Anyone have any tips on machining 17-4 prior to hardening, other than sharp carbide and dark oil with Moly-D? How much will this change dimensionally when hardened? I'll be using the 900degrees/60 minutes with stainless wrap method.
Gunsmithing Machining 17-4
- Thread starter zenbiker
- Start date
Re: Machining 17-4
I've worked with it quite a bit. out of all the SS's 17-4 and 15-5 are my two favorite.
It'll work harden if you look at it cross eyed. If tapping any holes make sure that tap is sharp and use the Moly D (best chit in the world!)
If you can, get the solution annealed H1150 stuff. It's pre hard and cuts much, much nicer than "raw" 17-4. It'll actually make a chip (little razors so be careful!) instead of stuff that looks like bubble gum.
Keep the speeds conservative and you'll be fine.
If you can, use coolant instead of oil. It's not terribly abrasive, you just want to make sure it doesn't get hot.
It'll also stress releive in the "raw" state pretty easily. If your for instance shell milling a piece of bar stock start oversize and cut back and forth (flip sides) as it'll want to banana on you. If it's a thin piece, don't beat it flat in the vise as it'll just bow up like a cat's back when you pet it the moment you release the jaws.
If using the bottom of the endmill roll a small radius on the corners of your tool using a diamond lap. You'll get a better finish.
As for heat treating:
It's an air hardening stainless so your biggest challenge is to keep a circulation of air around it during quenching. if your part is cylindrical in shape you want to suspend it in the oven. Don't let it touch the fire brick if you can and DON'T lay it on it's side. You'll have a banana!
It generally doesn't move around all that much, but it will move a skosh more than 15-5. This is where the H1150 solution annealed stuff is really nice as it's already heat treated to around 35HRC. If your tools are sharp you can just machine the part and be done with it. (assuming you don't need more hardness/tensile strength.)
Also, 17-4 and 15-5 are both precipitating hardening SS so it actually gets tougher/harder with age. How much I don't know, but it does.
Hope this helped and good luck!
Chad
I've worked with it quite a bit. out of all the SS's 17-4 and 15-5 are my two favorite.
It'll work harden if you look at it cross eyed. If tapping any holes make sure that tap is sharp and use the Moly D (best chit in the world!)
If you can, get the solution annealed H1150 stuff. It's pre hard and cuts much, much nicer than "raw" 17-4. It'll actually make a chip (little razors so be careful!) instead of stuff that looks like bubble gum.
Keep the speeds conservative and you'll be fine.
If you can, use coolant instead of oil. It's not terribly abrasive, you just want to make sure it doesn't get hot.
It'll also stress releive in the "raw" state pretty easily. If your for instance shell milling a piece of bar stock start oversize and cut back and forth (flip sides) as it'll want to banana on you. If it's a thin piece, don't beat it flat in the vise as it'll just bow up like a cat's back when you pet it the moment you release the jaws.
If using the bottom of the endmill roll a small radius on the corners of your tool using a diamond lap. You'll get a better finish.
As for heat treating:
It's an air hardening stainless so your biggest challenge is to keep a circulation of air around it during quenching. if your part is cylindrical in shape you want to suspend it in the oven. Don't let it touch the fire brick if you can and DON'T lay it on it's side. You'll have a banana!
It generally doesn't move around all that much, but it will move a skosh more than 15-5. This is where the H1150 solution annealed stuff is really nice as it's already heat treated to around 35HRC. If your tools are sharp you can just machine the part and be done with it. (assuming you don't need more hardness/tensile strength.)
Also, 17-4 and 15-5 are both precipitating hardening SS so it actually gets tougher/harder with age. How much I don't know, but it does.
Hope this helped and good luck!
Chad
Re: Machining 17-4
Yeah, Chad, thanks, that does help a lot. This is my first foray in to 17-4 and I'm sure to put in a few classes at the school of hard knocks. I needed a corrosion resistant hard alloy that could be used wihout anodizing, parkerizing, or other surface coating, so I decided 17-4. I won't be making any actions yet, just small pieces like blast baffles, muzzle brakes, and thread adapters for suppressors. The blast baffles are going to take the hardest beating in use, and while Inconel is easier to work, I decided this si the time to start using 17-4. Is it necessary to wrap it in stainless foil when heat treating? Thats going to be the only way I can keep the metal directly off the ceramic.
