Author Topic: Dummying up a guard to use as a casting template (Read 1896 times)

rich pierce · « **on:** February 04, 2019, 11:57:56 PM »

I’m working on another Fainot build and no guard available is quite close to the one pictured. I’m modifying another guard to send out to use as a template for sand casting. I want to beef it up in a couple areas, widen it a little, etc.

What can I glom on there to accomplish this? Bondo? I’ve got some. Would that stick well enough? Just want to build it up some here and there then finalize the shape.

Brooksie? What would Mikey do?

msellers · « **Reply #1 on:** February 05, 2019, 12:06:55 AM »

Bondo works for thinks you wouldn't even imagine. Have a skinning knife that I used bondo and a bread bag to make a smooth suface and ergonomically fit my hand for working kides. Has held up well, but also haven't dropped it. I was worried about it being so thick, but since there isn't flex and vibration I guess the 1/4 thickness mentioned on the can doesn't matter.
I would say rough the surafce up and give it a go. Can't do anymore yhan need to be scrubbed in acid if you aren't happy with it. Just my gut feeling on it.
Mike

Eric Kettenburg · « **Reply #2 on:** February 05, 2019, 12:10:13 AM »

I've used bondo exactly for this purpose a lot. Just make sure the surface to which you want it to adhere is roughed up a good bit - will hold up just fine for pattern making.

Mike Brooks · « **Reply #3 on:** February 05, 2019, 12:17:41 AM »

I took a trigger guard I bondo'd up down to the foundry last Friday. Works great.

45-110 · « **Reply #4 on:** February 05, 2019, 03:06:30 AM »

when i was casting way back and needed extra on the pattern for shrinkage, wrapping tape around some of the areas worked well. bondo will work fine too. just leave plenty of draft so you can get it out of the sand.
kw

Ron Scott · « **Reply #5 on:** February 05, 2019, 05:25:50 PM »

Keep in mind you will have perhaps as much as 10% shrinkage to all dimensions, of which the length will be the most visible. you might be better off to carve a master that is 10% oversize.

Randall Steffy · « **Reply #6 on:** February 05, 2019, 08:21:59 PM »

Actually, the shrinkage factor for brass is 3/16" per foot or 1.5%. So it is a significant amount in the length of a TG.

Bill Raby · « **Reply #7 on:** February 05, 2019, 08:30:01 PM »

I have done quite a lot of casting. It is not going to shrink any noticeable amount. If you cobble something together with bondo the foundry with have to make a mold of it first. At least if it is investment cast. If you carve one from casting wax the foundry can work with that directly and you save a few dollars on the mold.

Jim Kibler · « **Reply #8 on:** February 05, 2019, 09:14:58 PM »

I'm sure he is refering to sand casting. Yes, there will be shrinkage. Depending on the size of the original guard and the desired outcome, building up may be a good thing. Length shrinkage can ge an issue as well. When Wallace Gusler was making copies of mounts on some of his guns, he used the following process if I remember correctly:

Wrap original with tape to build up a considerable amount
Cast part.
Stretch metal with hammer to add length. In this case it would be double the shrinkage rate.
Cast part
File to shape.

This would then become the master pattern for casting additional parts.

Jim

Eric Kettenburg · « **Reply #9 on:** February 05, 2019, 11:16:24 PM »

I think you guys are way overthinking the shrinkage issue in regard to sand casting. I can't speak to more precise investment casting procedures but I have run a LOT of my own castings in both green sand and petrobond in small runs out of a small crucible, and using either wooden patterns or existing furniture as a pattern, I've never noticed any appreciable shrinkage or size change once it's all filed-out and cleaned up. You can always very slightly tap or wiggle the pattern in each half of the flask if you want to create add a hair of mass one way or another (carefully!) but honestly I've really never found the need to worry about any of this. Since I've been farming the patterns out, once again, the only difference I notice is the commercially cast parts are certainly nicer than my own castings! Finer sand, looks like.

