[deadlykitten]

hello, please, i need your opinion about machining 3 parts almost identical.

For each part i made 3 drawings :
- the upper one is as it is
- the one in the middle is with dimensions
- the bottom one is where i have some isues
- all files share same content

- all parts have in common a o36.5 [ -0.05 .. 0] grove, with it sides required to be at 1.6 rugosity
......- how can i keep this condition while machining many parts ?
......- should i consider 2 tools ?

- all parts have in common a o25.11 [ -0.05 .. 0] outside diameter ( surface A ), which i intend to machine at 1st clamp
......- for 1st part, how can i realize the o26 [ -0.021 ..0 ] inside diameter, with 0.03 concentricity with A ?
............- only the 2nd clamp may input a 0.03 error from "jaw-part-clamping"

......- for 2nd part, how can i realize the o20.015 [ 0 .. +0.021 ] inside diameter, with 0.02 concentricity with A ? 1.6 rugosity ?
......- for 3rd part, how can i realize the o20 [ 0 .. +0.021 ] inside diameter, with 0.04 concentricity with A ? 3.2 rugosity ?
......- i intend to ignore the o20±0.2 gap in between, and machine continuous
......- these holes are pretty close, ~o20 [ 0 .. +0.021 ] x 68, which is not so long, ~3D, but i would like to keep that [ 0 .. +0.021 ] as much as it is possible

kindly !

[Superman]

What material ? I would guess 4140
What quantities ?

IMO, achieving concentricity is best done in 1 entire operation.( or as much as can be done in the same op )....use rougher & finisher OD tools
- 1st op - using Ø42 bar stock x 75mm setout from front of jaws - turn ALL outer features complete - drill & finish bore 68mm deep ( the 20±0.2 made to just under top size, It will minimise problems achieving bore size )
----- rear of bore to be good finish for clocking true for 2nd op

- 2nd op - use freshly turned "soft" jaws for 2nd op ( jaw bore turned to Ø25.25 / Ø25.15 )
( clock within 0.02 T.I.R. to maintain concentricity )
- face & machine bore to finish sizes

[deadlykitten]

hy. i think i will machine it like this :
- 1st clamp all exterior and main bore
- 2nd clamp rest of the interior

My only issue is that wall gets thin ~2.5, and i must realize, on both sides of this wall, tolerances closed to 21um and 50um.
I think i must slow down the process ( rpm , feed ), and even so, i am afraid of instability / vibrations.

About that interior o20 [ 0 .. +0.021 ] x 75 length : if i use a GO_bar at o20 [ 0 .. - 0.002 ], with it's :
...length = 20, than i will go with a turning knife, and hope to keep that tolerance
...length = 80, than i will go with a ?!?!? maybe a reamer ...

I must discuss control and stuff with the client

[Superman]

hy. i think i will machine it like this :
- 1st clamp all exterior and main bore
- 2nd clamp rest of the interior

My only issue is that wall gets thin ~2.5, and i must realize, on both sides of this wall, tolerances closed to 21um and 50um.
I think i must slow down the process ( rpm , feed ), and even so, i am afraid of instability / vibrations.

About that interior o20 [ 0 .. +0.021 ] x 75 length : if i use a GO_bar at o20 [ 0 .. - 0.002 ], with it's :
...length = 20, than i will go with a turning knife, and hope to keep that tolerance
...length = 80, than i will go with a ?!?!? maybe a reamer ...

Don't use a reamer.......it will only follow the previous bore
- you need to use a single point cutting tool to make it concentric

- 2nd op, part held in formed soft jaws, use a Ø20.000 / Ø19.985 slug up the guts to assist holding the part with a higher jaw pressure ( & stop any deformation )
--- the slug with also confirm that your bore is not undersize nor made out-of-round

[deadlykitten]

hello superman ... please, what means " slug up the guts " ? kindly !

[Superman]

hello superman ... please, what means " slug up the guts " ? kindly !

sorry "Kindly!" , Aussie slang at work
-to say it correctly......A section of solid bar, made to suit the finished bore, positioned to not interfere with the op.2 tooling, but located within the jaw clamping zone

slug=leftover piece, a bit of whatever is available
guts= middle, stomach, insides, etc

[deadlykitten]

i guess you mean something like this 01.jpg

material is something between olc45 and stainless steel

do you think, on 1st clamp, that i can hold the hole tolerance o20[ 0 .. 0.021] x 75 with a knife ?

about " slug up the guts ", are you also a "butcher" ?

also, next week i should meet the client, and he said that they are allready doing this kind of parts @ france ... maybe will share some details

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i need a steady tool ... i think i will go with a "carbide shank", or a "vibration damping shank", with some easter/ X-mas inserts )

i never used "vibration damping shank", but i think i don't need it now / or would they make a difference ?

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if you ask me, for 1.6 surface rugosity, i could go like this :

- o20-0.2 drill
- grind

it will take longer, and will be constant, while the knife will put me in the area off small offset corections, and those corrections won't last long

however, i don't like this idea, because the "metal powder" will get everywhere, even if i will use filters to clean the coolant and i will increase coolant debit near the tool ... this will filter a lot of powder, but there will still be powder left to ruin the machine slowly, in time, part by part

also i believe that this approach is too much for this part / operation, but maybe i will afford that )

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about the japanese text image : usually i stay exactly at the nort pole, but today i accidentally slipped to the asian region

kindly !