Stainless steel machinability???

[Jasonsmack]

I went and broke my plastic trigger guard on my SS Savage 93 yesterday. Would it be a reasonable project for me to try and build a new trigger guard out of stainless steel to match the gun? I have a milling maching but mot much experience with it yet. Am I asking for trouble trying to cut stainless? I have never tried it before. I am able to cut aluminum and steel with decent results - it just takes me a long time. Any other tips or suggestions would be appreciated.

 

[Canuck223]

Stainless seems to grow more while machining due to heat. Cooling jets are needed, and it's best to plan on undercutting at first, then measure the cooled part.

 

[mercuryv8]

Enter the material slower than you would with steel. Heat as the last guy said is important. Cutting must also be slow.

My limited experience...but I hope it helps, maybe keep you from breaking an end mill.

Nic

 

[7018]

Definately slower RPM, slower feed, lots of coolant, flood type if possible and a good sharp endmill.

 

[triggerpress]

Stainless steel, like carbon steel, is not all created equally. I'm no expert by any means but what works for me is to break the stuff down into two groups: magnetic and non-magnetic. Usually the magnetic stuff has a number that starts with 4; the non-magnetic has a number starting with 3. The 400 series stainless (which is what is used in most firearms manufacturing) is not too bad to machine. Use a good end mill (cobalt if possible) and don't let the heat build up. You'll make out okay. The 300 series stuff is used in industry for shafting and other purposes and is absolutely ugly to machine.

Maybe we can get an "expert" to go beyond this....or correct me.

triggerpress

 

[farmnut]

Use 303 stainless. Cuts like butter.
Well more like mild steel.

 

[buckbrush]

Most stainless firearms are 416, or 410. Virtually all ss barrels are 416. This is easy maching stuff, very easy to work with.

 

[Jasonsmack]

Thankyou for your help guys. I will order some 303 and 416. I have a couple of simple projects on my mind now and the info you gunutz have given me has pointed me in the right direction. I will maybe start a different thread when I get my metal and start cutting. I am sure I will need a bit of help when I get that far too.

 

[Ripstop]

At work, I cut 420SS and 316SS at 60% speed/40% feed of regular carbon steel (1045). Coolant is your friend. That is more for the lubricating aspect than for cooling effect. The 60/40 works quite well for all stainless.

Good luck and I hope it turns out well for you.

 

[precision_lee]

well speed and feed are are more then just 60 and 40%, you have to input spindle speed number into a cnc before you can cut, and feed is the same deal(60 percent of what?)..and by the sounds of it you are using a regular mill so give me a message and you can phone me when you start to cut, I was a r&d machinist for the last four years in a medical instrument and fracture fixture company and 90 percent of my cutting was done on stainlesses, any trouble with surface finish call me about that too..i'll get you on track. Lee

 

[svt-40]

Just take very thin shavings, do not go deep in and you will be Okay. Milling is not as tricky as turning, where it's quite easy to break tools by going in too deep. SS is very chewy

 

[Ripstop]

well speed and feed are are more then just 60 and 40%, you have to input spindle speed number into a cnc before you can cut, and feed is the same deal(60 percent of what?)..and by the sounds of it you are using a regular mill so give me a message and you can phone me when you start to cut, I was a r&d machinist for the last four years in a medical instrument and fracture fixture company and 90 percent of my cutting was done on stainlesses, any trouble with surface finish call me about that too..i'll get you on track. Lee

Ummmm..... 60/40% speed/feed of carbon steel like I stated in my post. Even on CNC machinery you have manual overrides if you cannot calculate the ratio yourself. I've been working for 27 years on all types of material. Of course I will admit that I am a lathe geek but this does work with other machinery.

Example: If you cut carbon steel with a CSS of 150, then the SS speed would be 90.
If you had DSS of 600, then the SS speed would be 360.

CSS - constant surface speed, DSS - direct spindle speed, SS - stainless steel

If you use a feedrate of .38 MPR, then the SS feed would be .15
If you use a feedrate of 3 MPM, then the SS feed would be 1.2 MPM

MPR - meters per revolution, MPM - meters per minute

You would use MPR with CSS and MPM with DSS

Also I would like to add that I only use indexable carbide inserts. We seldom use HSS tooling anymore. These equations should work just the same for HSS. Hopefully I am not confusing anyone, these simple equations come naturally to me.

 

[thecollector]

Stainless steel, like carbon steel, is not all created equally. I'm no expert by any means but what works for me is to break the stuff down into two groups: magnetic and non-magnetic. Usually the magnetic stuff has a number that starts with 4; the non-magnetic has a number starting with 3. The 400 series stainless (which is what is used in most firearms manufacturing) is not too bad to machine. Use a good end mill (cobalt if possible) and don't let the heat build up. You'll make out okay. The 300 series stuff is used in industry for shafting and other purposes and is absolutely ugly to machine.

Maybe we can get an "expert" to go beyond this....or correct me.

triggerpress

Your best choice is 416 stainless; as this is a re-sulfurized free machining stainless steel specificaly for cutting applications. 416 is near universal in firearms fabrication because of its machinabilty, and it is a heat-treatable martensitic stainless steel, whereas the 300 series austenitic, and the ferritic series are not capable of being strengthened by heat treating.

 

[buckbrush]

416-R is what is used in ss rifle barrels, I know Crucible steel only does one melt a year of this stuff. I am told it is specifically formulated for rifle barrels.

This stuff machines much better and easier than the 4130 heattreated crome moly used in most rifle barrels.

 

[farmnut]

Hey all you SS experts read the original post,
he want's to make a trigger guard not a barrel.
So what if 303 can't be heat treated, why would you want to.
303 is free machining and easy to get.
Try it you will like it.

 

[Jasonsmack]

Just a trigger guard - I do not need to heat treat. I will take it very slow - I am in no hurry. I just have a medium sized chinese milling machine and have not set up a cooling system on it for anything I have done on it yet. It should not be a problem to run coolant on it though. I imagine a water soluble oil would be suitable for coolant? I have lots of experience cutting and grinding engine parts from my last job (automotive machine shop) but transferring that experience to this project is a stretch. I have ordered some 303 and will give it a try.