[member=4518]Mike Goetzke[/member] and others:
Dog selection criteria, in addition to the comments before in this thread, include additional considerations:
1. The dimensional accuracy and tolerances of the 20mm patterned workbench
2. The trade -off between super-precision and practical utility.
Point 1: Dimensional workbench top accuracy - not all workbench tops are equally or even consistently precise across the entire surface. This means that the DOGS and other tools connecting to the hole pattern need to take this variability into account. If you have a precision 20mm top via CNC Router or Parf Guide Mk 1 or Mk 2 you can be well served by the Parf Super Dogs we stock and sell along with TSO’s CF-Dog series which duplicate the dimensions and Close Fit (CF-) tolerances of the Parf Super Dogs. As Peter Parfitt has pointed out, these Dogs fit very snug – enough so that Peter has come up with a “dog extractor” shop built accessory (Parf Workshop Notes # 23). Our trademarked DoubleGroove™ Dog collars are designed to make extraction easier without a separate accessory. This kind of a tight fit may not always be helpful, however.
Point 2: Practical Utility – applies not only to the Dogs but also to the workbenches including the MFT/3. Many of the uses of these tops do not require and do not benefit from hyper-precision. More is not always better.
For this reason, we also offer a DoubleGroove™ Dog family (non CF-Dogs) with dimensions and tolerances more user friendly for all round woodshop applications but still quite capable for all but the most critical applications.
Judge for yourself – risk free: If you’re not sure, you buy a set of each including Parf Super Dog and compare. If you don’t find any of them useful, simply return to us – no problem.
You’re the best judge of what is right for you [smile]
Hans and Eric
PS: to clarify - the 20mm drill bit/cutter: TSO stocks the UJK 20mm CentroTec shaft cutter with lead-in tip designed to follow the 3mm pilot hole.
We are not a FESTOOL dealer