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Building own thickness/drum sander, question

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Forum topic by jbrukardt posted 05-24-2012 05:23 PM 2563 views 0 times favorited 9 replies Add to Favorites Watch
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jbrukardt

26 posts in 1701 days


05-24-2012 05:23 PM

most the time the drum itself is made out of about 50 slices of round MDF, that seems like a pain in the butt to me. Would there be any downside to making the drum out of a hefty piece of 5 or 6 inch pipe filled with something for rigidity?

planning on using these plans: http://woodgears.ca/sander/plans/index.html


9 replies so far

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Milo

869 posts in 2784 days


#1 posted 05-24-2012 05:31 PM

I used velco strip sand paper on mine.

Here’s the link to my blog on it. Maybe it will help(?). Not exactly the same project though.

http://lumberjocks.com/Milo/blog/17049

Milo

-- Beer, Beer, Thank God for Beer. It's my way of keeping my mind fresh and clear...

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jbrukardt

26 posts in 1701 days


#2 posted 05-24-2012 05:33 PM

Cool cool, so the PVC works ok, no major flex or deformation issue (would use the velcro paper just like you did. I was wondering if there was a reason you must have a solid core spindle, but wasnt sure.

Granted, mine is going to be a lot bigger in diameter than yours too though

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ChrisFranklin

23 posts in 1655 days


#3 posted 05-28-2012 04:54 PM

Couple of observations:

Velcro paper is pretty soft for a drum sander, IMO, if you want an accurate surface.

Mine is the normal MDF drum, with a WEST epoxy finish. The WEST has softened slightly in use, leaving an imprint from the paper, which indicates the surface of the drum is getting to a temperature of 150F or more—but I don’t think that heat is going very deep into the drum.

Mine is reinforced with 4 allthread steel rods through the drum to stiffen it, but it still flexes slightly (the drum is 26” long with a 3/4” mild steel shaft). A second pass without adjustment pretty much takes out any resulting curvature though.

If you’re going to be sanding thin things (guitar parts in my case), I would make the infeed table long enough so you can put the whole piece plus the edge of your pusher on it before it touches the drum. I wish I had made mine at least 24” from the drum to the edge of the table. (Edit: the key is you need to push the work through with one smooth unhesitating shove to get a reasonable snipe-free surface. I find I want to shove with my hip. Stopping, or even slowing down, to fit a pusher is a no-no; it’s got to be part of the original shove.)

Some kind of hold-down ahead of and behind the drum will make for a much smoother finish. I use Formica flaps about 4” wide right across the sander, which push down on the work as it goes through, but anything with a little flex would do it.

Build it heavier than you think you need.

-- Mud thrown is ground lost.

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jbrukardt

26 posts in 1701 days


#4 posted 05-28-2012 04:59 PM

Hmm, good observations. I will definitely extend the infeed and outfeed.

The fact that it gets up to 150 is slightly disturbing, as pvc starts to distort at 170. I also have a central rod of 3/4s, in black iron pipe though (natural gas pipe), couldnt find anything else locally.

Ill have to keep a close eye on the spindle to make sure it isnt getting hot enough for deformation.

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Milo

869 posts in 2784 days


#5 posted 05-28-2012 05:28 PM

Sorry for getting back late…

YES, I have a solid core. I cut out MDF circles (2”) and ran them down the threaded rod. This is not perfect, the plugs left air space in the tube. Then I plugged on end of the pvc tube and poured some fiberglass resin I had laying around down the tube. Again, not rock science, I winged it. Left the tube vertical over night. Seemed to work out fine in the end. I then covered the tube with velcro (twisting it like a biscuit tube) and used velcro sanderpaper to cover it.

Kept it as KISS as possible. It’s not perfect, but it works!

Milo

-- Beer, Beer, Thank God for Beer. It's my way of keeping my mind fresh and clear...

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jbrukardt

26 posts in 1701 days


#6 posted 05-28-2012 06:02 PM

Im really trying to avoid cutting mdf circles :/ The fiberglass resin is a good idea. I may try a test spindle where i fill it up with foam packing peanuts or something else lightweight to decrease the volume, and then pour it full of resin like you did, then jump on it a few times and try to flex it, etc.

Since mine is 5 inch pipe, the walls are significantly thicker than your small pipe already, so i think thats to my advantage, as i can easily flex 2 inch pipe with my hands, but sure as heck cant flex 5 inch pipe

View YorkshireStewart's profile

YorkshireStewart

1130 posts in 3366 days


#7 posted 05-28-2012 08:46 PM

jbrukhardt – The beauty of using the mdf sandwich is that the resulting roller can be perfectly trued up via an abrasive covered board on your ‘rise and fall’ platform. I’m uncertain as to how you would ensure such accurate centering of the spindle within a 5” pipe.

Of course there’s no need for fifty laminations if you use thicker mdf. Mine has about a dozen layers from memory. Rough cut the circles. Mount on the spindle and use the sander as a lathe to rough turn the drum. Then refine with the abrasive board. You’re assured of a concentric drum absolutely parallel to the bed.

Test spindles, peanuts and resin sound, to me, like more of a pain. I hope that’s helpful.

Click for details

-- Res severa verum gaudium - True pleasure is a serious business. http://www.folksy.com/shops/TreeGems

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ChrisFranklin

23 posts in 1655 days


#8 posted 05-28-2012 10:23 PM

YStewart: Yep, using the machine to true itself up is SO COOL I couldn’t have lived with myself if I hadn’t done it that way. Like pulling yourself up by your bootstraps. And, as you say, dead accurate—after about 10 years it’s still within a couple thousandths, although if it weren’t it would be easy to touch it up the same way. I cut squares of MDF on the tablesaw, drilled a 3/4” hole in their centers, and used a simple pivot with a 3/4” pin to cut them round on the bandsaw, so when the finished discs were threaded on the 3/4” shaft they were pretty accurate already. All in all a dusty, messy process, but soon done.

The 150F is local to the surface, I think—certainly the whole drum isn’t getting particularly warm. If you are using the velcro paper I doubt that heat would be an issue anyway; that would insulate pretty well, I would think. But I do like the results from a hard surface, like a sanding block.

-- Mud thrown is ground lost.

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shipwright

7174 posts in 2263 days


#9 posted 05-29-2012 07:43 AM

I built one that actually is an accessory to a lathe or in my case a ShopSmith. I used a 24” piece of 4” ABS for the drum with nothing inside at all. I have no problems with heat buildup and it is extremely accurate. I think the hook and loop allows it to run cooler.
I agree with Chris Franklin’s comments about feed and the need for a smooth rate.

My blog describes the whole build and includes a video of the sander in action. I use it for finishing marquetry that is only 1/32” thick and I still can put pieces through three or more times without sanding through anything.

-- Paul M ..............If God wanted us to have fiberglass boats he would have given us fibreglass trees. http://thecanadianschooloffrenchmarquetry.com/

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