A Tea Table Post

[4DThinker]

This is a sequence of images showing the steps from a cylinder of wood to a finished contoured post. 

Toolpaths were created in Aspire, but could have been done in VCarve Desktop or Pro. 

Wrapping toolpath to cut the initial square block into a cylinder.

A roughing toolpath to remove most of the waste for the moulding contour finish pass. 

A moulding toolpath finish pass to shape the bottom end for eventual dovetail slots. 

Finally a Moulding finish pass using a 1/8" ball end bit on the top contour shape. 

 

Leaving on the rotary axis until I decide the best approach to cutting the dovetail slots.  I may have to flip it end to end as I can't approach the bottom end where the chuck jaws are.

4D

 

[lew]

WOW! It's hard to imagine the difference between the forth and fifth picture!

[4DThinker]

In the forth photo the CNC was just finishing up with the contour toolpath.  The area from it to the end had already been done with another toolpath.  In  the final photo I've backed the CNC away from the post to take that photo. This photo would have been a better 4th photo with the contour toolpath roughly 3/4 done.  The 1/8" ball end bit took small steps over as it worked its way across the post.  There was roughly 45 minutes from when this photo was taken to when the 4th photo was taken.

 

4D  

[Grandpadave52]

That's impressive 4D. Count me in for this journey.

[4DThinker]

I will get the dovetail cuts done today.  Flipped the post over end to end so I can approach the bottom with the dovetail bit. Had to figure out what slope and diameter my old dovetail bit is.  Came from my old craftsman dovetail jig kit.  Must have bought that jig before the internet existed as there is very little if any data out there about the bits it included.  Think I've figured out it is 9/16 in diameter at the tip and has 8 degree sides.   Woke up this morning with visions of an internal rotating plate that would rotate 3 brass pins into the legs after they were inserted into the dovetail slots.   Not exactly sure why I need to though. Such is the challenge of vivid dreams. This idea might be perfect for some future project and not this little table. 

4D   

[4DThinker]

Dovetail cuts done.

Started with a pocket clearance cut to remove all but the undercut part that the dovetail bit would do.  Used a 1/4" end mill.

3/8" deep.  3 passes with the 1/4" bit. 

Clearance pockets cut.  Did one, rotated to 120 degrees.  Did the second one, the rotated to 240 degree for the third cut. 

Setup for the dovetail bit.

Slowed down the feed rate for the dovetail bit.  Ran the first one, rotated back to 0 degrees for the second one, then rotated to 120 degree for the last one.

Dovetails done.

Took the part off the rotary axis.  Removed the hex block from the bottom and threw it away. Have done some quick sanding on the broad sides to remove the subtle ripple surface left by the 1/8" ball nosed bit as it stepped across the surface. 

 

Now to find some material to make the legs/feet from. Been sketching leg variations hoping one sketch will stand out as worth using for this table.

4D

Edited May 12, 2023 by 4DThinker

[4DThinker]

Found some oak to use for the legs.  2 stretchers off a chair design I abandoned many year back. 3" wide, 1" thick, and 25ish inches long. Rounded over edges though.   Planed them down to 7/8" thick, then joined one edge to get rid of the previous rounded edge.  Could fit vectors for two legs on one piece and cut the 3rd from the other piece.   Need to cut the dovetails on the top ends which I'll likely tackle tomorrow,  Need to sleep on an idea for how to clamp them into my CNC's frame. 

4D

[4DThinker]

Just some contemplation here about what degree of effort might be appropriate to make a part.  I have 3 identical legs. Each one needs an identical dovetail cut on its top edge. I can clamp them one at at time vertically on my CNC, taking care to ensure the edge to be cut is perfectly horizontal relative to the plane of the CNC frame.  Once clamped in place I'll then need to touch the dovetail bit to a front edge, a side edge, and the top edge of the clamped in part so that the CNC will know where it needs to make the cut within  it's potential cutting area.   After the cut is made I'll have to repeat each of those previous steps 2 more times. 

 

Or I could make a fixture.  Time spent up front to design and make a shape that registers perfectly on my clamping jig, has a cutout where the leg parts can rest, has clearance for a single clamp to reach around to hold the leg in place while the CNC cuts the dovetail on it. Once the fixture is made the cutting of a dovetail on these legs is as simple as setting a leg in the fixture, tightening one clamp, hitting "RUN" on the CNC software.  A few hundred could be cut in an hour using this fixture.  I have 3 to cut.      Hmmmmm?

[4DThinker]

Did the dovetail cuts on the leg tops this morning.  Clamped the first on in place, than added bracing around it so I could just drop the second and third legs in for the same cut. 

 

Next was to zero out the dovetail bit for the cut.

 

First cut with the feed speed slowed down to 25% of default.  Looks good.

 

But did it fit?

Pretty good.  Now to repeat on two more legs.

 

Legs need a little refinement, such as chamfered edge, and maybe a shallow arc on the front face of the foot.  I'll wait until I have the top done and refined to see what the legs need.  So far legs are just slid in place.  The dovetail slot is tapered so they slid in easy but snugged up tight.

