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Designing a Drum Sander

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Forum topic by PaulfromVictor posted 01-08-2010 06:12 PM 4878 views 9 times favorited 21 replies Add to Favorites Watch
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PaulfromVictor

224 posts in 2812 days


01-08-2010 06:12 PM

Hello all.

I am in the beginning stages of designing a drum sander. I would have never considered building one without seeing and reading all that has been offered on this site, including Stewart’s, Blake’s, Dave’s and other Jock’s builds. The links and information are great. I still have a ton of questions, and will likely have more as I progress.

My plan is to build a sander with a 20-21” wide capacity. I want to be able to sand to thinness approaching 0, and thickness to be determined.

From the sanders I have seen others build, I see that typically disks are cut from MDF or plywood (still deciding on that choice too). Then the disks are stacked and glued with epoxy on a steel rod. It would seem that this would be a very weak bond. I would think that the epoxy bond would fail due to the high shear force of the spinning rod vs. the resistance created by sanding.

1. Isn’t there a high risk the bond will fail leaving a spinning rod inside a motionless drum?

2. Is a steel rod or a zinc coated rod better?

3. I will probably use some type of velco or hook and loop paper. Does it matter which direction the paper winds? How do you determine what angle to begin the wrap?

4. I have never used “pillow block bearings”. Are they closed on one side so that the rod cannot pass through?

5. From the models I have looked at, it looks like belt tension is achieved only by the weight of the motor. Is this correct?

6. I will probably get the power twist link belt. Are these compatible with all pulley types?

7. What usage issues should I expect? I will probably do a manual feed. I have heard issues of “snipe marks”, “black streaks”, and glue issues.


21 replies so far

View poopiekat's profile

poopiekat

4225 posts in 3201 days


#1 posted 01-08-2010 06:40 PM

Are you referring to a wide-belt design, or a hook-and-loop system like a thickness sander?
I’ve used scrap pulleys or sprockets with good set-screw hubs to attach drums to the shafts. Tubing, whether plastic PVC Schedule 40 or aluminum, is preferable to stacked mdf. I’ve even used heavy cardboard cores, with the ends capped with particle board, again attached to shafts by metal hubs, with good results. Zinc-coated rod has an indefinite diameter, and pillow blocks have very precise bores. Plain steel rod is best. Pillow blocks do not have closed ends, the shaft can protrude for mounting your pulley on the outside. Motor weight is the cheap and easy way to maintain belt tension. I don’t see much advantage to link-belt for this type of application. I’ve never heard of snipe or streaks Good luck!

-- Einstein: "The intuitive mind is a sacred gift, and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift." I'm Poopiekat!!

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Ger21

1047 posts in 2597 days


#2 posted 01-08-2010 07:24 PM

1) golf clubs are glued with epoxy, and they don’t come apart. Good quality epoxy is extremely strong, and if you rough up the shaft with 60-80 grit sandpaper, the bond will not break

Poopiekat, what makes tubing preferable to stacked wood discs?

2) Plain steel will offer a better bond

3)Taken from this website http://www.rockslide.org/drum%20sander.html

Simply take a piece of string and wrap it around the drum. Mark the string at precisely the location where they intersect. With the matting or paper laying on the bench, place the end of the string on a corner of the material and stretch the string out until the mark is at the opposite edge of the material and mark this point. That is the proper angle for your drum. Use a straightedge and utility knife and cut the angle. Then wrap the material around the drum (before taking off the backing in the case of the matting) and mark the other end where it meets the edge of the drum. Cut the same angle on that end and you are ready to install the material.

-- Gerry, http://www.thecncwoodworker.com/index.html http://www.jointcam.com

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poopiekat

4225 posts in 3201 days


#3 posted 01-08-2010 07:36 PM

Ger,
If Paul is going the velcro route, I’d rather be adhering the hook to either PVC or metal tubing. Easy to just cap the ends with stepped discs. Not as much an issue if he’s making a wide-belt sander, but we don’t know which, until he replies. For 30” he’d be just as well to go the belt route than the under-the-table abrasive roll. Easy just to find a commercially available common belt size and build around it.

