As the title says I have an interesting problem to solve.  I need to remove the remains of the sprues on the feet and then drill two of them for locating and retention pins.  I have four of each size to do.

This is what I'm up against:








These are my mom's creations:  Trophies for The Irish Water Spaniel Club Specialty.  They will be mounted to walnut bases.  


Though she has done these kinds of things in the past, but with many fewer needed and time is becoming an issue.  In the past the sprues were cut shorter (sometimes affecting the feet) and hand work was all that was required.  They still will need hand work to finish the final shaping, but to remove the bulk of the sprues and give four feet on the ground, a mill is the way I want to proceed.



Now for the curious on how these are created I will post that in my next post.

Hand held, all four feet at once with a belt grinder is how I'd do it.

How my mom started and got to this point as far as casting these (among many others).  These are lost wax castings, but the actual start has a bit more to the story.

With the large dogs (she is currently working on an even larger one) clay was used to sculpt the basic dog and fur, but leaving room for modification.  From the clay, a silicone mold was made into which wax can be cast.  From there, she uses a heated waxer tool (like clay working tools) to finish each with it's own personality.  She had even removed heads in order to change the direction the dog is looking.  Once the creations are to her liking, the wax forms are sent to one of two casters (the really small ones go to one---jewelry size, while the larger go to a second).  

The casters then attach wax sprues and vents and make a tree of the things.  Once treed, the assembly is dipped in investment (a heat resistant plaster like stuff) in multiple layers.  Once dry, the investment tree mold is placed in a kiln to first melt most of the wax for recovery, then heated to a higher temperature to burn out the remaining residue.  This also pre-heats the mold.  Bronze is then pored into the main sprue and the workers make sure that all the vents fill as well.  This assembly is then left to cool slowly.

Once cool, the investment is broken away, the sprues cut, and the final parts are cleaned, usually finished by bead blasting.   Even after cleaning, my mom still has to pick away at bits of remaining investment.  

There is a lot of detail work to clean up the imperfections where the investment did not quite fill, or cracked and left flashing. Her Foredom rotary tool now becomes essential and has paid for itself and its replacement flex shafts a few times over.  Once the detail work is done, then she lightly "buffs" the pieces with fine maroon ScotchBrite wheels on her old Craftsman benchtop buffer/grinder.

The final patina, to get the dark color of the Irish Water Spaniel coat, she uses liver of sulfur, and again lightly buffs to bring out highlights.


BTW, she will be 90 next summer.

The closest thing to that is her Harbor Freight belt sander/disc sander combo.  We've done it that way in the past but it can get the feet a bit too hot, and would take quite a while to remove that much material.   A band saw would make quick removal of the bulk, but holding the pieces well enough without damaging the coat would likewise be tricky.

Get a ceramic belt.

Fractal vise and thin copper strips?

That's the thing I was trying to think of, a Fractal vise. Those things are cool AF.

Pot them upside down in plaster.

We used to surface grind the bases of castings used for prism optics.  Because of their shape they and could not be clamped and even if we could have it would have flexed the casting enough to cause problems with tolerances.

We built some 3/8" plate steel u-shaped pots and sealed the ends with duct tape.  We then inverted the casting so the "feet" were facing up, poured plaster into the molds and let it set.

After it hardened we machined them,  unpotted them from the steel form and then just soaked the plaster block in water until it got soft enough to break out the castings with some light hammer taps.

I’d do the hand held but with a right angle die grinder and the appropriate roloc pads.

I have had the thought of making a hydraulic version of the fractal vise before.  Imagine a whole bunch of closely spaced pin/pistons in which three on each vise jaw can be adjusted first and then locked in place.  This would establish two planes but not provide enough surface area for clamping. The remaining pins would then be driven by connected hydraulics to apply even pressure points throughout the part's surface.

Damn OP, your mom did those?  By herself?!?  Your mom is badass.

Mines just a trucker with a bad knees and a bad back.

