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thickness sanding - how, what grits?
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Author:  bionta [ Sun Jan 07, 2018 12:33 pm ]
Post subject:  thickness sanding - how, what grits?
I have a bunch of questions about using a drum sander. I just acquired one and now I need to buy some abrasives. I have a few wraps of 220 grit, and 1 of 80 that came with the machine. I have a planer so I don't need to do really heavy material removal with the sander. But that's about all I know. I'd appreciate anything folks here could teach me about using the thing, before I go and blow a bunch of money of abrasive rolls.

When preparing tops and backs do you use just a single, coarse grit to get to the thickness you want and stop there? What grit?

Do you use a drum sander for surface prep of a joined back or top? With a rosette, even?

If you sand for surface quality, do you skip grades on the way up or always use every grit? What grit do you start with and how high do you go?

Playing around with 220 grit on cherry I found that even at the fastest feed rate and a really light cut I got some burning. Does that mean I should stop at a coarser grit or will I still see burning at 180 or 150?

Thanks in advance.
Author:  SnowManSnow [ Sun Jan 07, 2018 12:37 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Personally I take thin passes and use 120. In my limited experience the course 80 grit left pretty deep sanding marks that I had to then remove. So, the 120 seems like a good compromise and still has the grit to handle things


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Author:  Clinchriver [ Sun Jan 07, 2018 12:41 pm ]
Post subject:  Re: thickness sanding - how, what grits?
220 is just about useless on a drum sander, I'm mainly using 80 for getting close leaving enough to finish with 120
Author:  Barry Daniels [ Sun Jan 07, 2018 12:46 pm ]
Post subject:  Re: thickness sanding - how, what grits?
I also leave 80 grit on my sander all the time. Yes it is good for leveling rosettes.
Author:  Clay S. [ Sun Jan 07, 2018 12:52 pm ]
Post subject:  Re: thickness sanding - how, what grits?
"Personally I take thin passes and use 120. In my limited experience the course 80 grit left pretty deep sanding marks that I had to then remove. So, the 120 seems like a good compromise and still has the grit to handle things "

+ 1

80 or even 60 grit is O.K. for thicknessing if you don't have a planer, but 120 is a good grit for moderate stock removal, flush sanding rosettes, and as a final sanding on the drum sander - a good all around grit. I do finish sanding with a random orbit sander. On most machines changing paper is a PITA and on all the drum sanders I've used light passes are all they could handle without gumming up the belts.
Author:  Dave m2 [ Sun Jan 07, 2018 12:59 pm ]
Post subject:  Re: thickness sanding - how, what grits?
80 or even 100 grit leaves pretty deep scratches. These can easily go deeper than your intended thickness. Good for removing a lot of material but take care.

Also the abrasive can clog and again leave deep grooves. Check the abrasive every so often. I clean with the same rubber as is used on belt sanders.

They are great machines for dimensioning, not just panels but braces and all sorts.

Dave
Author:  bionta [ Sun Jan 07, 2018 1:01 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Sounds like most of you guys use the drum for leveling then? Also fine tuning the dimension. Not so much for heavy stock removal and the finish sanding happens later (by hand or ROS).

Do you see much burning with 120 on woods like cherry or maple?
Author:  Bri [ Sun Jan 07, 2018 1:16 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Drum sanders are notorius for burning, so light passes and fast feed rate seems to be the best. Finer grits tend to burn a bit more due to heat build up.
I would guess that 80-90% of my drum sanding is at 80 grit, hard and/or oily woods may run to 60.
I consider the drum sander to be primarily used for thicknessing rather than finishing, and I use an RO sander for finishing.
For me, the aluminum zirconia abrasives seem to cut a little better and run a bit cooler, though they are bit more money.
Cherry is one of the worst for burning.
The klingspor woodworking store has reasonable pricing on sander rolls.

