# mitered vs smooth

#### ysn

##### Senior Member
Hi, please what is the difference between mitered and smooth in this context:
"100 mm radius mitered 45 degree elbow equivalent length 750 mm"

"150 mm radius smooth 45 degree elbow equivalent length 300 mm"

Source: Building Code

Thank you

• What context? Please tell us what on earth this is talking about.

Here it means cutting both pieces at 45 degrees and putting them together. It may or may not be smooth.

It talks about clothes dryer duct when using elbow fittings. It covers the typical short radius mitered elbows and the equivalent lengths to the various types of elbow fittings.

johshen64, there is a table talks about dryer exhaust duct fitting type and equivalent lengths like:

"200 mm radius smooth 90 degree elbow ...length equivalent 475 mm"
"200 mm radius smooth 45 degree elbow...length equivalent 300 mm"
"100 mm radius mitered 90 degree elbow ... length equivalent 1500 mm"
"100 mm radius mitered 45 degree elbow ... length equivalent 750 mm"
So the question is: What is the difference between smooth and mitered?
I expect mitered means connected, in other words, fittings are connected to the elbow either by 45 or 90 degrees, but I am not sure from this meaning.
But "smooth" here I don`t know its meaning here at all.

TABLE
DRYER EXHAUST DUCT FITTING EQUIVALENT LENGTH
DRYER EXHAUST DUCT FITTING TYPE
EQUIVALENT LENGTH
100 mm radius mitered 45 degrees elbow
750 mm
100 mm radius mitered 90 degree elbow
1500 mm
150 mm radius smooth 45 degrees elbow
300 mm
150 mm radius smooth 90 degree elbow
525 mm
200 mm radius smooth 45 degrees elbow
300 mm
200 mm radius smooth 90 degree elbow
475 mm
250 mm radius smooth 45 degrees elbow
225 mm
250 mm radius smooth 90 degree elbow
450 mm

A mitred (BE spelling) elbow turns abruptly through 45 or 90 degrees; the tubing is cut at half the angle and two pieces joined. A smooth elbow is curved to turn through 45 or 90 degrees; the tubing is bent, not cut.

Thank you very much for your best efforts.

Thank you very much for your best efforts.
Do you have access to Google searches? If so, you might make a little more effort yourself. There are many images of mitered (or mitred) elbows.

and of smooth elbows

I mean I don`t understand the words "smooth" and "mitered". There is no context to explain what "mitered" or "smooth" means.
I understand the elbow with 90 or 45 degrees, but this does not explain the meaning of both words, mitered and smooth.
Smooth is a very easy word, but what does it mean in comparison to "mitered"?
I hope you get the point Andygc?

A mitre is a type of joint. There are 4 mitres in the picture of the mitred elbow above.
There are 3 mitres in this elbow

But in the table, why do they call it elbow, not fittings?
So "smooth" means no fitting in the elbow? which means that has a smooth surface, which is clear from anything?

But in the table, why do they call it elbow, not fittings?
Because it is an elbow. Users don't buy each of the individual sections of a mitered elbow and weld them together; they buy the complete thing.

But in the table, why do they call it elbow, not fittings?
We don't use the word 'fittings' for this. The elbow is the whole thing. If we look at Andy's picture in #11, the elbow consists of four sections with three joins, which are mitered joins. Mitred means they have these corners in them. This makes it possible to build the elbow using simple flat sheets of metal, rolled into cylinders and then cut at an angle.
So "smooth" means no fitting in the elbow?
Smooth means there are no corners in the elbow. As in the lower picture in #9. You can't make a smooth curve from joining flat sheets of metal together.

So smooth means one curve/turning piece?

Smooth has its usual, primary, meaning:
free from projections or unevenness of surface; not rough
The curved pipe that forms the elbow has no bumps, creases or joints.

Thank you all for your best efforts to help.

So smooth means one curve/turning piece?
Both types of elbow are bought as a single piece.

A smooth elbow:

A mitered elbow:

A smooth elbow offers a lower resistance to fluid flow than a mitred elbow, and I expect that if your table of equivalent lengths listed a pair of elbows where the only difference was that one was mitered and the other was smooth, that the equivalent length of the mitered elbow would be greater.

Of course, the table states exactly as you said, Uncle Jack, but without paying attention to resistance, just their lengths as mitered and smooth elbows.
Thank you very much, Uncle Jack.

The equivalent lengths appear to be a measure of flow resistance, hence smaller radius elbows having longer equivalent lengths than larger radius elbows.