For those with double drum sanders

[Tony Zaffuto]

For anyone with double drum sanders, such as the General International 25" sander I have, the drum adjustments can be confusing: set both drum to same height and then lower the outside (discharge drum) a bit lower than the infeed, with paper installed. There is an easier method: set both drums to same height, then install the heavier paper on the first drum (for me 120 grit), and lighter paper on second (150 grit for me). Run a piece of wood through so it touches out on the infeed roller, stop the sander, and lower the second drum an index mark or two. Run another piece of wood through to see if both drum touch out. If not, lower the second drum another index mark or two. For my General, the outfeed roller touched out at 6 index marks lower than the front. Went through several dozen passes of white oak, came out perfect, with no loading of the sandpaper or burning.

[Mike Cutler]

Tony

Thank you for the tip. I'll have file it away. Last time I adjusted them I sat there with a dial caliper for about an hour. This method sounds much faster.
I have a Steel City 27" dual drum sander. It sounds as if the General and the Steel City have the same basic adjustments.

[Tony Zaffuto]

Tony

Thank you for the tip. I'll have file it away. Last time I adjusted them I sat there with a dial caliper for about an hour. This method sounds much faster.
I have a Steel City 27" dual drum sander. It sounds as if the General and the Steel City have the same basic adjustments.

About a month ago, I went throught the same exercise, except I used my machinist 1-2-3 blocks. The instructions that came with the machine were an exercise in futility, and caused lots of paper loading and burning, no matter how light my cut. I believe the problem was assumptions by the manufacturer of the sander thinking that users would order pre-cut paper from them, and they didn't take into account the difference in thickness of paper from different makers.

[Bill Dufour]

About a month ago, I went throught the same exercise, except I used my machinist 1-2-3 blocks. The instructions that came with the machine were an exercise in futility, and caused lots of paper loading and burning, no matter how light my cut. I believe the problem was assumptions by the manufacturer of the sander thinking that users would order pre-cut paper from them, and they didn't take into account the difference in thickness of paper from different makers.
Even from the same maker using the same paper and amount of glue I would think the bigger coarser grit paper would be thicker then the finer grit stuff.
Bill D.

[Tim Bueler]

I got my DDS used and it had been pretty well abused. I fidgeted and futzed with it for a long time and eventually came to do pretty much exactly as you explained. To set the drums at the same height I removed the sandpaper, loosened the bolts, then raised the table up just so the pressure was taken off the drums. This not only got the drums the same height, it also got them parallel to the table...which the previous owner also had screwed up.

[Tony Zaffuto]

I figure many drum sanders must come up for sale when the owners get them our of adjustment, either by fussing with parallelism or height adjustment between the two rollers. If I would have stayed with General's instructions, I would have gotten rid of the machine!

[John Sincerbeaux]

I bought my General Int’l DDS (new)years ago. Never could establish the love for it. Even the tech support said it was a poor design. I sold it for pennies on the dollar cuz of guilt.
IMHO, Drum sanders are like toys imitating machines.

[Tony Zaffuto]

[QUOTE=John Sincerbeaux;2922519]I bought my General Int

That's exactly where I was heading with my General sander. In fact in another thread on SMC, I believe I stated I preferred my Performax 16-32 over the General. However, with abandoning the General instructions, I finally have it singing. Machine was bought at least 4 years ago, and my issue has always been with using bulk paper rolls, could never get it to work with both drums, without burning/loading, when adjusting the machine per the General instructions. There was a time when I would only use the front drum, and that was when I figured to unload the boat anchor.

[John Sincerbeaux]

I know guys have had success with using a Velcro type modification for the drums which helps prevent burning.
I always recommend guys spend a little more for a 24” wide-belt.

[Mike Kees]

Tony I have been meaning to search the archives on here. A couple of years back there was a guy who posted how he had figured out how to adjust the G.I. machines and he went on to buy two or three more for cheap for his friends and relatives. Remember that they worked very well once adjusted. I bought a Canwood sander,same machine as the General International. So far I have not played with it much,however I just finished the dust collection for it so that will change shortly.

