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[Newbie] Advice machining stainless steel.

coffeemaker

Iron
Registered Member
#1
Hello.

I'm new to machining. I want to make a stainless steel version of the Aeropress coffee maker (actually just the two parts on the left):
aeropress-3.jpg

Here are images of my desgin (happy to supply the actual files if needed):
Aero key v6.png Aero lid v8.png
I plan to weld the part of the left to a 5" long 2.5" diameter tube of stainless steel.

I have access to Tormach CNC Mill. Which I think is a lightweight machine but that's just what I've been told.

I've been researching the different types of stainless steel and found 303, 304, and 316. From what I've read, 304 is the hardest to machine so I can cross that off the list. 303 is the easiest but is difficult to weld which is how I was planning on attaching the left part to the tube. That leaves 316 which I've read is a little easier than 304.

My question is, how difficult is it to machine may parts out of stainless steel and is it out of the question for a newbie to be able to do with a Tormach CNC Mill?
 

Attachments

aliva

Active User
H-M Supporter-Premium
#2
Stainless steel has a tendency to work harden. Keep your speeds and feeds with in the recommended range and use plenty of coolant.
The parts look pretty thin, I would recommend TIG welding if you have access to one
 

Wreck™Wreck

Active User
H-M Supporter-Premium
#3
You will almost certainly have to make the part big then machine after welding, a part with such a thin section is going to walk a good deal.
 

coffeemaker

Iron
Registered Member
#5
Stainless steel has a tendency to work harden. Keep your speeds and feeds with in the recommended range and use plenty of coolant.
The parts look pretty thin, I would recommend TIG welding if you have access to one
I have access to a tig welder although I've never used it. I'll give it a shot. Thanks for the tip.

I can make it thicker. It's currently 0.12" thick (for no particular reason). What's a good minimum thickness for welding?

Do you know where I can find the recommended speed and feed range for 316?
 

coffeemaker

Iron
Registered Member
#6
You will almost certainly have to make the part big then machine after welding, a part with such a thin section is going to walk a good deal.
I can make it thicker. What's a good thickness? The tube comes with a wall thickness of 0.12" and so I made the part the same thickness...
 

coffeemaker

Iron
Registered Member
#7
Aeropress. Best cup I ever had and I'm a coffee snob.
Hahaha. Me too! I keep needing to get new chamber pieces because they warp/melt over time from the hot water. That's why I had the idea to make it out of stainless steel. Stainless steel Aeropress would be sweet, right!
 

Wreck™Wreck

Active User
H-M Supporter-Premium
#9
I can make it thicker. What's a good thickness? The tube comes with a wall thickness of 0.12" and so I made the part the same thickness...
The tube will likely be fine, the flat part will cause problems if it needs to retain its shape to function, I would leave .05" or more on each side for finish machining after welding, I do not know the part dimensions or welding process planned therefore am guessing from a good deal of experience however..

Good Luck
 

coffeemaker

Iron
Registered Member
#10
The tube will likely be fine, the flat part will cause problems if it needs to retain its shape to function, I would leave .05" or more on each side for finish machining after welding, I do not know the part dimensions or welding process planned therefore am guessing from a good deal of experience however..

Good Luck
Can you think of a better way to attach the thin piece to the tube, even if it's a major design change?
 

terrywerm

New Member Liaison
Staff member
H-M Supporter-Premium
#11
Being a guy that has machined and welded a lot of 316 SS, be ready for a learning curve. Make sure you purge the inside of that tube with argon before you weld the outer circumference or else it will probably get really ugly on the inside. Make sure you practice TIG a bunch before you weld your part.

Keep in mind that I am not trying to scare you off, but I am encouraging you to exercise some due diligence before you start on your finished part. Practice WILL pay off. Keep in mind that TIG welding thin stainless tends to make the stainless warp into what almost appear to be totally new shapes from what you started with. The flat disc at the bottom will likely need to be kept flat, so be sure to weld the two pieces together before you take your finishing cuts.
 

coffeemaker

Iron
Registered Member
#12
Being a guy that has machined and welded a lot of 316 SS, be ready for a learning curve. Make sure you purge the inside of that tube with argon before you weld the outer circumference or else it will probably get really ugly on the inside. Make sure you practice TIG a bunch before you weld your part.

Keep in mind that I am not trying to scare you off, but I am encouraging you to exercise some due diligence before you start on your finished part. Practice WILL pay off. Keep in mind that TIG welding thin stainless tends to make the stainless warp into what almost appear to be totally new shapes from what you started with. The flat disc at the bottom will likely need to be kept flat, so be sure to weld the two pieces together before you take your finishing cuts.
If I made the flat disc 0.25" or 0.5" thick where it contacts the tube, would it still warp? I want to make this as easy as possible and would rather make my finishing cuts before welding if possible. Thanks for the advise!
 

terrywerm

New Member Liaison
Staff member
H-M Supporter-Premium
#13
You would probably be okay at .250" as long as you don't get the heat too high. With some experience, you could probably go down to about .180 or .200 and be okay, but being new to this, you might want to stick to a little bit thicker.
 

coffeemaker

Iron
Registered Member
#14
You would probably be okay at .250" as long as you don't get the heat too high. With some experience, you could probably go down to about .180 or .200 and be okay, but being new to this, you might want to stick to a little bit thicker.
I'll add more material then, thanks.

Any suggestions on what cutters to use when milling?
 

dave_r_1

Active Member
Active Member
#16
You might also consider a solution where the pieces screw together, so the screen is held in place by a "nut" that screws onto the bottom and presses it against the tube...assumes you have a lathe that does threading... This might aid in cleaning it later as well.
 

Wreck™Wreck

Active User
H-M Supporter-Premium
#17
Can you think of a better way to attach the thin piece to the tube, even if it's a major design change?
Not without knowing what it does nor the loads it may need to withstand. The manufacturing method would be dependent on the number of parts required, if you are a hobbyist making only a handful and have no deadline just rough the parts, weld them then finish machine after welding.

If thousands of parts per month are required with a strict time constraint injection molded plastic is the answer the original manufacturer came to. Also Electron Beam welding creates far less distortion.
 
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terrywerm

New Member Liaison
Staff member
H-M Supporter-Premium
#18
For some reason I lost track of this thread for a while. When working with stainless, especially 316, I stuck with carbide cutters almost without question. HSS will work, but resharpening frequently will become the new normal. Make sure to use lots of coolant no matter what you use for a cutter.

I also like dave_r_1's idea of threading the bottom disk onto the tube. No warpage to worry about if you do it that way. You might have to make the bottom end of the tube a little thicker for that to work, or you could just use a very fine thread so that the root of the thread does not get so deep in the tube itself.