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Mini Spindle Sander


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That's an interesting machine and he did nice job of building it.  But one thing to keep in mind for sanding is the surface speed of the paper, which is pi x diameter x rpm. When it's too fast, the sandpaper is not effective, or it wears out quickly due to the heat. For sanding a 1-3" wooden object on my lathe, I set the speed around 250-750 rpm, depending upon the wood species.  The machine might be improved by adding a variable speed control.

Edited by Bob Blarney
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I would think that the designed unit that is the subject of this thread :

is under powered.  could over heat  unless better ventilation is allowed.

does not offer a large enough surface for sanding - especially for changing bevels on frames.

 

I have built two drum sanding tables.

The spindle sanders I checked use drum with sleeve sanding media.

I dislike being tied to using disposable media that is expensive and has

limited sources. When I found sleeveless drums at Peachtree that use

9 x 11 sheet sandpaper I built to use them.  The variety od sizes is good.

At one end is a 3" dia. that is 6 inches high and the other is 1/2" dia that

is 3 inches high.  To get down to 1/2" - the rubber layer making it 3/4" is

removed.

 

The first unit had a 1/20 HP motor 1700 rpm but the shaft is 5/16".

All but the two smallest drums have 1/2" sockets.  Then the two small drums

had 1/4" sockets.  Now, they seem to have changed manufacturers and the two

small ones now also have 1/2" sockets.  I had to drill and turn adapters from

cold rolled steel rod.  That is messy and requires an involved cleanup to remove

the steel turnings from the lathe.

The 1/20 HP motor did not have enough power to mount the 6 inch drum and was weak

in removal with the others.

I thought I might get the motor that Jim Byrnes uses for his sander but it turns out to be a 

3500 rpm motor pullyed down to 1700 rpm.  I did learn about two pole motors from the exercise.

 

I bought a 1/3 hp 1700 rpm motor from Grainger that has a closed fan internal cooling component

and ball bearing mounts for the shaft.  Good bearings and ventilation for cooling is important.

It is also best to develop a design that keeps saw dust out of the motor - which is a challenge when

the motor is under the drum.  The motor has a 1/2 shaft so all of the drums will mount directly ti it.

The motor is two pole, so I wired it to a drum switch so that the drums can rotate CW or CCW.

With a 1/2" shaft, I also mount burr cutters and micro planers - but with a threaded mount , reverse

rotation does not work so well.  The commercial spindle sanders that I have looked at appear to have

a proprietary method to mount their drums that limits their versatility.  The belt sanding attachment 

on the Rigid model looked interesting, but when Harbor Freight had a stand alone 4 x 36 unit on sale

for $60, I calculated it was easier and cheaper than trying to adapt that ability to my unit.

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Klingspor is good source for abrasives, and a 'bargain box' off odds & sods might be a very good deal for modelmakers, and they have a selection of products of interest to modelbuilders:  

 

http://www.woodworkingshop.com/product/bb00010/

http://www.woodworkingshop.com/category.aspx?id=52

Edited by Bob Blarney
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Bob, my 4hp treadmill use pwm to control the speed. yours should have something similar.

 

hope this can help you understand more about treadmill motor and pwm

 

https://www.instructables.com/id/Use-a-Treadmill-DC-Drive-Motor-and-PWM-Speed-Contr/

 

 

Jaager, thanks for you information, but my spindle sander is not design for normal size woodworking project, just for model making or small project. my biggest drum is  1 3/8" wide, never had motor over heat problem before, but I will put an thermometer in it to track the temperature inside

Edited by jay913
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Jay, thanks, the treadmill motor works fine.  I just scavenged the entire electronics including the MC45 controller board and the user control console, and then also added a dpdt reversing switch.  It turned out conveniently that the motor's flywheel-pulley used poly-vee "J" belts that matched the pulleys on the lathe.  (the belt was bought from beltsforanything.com).  My only issue is that at very slow speeds (125-250 rpm), it tends to bog down under load, and then overshoot the rpm.  I suppose that it has something to do with the soft-start and the speed modulation algorithm, and maybe also the 1:2 ratio of the pulley diameters.   But all-in-all, I'm very happy with the setup because it's largely eliminated moving the belt across the cone pulleys, except for special circumstances,

Edited by Bob Blarney
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I only use mine for model work also.  I just have to shape frames and cut bevels in

fairly thick stock.  Even at 1:60 Commerce de Marseille has timbers that are 1/4" thick

and sanding a station of them is over 2 inches of Hard Maple.  That needs an

adequate motor.  60 grit paper does not take too long to remove the bulk.  When I

do the sanding, I tend to go in batches, so a session can go for a couple of hours,

which does heat a motor.

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