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How bad does bronze strips warp when you machine it.

jackal

Titanium
Joined
May 4, 2006
Location
northwest ARK
I have machined a lot of bronze bushings in the past, but this is a new one for me.

My customer has asked me to machine some wear strips for a large assembly.

These are 3/4" x 4" bronze and they range from 5'-7" long to 6'-8" long.

The tolerances on the width are 4.000-3.997". The thickness gets machined down to .562" -.004 /+0

These also have 5/8" holes drilled through with 1" counter-bores, as well as Zig-Zag "Z" & "N" shaped grease grooves.

The grease grooves are 3/16" wide by 1/16" deep.

I double checked to see if they meant brass, but no it has to be " Bronze" . At first they said "Naval-Al Bronze"<:eek::angry::(:bawling::cryin: Now they want just bearing bronze ( 660 I'm guessing.)

Before I quote labor on this, I was wondering if it will warp so bad it will be unusable.

Thanks for any & all help.

JAckal:)
 
Thanks Bill, I never thought about them bending. Pretty much like a thin sheetmetal strip. That much weight, and no thickness.

The finished thickness will be .562:eek:

I will probably make wooden holders for them.

The material alone is over $12k.


Any more info??

Keep it coming,

JAckal:)
 
Thanks Bill, I never thought about them bending. Pretty much like a thin sheetmetal strip. That much weight, and no thickness.

The finished thickness will be .562:eek:

I will probably make wooden holders for them.

The material alone is over $12k.


Any more info??

Keep it coming,

JAckal:)

You are going to have to rough , flip & rough, flip * finish, flip & finish.
 
Do you have a planer? Actually, let me ask a different way: what's the X travel on whatever machine you plan to use? If it's less than the strip length, how are you going to control the thickness when you reset the strip for the 2nd (or 3rd) op?
 
You are going to have to rough , flip & rough, flip * finish, flip & finish.

Thats how we machine our wear bars.The ones we do are only 4' long but close to the same deminsions on width and thickness.

The material will warp but by flipping several times it is doable for sure,the ones we do still warp some when laying relaxed but not enough that the fastners will not pull them down.
 
If it is continuous cast like 954 Al bronze, it is more stable than I expected as far as machining or grinding goes, but I've never done any parts much longer than about 2'. But i have gotten 5' bars from UPS and there is some concern about bending as Bill has been describing. 660 is softer and would be even worse.

If the product comes in a cold rolled form to start, I would be very concerned about warping as it is machine.

For the size,those tolerances aren't exactly "generous" (for manual machines).

smt
 
If it is cast Why should it warp or bend The bending and warping comes most from rolling
And I have never seen any rolled bearing bronze I know I have not seen all so perhaps there is
Doing the thickness on a timesaver would indeed save time However if 0.1 -0mm tolerance is possible I don`t know
But if it warps anyhow you could premachine them on a timesaver and only the last cut on a mill
While doing the timesaver you could check how good you keep size and see from there if it is possible to sand to size

Peter from Holland
 
Need to investigate supplier and material spec you are getting very carefully. Ordinary stock bar material will bend like crazy in that sort of size. Friend John made a new cross feed drive for his Victoria mill (basically a helical rack and screw instead of the usual screw and nut) which, I think, started out around 1 1/4 x 1 or 3/4 ish and went down to around 1/2 thickness with a shaving off the sides. About 15 inches long. After the rack was finished and the thing unbolted it bent by over an inch on the thin axis pulling up so the teeth were on the inside of the curve! We eventually got it all straight and true without damage or loss of accuracy but the job was "interesting". OK the deeper, interrupted profile after cutting the rack teeth almost certainly enhanced the problem. Yes, he did skim all over first. Can't recall if material was phosphor bronze or SAE 660.

Clive
 
I would drill those holes and counter bores first, and use them to bolt it to a thicker steel plate. Maybe you can stress relieve it with heat before unbolting.
 
Just got home and have a cold brew in hand. On the trip home I got to thinking that Thermite is right.

C90300 Tin Bronze "Navy G"

If these cats can't deliver the exact size, get as close as you can and make a fixture and pocket it for those Mitee Bite clamps. Gas Axe a piece of 3/4" plate, bolt it to your longest x stroke mill, cut a 1/2" deep by appropriate width groove. Those Mitee Bites are bad ass.
It's been a long night. I think I'll go find some gratuitous sex and violence on tv an go to sleep in my recliner.
have fun
i_r_
 
Thanks Bill, I never thought about them bending. Pretty much like a thin sheetmetal strip. That much weight, and no thickness.

