Drilling and Pinning Tall Molds

I make a lot of molds that are hinged. I remove 1/4 inch of material leaving a 1/4" tall, by 1/2" wide radius boss at one end along with pockets
for the mating bosses on the other half of the mold. I found that it was slower to use a 2.5D process with an endmill to do that than to use a round over mill, but I get a very accurate repeatable result, and do not have to account for the lead angles on a round over mill and waste part of the remaining mold surface for a big clearance slot. Anyway, its automated and it works really well so I can be doing other things while its machining.
After all the primary work is done I drill and pin the hinge bosses along with my other secondary work. Alignement pins, clamping screws, extra hardware installation, etc.
When I first start I made some drill jigs out of aluminum with a clamping screw to hold it in place. It worked, but I had to be sure I clamped the same side on both the top and bottom of the mold, and if the thickness of the molds varied much so did the center alignment of the hinge pin. They were all made as double jigs. Use one side for top and the other side for bottom. It worked, but it had its issues.
I was always looking for a faster easier way. I played with the idea of setting up the little mill drill with a self centering vise and after finding center just clamping down the ways and leaving it there with a work stop for the molds. After much research I found most self centering vises that were priced in my budget just weren't up to the task. They would get you close, but not to my desired tolerance.
I resigned myself to clamping the mold in a vise, indicating off of it, and then drilling (Hurco or Tormach) or spiral milling (Speedmaster) the hinge pin holes. The little X4 Speedmaster mostly only gets used for engraving my trademark and the occasional custom engraving work for a customer so it was always available for that. Spiral interpolate the clearance size, then spiral interpolate from there to full depth for the press fit. Its faster to spot and drill on the Tormach or the Hurco, but the Hurco is down and the Tormach has been very busy lately.
Well a couple weeks ago I finished two hinged custom molds for a customer that are 17 inches tall. I also cut a test mold to experiment with. I'm glad I did. My first that was to just scribe and drill on the drill press. Nope. I set a 12x12x12 right angle plate on my surface plate, and clamped the mold to it. I right a cylinder square to make sure it was straight, but I could feel the dril press flexing a little when I was drilling. Anyway, the cumulative errors other than that were not good. That test mold works, but you have to use the handles to pry it open and pry it closed. Between flex, drill wander, scribing accuracy, and who knows what all else it just doesn't swing open and closed easily enough. Add on that the mold has mating "spacers with a close fit (.0005-.001 clearance) and everything has to line up pretty well.
The molds have been sitting on my assembly bench for a couple weeks while other molds get finished and shipped.
This morning I had a weird sort of idea. Mount it to the right angle plate, and mount the right angle plate to a face plate on the 14x40 lathe. I'd either have to remove the bed gap or clip two corners on the right angle plate, but the lathe is pretty rigid and it will drill straight (enough) if I center or spot drill to start the hole. The problem is aligning the lathe to the work pieces. Twice for each mold. I have no idea how I would indicate that in.
Then I had a better idea. Make drill guides. Not one like my old ones that clamps to the outside of the mold, but one that is an exact fit to the hinge boss itself and clamps to the face of the mold. The hinge bosses are pretty consistent. They vary by lot less than half the clearance of the hinge pin clearance hole. If I make the guide deep enough I could even hand drill the pins at that point. I'll have to make two of them, but so what. Its automated. LOL.
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******** I suppose I should clarify that none of my mills has enough Z axis clearance to spot and drill these mold hinges. The Tormach is close, but not after I install a tool holder. Even in a spindle collet, I'd have to make custom extra short drills. The Hurco came up a couple inches short even with the knee cranked all the way down. ********
"Bob La Londe" wrote in message
I make a lot of molds that are hinged. I remove 1/4 inch of material leaving a 1/4" tall, by 1/2" wide 1/2" radius boss at one end along with pockets for the mating bosses on the other half of the mold. I found that it was slower to use a 2.5D process with an endmill to do that than to use a round over mill, but I get a very accurate repeatable result, and do not have to account for the lead angles on a round over mill and waste part of the remaining mold surface for a big clearance slot. Anyway, its automated and it works really well so I can be doing other things while its machining.
After all the primary work is done I drill and pin the hinge bosses along with my other secondary work. Alignement pins, clamping screws, extra hardware installation, etc.
When I first start I made some drill jigs out of aluminum with a clamping screw to hold it in place. It worked, but I had to be sure I clamped the same side on both the top and bottom of the mold, and if the thickness of the molds varied much so did the center alignment of the hinge pin. They were all made as double jigs. Use one side for top and the other side for bottom. It worked, but it had its issues.
I was always looking for a faster easier way. I played with the idea of setting up the little mill drill with a self centering vise and after finding center just clamping down the ways and leaving it there with a work stop for the molds. After much research I found most self centering vises that were priced in my budget just weren't up to the task. They would get you close, but not to my desired tolerance.
I resigned myself to clamping the mold in a vise, indicating off of it, and then drilling (Hurco or Tormach) or spiral milling (Speedmaster) the hinge pin holes. The little X4 Speedmaster mostly only gets used for engraving my trademark and the occasional custom engraving work for a customer so it was always available for that. Spiral interpolate the clearance size, then spiral interpolate from there to full depth for the press fit. Its faster to spot and drill on the Tormach or the Hurco, but the Hurco is down and the Tormach has been very busy lately.
Well a couple weeks ago I finished two hinged custom molds for a customer that are 17 inches tall. I also cut a test mold to experiment with. I'm glad I did. My first that was to just scribe and drill on the drill press. Nope. I set a 12x12x12 right angle plate on my surface plate, and clamped the mold to it. I right a cylinder square to make sure it was straight, but I could feel the dril press flexing a little when I was drilling. Anyway, the cumulative errors other than that were not good. That test mold works, but you have to use the handles to pry it open and pry it closed. Between flex, drill wander, scribing accuracy, and who knows what all else it just doesn't swing open and closed easily enough. Add on that the mold has mating "spacers with a close fit (.0005-.001 clearance) and everything has to line up pretty well.
The molds have been sitting on my assembly bench for a couple weeks while other molds get finished and shipped.
This morning I had a weird sort of idea. Mount it to the right angle plate, and mount the right angle plate to a face plate on the 14x40 lathe. I'd either have to remove the bed gap or clip two corners on the right angle plate, but the lathe is pretty rigid and it will drill straight (enough) if I center or spot drill to start the hole. The problem is aligning the lathe to the work pieces. Twice for each mold. I have no idea how I would indicate that in.
Then I had a better idea. Make drill guides. Not one like my old ones that clamps to the outside of the mold, but one that is an exact fit to the hinge boss itself and clamps to the face of the mold. The hinge bosses are pretty consistent. They vary by lot less than half the clearance of the hinge pin clearance hole. If I make the guide deep enough I could even hand drill the pins at that point. I'll have to make two of them, but so what. Its automated. LOL.
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I have not cast metal since jr high shop in 1965.
But I have been watching MYFORDBOY on youtube. He is some old brit that never says a word, but casts Aluminum the way we were trying to do it in jr high.
Fun to watch.
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On 11/5/2018 2:56 PM, clark wrote:

