Sherline Flood Coolant System

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In Tabletop Machining, Joe Martin advises that a drop of oil now and then is enough lubricant for a Sherline mill. However, when running a CNC Sherline mill, that just isn't enough in my experience. The cutting is just too fast and produces too much swarf. The end mills get hot and the swarf gets ground back in between the end mill and the work surface making for a pretty poor finish in most cases. I built a vacuum system which was better because there was less damage to the work surface from the swarf. But things still got hot and in order to keep up the feed rate, I found that I needed to keep a couple bottles of coolant handy and keep things very wet. Then I found that the swarf became a problem again as it floated and swirled around the end mill chewing up my work once again. So, I decided to try a flood coolant system.

The reservoir

The coolant reservoir was a simple choice; a used kitty little container. You also find these outside your local deli.

I cut a 4" hole in the top with a razor knife.

Filter cartridge cap

The reservoir opening is filled with a 4" closet flange. You can buy one of these in your local hardware store, plumbing store, Home Depot, or... you get the idea. 

The truly frugal could probably skip this part but it is less than $10 and it does a nice job of keeping the "filter" in place.

The closet flange is then bolted in place.

The filter cartridge

A piece of 4" ABS pipe and an end cap will set you back another $10 or so. These are a snug fit so I did not glue them together. If they do get loose, I may run a screw or two through the side.

Next, drill a few 1" holes in the pipe. Bigger, smaller, more or less, to suit yourself.
This is roughly where the filter cartridge will sit.
The filter material is just nylon screen door mesh. I wrapped the pipe 3 times and then wrapped black electrical tape around the top and bottom and vertically up the end seem.

Place the completed filter cartridge into the reservoir roughly in the center. When you place the lid in place, it will center it. I did not glue the cap to the filter cartridge.

The way I think this should work is that the drain from the mill will flow first down inside this filter cartridge and the numerous holes in the pipe should flow plenty of coolant out. When swarf builds up enough, it's an easy job to pop the lid, lift out the filter, pull the cap off the bottom, and rinse it all out. So says my theory; we'll see.

Pump Hose Connections

Next came the home made bulkhead fitting. This was from the lamp section of the electrical department. It has an O.D. of 1/2". Buy two nuts and two washers, drill a hole in the lid, and screw it in place.

You could just drill a hole in the top and run the hose down to the pump. But, I wanted to be able to disconnect the hose from the pump reservoir in the middle. Take your pick.

Top and bottom look the same. Same nut, same washer.
The assembled lid. Bottom side up. That closet flange will slide neatly into the ABS pipe - filter cartridge.

The 1/2" tubing shown here was quickly replaced by some clear, reinforced material as this stuff came pre-kinked from the hardware store.

Coolant Pump

Here's my $60 pump before it goes down for the count into its new home. It's a submersible Pondmaster magnetic drive utility pump. I got this at a garden shop where they sell pond & patio supplies. 

According to the label it has : 

  • 140 GPH flow rate, 
  • Maximum 6 foot pump height
  • Adjustable flow
  • No maintenance
  • Washable foam pre-filter
  • Only one moving part.
  • 6 Ft. grounded power cord

Pump Placement

The coolant pump sitting on the bottom next to the filter cartridge.

Pump Switch

The pump is plugged into this switched outlet. I'm not sure that I like the pump cord coming out the front of the box and may change that later.

Finished Coolant Reservoir

The finished coolant reservoir. You can see the pump electrical cord exiting the front of the box. I just drilled a hole the same diameter as the electrical cord and then used some snips to cut a line about 1" up to the top of the reservoir in order to slide the cord down into the hole.

The coolant hose still requires hose clamps inside & out.

I got the drain hose from Home Depot. You can buy it by the foot but the hose guy suggested a pre-packaged length of about 20 or so for less money than the 5 feet I planned to purchase by the foot.

Coolant Feed

Coolant feed hose mounted in the mill box and on the mill arm.

The Loc-Line mount
The 1/4" Loc-Line aimed and ready.
A few things still need to be moved and tied off but I'm just about ready test the new coolant system and get back to work.
Top view of the drain
Bottom view of the drain
Everything worked pretty much as planned. The box contained the spray except towards the front, but that was expected until a suitable shield was put in place. I assumed at first that the front shield would cover the entire front area of the box but I knew it would be big and unwieldy. However, a shield closer to the spindle could be smaller.

I started by mounting a piece of .375" aluminum rod on either side of the mill plate. Each end was drilled and tapped for a#10-32 machine screw. A button head machine screw was screwed into one end.

The aluminum rod slides easily through the clamps and so the front shield can be moved closer to and further away from the spindle as needed.

As a way to protect the X axis motor and wiring, I mocked up a shield from  a bit of old peg board material; this will be replaced with Plexiglas. It's attached with the same plastic clamps and easily pivots up and down.

I will also mount one on the other end just to keep the spray to a minimum. They're so easy to make and so convenient to flip up and down. Very effective too.

Next, I needed a guard for the front. You can see that with the two button head machine screws protruding just a bit, all that is needed is a simple flat shield with two notches to slide over the ends of the screws. A hinged mechanism could also be used but this was very simple, light, and easily moved out of the way.


I first used a thin piece of aluminum to make the front shield but changed my mind and quickly made one from plastic. This way, I can see a bit of what's going on as the mill is working; well, sort of.

You can see that I also milled a trough around the plate. It doesn't catch & drain all of the coolant flowing off the plate but it does direct the vast majority of it off to the sides, onto the sloping bottom of the box, and down to the drain.

Updated: August 04, 2014