Homemade indexing head

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OddDuck
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Homemade indexing head

Post by OddDuck » Sat Mar 28, 2020 6:48 pm

All you real machinists, if you must laugh, please do so quietly, to avoid injuring my tender feelings...
https://youtu.be/GVvhMj_9sy8
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

RSG
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Re: Homemade indexing head

Post by RSG » Sun Mar 29, 2020 7:59 am

Looks good so far!
Vision is not seeing things as they are, but as they will be.

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SteveM
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Re: Homemade indexing head

Post by SteveM » Sun Mar 29, 2020 4:00 pm

Nice casting.

Steve

Harold_V
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Re: Homemade indexing head

Post by Harold_V » Sun Mar 29, 2020 4:04 pm

My only comment would be a fly cutter (finish) pass on the base would yield a nicer finish surface. Not critical, obviously.

Looking good thus far, but I wish you'd address the casting procedure. As most folks know, pouring gray iron isn't easy with a crucible furnace. Would you please address your procedure? Also, some mention of the condition of the casting. Was it easy to machine? The rather shiny appearance leads me to think the iron may be low in carbon, and slightly chilled. To be expected when melting in a crucible furnace, and can be addressed by ferrosilicon addition. Did you have to do that?

Well done!

H
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OddDuck
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Re: Homemade indexing head

Post by OddDuck » Sun Mar 29, 2020 8:38 pm

Thanks Everyone. Harold, I did try a fly cutter, unfortunately my tool grinding skills and the lack of oompf in my mill's ability to turn it made it not very effective. I did use the largest diameter cutter I could, got decent results with that. It seemed to mill fine, black powdery chips and not much if any squealing, when I broke off the gating it was a nice uniform grey on the cross section, with very little to no "skin" of hardness. The shiny parts are probably a result of cleaning it up a bit with a flap disk. It was greensand cast, and I was lucky it filled completely. I will admit I am not the world's expert on cast iron, biggest tips I can give are use decent scrap, with no steel embedded. Run the furnace atmosphere neutral to slightly rich, if you run lean, you run the risk of burning off carbon from the melt. I did add ferrosilicon, about a tablespoon for the melt and I added it about a minute before casting.
The next step is fixturing it to the faceplate so I can drill and bore or ream it. It's not shown on the video, but I milled one of the legs flat and square and I am just going to use a riser block to fixture it to the faceplate, to give clearance on the back end of the bore.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

Harold_V
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Re: Homemade indexing head

Post by Harold_V » Mon Mar 30, 2020 1:56 am

When I refined precious metals, I melted pure copper on several occasions, to cast ingots (it was used to recover silver from solution). The melting point of copper is well below the melting point of gray iron. I can only imagine what your experience was like.
Thanks for your comments.

H
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OddDuck
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Re: Homemade indexing head

Post by OddDuck » Mon Mar 30, 2020 8:41 am

Hot. It was very hot. Nah, with proper PPE it's not too much worse than casting bronze. Melts only a couple hundred degrees higher than the pouring temp for bronze, and it's maybe 2600 or so at pouring temp. I actually poured this one on the cool side, I didn't think I got a full pour. But it surprised me, in a good way.
It is very hard on the furnace and crucible, though. Most backyard furnaces aren't built with a high enough rated refractory to stand up to repeated iron melts. My hotface is rated ( at least it's what it said on the bag) at 3500, and the refractory I backed it with was 3000. If you want to do iron I would think that the minimum rating for your furnace lining should be 3000. All temps in farenheight, by the way.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

OddDuck
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Re: Homemade indexing head

Post by OddDuck » Sun Apr 05, 2020 6:24 pm

https://youtu.be/4PkVn64m_Oo
Now for some headscratchery to figure out my next step....
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

whateg0
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Re: Homemade indexing head

Post by whateg0 » Mon Apr 06, 2020 1:23 am

At that RPM, it's probably ok, but that's a lot of mass hanging out leveraging against those two bolts. As they say, though, ya gotta do what ya gotta do!

Dave

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Re: Homemade indexing head

Post by Harold_V » Mon Apr 06, 2020 3:59 am

Hmmm.
I didn't read or see anything that suggests you intend to bore the indexing head. Drilling should be simply to create an undersized hole, so you can bore for proper location and size. Your chance of drilling (and even reaming) and getting the desired results, even if you didn't have the void, would not be good. That isn't good practice.

Amazing hollow area, something I didn't expect. Any idea why it formed?

H
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SteveM
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Re: Homemade indexing head

Post by SteveM » Mon Apr 06, 2020 7:26 am

You located the part on the faceplate on the back of the head. You checked the hole relative to the base. There could be error between the back and the base.

It would have been better to have the part held by the base on the faceplate using an angle.

Then, as Harold says, drill undersize and bore with a single-point tool.

Also, if your tailstock is misaligned, you can end up with a tapered bore, particularly with a reamer, because it will orbit as it cuts. Boring with the carriage only depends on whether the ways are parallel to the spindle centerline.

Steve

OddDuck
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Re: Homemade indexing head

Post by OddDuck » Mon Apr 06, 2020 9:10 am

Thanks for the suggestions, guys. The hole is parallel to the long side, and about 1/8" of a difference along the hole in reference to the base. So, I think the tailstock is okay. My logic behind the setup was that the pressure of the drill would keep the leg pressed against the center. I think that the void was the problem, I couldn't drill a pilot, and the larger drill deflected when it got to the void.
It drilled nicely, no hard spots. So, boring it is a possibility. Harold, I think when I cast it, that the outer "skin" froze first, and the void is a shrink of some type.
I would love to mount it to an angle plate, but I don't have enough swing on my lathe, and that would make counterbalancing even more problematic.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

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