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Using a sander in lieu of hand sanding?


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Whilst I do enjoy the process of hand sanding, it's quite time consuming and there's only a limited amount of time in the day. I recently used a square palm sander to get a experimental piece of 1084 steel up to a dull reflective finish. I'm not necessarily trying to get it to a mirror finish, but does anyone recommend using a square/orbital sander to take some work out of the hand sanding process?

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if it works thats fine, i think that getting out 80 grit and bigger scratches takes the most time especially with hand sanding, once the blade is flat and those big scratches are gone things go a lot quicker. 

 

my concern is with how flat the blade is after using an orbital or palm sander, if the blade has slight dips and waves from machine sanding then you go to hand sand to a higher grit it will be harder to get a good finish because you might not be able to sand the low spots without removing the high spots.

 

im not saying it wont work but it doesnt seem as precise as hand sanding with a hard flat backer or sanding with a belt grinder with a flat platten which is a hard flat backer. im not very familiar with orbital/square sanders but try to make sure the sandpaper has a hard backing for more accuracy, a softer backing could be used to blend stuff together but softer would also wash out grind lines that you might not want to.

 

and ill just add this, minimum polish for me is 400 grit, a finer polish can resist rusting better and 400 is pretty good for carbon steel.

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Back around 2008 or so there was a craze for using orbital sanders in the southeastern USA.  We all bought one and built mounts to clamp them upside down in a vise rather than using it on a clamped blade.  This helps, since instead of controlling the sander you control the blade.  Recommended practice even went so far as to glue a sheet of 3/8" thick 70-durometer neoprene to the platen and buy rolls of PSA paper. Lube with Windex.  

 

By 2010, none of us were still doing it.

 

Why?  It only gives the illusion of speeding up the process, plus it tends to round over sharp lines.  Those little swirly marks are a pain to remove if you want to polish to a true 400-grit satin, and the vibration numbs your hands.

 

The fastest way I have found, short of a full machine finish on a belt grinder or 9" disk grinder, is drawfiling with progressively finer files prior to hand sanding.  

 

Forge as flat as you can, descale by an overnight soak in vinegar (scale ruins files and dulls sandpaper fast), rough grind however you are set up to do it.  If you can't go up to 400 on a grinder, go as high as you can, then use a large (12" or more) bastard cut file to drawfile true flats. This should take five minutes of filing for a 4-8 inch blade. Then use a 6" bastard cut, a 6" 2nd cut, and a 6" smooth file.  As long as you pay attention and clean your files every few strokes to avoid pins in the teeth, in about half an hour's work you are ready to start hand-sanding at 220 grit.

 

All the above is for "ordinary" knives.  On things with large flats like cleavers, some swords, axes, armor, and so on that are too wide to drawfile or hand sand with a reasonably sized backer bar, a handheld orbital sander does make it a little easier to polish things up.  Pneumatic ones are better than electric for some reason.  I think they buzz faster.  

 

Basically, whatever works for you is great, as long as it gives you the results you want.  If you have the cash, a good 2x72 grinder and 9" disk grinder can really speed things up.  This includes a greatly increased speed of screwing up, of course.  If you have a well-equipped woodworking shop, don't overlook the 6 x 48" belt sanders.  The 4x36 sanders are for wood only.  If you have about $150 to spend, an angle grinder, some files, and good sandpaper will do everything the $5000 worth of grinders can do, and some things they can't.  

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There are makers who don't hand sand at all. If you do hollow grinds, they use a hard(around 80 duro) rubber wheel for grinding and a soft(around 30 duro) rubber wheel with trizac or equivalent belts for finishing. 

 

For flat grinds, they use a rotary platen with the same trizac belts. 

 

You will have to use either layout fluid or a large sharpie on the whole blade between grits because the scratches are very hard to spot without.

Edited by Joël Mercier
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I will chime in that I do not like the process or the results of a 1/4 sheet vibratory sander or my 5" random-orbit sander when used on metal. These are both meant for woodworking and in my experience I ended up fighting with them more than they helped.  My Dremel detail sander (a separate item, not a rotary tool attachment) and Foredom rotary sander attachment did more harm than good, leaving scratches and uneven spots that were really hard to work out.

 

The one bright spot from my woodworking shop was my 3 x 18 variable speed belt sander. I like to use it to clean up post heat-treat because you can get good metalwork belts in that size and the slow speed means I don't overheat the edge. But even with that, I only use it because my 2x72 is a fixed-speed model which is way too fast for fine sanding.

 

I also tried a Wen 1/2 x 18 variable-speed sander. These are intended for metalwork so there is a good selection of belts for them, and the belts are fairly cheap. It's not as easy to control as an actual file, and it's arguably not much faster, but it is easier on the arms than a traditional file and I do use this quite a bit. 

 

But Alan's constant assertions regarding files converted me a while back - good files are hard to beat.

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