Oil filter crusher

My friend has an oil burner installation business and brought up a problem he has. The burners have an oil filter that has to be changed regularly and these used filters are considered hazardous waste as such, so getting them processed correctly costs very much. But if the oil filter is crushed so that the remaining oil inside the filter gets out, this crushed filter can then be thrown in to a metal recycling bin. The oil from the filters is collected and either used in a waste oil burner or given to a hazardous waste plant as fuel for their burning processes.

At first I of course used Google to search for existing solutions to see how the crushing is done commercially. The search results indicated that most of the commercial crushers are using pressurised air and some work with hydraulic/electric power. The usual tonnage I saw was between 3 to 10 tons, most of the crushers being in the 6 to 10 tons category.

I first thought of using pressurised air as that is easily available at 10 bar pressure, but to get 10 tons of pressure needs a piston that is about 350 mm in diameter. The idea of turning the piston and cylinder myself in a lathe felt like a bad idea and I didn't even want to know how much a commercially made cylinder would have cost, so something else had to be considered.

I had thought of using hydraulics and investigated on the price to build a hydraulic pump unit and a some sort of press frame from steel, but the price would have been in the 500 EUR and up category just for the hydraulic parts. I talked about this idea at work and one guy suggested using a hydraulic log splitter.

Hydraulic log splitter. That idea had potential, as I knew those would cost very little and so I did a quick search. A local business called Motonet had on their website four different models, three ranging from 199 to 299 EUR for horizontal models and one vertical model for 399 EUR. Each had a 6 ton rated capacity, so they all had enough force. And for this price it would have been impossible to get this crusher parts let alone all the work neeeded. My friend wanted the vertical model as it had small foot print and seemed very sturdy.

The log splitter originally has a table that is stationary and the splitting wedge moves up and down by hydraulics. It has a 3 kW electric motor so it needs a 16 A wall outlet to run. In operation the motor runs constantly and circulates the hydraulic oil through the operating valve back to the tank. When you push down both hand levers the valve opens and the piston pulls the wedge down. When either the travel ends or the pressure is at its maximum, an overpressure relief valve opens and lets the oil flow past the cylinder. When the levers are let go, the valve moves to the other end by a spring load and the piston moves up until a small limit rod pulls the valve to its center position and the movement stops.

I measured that when the wedge is at its lowest position, there is a gap of 135 mm from the wedge to the table top. I also measured that the wedge is not parallel to the table but inclined about 5 mm from end to end. This meant that I had to use an angle grinder to get that inclination away and to make such an attachment that it has at least 135 mm height. The inclination was easy to get rid off, I just put a straight edge against the square tube and drew a line on the side of the wedge.

As the oil filters are about 75 mm in diameter I had to have at least about 100 mm square plates for crushing the filters. I found about 140 mm square plates from the scrap bin that were both about 25 - 30 mm thick, so I sawed off a section of U-beam to lift up the other plate enough from the table. I squared everything in a CNC mill and used it to make a 120 mm in diameter and 3 mm deep pocket on the lower plate. I also made the pocket to be a little bit concave on the bottom, so the center is at 6 mm deep to get the oil to flow to the center. In the center I drilled an almost through hole and from the side of the plate I drilled an 11.7 mm hole to the center and tapped this with G 1/4" pipe thread.

After removing paint from the parts, I used a MIG welder to put everything together. The welds were a not so good in some places as the welders copper tip was worn out, no new one was around and thus it gave me problems every 10 seconds or so.

Finally after cooling the parts I was able to assemble the not-so-log-splitter-anymore and to test it out. I screwed in a hose fitting on the side of the lower plate and ran a short length of hose to a collection bucket for the oil. The first test was to run down the piston to its lowest position to see how smmall gap there is between the crushing plates and this showed to be about 10-15 mm, so it might hurt your fingers a little if left between.

The second test was of course to put a used oil filter on the bottom plate and see if the machine has enough power to crush it. With safety glasses on I pulled the levers down and watched as the filter nicely folded down in to a pancake. In the almost end of the stroke I saw an ooze of oil squirt down the hose in to the bucket, so it worked just like it should. The end result was a very flat oil filter, about 25 % of its original size and about a 100 ml of oil. The total time to crush a filter was about 10 seconds.