[Tony Zaffuto]

Tony I have been meaning to search the archives on here. A couple of years back there was a guy who posted how he had figured out how to adjust the G.I. machines and he went on to buy two or three more for cheap for his friends and relatives. Remember that they worked very well once adjusted. I bought a Canwood sander,same machine as the General International. So far I have not played with it much,however I just finished the dust collection for it so that will change shortly.t

Mine works fine now that I ignored the GI instructions. First, I adjust both front and back rollers to be parallel to the table and at same height (I used machinist 1-2-3 blocks). Next I mounted paper on both front and back rollers-120 on front 150 on back, with the 120 a bit thicker. Next I adusted for thickness and fed lumber through the machine, and lowered the rear (150 grit) drum (each side of the drum had an incrementally marked dial) until it began sanding. Worked like a charm, after lowering about 6 marks.

[Mike Kees]

Tony why two different grits ? I know a lot of people do this but it never made sense to me. If you do several passes then the 120 will be scratching up the 150 from the last pass, how does that speed up the process ? The little I have used my machine I had the same grit on both drums,worked great.

[David Kumm]

I ran a Performax and then a Supermax double drum for years, generally with 80 and 120 grits. You get so you can feel how the two heads are sanding by watching and listening to the motor ( or the amp gauge ) as the stock passes both heads. I always tried for a light pass on the first drum and a lighter pass on the second drum. The higher grit will have a tendency to want to burn so you only want to lessen the scratch pattern of the 80. Drum sanders are excruciatingly slow so the 80-120 combination allowed the project to be completed in a reasonable period ( or at least before death ). Due to the thinner paper on the second drum it needed to be set lower and that was also the drum that needed to be exactly level with the table. It doesn't take long before you can tell which head is doing more work.

I went to a single head WB which speeded up the process but with gentle use, the double drum worked well. Dave

[Mike Cutler]

Tony why two different grits ? I know a lot of people do this but it never made sense to me. If you do several passes then the 120 will be scratching up the 150 from the last pass, how does that speed up the process ? The little I have used my machine I had the same grit on both drums,worked great.

Mike
I run 80/120 on mine, front/back.
While it is true that the 80 will scratch up the 120, on multiple passes, but the final pass through should fine. I can also see how the grits on both drums should work well also.
I don't consider the drum sander to be the final surface prep personally. For me that is done with ROS's at 150/180/220.
Hmmm, maybe I should just use the same grit on both drums.

[Tony Zaffuto]

Update after at least another hour runtime: with present way of adjusting, both infeed and outfeed rollers just beginning to show slight amount of wear. Definitely way better than factory adjustment and paper. For the record, I took advice from another SMC thread and oredered paper from "Industrial Abrasives".

The General has plenty of power, and it is advised to not try to take too much off per pass. 120 on first roller and 150 on the second. No reason to worry about the 120 leaving scratches-I wet the oak with some mineral spirits and none were evident.

[Alan Schaffter]

Mike
I run 80/120 on mine, front/back.
While it is true that the 80 will scratch up the 120, on multiple passes*, but the final pass through should fine. I can also see how the grits on both drums should work well also.
I don't consider the drum sander to be the final surface prep personally. For me that is done with ROS's at 150/180/220.
Hmmm, maybe I should just use the same grit on both drums.

*This is a point many folks don't realize about a dual drum sander! You waste either the fine grit on the coarse passes or the coarse grit drum on fine passes.

The (only?) benefit to two drums is not having to change grits for the final pass. I came up with a design that eliminated this. I had already upgraded my 24" Grizz G1066 with a variable speed conveyor, but planned to modify the drum assembly too, but never got around to it. Essentially I was going to mount the drums and bearings on a dual rocking mounting plate assembly- plates pivot in the middle. Only a limited amount of rock (1/4' or less) is needed. "Rock" the drum assembly towards the in-feed and only the coarse grit contacts the stock. Rock it towards the out-feed and only the fine grit contacts the stock. Use the coarse grit drum until the desired thickness is achieved (of course drum sanders should not be used as thickness sanders :D ) and the only marks remaining on the stock are those made by the course grit. Then switch to the fine drum. There would be finely adjustable stops under each end of each mounting plate

Other possible options included, pneumatic vs mechanical drum selection, bi-directional belt motion, automatic direction change, rotating bristle dust brush adjacent to the out-feed drum.