B
Author:  bionta [ Sun Jan 07, 2018 1:24 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Thanks everyone. I'm going to get 2 rolls - 80 & 120. Maybe after getting some experience with it I'll decide I don't need to replenish both. I've been looking at Klingspor and was considering the Aluminum Oxide. Now I'll check out the Alum. Zirconia. I was thinking of getting some of that for the belt sander.

While I've got you here, has anybody tried one of those urethane conveyor belts?
Author:  Clay S. [ Sun Jan 07, 2018 1:29 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Buying 100+ foot rolls and cutting strips to length is cheaper than buying ready made rolls.
I will reverse ends of the board to alternate edges (left to right) to compensate for small differences in drum height (not that critical, but easy to do)
Author:  Hesh [ Sun Jan 07, 2018 1:36 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Hey Bob!

I used 120 and 80 with my Performax 10-20 with great results. Some tips that I learned are below and hopefully will be of value to you.

1). Never crank the crank more than 1/8th of a turn at once.

2). Super important to have very decent dust collection and here's why. Obviously we want the dust out of our shops, homes, lungs, etc. but decent dust collection has another very important function with some thickness sanders. The more air flow we have over the drum the cooler it stays and this will greatly.... increase the life of your abrasive papers without them gumming up with varnish forming from excess heat.

I've had good results with as little as 130 CFM but got much better results with 1,100 CFM.

3). 80 grit does leave deeper scratches but that's what my Festool ROS is for. I thought that 80 grit was a bit much for spruce so I used 120 there with decent results. It is a hassle to have to change but hey no-one ever said that things are always easy...

4). Performax type machines are kind of finicky but not in a bad way. It's a common issue on the 10 - 20's that the feed belt wants to migrate to the innermost side, the right side. Replacing the belt, adjusting the guides, etc may not help.

OTOH these open ended machines are set up with a bit of flex on the open end of the drum. As such a ridge forms on the open end of the work piece when it's wide enough for double pass sanding.

I found that not only could I not stop my feed belt from migrating to the right side but that if I just left it that way the ridge nearly goes away. Go figure, an actual welcome result from what appears to be a defect.

My worries that the feed belt would prematurely wear out from hitting the right side and only the right side were unfounded. My machine with several hundred tops and the same amount of backs and sides still has the original feed belt on it. No signs of wear.

5). My results got more predictable and I stopped going too far when I recognized that because of machine flex simply putting the work piece though twice and even three times without ever touching the height adjustment continues to take a few thou off at least the first time I do it. Prior to recognizing this it was easy to go too far.

6). Contrary to my assumptions a fast feed rate generates less heat than a slow feed rate... Go figure but that's what others here shared with me and that's how my results showed things to be too.

7). Lastly on Performax type machines there is a reason when they want some space between the wraps when loading paper. Without the spaces the spring tensioner cannot work as intended and snug the paper up. The spaces are necessary so that the paper can slightly move as it's being tensioned by the tensioning arm inside the drum end.
Author:  Joe Beaver [ Sun Jan 07, 2018 2:09 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Fastest feed rate, 100-120 grit, small increments in lowering the drum, 1/8 turn that Hesh suggested is good, but you may want to pass the piece two or three times between lowerings, good vacumn, and if the piece is not to wide then send it thru at an angle. That will spread the heat out over the whole width of the paper.

Hard woods like ebony and rosewood are the worst offenders. For domestic hardwood you should be able to sand a little more aggressively than above.
Author:  Woodie G [ Sun Jan 07, 2018 2:18 pm ]
Post subject:  Re: thickness sanding - how, what grits?
We've had - at various times - a Jet 10-20, Jet 16-32, and the current 22-44 Oscillating Drum Sander in the shop. We've used 80 grit (Industrial Abrasives) and scraped/sanded the interior surfaces with the Festool 5" ROS's (exterior surfaces get sanded courtesy of the process to ready the body for binding) for prep for bending, etc. The latest generation of the Supermax and Jet drum thickness sanders have a quick drum parallelism adjuster on the bed to address Mr. Breakstone's commend on open frame sanders - it really does work well on the Jet I was able to play with prior to the 22-44 OSC purchase (which does not have this feature, but does retain the previous generation's frame mounted adjustment. Due to the width of the 22-44 and 25-50 class machines, it seems more of a 'set-and-forget' adjustment for luthiers.

Oscillating drum sanders seem to be a game-changer for small shops. We are finding that light final sanding with P220 is enough to finish up sides and plates, and all those deep 80 grit scratches that used to take some scraper work or fairly aggressive ROS work are absent. The heavy cast iron base and heavy upper and lower drum carriage castings add a good bit of rigidity to the entire tool that the 16-32 class of sanders lacks, and the 1-3/4 hp motor sands aggressively - the SandSmart light is seldom illuminated even with fairly heavy passes.

The occasionally reported issues with keeping sandpaper on the drum appear to the guys in the shop to be operator error - as long as basic drum sander loading and tensioning procedures are observed, there's less in the way of issues with the 22-44 OSC than was seen with the 10-20 or 16-32.

I will have a more in-depth report on the 22-44 OSC when I get back in the shop for more than an hour or so at a time. One thing mentioned by the gentlemen in the shop is the resistance to resin build-up...when sanding woods like brazilian, East Indian, and cocobolo rosewoods, our usual practice is to angle the plate through the sander to avoid any resin buildup...with the ODS on, it looks like there is less tendency to build resin. While the oscillation is only about an inch, but that is enough to avoid the issue with resinous woods.
Author:  bionta [ Sun Jan 07, 2018 2:47 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Yeah, pretty big price differences. Klingspor sells 58 ft for $35 (5 wraps on a 22" drum) or 163 ft. for $85 (15 wraps). That's $7 per wrap vs. $5.67 each. Precut seems to be about $10 each. The aluminum zirconia rolls are pretty pricey tho. About 40% more than alum oxide in the 58' length. Ah ... to avoid doing too much violence to my finances for the month I guess I'll stay middle of the road for now and get 58' rolls of aluminum oxide.

Hesh, I've noticed that my feed belt tries to travel to the right as you said. I noticed that the rollers are not perfectly level so today I'm going to try to adjust that. So far I've fixed a few problems with the used machine that were pretty obvious from the start. First off, the guy I bought it from expressed his bafflement that the drum was clamped onto the column in a way that allowed it to swing around in an arc. It sounded like he found that kind of annoying. I thought it was a lot worse than that (in use the drum slid down the column and cut divots in the wood no matter how tight I made the clamp). I decided I would just bolt the thing to the column even if I had to drill holes. But first, I got a manual from somebody I found via mimf and learned that the thing is intended to be bolted. Sure enough, the holes are already there. I guess the guy had been using it that way for 7 years. I gather he was not too mechanically astute (though he's made some pretty nice live-edge tables and stacked, turned bowls...). I also found that both of the conveyor belt tracking adjusters were stripped. I guess he just got it to a place where it held and tracked reasonably well and probably tried not to touch it. No biggie - easy enough to replace those bolts. One thing I like about the machine so far is that it's simple and much of the hardware is ordinary, hardware store stuff, easy to replace.

Happily, my drum is 22" wide so I can sand a whole top or back panel in 1 pass. I think Clay's idea of swapping the board around is still a good idea though because it doesn't seem precise enough to give perfect uniformity from side to side. Woodie, the features of those newer machines sound awesome. I’ll look forward to seeing the full review (even though I’m pretty sure I’ll never see one of them in my shop!)

I did notice on my test runs that I could run a panel through 2 or even 3 times without raising the conveyor and still take something off it so I can see what you guys mean about the usefulness of doing that. 1/8 turn seems about right too. When I got too aggressive I caused problems - the board slipped on the conveyor and the drum dug divots.

