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Old 02-01-2020, 11:47 AM
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Bubba Bubba is offline
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Default Let's make some CNMG insert holders.

I had a stick of A2 7/8" steel. As it comes in it's not hard but hard enough for
a 14X40 Chinese lathe with BXA holders. I was looking into the right geometry
of the insert holders and seem they have a 5 Deg. down slope and 7 Deg.
relief. So I needed sort of a compound setup. It was a bit weak but I took
small cuts so nothing was moving through the ops.
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Old 02-01-2020, 11:56 AM
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I set the rotary table to 0, and moved 5 Deg. left/right to make the 80 Deg.
point with a 5 Deg. offset from the edge of the holder. Once the basic shape
was done I just marked the insert shape on the top. Just by eye and the marking,
made the pocket with a small cutout on the back. I used a .200 pin
in the chuck to mark the holding screw position.
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Old 02-01-2020, 11:57 AM
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Looking good! I want to make some more for work myself. I could go to the boss and he probably would buy them, cheaper in the long run vs paying work, but my frugal gene wants me to make them in slow time, just to say I can.

Your set up has given me some ideas on how I can do it with the tools I have available to me. Didn't think about the rotary table. I don't have a rotary table, but have an indexer. maybe I can use that. I like getting tools out that no one in the shop has used in 10-15 years and learn more tricks of the trade.

Now to just find some appropriate stock to start from the excess pile.
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Old 02-01-2020, 12:01 PM
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Drilled and tapped to 10-32. Since the stick was long enough I repeated the
process on the other side. Why not make 2 eh? Cut it in half and thinned
down the shaft so it fits in a BXA holder. A bit of de-burring and voila...
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Old 02-01-2020, 12:11 PM
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Very nice work.
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Old 02-01-2020, 02:06 PM
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Originally Posted by milomilo View Post
Very nice work.
Plus one
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Old 02-01-2020, 10:14 PM
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Quote:
Originally Posted by Bubba View Post
A bit of de-burring and voila...
Walter, you got lots to teach us. Thank you.
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Old 02-02-2020, 05:59 AM
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Wow those look nice!
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  #9  
Old 02-02-2020, 12:08 PM
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Black oxide formula:

600 gm sodium hydroxide
25 gm sodium nitrite
Dissolve to a final volume of 1 liter in DI or distilled water

Bring to a boil
Immerse 10-30 min
Rinse well

Final product must be oiled, waxed or lacquered.

Use rubber protective gloves, protective clothing and safety goggles!
Hope it helps and good luck!

Note: this solution will boil at a much higher temperature than 212°F or 100°C
So if you need to add more solution, you need to cool to add solution, and
yes some of the water will boil off, covering your pot will help. Your pot or
tank will have to be iron or ideally stainless steel.
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Last edited by Shade Tree Welder; 02-08-2020 at 11:47 AM.
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  #10  
Old 02-02-2020, 12:14 PM
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Nice work. You did great on machining the pockets.

I have one concern. The screw used to hold inserts is a tapered head. With
CNMG inserts the hole is not centered on the insert when the insert is placed
in the holder. The hole is off center in the direction if the back corner of the
pocket, then when the screw is torqued it bends slightly to force the insert
into the corner of the pocket and the tapered screw when properly torqued
holds the insert into the pocket as well.

With out the proper holding forces from the screw I am afraid that the insert
will vibrate and crack in use.
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