Prefered woods for patterns?

Never thought of using sign board for flat patterns, I have quite a lot of it lying around so will give it a go. I’ve been thinking of casting an aluminium house number plaque and the sign board sound perfect

 

That’s another little job to add to the outstanding list that I need to find time to do.

 

I first started patternmaking in the 1960s working in the family foundry alongside my grandfather and several other patternmakers. My grandfather's medium was plaster (dang, we made a lot of bells and valve casings) but I used wood - primarily Jelutong. Now I use basswood in it's place. My grandfather scored a truckload of Philippine Mahogany at 10 cents on the dollar so I had to use that for a long time - hated it. Jelutong was light color and easy to see penciled knife marks. Fine grained, it was easy to apply finishes. Mahogany is heavy and dark, difficult to cut cross-grain with a chisel. It felt like I was being punished.
All of the pattermakers I worked with came from the war department companies that made parts for aircraft and ships. Companies like Ryan, Consolidated, Kettenberg, Kaisar, etc.. They were artisans and magicians when it came to woodworking and I genuinely love the techniques they taught me. They all retired before the foundry ended up closing. All gone now, they were good friends until they passed.
The Navy had their patternmakers school here where I live, they liked to use sugar pine.
Here's the secret the old patternmakers taught me for wood pattern finish: Shellac. not the prepared stuff, get shellac flakes and dissolve them in Denatured Alcohol. Brush or spray a few coats lightly sanding between - then apply pastewax and buff. your pattern will jump out of the sand.
I still have a far amount of Jelutong and GOBS of mahogany.. Probably never use it anymore. We had so much mahogany my dad used an 8/4 X 24" wide board as a ramp to his lawnmower shed The shed itself has mahogany studs.
I've been using a 3D printer to make patterns in the last few years - it has a place in the shop but it's not the final answer. It takes a lot of post-processing to fill all the lines and ridges but it does work. (I use automotive spotting putty thinned with lacquer thinner until it's like pancake batter)
ABS works best - PLA is printing with training wheels

 

I’ve recently been using basswood for the first time as an alternative to the pricey yellow cedar I love. The basswood is nice to use, for sure. Baltic birch plywood makes up a significant part of nearly every pattern I make.

Regardless of the species of wood, one technique I like is to harden and toughen the wood when it is near its final form by spreading a thin coat of cyano glue on it. The glue soaks in an then I spritz it with kicker. A few final licks with Si-C paper and it’s ready for a couple coats of sprayed shellac and a couple of glossy lacquer (Rustoleum Brand).

I’m going to try thinning my Bondo more as you suggest. It tends to be my default fillet material. But, I also use fine sanding sawdust and thin cyano as an instant filler for some little divot that shows up in the process. Put a little mound of dust on/in the divot, wick in the cyano, spritz with kicker and immediately sand. Saves 15 or more minutes waiting for Bondo to cure. The cyano also homogenized end grain of plywood and solid woods so it finishes better with less shellac and paint wicking.

Denis

 

Just curious, there's an exterior grade of mdf, that goes by the tradename extira, it's completely waterproof and quite a bit denser than the normal stuff. Has anyone here tried using that or a similar type of composite wood product for patterns?

 

Not Bondo. Use the Automotive Spotting Putty - it comes in a large toothpaste-style tube. It's lacquer based so adding a little thinner works great.

I've never tried thinning Bondo..

 

be careful with spotting putty. if you put it on too thick it likes to shrink. But it dries really fast so making a few thin layers doesn't add a bunch of time to the project.

 

Sounds like I’d better give it a try. Can’t have too many arrows in the quiver. Thanks.

Denis

 

I will admit that since I was lead to water putty here..... I use it as my go to filler. Even on 3d prints that will be painted for patterns. It takes a bit to dry (overnightish) but shapes so easy and smooth.

https://www.amazon.com/Donald-Durha...ocphy=9015485&hvtargid=pla-311840853498&psc=1

 

I use bondo thinned out with a little polyester resin as a filler. Believe or not, water putty of any type, Durham's or otherwise, is nearly impossible to find here in Canada.

 

https://www.amazon.ca/Donald-Durham...ty&qid=1620845509&sprefix=durh,aps,174&sr=8-1
Rocco it's quite a bit more expensive in Canada (Double! even after adjusting greenbacks for Loonies) . But Amazon will deliver it!

 

For that price, I'll stick with what I know for the time being, bondo. But, I'm only a 1/2 hour from New York state, maybe when things are back to "normal", I'll dust off my passport and make a border run.

 

I get by well with filling with water based wood putty. Thin it and it dries quickly, sands easily, and you never know it's there when you get paint all over it.

 

I always used Mahogony back when we used wood. It worked well enough for to be used for master patterns and never really had any issues with it. We have used several different fillers but have pretty much stuck with Tuffill going on 30 years now. I couldn't recommend anything different. Has always done a fabulous job for us. But speaking of master patterns I have some very... very old lead master patterns that we used. Some of them may go back into the early 1900's...maybe even further back. Most of them are damaged and bent and warped from being tossed into a scrap pile but I got them out to use the lead for fishing sinkers.......only way I think I could have gotten them out of there.LOL I will get them out of storage one day and try to repair them to their original glory. Some pretty cool really old stuff! Kettles and dutch ovens and griddles and such....not in any old catalogs that I have seen so must pre-date those.

 

Hey Billy, try not to let those old patterns get melted down for scrap. Vintage foundry patterns are considered "art pieces" by some, have you seen what they're getting for them on eBay? If you ever get a chance, go through those old lead patterns, pull out the cool looking ones and ones that are a little unusual or that every one would recognize.

 

Someone with the right skill set could probably make them nearly perfect...ahem...not sure who..ahem. They are master's thought..not patterns...double shrinkage lead castings that they would use to make a pattern. In the old days we required a master to come with new products patterns were built for. Easy way for me to find how old they are if I can find them in an old catalog. They are way before my time and I often worked with things built in early century. They may predate the catalog which would be bad as no proof as to what they actually are. I don't plan on selling them but to hang in my foundry as art.

 

For small repairs and fillets, I use a hot melt mix applied with a small soldering iron, almost a wax pen. The mix is 10 parts damar resin, 5 parts bee's wax, 1 part carnauba wax. The mix sets in seconds, doesn't chip, scrapes and sands well, takes extensive handling, and is compatible with platinum based silicones (in case copying the pattern comes into play). Swapping pine rosin for the damar has similar physical properties, but lacks the compatibility with silicones. Damar resin is used as an incense base and as a base for encaustic painting; it is the 'varnish' applied to oil paintings of the renaissance.

For quick patterns I sometimes use pawlonia wood; stable, sands to shape almost as quick as Ren board, but dents easily.

 

I bought some automotive spotting putty (Bondo brand by 3M) and I see what you mean. Easy to smoothly apply and sands great. Makes sense as that was its intended use. Thanks for the pointer.

Denis