Though often underestimated, tube end preparation is one of the most critical processes in obtaining an optimum seal of any flanged, brazed, flared or preset tube end connection. When properly performed, the three steps, outlined below, of cutting, deburring, and cleaning will assure the integrity of your tube and prevent leakage in your tube fitting connections caused by improper tube end preparation. These guidelines are similar for all tube, regardless of the tube material.
It is critical that the tube be cut squarely within ±1° in order to assure the proper connection. If it is not cut squarely, it will not rest properly in the braze sleeve (ORFS connection) or fitting body (flareless connection). A tube end that is not cut squarely may also result in a flange or flare that is not circular.
Issues that can occur with tube ends that are not cut squarely
When cutting tube in preparation for flanging, brazing, flaring or presetting, a saw with a toothed blade is recommended. This type of tool will assure that the tube end is cut clean, with minimal burrs or contamination, and is not exposed to excessive heat or working of material, typical of abrasive saws and tube cutters. For Harder metal such as steel and stainless steel tubes, we recommend the use of a rotary toothed saw. However, if you do not have access to one, you can use a hacksaw with a saw guide instead.
Improper cut (left) and proper cut (right). The improper cut is showing what happens when a rotary cutter is used on harder materials, in this case steel.
Rotary tube cutters may be used with soft tube such as copper and aluminum. However, for steel and stainless tube rotary cutters will cold form the tube, hardening the material and creating excessive I.D. collapse or burr. The hardened material causes problems during end forming. All of this can compromise the tube sealing surface.
When cutting your tube, make sure that the tube is securely in the vise, then slowly cut through the tube to minimize the burrs.
Deburring the inside and outside diameter of the tube end is necessary to assure the tube fits properly inside the braze/flange/flare sleeve or ferrule and fitting body. Proper deburring of the tube end is also necessary to form a tube flange or flare which is free of imperfections that may create a leak path between the tube and the fitting sealing surface.
You should lightly deburr the I.D. and O.D. of the tube end to remove burrs and sharp edges. You can use either a hand deburring tool or a power deburring machine. It is important not to remove too much material when deburring tube ends as it can be detrimental. Just lightly breaking off the edge is sufficient.
Tip: if using a hand deburring tool, point the tube end downward while deburring to keep chips from entering the tube.
Debris may remain in the tube end from both the cutting and deburring processes. Debris present in the tube end can result in system contamination or can be lodged (or can embed itself) into the flange or flare, which may result in imperfections on the tube surface that can lead to potential leak paths. It is recommended that the tube end be cleaned properly prior to any further processing such as flanging, flaring, brazing or presetting.
To clean your tube after cutting and deburring, use a brush to remove chips from the inner diameter, then use a clean rag to wipe the inner and outer surfaces of the tube end.
Watch the video for a great visual of the steps we discussed:
In conclusion, following these steps every time will assure the integrity of the tube and prevent possible leakage in your hydraulic tube fitting connections caused by incorrect tube end preparation issues.
Do you have any additional tips or stories from the field about tube end preparation? If so, please share by commenting using the link above. If you have any questions or comments, please post them and we will respond if warranted. To talk to our techConnect engineer team directly, they can be reached at Parker Tube Fittings Division, 614.279.7070.
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Contributed by Burleigh Bailey, senior project engineer, Parker Tube Fittings Division
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