Practical Widebelt Sander advise needed.

[Charles Brown]

I've never had any real practical instruction with respect to the sequence of grit to use with relation to depth of scratches, etc. Let's do a little thought experiment. When you take a board of domestic hardwood (let's say walnut or cherry) off of the planer, what is the sequence of grits do you use and how deep of a setting do you use for each grit used. Let's assume both faces of the board are to be sanded.

Thanks for the help here.

[Rick Fisher]

Hey Charles.

I have a 25" SCMI and only use 150 grit .. off the planer I simply make 2-3 passes..

The problem I have found with wide belts is the volume of belts I have to buy .. I only buy 150 grit and make an extra pass or two .. after 1mm of wood is removed, its simply sanded to 150 grit..

I also sand right off the bandsaw with 150 .. same thing .. 3-4 passes..

[J.R. Rutter]

Right off the planer, I run 120/180 or even 120/220. Or like Rick says, multiple light passes work fine. The less you ask of the sander, the longer it will last and the more consistent your results will be.

As far as how deep, I would not try to take off more than 0.020" to 0.025" with 120. I have a two head machine, so the fine head is calibrated to just remove pencil marks left by the first head, which basically takes the surface down to the bottom of the scratches left by the coarse grit. If you have a single combo head, I would set the platen up as a second contact point. So start with the platen raised, sand a board, then pencil mark it and gradually lower the platen until it just erases the pencil marks on a second pass through the machine.

[Richard Coers]

Off the planer, 150 grit. Running curly maple off the planer, sometimes 80 to clean up chip out, then 120, then 150. Other advice would be for ring porous wood like red oak. Go too fine with it, and push it a little, and you will get wavy grain for irregular sanding of the early and late grain. I've always been a fan of a stroke sander for furniture work. Not nearly the deep scratches from the grit like a thickness sander. I've never run a really high quality thickness sander, so maybe a different experience from the low end stuff I have used.

[J.R. Rutter]

Other advice would be for ring porous wood like red oak. Go too fine with it, and push it a little, and you will get wavy grain for irregular sanding of the early and late grain. I've always been a fan of a stroke sander for furniture work. Not nearly the deep scratches from the grit like a thickness sander. I've never run a really high quality thickness sander, so maybe a different experience from the low end stuff I have used.

Good advice. A steel drum helps a lot with this, as well as knots.

[Jeff Duncan]

I have a single head machine and am pretty lazy about changing belts so do like some of the others and run almost everything through at the same grit. When something comes up where I need to grind a little extra or sand a little finer I'll take the time to swap, but for most things it's either 120 or 150 whichever I have on hand;) It's just easier to send a door though at 150 an extra pass or two than it is to change grits.....but again it's just me YMMV.

As far as depth I'm not trying to remove any significant amount of material, that's what my planer is for. If I do have to remove say 1/16" to flatten a glued up slab for say a c-top or similar, I'll throw a 60 grit belt on an grind it right down. Otherwise I'm just sanding enough to remove a heavy pencil mark or so per pass.

good luck,
JeffD

[Peter Quinn]

I should preface my comments by stating I'm not even vaguely an expert on widebelts, I use one a lot at work, counter tops, passage doors, panel glue ups, s4s, molding blanks headed for a shaper for edging , etc. What grit you use may depend on what you are sanding and what comes next. Mostly I use 60 grit for occasional grinding and leveling things too wide for the planer, 80 grit for rough sanding things too wide or too thin already to plane, but fairly close to level, 100 grit for paint grade, 120 for stain grade and anything with thin veneers. Paper thin I stay out of the wide belt. I don't see the wide belt as a finish ready machine even w/o cross grain scratches like on doors, things like doors and counter tops will get hand sanded anyway at 150-180 or 220. So my strategy is basic. Level surface, consistent fine scratches, done.

that said there was a good series of articles in woodshop news this winter, maybe a 3 part article, written by an actual widebelt expert that explained tune up procedures, grit selection relative to feed speed and desired depth of pass, and developed a series of practical sanding schedules for different operations. Definetly worth a read if you have access to the woodshop news archives.

