In the original post it is stated he is using a 50mm bar.
On the Haas lathe I run the spindle speed variation thingy is M38 and M39. M138 and M139 are for the live tooling. It may have been a typo or that may have been why you had little luck with it.
Hi
@kenton , you're right- It was a typo - I use it for Ø50 drilled holes, but the bar itself is Ø40. You're right about the second one too. BTW - What's your opinion on the M38/39 thing if you've used it? Apart from not having a lot of luck with it, I'm thinking that it must add some wear to the machine to rev up and down like that.
@Mtndew - The machine has half indexing (24 pos. turret) and it came with a double or triple holder actually, but its got 20 or 25 mm holes. Sorry for inaccuracy, it's in a drawer, never been used due to the bars being to close to each other - for most parts I've made the neighboring bar would collide with the part. I also want to use as thick boring bars as possible. For this part that I'm doing now I've got 200 mm overhang on a 40 mm bar, so that's 5xD & resulting chatter. Just chatter towards the free end of the part though.
While I'm at it, here's exactly what I have:
Material: 316L - Ø120 mm - cut to 200mm length
Fixation: 3 x grip jaws - 35 mm grip length @ approx. 15 bar chuck pressure
Ø40 boring bar - 5D overhang with Kenna DNMG 150608MS - KCU10 insert.
Running at VC140m/min, F0.45mm/r, 2 mm DOC. Making nice chips, but with a hell of whistling due to chatter.
Turning the hole which is 185 deep from Ø50 to Ø95.
@Ox - You nailed it I think with "
if your bar has a flat on it, a split bush will likely end up gitt'n sprung, creating the %^$$#! issue with sliding / removing it that you describe". I remembered incorrectly - it has a flat on it unlike what I first wrote. The bastard is so stuck that I can't remember the last time I took it out of the holder. Nearly stripped the head off the set screw that you need to tighten in order to widen the "clamp". Now it's set fully through and resting against the backplate of the holder - which is convenient because I don't need to jerryrig the bar with an IC hose.
As for feed, speed & DOC - I just don't get it. I've used the same figures before and it was (almost) fine with little chatter. I realize that everything I'm doing in the 5 X D range should chatter, but like I say, it has worked before. That's why I'm wondering a bit if 316 is not always the same. I've played around with feed and speed with little effect.
Right - now it's past my bedtime!
Cheers,
John
We (4 guys) are first, and foremost, engineers who happen to love solving operational problems, doing all the design work and, as it turned out, starting actually making our own parts. In the past two years the machining has moved from a "hobby" to a full-blown job where everything we do is self-financed and taught (albeit the latter with a great deal of advice & help). We started with cheap router tables, then a Multicam, the Haas lathe & in 6 months we get a brand new Okuma mill. Maybe we'll have one of those Hermle machines in 5 years time, just because we can.
