Entry hall table for a niece: Part 11

[Derek Cohen]

The process of attaching of the legs was completed by the addition of two screws in the sliding dovetail base. 

Why add screws? The screws are not to prevent the base sliding back (an elongated hole actually encourages this). It is just to prevent the base twisting in, and breaking out of, the socket since there is no glue there to prevent any lateral movement.

The force comes from the splayed and angled legs. They will want to cant outward, and this becomes more so when the three drawers are filled and a vase of flowers is placed on the top of the table.

I thought that it is worth mentioning the screws used and how they were inserted.

The screws are 1" long brass tapered wood screws. The drill bits are also tapered to match. These ones include a countersink and depth stop.



The plan is to drill the hole for the screw through the base and into the case, and then widen the hole in the base. This will permit the base to move with expansion and contraction. In this case 2mm each way.

A wider drill bit (and depth stop) ..



Before inserting a screw, especially brass screws, they are dipped in a little wax. This is wax for lubricating bandsaw blades ...



Here is the widened hole ...



The gap around the screw ...





The second screw is on the other side of the leg. This is positioned about half way between the end screw and the glued toe.



Regards from Perth

Derek

[C. in Indy]

Nice technique and solution!

Now,  just as I commented over on Part 10,  I see you really do have brass ones!   


Chris

[grwold]

Why add screws? The screws are not to prevent the base sliding back (an elongated hole actually encourages this). It is just to prevent the base twisting in, and breaking out of, the socket since there is no glue there to prevent any lateral movement.

Derek, because you mentioned an elongated hole I expected to see you widening the hole in the base only on the long dimension.  Yet you used a larger bit, enlarging the base hole laterally as well.  Do you find the screws' compression to give enough of the lateral support you're looking for?

[Derek Cohen]

The widened hole is to allow for expansion or contraction. The sliding dovetail will only permit movement along its axis (the screw holds it flat, so lateral movement is not possible). As a result, the widened hole is the same as an elongated hole, and easier to make.

With the screws in, I could feel that the structure was tauter than before.

Edit: The choice of screw came up, and I have been pondering on this. I must admit that I chose the screw first as a wood screw and that it could be recessed out of sight. My thoughts were on a wider hole for movement, and did not consider whether the conical countersink would limit movement. The answer is "I don't know" whether it will do so. To be safe, I plan to swap out the screws for round heads, and shape the countersink into a flat (using a wider forstner bit)

Regards from Perth

Derek

[hbmcc]

Did you steal a piece from your son's tool box? The color of that chuck looks a lot like his favorite [block] plane. 


On a serious note, won't the split on the frame bottom continue to separate? .... Not knowing Jarrah.

[Derek Cohen]

 ... On a serious note, won't the split on the frame bottom continue to separate? .... Not knowing Jarrah.

Bruce, it is not a split in the board. It is a gum fissue - common in Jarrah. No loss of strength, just not as pretty to look at ... which is why this board is underneath the case.

Regards from Perth

Derek

[Derek Cohen]

Okay, so I decided that the wood screws were a mistake. They would prevent movement rather than permit it. So they had to go.

This is the exchange screw: a 12 gauge stainless steel wood/metal screw with an all-important flat/domed head.



The plan was to use a 3/4" forstner bit. This would leave a wide, flat area for the screw head to move along. The range of movement would be the same as before, about 2mm each side of the screw.

A MDF template was made to guide the forstner bit, as it had no support in view of the existing hole ...



Drilled to depth ...



A steel washer added ...



Done ...



I had only 15 minutes after work today, but on the weekend, when I get back to this build, I plan to add a third screw behind the front leg.

Regards from Perth

Derek

[mdhills]

Bruce, it is not a split in the board. It is a gum fissue - common in Jarrah. No loss of strength, just not as pretty to look at ... 

That's just today's sensibility talking.
I expect to see a line of "fissure furniture" to sweep the show podiums in a few years...

Matt

[Derek Cohen]

I put the last screws in after work. That will free up this weekend to concentrate on building the drawers.

There are three screws. The one at the toe is fixed and there is no play for any movement. The two at the rear can slide 2mm each way.





Regards from Perth

Derek

[hbmcc]

That's just today's sensibility talking.
I expect to see a line of "fissure furniture" to sweep the show podiums in a few years...

Matt

Isn't that where those "'Bow-tie' thingies" go? This piece will be flipped bottom for top, with several butterflies added.