Got a nice finish on 303 stainless

[spaceman_spiff]

material	rpm	diameter	feedrate	radial doc	sfm	lube	direction	chips	tool	notes
303SS	581	1.175	.005 auto	.005 to .010	179	WD40	spindle	breaker	TPG322?	barely feel finish with nail
303SS	860	1.175	.005 auto	.005 to .010	264	WD40	spindle	breaker	TPG322?	barely feel finish with nail

Machine: Atlas 10F from 1940's
Stock held in 4 jaw chuck, center drilled and supported with live center in tailstock.
Stickout about 3" from chuck.
Insert: I think its a TPG322

thought i'd share..getting a good finish on steel is a small battle and I think this one I had a victory!

the good finish is in the middle..please ignore all the other, uh..."attempts"

the carbide is an insert, with a fairly large radius, i'd say probably 1/32". The one visible in the picture with the sharp corners is the chip breaker installed on top of it, which doesnt actually cut the finish.

 

[Wreck™Wreck]

If the last picture is a chipbreaker atop a tp insert it is way in the wrong place, I am surprised that you didn't scag a bunch inserts beforehand.

 

[Holescreek]

It appears that the insert you're using is too small for the tool holder. It's certainly not in the correct position, you're cutting on the back relief in the photo.

 

[spaceman_spiff]

If the last picture is a chipbreaker atop a tp insert it is way in the wrong place, I am surprised that you didn't scag a bunch inserts beforehand.

thanks for noticing, yes it is, I have no idea how to use it. how is the chip breaker supposed to be installed?

 

[spaceman_spiff]

It appears that the insert you're using is too small for the tool holder. It's certainly not in the correct position, you're cutting on the back relief in the photo.

the insert thats visible is the chip breaker which is not doing the cutting..I have no idea how its supposed to be installed so I just put it kind of off to the side

 

[spaceman_spiff]

heres a pic of the insert and its chipbreaker..I think the insert is a TPG322

 

[Wreck™Wreck]

One of the most annoying traits of stainless is how soft it is, it often makes large birds nests of chips which wrap around the tool and work causing a poor finish and tool breakage.

A clamp-on chip breaker forces the chip to curl tightly and break (if you are lucky).
Like so.

Increasing the feed rate and/or DOC creates a thicker chip that is more likely to break.

Flood coolant helps a great deal as it cools the chips and makes them easier to break. Negative rake inserts with molded chip breakers are the way to go but are probably not a good match for your machine.

Also skip the WD40 on steel, use a lightweight tapping/cutting compound, biodegradable of course.

TPG 322 insert means
Triangle Positive Ground, 3/8" IC, 2 X 1/16 thick, 2 X 1/64 nose radius. A TPG 321 insert would make you much happier with a 1 X 1/64 nose radius.

 

[Karl_T]

here's what mine looks like

 

[spaceman_spiff]

ahh thanks guys..so the chipbreaker increases the angle that makes sense..I was thinking somehow it cut the chip duh

These TPG inserts and the holder were basically free so I had to try them out.

I also have a bunch of CCMT and CCGT inserts, so I just bought a holder for them. Those are positive rake although they have a very fine radius..I think I have the "0" versions which are supposed to have no radius. Oh well at least they were free.

 

[Wreck™Wreck]

I also have a bunch of CCMT and CCGT inserts, so I just bought a holder for them. Those are positive rake although they have a very fine radius..I think I have the "0" versions which are supposed to have no radius. Oh well at least they were free.

All tools have some nose radius otherwise they would fail almost immediately. Coated inserts have a small radius on the cutting itself due to the coating process, many negative rake inserts for steel have a visible radius on the cutting edge, this requires a rigid machine to work effectively.