-- Einstein: "The intuitive mind is a sacred gift, and the rational mind is a faithful servant. We have created a society that honors the servant and has forgotten the gift." I'm Poopiekat!!

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PaulfromVictor

224 posts in 2812 days


#4 posted 01-08-2010 08:45 PM

Thank you so far for your replies. Autumn, that is at least 2 cents.

I am designing a thickness sander type drum sander. I am using the following as a starting point, although, I already foresee many changes:

http://www.rockslide.org/drum%20sander.html

I have used capped pvc tubing for making an outfeed support project. It is a quick and easy way to go. I don’t see how I could use if for this though because I think it would flex a bit, but more importantly as Autumn points out is trueing the cylinder to be parallel to the table can be done with sandpaper if a wood product is used.

Regarding the snipe, I have not read elsewhere that the size of the drum can reduce the chance of snipe. It makes sense. I wonder why 5” seems to be the sweet spot that people are using on their designs. Maybe because it is found on purchased machines.

View flyingoak's profile

flyingoak

68 posts in 2575 days


#5 posted 01-08-2010 09:17 PM

The PVC drums i have seen usually have spaced disks inside the tube to stabilize it. Also you cold use Sch. 80 pipe which is twice the thickness of the 40 stuff.

just some observations
Harold

-- where is the duct tape.....

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PaulfromVictor

224 posts in 2812 days


#6 posted 01-11-2010 11:15 PM

It would not be too difficult to design a sander where the table could be adjusted down to accommodate greater thicknesses – 6”, 8” or greater.

Does anybody see this as a useful feature? I am not exactly sure why I would want that, but I am trying to have 20/20 foresight rather than my typical 20/20 hindsight.

View Broglea's profile

Broglea

677 posts in 2557 days


#7 posted 01-12-2010 06:50 AM

I’m in the middle of building one of these as well. I purchased a couple of wood rolling pins and just drilled out the center for the rod to construct my cylinder.

I am having one problem though. My 3/4 HP motor is bogging down too much and won’t spin the cylinder anywhere near the rpm I need. I’m thinking there is a problem with the pillow block bearings. I paid $14 for them on Ebay. Is there a certain rating the bearings must be?

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PaulfromVictor

224 posts in 2812 days


#8 posted 01-12-2010 05:19 PM

I purchased a 3/4 hp motor as well. Others on this site indicate a 1725 rpm need on a 5” diameter drum. If your drum is larger, you will need slower. Maybe you need to adjust your pulley sizes to get the rpm needed. I am not a whiz at figuring this. Also, I am not sure how belt length comes into play.

Here is a link for pulley ratios:

http://www.csgnetwork.com/pulleybeltcalc.html

View dbhost's profile

dbhost

5607 posts in 2698 days


#9 posted 01-12-2010 11:06 PM

I am likewise designing a wide drum / thickness sander. My ideas on your questions are thus…

“1. Isn’t there a high risk the bond will fail leaving a spinning rod inside a motionless drum?”

Not really. Epoxy is VERY strong when mixed and cured right.

“2. Is a steel rod or a zinc coated rod better?”

Plain steel. Zinc coating (galvanizing) is simply an additional layer between the steel and the epoxy.

“3. I will probably use some type of velco or hook and loop paper. Does it matter which direction the paper winds? How do you determine what angle to begin the wrap?”

I haven’t figured this out either. So I will be watching.

“4. I have never used “pillow block bearings”. Are they closed on one side so that the rod cannot pass through?”

No. Pillow Block Bearings are open all the way through. You will need some arrangement to keep the rod from slipping out. Those tap on “hat” fasteners like you see on trash can axles are an excellent means of keeping the rod in place.

“5. From the models I have looked at, it looks like belt tension is achieved only by the weight of the motor. Is this correct?”

All of the shop builts I have seen are done that way. I was planning on a swing down / gravity design with a provision to mechanically push down to tension iif needed.

“6. I will probably get the power twist link belt. Are these compatible with all pulley types?”

