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Turning a casting, how would you approach this?

Ukraine Train

Cast Iron
Joined
Feb 10, 2014
Location
Ohio
I'm looking at doing some secondary turning on these castings. I have an old jig that mounts in a chuck and the other side has an octagonal recess with set screws to hold the raw casting. So using this I have some options:
1) Turn larger face in the jig first then chuck on the 4.625" diameter to do the threads and 2.125" bore. The 1.502" bore needs to be done in the same op as the 4.625" diameter to maintain true position. My concern here is I'd be chucking on only 5/16" of stock for the second op.

Or:
2) Turn threaded side first then make a slug with female threads to chuck up and screw the parts into it to turn the other side. The concern with this method is the threads have a somewhat loose fit so I will have some runout between the threads and the 1.502" bore and 4.625" diameter.

I think I like option 1 better, just concerned about how short the step is for chucking for the second op. For the first op with option 1 I might be able to just chuck on the raw casting where the threads will go, depending on how straight and round it is there. Then I wouldn't have to use the jig we have for these.

cap.jpg
 
If I was only doing a few I add and operation. Come down and take a clean up cut on the face and OD on the threaded end. Grip that in soft jaws finish the backside including the max OD. Grip on max OD in soft jaws and thread?

Brent
 
I like your option 1 but simply chucking on the threads od with soft jaws should also be fine going the option 2 route, at 3" diameter and 8TPI 1"+ long, with suitable soft jaws you can grip that nice and hard with zero thread damage. But option one seams easiest, 5/16" is easily enough if you don't go stupid with speeds - feeds.

Im realy not a fan of screwing parts into fixtures and then machining them, it bever works well, parts move and can also be baster-eds to loosen! Much rather grip on big threads like that and take a extra 10 seconds cutting a bit more softly.
 
Is the 4 3/16" cast or machined? If you can leave it as cast then make some jaws that internally clamp that diameter and do everything in one chucking. You'd have to back bore one of the diameters.
 
You have VMC? I'd chuck up on the rough casting where the threads are and turn the back side. I'd then make a fixture for the mill and finish the second side complete, bore, thread mill and the bolt hole pattern. 2 ops and out the door.................................
 
Option 1 .....................if I had a lot to do I'd make up a dummy faceplate to take the 4.625 spigot and clamp it to that, rather than rely on soft jaws.

A thought, on op 2 if using soft jaws I would skim the face of the thread ed spigot and using a ''washer'' and the T/S to keep the 5/16 deep spigot pushed back in to the jaws and steady things while I did the heavy turning and screw cutting.

That said, I'm with David N, in this day and age that job is really in VMC country.
 
I'm looking at doing some secondary turning on these castings. I have an old jig that mounts in a chuck and the other side has an octagonal recess with set screws to hold the raw casting. So using this I have some options:
1) Turn larger face in the jig first then chuck on the 4.625" diameter to do the threads and 2.125" bore. The 1.502" bore needs to be done in the same op as the 4.625" diameter to maintain true position. My concern here is I'd be chucking on only 5/16" of stock for the second op.

Or:
2) Turn threaded side first then make a slug with female threads to chuck up and screw the parts into it to turn the other side. The concern with this method is the threads have a somewhat loose fit so I will have some runout between the threads and the 1.502" bore and 4.625" diameter.

I think I like option 1 better, just concerned about how short the step is for chucking for the second op. For the first op with option 1 I might be able to just chuck on the raw casting where the threads will go, depending on how straight and round it is there. Then I wouldn't have to use the jig we have for these.

View attachment 179527

Routinely did 11" od parts chucking on 1/4". I don't see a problem.
 
Some great ideas here; thanks guys. I do have a VMC and considered doing the threaded end there but between the 30° angle in the bore and the undercut curved profile behind the threads I felt like I'm getting into some 3D contouring territory and special tooling which will increase the time and cost. I will wait until I have castings on hand and see how straight/round the thread side is and then decide if I need to skim that part before chucking on it.

The 4 3/16" bore is as-cast; depending on the surface that might be a good option for chucking also.
 
I don’t see an undercut behind the thread. There actually should be a clearance but the designer resigned to it.

If the casting is solid, chuck it on the thread stub. Make a central bore, say 1¼", make the big side, the eight bores, too. Prepare a fixture with two bolts, secure part with nuts, and do thread and inside, back chamfer on the 1.502" inclusive. If everything must be machined (I doubt that), you can still clamp on the short 4⅝".
 








 
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