How to Bend Stainless Tubing

Tube Bender Anatomy

Today, on the Mako Superlok Blog, we’re talking about everything you need to know about hand tube benders and how to bend tubing. If you’re just learning about tube bending, there are a lot of terms and features of these tools that can be kind of difficult to get your mind wrapped around. We’re going to start with just the anatomy of a tube bender. Looking at each part of the bender, we will talk about each part and the reason that it’s there. After we get that sorted, we’ll talk about how to use all the features to your advantage to make the most accurate bends possible.

Think you know everything you need to about benders? Click here to jump into the bending part↓

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Bender Parts

• Handles
• Starting at the top, we have our handles. They allow a bender operator to gain a leverage advantage to apply proper force to the tubing. Bending stainless tubing takes a considerable effort compared to softer metals.
• Tube Latch
• The tube latch grips the lead end of the tubing tightly. By locking the tubing in place, it prevents the tubing for slipping out of alignment aiding the operator in making precise bends.
• Handle Release
• This release can be drawn back to reorient the short handle by 90°. This is needed when an installer has a need to bend a tube between 90° and 180°.
• Roller dies
• The roller dies prevent the bending process from marring the tubing by rolling along the tubing as the bend is made. This system uses two rollers for extra support of the tubing throughout the process.
• Center Die/Mandrel
• This piece is precision-sized to the tubing and very sturdy. This helps the tube maintain its shape without crushing or kinking while being bent.
• Vice Block
• This solid and flat sided piece is designed to be clamped into a vice. Doing so improves the function of the bender by holding the center mandrel while the tube bender is in use. Operators using this method don’t need to worry about applying force to both handles, simplifying the process significantly.

Bender Markings and Indicators

Two sets of marking reside on the front face of the bender. The first set is the bend angle scale. It ranges from 0° to 180° and shows how many degrees of angle you have already bent. The second is the angle starting scale, and on these marks you’ll line up your bend point. However, you may have noticed that not all of these indicators are numbers. What are the “R” and “L” for? These two points are designated this way because of their relationship to one another. The “L” is the 90° bend point and “R” is the 60°. However, if you needed to make a reversed 90° bend, you would line your 90° bend mark up with the “R”.

When bending tubing, the “R” is for reverse bend. Use this mark when you need to make a
90° bend with the tail end of the tubing latched in the bender instead of the lead.

So then, what if you need to make a 15° or 30° angle? Since not all benders have indicators for these angles, you must put your mark an appropriate distance between the marks that are labeled.

Measuring to Bend Tubing

Before we can put this information to use we need to take measurements for our tubing. When working with tubing, all measurements should be relative to the center line of your tubing. Every time we start a run we should measure from the center of the fitting at the start of the run and end at the center of the fitting that finishes that run up. This measuring method is referred to as “center to center”.

Once you know your measurements, it may be wise to make a map of your run so that you don’t lose track of them. This step isn’t strictly necessary, but it sure helps with complex systems with multiple runs. A map will also help you calculate how much tubing you’ll need to complete the run. Coming up short on your last bend is an infuriating scenario. However, you should not cut your tubing to that specific length just yet. Since radius corners use just slightly less tubing than sharp squared off corners, you will want to cut the length after bending.

Your First Tubing Bend

Starting on the lead end of the tubing, make a mark at the length of your first leg. Next, take a ferrule, slide it down your tubing and use it to translate that mark all the way around the tubing. This will ensure that you can see the mark clearly regardless of the tubing’s orientation. From there, insert the tubing into your bender and loosely close the tube latch so that the tubing position can still be adjusted. Since we are making a 90° bend, we will line the bend mark up with the “L” on the starting indicators. Finally, fully close the tube latch and apply pressure to the short handle. Before completing the bend, you may want to stop just short of your goal and make sure that your bender is calibrated correctly. If you under bend the tubing you can always put it back in the bender to complete the bend. However, if you over bend, you should not attempt to unbend the tubing. This can cause stress to the bent area and weaken its integrity.

The Second Bend

Once the bend is complete and verified to be the proper angle, it’s time to move on to the next bend. It can be helpful to take your next measurement while the tubing is still in the bender. The shoulder of the center die often sits at the center of the tubing, so this can be used as an anchor point. If your bender does not share this feature, be sure and measure from the center of the last section of tubing to get your proper length. Once you’ve finished measuring, all the instructions for your following bends are the same with one extra thing to keep in mind. Alignment! For this demonstration, our two bends are in alignment with each other. In order to achieve this, we can put a level on the center die and then on the previous bend to make sure that they are planar. Additionally, if you’re not using a vice to hold your bender, you can sight down the handles to verify alignment. Although, if your bends are not meant to be planar, you’ll need to make sure that your bends are clocked to the correct positions relative to themselves.

After You Bend Tubing

Once you’ve bent the tubing into the shape you require, it’s time to cut its final length. We recommend using a hacksaw because it makes clean straight cuts without beveling the end of the tubing. Though, it is important to remember not to let your cutter scar the tubing near your cut point. Imperfections in the tubing of any kind can weaken it. This is especially true when that marring occurs in the area where the ferrules bite. Whatever your preferred cutting method, use a deburring tool to clean the end of the tubing. This will help the ferrules seal and reduce media turbulence in the line.

Final Fit

It’s finally time for that moment of truth. A good fit is where you can slide the tubing in place without forcing or struggling with the tubing. If you measured correctly and checked your angles as you went along, it shouldn’t be overly difficult to get a good fit. However, there is a chance that your fit is a bit tight. This pressure is called side-load and it can impact the integrity of your system by making the fittings feel hand tight well before they should. In turn, this means that the installer begins counting 1-1/4 turns too early and never fully beds the ferrules properly. If side-load is prevalent, see if it can be remedied by adding just a little more angle to one of your included bends. Alternatively, if side-load cannot be reduced, using Superlok i-Fittings will still ensure that you have tightened the fitting correctly. For more information on i-Fitting Click Here

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