Freeze in water?

Cerocast - or whatever it is called for taking chamber molds.

Belt sander. Probably 30 seconds to awesome.

Agreed, a good Norton NorZon zirconium belt will take that off in short order with minimal heat.

That was my first thought.  They probably can't be gripped well enough to be milled very nicely.

Off the wall idea- ice? Prop them up in a dish, fill with water, freeze.  Grip ice cube in vise, mill delicately?

And, she'll be 90 next summer.  The only help comes from me, my brother, and the foundries.  My brother does a bit of the grunt wood work, though my mom used to be quite capable of using her table saw, and chop saw.  Routers to do the edge detail has been a bit above her comfort level.  I, on the other hand, do the more precision stuff like locating holes in the wood bases to match the tapped holes in the mating casting for mounting.  She, however, dictates where and how the figure is supposed to line-up and fit the base, and its relationship to other things that might be on it as well.  There are often displays that tell stories about the event with her trophies.

Cerrrosafe (which I have a couple of pounds), along with the traditional Wood's metal for fixturing, I think, might tend to amalgamate with the bronze.  The tin in the bronze would likely combine with the tin in those alloys.  I did consider this as an option initially, but I do not want to risk damaging the artwork.

I was hoping that someone had a similar solution with some other low melting point stuff that would not stick to metal, have a minimal shrink, and be rigid enough to hold up to being clamped in a vise.  The plaster idea is of that sort, but knowing how difficult it is to get all the investment out of the coat detail, makes it slightly less than ideal.  However, a short soak in vinegar would remove any remaining plaster, though it does not seem to work as well on the investment.

Getting a new ceramic belt for the belt sander, does seem like a good option at this time.  I'll see if I can find one locally tomorrow while I'm in town.

Unless the mill vice is below freezing you would be dealing with a shrinking block of ice with a lubricant (liquid water) continuously regenerating. That's a recipe for disaster.

What they said...  This is not a complicated project.  Drill pin hole in feet.  Put the pin in the hole in the base with some epoxy.  Done.

I did a fair amount of sprue removal from bronzes in college

we used a v block and a jewelers hand saw

lazy students burned thru cut off wheels on the fordhams

Oh my god.  We might have to engage our brains!

Why is the foundry not providing the service of delivering a finalized product to your moms specification?

If mom is not making enough profit to pay for production costs, then she needs to reevaluate her final price to the customer.

Cheap seats stock take off is a harbor freight belt sander
mounted upside down in a vice with a speed control foot switch

https://www.harborfreight.com/7-amp-3-in-x-21-in-variable-speed-belt-sander-56916.html

better:
https://www.harborfreight.com/4-inch-x-36-inch-belt-6-inch-disc-sander-97181.html

a small bandsaw with a pine deck plate would safely clip the longer spruing
https://www.harborfreight.com/13-hp-9-in-benchtop-band-saw-60500.html

But for a dozen bronze dogs with 4 feet,
a nice German jewelers saw with a pack of fresh blades is going to do a perfect job in an hour

https://pmcsupplies.com/8-german-sawframe.html

Iunderstoodthatreference.jpg

for that i would band saw close , belt sand and hand drill the holes

if you realy want to use a mill then make a fixture with faxemility compound and mount it to the vice jaws

My first thought is to chisel relief into the wood base the sculptures will be mounted on.

It strikes me as a far simpler solution.

Edit: After looking at the photos a second time, I see that my solution would only work on a few off the examples, but not all.

These are, and have been done for quite some time.  A good belt on the belt sander did the majority of the work.  Locating the foot peg holes did require a bit of finesse with some wood blocks, careful drilling and tapping.  Brass screws glued into both the foot and the wood  or bronze base holds quite well. There were some details that had to be done with the Foredom flex shaft tool to clean up mold defects, and stuff.  Bead blasting afterward hid any tool marks, and helped remove any remaining investment.