John, really appreciate the reply. I didn`t realise that it should be that sharp, I thought sharp was just a clean front edge! How would I achieve such a sharp edge .... people talk about having sharp HSS lathe tools and it is the same there, I thought it just means a good clean cutting edge.
Regarding the process of taking the cut, I`ve spoken to a few people tonight and believe the best way to do this is to feed along the X-axis and take the entire cut very slowly but in one pass. This is the information I was given and I hope that Jim doesn`t mind me passing this information on:
Reading the information I have been given on here and in the message below, I think I have fallen on a few accounts...
Chris,
Really nice job of documentation on your blog. And congratulations on your first wheel, be it a bit less than perfect. I don’t think my first one was perfect either.
To your questions, I have cut many hundreds of wheels and pinions, so I will comment on what works for me and my thoughts as to where you may have gone a bit wrong.
1. It looks to me as if you cutter is not really “sharp” as in really sharp - as john mentioned above
a. Is it very hard? If not, it will be difficult to sharpen and will give you ragged teeth like you are getting
2. I feed from the X axis into the cutter rotating into the gear blank
a. I cut full depth in a single pass (if and when I measured it well and set it up properly)
3. I use coolant/lubrication . I realize there are many books that say it is not necessary, I think a lot of writers have not cut very many gears. Yes it is messy.
4. I suspect you may not have a “free machining” brass. Some brass formulations cut far better than others. I use ½ hard engraving brass for all my work and have for a very long time. I have tried some surplus brass that originated in China that was nearly impossible to machine, just FYI, even with coolant /lube and sharp cutters
5. Both wheel and pinion cutting likes a very rigid mount for both the blank and the cutter
6. I back up my blanks with either scrap aluminum or brass
7. I use fly cutters only as a last resort, but they work fine when the other 6 points above are in order
8. Cutter speed for fly cutting should be fast….. it is hard to rotate the cutter too fast on most mills…..I would push for at least 1500 rpm minimally
9. Feed rate should be slow into the cutter
Quite scary actually - reading all the above I think I have issues or done things incorrectly in nearly all aspects.
Time to try again....
Chris