motor for sanding

timothy thorpe · Post by **timothy thorpe** » Thu Dec 27, 2007 9:41 am

hi guys, i know the buffing motor needs to be at 1725 rpm. but i recently won a motor on ebay with 3400 rpm. this will be for the sanding disc, is this a good speed for sanding.

thanks,tim

hazmat · Post by **hazmat** » Thu Dec 27, 2007 9:54 am

You can use it, but it's going to be highly agressive.

Post by **KurtHuhn** » Thu Dec 27, 2007 9:58 am

For rough shaping it should be fine. Anything more than initial shaping, and it could be too fast. You may lose the ability to control the sanding once you get past rough shaping. Finer grits, like 400 or 600, may even burn or burnish the wood instead of sanding it.

Personally, I like rough shaping on my belt grinder, which runs at about 5000 SFPM, and is powered by a 3640RPM motor. When shaping/sanding above 120 grit, I use cushioned abrasives on a 1725RPM motor.

You might be able to make it work though. I've seen some folks make some real odd tools work for them in ways I would never have expected.

timothy thorpe · Post by **timothy thorpe** » Thu Dec 27, 2007 12:15 pm

KurtHuhn wrote:For rough shaping it should be fine. Anything more than initial shaping, and it could be too fast. You may lose the ability to control the sanding once you get past rough shaping. Finer grits, like 400 or 600, may even burn or burnish the wood instead of sanding it.

Personally, I like rough shaping on my belt grinder, which runs at about 5000 SFPM, and is powered by a 3640RPM motor. When shaping/sanding above 120 grit, I use cushioned abrasives on a 1725RPM motor.

You might be able to make it work though. I've seen some folks make some real odd tools work for them in ways I would never have expected.

thanks kurt, it makes sence just as long as the buffing is at the right speed.

tim

hazmat · Post by **hazmat** » Thu Dec 27, 2007 1:19 pm

Didn't you say you have a combo belt/disc sander? If so, you can rig up the disc side with a mandrel and chuck. You just have to remove some of the housing around the disc itself.

Frank · Post by **Frank** » Thu Dec 27, 2007 2:41 pm

If you don't mind the hassle of changing belts, you could rig up a pully system with 2 or 3 pulleys, giving you a couple or more different speeds.

hazmat · Post by **hazmat** » Thu Dec 27, 2007 3:04 pm

Frank wrote:If you don't mind the hassle of changing belts, you could rig up a pully system with 2 or 3 pulleys, giving you a couple or more different speeds.

The answer to this will most likely end up being McMaster-Carr

but I'll ask anyway. You can buy pulleys for this type of application, no?

timothy thorpe · Post by **timothy thorpe** » Thu Dec 27, 2007 5:22 pm

hazmat wrote:
Frank wrote:If you don't mind the hassle of changing belts, you could rig up a pully system with 2 or 3 pulleys, giving you a couple or more different speeds.
The answer to this will most likely end up being McMaster-Carr but I'll ask anyway. You can buy pulleys for this type of application, no?

thanks guys ,i'll look into it!!

Post by **KurtHuhn** » Thu Dec 27, 2007 6:19 pm

Yes, Mcmaster-Carr would be a on-stop-solution for all the crap you need to make a variable speed tool out of a single fixed-speed motor. Your shopping list will include:
- a couple pillow blocks
- a shaft
- two step pulleys (one for the motor, and one for the shaft)
- a v-belt
- work arbors for the shaft ends.

This type of setup is best for buffers, but can be adapted to disc sanders with little trouble.

Frank · Post by **Frank** » Fri Dec 28, 2007 3:23 am

What he ↑ said. (chuckle) I knew I could leave it up to Kurt to supply a parts list. Lazy me!

Post by **KurtHuhn** » Fri Dec 28, 2007 8:51 am

Frank wrote:What he ↑ said. (chuckle) I knew I could leave it up to Kurt to supply a parts list. Lazy me!

I just recently bought a few of that exact same parts list for another project, so I had it handy. If anyone wants the McMaster-Carr part numbers, just shout.

timothy thorpe · Post by **timothy thorpe** » Fri Dec 28, 2007 9:01 am

KurtHuhn wrote:
Frank wrote:What he ↑ said. (chuckle) I knew I could leave it up to Kurt to supply a parts list. Lazy me!

I just recently bought a few of that exact same parts list for another project, so I had it handy. If anyone wants the McMaster-Carr part numbers, just shout.

hey kurt, were would i buy round sand paper to wrap around a disc like a french wheel.

thanks,tim

hazmat · Post by **hazmat** » Fri Dec 28, 2007 9:01 am

KurtHuhn wrote:
Frank wrote:What he ↑ said. (chuckle) I knew I could leave it up to Kurt to supply a parts list. Lazy me!

I just recently bought a few of that exact same parts list for another project, so I had it handy. If anyone wants the McMaster-Carr part numbers, just shout.

I'm shouting over here!

