Machinery question

I am converting my 6’ joiner/planer into a 6" drum sander. The drum will be mounted above the base as opposed to the present cutters mounted under the base. The existing motor takes 20,000 cuts per minute with a 2 blade cutting head and the head is running 1/2 the speed of the motor so I have a 2 hp, 20,000 rpm motor.

 I want the sander to run about 1500 to 1700 rpm's. I would like to use a 6" drum if possible but not sure if that high rpm motor could maintain the torque needed for a sander. What size drum do you think would be best? Of it it is a bad application for that motor I would rather just stop now.

I’m not really sure what you are after mechanically, but this: http://www.harborfreight.com/router-speed-control-43060.html should get your motor RPM down to where you want it.
A 2 HP universal motor… That’s a monster.

I wasn’t planning on slowing down the motor. I was planning on gearing the pulley down to slow my sanding drum. I never have worked with anything at 20.000 rpm before and wasn’t sure if they had enough torque for sanding drum applications.

I would guess that a 2hp motor that is capable of spinning a jointer head would have enough torque to spin a drum sander…

However, I am curious as to the why of this project? Are you planning to use the drum sander as a secondary appendage to the jointer? Are you going to use the sander as a drum sander or as an edge sander?

Inquiring mind wants to know.

I removed the joiner blade alltogether. I am mounting the drum above where the cutter head was on pillow blocks and 2" stands. This will give me about 1" clearance, the jointer has about 3/8" adjustment which is all I need. The laminations I am grinding are flat about 2" wide and I need very accurate thicknes control. I will be sending the lams through on tapered sleds that will give me the desired tapers I need.

How are you going to reduce the RPM? If you put a V-belt pulley on the motor and drum, a 1" pulley on the motor and a 10" pulley on the drum would drop the 20,000 RPM to 2000 RPM, in the range you want, buy how are you going to put a 10" pulley on a 6" drum (I guess it can be done, but it will look a bit funny and be somewhat dangerous if it doesn’t have a guard around it).

I suspect a 2 hp motor is way overkill. It might be much simpler to get a 1 HP (or even a fractional HP motor) that operates at 1750 RPM and build your own stand. Drive it with a V-belt using same-sized pulleys.

I agree that you should get a dedicated motor. You don’t need high speed or torque for a sander. Depending on the drum construction you might tear the sandpaper off the drum at 10,000 rpm or higher. You can probably construct or buy a 6" drum that can be mounted on a drill press. If your drill press head rotates 90 degrees you may be able to place that right over the joiner table to do what you want.

I am using a step down double pulley with an idler, my puleys should be about 4" each.

So this is a one time deal. How long are the lams? Have you considered jigging up a template for a router based solution? Drum sanding will be slow and very tedious. I cut my own veneers at times and the process of drum sanding them to a uniform thickness is long. Off the top of my head taking 6 pieces of walnut veneer (5" x 24") that are just over 3/16" down to just under 1/8" took me about 1.5 to 2 hours.

Watching oil dry is a more pleasant time in the shop. :slight_smile:

The motor is dedicated, I removed the cutter heads, just using the frame, motor, and bed.

The sytem I have now I can run the 2" X 36" X .140 thick in about 2 minutes. I just need finer adjustments and more accuracy. I built an adaptor for my 6x48 belt sander and it works well if not for the crown on the wheels. I also use a very course grit of paper 36 grit, as to leave deep lines for the epoxy to adhere to. I can easily take off 1/16 in a single pass but usually do about 1/2 that or less. I would like to figure about 6 pieces per hour from start to finish.

I understand, but it’s running at much too high of a speed. However, if it’s not, or the original cutter head spindle can be stepped down with different gears or pulleys, maybe you can make a drum to fit on the same spindle.

I’m looking to do something similar to put on my Shopsmith. I have the lathe tailstock to use to support the drum on both ends so I can use a long drum. The problem is the limited space between the table and the power spindle, not enough for a 6" diameter drum. I have a second table and if I remove the trunnions for table tilt and mount the table directly on the legs I may have reasonable space for material to be sanded.

I had one set up on my small lathe but it didn’t have enough power, your shop smith should have plenty. How much space and adjustment room do you need?

I’ll have to find my notes, it’s less than an inch I think with a 6" diameter drum. I want to be able to sand table tops and other panels. I’d like to finish and size heavier pieces as well, but those wouldn’t be that big that I couldn’t do it in a simpler manner. I’ve seen a few Shopsmith drum sander creations, they either uses gears or pulleys to mount offset the drum over the power head, or some kind of rigged up table resting on the way tubes. The trunnions raise the table several inches over the top of the table riser legs so if I can get the table top secure directly to the top of those legs and flat and level side to side I’ll have something good enough for my purposes.

The table will rise up over the power head though, so the other approach is to cut large rectangular hole in a table top that the sanding drum can stick through and pass the material over the top. I could rig up some kind of pressure roller or just use weights on top of the material.

You’re getting me thinking about using the joiner though. I can replace the drum that holds the blades with a sanding drum. The joiner is usually attached directly to the motor for maximum speed but I can attach it to the speed changer also. It’s only 4 inches wide though.

What information is on the motor you have now ? volts, amps, frame size , rpm , etc ?

110 v 12.5 amps, 2 hp, 20,000 rpm. It is one of those small high rpm motors.