Stainless steel woes!

[lazylathe]

Hi All,

Well i dusted off the Myford to make a part for my Goodell-Pratt 2 speed hand drill!
Did not take long but i had some serious Issues!!!

Turning was the easy part! I could get the shape and size easily!

Then it came to drilling...
Out comes the center drill and it went easy enough. Took a bit longer but it drilled the hole.
Then comes the drill bit... Lots of screeching and complaining and no real action! ???
Gave up on the hole as an i can do it later project!

Now i needed to part it off!
Out comes the freshly ground HSS cut off tool.
Starts out well but ends up turning blue and smoking really fast and turning into a nice concave forming tool instead!

Had to hacksaw it off and face it!!

No idea what type of stainless it is except it is HARD!!!

Any ideas for my future endeavors with this nasty stuff???

Andrew

 

[gbritnell]

It sounds like 304 or a similar grade. It's hard enough working with unknown regular steels, no less stainless.
The reason it turned ok and center drilled ok was probably because you kept pressure on the tool and cut a reasonable amount of metal off. When it came time to drill you didn't keep enough feed into the material and it work hardened and dulled the drill. It helps to use a lubricant also.
As for cutting off, most people are tentative about this process to begin with so once the feed is reduced you have the same situation as when you tried to drill it.
Speed is very critical when working with stainless also. You have to run it slower than a comparable diameter piece of mild or carbon steel.
I only work with 303 stainless and have the different pieces marked as to what they are (grade).
gbritnell

 

[Blogwitch]

Andrew,

I use a lot of donated (unknown) stainless and the only way to cope with it it to treat it rough. Like George says, if you let it 'skid' at all, it will produce a hardened face straight away that is very difficult to restart again.

What I do if that happens, is break out the tungsten tipped tools and get rid of the hardened surface, then go back to using normal HSS tooling.

Hard plate drills work wonders when drilling holes in unknown materials.

http://www.leofixings.com/fixings-products_Drill+Bits_Hardplate+TCT+Tipped+Drill+Bits-10-132.html

A high pressure cutting oil is essential when working with this stuff.


John

 

[lazylathe]

Thanks for the responses!!
I thought it had hardened... And all through my mistakes!

When drilling it i went as hard as i could and not too much happened.
Think i will remake the part out of CRS or something similar.
It does not have to be such a hard material, it was all i had.

Will post some pics of it later.

Andrew

 

[MachineTom]

I do alot of work with SS almost all the dreaded 304 type. Get a set of Cobalt drills and keep them sharp, if you don't own a drill sharpener buy one first. Here are the kind of speeds I use 1/4 600 rpm, 1/2 300-400, 1" 150.

Things to keep in mind when working with materials that work harden, lube shoot lube down the bore each time you clear the chips, if drilling and you hear a squeal, retract and clear the chips, if the chips are not falling out the drill bore clear the drill. The biggest issue is as the bit goes deeper into the material, the chips jam up in the flutes, at that point the bit stops cutting and is rubbing and hardening the material. If you are step drilling say a 2-3" deep hole, drill the 1/4 1" deep, then drill a 5/16" bit just a bit less than 1" deep, this will give space for the chips to travel through then drill the next 1" and again follow with the 5/16.

 

[Springbok]

Hi Tom is absolutely correct. and as us old codgers say slowly slowly catchee monkey.
When useing unknow metals allways go steady use lots of cutting oil not sure if you have variable speed but go slow at first
Have a nice christmas.

Bob

 

[neptune769]

Hello All,
I have worked for a company that manufactured medical diagnostic equipment. I worked there 5 years. 3 of that on a manual lathe. I never ran coolant or oil while cutting. I used HSS drills and some Carbide inserts as well as HSS hand ground turning tools. ONe part in particular was an alignment pin. It was .250 long and .177 with a .0002 tolerance. Yes that is 3 zeros. I started with .250 rod. I took it down to .1775 then polished it to size with Scotch Brite. There were many other parts using 304 but I can't recall any others at the moment. I guess I made so many of these I was so traumatized that I forgot the other parts. :'( I don't ever recall having a problem with 304. Only on the 316. That stuff is a real pain in the rump to cut dry. All I can say is make sure your tools stay sharp and don't let them get to hot. While drilling peck more than usual. Good luck.

Regards,
Dennis

 

[rake60]

If the stainless is 304 it is real tough to manage in a hobby shop.

304 stainless requires sharp tools, positive rakes, high tool pressure and SPEED to
keep it from work hardening.

I hate working with it myself.
The opposite of the spectrum is just as bad.

I have machined pure copper.
It is very soft so how difficult could that be?
It gums up on tool and ends up galled to the work piece.

That often resulted in coming into work and seeing a note from your buddy that read:
"Tool broke, piece moved, went home early, sick."

I can't say I miss those days!

Rick

 

[lensman57]

Hi All,

Well i dusted off the Myford to make a part for my Goodell-Pratt 2 speed hand drill!
Did not take long but i had some serious Issues!!!

Turning was the easy part! I could get the shape and size easily!

Then it came to drilling...
Out comes the center drill and it went easy enough. Took a bit longer but it drilled the hole.
Then comes the drill bit... Lots of screeching and complaining and no real action! ???
Gave up on the hole as an i can do it later project!

Now i needed to part it off!
Out comes the freshly ground HSS cut off tool.
Starts out well but ends up turning blue and smoking really fast and turning into a nice concave forming tool instead!

Had to hacksaw it off and face it!!

No idea what type of stainless it is except it is HARD!!!

Any ideas for my future endeavors with this nasty stuff???

Andrew

Hi,
I think you need carbide tooling and special cutting oil for SS all the way,
HSS somehow doesn't do so well with this stuff. Also try and get your speed and feed spot on.

A.G

A.G

 

[kcmillin]

I agree, 304 is a machining nightmare. Do whatever you can to keep it from getting hot. I generally peck drill 25 thou at a time with a 1/4" bit.

I have machined pure copper.
It is very soft so how difficult could that be?
It gums up on tool and ends up galled to the work piece.

That often resulted in coming into work and seeing a note from your buddy that read:
"Tool broke, piece moved, went home early, sick."

I can't say I miss those days!

Rick

I just worked with copper for the second time at work today. I got to make two copper bolts 1/2"-20 thread, turned down from 3/4 by 3-3/8" long. I found the magic number to be 900rpm with .002" feed, with flood coolant it came out with a very nice finish. Any faster feed than .002" and it leaves a sandpaper finish, literally.

The real fun came with single pointing at 700rpm. It took about 15-20 passes to get a good thread. Needless to say they were some very expensive bolts, not to mention the rest of the "extremely high current resistor" they go in.

Kel

 

[portlandron]

When you get back to drilling the hole, if possible, try drilling from the opposite side you started the hole on as it may not be work hardened on that side. You will still run into the hardened area but hopefully it will not be very deep.

 

[titex]

Lazylathe,
If it is 304, then that really is the dregs of the s/s family. 304 it's a w***e, 303's the one for me. S/S is notorious for work hardening in a flash
which seems to be what you are experiencing. You MUST keep up the feedrate, don't let the drill dwell even for a second.
The best style of drills for S/S have reinforced webs to handle the increased thrust load from heavy feedrates. but you don't need to go to that extremes. like is said just keep up the feedrate [neat cutting oil is also a good help].
Titex.