Radius or chamfer?

[FC2008]

If I have a pipe and want to make the edges less sharp. Is it best to add a radius or just chamfer the edge?
How about machining cost, does it cost much more to make a radius?

Thanks

 

[handleman]

Chamfer works just fine. Radius is expensive.

-handleman, CSWP (The new, easy test)

 

[FC2008]

Thank you

 

[jmw]

Er, does it make a difference sometimes?

I would expect that there should be some defined standard for particular applications where there are sound reasons for one or the other. If there is no relevant standard expressed I guess it doesn't much matter.

We had a part that was spark eroded and it would then be shot blasted for some applications, electro-polished for others and for PFA coating something else altogether. Coatings, it seems, don't like corners/sharp edges.

On the other hand, how many drawings show radiused corners when chamfers would do as well? And what if the part is then shotblasted?

Was there something special about your application?

Just curious.

JMW

http://www.ViscoAnalyser.com

 

[FC2008]

The part is to be painted, including the chamfer/radius.
Would the paint job suffer from the chamfer?

 

[GregLocock]

Yes, it can do. The paint draws back from the breakpoint on the chamfer, leaving it with a thinner coat there. This can be worse with powdercoating, the charge builds up on the sharp edge.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[FC2008]

I just talked to the machining company that does our work and it turns out that it isn't more expensive to make a radius of 2 versus a 2x45 chamfer.

Thanks

 

[TheTick]

A chamfer has more "blunting" effect for less material removed.

 

[eromlignod]

If it's milled, it costs basically the same, since they just use a different cutter.

If it's an outside chamfer done in a lathe it is often done carefully by hand with a file or a simple angular cut. A radius would probably require a profiling tool, but if its a common size it's a no-brainer.

The only case where I could see the radius costing more is if it is an exotic size, requiring a special tool or setup.

Don
Kansas City

 

[KENAT]

From a machine cost point of view, general wisdom is that external radii are more expensive than chamfer.

However, this is highly dependant on the specific application as eromlignod explains.

In many cases there is little or no cost differenc.

Also with CNC machines, if the rad/chamfer is created by the path of the cutter then the price difference is negligible.

Another factor (not relevant to your OP & assumiong shape created by cutter) if you have chamfers of different sizes on a piece, these can often/usually be made with one tool. If you have a number of different radius you'll need a different cutter for each size radius - which means more cost.

Generally I spec a chamfer unless there is some other functional requirement for a radius - such as your paint concern.

(This is all based on what I've been told, not what I've done first hand.)

KENAT, probably the least qualified checker you'll ever meet...