I've got my dust collection working pretty well now. I was going to make a dust hood from a length of round HVAC duct but it was too flimsy and difficult to attach the connectors to so I followed Don Parker's lead (thank you Don) and used thin plywood. Unlike his, my machine doesn't have 2 columns and the cantilevered strut that the drum hangs from leaves less room to attach the dust hose so I ended up with two 4" tubes instead of the single 6" that he used. I have the same dust collection system he has (Clearvue cyclone with 6" ducts) so there's plenty of airflow. Here’s a pic:

Attachment:
IMG_1610.JPG


Altogether, for my $450 investment and a couple of days f*rting around with the machine to get it working well, I couldn’t be more pleased. Now if I can just arrive at an arrangement in my tiny shop to relieve the congestion a bit, life will be great.

Thanks everyone, for all the help!


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Author:  meddlingfool [ Sun Jan 07, 2018 3:32 pm ]
Post subject:  Re: thickness sanding - how, what grits?
I use 60 grit for initial grinding after jointing the plates. I put them through at an angle so the glue line is spread over more of the belt.

Once I have the piece leveled, I will put it through with the grain and do the majority of material removal.

Then I switch to 100 and put it through to about .015 oversize, being careful to get out all the 60 scratches.

Then I switch to 180 and take it to final specs.
Author:  JSDenvir [ Sun Jan 07, 2018 4:09 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Hey Bob, no advice I’d argue with here. A couple of little things. I use 80 to thickness, and then sneak up on my final dimension. Once you think you’re getting close, put it through a couple of times without adjusting the height.

I then switch to 120 to bring it to within a hair of my final dimensions.

I use 80 on tops only if they’re really thick, and even then, switch over to 120 well before my final thickness.

To reiterate what some others have said, don’t try to get too close with the 80. It’s amazing how much more you can end up taking off getting those scratches out.

Good luck

Steve
Author:  Mark Fogleman [ Sun Jan 07, 2018 4:31 pm ]
Post subject:  Re: thickness sanding - how, what grits?
I have that same drum sander. Make the outfeed roller further away from the drum by adjusting the nut on the side with the belt damage. It only takes a gnat hair to get it into or out of alignment so make small changes and mark the nut and side of the outfeed frame once you're good to keep track of the location.

Also...reinforce the back side of the narrow tongues of the abrasive with some fiber tape or duct tape if you will be changing grits often. They will break after 4-5 changes if not reinforced.
Author:  bionta [ Sun Jan 07, 2018 5:05 pm ]
Post subject:  Re: thickness sanding - how, what grits?
Thanks for the tips Mark. I will reinforce the ends of the abrasive. Mine have already been put on/taken off a few times. I tried adjusting the tensioners on the conveyor but wasn't able to completely eliminate the tracking skew. I saw something in one of the Performax manuals I read (can't seem to find it now or I'd quote it here) that advised checking the roller alignment by placing a ruler on the table and measuring the gap between the edge of the ruler and the roller for the conveyor belt. Then do the same measurement on the other side of the table. Left and right ends of each roller should be set to the same height for proper tracking. If not, you can supposedly loosen the bolts that affix the roller brackets to the table and tilt them a little bit to get the rollers aligned parallel to the tabletop. I haven't tried this yet but it sounds logical.
Author:  Clay S. [ Sun Jan 07, 2018 5:09 pm ]
Post subject:  Re: thickness sanding - how, what grits?
"Now if I can just arrive at an arrangement in my tiny shop to relieve the congestion a bit, life will be great. "

Putting castors on and making the machinery mobile can help a lot with over crowding in a one man shop. It doesn't work so well where you have multiple workers but for a person who only has to deal with their own workflow it can help.
Author:  doncaparker [ Sun Jan 07, 2018 5:20 pm ]
Post subject:  Re: thickness sanding - how, what grits?
bionta wrote:
I've got my dust collection working pretty well now. I was going to make a dust hood from a length of round HVAC duct but it was too flimsy and difficult to attach the connectors to so I followed Don Parker's lead (thank you Don) and used thin plywood. Unlike his, my machine doesn't have 2 columns and the cantilevered strut that the drum hangs from leaves less room to attach the dust hose so I ended up with two 4" tubes instead of the single 6" that he used. I have the same dust collection system he has (Clearvue cyclone with 6" ducts) so there's plenty of airflow.


