Re: Train of Thought- Sanding resin flash, or: avoiding bloody finger tips.


Pierre <pierre.oliver@...>
 

Doc,
Entertaining read.
As I've said in clinics on building resin kits, the best way to get good at sanding resin castings is to do a string of stock cars. It'll either cure you or kill you.:-)
What I do which helps relieve the tedium and speeds up the process is to use coarser sand paper. 80 or 120 grit. The 80 is reserved for those cases where the flash is very thick. One needs to be very careful about how much material one is removing, but with a little diligence the job can be done fairly quickly. I've yet to sand through a casting.
Which reminds me, it's time to glue more sand paper to plexi for sanding resin. The old sheets are worn out.
Pierre Oliver

--- In STMFC@..., Denny Anspach <danspach@...> wrote:

Friends, I am once again engaging in my usual summer push-on-the-porch to build at least several fine kits, some really challenging, and others merely enjoyable. I have no grand plan or scheme, but simply choose those projects that catch my fancy and interest.

One of my current projects is a thoroughly delightful Westerfield Milwaukee Road 36' drop-door stock car kit, and as one might expect, the exquisite flat sides with their myriads of slats and fine bracing are all laid out in high relief on a relatively thick tough slab of resin. Now, the entire project depends upon cleaning out all flash between these fine slats and braces without collateral damage, the produced spaces to be squarely and smoothly cleared. In this regard, all know what to do: sand the backs of these sides until the flash between the slats becomes so thin that it can be easily cleaned out with the hosts of various sharp instruments that are right at hand (none of which really fit, or do the job!).

So the sanding of these large pieces begin: a segment of 220 grit wet-or-dry sandpaper is laid out flat; the side is placed on its back; and with fingers spread-eagled the length and width of the slide, the side is moved back and forth with sufficient pressure to engage the cutting sand paper granules, but not enough to grab the sandpaper and bunch it up with the creases that will only cause future problems.

Well, after a considerable length of time (I count to 100 slowly, with about three swipes per count per bout of sanding), I take a look and- I find that the flash is indeed minutely being removed, but primarily only under the tips of my "light" fingers. I change the position of my fingers, but I do not get very far because the sand paper is now loading up. I wash the sandpaper with a drop of detergent, dry it on a tea towel, and then get back to sanding. I rotate the side; I try to flatten my finger tips; I change my finger positions; I load up again; I wash again, and so on. Finally, I detect that the the bloom is off the rose on this once-fresh sandpaper (resin must be harder than I would imagine), and new sand paper is called for.

Now, I steal the small broiler pan out of the toaster over, fill it with detergent water, submerge the sandpaper, and commence sanding again, this time underwater. Things move faster (the paper is now self cleaning), and at least an elapsed 1/2 hour each after starting, finally the sides are becoming thin enough so that the flash between the slats and braces is thin enough to attack with my sharp sticks. However, at the same time, the sides are also becoming thin enough to become somewhat delicate to the handling that is still necessary.

But wait! The much thinned flash must still be removed so that the slats and braces have clean sharp edges, both in fact and in perception. This is undertaken with my principal sharp stick: a #11 Xacto blade whose point has been specially honed on an Arkansas stone, and whose "square" backside has also been flat-sharpened- i.e. the 90ยบ corners are also made as sharp as possible so that with only only the slightest tip, the backside will cut -actually scrape- just about as well as the knife edge on the other side. With this wonder tool, and a variety of stiff brushes, pokers, etc. and about an expended time of @hour, at last the exquisite, now fully-fenestrated sides are ready for their ends to be mitered to fit the car ends (also mitered).

I write this all up so that I can learn from others how THEY handle this relatively common but time consuming and tedious situation. My finger prints have probably been erased from my fingers during previous bouts of such resin flash sanding with much smaller pieces, the skin of the fingers being freshly sanded -bloody even- along with the target resin part.

I will say that demanding kits like this make me realize once again what a fulfilling delightful hobby this is!

Denny










H-mmm.
Denny S. Anspach, MD
Okoboji, Iowa

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