 

Top is next.  May take a few days of contemplation to decide what to do for a top. 

4D  

[John Morris]

Man that looks fun! 4D, how close is the surface to finish when working like this? I can't really see any lines or anything in the wood, do you still sand before applying finish?

[4DThinker]

Off the rotary axis the surface depends on how much stepover is used for the 1/8" ball nose bit that did the finish cut.  When I started sanding it I could feel and hear a slight ripple/buzz from that finish pass.  When the buzz stopped I knew I had knocked it down and could proceed with finer sandpaper then finish. 

When I taught furniture design the college had a big Multicam CNC and I oversaw 3 small Probotix CNCs.  Students who had the operator of the big machine cut their 3D surfaces they were usually left with obvious ripples that were a pain to sand smooth.  The Multicam CNC was so much in demand that shortcuts (and big stepovers with a big bit) were taken to speed through jobs.   When I did the 3D cuts for students I usually brought them home to do so using the CNC didn't distract me during class time.  I would set the parameters to end up with a similar smoothish surface as time wasn't really an issue and I could let a cut proceed all night if it needed to. 

 

10% of a .125 diameter bit is .0125".  80 grit sandpaper is also .0125 per grain, so the surface I get is equivalent to a sanded 80 grit surface.  I could use a 5% stepover for an even smoother 160 grit surface, but the cut would take twice as long.  Want to skip any needed sanding?  A 2.5% stepover would be equivalent to a 320 grit sanded surface. Plenty good for woodworking that doesn't need a mirror finish. You may burn up a router letting it run 4x longer though. 

4D

Edited May 13, 2023 by 4DThinker

[4DThinker]

Considering this design for the top of this 18" tall pedestal table.

Top View

 

Bottom view.

Menards has 16" wide oak panels all made up so I'll likely pick one up tomorrow to use for this top.   9 sided over the 3 legged base.  Something mathemagical afoot. 

4D 

[Grandpadave52]

I like it. 9 sided will give it a quite unique character. Glad I'm not doing the math though.

[4DThinker]

6 hours ago, Grandpadave52 said:

I like it. 9 sided will give it a quite unique character. Glad I'm not doing the math though.

No math was needed.  Aspire/VCarve have a drafting feature that will draw polygons with any number of sides you enter above 2.  In other words I cheated. 

4D

[Grandpadave52]

50 minutes ago, 4DThinker said:

In other words I cheated. 

Oh no, never say that. Just say I utilized a complex calculating method that incorporates multiple formulas which eventually yielded the desired result. In other words, if you can't baffle them with brilliance, buffalo them with B.S.

[4DThinker]

Almost.  I did use a complex CAD/CAM package that incorporated multiple algorithms which generated the desired result.  I could have drafted up and done a water colored rendering of the 9 sided shape but drafting paper and water colored renderings are challenging to post on the web. With  360/9 being 40 no challenging fractions are needed.  Seven sides would have been my other choice but 360/7 is a hard fraction to find with a protractor.  I suspect my CNC software also has a challenge with 7 sides given its precision being limited to 4 decimal places. 

4D

Edited May 14, 2023 by 4DThinker

[honesttjohn]

Super Cool!!!!  Way above my pay grade.

[4DThinker]

8 hours ago, honesttjohn said:

Super Cool!!!!  Way above my pay grade.

Thanks HJ. Best pay I get is the satisfaction of seeing parts come together.  Actual pay wasn't that great when I was working. 

4D

[4DThinker]

Picked up two 16" x 36" x 3/7" oak panels from Menards this morning.  Only needed 16" x 16" for the top, but figure if I like how this 18" tall pedestal table looks I may make a 24" version and can use the extra oak to make it.  Here is the bottom side being cut on my CNC.  This is the  wide chamfer almost finished being cut.  If goes shallow most of the way toward the edge, then finished with a steeper chamfer that echoes the chamfer on the top side. 

 

This this the CNC cutting the center hole that the post top will tenon into. 

 

I ran a perimeter pass but left about 1/8" in the center.  Took the board to my big compound miter saw to cut the top free from the larger panel.  Then to my bandsaw to cut the 9 sides free before moving to my benchtop router with flush trim bit to clean up the edge.  Then to pose for photos.

Bottom view of the top.  Does suggest that the legs need more detail.

 

Top view.  Feel like the top is sized right.  Open to any opinions good or bad.

 

Top and legs aren't glued together yet.  So far it's been a fun project to work on.  My tools were happy to pitch in as they've been a bit bored since I retired last June. 

I need to check the flatness of the bridges I clamp parts to on my CNC.  The oak panel should have been uniformly thick.  It did have a little bow out on one side but I was able clamp it flat to the bridges before cutting on it. Still the cuts were a little deeper on the right than on the left.  Nothing I couldn't correct on the finished top with just a little sanding, but something I didn't expect to see. 

4D

[honesttjohn]

Pretty darn cool Jointmeister.  All that time spent in school paid off.