You're welcome!

On the grits:

I used to only use 80 grit, but I now have some 120, and I am going to start using it for more things. Tops, particularly. Like everyone says, take light passes and turn the conveyor up to the max speed. Run the workpiece through a few times before raising the conveyor. Don't try to raise the conveyor more than 1/8 turn at a time.

For general thicknessing, I don't use a planer at all. I resaw on the bandsaw to somewhere outside the final dimension, then use 80 grit on the Performax to take it down to where I am leaving room for finish sanding. With the figured woods we use, I worry about what a planer will do to the wood, and I don't have the room for one, anyway. I get by just fine this way.
Author:  jfmckenna [ Sun Jan 07, 2018 6:17 pm ]
Post subject:  Re: thickness sanding - how, what grits?
I use 80 pretty much exclusively and only on the show face since that gets sanded anyway. Works great to level the rosette. I get it close to where I want it then use a plane on the brace side for final thicknessing. My sander is on casters and I simply roll it out from it's little hiding place when I need it.
Author:  bcombs510 [ Sun Jan 07, 2018 6:18 pm ]
Post subject:  Re: thickness sanding - how, what grits?
I’m surprised more folks don’t experiment with using Abranet on the drum sander. I have a 16-32 from Jet. The challenge is that the Abranet comes in weird sizes (2 3/4” and 4 1/2”) which doesn’t work well on the 16” wide drum.

Image

So what I do is trim the whole roll down to 2 1/2” when I’m ready to retire a bandsaw blade. :) Take it nice and slow and trim the 2 3/4” down to 2 1/2”. Then I can use the same taper and method for cutting the paper that is described in the manual. The only difference is my paper is 2 1/2” instead of 3”.

Image

The 120 cuts like 80 but leaves a surface like 220.

I got this tip from Mark Roberts in a video shop tour he did for a podcast.

All the same great things about Abranet but on a drum sander! Doesn’t clog, doesn’t overheat and lasts forever.

Might be worth considering.

Brad


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Author:  Ruby50 [ Sun Jan 07, 2018 6:59 pm ]
Post subject:  Re: thickness sanding - how, what grits?
I have contemplated getting one of these machines, but I go to a cabinetmaker a couple blocks away and he thicknesses everything I bring him for $20. His machine is 48" wide, oscillates a few inches every 3-4 seconds, has a 20 HP motor with a 3 HP feed motor, and the belts take about 45-60 seconds to change. We both got a kick out of a pair of ukulele sides going through this monster to .055" thick.

Ed
Author:  Haans [ Sun Jan 07, 2018 7:28 pm ]
Post subject:  Re: thickness sanding - how, what grits?
80, then 120 on the inside and 80 outside, after rosette then 120. I still left material to be sanded off in tap tuning after the box was together.
Author:  Mike OMelia [ Sun Jan 07, 2018 7:41 pm ]
Post subject:  Re: thickness sanding - how, what grits?
I’m gonna break break a lot of brains with this. But my primary hardwood thicknessing grit is 36, klingspor blue. Stuff lasts forever. I mainly switched to it because of oily wood clogging. But it works. On my 22-44 Jet Drum. The trick is to not use too much depth pressure. And to know when it’s time to switch to 80 grit. Overpressure will def create deep scratches. On a single paper, I’ve thicknesses dozens of hardwood back and side sets without ever having to clean or replace. Use angled passes. Reverse, flip. And it’s never hard to clean up with 80 and then 220 on the palm sander. Practice.
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