Order of Operations for Raw Castings

Shiseiji

Shiseiji

Avid destroyer of many materials.
H-M Lifetime Diamond Member
Joined
Sep 14, 2014
Messages
710
I want to state up front I don't know squat, and absolutely do not want to start an opinion war. This a serious question. If I could have found an answer on the two forums I searched I wouldn't ask. Also I'm post surgery single handed on a tablet so please excuse typos I don't catch.

When watching Quinn (Blonde Hacks of whome I am a minimum level Patron) machine a raw casting for a packing, she said right up front she was eye balling the setup and from my own error prone experience wasn't surprised when attaching the part it would only go on one way because the three holes didn't share a center line (hope that's close to the correct term). Learned several days later there had been some blow up over this and the same issue with Joe Pie's work. Honestly I don't care. I do want to learn how others might approach the set up so all three holes are centered. My thoughts follow, please shoot it full of holes as necessary and give your thoughts.
- Flatten the flange base using a vice
- flatten the top of the flange center.
- Get the average the width of the two flanges
- drill a small hole in the flange center
- use a screw to clamp down the flange using the small hole to a sacrificial plate and a couple of clamps to prevent spinning.
- Establish the center line, flatten and drill the screw bosses
- use the screw bosses to clamp down the flange
- remove the center screw and drill/ream to size.
 
You know, sometimes it's easier to use a DRO, gauge pin or super glue.
You are comparing two of my favorite channels but they approach things from two different angles.
I too, don't know squat.
Sounds to me like you have it worked out. It's only a model, complete this one, next time you may do it differently.
 
Usually, if I want to find out if a pattern is on center, I will use a compass, whether laying out or verifying. It's basic geometric construction.
 
Janderso said:
You know, sometimes it's easier to use a DRO, gauge pin or super glue.

Sounds to me like you have it worked out. It's only a model, complete this one, next time you may do it differently.
Click to expand...
Thanks. I like Quinn just a little more only because her tooling is closer to my reality. I have yet to succeed with super glue so tend to try other options. My mill is a Clausing 8511, factory BP M-head, and the DRO is still in the box :rolleyes: but this would be a great reason to get it mounted and start to figure the thing out. Would you put the gauge pin through the hole into a plate?
 
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pontiac428 said:
Usually, if I want to find out if a pattern is on center, I will use a compass, whether laying out or verifying. It's basic geometric construction.
Click to expand...
Meaning eyeball the center using a center line and the arcs? My #1 weakness in this hobby is that in a family with 3 engineers and a college CNC instructor, I'm the one who gutted his way, with tutoring, through every math class I had, was happy with a "C", and close to zero retention. But I've wow'ed West Point grads with my spread sheets, so I no longer have much shame over it, just ask and be done with it.
 
I too am making this kit.

For the small packing gland I used my belt sander to flatten the bottom then glued it to some round ally stock like Quinn.

I managed to get the boss machined round, to height and centre drilled and was then able to move the whole thing including the ally to my mill and drill the holes there. I centred the piece using the hole with a drill in the chuck. I then used a combination of a pin then a spot drill to align it by eye so all 3 holes ended up being in line with the Y axis, then drilled it. This turned out very accurately. Finally I held the piece in a collet chuck in my lathe and machined the back side to thickness.

However I couldn't get superglue to hold the larger packing gland on the lathe.

I even drilled and tapped a piece of round scrap and tried screwing the part onto this but it still spun, even with glue. I think that the part was too large to be held on the small surface area available to the glue.

I then made up the pressure fixture that Joe made to hold the piece using a rotating centre. But I simply couldn't get enough pressure for some reason to hold the part solid.

Each time it slipped I had to recentre it with a gauge. Very frustrating. With care and very light cuts I managed to get the boss to size but it ended up about 10 thou off centre and I simply couldn't get it to stay in place to machine the surface of the ears.

So then I made up a fixture plate like Joe Pi used. Drilled and tapped a matrix of 1/4 20tpi holes in a piece of 5/16 plate steel (7 by 3 holes, 0.75" apart) and made 3 finger clamps similar to the ones he made although cruder. Worked brilliantly. Because I had got the boss off centre it looks a little odd but I drilled the 2 screw holes in line with the boss and just filed the outer profile a bit and it looks OK.

I have just finished the conrod using the same plate. Made it incredible easy.

My advice would be to copy the plate Joe has. You'll use it again.
 
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I'll probably never get around to watching the videos (my video to-watch backlog just keeps growing), but can you guys let me know which ones you're referring to so I can at least understand what model/project is being undertaken?
 
Thank you Andrew. Only at the very end when Joe Pi has the flange screwed down does it appear one hole isn't centered. But with the way he indexed the part, I suspect the part will fit either way.
 
I watched them both and Joe Pi's method is more along how I would approach machining the part. You could also not use the casting and remake the part from bar stock. This would pretty much guarantee the three holes are on same center line and equal distant from the center. It would require filing the part to the correct profile.
 
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