Yeah, Chad, thanks, that does help a lot. This is my first foray in to 17-4 and I'm sure to put in a few classes at the school of hard knocks. I needed a corrosion resistant hard alloy that could be used wihout anodizing, parkerizing, or other surface coating, so I decided 17-4. I won't be making any actions yet, just small pieces like blast baffles, muzzle brakes, and thread adapters for suppressors. The blast baffles are going to take the hardest beating in use, and while Inconel is easier to work, I decided this si the time to start using 17-4. Is it necessary to wrap it in stainless foil when heat treating? Thats going to be the only way I can keep the metal directly off the ceramic.
Re: Machining 17-4
When at Nesika we didn't worry about wrapping the actions for heat treat. Now they were/are made from 15-5 ph but the two (15/17) are essentially inbreeding cousins so I don't think it'll matter much.
900 degrees really isn't that hot compared to other material requirements so I don't think you'll have to overly concerned with oxygen making a mess of things. Maybe try flooding your oven with an inert gas like argon or something before you fire it up. Might be worth a try. (dunno)
When at Nesika we didn't worry about wrapping the actions for heat treat. Now they were/are made from 15-5 ph but the two (15/17) are essentially inbreeding cousins so I don't think it'll matter much.
900 degrees really isn't that hot compared to other material requirements so I don't think you'll have to overly concerned with oxygen making a mess of things. Maybe try flooding your oven with an inert gas like argon or something before you fire it up. Might be worth a try. (dunno)
Re: Machining 17-4
When you air quench it DO NOT flow air over it. It should sit in quiescent (still/calm) air. I've seen a lot of people tell someone to blow a fan on a part to help quench it. This causes differential cooling on one side vs the other and rarely results in a straight part. It always results in one side being harder than the other and imparting internal stresses that show up as material is removed.
Other than that, I don't have anything to add, Mr. Dixon has covered it very well.
ETA: If you need to speed the rate for a harder/stronger part then multiple fans or airlines situated around the part for quench is OK. Do not just use 1 and try to move it around or let it sit and blow at a stationary point.
When you air quench it DO NOT flow air over it. It should sit in quiescent (still/calm) air. I've seen a lot of people tell someone to blow a fan on a part to help quench it. This causes differential cooling on one side vs the other and rarely results in a straight part. It always results in one side being harder than the other and imparting internal stresses that show up as material is removed.
Other than that, I don't have anything to add, Mr. Dixon has covered it very well.
ETA: If you need to speed the rate for a harder/stronger part then multiple fans or airlines situated around the part for quench is OK. Do not just use 1 and try to move it around or let it sit and blow at a stationary point.
Re: Machining 17-4
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body">When you air quench it DO NOT flow air over it. It should sit in quiescent (still/calm) air. I've seen a lot of people tell someone to blow a fan on a part to help quench it. This causes differential cooling on one side vs the other and rarely results in a straight part. It always results in one side being harder than the other and imparting internal stresses that show up as material is removed.
Other than that, I don't have anything to add, Mr. Dixon has covered it very well.
ETA: If you need to speed the rate for a harder/stronger part then multiple fans or airlines situated around the part for quench is OK. Do not just use 1 and try to move it around or let it sit and blow at a stationary point. </div></div>
Noted:
I should have been a little more specific when I mentioned "air stream". He's absolutely correct. A fan is a horrible idea.
Thanks for the clarification.
C
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: bohem</div><div class="ubbcode-body">When you air quench it DO NOT flow air over it. It should sit in quiescent (still/calm) air. I've seen a lot of people tell someone to blow a fan on a part to help quench it. This causes differential cooling on one side vs the other and rarely results in a straight part. It always results in one side being harder than the other and imparting internal stresses that show up as material is removed.
Other than that, I don't have anything to add, Mr. Dixon has covered it very well.
ETA: If you need to speed the rate for a harder/stronger part then multiple fans or airlines situated around the part for quench is OK. Do not just use 1 and try to move it around or let it sit and blow at a stationary point. </div></div>
Noted:
I should have been a little more specific when I mentioned "air stream". He's absolutely correct. A fan is a horrible idea.
Thanks for the clarification.
C
Re: Machining 17-4
Thanks everyone. I'm going to try stainless wrap and let the piece cool passively without any fans or such to start and see how it goes. In fact I may just turn the oven off after an hour and let the whole thing cool without opening it up.
Thanks everyone. I'm going to try stainless wrap and let the piece cool passively without any fans or such to start and see how it goes. In fact I may just turn the oven off after an hour and let the whole thing cool without opening it up.
Re: Machining 17-4
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1ZNUF</div><div class="ubbcode-body">Thanks everyone. I'm going to try stainless wrap and let the piece cool passively without any fans or such to start and see how it goes. In fact I may just turn the oven off after an hour and let the whole thing cool without opening it up. </div></div>
Cooling rate is very important for how a quench hardening material behaves. If you let it sit in the oven for a while and cool slowly it will be more ductile, softer, and higher elongation to failure IN GENERAL.
