Small Steps and Early Beginnings - Flycutting

I am now beginning to be actually using (and slowly learning a little bit by bit) my lathe and mills in my nice new workshop and am having fun as well as frustration and I am thoroughly enjoying it.

I had not tried any fly cutting (not done a lot of any cutting really) over my past 6 months of beginners practice, but as it looked a useful technique I got myself a low cost R8 fly-cutting tool holdr and some 5/16 HSS from those awfully nice people at Arc Euro, and armed with a printout of the guide to grinding a suitable tool by Bogstandard I managed to produce a cutter and had a test run on a bit of scrap on the manual Super X3 mill taking very light cuts. I was delighted with the results. I then tried on the KX3 – big advantage being I can set it up to make multiple passes to get down to the required total depth, set it off to compete the task and no laborious handle turning and counting. I can then get on with something else manually whilst it runs. Yes I can do this with conventional milling cutters too, and have been practicing this up till now, but the number of passes of a much smaller size cutter, even with a deeper cut per pass, have resulted in runs to surface a block taking well over an hour or even two. The bigger sweep of a flycutter seems to make for speedier material removal, even with lighter cut per pass, and the finish is really good.

I am so delighted with these results that this weekend I start on my first ‘real’ project – the Firefly 46 glow motor. Or rather two as I plan to make a pair. I just hope this is not too ambitious for a first project! First task will be to fly-cut the crankcases to size +.5mm ready for the drilling/boring. Jason's build blog will be my bible (stand by for dumb 'how do I' questions...)

What should be the average and max depth of cut I should work with for a fly-cutter?

I am running at 600 - 650 RPM and there is a very gentle vibration due to the imbalance - is it worth buying a more expensive flycutter tool holder that is better ballanced, and if so what can you experienced chaps recommend?

Speed will really be determined by the actual diameter that the tip of the tool describes, I would imagine your R8 tool swings 3-4" so that speed or a little less will be OK. I mostly tend to use smaller flucutters with a 1/2" shank but either should be fine.

J

Would be nice if you start another thread on your build.

There are lots of online calculators for feedrate and cut depths, but most of them apply to heavy industrial machines. The KX3 and the Super X3 are, like most hobby level machines very light weight compared to industrial machines.

I use a calculator called GWizard **LINK** with my CNC converted X3, unfortunately it isn't free, but does come with a 30 day free trial period. The best thing about it is that the associated website and blog contains a huge amount of information about machining and engineering in general (all free). Even if you are not interested inthe calculator the website is well worth a browse.

The advantage of GWizard is that it can be set up for hobby type machines (ie low power low rigidity) and seems to give sensible results. Whilst you can use trial and error for manual milling, because you get a lot of feedback about the cutting conditions via the handwheels, it is not so easy with a CNC mill.

One approach is to use GWizard for a trial period and estabish some good cutting conditions for your machine with a range of cutters, then simply make a note of the cutting conditions, which you can then use when the trial period expires.

Chris

Jason - the swing is 80mm ( about 3.1" ).  Yes I could start a separate build blog... but it will take a long time to complete.....

Chris - I will check out GWizzard but feel it may require more background knowledge than I actually have... At present I use the feed and speed calculator available within the Newfangled Wizzards in Mach3 and then start at 50% of those figures and work up to 90% - 100% if all is good with my test pieces. So far they seem OK.

Edited By EtheAv8r on 02/08/2012 23:00:18