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Mandrel Bending, Marman Flanges, Mandrel Bent Tube

What is Mandrel Bending?

Mandrel Bending is to bend tubing without any distortions in the bend area. By the use of a mandrel inserted to the inside of the tube, the mandrel keeps the tubing inside diameter nearly round during the bend process. Other benders crush the tubing and the loss of flow area can be a minimum of 40%.  Mandrel Bending keeps the flow at 96-99%.

Youtube video here: https://youtu.be/F9ygWTqOfA4

Marman Flanges, what are they?

Marman flanges have been created in the 1940's by Herbert "Zeppo" Marx of the Marx Brother fame.  This flange was created to be simple yet be able to handle extreme pressures up to 3000 PSI associated with liquids and is superior to vacuum volume as well.  These were used during World War 2 as a fast disassembly of automobiles and aircraft. Without this ingenious assembly, the war would have certainly had a different outcome.  Currently, these are used on all diesel semi-trucks across the world as well as irrigation pipes, aircraft and these have even been used on the Space Shuttle Rocket Boosters . GBE Mandrel decided to manufacture these in smaller sizes to be able to handle the light exhaust pressures from automotive uses with ease.  Unlike the V-Bands, these DO NOT LEAK.  

Youtube Video here: https://youtu.be/dZFC7HiNy-

Mandrel Bends

What is tubing? What is piping? Aren't they the same? 

Actually, NO

Tubing is what is used on vehicles, bikes, motorcycles, fences. Everything that doesn't require alot of strength.  Tubing uses outside diameter and a wall thickness which is measured in gauge.  The thickness compared to pipe is usually quit thin. If your looking for 2" tubing, it will be 2" measured outside diameter.

 Piping uses inside diameter and doesn't give a wall thickness per se'.  Usually it is measured by schedule.  It is usually used for water, sewage, drains, roll bars/cages.  This is usually quite a bit thicker in material than tubing because it needs to handle more pressures inside and out. If you are looking for 2" piping, then the inside diameter is measured 2", but the outside diameter could be 3" or even 12"! 

Make sure you know what your asking for!

We only bend tubing, not piping.

Don't know what tubing to use?  Here are the basics:

Steel Tubing: Great for inexpensive mock-ups, prototypes and headers but you must paint, plate or ceracoat the material.  Welds good with mig, tig, oxy/act. Longevity? Unpainted, 2 years. Painted, 4 years. Plated, 10 years. Ceracoated, 10 years-15 years. Recommended for headers!

Aluminized Tubing: This is what your local exhaust shop uses.  Aluminum coated steel tubing that resists rusting.  Welds great with mig welder with shielded gas. You must paint outside of the welds otherwise rusting will occur. Longevity, 10 years except at the welds on the inside of the tube. Great for a do it yourself exhaust system.

409 Stainless:  This is where we get technical.  409 tubing is known as "exhaust tubing".  IT IS MAGNETIC! It welds good with mig and better with TIG using simple argon gas and a grey tungsten.  Not very polish-able, but when bent, it stays there.  This is what is mainly used by the "top guys" in the exhaust filed for kits and mufflers. Perfect for ALL custom exhaust. Is magnetic, but will mainly resist rusting. Longevity, 20 years Perfect for custom exhaust systems.

304 Stainless:  This material is slightly magnetic and can actually become more magnetic when heat is applied or in the mandrel bending process.  304 is a super durable material except when put to high heat. Stress cracking can occur at welds or seams.  Material does NOT keep it's shape when heated.  Tends to attempt to straighten out bends in heated. Perfect for coolant (anti-freeze) lines.  Highly polish-able.  Not great to mig weld, must use helium blend. Tig welder can make welds look great, only argon needed with grey tungsten.  Can be used on headers, but material will crack over time.  Better off for a not-much used show car.  Longevity, 20 years.

Want to see some really COOL videos?

Click on the link below to see GBE Mandrel Bending's You Tube channel.  We bend tube, fabricate, exp

Contact Us


If you have a drawing or bulk inquiry, Email us at GBEMANDREL@GMAIL.COM

Local? Stop on by!  We are always here to help.  Open to the PUBLIC!


15600 SE For Mor Court, Suite B, Clackamas, OR 97015

(503) 344-4149




Please call us between the hours of 7am-5:30pm M-F so that we can answer all your questions. Special requests, email us at: GBEMANDREL@GMAIL.COM

Mandrel Bending or Crush Bending?

Did you ever want to know what Mandrel bending is and how we achieve our nice bends?