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  1. #41
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    Quote Originally Posted by angelw View Post
    My math is just fine. The contact with a 7.08 rad form tool, with the profile being discussed, is through 162.757deg. Unwrap that and its 20.1117 (0.7918").
    But not all of it is really cutting. Most of the real cutting is on the nose.

    Unless the tool is profoundly positive rake and minuscule feed rate ...
    HA ! there's your problem right there. You can't use a "miniscule" feed rate with form tools. They chatter. You gotta dig in and cut.

    And yeah, it was positive. I can grind a HSS tool okay. Had a holder for them, spent a half hour making a special tool, came back and was making parts in an hour. Would have taken three days and several hundred dollars to get carbide face groovers and a holder delivered. That particular lathe was only 11,000 lbs, but not linear ways, not feeble, could take a cut. I only work with alloy steels, no ledloy. This happened to be 8620 but I've done the same with 4130, 4142, 9310, 7075 aluminum. Admittedly the 9310 is a bitch.

    No chatter. Parts finished the same day I got the order. Big bubbles, no troubles. Old methods can work too.

  2. #42
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    Quote Originally Posted by EmanuelGoldstein View Post
    No chatter. Parts finished the same day I got the order. Big bubbles, no troubles. Old methods can work too.
    I know that you live in the past and like the old methods, given your propensity not to use Constant Surface Speed for turning, or Cutter Radius Comp for Thread Milling. But simple logic comes into play when choosing an appropriate cutting tool for a job, particularly when only two parts are involved.

    Let’s be generous and consider that the 8620 you were working with was at the low end of the hardness range. Accordingly, the Surface Speed for HSS would be around the 30M/min mark. You stated that you were cutting a face groove; accordingly the major diameter of the groove must have been larger than 38.1mm, otherwise you would be exercising a boring operation, not a face grooving op. So let’s pick an arbitrary minor diameter of 25mm, giving a major diameter of the groove of 63.1.

    Calculating the RPM for the Major Diameter, results in 151. The machine better have some torque at those revs, with a tool that wide, if, as you put it “You gotta dig in and cut". And it get worse as the diameters go up. Extrapolating the Surface Speed for the part of the tool cutting the Minor Diameter, results in 11.9M/min. Quite a spread.

    I just don’t buy it that one would logically pick up a 3/4” wide tool and think, yeah, that tool won’t give me any grief, I'll use it, particularly when only two parts are involved. If forced to make a tool out of HSS, I would rather be scarfing a smaller section to clear the bore of the groove major diameter, than a piece of 3/4".

  3. #43
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    Quote Originally Posted by angelw View Post
    I just don’t buy it that one would logically pick up a 3/4” wide tool and think, yeah, that tool won’t give me any grief, I'll use it, particularly when only two parts are involved. .
    2 pieces and a cnc, yes I'd just put in a 1/8 wide full nose vee-bottom or topnotch, post it in the CAM and go walk away doing other work while it does it's thing.
    You could code this by hand but that would very time consuming and prone to typing or oopsy math errors.
    5,000 or million of them and it becomes different thinking and maybe seconds in cycle time do count.
    Bob

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    I fish with dry fly's in the Spring, and wet during the Summer. Just saying...

    R

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    Quote Originally Posted by angelw View Post
    I just don’t buy it that one would logically pick up a 3/4” wide tool and think, yeah, that tool won’t give me any grief, I'll use it, particularly when only two parts are involved. If forced to make a tool out of HSS, I would rather be scarfing a smaller section to clear the bore of the groove major diameter, than a piece of 3/4".
    22,000 lbs and 40 horse continuous, 60 for 15 min/hr. 3 gear ranges. Full torque at 50 rpm.

    I didn't have a face groover that would work, it would take $100 for a box of inserts and $300 for the holder, plus several days, probably a week, to get them (Western Tool sold Manchester but never had stock). I had the 3/4" HSS in the toolbox and a holder they fit. Took a half hour maybe to grind the tool.

    HSS comes in squares, anything smaller and it's going to be pretty weak in the load direction. I've done smaller as well. They tend to break.

    You may remain convinced that waiting a week and spending $400-500 dollars more is the better way to make those parts. That's fine. But personally, I was happy with the way the job worked out.

    Your earlier claim was, can't be done, or doesn't work, or something like that. I guess you're right, it's impossible.

    added : I'll take your CSS lathe program, rewrite it to defined speeds and it will run better. Guaranteed. I know you don't care about that but some of us do. The Zen of Running Machine Tools, if you like. CSS sucks for roughing, period.

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    10+ posts a day for 7 months...about Archaic Machinery that isn't readily available anymore. In the CNC sub-forum. Yay.

    R

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    Quote Originally Posted by litlerob1 View Post
    ...about Archaic Machinery that isn't readily available anymore.
    All ya need is money, honey !

    Archaic Machinery Company


    btw, angel - the incident of suggesting to not use cutter comp was on a 1/4-20 thread. Given how tight the space for the cutter is, I'd still not use cutter comp. If you don't know how to program to cl, well, that's fine but I'd consider it a useful skill for these situations.
    Last edited by EmanuelGoldstein; 12-07-2019 at 10:11 PM.

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    Quote Originally Posted by EmanuelGoldstein View Post
    All ya need is money, honey !
    Johnny Larue to a tee.

    Quote Originally Posted by EmanuelGoldstein View Post
    btw, angel - the incident of suggesting to not use cutter comp was on a 1/4-20 thread. Given how tight the space for the cutter is, I'd still not use cutter comp. If you don't know how to program to cl, well, that's fine but I'd consider it a useful skill for these situations.
    As I replied to your banal argument back then, you can still program Centre Line and use TRC, taking advantage of being able to size the thread without having to edit the program. As others in that discussion pointed out to you, there are many factors that influence the actual size cut when Thread Milling. If for a Thread Milling operation, you think you can initially get and maintain size through out the life of the job more conveniently by editing the program, then you're playing with one tool in particular a little too much.
    Last edited by angelw; 12-10-2019 at 05:37 AM.

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    Whomever it is, it's annoying me enough that I don't want to read it's posts any more.

    Who posts that much in 7 months?


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