Drum Sander Grit?

Last Friday I purchased a 25" dual drum sander and was wondering you could share with me how you use yours and what grit of paper you keep in stock. I got the machine wired up and running last night and was running some test pieces of rough pine through it, I had a 80 grit on the front and 120 on the back. After several passes I still had small lines running the length of the wood so I removed the paper from the front drum and did a few passes of 120, there were still lines running the length. Is this normal? what grit would someone use for finishing. I need to stain these pieces when finished? Also do you guys keep a roll of every grit on hand or just three or four grits? Would it be normal to go from 80 to 220 or should I make slower progressions? What about using different grits on the front and rear drums?
THANKS
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wrote:

I bought 60 grit and found that it was too aggressive. Waste of money for wood that just came out of a planer. 120 and 240 seem to be about right for next to final sanding. The 240 still leave the sanding lines and need to be either scraped or orbit/vibrate sanded out before oiling/staining.
Pete
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is it customary to use a different grit on each drum?

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HotRod wrote:

That's why there are two drums.
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I think Pine is not the best for testing but I like to go with the finest grit I can. I think that drum sander grit needs to be thought about differently than hand sanding.
I think I would try 120-180 or 120-150 and see if I can get some Oak to pass through and come out flat but not stall with a fairly aggressive cut and a few passes. One trick I always use is to pass the stock through one more time when I am done without rasining the table so I sand it twice on the final seeting. This seems to do a nice lite final pass and minimize the sand lines.
Even if I had 180 working I always start hand sanding at 150 after coming out of the drum or wide belt. The thing is, just a quick pass with some good 150 on a palm sander and it's smoothe enough for assembly.
P.S. Someone mentioned an orbital but I shy away from them except for flattening joints on badly jointed face frames or really rough spots. I've had to live with the little circular squiggles in my finish when I didn't notice it soon enough so now I just use palm sanders once the wood has been through the wide belt.
HotRod wrote:

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I'll give it a shot and see how I make out. Since I'm new to the drum sander this may take some time. How hard or tight are you pressing down on the wood with your initial passes? Are you actually running it just below where the motot would slow down or die? Also on my machine each roller has a small metal roller in front and behind it, how should these be set?

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The manual should give you some clue about the tension on the feed rollers. They are likely spring loaded and need to grab enough to feed without ever slipping while the drums are rolling.
I try to stay far from grinding the drums to a halt. It takes several passes to remove the compression lines from a stall. On most machines I just play with the depth bringng it up until I hear a slight engagement then let it roll. Then learn what a good increment is each pass. One the wide belt I am using now I bump it up .3mm per pass. and .2 or .1 if I am trying to do a fine pass.
HotRod wrote:

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It depends on how much wood you are putting through it at a grade.
I normally just do 80 on the drum and the rest with a ROS, but if I were to do enough to justify the setups, I would go finer.
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I start with 60 and then go to 80, and then 120.. This is with oak. Although after reading the posts here, I may start skipping 60 and just using 80 and 120.
I'm largely doing face frames and cabinent doors though with a satin poly finish. To me, the lines aren't noticable or worth worrying about. If I was doing more "fine furniture" work, I might try to do finer grits.
HotRod wrote:

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I'm actually getting a little "Sniping" near the end of the baords and was wondering if this is normal? How can I prevent this?

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This could be related to the setup on the feed rollers. Generally the infeed and out feed tables should skew slightly up from the base. I've never seen leading edge snipe from a sander but tailing edge is totally possible if a long piece starts to sage on the outfeed and lever pressure upward on the tailing end. On long pieces I usually stand at the outfeed and hold them up slightly to avoid this.
Sanders shouldn't have much snipe if any so you might want to see if they have any specifc setup info for the infeed\outfeed roller pressure. BTW, what brand?
BW
HotRod wrote:

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Thanks I'll need to experement with that.
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