[Charles Brown]

Peter, I think someone in my shop has the Woodshop News. I'll check with them.

I guess mainly what I'm interested in is not using the widebelt as a thickness sander, more so as a a tool in the finishing process. I'm not looking to remove inches of material. I'm interested in seeing what the progression people use to be the most efficient in removing the scratches left behind from the previous grits. Consensus seems to be, though, to just use one grit on multiple passes. Interesting way to approach it.

I've got a kitchen full of cherry doors and end panels coming up and I was just trying to strategize how to send all the parts through so all it will take is a little time with the ROS at 180 and 220 to be finished. Just trying to improve my work cycles.

It is such a simple exacting machine that I thought people may have a known sequence for each level of grits to be used. I usually try to stay in the 0.015" per pass with say a 120 grit belt, but if the scratches left behind are "0.020" deep then it's not the most efficient use of time and material.

JR, in the future I'll get a combo head. Right now all I have access to is a single oscillating 37" widebelt.

[Mike Wilkins]

Off the planer I have 100 grit, then 120 on my dual-drum sander. This gets it ready for joinery and then finish sanding w/random orbit sanders. I am mostly trying to get rid of planer marks. I never use my sander for a thicknesser; that is what the planer is for. Even as a serious amateur, I feel the grit change dance is just too much to go to lower, coarser grits to thickness a board.

[J.R. Rutter]

I've got a kitchen full of cherry doors and end panels coming up and I was just trying to strategize how to send all the parts through so all it will take is a little time with the ROS at 180 and 220 to be finished. Just trying to improve my work cycles.

It is such a simple exacting machine that I thought people may have a known sequence for each level of grits to be used. I usually try to stay in the 0.015" per pass with say a 120 grit belt, but if the scratches left behind are "0.020" deep then it's not the most efficient use of time and material.

JR, in the future I'll get a combo head. Right now all I have access to is a single oscillating 37" widebelt.

If you are going to ROS at 220, then I would go at least to a 220 pass to make life easier. Normally, I try to step back one grit level for ROS. So we use 180 on the hand sander and 220 final grit on the widebelt.

Here are some depth of scratch numbers that might be helpful to get in the ballpark - I took it from a reference that I have and retyped it. On a single head machine, keep careful track of the feed table height (part thickness) when changing between grits because the actual setting will change due to the finer grits being the equivalent of a thinner belt. For example, to go from 120 to 180, you may have to adjust the feed table up 1/8 turn of the hand wheel or so just to be able to hit the surface of a board on the second (fine grit) pass. If you keep track of how much you have to raise the table to erase the previous scratch pattern, then changing grits is faster and more consistent.

https://lh4.googleusercontent.com/-EdI1YNWLwoc/USvBW-KJ__I/AAAAAAAACYI/E4jnls6OmLY/s817/scratch+depth.png

[Mel Fulks]

Good public service anouncement ,J.R. Trying to get out cross grain scratches with the same grit on ROS is pretty slow.And I have noticed whenever there is an emergency sanding session with a bunch of people using a ROS to get doors into spray room ...all will be expressing their individuality in deciding what grit to use. Sanding needs a lot of managerial supervision.

