Thread: Sanding a slab with grain is all directions

Carefully!! but you already know that

I'd carefully handsand following the main grain direction. you may find a curved sanding path helpful for that middle section.

I wouldn't use the palm sander and I'd start with say 180 grit minimum and take it carefully up through 180, 240, 320, up to 400.

Another method would be to scrape it.

cheers
Wendy

What kind of epoxy are you using? the usual is Casting and embedding resin which is like the stuff used for fibre glass. Its clear so if the hole is deep enough you can do the bug house thing. Personally I prefer it black so use a little builders oxide in the mix, but any colour is possible by mixing oxides. The surface though is a shiny plastic area in a lovely piece of wood, thin cracks are OK but larger pieces tend to annoy as time goes by. My next project I think Ill try to inlay rather than fill. Again if your finish is a polyurethane then that may not matter.

Using West System 105 (never mixed expoy before). I wanted the clear look and test patches are er ok - not great. Having a little problem with small bubbles to date but learning more about that as I go. Still better than a couple examples I've seen - so far but it's a finicky thing and won't say too much untill mine is done and correct.

And yes realise that it will have the shinny look where it is filled. Only 1 largist fill. Will be finishing in Cabots carbothane but no sure if it will be gloss or satin.

Sanding the multi-directional grain and the epoxy area is what's worring me as the epoxy is so hard. I doubt if I can sand successfully by hand. So far on test sections and the underside I have used the orbital with 120. This has been ok doing epoxy at 24 hours but i don't want to leave longer. I have noticed 1 little bit of scratches near some epoxy, hence the question in this thread.

Thanks

Cheers

Me, I've got powertools and ain't afraid to use 'em.

Personally I'd use a ROS all the way... Camphor is a pretty forgiving timber, even when knotty.

Between grits I'd be wiping down the surface with a tack cloth and "blowing out" the ROS and pads, to ensure any previous grit is removed. Paying particular care to the intersection of epoxy/timber, as this is where particles can get trapped, and cause scratches when you move to the next grit.

As you're aware, the epoxy won't cut back as fast as the timber and can end up sitting slightly proud after each grit. (Less and less so, as the grits become finer.) So, between grits with the ROS I'd use a straight-edge over the epoxy and sight through for high-spots. If the epoxy stands proud, then I'd lightly hand sand just that area with a block, using the last grit.

Once you're down to 400 grit - or wherever you want to stop at with the timber - it's a good idea to go a few more grits finer with the sanding block on just the epoxied areas... because you'll still see scratches there even when the timber looks OK. For a real "mirror finish" I've gone down as far as 12000 on epoxy in the past...

Skew, great advice.

Hit it with the duo Metabo (suitably dust extracted) and work through the grits. Never fails. Only problem will be the epoxy as Skew noted. I usually work out from there and return, just like if you want a hollow on the grinder.

Jeff

Thanks peole great stuff.

I have normally only gone to 600 or 800 in past. Going to that or finer won't case and adherence issues with epoxy when finishing with Carbothane?

Cheers

SB

try a bit of casting and embedding resin, I think you will get a better finish. You can get a small can from Bunnings but there is a nasty trick, you have to buy a bottle of hardning agent, so dont be caught as the language can be rough. This stuff is thin enough that I used a syringe with a large blunt needle to fill worm holes, it will sand and polish up to perfect if finished with wet and dry. So a piece of wood like that try it, you never know you might like a nice redback down the hole as a talking piece. If you do you put some resin in first then the bug and cover the lot.

West System is an excellent and well proven product but there are a couple of quirks in it use:

* It absolutely hates water. Think about running a heat gun lightly over surfaces before applying West.

* Moisten surfaces with epoxy thinners (MEK or similar) before applying WEST product. It aids penetration and minimises bubbles.

* Be extremely accurate in measuring resin and hardener. In one of their books WEST say you can be up to 3% out, which isn't much if you are mixing 50 mils.

* Use a clean cup and stirrer for every batch of epoxy. If you use a pre-used container the partly cured epoxy will affect the new batch, perhaps drastically changing its open time.

* Make sure all containers, etc are compatible with the epoxy. Foam cups will, and some other plastics also, will dissolve in epoxy thinner.

* Latex rubber gloves go tacky in solvent, PVC disposable gloves do not. Both are usually available on same shelf in supermarket, M10, B**, etc.

* Follow safety instructions. Many people slowly become sensitised to epoxy over time. I am developing a twitch in my eye when exposed to wet epoxy, a friend gets migraine and is disabled for 2-3 days. I wear two pairs of gloves, excellent ventilation, eye protection and mask - and I am very careful.

You have probably already discovered the above but....

In spite of the above I actually like the results of epoxy.

Cheers

Graeme

Camphor is very forgiving and easy to sand, if using a building finish ie laquer, polyU etc its pointless sanding higher than 180 with a ROS or 240 by hand. If finishing with oils, wax or shellac go as high as your patience allows.

If hole filling in camphor, West System dries very, very hard, and can be difficult to get a flush finish. Techniglue is not clear but is easy to sand, Rapid Cure is clear and is easy to sand but as the name suggests, you have to work quickly.

Believe it or not but filling holes with a black epoxy mix makes the holes just appear to be features, to many people this sounds just wrong, but it can make the flaws "disappear" and become part of the timber.

I would do the bulk of the work with a cabinet scraper or scraper plane if you have one but am not a big fan of filling voids with epoxy and such.
Like Maloof I like to cut wedges, blocks or whatever shape fits out of a piece of the same timber and glue them into the voids sometimes even hammer them into the voids. Some hand shaping is needed and the tiny voids cracks etc I fill with CA glue then ROS to whatever grade suits your proposed finish.
f voids go right through I prefer to remove the unstable material with carving tools and then sand the inside of the void and finish like the rest of the table.


Ross