Model Boat Mayhem

Mess Deck: General Section => Model Boating => Topic started by: Vaas on January 09, 2013, 09:54:47 pm

Title: props
Post by: Vaas on January 09, 2013, 09:54:47 pm

What is the difference between screw, m4 and m5 props?

Title: Re: props
Post by: Neil on January 09, 2013, 10:02:18 pm

just the diameter of the shaft that the prop fits on............
in simple terms an M4 propellor is a prop drilled and tapped to fit onto a 4mm diameter thread (actually about 4.3mm) and an M5 prop is to fit on a 5mm diameter thread (again slightly larger at 5.3mm)
 
neil.

Title: Re: props
Post by: NFMike on January 10, 2013, 12:12:25 am

Quote from: Neil on January 09, 2013, 10:02:18 pm

a 4mm diameter thread (actually about 4.3mm) and an M5 prop is to fit on a 5mm diameter thread (again slightly larger at 5.3mm)

I don't think that is right. M4 and M5 (and I believe other sizes) of male threads are never more than the nominal diameter and usually a tad less. An M4 propshaft is a 4mm steel rod with an M4 thread cut on each end, so the threaded part can't be more than 4mm. Close M4/M5 clearance holes are 4.3/5.3mm.

Title: Re: props
Post by: davidjt on January 10, 2013, 11:13:55 am

hi,
 
i have just been drilling some M5 threads for a job and useing 4.2 drill for hole and M5x0.8 tap and fits snug, so M4 will be 3.5mm drill hole. allways use less size hole not bigger
 
david

Title: Re: props
Post by: w3bby on January 10, 2013, 01:27:24 pm

M4 coarse is 3.3mm drill, M4 fine depends on the thread...

Tap size chart (http://www.custompartnet.com/quick-tool/tap-size-chart)

Title: Re: props
Post by: PLAcard on January 11, 2013, 10:25:57 pm

As W3bby included, use the tap chart to identify the correct drill bit to use.  Especially on fine threads, otherwise as soon as you tighten up, the threads could strip.  Always when tapping threads make the tap wrench or tool is straight as wonky threads cause problems.  Best of luck!