Frequently Asked Questions

Question:
Why do some compression spiral bits have a short up-shear and others have a longer up-shear?

Answer:
When using compression bits on a flat table router, it is important to choose the short up-shear on a compression spiral (usually 3/16”).  The reason for this is, that on smaller diameter tools a longer up-shear could sometimes lead to thinner panels moving on the table if the vacuum hold-down is not sufficient, i.e. it could try and “lift” the material as it cuts.  This possibility is eliminated with a shorter up-shear.  The shorter up shear also eliminates tear out when using the tool for shallow grooves or dados. The longer up-shear bits are better used on pod/rail machines.

 

Question: 
Is there any difference in carbide grades that are used on compression spiral bits?

Answer:
Carbide grades can vary from one manufacturer to another.  In general, a medium grade composition of carbide grain and binder will work well on a variety of materials, such as wood, plywood, particleboard, MDF, chipboard etc. and is very suited for smaller shops that are machining different wood species or composite panels.  If machining particleboard all day long,  a better tool life will be experienced with a carbide grade composition that is designed to be more corrosion resistant.  It is a good idea to let your tool supplier know what material you are machining so the proper carbide grade/tool can be recommended.  Particularly with very abrasive laminates or melamines (such as white melamine), we have recently introduced our "Xtreme Life" carbide grade that often provides in excess of 50% longer tool life!  

 

Question: 
Why does a 3/8” solid carbide bit with a ½” shank cost so much more than a 3/8” shank bit?

Answer: 
Since the carbide rod that a bit has to be produced from, is determined by the diameter of the shank, if you want a ½” shank it requires a ½” rod and much more grinding to turn a 1/2" rod blank into a 3/8” cutting diameter.  If you are ok with a 3/8” shank, the machining process is greatly reduced and, additionally, the 3/8” rod costs less than a ½” rod.

 

Question: 
Can I machine plastic with a standard spiral bit? 

Answer:
While, for instance, you can machine solid surface material with a standard up-shear spiral bit, generally for machining plastics an O-flute Bit is recommended.  For flexible plastics the O-flute Bit should be a straight cutting edge, and for the more rigid plastics, an O-flute Upcut Spiral Bit is the best solution.

 

Question: 
Will I get a better finish with a 3 flute bit as opposed to a 2-flute?

Answer:
Not necessarily.  While many believe that three flutes will cut better than two flutes, it’s a fallacy.  What determines the best finish and better tool life will depend on whether you are producing the ideal chip load based on the tool design (i.e. number of flutes), the feed rate and the rpm of your router motor.  Ideal chip load varies depending on the material being cut.  If your chip load is too small for the material you are machining, you will generate a lot of heat and it will cause the cutting edge to deteriorate prematurely.  Of course, the tool life is not determined by the cutting tool alone.....the machine spindle bearings, the tool holder, the collet and the collet nut all play a role as well.

 

Question:
What causes my router bits to break?

Answer:
When router bits break, they usually do so at the weakest point of the tool which is directly below the shank.  Generally, there are tell-tale signs that give a clue as to why this happens.  The reason bits break is usually found in the following:

  1. bad collets
  2. incorrect torque
  3. tool slippage (as a result of using a static collet nut)
  4. incorrect clamping (too much shank protruding from the collet)
  5. incorrect chip load
  6. movement of the work piece
  7. vibration in the cut due to inadequate hold-down
  8. incorrect use of the bit (putting too much pressure on the tip, such as cutting a ¼” rebate with a cut length on the tool of 1.5/8”)

 

Question: 
Can I drill with the up spiral router bit?

Answer:
Router bits are designed to move forward while cutting.  If they are used to drill holes they will create an excessive amount of heat generally leading to burning and breakage.

 

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