Air Cooling materials have specific behavior and curves that need to be accounted for just like any other material. Oil quench, water quench, post-quench normalizing, etc.
Do some internet searching on the material properties that you NEED and then tailor your heat treat process to what you NEED. Don't just DO something.
Try looking here for starters:
www.matweb.com
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: 1ZNUF</div><div class="ubbcode-body">Thanks everyone. I'm going to try stainless wrap and let the piece cool passively without any fans or such to start and see how it goes. In fact I may just turn the oven off after an hour and let the whole thing cool without opening it up. </div></div>
Cooling rate is very important for how a quench hardening material behaves. If you let it sit in the oven for a while and cool slowly it will be more ductile, softer, and higher elongation to failure IN GENERAL.
Air Cooling materials have specific behavior and curves that need to be accounted for just like any other material. Oil quench, water quench, post-quench normalizing, etc.
Do some internet searching on the material properties that you NEED and then tailor your heat treat process to what you NEED. Don't just DO something.
Try looking here for starters:
www.matweb.com
Re: Machining 17-4
The company I work for machines & heat treat2 17-4 everyday. At H900 (900 degrees F for 1 hour minimum) the material will shrink 0.0005" inch/inch. In other words, if you started with a 1.000" square block, after the H900 heat treat, it will be very close to 0.9995" square. This material also is very easy to work harden. Be sure to use sharp tooling and a lot of coolant. We only use carbide now days. It holds up much better. Many people use to wrap heat treated parts with stainless steel foil & include a small piece of paper. The idea was that the paper would burn & remove all the oxygen in the sealed space made from the foil. We do not use this method. Most of our items are sandblasted at a later date. At times we do machine after heat treat. At H900, 17-4 is roughly Rockwell 43 on the C scale at has a yield strength 180ksi.
I have never seen parts distort from air being forced over them while cooling. Most of the time, the material will distort from internal stresses being relieved during heat treat process. If the material was Condition A then machined, dull tools or improper machining could cause internal stress. We've found the round, forged barstock has less internal stress than plate or square stock.
Make sure while heat treating that the part is at 900 degrees for atleast an hour. If you left it in longer, it will not effect the heat treat (up to several hours). Be sure to removed the part from the oven after the time is up. This is very important.
If you have questions, please feel free to email.
Paul
The company I work for machines & heat treat2 17-4 everyday. At H900 (900 degrees F for 1 hour minimum) the material will shrink 0.0005" inch/inch. In other words, if you started with a 1.000" square block, after the H900 heat treat, it will be very close to 0.9995" square. This material also is very easy to work harden. Be sure to use sharp tooling and a lot of coolant. We only use carbide now days. It holds up much better. Many people use to wrap heat treated parts with stainless steel foil & include a small piece of paper. The idea was that the paper would burn & remove all the oxygen in the sealed space made from the foil. We do not use this method. Most of our items are sandblasted at a later date. At times we do machine after heat treat. At H900, 17-4 is roughly Rockwell 43 on the C scale at has a yield strength 180ksi.
I have never seen parts distort from air being forced over them while cooling. Most of the time, the material will distort from internal stresses being relieved during heat treat process. If the material was Condition A then machined, dull tools or improper machining could cause internal stress. We've found the round, forged barstock has less internal stress than plate or square stock.
Make sure while heat treating that the part is at 900 degrees for atleast an hour. If you left it in longer, it will not effect the heat treat (up to several hours). Be sure to removed the part from the oven after the time is up. This is very important.
If you have questions, please feel free to email.
Paul
Re: Machining 17-4
17-4ph is a great choice for the applications you mention. I've done blast baffles and muzzle brakes/mounts from both Inconel and 17-4 and I definitely liked the results from working with 17-4 much better. I think it's much nicer to weld also. I wrap parts in SS foil, cook at 900/1hr and then let cool in the foil outside the oven. I then abrasive blast before welding. Blast baffles last a long-time, very resistant to erossion. Don't know why it isn't more popular material? I'm sure you will be very happy with the life of baffles/brakes made from 17-4.
17-4ph is a great choice for the applications you mention. I've done blast baffles and muzzle brakes/mounts from both Inconel and 17-4 and I definitely liked the results from working with 17-4 much better. I think it's much nicer to weld also. I wrap parts in SS foil, cook at 900/1hr and then let cool in the foil outside the oven. I then abrasive blast before welding. Blast baffles last a long-time, very resistant to erossion. Don't know why it isn't more popular material? I'm sure you will be very happy with the life of baffles/brakes made from 17-4.
Re: Machining 17-4
As others mentioned, it is great for compensators, blast baffles, or anything else which requires a strong & erosion resistant material. I've made a lot of comps from 17-4. Beware that 17-4 is prone to galling. If you thread 2 parts together made from it, be sure to use locktite or antisieze. If not, you may never get it apart again.
Keep in mind that the oxidation has to be removed either by blasting, sanding, or by pickling. The oxidation will rust.
This material is very popular in aerospace, medical, and transducer design companies (like ours).
Paul
As others mentioned, it is great for compensators, blast baffles, or anything else which requires a strong & erosion resistant material. I've made a lot of comps from 17-4. Beware that 17-4 is prone to galling. If you thread 2 parts together made from it, be sure to use locktite or antisieze. If not, you may never get it apart again.
Keep in mind that the oxidation has to be removed either by blasting, sanding, or by pickling. The oxidation will rust.
This material is very popular in aerospace, medical, and transducer design companies (like ours).
Paul
Re: Machining 17-4
Thanks to everyone for the heads-up on taking the piece out of the oven to cool, and for the website mentioned. I'll be doing some more home work before starting anything; the tooling and material is not cheap, not to mention the time invested, which ends up being even more valuable. I'm not doing this for a living but one machinist told me one botched job ate up the profits for nine others, so make sure you know what you're doing before you do it. As it is, I have precious little time to devote to whatever project I'm doing, so a screwup sets me back until my next window of opportunity opens.
Thanks to everyone for the heads-up on taking the piece out of the oven to cool, and for the website mentioned. I'll be doing some more home work before starting anything; the tooling and material is not cheap, not to mention the time invested, which ends up being even more valuable. I'm not doing this for a living but one machinist told me one botched job ate up the profits for nine others, so make sure you know what you're doing before you do it. As it is, I have precious little time to devote to whatever project I'm doing, so a screwup sets me back until my next window of opportunity opens.
Re: Machining 17-4
Chad,
Did you find 17-4 or 15-5 from one vendor might not machine the same as the next? Went thru that horror on gundrilling ops, got the tool geometry and sfm figured out for the one batch or lot, they went and ordered a 'cheaper' 17-4 for the next run, same certs and spec, different vendor, and could not drill a hole making more than one chip. Spent over a week regrinding the tool geometry to make it work..Night-mare..Squidgy shit anyway.
JR
Chad,
Did you find 17-4 or 15-5 from one vendor might not machine the same as the next? Went thru that horror on gundrilling ops, got the tool geometry and sfm figured out for the one batch or lot, they went and ordered a 'cheaper' 17-4 for the next run, same certs and spec, different vendor, and could not drill a hole making more than one chip. Spent over a week regrinding the tool geometry to make it work..Night-mare..Squidgy shit anyway.
JR
Re: Machining 17-4
JR, we don't have much problem with the metal behaving differently from batch to batch. I buy the stock in 12' bars. Over the course of year, I purchase hundreds of bars from 0.5" to 12" diameter. Could be that the metal wasn't properly solution annealed. One thing, 15-5 is more difficult to machine.
We did have a vendor give us 15-5 instead of 17-4. That won't happen again!
If you have question, please let me know.
Paul
JR, we don't have much problem with the metal behaving differently from batch to batch. I buy the stock in 12' bars. Over the course of year, I purchase hundreds of bars from 0.5" to 12" diameter. Could be that the metal wasn't properly solution annealed. One thing, 15-5 is more difficult to machine.
We did have a vendor give us 15-5 instead of 17-4. That won't happen again!
If you have question, please let me know.
Paul
Re: Machining 17-4
Cheers Paul, that episode was about 10years and a purchasing agent ago..I like the cartech stainless, she went with something else..Have since learned from that exercise..Stick to what you know. ha..
Cheers Paul, that episode was about 10years and a purchasing agent ago..I like the cartech stainless, she went with something else..Have since learned from that exercise..Stick to what you know. ha..
Re: Machining 17-4
Carpenter developed 17-4 a long time ago and had the patent on what was called custom 630. Seems like everyone is making it now. Carpenter has what they call Project 70 -17-4 which is suppose to machine better. Not sure if it is worth the extra money. We've tried it in the past, not much difference.
Paul
Carpenter developed 17-4 a long time ago and had the patent on what was called custom 630. Seems like everyone is making it now. Carpenter has what they call Project 70 -17-4 which is suppose to machine better. Not sure if it is worth the extra money. We've tried it in the past, not much difference.
Paul
