I'm making a meat grinder plate for stuffing sausages. I am using a slice of 4140 because it is what I have and it was close to the needed end size. It is pretty tough machining for my little equipment but it can be done slowly and the finish turns out nice.
Normally the holes on such a plate are kidney shaped to allow maximum opening with little restriction. I however do not own a rotary table or the cutters to achieve such holes. So I figured I'd just put in as large of a hole and as many as I could. My original "plan" was 5x25mm holes. However just before drilling of the holes I decided to use 30mm holes as I had a backup cutter in that size if my first cutter failed (which I was expecting). I went to cut the second hole and realized that 30mm holes are not going to fit very well in my "plan". I went ahead and cut them all anyhow.
I had to use my drill press as I did not have a vice large enough to hold the piece properly on my milling machine, so rigidity was less than ideal. I used some horrible little carbide tooth hole saws I bought cheap of Aliexpress or Amazon. If you do not have any of these, keep it that way and buy something else if you can afford it. However if you are like me and figure you can't afford good annular cutters here are a couple of things to help make the cheesy ones work.
First replace the little 5mm set screw that holds in the drill bit with a decent screw. The originals do not hold the bit in tight and the head of them stripes out causing all sorts of frustration.
Second, do not try to cut more than about 3/16" thick mild steel as the saw does not evacuate the chips very well and you have to do constant plunging to clear chips. As well if you cut through much thicker stuff the donut hole that gets cut out is very difficult tk remove from the hole saw.
Third, the bits in these saws are also very poor. I predrilled a pilot hole in my piece and that helped.
Fourth, really try not to buy these if you can.
Having said all that....I was drilling through 3/8" 4140 and I did eventually get the job done.
Normally the holes on such a plate are kidney shaped to allow maximum opening with little restriction. I however do not own a rotary table or the cutters to achieve such holes. So I figured I'd just put in as large of a hole and as many as I could. My original "plan" was 5x25mm holes. However just before drilling of the holes I decided to use 30mm holes as I had a backup cutter in that size if my first cutter failed (which I was expecting). I went to cut the second hole and realized that 30mm holes are not going to fit very well in my "plan". I went ahead and cut them all anyhow.
I had to use my drill press as I did not have a vice large enough to hold the piece properly on my milling machine, so rigidity was less than ideal. I used some horrible little carbide tooth hole saws I bought cheap of Aliexpress or Amazon. If you do not have any of these, keep it that way and buy something else if you can afford it. However if you are like me and figure you can't afford good annular cutters here are a couple of things to help make the cheesy ones work.
First replace the little 5mm set screw that holds in the drill bit with a decent screw. The originals do not hold the bit in tight and the head of them stripes out causing all sorts of frustration.
Second, do not try to cut more than about 3/16" thick mild steel as the saw does not evacuate the chips very well and you have to do constant plunging to clear chips. As well if you cut through much thicker stuff the donut hole that gets cut out is very difficult tk remove from the hole saw.
Third, the bits in these saws are also very poor. I predrilled a pilot hole in my piece and that helped.
Fourth, really try not to buy these if you can.
Having said all that....I was drilling through 3/8" 4140 and I did eventually get the job done.
