Thread: 1/4 hp motor any good for a disc sander

My 300mm Woodfast disc sander has a 1hp motor and I wouldn't consider it over-powered.

Arron, I think you will be pushing it to use such a small motor.

I fired up my Hafco 12inch sander today for the first time in years. It has a 2hp motor!!

OK the other end of the motor shaft drives a 4inch belt sander, but you don't use both at once.

I'm pleased I have this amount of grunt as whatever I do is easy work. The area available with a 12 inch disc is
a considerable advantage also.

Mind you it could be stalled or made to work hard if used stupidly, but sanding is not all about applying lots of pressure.

If you want a 12inch sander then I suggest 1hp is a minimum motor requirement.

Of course you can use it as a sander but not with a 12" disc

Since the data is easily obtained I made a graph of disc size versus nominal HP for the machines on the H&F website.



Forgetting the Heavier Duty (HD) machines on the RHS there seems to be a clear pattern for size versus HP.
Extrapolating towards the LHS along the dotted magenta line you can see that that a 1/4 HP motor will be good for only a 3" diameter disc.

No disc/motor size is only one pair of factors. To get decent sanding happening you will not only need power but a reasonable liner speed. This means small discs have to spin faster. If a 6" sander does 1440 rpm then a 3" one should do double that otherwise sanding will take a lot longer. Take a look at the rpms that rotary handheld sanders do for some idea of what is needed.

If you want to operate in HD mode then maybe a 2" disc?

Nice analysis Bob!
Just for the record: my 1/2 HP 1440rpm 8" home-made 20 years ago disk sander gave up the ghost a couple of years ago in the middle of a job. The only foot-mount motor with the right shaft diameter I had at the time was only 1/3HP 1440rpm. I swapped the disk onto that and have been using it ever since..... Yep, I can stop it if I wantto, but I can also sand lots of big stuff and not stall it. I think a 1/4HP one would be OK for 6 or 7". Just my experience....

Well that just mucked up my plans too!

What about as a little spindle sander with what might usually get used in a drill press? Or even a little 6" (wide) drum sander or Sandflee kinda thing? That'd be kinda nice for little bits like scrollsaw puzzles and the like.

Spindle sander - say 4" (100mm) or less should work. Belt sander? Maybe 1"(25mm) wide max.....

Actually , a little spindle sander is a good idea I never thought of. Very useful to me too.
Cheers
Arron

Actually, I should have mentioned that I have three of these motors. So any suggestions for the other two. The little spindle sander is a ripper idea. For the other two....?

I made one of those sand flee rip-offs to work with my lathe a while back. It worked, but somewhat superfluous given that I have a drum and edge sanders already.

Cheers
Arron

Portable power supply, a spindle full or rubber hands, and running down the street power-slapping people in the face!!


Well, that's what *I'D* do anyway

Arron, those motors are the perfect size and speed for a scraper hone! Make a cast iron 5" wheel to fit onto the spindle - and face it DEAD flat, preferably put the entire motor on your lathe between centres (the motor body won't spin)
You the apply 10micron diamond dust in grease (from Hong Kong) to the face and hone your carbide tipped scrapers on it at 5deg...

Cheers,
Joe