Edit: I do want to stress that I DO understand that there is a variable percentage of shrinkage, I'm not trying to defy the laws of whatever and claim it doesn't exist. What I am saying is that unless you are casting precise parts to fit precise pre-existing inletting or something like that, I have never found it to be a problem in an individually-stocked piece and I've not seen any blatantly noticeable degeneration of form. Now maybe if you went multiple generations down the line - castings of castings of castings etc. - well that would be a different story.

120RIR · « **Reply #10 on:** February 06, 2019, 12:06:43 AM »

Not to change the subject from Mr. Kettenburg's contribution, but instead of Bondo you might want to give an epoxy putty called POR-15 a try. I've been using it for many years in the restoration of a small WWI artillery piece. It's a stiff putty (2-part), a lot cleaner than Bondo, and hardens like rock and then some.

Mike Brooks · « **Reply #11 on:** February 06, 2019, 12:54:40 AM »

I've been having a lot of sand casting done lately. I'm seeing something near 1/16" or less shrinkage on buttplates and trigger guards.

Metalshaper · « **Reply #12 on:** February 06, 2019, 05:41:21 PM »

if your into youtube, look up myfordboy! He has a lot of vids on casting and such. mainly aluminum but easily translates into brass I would think??

Respect Always
Metalshaper/Jonathan

45-110 · « **Reply #13 on:** February 06, 2019, 08:23:58 PM »

you want a oversize pattern not only for shrinkage but for cleanup. sand castings need more cleanup than investment cast. also thin sections of your part (ie. guard tang etc.) need the pattern thickened so the metal flows and fully fills out.

Clint · « **Reply #14 on:** February 14, 2019, 03:04:45 AM »

Rich,
You could easily get some casting wax and dip the old fitting a if you were making candles. stop when you have enough buildup and in the end remove the wax with hot water. I have rammed wax into sand molds and they wear out after a few runs. Clint

Marcruger · « **Reply #15 on:** February 14, 2019, 05:04:11 AM »

Eric's triggerguard pattern at the Colonial Williamsburg shop is beautifully carved from wood. Maybe walnut or rosewood it appeared. The pattern in and of itself is art. So we know some are made from wood as a start. God Bless, Marc

M. E. Pering · « **Reply #16 on:** February 14, 2019, 05:42:28 AM »

I am getting closer to casting my own brass, and have been doing a few experiments with pattern making. I have been playing with polymer clay of the brand name Sculpey. Once you have the model made in this clay, you bake it in a kitchen oven and it becomes quite hard. I did try Bondo too, but you have a limited work time with it, though shrinkage doesn't appear to be much of an issue. The Sculpey clay does shrink a bit during the bake. But with the polymer clay, it stays workable until baked.

Now I am not modifying a current design, but making my own from scratch, but I believe it would work in this case too. I imagine the metal would get to temperature faster, and thus by the time the clay was curing, the metal would be expanded as much as it is going to. while the clay is still soft. I am currently planning on sand casting, but until I get a larger burn-out kiln, I will have to hold off on investment casting, though this would be my preferred method.

Matt

rich pierce · « **Reply #17 on:** February 14, 2019, 06:56:54 AM »

I’ve got one master made from wood and another just getting beefed up a bit. Bondo was so-so in adherence so went for filled JB Weld build up. I’m good to go soon as I final polish.

Mike Brooks · « **Reply #18 on:** February 14, 2019, 05:19:41 PM »

I just made an early English trade gun trigger guard master. Bought what was available from TOTW that was suitable with modifications. I cut it up, modified it here and there soldered and riveted it all together, slathered on the bondo, filed it how I needed it to be and now it's at the foundry.

Next project will be making a master to cast the box for Oerter's Griffin gun. Maybe the four piece early Dickert box after that. So many projects , so little time.

45-110 · « **Reply #19 on:** February 14, 2019, 11:04:46 PM »

for Mike Brooks
Could you reveal what foundry you work with? Appears that they do small custom orders and will work with ones own patterns.
thanks
kw

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Author Topic: Dummying up a guard to use as a casting template (Read 1896 times)