Cut into a Parf Dog

[GoingMyWay]

When I originally made my custom tracksaw cutting station I followed Peter Parfitt's advice and made sure not to drill a hole that would fall directly in line with the tracksaw cutting path.  My custom tracksaw cutting station was made out of a 2' x 4' piece of MDF and I set it up to allow me to make my cuts along the shorter 2' side.

This past weekend I started building my end grain cutting board using pre-milled 21" long lumber. I figured it would be easier if I was making my rips along the 4' side of the station. I had already pre-drilled the full pattern of 3mm holes so it took no time at all to add several new 20mm holes along the longer side of the cutting station where I thought most appropriate. In my haste I didn't really stop to think about where the parf dogs might be in relation to the guide rail.

Sure enough I had not only drilled a hole but also actually placed a parf dog right into the cutting path of my TS55 with the 48 tooth blade.  After my first cut in the new orientation I sadly discovered that I had ever so slightly hit the parf dog. I casually inspected the blade and didn't see any obvious signs of damage. I probably should have taken the blade off for a thorough inspection, but I didn't and I continued on making lots more rip cuts. These cuts seemed fine. 

Since I didn't see any obvious damage and the subsequent cuts seem fine I was guessing that the stainless steel was soft enough not to hurt the carbide.  You can kinda see the nicked parf dog in the attached picture.

Think my blade is ok or did I mess it up?

 

[Cheese]

I thought most dogs were fabricated from aluminum or delrin.  If these are truly fabbed from SST, then I’d examine the blade very closely. I’d check each tooth looking for any chipped carbide teeth. 

FWIW...I find it rather bizarre that anyone would fabricate dogs from stainless, because sooner or later they will end up in the pathway of a TS at full churn. I love stainless but I just don’t think this is a great application for the material.

 

[GoingMyWay]

I double checked the product description and it does say stainless steel:http://www.leevalley.com/us/garden/page.aspx?p=71185&cat=1,41637. I guess I better take the blade off for a closer look. I'm afraid what I'm looking for won't be that obvious to me though.

This is my first time using any kind of dog like this so I hadn't even thought about the ramifications of accidentally cutting into a plastic vs a metal dog. I guess I don't feel so bad that it happened to me so early on since it was likely going to happen at some point as you pointed out.

 

[Scorpion]

IIRC, Veritas makes their dogs out of Stainless.  I agree with Cheese, I’d prefer sets out of aluminum or delrin.  2 reasons: 

(1) They’re much cheaper than a blade so I’d rather wreck a dog than a blade

2) I’d argued that a cut dog would still probably function just fine for the most part so cutting a dog softer than the blade might not have I’ll consequences to either the blade or the dog. 

Edit:  to answer your question - check your blade carefully.  The blade can lose a carbide tooth or have chipped ones and you might not initially notice when cutting.

 

[dltflt]

Carbide is brittle so you need to look for hair line fractures that may come apart at a later date.

 

[Cheese]

Ya thinking through this...remove the blade and carefully clean it to remove any built up gunk. 

Then take a magic marker and mark any tooth. Carefully check each tooth starting from the marked one. Look at both the top grind and at the edges for any chips in the carbide. I’m certain that if any are chipped/cracked/broken you’ll be able to identify them easily.

Mark any damaged tooth with the marker to help assess what the approximate cost will be to put it back into serviceable condition. Saw blade reconditioners usually charge some $ figure per tooth to detach damaged carbide inserts and replace them with rebrazed new carbide inserts. If too many are damaged, it’s just cheaper to purchase a new blade.

If this blade needs to be serviced, I’d suggest you contact Leitz as they are the suppliers of original Festool blades.
http://www.leitztooling.com/services.htm

 

[GoingMyWay]

Thanks for that suggestion and the link to Leitz.

 

[GoingMyWay]

I cleaned the blade this morning and checked all 48 teeth - 2 times.  The only thing I noticed was one tooth that had a shiny spot at the tip.  I couldn't detect any cracks there or anywhere else.  I've attached a picture showing the shiny spot on the tooth.  It may be hard to see in the picture.  It was a little hard to see even with the naked eye in person.  I've also attached some better images showing the damage parf dog.

 

[jeh]

Ya thinking through this...remove the blade and carefully clean it to remove any built up gunk. 

Then take a magic marker and mark any tooth. Carefully check each tooth starting from the marked one. Look at both the top grind and at the edges for any chips in the carbide. I’m certain that if any are chipped/cracked/broken you’ll be able to identify them easily.

Mark any damaged tooth with the marker to help assess what the approximate cost will be to put it back into serviceable condition. Saw blade reconditioners usually charge some $ figure per tooth to detach damaged carbide inserts and replace them with rebrazed new carbide inserts. If too many are damaged, it’s just cheaper to purchase a new blade.

If this blade needs to be serviced, I’d suggest you contact Leitz as they are the suppliers of original Festool blades.
http://www.leitztooling.com/services.htm

US Service Centers:
http://www.leitz.org/weltweit.html?cont=7&count=162#cont

 

[Stone Message]

The choice of stainless steel for the Veritas Parf Dogs was carefully considered as it has a number of advantages over aluminium.

The whole concept of the Parf family of products is to get the best accuracy possible with a tracksaw on a cutting station. If you drop an aluminium dog onto a concrete floor then there is a chance that it will get a ding on the edge of a round section and not go into a 20 mm hole. I suspect that more people drop their dogs on the floor than saw into them.

Accidents can happen yet we have chisels, screwdrivers, squares and all sorts of other steel tools on the bench.

It was a bit of bad luck for the OP but it his mishap will not make any difference to the material or philosophy behind the Parf range of products.

