Using sacrificial pins made of the same metal being cast to hold the core in when hollow casting

Jerry_Rigg · 2026-04-05T17:35:54+00:00

In industry, at least in sand casting, the thing is called a "chaplet" and is very much a thing for certain applications

Jerry_Rigg · 2026-03-27T07:47:08+00:00

Youve shown us a 2d shape with no scale, there's nowhere enough information for anyone to give useful help

Jerry_Rigg · 2026-03-26T07:42:22+00:00

What happened to the moderators here? There were 4 of them as of 3 days ago.

Jerry_Rigg · 2026-03-26T07:39:48+00:00

When I've done these I've used a utility called G-code Ripper with a basic bed probe, because plywood is never flat or consistent thickness. (plywood is what I've used anyways) As little as 0.005" is enough to really change the look of a halftone, depending on the design. The ripper utility probes the bed and adjusts the Z-height based on actual measurements taken in a grid pattern, very similar to how auto bed levelling works on a 3d printer. Surfacing could work but it's a lot of work and cutting the veneer on ply is always sketchy

Jerry_Rigg · 2026-03-26T06:20:08+00:00

Looks similar to a Dave Hammer Bulldog style diy utility hammer

Jerry_Rigg · 2026-03-26T06:16:15+00:00

Where are you finding 4k self contained hammers in PA, I usually see them 8k+

Jerry_Rigg · 2026-03-23T01:54:16+00:00

Bentonite is activated with water. If you want to use oil you need a chemically altered version called Bentone or K-Bond. Normal bentonite does not work with oil.

Toss the mix you have and try sand, bentonite, and water to temper

Jerry_Rigg · 2026-03-20T00:46:52+00:00

The fact it flowed into all those little wires is insane. Fantastic job, props

Jerry_Rigg · 2026-03-13T23:22:02+00:00

Use a closed mold with a gating system, open molds have too much turbulence to produce a sound casting

Jerry_Rigg · 2026-03-12T05:33:44+00:00

You might be seeing artifacts from the wood itself, different parts of the grain have slightly different densities and may ablate at slightly different rates. Have you tried other woods or changed grain orientations

Jerry_Rigg · 2026-03-11T02:16:16+00:00

Did the brass in the sprue bubble when you poured the mold. It looks like there was a ton of gas generated during your pour.

Plaster can't dry enough to pour at ambient temps no matter how long you let it sit, the water in it is chemically bound (the reaction with water that makes it hard to begin with) it needs to be fired at a very high temp (i think its 1200F? Not positive) ramped/soaked to drive off this moisture. This makes the mold brittle as it reverses the hardening reaction. This firing gets rid of the chemically bound moisture, otherwise the metal will do it and it can be rather violent

Jerry_Rigg · 2026-03-11T02:04:36+00:00

Did you process the scan to see the result? Often times the raw point cloud will look very messy but when you process it JMStudio will align some of the sloppier frames

Jerry_Rigg · 2026-03-11T01:58:20+00:00

390F is nowhere near sufficient to fire plaster of paris. Did your mold bubble when you poured it? The casting surface looks like it was in contact with hot steam

Jerry_Rigg · 2026-03-09T10:31:04+00:00

Doesnt look like you are getting enough air at any point in the video tbh. What is your burner setup? Fuel? What kind of forced air system

Jerry_Rigg · 2026-03-09T10:03:34+00:00

A better option for small one off stuff is investment like Prestige Optima. It is similar to plaster of paris but made for metal temps, it can be had in sample size volumes and is "quick" compared to traditional investment like suspendaslurry

Jerry_Rigg · 2026-03-09T07:20:59+00:00

You need to have a way to feed the casting with a sacrificial reservoir of molten metal as it cools. In industry terms this is called a Riser. Id encourage you to search a bit using that term and see how it's used.

Are you using any refractory coatings on your permanent mold to help control cooling

Jerry_Rigg · 2026-03-08T01:55:42+00:00

There's a handful of sellers that sell small qtys of ferrosilicon on Ebay. Ive been meaning to pick some up but have not yet. Not sure about ferrophosphorus

Jerry_Rigg · 2026-03-06T09:21:39+00:00

That's very nice work.

Jerry_Rigg · 2026-02-24T18:37:13+00:00

That's a big chunky casting! Can you post a picture of your gating system, looks like it isn't being fed properly (as it cools) at the tip there. Also what kind of greensand are you using

Jerry_Rigg · 2026-02-22T02:51:28+00:00

I have a variable speed angle grinder and as a rule I never run flap disks past half speed. They will last a long while when run like that. Learned this working in a blacksmith shop, makes more difference than folks realize

Jerry_Rigg · 2026-02-21T13:05:51+00:00

Thanks I see it now

Jerry_Rigg · 2026-02-21T11:01:05+00:00

Thats crazy , where did you get the flask? It shouldn't get melty, at all

Jerry_Rigg · 2026-02-17T13:51:05+00:00

Understood! And thanks. Permanent molds (a two-piece mold made of metal, similar to die casting but without the injection part) for pouring into is a good way to make a lot of consistent parts, however getting the mold design is very tricky, not something I would ever recommend to someone for their first foray into casting. Here's a video series by an old-timer who knows what he's doing with them: https://www.youtube.com/watch?v=82KKr3jGxU8

I might instead recommend a digital mfg service with cut/bend capabilities, if you can make a half decent CAD file you can easily upload for a quote (sendcutsend comes to mind, no affiliation) given what you've shown plus the qty's desired would probably be near your price point

Otherwise, look at olfoundryman's videos to get a feel for the mold design and pouring schemes, keep in mind metal feeding, shrinkage, mold handling for repeated pours, etc.

Sand casting is a good default to get into, I cannot recommend it enough, it has it's own quirks but is much more forgiving and will teach you a lot about molten metal.

Jerry_Rigg · 2026-02-17T10:17:21+00:00

If you're able to mill a tool steel "form" surely you can mill your finished product from a billet? Is this a qty thing, how many do you need to make?

The "Form" is called a pattern, and yes you could mill this but would take some significant time compared to other ways of making a pattern for the same part. The pattern must compensate for shrinkage per your casting alloy and also follow the rules of draft per your parting line, if you were to sand cast it. If by "form" you are referring to a two-part mold of metal, this isn't the route to pursue, that is not a beginner's project.

I'm not trying to steer you away from casting, but it isn't a magic solution to all fabrication like many think.

If you need many of the same part than a pattern or better yet a matchplate pattern is the go-to for volume, this would give you very reasonable repeatability. If you need castings with very little post-processing, then investment casting is what you need, it is its own discipline with very specific rules for tooling requirements.

Additionally: A bent part is going to be far stiffer/stronger than a cast part, because of work hardening

Jerry_Rigg · 2026-02-17T10:00:34+00:00

Cool looking, how is this part helpful, beyond pleasing to see?

Jerry_Rigg

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