Page 3 of 4 FirstFirst 1234 LastLast
Results 31 to 45 of 54

Thread: dowel pins too tight (follow up on Jessem dowel jig)

  1. #31
    Join Date
    Oct 2005
    Location
    Camas, Wa
    Posts
    3,853
    Quote Originally Posted by Paulh Tremblay View Post
    They don't. The dowels I used in both tests were Jessem's dowels. I used the bit supplied by Jessem, the 3/8'' size. A Jessem rep has informed me that there is a flaw in the Jessem Jig design, and suggested I return the jig.
    I am getting confused in both of these threads. According to Jessem the "flaw" is not having the 9.7mm drill bit and bushings? So all jigs that were shipped with an actual 3/8" bit and bushings is flawed and should be returned? You should return it even though Bill said that JessEm is offering the 9.7mm by the end of the month? Why did JessEm switch from the 9.7mm to the 3/8"(which I have).?

  2. #32
    Quote Originally Posted by Cary Falk View Post
    I am getting confused in both of these threads. According to Jessem the "flaw" is not having the 9.7mm drill bit and bushings? So all jigs that were shipped with an actual 3/8" bit and bushings is flawed and should be returned? You should return it even though Bill said that JessEm is offering the 9.7mm by the end of the month? Why did JessEm switch from the 9.7mm to the 3/8"(which I have).?
    Here is my take:

    The difference between 9.7mm and 3/8" is .006" (two sheets of rather thin paper). And most people with 9.7mm bushings said 9.7 is too sloppy (and I concur), so many are using 9.6mm bits w/ the 9.7mm bushings. The difference between 9.6mm and 3/8" is .003" (now one sheet of rather thin paper).

    Now, there are a couple of complicating factors, first: Hard vs. soft wood. If you're trying to shove a slightly oversized dowel into a 3/8" hole in hard maple, it is going to be a challenge. Now multiply that because you're creating a joint with several slightly oversized dowels in 3/8" holes, adding glue, ugh.

    But softwood is different. I can tap a slightly oversized dowel into a 3/8" hole no problem-o. Do it in fir and pine all the time.

    And there is a second complicating factor: The dowels themselves. They may be a bit oversized, they may be a bit undersized.

    So as much as people want a guarantee that the holes will always be the perfect size for the dowels, there is really no way you're going to get that. Perhaps if you have a single source of dowels with very high quality control standards, and you can control your own shop environment perfectly, and you only use all hardwood or all softwood, maybe you could do it.

    But if anything changes, like you now want to switch from hard to softwood for a project, or you want to use dowels from a new vendor, well, you're going to have some issues.

    My point is, as soon as you think you have hit the magic combination, one variable can change and you're right back at the starting line.

    So the advice to in these threads to make a dowel-sizing plate from a scrap of steel is (IMHO) the right approach. Sometimes I sand my dowels, it is cathartic. I'm not a production shop, I can fit my dowels. I can take some time and shrink dowels in the microwave or via dowel plate or via sanding. If the dowels on hand are a little small I simply go through the batch to find those at the opposite end of the tolerance spectrum. If I don't have enough, I order more dowels.

  3. #33
    I had some issues with dowel fit but seem to have it in hand now.

    The bits are standard twist drill bits designed for drilling rigid materials like metal. When drilling in wood they don't cut cleanly at the outer edge and push the wood which springs back. So you end up with a small hole which varies with wood species. Try a quality brad point bit designed to cut wood - often solves the problem.

    The dowels are compressed and grow a little after manufacture. Try them in the jig bushing and if they are tight push them through a dowel plate. I use the Lee Valley plate inserts - don't have the plate, just the inserts which fit in a dog hole in my bench. Pushing each dowel through takes off a few thou and gets them to the size they're supposed to be.

  4. #34
    Quote Originally Posted by Cary Falk View Post
    I am getting confused in both of these threads. According to Jessem the "flaw" is not having the 9.7mm drill bit and bushings? So all jigs that were shipped with an actual 3/8" bit and bushings is flawed and should be returned? You should return it even though Bill said that JessEm is offering the 9.7mm by the end of the month? Why did JessEm switch from the 9.7mm to the 3/8"(which I have).?
    I don't know why Jessem switched from 9.7 mm to 3/8''--that is a very good question several of us would like to know.

    [Edit] I am deleting faulty information I had included about Jessem.
    Last edited by Paulh Tremblay; 09-06-2014 at 10:47 PM.

  5. #35
    Quote Originally Posted by John Gornall View Post
    I had some issues with dowel fit but seem to have it in hand now.

    The bits are standard twist drill bits designed for drilling rigid materials like metal. When drilling in wood they don't cut cleanly at the outer edge and push the wood which springs back. So you end up with a small hole which varies with wood species. Try a quality brad point bit designed to cut wood - often solves the problem.

    The dowels are compressed and grow a little after manufacture. Try them in the jig bushing and if they are tight push them through a dowel plate. I use the Lee Valley plate inserts - don't have the plate, just the inserts which fit in a dog hole in my bench. Pushing each dowel through takes off a few thou and gets them to the size they're supposed to be.

