oakhilltop said:
I'm working on a project using white pine with knots. Hand planing is a challenge with the knots and grain variations around the knots. I have a ETS 125 sander and tried using that to flatten some boards (1" x 6") that are slightly cupped etc. But it takes awhile with 80 grit and don't have lower grits in the shop at the moment. I watched a few videos on using a belt sander and thought, hmmmm that could work well. It seems like the large flat surface of a belt sander could get the boards very close to the final surface. Once I get the panels glued up, I will have a fair amount of sanding to smooth them further.
I'm interested in thoughts about the pros and cons of a 4" x 24" belt sander (looking at the Makita) and the festool sanders. The belt sander would be easier on the wallet.
I may very well be missing something here, but I simply don't see any reason whatsoever to be flattening individual planks prior to glue-up into panels. Why? Especially, why use sanders for this task? This is more the province of the surface planer, or jointer in new-world parlance. Flatten one face only: the concave one. Again, why would it be necessary? It just seems a waste of time & effort. Why not flatten the whole panel post-glue-up?
It's not at all unusual for planks to cup. When making panels from these, it's traditional to alternate the concavities across the face of the glue-up, to provide an overall (roughly) flat planar panel surface. This also compensates for the fact that board edges are no longer at exact right angles to the faces.
Traditional cabinet makers would've flattened the panel's diagonals @ 45 degrees with a Jack or even a scrub plane if it's in particularly bad shape before a final smoothing parallel to the grain. Cranky grain & knots would've been carefully treated with scrapers.
I've had great results with using belt sanders for both roughing out the diagonals and final smoothing too. I simply don't understand the hate , nor the tales of woe from their use. A carefully, properly used belter won't produce ridges & valleys. In my youth, I've sanded entire floors, even walls & ceilings, with belt sanders. Both new & old. A similar technique to hand planes is used. First the diagonals with coarse grit (24-36-40G if hardwood, maybe 40-60 for softer woods), then progressively smoother grits once levelled along the grain (60-80-120-240G/80-240 hard/softwood). Obviously, the rougher the surface, the coarser the grit required. For renovating or removing deteriorated timber finishes, maybe start with 120G or so.
Belt sanders are simply THE tool for panel flattening. It's what they were specifically designed for, & precisely what they're best at. The only tool better, faster & more accurate is the dedicated stationary thicknessing sander.
For what it's worth, bigger, more powerful sanders are obviously much faster, but also tend to be a bit more of a handful. But their weight & power works well to accomplish the task without undue effort. However, for anything other than horizontal surfaces, esp vertical wall panelling or overhead, belters are terrible, & should be avoided at all costs. My current fave is the lovely big 1400w Holz-Her/Festool sander with it's integrated frame. Sufficient power to accomplish herculean tasks yet with a delicacy & finesse of touch to achieve the finest of nuanced surfacing too.
Sub-framed sanders from Germany & Switzerland can be surprisingly delicate with a sufficiently light, even & gentle touch to smooth veneers in finer grits. Not that I'd recommend you try this. Yet for the actual act of flattening wide panels, floors, walls etc there's no other sander available (as far as I'm aware) that capable of flattening (depending on grit & sub-frame) either as rapidly or as accurately either.
For what it's worth, I've owned belt sanders from Bosch/Scintilla, Metabo/Holz-Her, Elu/Perles, Festool/Holz-Her & used others from Hitachi-Koki & Makita, principalliy in 75 x 533 & 100 x 610 sizes. The smaller sizes are a great all-rounder, with the size & power ideal for most cabinet & panel work, paint-stripping etc. whereas the latter is a big, powerful & heavy beast of a tool, well-capable of tackling all but the very largest of tasks.
PS. I wouldn't recommend using ANY hand-held belt sander for any but the smallest of floor refinishing tasks. Just hire the proper tool for the weekend instead.
PPS. A regularly applied offcut of stiff PVC water pipe to a running belt sander's front roller will keep the abrasive grit relatively clog-free and extend belt-life many times over!
