I've had moderate success in making a sausage stuffer. I'm posting this information here simply to throw in some ideas for other beginners who might want to experiment.
Here is the stuffer showing the main frame, the lever, the syringe body and the plunger:
Here's a side view of the frame. In this picture the plunger has been pulled to bits to show how it is made (this isn't the only way to make it of course):
This is how it would be used. In practice, my left hand would be holding the casing on the nozzle and pushing down on the whole thing to anchor it:
I'm fortunate to have access to some fairly good metalworking gear.
The main syringe body is a six-inch length of 3 inch diameter stainless steel tube. The nozzle is stainless tube with a 5/8" outside diameter, which means the sausage mix gets forced through a hole little more than 1/2" in diameter. Both tubes are welded to a common bit of stainless steel flat plate.
The plunger end is made from some inch-thick plastic (nylon? polyethylene?) cutting board. The plunger shaft is just a 3/8" stainless bolt. The plastic plunger is tapped with a screw thread to take this bolt. The plunger assembly is reinforced with the stepped sleeve and bit of tube shown in the middle picture. I didn't have these two items for a start, but when I saw how much force was necessary to move the sausage through the small hole, I figured I needed them to stop the plastic thread getting stripped. Of course I could have used another idea to make a stronger shaft, but I had these two items on hand.
I had hoped that all I'd need would be the syringe body and plunger, but I was wrong. With my strength being distributed over the relatively large plunger diameter, I could barely get the meat moving.
By using a bigger diameter nozzle and a smaller diameter syringe tube, less force should be required to extrude the sausage mix....but less volume would have to be loaded for a tube of the same length. As it is, this system holds probably less than half a kilo of mix.
When I first made the plunger, I allowed only a few thousandths of an inch clearance between the plunger and the bore of the syringe tube. While this was good in theory, I found that the tube was slightly out of round and the plunger jammed. So I had to make the plunger substantially smaller. I thought that I might have to fit an o-ring to the cylindrical surface of the plunger to make it seal properly, but I found that the chunks in the mix made an effective seal...so the o-ring is not necessary. Perhaps if I had a very liquid mix, I would have to think about adding an o-ring.
Finding it virtually impossible to force mix through the nozzle with just the simple syringe arrangement, I had to make some sort of a 'machine' to help me. An elaborate stuffer might have a 'rack and pinion', or screw jack system, but I wanted to get going quickly with minimal expense and effort. I made up the frame pictured from aluminium channel section, a short bit of aluminium angle section, some bolts, and a couple of stainless pipe spacers.
At the rear of the assembly (the nozzle end is the front), I have four bolts spaced along to match the 'travel' of the plunger. I use a bit of stainless steel flat bar as a lever, using each bolt as a fulcrum point in turn.
This stuffer isn't simple to use, but it does the job for the quantities of sausages I will be making as I experiment. Today I made up a relatively coarse, dry Boerewors mix, and I found that I could extrude it through the machine....although it wasn't easy. Sometimes I would have to apply considerable pressure...then I'd get a great 'ejaculation' of sausage meat flying out.
Boerewors strikes me as being a relatively dry, stiff mix. With a fattier or wetter mix I imagine that the extrusion process would be easier.
Also, if I'd somehow fabricated a tapered nozzle I MAY have found that the machine took less force to operate. But a tapered nozzle isn't simple to make compared to a bit of tube, and more mix is left in a tapered or bigger nozzle once the plunger reaches the end of its travel.
My main current sausage-making goal is the production of Droewors. So I need something like this with a small nozzle.
Anyway...I just thought I'd share the results of my experiments. I'm considering the option of buying a nice commercial stuffer, but meanwhile this will keep me going.