Need help with flattening (bolsters, scales, etc.)

P

P J 234

Well-Known Member
After many tries using as many different tools and methods I can think of and have available to me, I'm at a real frustration point with trying to get things flat. This includes bolster materials (stainless bar stock, etc.), wood handle scales, etc., etc. The tools I have tried are belt grinder on a flat platen, cheap small fast disc grinder on my Craftsman belt/disc combo, palm sander with hard plate mounted upside down in a bench vise, and by hand with sandpaper on a flat surface.

I occasionally have success, but I often end up with results that I'm not happy with and there doesn't seem to be any rhyme or reason to it as far as I can tell. Sometimes things may get a relatively flat surface from my efforts, but they are not of uniform thickness afterwards. Sometimes things end up bowed either high in the center (convex) or low in the center (concave.) I just can't seem to come up with the right methods to get this right and I'm not even sure what I'm doing wrong in order to correct it.

The latest example of this is after cutting a wood block into scales on my DeWalt portaband (not a perfectly clean, straight cut), I tried evening and flattening them on the belt against the platen. I don't know when it happened, but I ended up with a bowed surface that's high in the middle and low at the edges. If I hold the sanded surfaces of the scales together and squeeze them at the edges on one side, they roll together at that edge and away from each other at the opposite side. I've tried sanding it by hand, and also tried on my palm sander to get it flat, but it still looks exactly the same after my efforts.

If anyone has any tips for getting things good and flat that are easily shared over the internet, I'd be very grateful for the help. Thanks in advance for any assistance!
 
Someone is going to come along and suggest a disc grinder but I have no experience of one so can't comment on that directly, even though I know that it the power tool way to go.

I flatten my scales by hand using a slab of granite that has wet 'n' dry well stuck down.

Start of by colouring the entire side in with a pencil. Take a stroke on the wet 'n' dry. See what dissappears to give you an idea of the work you need to do.

Only sand in one direction. The change of direction if sanding back and forth will give you the rounded surface.

When you think you're done, colour the scale in again.

Take one slow and steady stroke.

Have you done it right? Is there some graphite left at the edges?

Flattening is a very important step. If you do it wrong, you fluff the whole knife.
 
PJ, if you need a flat granite slab check out a countertop shop in your area. I went to one and they had a dumpster full of cut-offs and broken pieces. All for free. Places that make tombstones are another place to look.
 
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I use a driil press attachment called the Luthiers Friend.A thickness sander.It does a very good job with handle scales and Ive used it to flatten copper and brass. It sells for $159.00 I also replaced the drum that came with it,for a sleevless drum,I can use any grit of paper I need with the drum.Its well worth $$$.
Ive attatched a couple of pics of mine.
I think I got it at stewmac.com or woodcraft sell them also.[/ATTACH]
 
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That is some of the best information probably that you will read. I will add this as it works for me. Don't attempt to sand down past 120 before going to the granite block or thick piece of glass or other very flat surface. If you grind with say a 60 grit and 120 that should be enough. Use only new or near new belts to do this !!! It is also a lot easier to grind a retanglular shape piece than say a sort of triangular one and keep it even. Check often with vernier caliper how the work is going. Finger placement for where the pressure will be is very important. Get one side down to the 120 then use that to judge and measure thickness from for the other side. It does take time and lots of practice to be real good at it. There are lots of makers that do this well enough to not need surface grinders when making folders. Try some scrap wood and metal first if possible. If you are doing straight knives you might get a strong magnet to hold on to your piece. When you go to the hand sanding bend back masking tape in the shape of a "T" and stick this on the piece for a handle. I hope this helps you. It does work for me and a few others I passed these tips on to. Frank
 
One thing I was told years ago, and works for me is when sanding on the granite block, make figure 8 motions not circular or back and forth.

The tape handle Frank mentioned sounds very simple but ROCKS when trying to hold a small scale piece on a fast moving abrasive belt! Save lots of fingertips and knuckles!!

Trial and error is my best teacher. Using a pencil to color your surface is also a very good idea, I know I changed a lot of my techniqes once I started doing this.