Of course I called my friend to let him know that the machine was ready and that he would bring a box of used filters with him to test the machine. He showed up with about 50 oil filters in three carton boxes and together we crushed them in no time. End result was only a small bucket full of crushed filters and 5 litres of oil. No wonder they charge so much to dispose off as hazardous waste. Now he saves lots of money by recycling the empty oil filters as metal and by giving away the used oil as a fuel. And even if the regulations would say that the crushed oil filters are still hazardous waste, it would cost less to dispose off as they weigh a lot less and take up smaller space.

Now the only thing to do is an oil change to the crusher and adding an oil filter to the pipe that runs from the tank to the pump to keep the machine in operation for a lot longer than the original.

And as hydraulic log splitters can be had with a 1000 mm stroke and 6 tons of force and they contain everything needed between an electrical wall outlet and the hydraulic piston and the fact that they cost only 200-400 EUR, this will be my source for hydraulic power unit for a small hydraulic press. Nice to have electric motor running and just pressing a button to get all the movement without tedious hand cranking.

Changing mains plug

The SIEG C4 lathe that I bought from Axminster Tool Centre works on 230 VAC 50 Hz mains voltage, the same we have here in Finland. The only problem was that the power plug in the end of the cord was some British type and not the kind of we use. So I went to the local hardware store and bought a plug that is made of rubber, rated for 16A and has an insulation class IP44. The cost of the plug was 1.79 EUR, so it is cheap.

I don't know of other countries laws on electrical work, but here everybody has the right to change a power cord to a device. Technically I'm not changing the cord but in reality I'm doing the very same end result with the same connections so it doesn't count.

First thing to do was to cut the original British plug and toss it. At the same time I stripped the insulation down about 40 mm and clipped the neutral and live wire about 5-10 mm shorter than the grounding wire. This is made so that if you yank the cord and the wires get ripped off, the ground connection is the last one to rip off and in some cases it can save your life. In this plug it doesn't matter that much, but I have a habit of doing this always so I don't forget it.

I stripped the insulation off of the ends of the leads for about 5 mm and twisted the stranded wire together. Using a screwdriver I opened the new plug and screwed off the strain relief.



First I opened the screw for the grounding wire (green-yellow) and put it under the screw and tightened. After that I bent the live (brown) and neutral (blue) to their attachment points and screwed them tightly. This plug type is non-polarised, so it doesn't matter which way you attach the live and neutral. Last I screwed the strain relief tightly so it clamps on the black insulation of the cord.

Pulled the cover on and screwed it snug and this modification is done.

Blasting cabinet mods

Here is my blasting cabinet in operational condition albeit still on the floor in this picture. The small rectangular box contains about a litre of pantyhose filtered glass beads ready for use in the small blasting pen. The blasting pen is the one with the long and colorful hose in the middle and it has a small cup that holds the blasting media.

The original blasting gun was supposed to be installed with a small female connector in the right hand side panel so that there would be a G 1/4" female thread for a pipe connector. But as I'm not going to use the original gun but the blasting pen and I want a small air gun in there also for cleaning, I made a small splitter block from aluminum. The splitter block has two female quick connectors to attach the pen and the gun. The splitter has G 1/4" threads for the quick connectors and one cross drilling that I plugged from the end with an R 1/4" plug and pipe connection glue.

The air gun is from Biltema and provides very good adjustability as the trigger lever is long. It also happened to have the dangling hook in an otimal place just by coincidence, as I found out that it fits perfectly loose to the M4 screw that holds the air filter in the cabinet and is in reach of my hand while working. The hose for this air gun I liberated from the original blasting gun as it is quite thin walled and very flexible, so it is easy to maneuver inside the cabinet.

The inlet to the splitter block comes from the compressor with a hose that has a female quick connector in the end that fits a male quick connector. This is attached to an elbow joint that is going through the cabinet wall to the splitter block and keeping it also in place. The elbow connection saves me some lateral room as it comes out only about 30 mm from the side of the cabinet versus about 100 mm that it would take with the quick connector & hose coming in horizontally.