[Jeff Duncan]

I agree that you ideally want to go at least to the finest grit your going to ROS if not one grit finer. Do you need to go to 220 for your doors? You may want to run a test panel if you haven't already, just to see what the difference between 180 grit and 220 grit will be. In my shop 150 is about the highest I go for raw wood sanding unless it was something really particular. I have on occasion thrown a 180 grit belt on to save a few minutes of sanding time, but that's as high as I've gone and it's a toss up as to whether I really save time vs just using the ROS.

good luck,
JeffD

[Kevin Jenness]

The table Jeff supplied is an interesting reference.You can see from it that a light pass is sufficient to erase scratches from the coarser belt at normal "finish sanding" grits. I would say that with good abrasives the scratch depth should be less than the stock removed. Lower quality belts may have a wider distribution of particle sizes that produce deeper scratches at a nominal grit designation. We run a Sandingmaster 36" single head with a nominal 18hp motor using 3M belts. We don't take more than .010" at 120# or .006-7" at 150#, and that is sufficient to remove any scratches from coarser belts. For glued up doors, assuming no tearout and the joinery is accurately indexed, one pass at 120# or 150#, then jump to 150# or 180# should do it. Some of us just run at 150# and hand sand from there. We can skip one grit level but not more.If you have a platen. use it for the final pass to lengthen the scratch pattern and reduce chatter and snake tracking from the oscillation. On our machine, the platen setting is rather subjective- too high and it is ineffective, too low and you run the risk of burning the belt and the work, and the risk increases as the grit #'s increase. We adjust it so it removes a pencil mark across the workpiece, and it feels warm but not hot to the touch as it comes out. Individual belts can vary depending on their manufacturing quality, age,and cleaning history. I find that removing cross grain scratches on the rails requires dropping back one grit level when random orbit sanding. In fact, if I can get a clean milling job and level joints I avoid the wide belt altogether. I don't use it for assembled face frames, but run the parts through the wide belt and concentrate on getting a flush joint that can be quickly tuned up with a scraper or ro sander. I don't look at the wide belt as a finish sander, but a leveller with adjustable aggressiveness and scratch depth. Sometimes the "timesaver" is not the widebelt but accurate milling and joinery.

I believe the Woodshop News articles referred to were by Howard Grivna, who has a book available on the subject of sander setup and maintenance.

[J.R. Rutter]

I believe the Woodshop News articles referred to were by Howard Grivna, who has a book available on the subject of sander setup and maintenance.

His book is where I got the data for the table.

[Charles Brown]

Jeff, you are correct that I probably don't need to go past 180 on the doors. On cherry I tend to one grit past what I deem to be necessary to minimize blotching, etc, on a natural finish. Where I used to work when applying darker stains we really didn't go past 150 on the doors.

I agree that the most time saved is in the proper milling of joinery, etc. Work cycles need to be efficient; even in a one-man shop. I enjoy my time spent working the wood but, and let's all be honest here, who really loves to sand? Anyone? Me neither.

The main goal was to try to outline a predictable sanding schedule to result in a consistent thickness. For example, if I want to end up at 13/16" thickness for my doors (0.8125") and I am to make three passes with consecutive grits (120, 150, 180) then (assuming only requiring one pass per side per grit) I should start with a board thickness of (0.8125" + (0.01*2) + (0.006*2) + (0.005*2) = 0.855") off the planer.

I know there are a lot of assumptions there but it is just a thought experiment. As stated above, your mileage may vary.

Why do I get the feeling that if these measurements were in metric the numbers would be even easier to remember?

[J.R. Rutter]

The main goal was to try to outline a predictable sanding schedule to result in a consistent thickness. For example, if I want to end up at 13/16" thickness for my doors (0.8125") and I am to make three passes with consecutive grits (120, 150, 180) then (assuming only requiring one pass per side per grit) I should start with a board thickness of (0.8125" + (0.01*2) + (0.006*2) + (0.005*2) = 0.855") off the planer.


That is exactly where my moulder and planer are set for door parts to hit 0.813" finished thickness. For me, 120 is perfect for leveling and glue removal (there isn't much of either to do) and 180 is a good finish grit. I wouldn't bother with 150 grit though. The sander can/will remove more material than the scratch depth. But if the final thickness isn't critical, then you are on the right track.

[Kevin Jenness]

I agree with J.R. Rutter. Skip the intermediate grit. I tend to mill about .030" thick and sand .015" off in two passes. Some spiteful woods need a greater margin and more passes through the sander.