To determine a spiral bits direction of cut you need to look at it upside down. I don't mean you need to be upside down, but the bit needs to be upside down. So hold the router bit's shank in your hand with the cutting edge pointing towards the ground. Now spin the bit in a clockwise rotation. If the spiral is 'pushing' down you're holding a downcut bit, if the spiral is pulling up you're holding an upcut bit, there, that was easy. The other way to look at it is to hold the bits in your hand with the router tips facing upwards.  Reading the flutes from left to right, if the flute goes upwards to the right, then you have an upcut, and if the flutes go downwards to the right, then you have a downcut.  I drew really bad arrows on the photograph below to illustrate my point.  By now you've probably figured out that spiral bits were originally meant to work in an overhead (handheld) routing application, having been developed for guys with overhead CNC routers.

The solid carbide spiral bit uses a constant shearing action when making the cuts instead of a typical straight head router bit which basically smacks the bit edge against the wood over and over.  This does not mean that the spiral bit is your perfect go-to bit though.  Straight bits still have their place and typically get used more in most shops, not to mention that spiral bits have a higher up-front cost.

Solid carbide spiral router bits cause confusion.  What is the difference between upcut, downcut, or the compression up/down spiral router bit that does both?  Do I need all of them in every size?  Why can't I use one for every job?  Why not just use a straight bit?

If the outer surface is machined and the allowance is large, generally adopts the HLCBN material or BNK30 material to be roughly processed, then grinding with a grinding wheel. For small machining allowance, the roller can be grinded directly with a grinding wheel or profiling processed by diamond tools. In general, cutting alternative grinding can improve machining efficiency and the cutting method is more conducive to improving the production lead time.

Our solid carbide spiral router bits (both individually and in sets) provide remarkable performance and durability. Upcut bits pull chips up and out of the kerf for faster cutting. Downcut bits don't clear chips as quickly as upcut bits but their downcut geometry leaves a cleaner cut.

In this photo, you can see that I used the upcut bit for the U and the downcut for the D.  The D has a much cleaner edge with minimal tearout (excluding the fact that it is freehanded and I have a hard time going in a straight line without a jig), while the U has a larger amount of tearout.

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Although the tungsten carbide material is better than other materials, it is difficult to machining due to extreme hardness and it is more widely used in the steel industry.

1. Develop a new type of roller shaft material. Conventional ductile iron roller shafts will be difficult to withstand greater rolling power and deliver a larger torque. So high-performance cemented carbide composite roll shaft materials must be developed.

When machining a tungsten carbide roller, passivating treatment is necessary to reduce or eliminate the sharpness value, for the purpose of flatness and smoothness with high durability. However, passivation treatment should not be too large, because the contact surface of the tool blade is large after passivation and the cutting resistance is also increased, which is easy to cause a crack, damaging the workpiece.

The downcut bit is the one I use more often though as I use it for cutting grooves, dadoes, and inlays.  This bit's fluting direction pushes the top grain on the wood down creating a cleaner top surface when you are doing grooves or inlays.  A lighter depth of cut is preferable with this bit.

The carbide roll has a high hardness and its hardness value varies very small with temperature. The hardness value under 700°C is 4 times higher than the high-speed steel. The elastic modulus, the compressive strength, the bending strength, the thermal conductivity are also 1 times higher than the tool steel. Since the thermal conductivity of the cemented carbide roll is high, the heat dissipation effect is good, so that the surface of the roll is under high temperature for a short time and thus the high-temperature reaction time of harmful impurities in the cooling water and the roll is shorter. Therefore, the tungsten carbide rollers are more resistant to corrosion and cold and hot fatigue than tool steel rollers.

3. Due to the differences in the rolling force, rolling torque, heat transfer performance on different racks, the different racks should adopt different grades of tungsten carbide rollers to ensure the reasonable match of the strength, hardness, and impact toughness.

One important thing to take note of is that if you do use the spiral router bits in a router table, then the downcut bit will actually push material towards your workpiece sometimes raising the workpiece off of the table.  It will still function the same making a clean-edged cut, but it does want to raise the workpiece up, so its important to use a good downward feather board system.  And please take light passes when using it in the table.  The upcut bit will actually pull the piece downward towards the table making it a little safer, but the tearout issue still exists.

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With the rapid development of the steel industry, in order to improve the output of steel and improve the utilization rate and productivity of the rolling mill, reducing the shutdown times of the rolling mill, adopting a tungsten carbide roller with long service life is an important method.