Blasting cabinet

I bought a blasting cabinet from Biltema (article #15-377) for 159 EUR. The cabinet is quite small so it fits my workshop well, as it is more than enough in size for my parts. My intention is to use this with the silent air compressor I built earlier, but I'm going to use a small blasting pen with this cabinet to keep the air consumption low. My blasting media will be fine glass beads as I want to have a nice finished surface on my parts and one lock related project needs this also.

And as with all things that I carry home, it happened once again. I get the box inside, close the door and turn around and the Quality Inspection Team is all over the place. Yup, that's my other cat, enjoying a new toy. Well, at least they get the box afterwards as they love to play and sleep in them :)

The box contained all the parts neatly packed and properly shielded with lots of bubble wrap. I pulled all the essential small parts out front to take this picture. In here you'll see the V-bottom of the cabinet, the gloves, the supplied blasting gun and four nozzles, the lamp and a power source for it, instructions manual and a bag full of nuts & bolts. Notice the grey foam around the V-bottom, this was preinstalled but I was not thrilled of it and the next pictures shows why.

Here I'm applying very liberal amounts of butyl sealant with a caulking gun. The sealant was a 300 ml tube from Biltema for 3.99 EUR and the gun also from Biltema for 2.99 EUR. The butyl sealant is good as it remains elastic and kind of rubbery when it hardens fully (around 1-3 weeks). Downside is the enourmous force needed to squeeze it out of the tube, as it is very thick.

The sealent begans to surfaceharden after about 20 minutes so there is plenty of time to install the parts and screw everything down. In the picture I'm just installing one of the sides to the V-bottom after applying the sealant. You can notice that I removed the original foam seal from the V-bottom. The reason is that I didn't like it and I had a tube full of this butyl sealant that I could install instead. I wanted a blasting cabinet that would not blow the blasting media all over my room from the small holes that would have been left in the corners and joints where the bolts are. Applying this sealant to all mating surfaces provides me an "airtight" blasting cabinet and helps to keep noise level and cleaning down.

The only difficulty I found installing all the parts was with the gloves. I couldn't keep them in place with only one hand while trying to fit the compression ring around them with the other. Finally I figured out that I could put the ring ready on the glove, fold the gloves edge around the ring and then install it in the cabinet. Worked well and got everything assembled. In the picture you see the original gun and its nozzles and the small 12 V transformer for the interior light. This is a nice safety feature as there isn't 230 VAC inside the cabinet. On the right hand side in the upper back corner there is a small yellow air filter that lets out the air but keeps the blasting media inside and also drops down the noise somewhat.

Although the cabinet has its own feet, I'm not putting it on a table but will make feet for it instead and write about them and one other mod I have in my mind.

Bigger tools to the C4 lathe tool post

The original tool post that comes with the SIEG C4 lathe accepts up to 13.8 mm thick tool shanks, but the maximum tool height to axis of rotation is only 10 mm. I think this a place where SIEG should make a change to their lathe as the lathe has enough power to use bigger tools. Only needed operation would be to make the tool post 2 mm lower.

My own way of modifying the tool post was to use a surface grinder to take off 2,00 mm from the bottom of the tool post. Because the tool post goes over a small shouldered bolt in the compound rest, the bolts shoulder had to be turned shorter. I took about 1.6 mm off of the length of the shoulder in a lathe and chamfered the edge.

I bought a DNMG insert holder from eBay that had a 20 x 20 mm shank and wanted to use it in my lathe, so again had to modify it to fit my tool post. I tried my best to search for 12 x 12 mm shank DNMG insert holders, but could not find any, so the 20 x 20 mm shank had to be bought. At the same time I also bought a 10 piece package of DNMG 110404 NF inserts. The nice thing with these inserts is that they are negative inserts, meaning the insert can be used four times and for me this means 1 EUR per insert edge, so very cheap.

