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post #21 of 63 (permalink) Old 02-03-2017, 09:26 PM
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@MT Stringer

I made a drawing and sent it to a local CNC shop - probably less than 10 miles from me - now waiting for a quote. I have been reading posts on Festool forums about hole size versus dog size and that led me to go ahead and order a set of the parf dogs from Lee Valley so I can have them match the holes to the dogs. In thinking though, it would seem that, within reason, a minor difference between the hole and dog shouldn't affect the accuracy as the dog will touch the hole at the tangent point and still have the plane of the dogs perpendicular to the other row of holes - assuming that the holes are all the same diameter.

A thought - a dowel is not necessarily round as there is different shrinkage with and across the grain so it could be a cause of some error. Just a thought.

Last edited by tomp913; 02-03-2017 at 09:29 PM. Reason: Added "A thought"
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post #22 of 63 (permalink) Old 02-03-2017, 10:15 PM
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The difference in size is 20 millimeter which .787 inch 3/4 inch .75 difference is .037 inch . Close equivalent 1/32 is .03125 the 20 mm
holes are bigger by that amount. Parf dogs are bigger than Mikes 3/4 holes by that much. Closes equivalent is 25/32 in US size if you could find a 25/32 router bit it may work don't think they make that size.
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post #23 of 63 (permalink) Old 02-04-2017, 06:05 AM
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@roofner

I was thinking a difference just of thousandths rather than 1/32". On the Lee Valley site, the size of the Parf dog is given as 19.90 mm, and I read somewhere that the tolerance on that size is held to .0005" which is pretty tight. The site also states that the holes in the MFT are 20 mm which would give a clearance of 0.1 mm (.004") which seems reasonable - and the Parf drilling system comes with a 20 mm dia. forstner bit which would indicate that they're shooting for a nominal 20 m hole. Seneca Engineering has published a drawing of the MFT top which shows the hole size at 20.2 mm - this gives a nominal clearance with the Parf dog of 0.3 mm (.012") which I feel is starting to get a little sloppy. Hence the recommendation to provide the CNC shop with the dog that you are planning to use and let them cut some trial holes to establish the size needed.
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post #24 of 63 (permalink) Old 02-06-2017, 01:23 PM
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I had an idea for a substitute for parf dogs if you use 3/4 holes. Go to hardware sections of your home center find some 3/4 id by 1 od by 2 inch bushing using 3/4 inch bolt through the bushing then through your top with a flat wash and nut. The bushing were brass.
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post #25 of 63 (permalink) Old 02-06-2017, 02:31 PM Thread Starter
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Quote:
Originally Posted by roofner View Post
I had an idea for a substitute for parf dogs if you use 3/4 holes. Go to hardware sections of your home center find some 3/4 id by 1 od by 2 inch bushing using 3/4 inch bolt through the bushing then through your top with a flat wash and nut. The bushing were brass.
For me, that might be a good choice. My 3/4 inch holes are exact and the dowels don't fit. But I do have four dogs made on the lathe by a friend. They fit snugly. Maybe a bolt would be an even better fit.

That's my story and I'm stickin' to it!
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post #26 of 63 (permalink) Old 02-06-2017, 04:25 PM
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That's my plan I have not setup the time yet to cut holes.
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post #27 of 63 (permalink) Old 02-07-2017, 07:31 AM
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By the way I did get a pair of the saw horse at Valu home Center for $25 on Sunday. The brand is stanley .
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Last edited by roofner; 02-07-2017 at 08:04 AM.
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post #28 of 63 (permalink) Old 02-07-2017, 10:59 AM
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Tom to drill your holes they need to be between .791 to .795 inches that gives your .004 tolerance. It is not a lose tolerance.
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post #29 of 63 (permalink) Old 02-07-2017, 12:02 PM
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I bought the DXF from MFSlab MultiFunction Slab Work Bench - Multi* Function* Slab for $18. I customized it with an opening to hold a router plate or other use. I plan to make an insert for my Kreg Pocket hole drill, vacuum hold and a vise.

I do not route or cut MDF due to the dust. I also wanted a table that wouldn't be junk after a liquid spill, rain, glue squeeze out or paint, so I chose to put Formica on 3/4" MDO before cutting holes. MDO may look like plywood, but is not. It is the material that outdoor sign makers use.

Major lessons learned; put the MDO on the CNC properly the first time (notice extra holes on left) and test the diameter of your end mills. Picture tells full story of positioning the MDO. Even in the world of +$80 router bits do not expect you are buying NASA precision tooling. This project needs minimal clearance for a precise fit of the inserts and if your bit is 0.001" undersized, then the inserts won't fit. I already have Formica put on another piece of MDO and will cut it after more evaluation of this one.

My shop made (cobbled) router fence uses one of the holes to pivot on and a clamp to hold it in position. Has worked well for couple initial jobs.

After making the slab, I went about looking for gadgets to use on it. I bought some Bessey auto-adjust clamps from Lee Valley which are awesome. I plan to get some of the Parf dogs, wedge dogs and surface dogs.

In hindsight, I saw that Rockler carries a lot of gadgets for 3/4" holes that I would like. I would advise people to look at those offerings before making the diameter decision.

Steve.
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post #30 of 63 (permalink) Old 02-07-2017, 05:10 PM
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For 3/4 holes bolt probably will not work because your hole would have to be .008 min bigger then the hole and no more than .012 bigger at the upper limit. The 3/4 inch router bit is probably very close to .75 inch
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