C360 Brass- Warped like crazy

Need some help.

A customer ordered C360 to replace some parts that were originally bronze. The print calls +0/-.002 and I charged accordingly. Unfortunately I don't usually work with brass and didn't know it warps if machined heavily on one side :-/

Material came .625" x 1.75" x 6.25". Final dimensions are .495" x 1.625" x 6.109". I faced .01" off one side with a flycutter (beautiful finish), flipped and roughed to +.01 using .030" DOC with carbide insets on a small 90° face mill. Then finished all 33 parts with a flycutter without moving Z. I was happy to hit all 33 within .0004" under the .495". Way higher tolerances than I'm used to.

Went in this morning to find all the parts warped like crazy. I can slide .014" feeler under the center of some, others are only .003" out. WTF. I then found a few threads saying its the internal stress from rolling causing the work to warp if not cut evenly on each side. SOB. Funny that never showed up on the 30 or so threads I read looking up tips/feeds/tooling info.

HERE IS MY REAL QUESTION: (2 actually)

I tried bending it back on the vise using 2 points of contact on the ends of the concaved side and one in the convex side. Seems I can bend them back close and face a few thou off each side after getting okay from customer. Before calling him I want your input. The part Is essentially a gib and is going to fail at its intended purpose anyways... bronze ones wore out so he is trying brass... looks like I'll be running the parts regularly... or changing to bronze next time. lol Any thing to worry about bending it back and having? quick test reduced the convex to .003" but its warped out of square the other way too so I'm thinking .005" on each side should get them back to perpendicular to the other edges.

SECOND QUESTION-

I need to slot .125" deep at .75" wide the while length and drill and tap 2x 3/8/16 along the center. Well this slot cause more warping? should I use a smaller EM? HSS instead of carbide? I was planning on using Data Flute ARF20500 2fl carbide .5".

I also am now questioning the 60.5° angles along the length (fits to a dovetail). If it warped when I carefully cut .125"... what the heck is gonna happen when I shave of a large chunk off at an angle along the part?


I really don't want to pay for all this brass... not do I want to spend hours straightening the parts out if they are going to warp later. little frustrated... appreciate any help.

Maybe anneal it now and take the stresses from cold rolling out? It will be a lot less likely to warp but likely to wear out sooner. I think a lot of bronze gibs are annealed before machining, but they wear a lot better. Just a guess.

Take the bars home and put them in the oven @500*. After a couple of hours turn off the oven and let it cool. That should take about 80% of the "Boing" out of it.

Brass bar is pulled through a die. The process stretches the outside skin tight and the inside part of the bar doesn't feel it as much. So when you clean off one side, the other side can shrink and bend the bar. I found the bars losing about .001" per inch in length when both sides were cut.

Regards,

Stan-

Metalcutter said:

Take the bars home and put them in the oven @500*. After a couple of hours turn off the oven and let it cool. That should take about 80% of the "Boing" out of it.

Brass bar is pulled through a die. The process stretches the outside skin tight and the inside part of the bar doesn't feel it as much. So when you clean off one side, the other side can shrink and bend the bar. I found the bars losing about .001" per inch in length when both sides were cut.

Regards,

Stan-

Click to expand...

Thanks for the info so far guys.

I have a Powder Coating oven that can fit them all at once so that is easy.

I played with bending a few tonight and got them within .002" of flat pretty easily. I don't know if they will spring back yet.

Should I bend then all back, heat (semi-annealing?), then finish machining? Or heat, bend, then machine? Seems like using the springiness will help it bend "flatter" than bending after heating.

Seems like straighten, heat, take .003ish off each side should get them square and prevent accumulated error when machining the angeles. The jig holds a large side and locates off the side, flip then locates off the other side. So
if the sides aren't square to the bottom the two angles won't be in the correct plane to each other.

Just for anyone searching on this later:
I used heavy magnets to hold .125" steel shims against a 1.625" x .5" parallel against the back vice jaw and set so the part only hung .125" over each shim. Then put the dti between the part and parallel. Put a .5" ground pin vertically between the moving jaw and the part so I could measure the actual deflection.

I bent .030" past square (.04" total on one .01 warped).

Any thoughts on hardening it back with only 500°? Heat several hours then oil? Would that discolor the brass?

Quick google search yielded this

The process of hardening and annealing brass is exactly the reverse of that used with steel. Brass is hardened when it is heated and allowed to cool slowly ; it is softened or annealed when heated and cooled suddenly. When annealing brass, care should be taken that it is evenly heated throughout and that it is evenly cooled

So slow cooling from 500° would harden them which removes some "boing".

PriddyShiddy said:

Quick google search yielded this

The process of hardening and annealing brass is exactly the reverse of that used with steel. Brass is hardened when it is heated and allowed to cool slowly ; it is softened or annealed when heated and cooled suddenly. When annealing brass, care should be taken that it is evenly heated throughout and that it is evenly cooled

So slow cooling from 500° would harden them which removes some "boing".

Click to expand...

Actually only some certain alloys of brass can be heat hardened. Heating c360 to 500F and letting it cool would stress relieve it, which is just what you want here.

brass

i have has metals warp than were not annealed and each and every time they were machined they warped some more. yes i have bent them back straighter but sometimes they bend some more after a few days or weeks especially if exposed to different temperatures.
.
link on brass annealing and stress relieving.
http://www.pearson-studium.de/books/3827370597/cd01/Articles/ASM/C36000.pdf
.
i always thought to anneal heat to a dull red but you are correct that stress relieving can be done in a oven at 550 F degrees

DMF_TomB said:

i have has metals warp than were not annealed and each and every time they were machined they warped some more. yes i have bent them back straighter but sometimes they bend some more after a few days or weeks especially if exposed to different temperatures.
.
link on brass annealing and stress relieving.
http://www.pearson-studium.de/books/3827370597/cd01/Articles/ASM/C36000.pdf
.
i always thought to anneal heat to a dull red but you are correct that stress relieving can be done in a oven at 550 F degrees

Click to expand...

THANK YOU! Excellent data. Knew this was the place to ask.

Metalcutter- his data put your suggestion spot in down to the degree. Impressive. Thank you both very much.

TomB - Thats some great info. Do you have a link to a page with other materials our was that a google search? Tried the domain top level by I guess living in Frankfurt for a year when I was 8 wasn't enough to be able to navigate that site. Would love to save a few more pdf's on my phone for quick reference.

Checked the pieces I bent last night this morning and they seem the same as when I went to bed, so I'll bend them all then stress relieve. I'll make sure I post findings after machining for archival purposes.

Really appreciate the Sunday night support gentleman.

The reason my temp was selected is I was frustrated with the "Boing," and that was the highest temperature my apartment oven could do. It was just a thought at the time, and I got lucky.

I find it really helps to have wider understanding of how to "Work" the materials we machine. There are some really cool tricks out there...

Regards,

Stan-

google

PriddyShiddy said:

TomB - Thats some great info. Do you have a link to a page with other materials our was that a google search? Tried the domain top level by I guess living in Frankfurt for a year when I was 8 wasn't enough to be able to navigate that site. Would love to save a few more pdf's on my phone for quick reference.

Click to expand...

just a google search, annealing c360 brass,

although metal suppliers or manufacturers typically have information on the metals they sell