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gramps
01-27-2002, 09:42 AM
I have a small cnc lathe that is great for
contouring and cutting tapers etc.
The main problem is long stringy swarf.
My machine is home built and not really
ridgid enough for more than .025-.030
per pass and the amount of swarf generated
is astonishing. It quickly turns into a
birdnest and I have to stop the lathe and
clear the mess. It kind of spoils the fun.
I am ready to go for some kind of chipbreaker insert and I could use some
suggestions. I do both turning and boring
and need something that can follow contouring
both outside and internal. An insert that I
can mount in my own boring bar and also use
for turning would keep the cost down.
Any help would be welcome.
Gramps



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kap pullen
01-27-2002, 09:54 AM
Gramps,
Try leaded steel 1117L (free machihing ), or 303 F. M. (free machining stainless).

The stuff cuts like butter and makes little chips becauce of the sulpher, or lead in it.

It's not as maluable as regular material so don't plan to make a head and "rivet" it over
cause it'll split.

Kapullen

Thrud
01-27-2002, 03:53 PM
Gramps:
If you are using inserts now, it sounds like you need a different insert. I also had this problem, but after discussing it with a Kennametal rep they suggested more appropriate inserts for my tooling. Good people to talk to - they really know their stuff! They can get you those nice "9" (or "6" for the guys in Australia) chips that are desired.

Dave

gramps
01-28-2002, 08:32 AM
Thanks for the response guys. I have the
most trouble with aluminum(which I forgot to mention in my first post).I will call Kennemetal today. Over the years I have been given various inserts by friends and have
some success but I guess its time to call
the experts. What do you think about the solid carbide boring bars? Are they worth
the money?
gramps

SGW
01-28-2002, 08:37 AM
Kennemetal (I think it's them) sells a "microchip" aluminum alloy that comes off in tiny chips almost like brass. Assuming its physical properties are appropriate for what you're making, that stuff would certainly solve your stringy swarf problem.

hms50
01-28-2002, 08:49 AM
Hi Gramps!

The solid carbide bars are very nice but also very expensive. I got some with a surface grinder bought at auction, the auctioneer thought they went with the grinder! They are my first choice when boring. Very ridged and no spring. My lathe is just a 9" South Bend and while a good lathe for it's day and price is not as solid or ridged as many of the newer machines. I'll bet the carbide bars would perform even better in those.
hms50

kap pullen
01-28-2002, 09:55 AM
Gramps,
I run a heavy feed and light cut on aluminum
to break chips. Keep it kool too.

The heavier the chips, the more brittle they are. They'll curl around and break on the tool or the un-cut surface.

I run the cnc .1 depth and .01 to .02 feed and it breaks em pretty good. Experement.

Heavy feed, light cut seems to make less chatter too.

I don't like those knarley chips the little inserts with chipbreakers make.
They like to stick on my cheek, or lip.

Just my preferance.

Kapullen

Thrud
01-28-2002, 03:43 PM
Gramps
As far as carbide bars go, they are the best because they dampen harmonic vibration. It is tough to justify their high cost unless you get lucky like SOME people and score them at an auction! You can overhang them up to a 11:1 ratio - great for deep precision boring.

Dave

gramps
01-29-2002, 06:42 AM
Thanks for the help guys.
I will try your suggestions Kap.
Gramps

hms50
01-29-2002, 09:17 AM
Hey Thrud,

If you think I was lucky with the boring bars, I won't even tell you what I got the grinder for!! In my neck of the woods things have been going cheap for several years. In August, a friend bought 3 bridgeports to rebuild, (J head) for $500 each!

hms50

spope14
01-29-2002, 03:47 PM
I will ask for information here from you. What size of shank for the tool can you use. I have some lathes in my shop - 13 inch that I use a CTAP-R holder on (I believe this is it) and a TPU or TPG 221 -222 insert in the holder (1/4" IC). This is a positive rake tool as indicated by the insert, and does quite well in reducing needed power and still giving the flex of carbide. The insert is a clamped style - no hole. The holders run about 36 - 45 dollars, an inserts can go from 1.65 to 2.50 each. There is a chip breaker you can buy for these inserts, and it works great - clamps on top, and is slightly adjustable to the front or back for your needs. I believe the chip breaker is T--D 22 (forget the middle letters), but you will need to look it up. Get my stuff from MSC, but any catalog can do this. This has been a method I have used for years, wih excellent success.

The benefit of the positive rake over the neg rake inserts and holders is the less power needed, and less speed needed. Less pushing of the material, as done by a negative rake tool. Drawbacks are more wear in some instances, interrupted cuts effect on the insert.

For a small CNC lathe, I have adapted a holder for my CNC5 Emco machine for this purpose, now can go to .040 deep on steel, .050 on Aluminum. This lathe is a real weakling due to the turrett rigidnessn only, the rest of the iron is fine.

Thrud
01-29-2002, 05:24 PM
Hms
It is getting tough to find good used stuff around here - you have to watch auctions and sales like a hawk.

Just got a new never used fully programmable Mitsubishi VFD for up to 3Hp (2HP constant torque). It can drive the motor up to 400Hz. (yeah!) and much, much more. Got it for 1/3 wholesale. Now all I need is another 230V outlet and a c-flange 3Phase VFD motor!

gramps
01-29-2002, 08:14 PM
To SPOPE14 I can use up to 1/2 square
tool bits....and 3/4 round boring bar.
The tooling you talked about in your reply
sounds like what I need.
I will take another look in the MSC catalog.
The inserts from J&L go for big bucks.
$10.00...$16.00 each!!!
Thanks again to all.
Gramps