Post by **KurtHuhn** » Fri Dec 28, 2007 9:56 am

hazmat wrote:
I'm shouting over here!

This is what I used, your list may vary slightly:

Code: Select all

1. Two pillow blocks, 7/8" center height, single sealed - 5913K42
2. Keyed shaft, 12" long, 5/8" diameter - 1497K141 
    (or)
   Unkeyed shaft, chrome plated, 5/8" diameter - 5947K14
3. Key stock 3/16"x3/16", 12" long (omit if using plain shaft) - 99374A100
4. Two step pulleys for 5/8" shaft (2", 3", and 4" steps) - 6213K48
5. V-belt, 4L fractional horsepower, 24" circumference - 6191K16
6. Two work arbors - 43555A25

Using these parts, you could build yourself a buffer arrangement that will last a lifetime. All you need to add is a motor, anything around 1/4 to 1/3 HP would be fine, and some buffing wheels. With a little thought, you could use this as a sanding station instead. Just make a disc that will thread onto the 1/2"-20 threads on the work arbors, and you'll be good to go. Or, given that I spec'd 5/8" keyed shaft (standard, as far as I'm concerned) you could get a couple of Trent Rudat's french wheels and slide them right onto the shaft.

If you build it, post pics!

Post by **KurtHuhn** » Fri Dec 28, 2007 10:04 am

timothy thorpe wrote:hey kurt, were would i buy round sand paper to wrap around a disc like a french wheel.

Any good sandpaper should work. The trick is finding good sandpaper. You want the suff that has a cloth-like backing, not the regular sandpaper you might find at Harbor Freight or some other discount store. I forget what brand I get. It's red, uses aluminum oxide as the abrasive, and has stearate lubicrant coating. I get it at the local woodcraft.

That said, I don't use that stuff on a french wheel, that's for hand sanding operations only. The stuff I use on wheels is Abralon cushioned abrasives, and they're hook and loop discs that I use on a homemade disc that mounts directly on a 5/8" shaft.

hazmat · Post by **hazmat** » Fri Dec 28, 2007 11:57 am

Alright, Kurt... I know what the bulk of these parts are, but what is the difference between a keyed and unkeyed shaft? Also, what is keystock? I'm assuming this has something to do with the belt drive aspect of the arrangement but assumptions always seem to get me in a bind

This setup would be a double-ended deal, correct? You'd run the shaft through the two pillow blocks and drive the deal from the center, with work mandrels threaded on the ends. That's what I'm envisioning, anyway. Is that pretty much the idea?

Post by **KurtHuhn** » Fri Dec 28, 2007 12:56 pm

If you look at your motor shaft, chances are, it will have a slot that's about 1.5" long, 3/16" wide, and 3/32" deep. If so, that's a keyed shaft. If not, it's unkeyed.

A keyed shaft just gives you some security against having the step pulley's break free of their set screws and rotate around the shaft instead of turning it. The use of keys shafts and pulleys means that you don't need to worry about that, since the key will lock the pulley into position and the set screws are only there to keep it from sliding along the shaft.

To assemble, you cut a piece of key stock to however wide the pulley is, and lay it in the keyway. Then you slide the pulley onto the shaft, lining up the keyway inside the pulley with the keystock, and position the entire shebang where you want the pulley. Now the pulley can't rotate around the shaft at all, even without tightening the set screws, like it could on an unkeyed shaft.

As you've guessed by now, the keystock is square bar that's undersized to fit in the 3/16" keyway of the shaft and pulley.

This would create a double-ended setup, correct. Exactly as you've described. The only difference is that the work arbors won't thread onto the shaft, they're just attached with set screws.

hazmat · Post by **hazmat** » Fri Dec 28, 2007 1:38 pm

Gotcha. Thanks for that, Kurt. Looks a little bit like I'm going to have a project on my hands for the new year.

hazmat · Post by **hazmat** » Fri Dec 28, 2007 2:17 pm

Kurt.. one more

and I think I'll have all I need to get started on this. How did you mount everything up? Did you just bolt the pillow blocks and motor to a workstation or did you set the thing up as a stand-alone unit? I've seen soooo many various setups for these types of things and have a general idea of which direction I'm going, just not real solid on that. I have limited space and don't want to get more elaborate than I have to. Thanks!!!

Frank · Post by **Frank** » Fri Dec 28, 2007 2:56 pm

hazmat wrote:Kurt.. one more and I think I'll have all I need to get started on this. How did you mount everything up? Did you just bolt the pillow blocks and motor to a workstation or did you set the thing up as a stand-alone unit? I've seen soooo many various setups for these types of things and have a general idea of which direction I'm going, just not real solid on that. I have limited space and don't want to get more elaborate than I have to. Thanks!!!

Matt, Kurt can fill in the other details for you, but I thought I'd mention a handy setup arrangement. If you mount the motor on a hinged board underneath the pillow block setup, then gravity will take care of belt tension, making belt changes for speed change very easy. If this description doesn't make sense I'll post a sketch, unless Kurt or Jack beat me to it.