how to you measure a prop to determine it's diameter

[Boomer]

What is the correct way to measure the diameter of a propeller? I took a picture showing how I am measuring a propeller, but even with a digital micrometer, the props I measure don't seem to match the advertised diameter.

Please share the proper points to use to get the correct diameter measurement.

Thank you
Boomer

[Steven Vaccaro]

You have it right.

Lots of the Octura props wont measure what they are listed at. It seems they use different molds or experience shrinking on some more than others.

[teach]

Also as you sharpen and balance a prop, some of the tip usually will get taken off lowering the total diameter. Same for rounding the tips.

[martin]

All casting shrink when material is solidified after casting so patterns must be made larger to allow for shrinkage. I suspect some manufacturers copy other propellers & simply take their mould from some one elses finished props. Saves a fortune to take an allready good prop & just copy but you end up with an undersize prop casting because the copied original was proper finished size. By the time a mould is taken the mould ends up finished size & them when the props are cast in this mould you get the relevent shrinkage. Aluminim shrinks around 6% & copper based materials around 4%. This is why some copper based castings with no filling just flash removal should be a 40mm prop but are 38mm +. Thanks Martin.

[Boomer]

Thank you for each reply! Thought it was me. Usually is, so it is nice to know I was doing something the right way for a change!
Boomer

[Doug Smock]

Kevin Sheren made these cool tools for checking diameter while making sure both blades are the same. 3/16 and 1/4" mandrels
When I got mine I was suprised how much some of my props were off.

Doug

[westbeach]

Hey Doug, do you have a close up on one of these handy calipers? Thx

[Doug Smock]

Hey Doug, do you have a close up on one of these handy calipers? Thx

I'll post one tomorrow.
Doug

[Doug Smock]

Here you go.
If I remember right Kevin was letting these go for $65.00 shipped . You can contact him here if you are interested. Gas_dir@yahoo.com
If you get one of these be prepared to spend a bit of time with your prop box. Like I said, I was suprised how many props I had that were off. This tool is well worth the money.

Doug

[Steven Vaccaro]

Here you go.
If I remember right Kevin was letting these go for $65.00 shipped . You can contact him here if you are interested. Gas_dir@yahoo.com
If you get one of these be prepared to spend a bit of time with your prop box. Like I said, I was surprised how many props I had that were off. This tool is well worth the mo

Doug

Very cool. I have to buy or make myself one of those!!!! Probably buy one for that great price.

[egneg]

Doug is the pin on center with the jaw for the different pin sizes?

[Doug Smock]

Doug is the pin on center with the jaw for the different pin sizes?

Yes sir.
D.

[egneg]

Yes sir.
D.

Thank you, it would be good to do a quick check. This is what I use to make sure all the blades match. I can also use it to check pitch with a gizmo I made.

[dasboata]

Thank you, it would be good to do a quick check. This is what I use to make sure all the blades match. I can also use it to check pitch with a gizmo I made.

You can check pitch with that I would like to know how as pitch is checked on the face of the prop

[egneg]

You can check pitch with that I would like to know how as pitch is checked on the face of the prop

The indicator is turned 90* and a wiggler is attached.