Revision Dogs from Parf: A must have!

[@ealdydar]

No one should waste there money on any other system. The UJK Park Guide system is hands down the best. I wasted my money on the Trend and Woodpecker jig. 110% happy with the UJK.

[@ThekiBoran]

I have the Mark II, I didn't try hard but it's off a bit. I should say that half of my 4' x 8' work top is highly accurate and the other half is a bit off, by at least a mm.

[@misterm7086]

Off topic, where did you purchase the orange casters?

[@stefanlippert742]

Hey Paul, is there a specific reason why the 2 outer rows are not 96mm apart from each other on all of your benches? Thanks for introducing the revision dogs, they are a great addition to UJK Parf system!

[@TheSmartWoodshop]

Over my years of using the MFT layout, I found that having an extra set of holes 32mm in from the edge very useful for clamping and attaching various jigs like my Paulk Smart Cut (PSC). Ron

[@stefanlippert742]

@@TheSmartWoodshop Thank you and sorry for the confusion of your first and last name ;)

[@Marcel41021]

Would you describe examples when you needed the 32mm spaced holes?

[@TheSmartWoodshop]

The holes all around the edges of all of my benches, router tables, extensions, miter extensions. and more...I had a work around in the past to get these, but this is much quicker and hands down more accurate.

[@ThekiBoran]

I think a big reason is if you're using the Parf super dogs and a track. Mine are offset by 48mm, the offset makes it so your track saw blade doesn't cut through any of the 20mm holes in the middle of the table. See Peter Parfitt, he explains things very, very well.

[@ThekiBoran]

If you only use rail dogs your saw won't cut into any of the 20mm holes.

[@4570Govt]

Ron, I make custom soft goods(mostly bags and cases). I’m just getting into woodworking, having just purchased an HKC55 and a 1400 rail to supplement the FSK rail it came with. I’m making a rail storage case for the 1400 rail, since I’m planning to purchase a second one soon. While this is primarily for my own needs, to protect my own rails when I’m not using them, but I know others might find interest in them. Would you be interested in beta testing one for me? I know you have the longer 2700 rail, but for more “mobile” guys like me who don’t have the space to store a 2700 rail, so we use rail connectors and two 55” rails. Feel free to let me know, and how we can coordinate if you’re interested. Thx, Dan from “Stone Photo Gear”

[@hmbwoodman9444]

I don't see the posted link that you mentioned for ordering the Revision Dogs.

[@TheSmartWoodshop]

tsoproducts.com/tools-equipment/ujk-parf-revision-dogs/

[@Tensquaremetreworkshop]

Many have found that this system is NOT as accurate as CNC. If you complain to the manufacturer, they will list all the steps and the tolerance in each. Result is that they do not guarantee the resulting accuracy. 'Revision dogs' a revision to the design to fix a design fault. When I built my own jig, I did not make that mistake- the design incorporated such a part- which removes the need for one of the drill guide bushes. Wood workers should talk to machinists about tolerances. Words such as 'perfect 90deg' and 'no slop' will cause them to smile wryly. Everything has a tolerance; and they add up. e.g. it one ruler is 1 degree (C) warmer than the other (held in the hand slightly longer) for a single hole then you fail CNC accuracy for everything that follows. Remember, what you are doing here is not woodwork, it is machining (cutting to tolerance using jigs). Technically it is toolmaking. In truth the accuracy actually needed for woodwork is not great (which is why these systems are widely used), but it is not helpful for people using these jigs to pretend accuracy that is not attainable. Even the manufacturer says so. For those interested- The accuracy of jigs needs to be at least 10 times the desired result. CNC is widely quoted as 0.01mm. So we need to e.g. drill holes to an accuracy of 100microns (because the errors can add across the table- each hole is referenced to a previous hole, not to a work zero). That is spread between the plugs in the locating holes (both the hole and jig in each case), the drill bush, the drill to bush, axial alignment of the jig, thermal movement of the jig and the table itself, and a host of other issues. (Remember there has to be clearance for the drill to rotate in the bush). We can stop there. It is not possible.

[@daversj]

I have a CNC mdf top and the holes are f*cked. I used it as a template for my bench and neglected to check it first. Holes are out 1/16” at 3’ and i cant use them to make square cuts. Now i need to route off the old top and make a new one, $65 for the plywood and 3 hours work. There are some garbage CNC machines out there.

[@Tensquaremetreworkshop]

@@daversj Yes, there are. But referencing them surely assumes a calibrated correctly functioning machine. Many woodworkers struggle with CNC machines- because their use is machining, not woodwork. Machinists understand tolerances, and the way to achieve them (they live with them every day) and relax when machining wood. Its inherent properties make it like machining Jello- it is moving all the time, mainly from humidity, and in a non-homogenous way. Claiming metal-like tolerances (easy to find MFT users claiming 0.01mm) just displays ignorance of the factors involved. Because CNC machines reference work zero, the tolerance to any hole is on an absolute value. Jigs such as the PARF system are incremental, so each tolerance is on a relative measurement, which will be subject to the sum of errors up to that point. Error bands expand in a random manner, and accuracy is lost. There is a very good reason why the original MFT by Festool does not use the holes to establish cuts- both the fence and the rail are referenced to the aluminum frame of the table. Toolmakers are engineers. My own table is Birch ply, cut using a Birch ply template made with a CNC calibrated immediately before. Every hole is finished with an engineer's reamer. Is it perfect? Nope. But it was cut more accurately that the material will be able to maintain, and that is as good as you can sensibly get. After all, it is for cutting wood. Which will move afterward, over the months and years...

[@andrewmcgillivray1881]

we often forget that we are woodworkers. i was a pattern maker in a foundry. that's about as precise as can be for woodworking and yet there were acceptable tolerances. the world has gone parf-crazy. wood will move more than that after a summer shower or a hot day in august. i admire the dedication to excellence, but sometimes this is at odds with the nature of craftspersonship (never thought that i'd ever write that...). david pye would turn in his grave, even without a lathe. My dad bought a PoS tablesaw from a building center, he paid 75,00 bucks for it and complained that it was inaccurate. the saw was way more accurate than he ever was.... nuff said. keep on parfing!

[@Tensquaremetreworkshop]

@@andrewmcgillivray1881 Agree 100%. Simple fact is that if you build tools, measuring equipment, jigs or fixtures out of wood you cannot expect accuracy. Way back there were wooden rules, planes, spokeshaves, etc etc. They were all replaced by metal for very good reason. Tablesaws are reckoned better with cast iron tables- so even cast alloy is not good enough. Yet folks want to use wood?

[@KarlCaillouet]

Can't argue with any of the above. That said, there are at least two principles that will assist in maximizing accuracy when dealing with fabricating in a medium (wood) that is inherently subject to a variable like RH (relative humidity). ~ Use the same device (tape measure/ruler) for layout in the project. ~ Batch cut all parts in the project (make all cuts of a certain dimension before moving a reference edge/surface/fence). The accuracy, careful application using the math behind the Parf system, combined with the above two principles is certainly sufficient for all woodworking tasks, IME.

[@RobyWanKenobi]

How do you store your parf guide?

[@TheSmartWoodshop]

I made up a tube with 3” pvc and two caps. I glued one cap to the pipe.😎🤙

[@richardtullius6419]

TSO is out of them again.