Fly Cutting

I need to create a flat surface using my Super 7 ( approx. 4in x 3in). I can either fly cut or end mill in stages using a vertical slide.

My question is :- has anyone out there used say a 1in dia end mill mounted eccentrically in the 4 jaw chuck as an fly cutter with the job mounted on the cross slide?

You would do better making a simple bit holder to mount on the faceplate. Say a length of 1" dia steel drilled and tapped one end for a bolt to go through the faceplate. The other end drilled say 1/4" for a round HSS tool (old centre drill or milling cutter) that can be ground to suit and a tappe dcross hole for a grub screw to retain the bit.

You could mount a bit of square or round HSS in the four jaw chuck, or as Jason suggests, you can fit a bit of square in a round hole, and secure it with a screw.

Ian S C

Its going to need to be a big bit of HSS is you are going to be able to hold it in a 4 jaw and offset by 1.5" to get the 3" swing required.

Use a lathe bit in the chuck. I use a 6mm button tool in a flycutter for some work and the basic flycutter bit is ground like a lathe tool. There may be a need for some paper or card to be fitted between the chuck and the tool to increase friction.

Martin

If possible mount the work in chuck or faceplate, much easier.

As Gordon suggests, if the shape permits the work to be held in the 4J, or on faceplate, on a Super 7 it would be much easier to face the surface flat.

Using an eccentrically mounted end mill as a fly cutter sounds a bit dodgy to me, unless you grind off all but one of the teeth, which is a waste of a good end mill (unless it's EOL anyway).

Or you could make a fly cutter yourself. This would be a most useful accessory, well worth the time involved in making it. There are numerous designs available on the internet that are simple turning and drilling jobs.

One of the simplest types can be seen here: http://www.cnccookbook.com/CCFlyCutter.html
Scroll down and you will see 2 different sizes in the guy's hand.

Dave
The Emerald Isle

Mounting the work on a faceplate/4Jaw/whatever and using a tool in the toolpost won't generate a flat surface (or shouldn't, anyway) because of the non-90deg angle of the cross slide (i.e. you're just doing a normal facing procedure). Doing it the other way 'round will generate a flat surface, but then you need to take the cross slide angle into account if it's a critical job. Of course, these effects become less apparent as the workpiece becomes smaller. It just depends on really how flat is flat enough.

Roger

Second photo down shows what I had in mind, it will do the whole face in one pass.

As Jason said, that's the most straightforward way of getting a flat face.

Further to my previous post, if the workpiece is small, and your compound has sufficient travel, then you could face a true flat using the compound only, but you would have to set it up very carefully.

Roger

Chances of setting the compound dead square is remote but possible, lots of trial and error?

Facing a 4" x 3" in the chuck - how far out from a flat surface will this be ?

.

... Length of the proverbial piece of string ?

.

It would depend upon the lathe, but ... assuming the Schlesinger doctrine, something less than one thou' concave.

MichaelG.

> Facing a 4" x 3" in the chuck - how far out from a flat surface will this be ?

It depends, but on a typical lathe it could be dished by a thou or more. When I made the t-slotted table for my lathe I worked out the error and shared it out across the whole feed-in distance, tweaking the cut by a quarter-thou (estimated) at regular intervals. Rubbing the finished surface on fine wet and dry over a flat plate of glass highlighted the concentric rings then allowed me to pretty much lose them and get a decent flat surface. It would have been (still is, I suppose!) a good surface to complete by scraping.

Neil

Thanks Guys.

I think I new that I would have to make up a simple fly cutter. I just had this thought pop into my head about an end mill mounted eccentrically in four jaw that I just had to ask the question.

Peter

The link to the photo clearly shows a ground tipped tool for flycutting. The text refers to cutting a slot with an end mill mounted in a collet. This is not flycutting with an end mill.

Martin

Edited By Martin Connelly on 02/01/2016 23:40:56

The intention of my comments was simply to raise the awareness of the effects of the cross slide construction, small though they may be. The likelihood of it being important to anyone during day-to-day (or maybe even year-to-year) work is small, but ...

Neil's job is a case in point - without his attention to the effect, the error at the top of a tall, small-footprint workpiece mounted toward the extremities of the fly-cut surface would definitely be measurable, and most unwelcome.

[/soapbox]

Roger

A one thou dish in a flat surface 4" x 3" would take only a minute or two to bring to dead flat by holding the job in the vice and using a 10" mill file on the top surface. First from one direction, then at 90 degrees, keeping the filing even across the width. The concentric tool marks on the face give a very good guide as to how you are progressing. I do it this way quite often. The result can be double-checked with bearing blue on a sheet of glass, lathe cross-slide table etc.

And it is a good thought. One I have had too, but never tried it out. Might be worth a try just to see how it goes.