Made some MFT dogs

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Scorpion

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Was reading Sapper's thread about some dogs he has maybe not being machined correctly.  About a year ago I ordered some 6061 aluminum rod so I could make a set so I decided to make a set and run some experiments on my MFT to see if you can actually get things square using dogs.

The material I'm using is 7/8-inch 6061.

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I setup the stop on the lathe to net a 1 1/8-inch cut.

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Let the auto-feed do the work.  Flip end for end and go again.  I'm left with this.

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I then cut them off allowing just more than a 1-inch shoulder.  Repeat the process until the drop is too short for another.  I ended up with 8.

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The next 4 ops are just fiddling.  I knock the edges off with a file from the three shoulders and face both ends.

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Next, analysis...
 
Those are pretty nice.  If you ever consider selling a few I'll take some.  Nice job
 
If it isn't obvious, the process in which I used to machine the dogs is the simplest and most prone to accuracy problems with the end product.  I turned the shank of the dog to the MFT hole diameter and did not machine the head (no skim cut) which relies on the consistency of the diameter of the material AND the accuracy of the chuck on the lathe.

For this exercise I checked all six and found their OD's to be within a thou.  An up-close of one of them.

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In thread, Sapper indicated that the shoulders of the part looked like they weren't even.  Here's a single dog from 4 different angles.  The shoulders look (visually) to be identical.

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If they were machined correctly, there shouldn't be a visible difference from any angle. 

Not to check for concentricity.  I chucked up one of them and set up the dial indicator.  Spun the chuck while the indicator rides on the unmachined surface marking the high and low spot.

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The deviation between measurements is ~.003".  This indicates that the material (extrusion) is out of round.

To verify the part is in the chuck straight (as possible) I move over 1/4-inch and re-measure.  If the part is  straight in the chuck, the measurements will be the same.  They are.

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Without removing the dog from the chuck I relocate the dial indicator to the machined surface and re-test.  If the spots on the machined surface have similar high and low spots then the part is slightly offset in the chuck.

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The difference between high and low now is only .0005".  That means the machined surface is not only in the chuck straight, but machined true.  This also means that the extrusion isn't extremely accurate (as far as a machinist thinks).  As a wood worker, it's darn good.  I ran similar tests with half of the others with nothing interesting to report.

If my dogs are straight, I can assume them a constant and do some hole comparisons on the MFT. 

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I spent about an hour moving around the MFT trying many different locations checking to see if I could get a 3-point test to fail.  Of all of the tests, so only found one on the surface that stood out as suspect.  The pencil is pointing at it in the pic.

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I moved the dogs around it and he led it from all sides. 

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The results are as you would expect if the hole wasn't in the correct location.  I switched dogs out  and rotated them as well to ensure the .003 run out of the dogs wasn't messing the test up.  No matter what I did, I cannot get the square to seat on three points if one of the holes is this one.  I found no others that were obviously off anywhere on the table.

I'd probably recommend checking the holes and dogs to ensure the ones you want to use are straight the first time you use them.  They may not be.
 
Scorpion, I found your post to be very timely... I'm a longtime Festool fan and FOG lurker, but just recently ordered a mini lathe and have started to get into a little machining. I had been thinking of making some dogs as my first project on the lathe. I have a 48"x48" CNC router and machined the same hole pattern as the mft into my spoilboard (to use for hold-downs and alignmnet). I want to make some dogs and other fixtures to utilize on the CNC table.
Would you mind going into a little more detail on how you created the dogs?

Thanks

EDIT> due to thread split
 
ablythe said:
Scorpion, I found your post to be very timely... I'm a longtime Festool fan and FOG lurker, but just recently ordered a mini lathe and have started to get into a little machining. I had been thinking of making some dogs as my first project on the lathe. I have a 48"x48" CNC router and machined the same hole pattern as the mft into my spoilboard (to use for hold-downs and alignmnet). I want to make some dogs and other fixtures to utilize on the CNC table.
Would you mind going into a little more detail on how you created the dogs?

Thanks

Ablythe,

Regarding my post - which part of the process are you interested in?  I'd be happy to break down my steps for you.  Quality dogs are fairly easy to make with a few simple setup tricks but I'm sure I took some of them for granted in my first post.  Contrary to what was previously stated, there is no magic in the design.  Home made is just as good, if not better.  You'll be making them to your MFT, not making them using averages. 

EDIT> due to thread split
 
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