To minimize measuring and setups I used a surface grinder to knock off all the material needed from the insert holder. First I measured that I could take about 5 mm from the bottom safely without messing with the insert retaining screw. Then the remaining 3 mm from the bottom I took so that I created an edge to the holders bottom as can be seen from the photos.

Last operation was to take 8 mm from the backside of the holder so it wouldn't hang so much out from the tool post. This was easy and fast and the last operation I did was to chamfer all the sharp edges with a file. The shank material was hardened, but filed quite okay.

Last thing to do was of course test this new tool with the new tool post mod. The tool sat very well, about 0.1-0.2 mm under the center of rotation as I checked it with a dead center mounted in the tailstock. By the way, it is a good practice to keep something in the tailstock taper as it prevents chips from entering it.

For the test I used RPM of 600 for a 60 mm diameter scrap piece. This gave me a surface speed of 113 m/min now that I calculated it. I usually aim for about 120 m/min minimum if the steel is nothing special. The feed was 0.15 mm per revolution. Depth of cut was 1 mm and the lathe happily purred away throwing short painfully hot deep blue chips. The finish was very good, considering a feed 0.15 and an insert radius of 0.4 mm.

I'm very happy of this tool post modification as it means that I can finally use the lathe :) I'm still going to buy a quick change tool post, but this will do until then.

Silent air compressor

For a long time I have wanted to have pressurised air available, especially for glass bead blasting of machined parts. The main reason I haven't just bought an air compressor is that they are loud as a jet engine, usually in the order of 85-95 dB and that just doesn't cut it in an apartment complex.

About a year ago I stumbled upon articles in the internet of how to use a freezer or fridge compressor to produce compressed air silently. The only drawback is low air output volume, but my need is occasional and very little, so this fits for me.

A week ago I was able to obtain a working compressor out of an old freezer. This was an old ZEM compressor with 110 W of power and it runs from 230 VAC 50 Hz supply. The best thing is that it was from a freezer, as these are usually more powerful than compressors from fridges. The compressor had its original oil still in it, so I poured it in to a junk oil container and replaced it with a regular oil meant for automatic transmissions. The only requirements are low viscosity and that the oil is of mineral variety.

These freezer compressors are able to produce enormous pressures and also vacuums, so care must be taken that the system is able to withstand the pressure. This usually means a pressure switch that cuts of the compressor when the pressure reaches a set upper limit and starts the compressor when the pressure drops below a set lower limit. Also an overpressure valve is needed, as it vents if the pressure switch doesn't switch off the compressor.

To have a big supply of air for some time the compressor needs a pressure tank after it. This can be an old carbon dioxide extinguisher bottle or gas bottle that is rated for the intended pressure. There is also a need for the pressure switch, pressure regulator, connectors, piping, oil/water catcher and air drier. If you have to buy everything as new, the total will cost probably around 100-200 EUR plus all the work needed to assemble everything.

This is the reason I thought of buying a brand new compressor unit and just replacing the compressor unit with the freezer compressor. So I spent 89 EUR to buy a Herkules brand compressor from Bauhaus, as it was the cheapest I found that had a 24 liter pressure tank. The original compressor unit fills the tank in about 2 minutes from 0 to 10 bar, but produces an ear breaking noise of 97 dB at the same time. Not good.

So I started disassembling the unit to get the original compressor out and to take measurements of the pipe size used so I can make or buy a proper sized fitting between the pressure container and my freezer compressor. It was quite easy to just unscrew the plastic cover to reveal the compressor unit, but the Abiko connectors to the power switch didn't want to come off so they got a quick treatment from pliers.

After removing everything not needed, I was left with a tank, a one way valve, a pressure switch, overpressure vent and pressure gauge with an adjustment valve. The output is a 1/4" female quick connector and the input to the tank is from the end of the one way valve that has G 3/8" male thread.


The freezer compressor had a 1/4" OD copper tube as its output, so I bought a hose connector that had a 1/4" hole through it. From this I hacksawed the hose connection part off and after cleaning everything, I soldered this to the compressor output tube. To the one way valve I rolled few turns of PTFE tape and screwed on a G 3/8" -> 10 mm hose connector. This way I can attach the compressor to the tank with a small length of hose and avoid induced vibrations to the tank and also avoid messing with rigid tubing and bending.

