop off a well fit taper. You really want to get some lapping compound and lap on the new prop. After you have twisted the prop with the lapping compound several times, remove it, wipe it down and look for different color areas. These areas will be the high spots that the lapping compound is working on. Continue until the whole taper is almost even.

The taper is a great idea. The most common use of it is the drill chuck on the end of a electri drill or cordless. The chuck has a female taper and the drill a male. No keys or splines!!

in dans case if the key was absent the prop s would have spun on the shaft so i should say the key keeps the prop from turning on the shaft, but is the taper that holds it

don't get excited about the lapping compound you really don't need to do it as long as when you tighten it down with the keyway in place and it doesn't cover the mark you made when the key was removed when you trial fitted the prop.

Eric, It is a recommended procedure by the prop manufacturers!

Does the drill chuck fall out of the shops drill press spindle too?

Lapping in the prop is just one of those little thinks that I'll bet 95% of people putting on props don't do. I will confess, that I do not do it unless I suspect a problem with the taper fit.

anthonylizardi wrote: I have seen lapping compound when resetting valve. Probably is the same procedure.

Yes.....you are doing the same thing to the prop and prop shaft as with the valve face and seat. That is to say lapping mates the two surfces together for maximum surface to surface contact.