Good Luck and God Bless
Mike
 
D. Brodess, I sure like that !!! I may have to try a put together of my own, or afterwards purchase one. I have some sanding drums that go up to about 4". What diameter is that one you have, please ? Thanks. Frank
 
I am going to attempt an answer for your question. There are a lot things that influence getting a flat surface when sanding. Hardness of material, direction of sanding, pressure applied when sanding, the belts ability to cut.
I did woodworking most of my life before I got hurt. I used to pride myself on being able to take a 4x24 belt sander and a saw and create pretty much any kind of a piece of furniture, cabinet or such. When I first started with a 4x24 I hated it. I could grind a dip or gouge into a piece before I knew what was happening. The real secret is practice, practice, practice, and knowing your machine and what it is capable of!
When rough grinding a flat surface on the platen of a belt grinder I often turn the piece somewhat cross wise. I know I just heard a bunch of cringes! :eek:

Don't be afraid of this putting in cross the grain sanding marks because before you lift the piece from the belt you will rotate it back to sanding with the grain. The action of rotating the piece momentarily will help to knock down the high spots and bring it the piece back to a flat state. Now I don't recommend this too much as you drop down in grit and always before lifting the piece come back to sanding with the grain momentarily to knock out the cross grain marks.
I also will lift the piece from the belt and rotate around end for end while sanding and sand it that way for a while. You are still going with the grain and this helps to lessen the problems associated with off handed pressure you may be applying or the belt being duller on one side than the other.
When getting down to a final finish and you want to a flat grind use a fresh belt. The less pressure you have to apply to a belt the flatter the grind!
Also when trying to grind a flat surface stop and check often.
If you have a dip mark that area with a sharpie and stay off of it till you can bring down the surrounding areas. Coating metal with Dycon will let you know right quick how flat a grind you are getting. Remember the eye is somewhat forgiving when seeing flat but a straight edge takes away the eyes ability to overlook a dip in a flat grind. When looking for a flat grind stop and check the surface with a straight edge when in doubt and do it often to identify any trouble spots.
 
Paul,

Unless your actually attempting to surface grind something don't worry about it being an even thickness. Especially for scales or bolsters where your going to be shaping, grinding, sanding, finishing, polishing, and re-polishing the side opposite from the flat your trying to get.

As for getting things flat.... it's a PITA for us all lol. But even attempting to hand sand a true flat begining with a convex surface is just asking for trouble. Even once you get a flat started a little pressure in the wrong direction and you back to being convex.

Try this out for your scales. Draw a straight line down the length on the edge. Then grind down to the line as good as possible with the scale going across the belt. It wont be flat but it wont be convex either. Now hand sand on some 60 or 100 grit paper.

Most likely you'll be starting with the lowest spot in the middle of the scale so what happens is as soon as you begin hand sanding you'll create a flat on the top and bottom edge of the scale. Now as you sand things will keep getting better and better till the low spots are gone and you've got a true flat.

Another tip is to flatten the scales before cutting them to shape at all. Typically the low areas always seem to be on the edges of the scale. Now position the tang in 1/4" or so from all the edges of the "flatened" scale. Doing it this way just leaves some sacrificial material on the edges of the handle material and you will end up with a true flat.

Now I use the beveled disk grinder to get a concave surface running the length of the scale. It's on a vary small scale but still concave. Generally a minute or two of hand sanding gives a true flat. I don't have a surface plate so I've been using the table on the drill press. No gaps so they must be getting flat enough.

Hope this helps, Josh
 
Frank Niro.
That is a 2"x3" drum.I cut my own handle slabs and it does a good job of flattening the scales.But I still hand sand .I use the table on my band saw with a big sheet of sand paper to touch it up!
Dan
 
Practice and patience help on the belt sander, but hand sanding using a granite surface plate works well.
 
Some times the platen that comes with a belt sander, for example a Ryobi I have, is not completely flat. I added a thin(3/32") plate of stainless steeel to mine with JB Weld. It really helps.

But I findI do most of the sanding by hand, with wet/dry on a 3/4" thick piece of plastic.
 
When ever you are cutting scales from blocks of wood you should get them close and then let it rest for a few days before attempting to get it completely flat because wood will almost always move a little after being cut and the internal tension takes time to release. Moisture also plays a part.
 
Wow, thanks for all the awesome tips and advice everyone! I think it sounds like practice (and patience, which isn't always in large supply with me!) are the big things but some of these little tips I will put to use right away. I do have a flat surface for hand sanding, but no real disc and as much as I'd like to have one, it's not going to be in the cards for me for a while. The tape handle on the wood scale is a great idea, as I have trouble with that and I couldn't figure out how to make it stick to a magnet ;) The Luthier's Friend looks interesting, but I could probably almost cobble together a disc or similar money. If it were only half that price...

Thanks again for everyone's input and advice, it will (hopefully) help me get this figured out!
 
Don't over complicate it until you're down with the basics.

Have you heard the phrase 'all the gear and no idea'? It's easy to get a machine for everything...
 
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