The Power Twist has specs that are the same, or similar to Accu-Link (the green one that is sold by Harbor Freight) which requires a pulley compatible with a 1/2” V style belt. So no, not compatible with all pulley types (Serpentine pullies will not work with a V type belt arrangement…)

“7. What usage issues should I expect? I will probably do a manual feed. I have heard issues of “snipe marks”, “black streaks”, and glue issues.”

Make sure you have plenty of infeed, and outfeed support to avoid snipe. Same thing goes with a planer… Manual feed is fine as far as I know… I have heard about Black Streaks as well, never found out why. What are you hearing about “blue issues”?

-- My workshop blog can be found at http://daves-workshop.blogspot.com

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Broglea

677 posts in 2557 days


#10 posted 01-13-2010 12:30 AM

I believe my problem exists with the rod. It is 5/8 zinc plated steel. Maybe I should have use a plain steel rod. I had one heck of a time getting the pillow blocks onto the rod. I may have damaged the bearings. It took me a lot of swings with the hammer to get the bearing on the rod. Am I correct to assume the bearings should just slip onto the rod?

View Blake's profile

Blake

3442 posts in 3341 days


#11 posted 01-13-2010 12:45 AM

Sorry, I didn’t have time to read all the posts in the feed but I can answer a couple of your questions….

  • Steel rod is fine
  • I didn’t put epoxy between the disks, I used yellow glue. Because its water-based, it will actually make the mdf disks expand and tighten around the steel rod. Trust me, it will not slip. If you ever have a problem with it slipping, just drill through one of the disks into the rod and out the other side of the disk, and insert a pin.
  • The angle of the wrap (of the paper and velcro) is based on the diameter of the drum and the width of the paper. It is determined only by trial and error. Wrap the velcro in the opposite direction you plan to wrap the paper. Cutting the first paper strip is trial and error, after that make a template for future strips.
  • I’ve never had an issue with snipe. Take light passes.
  • Power twist belts work with any standard “A” belt style pulley.
  • The motor weight, like your tablesaw, keeps it properly tensioned.
  • Pillow bearings usually have set screws to keep the rod from wandering.
  • The only other issue I have is the leading edge of the paper coming up. You need some kind of clip to hold it down. I use a staple (very low tech but simple). The trailing edge is not a problem.

-- Happy woodworking! http://www.openarmsphotography.com

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ajosephg

1878 posts in 3027 days


#12 posted 01-13-2010 12:47 AM

If you had to pound the rod through the bearings you well could have damaged them. With no belt attached you the cylinder should spin freely.

-- Joe

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papadan

1178 posts in 2835 days


#13 posted 01-13-2010 01:26 AM

I am in the thought process for one of these sanders myself. I was planning on using 6” aluminum pipe as my drum. The only thing about this thread that has me confused is the reasoning behind using plywood or MDF disc. It was stated that using these disc types will let you adjust the drum to parrellel with the table. You lost me on that one? I would adjust the table to achieve parrallelism with the drum, right?

-- Carpenter assembles with hands, Designer builds with brains, Artist creates with heart!

View PaulfromVictor's profile

PaulfromVictor

224 posts in 2812 days


#14 posted 01-13-2010 02:18 AM

dbhost – I plan to use gravity alone ro tension the belt, but plan be is a low tension spring on the bottom of the motor mounting plate with the other end of the spring attached to the frame.

papadan – aluminum pipe may make a good drum, but you will have 2 challenges. The first will be getting the rod to go straight through the center of the drum so it spins true (and attaching it so it spins), and the 2nd challenge is to make the drum perfectly parallel to the table. With shims if needed you can adjust for parallel. The benefit of doing the cylnder out of mdf or plywood discs is that when you get the bare cylnder installed, you can then use adhesive to attach sand paper to a flat board and run this under the bare drum, from side to side, etc. to smooth the drum while simultaneously making it parallel. People have been saying that this works well.

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PaulfromVictor

224 posts in 2812 days


#15 posted 01-13-2010 02:22 AM

Autumn, when you are milling your “figured stock” do you go the traditional route of jointer then planer, and when squared use the drum sander to clean up the tear out, or do you go right to the ds?

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