9x20 lathe, heavy cuts, HSS

[Elninio]

I've managed to grind a really good cutter this morning.

This chip is about 2 feet long, the shank in the background is 1" OD ground HSS.


Here is a 0.400" depth of cut chip. It cut like butter, no vibrations. I've noticed that, like drilling, you have to feed it hard enough to avoid chattering. It's much less "hard feeding" than drilling in a center-drilled hole with a 1/2" bit. On the little shaper, the vibrations really amplify. This wasn't the case. D


The cutter (Well the actual one is for left-handed cutting. This is Darin's tool, and I decided to copy it's design for use on the lathe). Relief is the typical 8-10deg. The rake is probably about 15 to 35 deg; I ground it using the corner of my grinding stone. The edge is 45deg , minus edge-grinding (especially on the tool tip radius), then I break the edge with a file.



Great finish. Feels slightly more coarse than the endmill when scraped with the fingernail. The chatter on the chamfer is from a similar tool. The edge or chipbreaker on that one was ground deeper on the distal end of the tool, which causes the chatter (since it's below center). Even the chattering looks smooooooooth.



I wasn't able to take the same depth of cut with carbide, even increasing the RPM's to a higher value. The chatter is just too horrible ..

[Carld]

That's interesting. What was your rpm and feed?

[S_J_H]

Yep, that is a healthy amount of metal removal for a 9x20. Nice job.
What type of steel were you turning?

Did you mean .4" off the diameter? ..as the chip looks like the cut depth was around .2"

I used to have a 9x20. I did a lot of work to that lathe. My Friend Rube has it now.
One of the mods I did was to make a set of pulleys so it could use 2 drive belts in the low range.
I had fitted a 1hp 3ph motor and VFD and with heavy cuts or parting it would snap the belt often. Adding the second belt eliminated that problem.

Steve

[Elninio]

RPM 1250,
I don't remember the feed, but it was pretty low. I had it set to cut a thread, and then reversed two gears to produce a nice finish. I decided to start taking heavy cuts to see if my sharpening was good. That's .400" depth, the bar was 0.800".

[Elninio]

RPM 1250,
I don't remember the feed, but it was pretty low. I had it set to cut a thread, and then reversed two gears to produce a nice finish. I decided to start taking heavy cuts to see if my sharpening was good. That's .400" depth, the bar was 0.800".

Forgot to mention, I took the .400 in steps, since I wasn't sure it could handle it, and there being no point to face each cut. That's why the chip looks thinner at the curled end, and thicker at the unrolled end. The weight of the chip cause it to break when i got close to .400, due to curling into the cutter ...

Another thing,

my lathe is on a 1 hp motor and i've managed to stall the motor at this speed. It could be that my feed was quicker, but I think it was due to the cutter having much less side rake. I've also stalled it on the lowest speed (higher torque), and the plastic gears didn't break. I'm sure they're break if I was running an 8" chuck at 2500rpm and then plunged the cutter into the chuck jaws ...

[bobw53]

I wasn't able to take the same depth of cut with carbide,

Because obviously carbide only comes in one flavor "Carbide". Those 600 page catalogs of carbide inserts are just for show.

[aheg1220]

Did you grind a special type of tool for this, or did you just manage to grind a darn good cutter? From the picture, i'm a little confused about whether or not you made a special tool.

[snowman]

I am having the same difficulty. Can you take a picture of the tool itself? On a plane paper background or something?

I can't seem to tell what the geometry is.

[PixMan]

In my first year of trade school, a teacher set out to prove he could take a 1" depth of cut using a Hendey gear head lathe. He set it up with a 3/4" HSS tool mounted in the 4-way tool post. The material was 1020 hot rolled steel. He started the machine and instructed a student to use a broomstick to break the chips off as it cut.

The first few minutes were fine, and everyone was in awe at how that little 14" 1HP machine could take such a huge chip in back gear. The student breaking chips let it go a little too long though, and one chip about the size of a car's coil spring flew out, up about 10 feet and struck the metal window frame about 20 feet away. It smashed the glass and left a huge dent in the frame that stayed there until they razed the building 3 years ago.

Those little machines have the capability to do things most of us would never imagine. And we can get hurt or killed if we aren't careful.

[Greebe]

I too would like to see a better picture of the tool bit. Maybe one from the top sides and front.

Thanks
Greebe

[Elninio]

It's your regular cutting tool but with what i see is being called a 'chip breaker'. Maybe its supposed to act as a chip breaker, but in my case all it did was curl the chip (which is a good thing), but also it changes the rake values. So ... its not 'just' a chip breaker'; i wouldn't say it's fair to call it just that.

[snowman]

Looks similar to a box tool grind for a turret lathe.

[S_J_H]

I still had these pics on Photobucket.

This was the dual belt setup I made for my old 9x20.
I made the extra pulleys, modified the intermediate pulley for sealed bearings and made a new stronger steel shaft. I also made a wider tensioner pulley for the extra belt.
The detent clutch was eliminated.
It worked really nice.





Steve

[Elninio]

Now i understand; there are two versions of the 9x20. In canada busybeetools sells the one you've got, and king sells the one i've got. One of the differences is the belt thickness, another is that mine has a sealed gearbox. I would have done the same

[Greebe]

I too would like to see a better picture of the tool bit. Maybe one from the top sides and front.

Thanks
Greebe

-- Pictures?