Rebooting the 'micarta' production line

[oafpatroll]

@Tripodmvr has been posting pics of Ausie knives with micarta type scales and that inspired me to break my two day streak of Christmas present book reading to make some again. I've been meaning to do so for quite a while as I have two knives that are long overdue some new scales and two handguns that I would like to make grips for. Fabric based micarta is really useful stuff in that it can be made at home and is very durable, inert (depending on the resin you use), flexible, impact resistant and grippy as hell wet or dry. I made a fair bit of the stuff years ago for knife scales and for a friend who used it for building drones when they were still more of a fringe uber geek thing than they are now.

Having not kept record of my resin/fabric mix ratios or work time I decided to do a recalibration run with stuff I had on hand so as to avoid wasting money. Used a really manky pair of khaki cotton canvas work pants and some leftover polyester tooling resin for the material and 16mm clad chipboard offcuts for a press.

I'd forgotten how much resin cotton fabric absorbs even when it's threadbare and paint stained like this stuff was so I had to mix a second batch post haste to finish the layup as the first lot was starting to gel.

Worked lekker though and the first block will be used to re-scale a chopper knife I made out of a roller bearing nearly 20 years ago. It's as ugly as hell and has paint inclusions and oil stains and all sorts but it's rock solid and completely homogeneous. I'll make up some more this weekend using alternating layers of virgin khaki and olive drab cotton canvas for aesthetics and use those on the second knife and the two handguns.

The white colouring in the pics aren't dry spots but paint and bleach stains in the fabric. I thinned the resin a touch with acetone after catalysing and consolidated with a roller so it was completely saturated.

A tip for anyone who may like to try this is that baking paper is the thing to use as a mold release rather than wax paper. It's completely counter intuitive but matte baking paper almost jumps off the mold and the slab while slick slippery wax paper needs to be laboriously peeled off. That's one thing I'm dead glad to have remembered. 









 

       

[oafpatroll]

Pic of the slab attach for those who can't see onedrive pictures

[oafpatroll]

Pic of the slab attach for those who can't see onedrive pictures

[oafpatroll]

Something I forgot was that if you want absolutely parallel faces on a slab you need seriously rigid plates to clamp against. I thought that a layer of 16mm chipboard with 20mm of pine on top of that would do but the slab was more than 1mm high in the middle of its 200mm length. The stuff I made for my mate with the drones was made in a press consisting of two 16mm mild steel plates with 8 bolts around 6mm thick steel spacers. With that I just piled in the layers and then cranked down on the bolts and the slab was a perfectly uniform 6mm across its usable area. With this janky chipboard press I will need to add clamps in the middle and measure a bit more carefully but given what I intend using them for that should be fine. 

[oafpatroll]

Made a few more slabs with virgin fabric. First one that I got out of the mold and ground an edge on and wet sanded to 320 grit is this black bull denim. I like it a lot and will be using it to make a set of grips for a stainless Ruger revolver. I have fine hessian and a khaki cotton canvas/duck still in the molds. looking forward to how they come out. Will be having a crack at some much finer fabrics in the linen range as well as craft paper next. Paper has the advantage of piling up in thin and perfectly aligned layers that don't deform when clamped.

[Treeman]

Interesting stuff this ! What would happen if you put something like a dagga leaf or feather or R100 note as the top most layer ? Would it be as imagined ?

[Ds J]

And would you please give us a photo of the polished blue stuff? It looks good.

[oafpatroll]

Interesting stuff this ! What would happen if you put something like a dagga leaf or feather or R100 note as the top most layer ? Would it be as imagined ?

As long as whatever you put in is permeable to or completely encapsulated by resin it should work fine.

[oafpatroll]

And would you please give us a photo of the polished blue stuff? It looks good.

Unless you coat it with clear resin or varnish this stuff doesn't polish to a bright surface as the bulk of the block is fabric. It doesn't really seem to change much after 320 grit. Since I want it for the grippiness it imparts I won't be coating or polishing the grips or scales I make from it.

[oafpatroll]

And would you please give us a photo of the polished blue stuff? It looks good.

Unless you coat it with clear resin or varnish this stuff doesn't polish to a bright surface as the bulk of the block is fabric. It doesn't really seem to change much after 320 grit. Since I want it for the grippinessnit imparts I won't be coating or polishing the grips or scales I make from it.

While what I've made doesn't polish well in it's raw stae it does absorb oil which chnges its appearance a bit. This is the black denim with some thinned boiled linnseed on the 320 grit cut edge.

[oafpatroll]

Pulled the hessian this morning and it looks a lot like . . . . . hessian. Be interesting to see what the cut edge looks like. Expect that this will make for the grippiest of the sample so far so I may use it on the frankenchopper rescale as that wouold benefit most from more grip.

[Tripodmvr]

Patiently waiting to see the final product as fitted. Do you need some medium to contain the resin or can it be used as is and colored with some stain or powder?

[oafpatroll]

Patiently waiting to see the final product as fitted. Do you need some medium to contain the resin or can it be used as is and colored with some stain or powder?

I'm going to do a bit more prototyping and testing with cheap leftover polyester resin I have before making the blocks I'll use for my nice knife and the two handguns with good quality epoxy resin so it will be a little while before I have anything  final to show. Given my near non-existent woodworking skills I'm far from confident of the outcome, especially of the revolver grips as working the stuff is a fair bit like working dense hard wood.

I know you get casting resins that are strong on their own but I've never tried anything like that and have no idea if it would be strong enough on its own for use as a scale or pistol grip. My gut feel is that it wouldn't be but I don't know that for sure. I understand that the properties of the micarta (especially the compressive and tensile strength) come from the combination of the material in the composite so leaving out the fabric would probably lose you something. As to the staining I once tried an alcohol based black stain in some polyester resin and it worked well. 

[Tripodmvr]

Thanks. Something totally new to me and although the name "micarta" is known to me I have never queried the source of the product. Will do some browsing to catch up.

[oafpatroll]

Thanks. Something totally new to me and although the name "micarta" is known to me I have never queried the source of the product. Will do some browsing to catch up.

Pleasure. 'Micarta' is actually the trade name of a phenolic resin based composite that was developed pre-ww1 by Westinghouse. It was a thermoset composite of phenolic and paper or fabric and was cured in serious presses. It was originally used in industrial electrical applications and apparently also for some decorative stuff.

The term now is used in much the same was as 'damascus' is as a generic term for pattern welded steels. The few bits of the real vintage stuff I've seen is very smooth and has barely a hint of the fabric patterning.