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Thread: Hoffmann dovetail?

  1. #1
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    Hoffmann dovetail?

    Anyone use the hoffmann dovetail keys for face frames or possibly millwork? Any advantage over pocket screws?

    Basically why would you use the keys over the other options.

  2. #2
    Its a production tool and the answer as to why it is used boils down to, speed, operator skill level, and overall cost per joint.
    It does whats is supposed to do which is join to piece of wood together.

  3. #3
    They sell two types it seems. The plastic ones are the structural ones. The hard wood ones are not structural. In fact, they are cut so the end grain is the show face. That will make a very weak key that you could snap in your hand. I am used to bow ties having the grain running the length of the key.

  4. #4
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    Quote Originally Posted by George Makra View Post
    Its a production tool and the answer as to why it is used boils down to, speed, operator skill level, and overall cost per joint.
    It does whats is supposed to do which is join to piece of wood together.
    Speed and cost per joint seem to favor screws.

    The keys are more expensive than screws and the need to cut a matched pair of dovetails in both parts of the joint doubles the processing time not accounting for any marking or alignment setup. I suppose you could gain some of that back during assembly as its already determined vs time spent to locate both parts for screw assembly. I guess it's cheaper initially than a pocket hole machine and ff table, ignoring operating cost.

    I might pick up some keys and just try it out for myself.

  5. #5
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    Cost per joint: in a production environment 'cost' includes things we don't think about in one man shops or where high end custom work is done. A machine that a part-time college kid can be taught to run in a short time, on the job, is a money saver.
    ďFalsehood flies, and the Truth comes limping after it,Ē
    -Jonathan Swift

  6. #6
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    I would think Hoffmann dovetail might not be as effective as pocket screws for face frame construction. I have one that we use for mitered joints and it works well for that. Especially joining curved mitered glass beads to straight. I have no experience with pocket screws but most pro cabinet shops seem to prefer this method. I have joined a few butt joint frames together with the Hoffmann just to see how it worked and more for the decorative effect. It does go together nicely but think you would need a Tiger Stop or similar stop system to be effective on the inside rails.

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  7. #7
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    The Hoffman is brilliant for miters (the stop is easy to use and consistent), but because you need to precisely locate half of the joint in each part it doubles the chance for errors. I used to have one with a laser line to locate the dovetail for face frames, but that wasn't really accurate enough for some work. YMMV

    With pocket screws, you just machine one part and can then locate it precisely before fastening. If you apply glue to the end grain twice so that it doesn't get wicked away, the joint is very strong. I've tested joints to failure and found that the long grain will actually break away.
    Last edited by J.R. Rutter; 01-20-2020 at 1:36 PM.
    JR

  8. #8
    Whatís the best way to avoid splitting in hardwood with pocket screws? Iíve not had much luck with the narrow face frame stock and location of screws near the end of stiles, even with fine threaded screws.

    Iíve predrilled the mating piece after marking the entry location, but this defeats the efficiency.

  9. #9
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    Is anything faster than pocket holes? Plus, since the face frame is attached to the cabinet case and pocket hole joints are fairly strong to begin with, face frames seem to be an ideal method for face frames. I've used others, including mortise and tenon joints and the Domino. For me, nothing is easier than pocket holes . . . not as satisfying but easier and faster.

  10. #10
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    Quote Originally Posted by Eric Schmid View Post
    What’s the best way to avoid splitting in hardwood with pocket screws? I’ve not had much luck with the narrow face frame stock and location of screws near the end of stiles, even with fine threaded screws.

    I’ve predrilled the mating piece after marking the entry location, but this defeats the efficiency.
    How narrow are your rails? I wouldn't say I've never had that happen but its rare. I dont go below 1&5/8" though.
    Last edited by Jared Sankovich; 01-20-2020 at 4:19 PM.

  11. #11
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    Quote Originally Posted by Eric Schmid View Post
    What’s the best way to avoid splitting in hardwood with pocket screws? I’ve not had much luck with the narrow face frame stock and location of screws near the end of stiles, even with fine threaded screws.

    I’ve predrilled the mating piece after marking the entry location, but this defeats the efficiency.
    An "aircraft" drill bit is long enough to drill through the pocket holes and into the stile while they are clamped. Of course, having both a drill and a driver is needed to make it efficient.
    JR

  12. #12
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    Quote Originally Posted by J.R. Rutter View Post
    An "aircraft" drill bit is long enough to drill through the pocket holes and into the stile while they are clamped. Of course, having both a drill and a driver is needed to make it efficient.
    JR,
    Is that a common occurrence for you? I could see it being dependent on wood species?

    Nice tip about the aircraft drill bit, never thought about them in this application.

  13. #13
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    Not very common. It does depend on species. Dense and brittle woods just want to split in spite of the self-drilling pocket hole screws. Years ago, we did a lot of jatoba kitchen work and had to pre-drill every pocket hole.
    JR

  14. #14
    Aircraft bits are a good solution. Is one screw each side enough? Usually use two to keep the pieces from rotating. The one closest to the end of the stile is the bigger problem.

    Iím finishing up some matching cabinets for a kitchen built in the 50ís. Not exactly face frame and not exactly euro, hybrid. The frames are birch, which is brittle. The last set I did, the frame is only 1 1/8, so just used glue and clamps on these. Current set has 1 1/2Ē frame and cabinet is being built in place so was hoping for the ease of pocket screws. Iíll try pre-drilling the mating piece.

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