Fly Cutting

[Steve WithnellParticipant @stevewithnell34426]

I’ve never done any flycutting and my current project calls for two surfaces to be skimmed with a fly cutter.

 

So I got one of these indian ones on a MT3 taper and had a practice run:

 

With this result

 

So I thought what I really need is an M&S flycutter, but turns they don’t sell flycutters so I made my own:

 

Lots of rigidity, lots of mass in inch square bar and momentum too at high rpm. Result:

(The nasty bits at the bottom are previous drilled holes in the scrap)

Result:

 

I’ve taken cuts upto 1.5mm and the finish is less good, though still good.

 

Steve

[Steve WithnellParticipant @stevewithnell34426]

[_Paul_Participant @_paul_]

Hi Steve,

 

If you ran the bought flycutter with the tool steel hanging as far out as the pic shows the finish you got isn’t surprising

 

Also Looking at the tool steel in your bought cutter is it the right size looks a bit thin in the pic? if it is that wont help either.

 

In my experience if the tool edge is out beyond around 1/2 the width of the cutter body using 1/4″ tool steel (or carbide tipped) the finish starts to suffer depending of course on speed, material, lubricant & depth of cut.

 

Your home made cutter is impressive, a 1.5mm cut with a flycutter is quite heavy.

 

Regards

 

Paul

 

 

[wheeltapperParticipant @wheeltapper]

Hi Steve

did you use the cutter with the pointy end that they come with?

I’ve got the same sort and I got a much better finish by rounding the end off a bit.

 

Bogstandard has a thread about it somewhere but I cant find it at the moment but I followed his idea, the finish on my engine crankcase is straight from the flycutter.

 

BTW if you flycut ali, use wd40 to lubricate, comes up lovely.

 

Roy

[Steve WithnellParticipant @stevewithnell34426]

I cut the piece dry, so I’ll break out the WD40 and see how that works out.

 

The Indian flycutter slot would take a bigger piece of tool steel than 1/4 inch, but not much.

 

 

I had thought taking light cuts I’d get away with it. Clearly not. I was going to set it up in the mill and run a 10mm slot drill through, as I needed much more than 1/2 inch overhang. At that point I thought I might as well make something more solid.With my M&S version I’m going to creep up the depth of cut and see what happens, 1.5mm wasn’t bad at all.

 

Roy – did you spot what my piece of scrap was?

 

 

 

 

[colin hawesParticipant @colinhawes85982]

Hi Steve, I agree with the previous comments and would like to add that the workpiece needs to be well suported underneath by packing if it is not flat. Vibration is the problem.

Colin

[Gordon WParticipant @gordonw]

I like the homemade fly-cutter, I made something almost identical to use as a trepanning tool with the steel plate to be cut mounted on an angle plate screwed to the cross slide, worked well. I think the extra flywheel effect helps on small lathes. As mentioned Bogstandard has some very good stuff on fly-cutting.

[wheeltapperParticipant @wheeltapper]

Posted by Steve Withnell on 22/10/2011 17:25:39:

I cut the piece dry, so I’ll break out the WD40 and see how that works out.

 

The Indian flycutter slot would take a bigger piece of tool steel than 1/4 inch, but not much.

 

 

I had thought taking light cuts I’d get away with it. Clearly not. I was going to set it up in the mill and run a 10mm slot drill through, as I needed much more than 1/2 inch overhang. At that point I thought I might as well make something more solid.With my M&S version I’m going to creep up the depth of cut and see what happens, 1.5mm wasn’t bad at all.

 

Roy – did you spot what my piece of scrap was?

 

 

 

 

Hiya Steve.

just remembered this, no I don’t , sorry.

blame it on old age.

 

Roy.

[Clive HartlandParticipant @clivehartland94829]

Steve, Looks like a scrap crankcase off a Nemett?

 

Clive

[Steve WithnellParticipant @stevewithnell34426]

That’s it! I think I made two of most things!

 

 

I didn’t flycut the crankcase, but used an endmill in 3mm wide cuts, so it has a distinctive machining pattern all over.

 

 

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