OK, well I`ve set off on the next attempt at the cutter. I have decided a few things since my last attempt.
1. Use the correct material, a suitable carbon steel and ideally heat treat a piece to test it.
2. I need to be more accurate. I did some more calculations and the difference between module cutters is tiny, clearly I need more precision.
3. I need to really sharpen the cutter.
So with that in mind I decided to dig out my mitutoyo calipers and guage vernier that was given to me from a friend at work a few weeks ago. I haven`t used them yet and I think now is the time to learn. It puts me off because they are imperial but I`m getting much better now switching between metric and imperial over the last few months of reading both.
For the material I ordered some guage plate or ground flat stock as John Shadle suggests in his plans. Whats more, it acutally was advertised as “suitable for hardening for tooling”.
I next cut the out a rough disk with the hacksaw. Drilled a hole in the centre and mounted it on the actual arbour that it will be situated on when the cutter is finished. I then trued it up in the lathe and immediately hit problems. This stuff is pretty hard! I remembered a conversation we had on here a few days ago with John (Bogs) and remembered about honing in with a stone on the cutting tip. What a difference it made, the steel started curling and shaving off. I then continued cutting in from both sides, skimming slithers off until eventually I got to a width of .05″ for the tooth tip or what will become the gap between teeth. I then took this down to the correct depth for the dedendum of the teeth.
Next I needed to put on the radius 2.5mm. I really wanted to find a more accurate way of doing this but couldn`t think of anything better than John Shadle suggests in the plans. A well if it is good enough there it is good enough for me. I rounded an old 2.5mm drill bit to profile and mounted this in a little holder I made and held it with a grub screw:
I mounted this in the tool post and run the lathe on very slow with lots of oil. I thought I`d hit problems but to my astonishment, the steel started peeling off! I continued until I got to depth for the addendum and removed it all from the chuck:
If you look at the top of the picture below you can see the nice radius profile on the cutter. It looks much better than my previous attempts – much better
…. and then the battery went on the camera!
I`ve not done too much more other than remove it from the arbour and litterally cut the disk in half with a hack saw. I have then taken my time and really sharpened and honed in on the cutter edge. It is now really sharp and shiney. The great thing about this method is that you actually end up with two cutters (each half of the disk) and if an offset hole is drilled on both sides of the half disks, you end up with two cutting sides on both halfs of the cutter. John Shadle says this method takes an hour and I`ve probably put a good two hours already but I`m nearly there. I really hope this works otherwise I`m going to be pestering Stew to get this tool post grinder wheel cutting idea up and running :whip: lol.
I`ll take more pictures tomorrow, hopefully of a finished cutter.