The pressure switch was factory set to have 10 bar upper limit and 8 bar lower limit. I plugged the modded compressor to the wall for a quick test and started a timer to see how long it takes to fill the 24 liter tank from 0 to 10 bar. The pressure rise was slow but steady and finally after 24 minutes the pressure switch turned the compressor off. This means that the compressor can provide about 10 litres per minute. The 0-5 bar rise time was exactly 10 minutes.

I was a little bit doubtful if the freezer compressor could start against pressure, so I blead the tank slowly until I heard the pressure switch click on at the 8 bar marker. The compressor immediately started to purr and building more pressure to the tank. I timed how long it took to see how much the air output volume would change from the first run as this was against pressure. It took 4 minutes 50 seconds until the compressor shut off, so against pressure the compressor can provide about 9.93 litres per minute, which doesn't differ from the 0-10 bar rise time.

The compressor temperature climbed to quite warm during the half hour test, meaning I could not keep my hand on it for long. I'm quite sure my air need is so small that this will not be a problem as I can switch the compressor off when I have pressure in the tank, but I could add a small 230 VAC fan to blow cooling air over it.

Of course mounting the freezer compressor meant that I had to fabricate some sort of plate that attaches to the tank mounting holes and that has mounting holes for the freezer compressor. I used a proper sized piece of aluminum plate that I countoured with a CNC mill and drilled and threaded for M6 screws. I used the freezer compressors own rubber feets to isolate vibrations from the unit to the rest of the system. In the rear end I also installed a small water separator unit that is screwed to the plate and inside the plate is an 8 mm passage for the air. On the back side there is one electrical connection to the pressure switch, which is wired in series with the fridge compressor and shuts it off when there is 10 bar in the tank.

So how silent is my silent compressor? Well, I can just hear it running, sounds like a fridge humming its things. Yep, beats the so called "silent" compressors they advertise in hardware stores with about 68-70 dB sound output.

Added 06.01.2011: I bought a small Simota brand air filter that had a connection for a 9 mm diameter tube. This was probably meant for some RC car or something, but works wonders in this application and totally eliminates the small intake sound of the compressor.

I also had an idea for a decal to replace the original "Herkules" tape and so I used 5 minutes with KolourPaint and printed off a nice new decal and attached it (poorly) with a piece of tape meant for covering books. The word "Perkules" is a kind of twist from a Finnish curse word "perkele" and the original brand "Herkules". The word below it is my own drunk misspelling of the word "kompressori", which is Finnish for a compressor.

Mod: Reversible spindle for X2 mini mill

Almost from the day I got my X2 mini mill I have been thinking of adding a reverse switch to it. Countless times I have tapped with power but have had to wind the tap out by hand as the spindle has no reverse.

All I know of the mills power and voltage demand for the motor that it is about 300 W, so about 1-1.5 A of current from mains at most. The voltage is probably just full bridge rectified mains voltage, so about 325 V at maximum. I'm thinking of a 250 VAC and at least 2 A rated DPDT (double pole double throw) ON-ON switch for this application. Now you may think that the switch can't handle the requirements and it is true. But it is true only if used to switch under a load. The closed switch easily handles the voltage and the current and there is no problems.

Well, finally I decided that enough is enough, as I had to tap over 50 M4 holes and my hand said no go. I went to the electronics store, bought a DPDT ON-ON type switch, rated for 250 VAC / 3 A. Price was 1.85 EUR, so nickels to save my hand.

Quickly drilled a small hole to the controller box and installed the switch. Then I clipped off the quick connector clips from the motors leads and soldered the leads from the controller to the switch's centre poles and the leads to the motor to the other end of the switch. After that I soldered jumper connections from the other side of the switch connections to the motor cables but crossed them. This way the switch flips the polarity going to the motor and thus the motor runs in reverse.

Tested after assembling the controllor box and it worked! I also got the switch mounted so that regular clockwise rotation is achieved when the switch is down and counter clockwise when it is up. Easy to remember from tapping: Down goes down and up comes up :)