didn't get to pour , or even watch , just made the mold and Teacher poured after school . Now I have my own foundry setup , and have cast al and brass . Currently working on a forge furnace so I can beat on some steel . Check out castinghobby on yahoogroups ...
--
Snag
Yes , I'm old
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"Terry Coombs" wrote in message
On 11/5/2018 2:56 PM, clark wrote:

That would be about the same time I got my first taste ... but we didn't get to pour , or even watch , just made the mold and Teacher poured after school . Now I have my own foundry setup , and have cast al and brass . Currently working on a forge furnace so I can beat on some steel . Check out castinghobby on yahoogroups ...
***************************
Thanks guys. I typically make casting molds for lead, pewter, etc, and injection molds for plastics. I may at some point if I have the time make some "permanent" molds out of steel for aluminum, but I'm pretty busy with what I am doing right now. Maybe I should raise my rates a little to cut down my work load. LOL. I used to do that every year or two as a contractor.
Anyway, aluminum casting and backyard metal beating are on my to do for fun list. I just haven't had the time. I have accumulated a decent stock pile of firebrick, refractory coating, and refractory cement along with other miscellaneous materials to build foundry and forge furnaces. (two separate furnaces) I think my next fun project to be added to the fun list though is to weld a top on my anvil (yes I still haven't done it) and put it on a nice extra heavy steel stand. I'm still beating on a scrap piece of 1" plate laying on my work bench when I need to shape something or to curve something by throwing it in the sand outside and mashing on it with a ballpein.
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