The OP posted this out of interest and as a caution to others. The latter point has been clearly stated. Aluminium is an easier material to work with and it can be decorated, through anodising and dye, to look jolly interesting but is remains a softer and less robust material for accurate service over the lifetime of the purchaser.

Peter

 

[Michael Kellough]

I'm with Peter, for the intended function ss is the better material for dogs. Just be careful with cutting tools.

 

[daveg]

I also think SS is a good choice for Parf Dogs. When we work with almost any machine, we have to be as diligent as possible to account for scenarios like those of the OP. I'd use this as a good learning experience. The outcome only cost a relatively small amount. No injuries is a good thing! My guess is the OP will be a much better woodworker in the future.

 

[ben_r_]

Yep, wouldnt have bought aluminum ones myself. I like SS when available.

 

[Svar]

I'm with Scorpion on this one. SS costs more, but other than being shiny it offers no tangible advantage over aluminum for this application. SS dings almost as badly when dropped on concrete floor. Try it. Yes, its harder, but heavier and will have three time the kinetic energy upon reaching the surface. Precision? Give me a break. Your guide rail is aluminum, and so is your saw, MFT, and a fancy Woodpecker square. Oh, and you stick those dogs into MDF! The threads will hold up better in SS though, but that's it.

 

[pixelated]

About a year back, I accidentally cut through two #8 stainless screws that were in a 2x4 I was reclaiming/repurposing and cutting to size on my 12 inch miter saw. I couldn't find any visible damage on the blade, but there was a noticeable difference in the cut quality afterward. YMMV

 

[GoingMyWay]

I noticed that I started getting some saw blade swirl marks on my cuts after I hit the parf dog, but I think that was the result of the combination of me taking multiple passes at various depths to try to avoid the saw kicking back and not having the guide rail clamped.  Unfortunately, I had only made a few cuts (with a "loose" un-clamped guide rail) before I hit the parf dog so I don't really have a good baseline of how the saw was cutting before my mishap.

Yesterday, I bought 2 Quick Clamps so I could securely clamp the guide rail to my cutting station.  I was then able to cut full depth into both 1.75" thick maple and purpleheart in a single pass with only the tiniest amount of swirl marks and no kickback.

After my careful inspection, I think it's safe for me to continue using the blade as is - that is unless any one thinks there could be major safety concerns.

 

[Cheese]

Ok, seeing as it was probably my statement that started this aluminum vs stainless debate, I need to weigh in. Thus far, I’ve yet to see a compelling argument brought forth as to why stainless is a better material to use for dogs than aluminum, other than there is a lot of love   for sst.

I completely understand why people prefer sst dogs  ... personally I prefer sst for just about everything in life, however in this instance the use of sst over aluminum just doesn’t make sense. It’s really a materials science issue.

These MFT’s are traditionally manufactured from MDF. However, with the proliferation of personal CNC machining centers, and the inclusion of various materials into other custom MFT formats, there is no longer a standard from which to develop a universally accepted standard hole size. 20mm means what? 20mm + something and - something? Or 20mm + something and minus nothing...you catch my drift.

20mm drill bits, 20 mm Zobo bits, 20mm router bits, 20mm Forstner bits, the method that CNC uses, to drill a smaller hole and then enlarge it, they all produce 20mm diameter holes, more or less. So to say that a stainless dog is the solution for accuracy is just not reality.

Stainless and aluminum can both be CNC machined to a consistent +/- .001 tolerance so the material itself isn’t the issue.

So if you are inserting and removing a dog (aluminum or sst) from a hole, and assuming that the MDF will be eroded by a factor of X, the consequent abrasive wear on the dog itself, will probably be in the 10,000:1 range for aluminum and likely in the range of 100,000:1 for sst. What all this means is that the MFT hole sizes will grow significantly before the aluminum dogs wear significantly.
The old wives tale still holds true, what’s the weakest link in the chain...the MDF substrate . The stainless dogs will not cure the ill.

 

[Stone Message]

I take ( [member=44099]Cheese[/member]  )  points but there is one issue that has not been mentioned. Anodizing alters the dimensions of aluminium by a fraction. It is significant as we had to look very carefully at this with the 25 mm holes (which are anodised inside) on the 20 mm Guide Block of the Parf Guide System. The thickness of the anodizing can vary from one batch to another. Anodizing will wear in time as well.

You mention all the variations on "20 mm" for the hole sizes. You are right to point this out and Lee Valley understood this when they began the manufacture of the tall and short Veritas Parf Dogs. When the Parf Guide System was being developed the "20 mm" cutter had a lot of thought and prototyping in order to get it right. You will find that all the Parf products use that drill as the definitive standard for all tolerances on the other components and for the new Parf Super Dog.

Peter

 

[Cheese]

Hey Peter,
Approaching this from a strictly analytical perspective, I take note of your statement that the anodization process impacts the dimensional properties of the aluminum dogs. However anodization, whether purely decorative or functional (hard coat), will only tweak the final dimension in the realm of .0005/.001”. That’s approximately in the 012/.024mm range.

We’re talking about 1/6-1/3 the thickness of a human hair. That’s certainly within the range of discrepancy of a typical 20mm boring tool, no matter what form it takes.

So, for all the various reasons and conditions stated above, I really like the new Parf Super Dogs, because they make
the above issues all non starters.

 

[bnaboatbuilder]

Regular Veritas Parf dogs are undersized to start with, honestly too small at 19.88mm. I make my own aluminum dogs, 7 or so now. No need to anodize them for my purposes and i can size them correctly which is better at 19.96mm.