The finished thickness will be .562:eek:

I will probably make wooden holders for them.

The material alone is over $12k.


Any more info??

Keep it coming,

JAckal:)

Before I did anything I'd want to know how the job is going to be financed, free issue, customer supplied but at my risk, I supply - if so I'd want at least the cost of the material up front.

Doing $100 of work on $1000 of material, at your risk is a recipe for bankruptcy.

Personally I'd say thanks but no thanks.
 
If you do not know exactly how to handle this job,and materials are $12,000, SAY NO. Terrible risk to you if anything goes wrong. You could be left with scrap value warped strips.
 
Send them through a thickness planer(wood type with carbide blades)

Got to be safer than feeding them freerange through a horizontal climbmilling like me.
 
Rolled bars would have bending issues. I've never seen 660 bearing bronze in any shape but rotocast rounds and hollow rounds. 660 might be fairly relaxed due to the casting process itself, but acquiring the material in the right shape could be a concern.

I would think maybe a stress relief before beginning any work on it would be your best bet. Maybe hang the strips in a chimney and start a chimney fire ;) :D

Straightening in a press afterwards might be possible. Use a stiff urethane cushion to form it on so as not to mark it up. It bends easily.
 
Still need to know the material.

660 continuous cast is probably stable, but bendy.
954 " " is probably stable, will sort of self support with care. (I've got remainders of 60" bars of 3/4 x 2, and 1/2 x 3 or so in stock) My experience with 954 is that in pieces up to about 2' long even with somewhat complex machining, it barely moves
Other alloys...Who knows?
Rolled products (not continuous cast) are probably very prone to warping regardless the alloy.

How close are you to this customer? Have they had this exact job run before? Do they count on your for problem solving? If so, maybe they would agree to let you try one, their cost for materials, before committing to the whole order.

smt
 
You say they will be "Bolted Down" how far apart are the holes, if you can get it parallel, they will bolt down true. Sounds like a good job for rolling to size, getting something like that to stay flat is almost impossible and really not required if once assembled they will be held flat. We at work do jobs that require "Parallel Tolerances" but can in a free state be quite far out, once bolted down they lay flat!
 
My customer isn't the end user of the strips. His customer is.

He is a medium sized shop that does a lot of oil field assemblies & parts.

The have a planer that is 12' on travels.


I talked to him yesterday and he is willing to machine the longest parts the 8' long & 6' long to size. Then let me drill the holes & put in the grease grooves.

The reason they want me to cut the grooves is the odd shapes. I have a CNC mill & they don't.

He will purchase all of the material.

There are some smaller plates; 5" x 3/4" x 3ft, 9" x 3/4" x 3ft, & 4" x 9/16" x 2 ft, that I think would be more manageable for me.

My original thoughts were to cut & flip as said above.

Also, I have some 1" aluminum plate that can be used as a sub plate to keep from drilling into the table.

In the past I have milled a long trough in it for machining plastics. This would also work good like IR machinist said.

In the fine print on (3) of the drawings it noted: Material must be ASTM B-148-9C & the other one says 954 AL bronze.

The Al-Bronze might be more stable, although I know it is tougher to machine.

My customer also mentioned about if it warps when we unclamp it, they can still draw it down straight with bolts if it isn't too bad. The longer ones have (2) 5/8 bolt holes side-by-side every 12".

The shorter ones have 11/16" bolt holes every 6".

He also mentioned " blending it with sandpaper & scotchbrite wheels."

If he wants to do it under these conditions, I'll go for it.

They can do the long skinny parts, and let me have the 3ft & under parts.

All I have to do then is cut the grooves & drill/c'bore the bolt holes on the long skinny ones.

I'll get a definite spec on the bronze alloy Monday, and be back with more info.


Thanks to all for the help,

You guys are like uncles & big brothers looking out for each other.

That is why I always ask here first,

JAckal:)
 
Here is part of the prints. I can add this much without privacy issues.

The longer parts are .562 thick +0 /-.003 & all of the shorter ones are 3/4" with +/-.015 thickness.

All of the hole locations & groove dimensions are +/- .0015".

It is looking a lot better now.






JAckal:)
 

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