Dowel jig for 6" square timbers


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Old 06-12-20, 06:48 PM
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Dowel jig for 6" square timbers

I'm planning a dining room table base with 6" square reclaimed timbers. The design includes 2 6"x6x6' horizontal timbers being joined to the 4 6"x6" table legs with 45 degree cuts and dowel joiners. I'm having trouble finding a reasonably priced jig for this. Any ideas?
 
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Old 06-12-20, 06:56 PM
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How big of dowels are we talking about?
 
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Old 06-12-20, 06:59 PM
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Whatever is appropriate for 6"x6" timber, maybe 3/8". I'm not sure the dowel size is relevant. Since dowel jigs are typically made for 1" boards, the issue is the jig.
 
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Old 06-12-20, 07:17 PM
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Ok, forget I asked.
 
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Old 06-12-20, 07:21 PM
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I don't understand. I asked about a dowel jig for 6"x6" timber. I don't understand how dowel size is relevant. Please enlighten me.
 
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Old 06-12-20, 07:28 PM
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Well if you are using say 3/4" dowels it rules out quite a few jigs.
 
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Old 06-13-20, 07:18 AM
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45 degree cuts
Are these mitred joints where the legs join the apron? If the top of the apron is going to be covered by the table top you could avoid blind dowelling with a jig. Instead clamp up the joint and just drill down through the apron with a long bit into the leg for the dowels.

Or make a jig.
 
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Old 06-13-20, 07:30 AM
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I would suggest making your own jig.

OR you will have to pay for a jig.

Example: https://www.rockler.com/self-centeri...-thick-timbers
 
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Old 06-13-20, 08:17 AM
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Thanks so much, great idea. I'm also considering pocket hole screwing because the timbers will be cut 45 degrees to hide end grain. Since the 10'x4'x1/2" glass top will be a couple hundred pounds, do you think dowels or pocket screws would be stronger?
 
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Old 06-13-20, 02:22 PM
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Assuming it is a full mitre and that the top overhangs or is flush with the outside of the legs, the weight of the top will be pressing down on the legs and not on the apron separately. How will the short aprons be attached?

Since the top is glass the dowels will show if you use my earlier suggestion of drilling down. I think that would not be bad looking. Somewhat like a through tenon in Mission furniture. If you want to make it a design element, you could add dowels through the legs into the apron, too. Horizontal dowels will help resist theoretical "sliding" of the pieces in the mitre joint. (However, I also assumed that the joint would be glued so in addition to the weight being borne by the legs pressure to the top of the apron or the weight of the apron itself on the joint is not a concern.)

Either dowels or pocket screws should be adequate. In my opinion if the connections are visible, I would prefer to see chunky dowel ends on a 6 x 6 rather than smaller screw hole plugs.

If you do use a jig, it would be easier to drill the holes for the dowels before you cut the 45 degree mitre.
 
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Old 06-13-20, 02:50 PM
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I apologize for not being clear. Yes, all 4 legs will be secured to the two top beams (aprons confused me) with 45 degree cuts to hide any cut marks.

The table design involves 4 6"x6" legs the top of which are mitred 45 degrees so as to mate with the two 6"x6"x6' horizonal timbers also mitred at 45 degrees such that no cut wood is visible. Then one set of legs and top been will be connected to the other by 3 1"x8"x2' boards that can be either doweled, pocket screwed or both at both ends of each end. The three 1"x8"x2' boards will be placed at each end with one in the middle. I envision placing them slightly below the 6"x6"x6' top beams such that the top beams support all the weight of the glass. In this way the pocket screws would be on the bottom of the two top beams and not be visible.

Does that sound right? Do I need both dowels and pocket screws?
 
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Old 06-14-20, 07:08 AM
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I understood the leg-beam/apron structure as you described it.

Are there 3 1x8s attached to the legs at each end like rungs of a ladder (total of 6)? Or are they attached to the beams (3 only) spaced along the length of the beam and visible through the glass?

In either case I see some structural weaknesses. If the ends are "laddered" then there could be good resistance to side-to-side sway (but relying only on pocket screws) but there is no resistance to end-to-end sway other than the mitre joints which may not be strong enough even if glued and screwed/dowelled. There is a lot of mass in the beams and glass to be offset.

If the ends are not laddered and the 1x8s are attached to the beams, then I do not see how either side-to-side or end-to-end pressure will be resisted and collapse is likely.

Can you provide a sketch?
 

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Old 06-14-20, 09:12 AM
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I'm envisioning 3 boards connecting the two top beams, per the very rudimentary table top view drawing. The 4 legs would be attached per the first drawing with no boards connecting them vertically to maximize the leg room of the two end chairs. The estimated weight of the glass is 280lbs. If you think there are instabilities, what changes would you recommend to the design? The 2nd set of drawings has two braces connecting the legs and beam. Is this enough? Thanks.

 
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Last edited by zich6; 06-14-20 at 12:09 PM.
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Old 06-14-20, 11:53 AM
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I have marked up your drawing to show the problem areas and some suggested solutions.

If you decide to use brackets I would advise that they be heavier than the ones usually found in the big box stores. Steel that is 3/16 or 1/4 inch thick would be my choice. They could be surface mounted or set flush into the beams and legs. If you want them to show as a design element they could be on outside faces. Otherwise hidden on the inside faces.

Many tables with heavy elements use mortise and tenon joints that are very strong and by their nature resist these kinds of forces. Google "trestle table" or "table mortise and tenon joint" for examples.
 
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Old 06-14-20, 12:27 PM
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Thanks, great advice. I think I'll try the 6"x6" braces for the beams and legs. Then find a way to strengthen the cross members. I don't have the tools for mortise and tenon.
 
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Old 12-05-20, 04:07 PM
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Finished the table

Here's how it turned out. Thanks for all the help.





 
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Old 12-05-20, 04:31 PM
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Rustic, yet modern. Looks nice!
 
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Old 12-05-20, 06:45 PM
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Thanks. The design is simplistic maximizing leg room and view of the outstanding reclaimed cedar. I'm happy with the way it turned out.
 
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Old 12-06-20, 07:15 AM
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Looks really nice. Glad it worked out. Thanks for letting us know.
 
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Old 12-06-20, 07:20 AM
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I love this forum because there are great people here that are knowleable and willing to help. I thought you guys would appreciate seeing the fruit of your advice. Btw, the glass is low iron. It's much more expensive than regular tempered plate glass, but much clearer so you can really see the wood grain. Thanks again all.
 
 

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