Any suggestions on cutting small and thin parts from 304

[Mtndew]

Mill the entire part leaving small tabs in a couple of areas, then make the tabs thinner to easily snap the part off.
File or sand the remains.
Profit.

 

[implmex]

Hi Mtndew:
My experience with tabbing parts:
When you have milled features on both sides it is a super valuable way to get there, because it relieves you of the burden of having to fixture some weirdass shape for the side 2 ops and find a way to pick up your new WCS.

But it's very slow and it's also super wasteful of material.
You need to plan for stock that's big enough for your profiling cutter plus the stock you need to leave as a frame around the part.
If you're thicknessing it only locally, you have to nibble out your facing cuts with little cutters...kinda like milling a pocket.
Then you can profile your part...again with skinny fragile cutters, leaving whatever tabs you need to stabilize the part.

After you cut it from the tabs, it's still going to sproing into a banana shape, and now you have tabs to trim as well as a nasty debur to do in order to make the tab remnants go away.
If you laser cut them from 10 gauge sheet, you get net shape parts in one operation that you don't need to do anything further to, except maybe tumble them if you want to debur them before the customer gets them.

Laser cutting is such an obvious way to make these, that if the customer squawks about it, I'd politely (or maybe not so politely) invite him to go away and stop bothering me.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

 

[joecrs]

So maybe i can get some advice on a better way to get my desired results.

The finished parts measure about 2.375 long by .375 wide and .135 thick. They will be the handles for minature knives.
The original plan was to get a 2.5"x6'x.1875 piece of 304 stainless, cut it into 6.5" strips then deck them to thickness, drill and countersink some holes and then place them on a fixture to cut out the individual handles.
Well I was able to make my fixture plate and all was good until I started trying to deck the 304. I think part of my problem might be related to the tooling i have at hand. I planned to use a 2" shell mill with apkt inserts to remove about .02 and then come in with a flycutter and make a single .005 finish pass. Flip and repeat until they were at final thickness.

I ordered some inserts that would work better in stainless than what i had on hand and Im happy to say I was able to get an acceptable surface finish and good sounding cut out of the shell mill. The fly cutter hasnt worked quite so well though. I havent been able to get anything close to the results im looking for. Either the finish isnt good enough or it starts out great then goes to hell cause the insert chipped midway through. I have tried a range of feeds and speeds, cut with and without coolant and, tried a few different depths of cut Inserts might be the issue as they are tpg inserts held in generic 3/8 amazon lathe holders. Not ideal by any measure but its what I have on hand.

The other issue is that on the one i was able to get a good finish curled like a potato chip when removed from the vise. So any suggestions to deal with that would be helpful as well. I saw something about normalizing the material before working it but didnt read into the process all that much. The other trick seems to be taking small cuts from each side trying to balance the twist out as you go. That seems tricky considering the work hardening and lack of material to be removed. If thats my only option it is what it is but if normalizing or another process would work as well or better that would be preffered.

I do have a 45 degree face mill large enough to make a single pass with stainless specific inserts on order based on suggestions from other posts regarding cutting 304. Im really hoping the new cutter solves most of the issues but with the pessimistic assumption it wont is there anything you guys can suggest that might improve my results with the fly cutter at hand. Perhaps a different holder and insert combo, a better depth of cut and feed/speed combo to avoid work hardening.

I'm open to other processes or material suggestions as well. I had considered either 303 or 430 and my client is open to that idea but im wondering if id still have the same parts curling up issues with those that im having with the 304. I also suggested having the handle shapes cut over sized on a waterjet or laser and then do the 3d profiling in the mill, the client wasnt so keen on that and admittedly i dont have enough experience with stainless much less small stainless parts to argue. But if someone with more experience says hey thats actually a better way to do things that would help me change his mind.

My question would be if you are making a knife you actually want to cut something with why 303 or 304 stainless those are not great choices for knife material at all they will not hold an edge.

 

[plastikdreams]

Hi Mtndew:
My experience with tabbing parts:
When you have milled features on both sides it is a super valuable way to get there, because it relieves you of the burden of having to fixture some weirdass shape for the side 2 ops and find a way to pick up your new WCS.

But it's very slow and it's also super wasteful of material.
You need to plan for stock that's big enough for your profiling cutter plus the stock you need to leave as a frame around the part.
If you're thicknessing it only locally, you have to nibble out your facing cuts with little cutters...kinda like milling a pocket.
Then you can profile your part...again with skinny fragile cutters, leaving whatever tabs you need to stabilize the part.

After you cut it from the tabs, it's still going to sproing into a banana shape, and now you have tabs to trim as well as a nasty debur to do in order to make the tab remnants go away.
If you laser cut them from 10 gauge sheet, you get net shape parts in one operation that you don't need to do anything further to, except maybe tumble them if you want to debur them before the customer gets them.

Laser cutting is such an obvious way to make these, that if the customer squawks about it, I'd politely (or maybe not so politely) invite him to go away and stop bothering me.

Cheers

Marcus
www.implant-mechanix.com
www.vancouverwireedm.com

When I tab stuff on the wire I usually only leave 20k or so if it's thick enough I usually only need one I usually don't tab though, I prefer a profile then a single cut off.

 

[Garwood]

Double disc grinding is often an in-house process. The machines can be millions of dollars and are built for a specific part or family of parts. I am not familiar with grind shops that will double disc grind 500 parts. Maybe it's not a big deal, but I'd be surprised if it was affordable at that scale.

Blanchard grinding is almost as fast, but much easier to setup and get running. And Blanchards are a low cost machine that's cheap to operate.

Yes, you can Blanchard grind non-magnetic stainless.

 

[Rob F.]

On a need to know basis, does he need to know you are getting them waterjet cut?

That is kind of what I was thinking as I read this. The part is made to a print, who really cares how the part gets to match the print as long as it does... Milling entirely out of thicker stock just sounds silly to me.
Get the parts cut and ground as efficiently as possible, do what ever work you do to finish them and show it to him, will he reject it?
If he knows nothing about manufacturing and is trying to direct how the part is manufactured... isnt there something wrong here?

 

[D Nelson]

So maybe i can get some advice on a better way to get my desired results.

The finished parts measure about 2.375 long by .375 wide and .135 thick. They will be the handles for minature knives.
The original plan was to get a 2.5"x6'x.1875 piece of 304 stainless, cut it into 6.5" strips then deck them to thickness, drill and countersink some holes and then place them on a fixture to cut out the individual handles.
Well I was able to make my fixture plate and all was good until I started trying to deck the 304. I think part of my problem might be related to the tooling i have at hand. I planned to use a 2" shell mill with apkt inserts to remove about .02 and then come in with a flycutter and make a single .005 finish pass. Flip and repeat until they were at final thickness.

I ordered some inserts that would work better in stainless than what i had on hand and Im happy to say I was able to get an acceptable surface finish and good sounding cut out of the shell mill. The fly cutter hasnt worked quite so well though. I havent been able to get anything close to the results im looking for. Either the finish isnt good enough or it starts out great then goes to hell cause the insert chipped midway through. I have tried a range of feeds and speeds, cut with and without coolant and, tried a few different depths of cut Inserts might be the issue as they are tpg inserts held in generic 3/8 amazon lathe holders. Not ideal by any measure but its what I have on hand.

The other issue is that on the one i was able to get a good finish curled like a potato chip when removed from the vise. So any suggestions to deal with that would be helpful as well. I saw something about normalizing the material before working it but didnt read into the process all that much. The other trick seems to be taking small cuts from each side trying to balance the twist out as you go. That seems tricky considering the work hardening and lack of material to be removed. If thats my only option it is what it is but if normalizing or another process would work as well or better that would be preffered.

I do have a 45 degree face mill large enough to make a single pass with stainless specific inserts on order based on suggestions from other posts regarding cutting 304. Im really hoping the new cutter solves most of the issues but with the pessimistic assumption it wont is there anything you guys can suggest that might improve my results with the fly cutter at hand. Perhaps a different holder and insert combo, a better depth of cut and feed/speed combo to avoid work hardening.

I'm open to other processes or material suggestions as well. I had considered either 303 or 430 and my client is open to that idea but im wondering if id still have the same parts curling up issues with those that im having with the 304. I also suggested having the handle shapes cut over sized on a waterjet or laser and then do the 3d profiling in the mill, the client wasnt so keen on that and admittedly i dont have enough experience with stainless much less small stainless parts to argue. But if someone with more experience says hey thats actually a better way to do things that would help me change his mind.

Take all but one insert out of the face mill and use it as your fly cutter
Don