MidnightStudio

This is a project that I finished up about a year ago and was the main motivation for purchasing my milling machine (yeah, didn’t take much, did it).  Finally, after 14 months of design, shopping for a mill, more design and fabrication, I completed my “ultimate” dish drying rack for the kitchen.  If you factor in the mill, it’s probably the world’s most expensive drying rack.

Exactly what is the Problem we’re trying to solve here?

I have a drying area behind my kitchen sink, which is the perfect location for a dish drying rack.  The space is 9.3” in depth and so requires a custom solution to full take advantage of it.

Years ago I build a wood rack for this area, and while it worked well at first and fit it perfectly in the area, over the years the constant wet environment had a damaging effect on the wood.  It would turn black with mold, the pegs eventually rotted and broke off, and the wood rack itself was just disintegrating.  A new rack was required.

My previous design worked well, and I was inclined to construct the replacement in a similar style.  Basically, a set of 0.25″ pegs spaced 1.25″ on a 9.3″ base, connected to six additional and identical bases.  The design was pretty straight forward.  How hard could this be, right?

My first thought was to build this rack from a moisture tolerant wood, such as Teak or Mahogany, but concluded that any wood would eventually have the same problem, and I wanted something more permanent and a bit more modern in appearance.

This required an either a plastic or metal base.  I ordered several samples of 0.75”x0.75” square rods of various materials for prototyping.

Material picked for the prototype included (from left to right), Aluminum, Stainless Steel, Brass, Acrylic and HDPE (High Density Polyethylene) (aka, cutting board plastic)

Stainless, while is looked great, would have made the rack heavy and was difficult to machine at the time.  Brass was expensive and I didn’t want the yellow coloration.  A prototype was made of aluminum, acrylic and HDPE.  Acrylic was ruled out for various reasons (some of which I overcame in the 14months of R&D).  Aluminum was a possibility, but the question of how do you secure the pegs in aluminum was an open question, as was discoloration from long term oxidation of the aluminum in a wet environments.  The HDPE prototype worked well and allowed for a design with a friction fit for the rods.

One additional issue with an all metal racks would have been the need for a softer material where a delicate knife edge and porcelain dish would rest.  I didn’t want to damage and dull my kitchen knifes by drying them while resting their delicate edges on a hard stainless or aluminum surface.  Some prototypes where created that would put a thin layer of rubber or plastic over the metal, but that proved complicated.  Note, since completing the rack a year ago, I have had positive experience with laser cutable rubbers, which would allows for easy fabrication of a soft surface (maybe in v2).  This still left the problem of securing the pegs into a metal base.  Investigation in welding and braising the rods to the metal bars didn’t yield good results (at least that I pull off).

In the end, HDPE was selected since it was easy to machine, lightweight would allow a secure friction fit of the rods to the material and was an acceptable surface for contact with delicate cooking tools (after all, you do cut on an a HDPE cutting board surface, so a knife should rest very well on it).

The next question was what material to use for the rods.  Since Stainless steel was an early favorite, that material was selected for the rods. A prototype HDPE with Stainless Rods was created and looked and functioned well.  I also prototyped with various rod thicknesses, but the one advantage that stainless gave is that I could use a thin diameter and have it still be ridged.  0.25” was selected.

It was around this time that I was looking for a used mill to add to the workshop, so the project was put on hold for a few months while a suitable milling machine from Craigslist could be located and purchased.  I eventually settled on a used RF45 Clone from Lathemaster (ZAY7045).  Add another few months to install a DRO with glass scales on all the axis.

Five 4’ rods of stainless were ordered as was a sheet of HDPE plastic.  Cutting the HDPE was straight forward on a compound miter saw, but the stainless was a bit complicated.  Using a parting tool on a metal lathe, I fabricated 68 4″ pegs.

One immediate problem with parting the rods on the lathe is that it left a very precise, if not razor sharp edge.  I was concerned that this would prevent the bars from seating properly into the holes and scratch any dishes.  Filing the edges did not sufficiently round the sharp edge.

The bars were reworked in the lathe to have a 45 degree relief on each edge.  A rather time consuming operation to do twice (once on each end) on 68 bars.

With the bars completed, it was time fabricate the horizontal HDPE bases.

Several prototype were made to determine how much smaller the hold had to be in order to correctly give a very tight fit to the 0.25” bar in HDPE plastic.  The rods were 0.250” and the correct hole diameter turned out to be 0.246”, or a D sized drill bit.  This allowed the bars to be easily tapped into the holes for a secure fit.

The device on the left is a fantastic piece of tooling, it’s a 5-axis Milling Stop, which allows you to set a workstop, so that I can slide bar after bar into the vise, slide it against the workstop and have it be in the same location every time.  I can’t recall where I purchased mine, but noticed that Enco now sells the same model.

After two hours, all six pieces were completed.  Two additional holes were needed on each part side to allow pegs to secure each base to one another.

Completing the rack was a simple matter of tapping in the pegs with a plastic  hammer.  Once seated, the pegs remain very firmly in place.

I wasn’t sure how well the kitchen ware would stand up to being inserted into stainless bars, so elected to add 0.25″ screw caps on the top of the pegs.  This provided a soft rubber surface for any delicate items that might come in contact with it.  I ordered several samples, and elected for black ones with a 0.5″ length.

A final detail, rubber feet.  I wanted the rack to be slightly higher than the surface to allow easy drying and evaporation of water trapped under the rack.  Plus the feet help secure the rack in place.

Three different samples were ordered.  Stainless screws were used in the correct size to secure the feet.  (Note, this turned out to be a big mistake, more below)

And finally, the completed rack.

The completed rack in place.

One year later

The rack works flawlessly, after a year, with almost no signs of wear.  Several of the rubber screw caps have become nicked from sharp knife edges.  They are not a big deal to replace as they are very inexpensive, but I need to factor in replacing about two caps per year.

Far worse was my decision in rubber feet.  While I did use a stainless screw to secure the feet to the base, the selected feet contained a zinc washer in their base.  After eight months, the washer started to corrode.  Unfortunately, white marble is very porous and soon I had rust stains deep within the marble top.  After trying various remedies to remove the rust, the one solution that worked fabulously was a mixture of 1 part Marble Poultice and 1 part Ironout (thank you internet searches).

I’ve been using the rack minus the rubber feet for the past few months while I search for an alternate.

Conclusion

This project started 14 months ago, and took a bit little longer than I expected.  Selecting, purchasing and repairing of the milling machine consumed a large portion of the time, as was the creation of many prototypes to select the final materials.  I’m currently planning for V2, which would be machined from stainless bases and include a 1/8″ thick rubber surface, laser cut to the shape of the bases, to protect knife edges, but that’s another project.

Breakdown

Build Time	~ 8 hours over eight days (minus various prototypes)
Total Time	14 months
Cost	~$30
Difficulty (1 to 10)	3 (basic design is pretty straight forward)