    [Edit Getting rid of wrong information about Jessem]

    I can't get a dowel plate and as Bill Huber points out, that is a bad idea, because dowel pins are made with grooves in the side for absorbing the glue, and a dowel plate will get rid of the grooves.
    Last edited by Paulh Tremblay; 09-06-2014 at 10:48 PM.

  6. #36
    [Edit: getting rid of faulty information about Jessem.] Sanding dowel pins, or pushing them through a dowel plate reduces their main feature, the grooves in their sides, so I am not going to do that.
    Last edited by Paulh Tremblay; 09-06-2014 at 10:49 PM.

  7. #37
    My jig works just fine with 3/8 dowels using a 3/8 drill bit. The dowel plate is shaving at max a couple of thou - it doesn't remove the grooves.

    Sometimes I have to do a little adjusting of dowel and/or hole - that's woodworking. A dowel with a kerf and a little strip of sandpaper makes a small flap sander to clean a hole. Lots of simple, quick solutions.

    Using high precision drill bits, reamers, and precision dowel pins is metalworking.

  8. #38
    If the dowel holes are full of glue with no air space it will take a lot of force for the clamps to pull the joint together and the wood will split from the hydraulic pressure.

    Don't need much glue - just a surface wipe in the hole and on the dowel.
    Last edited by John Gornall; 09-06-2014 at 9:31 PM.

  9. #39
    When I got my Jessem dowel jig a couple of months ago it happened that we were renovating at my shop. Needed sink and 3 upper cabinets in the lunch room. I usually rabbet, glue, and staple cabinets but decided to use dowels. Cut the panels, edge taped them, laid out the dowels, drilled with the jig, and glued them up. Perfect, no thoughts about drill or dowel sizes. Dowels from Lee Valley. If I had assembly problems I would have adjusted the dowel size - dowel plate - sanding - squeeze in vise whatever. Chasing drill size just makes it hard. Just do some woodworking. MDF may be your problem - try some real wood.

  10. #40

    Good info on dowel fit

    I found two good sources on how dowel pins should fit. They sources actually contradict each other, but still shed light on the problem.

    First, this from an interview with Jim Lindsey, the maker of Dowelmax:

    The 1×6 had six dowels in it and i pushed it together without glue and it is still together and that was 12 years ago. It would not come apart. I would have to have broken the wood to get it apart and that’s when I realized I had a problem. I did some research after that and discovered that a 9.7mm drill ...But as we went on through the years, what we found is the dowel sizes vary from company to company. You know, they give you all sorts of excuses that they can only go 5 thou, plus or minus 5 thou which is of course 10 thou and that can be problematic so Mike and I started looking at it again and did some research and thought that possibly the 9.6 might have been better rather than the 9.7 because it was more of a median size.
    http://thewoodworkersnews.ca/2014/05...-the-dowelmax/

    And this from Laurier, a maker of dowels:

    The dowel pin should be the same size as the drill used to make the hole. It is normal to use clamp pressure or a dead blow hammer to assemble a joint. In a properly fitted joint 2 to 3 dowel pins per joint is normal.
    http://www.laurierwoodcraft.com/3648/sizing
    Last edited by Paulh Tremblay; 09-06-2014 at 11:38 PM.

  11. #41
    Join Date
    May 2005
    Location
    Highland MI
    Posts
    4,511
    Blog Entries
    11
    Quote Originally Posted by Paulh Tremblay View Post
    [Edit Getting rid of wrong information about Jessem]

    I can't get a dowel plate and as Bill Huber points out, that is a bad idea, because dowel pins are made with grooves in the side for absorbing the glue, and a dowel plate will get rid of the grooves.
    A dowel plate only shaves a few thousandths off the pin, not nearly enough to remove the grooves. And the grooves serve two purposes: primarily they allow excess glue or air to escape, avoiding a hydraulic lock as the pin is driven home, and secondarily they give the dowel wood somewhere to go when it expands from the glue's moisture.
    NOW you tell me...

  12. #42

    loose fit dowels make strong joint

    I found this interesting article on glue strength:

    http://www.oldbrownglue.com/images/a...urGlue_FWW.pdf

    An important point is that a slightly loose fitting joint is only slightly weaker than a snug or tight one. That fact explains why a 9.7 mm drill bit will produce strong joints.

  13. #43
    The compressed dowel people - dowels for 9.7 mm drill and smaller dowels for 3/8" drill - read their "Helpful Information" page -

    http://www.justjoinery.ca/

  14. #44
    Quote Originally Posted by Paulh Tremblay View Post
    I found this interesting article on glue strength:

    http://www.oldbrownglue.com/images/a...urGlue_FWW.pdf

    An important point is that a slightly loose fitting joint is only slightly weaker than a snug or tight one. That fact explains why a 9.7 mm drill bit will produce strong joints.

    Very interesting. The company offers dowel pins for 3/8'' bushings and 9.7 mm bushings. The information on the fitting is the same exact I quoted above, about using a dead blow hammer or clamps. I do wonder if using a dead blow hammer would split joints made from MDF.

    Thanks for the info.

  15. #45
    Could the 3/8 inch Jessem guides be drilled out to 9.7 mm?

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •