Pie cut tubes.

[God mode restorations]

Evening everyone..
Guys I have a question....what is pie cut tubing..I seen it on exhausts and intercooler pipes ect...but what does the pie stand for...how and what is it cut with..
Just curious....

 

[Fintray]

The side on section of the pipe looks like a slice of pie, cut with chop saw or bandsaw.

 

[Spark plug]

It's also referred to as a lobster back bend.

 

[God mode restorations]

So on a 90 degree radius for example. Depending on diameter. The radius is divided into to equal sections round the intire bend.looking like slices of pie

 

[kcchan]

Yup. Sometime called lobster backing as well.

EDIT: beaten too it. Also to add, it's used sometimes to achieve a bend rad not commercially available.

 

[God mode restorations]

Got ya.. cool. I wondered what the pie was referring to....cheers guys.

 

[Maker]

Also to add, it's used sometimes to achieve a bend rad not commercially available.

Not just unavailable radius's, but compound curves (Where the radius isn't constant), and twisted curves, both very hard to create with even the most fancy benders.

 

[Spark plug]

You can also develop very complex compound curves like this:

 

[God mode restorations]

You can also develop very complex compound curves like this:
View attachment 104301

Really like the way stainless discolours when tig welded.

 

[God mode restorations]

What methods do you guys use to cut the sections.

 

[norlander]

think a bandsaw would be my choice.

 

[Wallace]

Saw cuts only can be used for shallow bends.......

45mm mild steel tubing, depth stop set on the bandsaw and a line scribed along the length lined up with a pointer each time the vice was clamped.

Fabricating a mandrel to produce a one off silicone radiator hose.

Finished mandrel. All welds sanded back and polished.

Hose produced from mandrel.

 

[Crater Creator]

Saw cuts only can be used for shallow bends.......

View attachment 104605
45mm mild steel tubing, depth stop set on the bandsaw and a line scribed along the length lined up with a pointer each time the vice was clamped.



View attachment 104606
Fabricating a mandrel to produce a one off silicone radiator hose.



View attachment 104607
Finished mandrel. All welds sanded back and polished.



View attachment 104608
Hose produced from mandrel.

Now that there is a very nice job. So nice in fact I would have tried to find a way to use the polished metal tube instead of the hose!
How on earth did you get the mandrel out of the formed hose?

 

[zx9]

WHS ^^^^^^^^^^^^^^^^ Off topic but how is the mandrel removed from the finished silicone hose?

 

[WorkshopChris]

@ukracer you might want to look at this. You started a post about this subject but it ended up a little off track and food related.

 

[ukracer]

@ukracer you might want to look at this. You started a post about this subject but it ended up a little off track and food related.

Cheers mate....most of my threads end up like that. I think it's a conspiracy.

 

[norlander]

Saw cuts only can be used for shallow bends.......

fine, nice job but we is we is talking lobster backs/pie cuts.

 

[Wallace]

Now that there is a very nice job. So nice in fact I would have tried to find a way to use the polished metal tube instead of the hose!
How on earth did you get the mandrel out of the formed hose?

WHS ^^^^^^^^^^^^^^^^ Off topic but how is the mandrel removed from the finished silicone hose?

Not sure, I wanted to see the process and do a feature for a car club magazine but they were unable to accommodate me on the day.

fine, nice job but we is we is talking lobster backs/pie cuts.

True, thought it was worth a mention as an alternative for shallow bends.

 

[Pete.]

When I had to do lobster back bends I used 15 degree cuts which produces a 30 degree bend. I used that figure because it matches the old 30 degree grinds on valves and I figured that someone much smarter than me had worked out that 30 degrees was a good angle for gas flowing over the valve so who was I to argue?

 

[indy4x]

is that 30 degree on inlet and exhaust valves? i would have assumed that the 30 degree would have been used as it gives the best sealing of the valve without the valve jamming shut cos the angle is too great, but thats purely a guess