Tool bits life can be extended and more consistent finishes produced through frequent removal of B.U.E. (Built Up Edge) by horning the bits cutting edge. This condition can occur any time the bit rotates with enough speed and friction to fuse material to the edge . Talk to your sales coordinator for more information.
End Preparation Squareness
Tri Tool Inc. designs all standard ID mounting weld end preparation products to machine the end square to the mounting surface within .002" per diameter inch and flat within .005" . Tri Tool does not test and certify each tool to meet the criteria, but the initial production lot is verified to meet the criteria and random samples are tested thereafter. A squareness factor of .002" per diameter inch is equivalent to about 1/8" of one degree. If a customer requires a certification of squareness and flatness then Tri Tool will test a machine at time of sale and provide the certification at a nominal fee.
There are several factors which can give the appearance of a machine cutting out of a square, when in actuality a machine is not at fault.
To perform a squareness test with an ID machine select a short length of pipe or tube ( length to be about 3 to 6" for the small bevelers) with a reasonably good ID surface and proceed as follows.
1. Mark an axial line on the side of the pipe/tube.
2. Install the sample with the line indexed over a mandrel blade or jaw block.
3. Use a facing bit to cut the tube.
4.Remove the sample and reinstall with the index line over the same mandrel blade or jaw block to cut the other end.
5.Cut the second end flat.
6.Measure the length of the sample in several places to find the high/low points either with Verniers or on a surface table.
The difference between the shortest measurement and the longest measurement divided by the actual diameter of the pipe/tube is equal to twice the out-of-squareness factor. By indexing the sample to mandrel blade any misalignment
will be in the same plane on each end. This makes the length measurement differences double the actual out of squareness factor per end.
Changing Cutting Bit Position for Best Results
Optimize the burr conditions on the tube squaring operations. How the tool bit is mounted can shift the .005" burr from the ID to the OD (or the OD to the ID). The balance between the ID and the OD burr conditions (even though they are small) can be shifted by changing the shear cutting angle of the tool bit.
Tri Tool DURABITS for the tube squaring are ground with a high shear angle to minimize the residual burr on the ID of the tube and make the chip go to the outside. However, by mounting the tool bit to use the outside part of the cutting edge, there is less effective shear which will reduce the OD burr. Moving the bit as far "out" as possible (the tip of the edge must remain inside the bore of the tube) will provide the most shear action for minimum burr on the ID of the tube.For tubing with an ID greater than .50", a tool bit can be mounted backwards in the tool bit holing slot ( with the cutting edge away from the centerline) for even greater shear action. Relatively small changes will sometimes make a difference so experiment with what works best for you.
Potential For Carbon Contamination from High Speed Steel Tool Bits
The potential for carbon contamination of high purity and ultra-pure stainless steel piping/tubing systems for the use of High Speed Steel (HSS) tool bit has been discussed and debated for many years. In most cases the question comes up on systems using electropolished stainless steel tubing which has to be squared for autogenous welding. There is no acceptable alternative cutting material for achieving a burr-free tube end that does not contain carbon. A stainless steel tool bit that is carbon free does not exist.
Tungsten carbide has been recommended and used, but two problems exist, it is difficult to make a tool bit for burr-free cut with Tungsten Carbide and theoretically Tungsten Carbide which is a molecule of one Tungsten atom, and one carbon atom can decompose under high heat to release a carbon atom and form an alternate carbide compound. The possibility of depositing carbon from Tungsten carbide is just as great as with HSS. Cermets use HSS for a metallic bond matrix. Diamond is nothing but carbon. Stelite contains carbon. HSS tool bits have been used for squaring stainless steel tube in the microelectronics, pharmaceuticals and experimental physics programs for many years. Weld joints are continuously monitored in some of these programs and there has never been any evidence reported that the problem exists from carbon contamination as a result of using HSS tool bits.
From a practical point of view the amount of material that could be deposited from hardened and ground tool steel with only about .2% carbon is very small. In practice, in order to achieve a burr-free end prep, the tool bits must be run slow and not create high temperature levels in either the tube or the tool bit. These conditions automatically reduce the probabilities of depositing metal on the surface of the tube being machined.
Recommended Cutting Speed for Tube Squaring and Severing Equipment
To obtain minimum burr tube ends it is essential that heat buildup be avoided. When either tube or the tool bit gets hot, the tube material starts to flow or push away from the tool edge as a burr, instead of being cut cleanly with a minimum burr. The three basic operating conditions which generate excessive heat along with corrective actions are:
Cutting speed (RPM) is actually a range depending on the material conditions. Some judgments, based on the cut conditions must be made to select the actual speed. Generally the cutting speeds should be:
Time/ Head Revolution
Tool Bit Selection
Obtaining the best results starts with selecting or determining which tool bit to use with the material being cut. Tri tool has three basic cutting edge geometry's which function well on most of the common tubing materials. In addition to variations in the edge geometry, tool bits are available made from M-42 tool steel, variations in height and combinations of all three as shown in the accompanying table. Selections of the tool bits should be based on tubing material, how critical it is to have a neat burr-free end and tubing size.
General guide lines for selection of the tool bits are:
There are practical limits to when and how many times a tool can be resharpened. The number of times a tool bit can be resharpened is dependent on the type of tool bit and the application.Some of the conditions which make it impractical to resharpen a tool bit are:
Conditions which effect the number of times a bit can be resharpened include:
Micrometer Feed
For squaring and severing operations where control of the depth of cut is an important facto, an optional micrometer feed assembly is available for some models. Contact your sales representative for more information.
Working With Microfittings
Most welded high purity tubing systems utilize electro-polished microfittings. Our equipment properly prepares microfittings for orbital welding by producing perfectly flat, square ends, while maintaining the perch length required for automatic weld heads. This is essential for both new and reclaimed components and tube sections. Tri Tool, Inc. special engineering and quality custom manufacturing can provide you with special microfittings as required.
