J Tiers..SB depth of cut question?

[torker]

JT...was just wondering what the deepest cut you've made with your SB? I've long ago changed over to the way you explained it to me (sharp tools, back gear, low gear). With mild steel I usually cut .060 but tonite I was in a hurry to turn down some hubs from 4" dia X 1 1/2" thick flame cut blanks from plate. The ol' SB9 will easily cut .090 DOC but it's grunting pretty good. I'm thinking you take deeper cuts than this so what is the limit you've found? I'm not sure that I've got the tool sharpening down to go much further. Thanks!
Russ

[Arbo]

I'm not JT, but will chime in anyway. I have a SB 9" model A. With the proper set-up, I can easily take .125 DOC in back gear on 2" diameter 1018. I keep my belt loose enough that it will slip on the pulley if anything bad happens. A steady drip of Tap-Magic even gives a fairly nice finish on the turned piece.

[J Tiers]

I AM J Tiers, and I have a Logan, not an SB.

But I often cut a 0.125 d.o.c. (1/4 off diameter), at a slower feed, like 0.004 or so. Most ever has been about 0.187. Tough materials like 4140 prehardened may not take that until smaller diameters under 1"

Tool a "slicer" with lots of side rake, no particular back rake, and sharp. Hardly any nose radius, just enough not to break off.

Have not used back gear, but do use slower speeds. As fast as it will stand without stalling due to flat belt.

[This message has been edited by J Tiers (edited 04-14-2005).]

[ACF]

I'm not JT either, nor do I have a SB lathe, but thought I'd add my $0.02. I think the real question here is, how many cubic inches of metal can the machine remove per minute (hour, sec., etc.). This is determined by the horsepower avaiable at the spindle.

I've seen statements in the machining books that say most machines can take a DOC of "X". This doesn't say much, but, if you look at the cu.in./minute of metal removed, that is the bottom line. The DOC, the feed rate, the spindle speed, and the diameter of the workpiece all have an influence on the metal removal rate. This assumes your machine is rigid enough to use whatever HP you have powering it.

There are formulas for figuring this out in Moltrecht's book, however, if I recall correctly there was an error in them.

Chris

[J Tiers]

<font face="Verdana, Arial" size="2">
I think the real question here is, how many cubic inches of metal can the machine remove per minute
</font>

Depends on what you are doing....sometimes you almost have no choice, like cutting a stem 0.093 diameter 1" long on the end of a piece of 0.375 stock.

If you try to go back and touch up when you are close to final dia, it will bend, most likely, so you are sorta stuck with a deeper d.o.c. direct to dimension from some considerably larger diameter.

[ACF]

Maybe I misunderstood Russ, I thought He was just trying to hog off metal. IF your goal is to hog off metal then your only limited by HP and the rigidity of the machine.

I do understand that there are times when "hogging off metal" is not called for.

Chris

[torker]

Thanks guys!
JT...sorry about the SB crack! I think you told me about this on a Southbend forum or SB question some time ago. I just assumed you had a Southbend.
AFC...yup, that's what I'm doing...getting some 4" blanks turned down to 2 1/4" on one side, cut length 3/4"
JT and arbo...I must be almost there. Didn't have much time tonight but I tried .110 DOC just a few minutes ago.
It did the same hunker down grunt and just peeled it off pretty as you please. Seems strange watching .220 disappear in one pass with a 1/4 hp machine.
I would have taken more but I ran out of cutter profile to work with. I'll have to grind a longer edge.
Another thing is maybe a little too much nose radius as you say.
What a nice way to turn metal down though. It obviously makes some hella big swarf but it's coming of at a much more managable speed than the cuts I usually make.
Now I just have to be careful not to turn things down too far
Another suprise.. when the cut is finished and you roll back the handwheel, the cutter doesn't touch the part. Doesn't make sense, with all the spring back it SHOULD have, you'd think the tool would really dig in on the way back.
I'm also pretty impressed with the finish it leaves. Thanks again!
Russ

[wierdscience]

Here you go Russ,I use this tool grind from time to time when I have a dump truck load of chips to remove from a part.It IS free cutting just as advertized.

I have insert holders galour at work,but nothing beats this for raw stock removal in a single pass.

Last time I used it was on some 4140 pump shafts,6" od was being brought down to 4" for a length of 32" on each end.I managed a 7/8" DOC But not on a SB lathe

SB claims in thier propoganda that a 9" will make a .250" DOC in 3" diameter corld rold,in backgear.From having used this grind in several different lathes I tend to think it possible.



[This message has been edited by wierdscience (edited 04-16-2005).]

[wierdscience]

wait a minute,it's coming

[This message has been edited by wierdscience (edited 04-16-2005).]

[precisionworks]

Wierd,

What's the title & date of printing?

------------------
Barry Milton