converting spindle sander


Corporate Member
What is the chance of converting a 4.5 inch spindle to a 6 inch spindle. I have a Sears model that is close to 20 years old. I have looked for a new sander but not a single one gives the length of the spindle in the specs. If you look hard enough for the sleeve size you can determine the spindle lenght. I have yet to see a spec for the length of travel.


Senior User
How big is the hole in the table where the spindle comes through? I think this is a limiting factor.

The drum that holds the paper is a composite of some sort, I think, and probably does add much weight as diameter increases. Although I’m sure someone better versed in physics will worth the me if I’m wrong about this!


Corporate Member
Just reading this what comes to mind is increase in inertia mass (6" vs 4.5" dia), this most likely lesser of an issue for the motor than the friction vs torque output.

Most Machines (Especially Craftsman) misrepresent the true power output of the motor, thank marketing for this. This marketing deception is rampant EVERYWHERE. Us buyers need to be informed or we get duped. The other place we see huge deception is in Lumen ratings in light bulbs......:mad: FYI 746 watts= 1 hp roughly 7 amps to 1 hp. Keep in mind all motors run between 85-90% efficiency so, in order to get a true one hp it needs to be 1.1 hp or 8amps/120 volt rated motor.......... All this is lab calculations not real life but it gets you some starting points to work with.
That said, if the motor power is ample to resist the increased friction, then it would work ok. Bear in mind the old 4.5" dia has a roughly 14" surface area and the 6" will be about 19" surface area.
Without getting into a bunch of math, this is what will increase the work burden on the motor. Surface area. The increased inertia from this will be the lesser impact on the motor except for the startup impact.
My own real life experiences have showed me if the motor is a true 1hp motor, it would work ok (assuming it is a 1to1 direct spindle) above that, you will be able to hog in on the work if that is the need, below that, you will be going slow and lighter push based on the slowing sound of the motor, and will shorten the life of the motor. Damn, I planned on writing just a couple of sentences.....

bob vaughan

Bob Vaughan
Senior User
I think spindle height is the issue, not diameter.
If the sanding spindle is removable like a lot are, then its merely a matter of having a new one made to your specs.
My sander uses 9" tall spindles. Often the 4.5" tall sleeves are available on sale so I made some spindles to take the shorter sleeves.
I think a lot of spindle sanders have a 1" stroke cycle except maybe the little plastic bench top things. Don't know about them.


Mine is an old Boice Crane that uses 9" spindles. I made some 6" ones for smaller than 3/4" diameter.
I don't think the size makes much difference on the power.T
This one has an oscillating stroke of 7/8".

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