2. During the manufacturing process of carbide rollers, the residual thermal stress caused by thermal expansion between the inner metal and outer cemented carbide must be minimized or eliminated. The carbide residual thermal stress is a key factor affecting the life of the roller. Therefore, the coefficient of thermal expansion difference between the selected inner metal and outer cemented carbide should be as small as possible, while considering eliminating the residual thermal stress of the carbide roller ring through heat treatment.

The compression (upcut & downcut) spiral bit creates a great edge on the side of a board when you need both edges to be crisp.  Its spiral action pulls both sides into the center of the bit where it ejects out of the side.

In recent years, the tungsten carbide rollers have gained more and more extensive applications in steel production with their excellent performance. However, there are still some issues in the production and use of carbide rolls.

Downcut bits don't clear chips as quickly as upcut bits but their downcut geometry pushes wood fibers down into the cut and leave a nicer quality top surface on your workpiece. They do require a slower feed rate. When used in a router table downcut bits actually push your material up.

Why not just use a straight router bit? Well, that's an easy one.  The spiral bit's geometry and top point allow you to plunge into your work like a drill.  Our solid carbide spiral bits begin life as extra-hard C4 micro-grain cylindrical carbide blanks. We then use sophisticated 6-Axis C.N.C. grinding machines to grind their spiral geometry.  The precision of the spiral and hardness of carbide allows for a very sharp edge and typically longer edge sharpness. A straight bit can't compete with that.

The performance of the tungsten carbide rollers is related to the content of the bond metal phase and the size of the tungsten carbide particles. The tungsten carbide is about 70% to 94% of the total composition and the average particle size is μm of 4 to 8. If the metal bond content is increased or increases the particle size of tungsten carbide, the hardness of the cemented carbide decreases and the toughness is improved. The bending strength of the tungsten carbide roller ring can reach 3000MPa. and the HRA is 78 to 90.

For the rolling of wire, rod, tungsten carbide roller replacing conventional cast iron rolls and alloy steel rolls, has exhibited a lot of superiority, with the continuous development of roller manufacturing techniques and use technology, will continue to expand the applications of carbide roller rings and they will become more important in rolling machining with wider applications.

The carbide rollers are mostly used on cold processes of wire drawing? or could it also be used in hot process? what process is best used on?

The cemented carbide roller, also known as cemented carbide roller ring, refers to a roll made of tungsten carbide and cobalt through the powder metallurgical method. The tungsten carbide roll has two types of integral and is combined. It has superior performance, stable quality, high processing accuracy with excellent wear resistance and high impact resistance. Carbide roller is widely used for the rolling of the rod, wire rod, threaded steel and seamless steel pipe, which greatly improve the operation efficiency of the rolling mill.

Upcut bits pull chips up and out of the kerf for faster cutting. This type of bit is ideal for high-volume shops but the workpiece must be securely clamped in place to prevent lifting. For work requiring a finer finish consider a downcut spiral bit.

Our solid carbide spiral router bits are designed to provide remarkable performance and durability. They quickly slice through hard or soft wood, plywood and composites such as MDF or particleboard. Manufactured using state-of-the-art computer-controlled machinery; these micro-grain carbide cutters feature our optimal helix design and a stronger body that reduces vibration and lasts up to 300% longer than regular router bits. Unlike straight router bits, Infinity solid carbide spiral bits feature a helical spiral design that is continuously in contact with the workpiece, producing smoother cutting action and the cleanest results possible.

The tungsten carbide roller can be divided into two types of integral and composite according to structural form. Integral tungsten carbide roller has been widely used in pre-precision rolling and finishing stand of high-speed wire rolling mills. The composite cemented carbide roller is composited through tungsten carbide and other materials. The composite carbide rollers are cast directly into the roller shaft, which is applied to a rolling mill with a heavy load.

The upcut bit's spiral direction allows for great chip ejection from the cut making it the perfect router bit for plunge cut mortises.  This bit ejects the wood chips out of the way of the router bits point making the plunge go nice and easy with less chance of bit wander.  It is fine for any hole or opening that will not be seen.

When machining the tungsten carbide rolls with a hardness smaller than HRA90, select HLCBN material or BNK30 material tool for a large amount of turning and the tool is not broken. When machining the carbide roller with a hardness of greater than HRA90, a CDW025 diamond tool is generally selected or grinding with a resin diamond grinding wheel. Generally, the higher the hardness is, the material is crisper, so it is more cautious for cutting of high hardness materials and the exact reserved finishing grinding allowance.

Please note: The recommended depth of cut for any single pass is 1/2 of the diameter of the tool. For example, if you are using a 1/4" diameter cutter you should only take a 1/8" depth of cut for any single pass. When used in a router table upcut bits actually pull your material down.

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