Flycutting - need help total noob.

Just ordered a basic flycutter for my hobby mill (SIEG Super X1LP) and thought I might give it try on aluminum.

Getting a bit confused about the cutting tools. Can I just buy a square tool slap it in and use it ?? Or is it must that I grind it before using it.

Is there anywhere that sell pre-ground tools for a flycutter or maybe somebody on here could help me out with grinding it.

From another newbie.

Sadly you will have to grind the tool. If you look at 'toms techniques' website where he is squaring the stock on his latest project he does go through the grinding of such tools.

Essentially it's the same grind as a lathe cutting tool.. just because it's presented to the work upside down and it's the tool that's spinning just makes it a bit weird to get your head around (I had to draw myself a few doodles to get it straight) The important aspect I find is gettign the end radius right. For ally it's about 1/16th of an inch typically and you really do have to stone it smooth to get a good finish. It's also better (for me anyway) to use a smaller flycutter when practicable so any slight tramming errors on the mill show up less.. to the point that I re-tram if I put the vice on compared to the mill bed itself. And thats a pain on my mill..one of those where as you tighten the head bolts it just moves a touch and can be a boring fiddle to get right.

Justlike a lathe tool you need clearance below the cutting edge (below on a lathe tool, above on a fly cutter), clearance behnd the cutting edge on a lathe tool is below the edge on the flycutter and end clearnace on a lathe tool is below the free end but behind on the flycutter free edge. Yeah, confusing...

Don't panic, As a 'starter for ten' you can use the same right hand knife tool (look it up) as you use on your lathe. This is not by any means the best shape, but will do. It takes very little to grind one up. Then you can examine the cutting geometry and work out a better shape. Doing so will improve your understanding of waht is going on.

Otherwise search through Bogstandard's posts for his recommendation and pictures.

Go here to get Bog's flycutter info. **LINK**

Bert

Hmm... my gut feeling tells me a right hand knife tool doesn't work in a flycutter (unless the mill can run counterclockwise)

Sure, look it up!

Regards, Frank

Hi Jamie, go to tomstechniques.com website, and view the instructional videos - there is one on grinding HSS tools. Then click on the Reference section, Charts, and there is a chart on the angles for grinding a flycutter toolbit that is very easy to understand.

The tomstechnigues.com website has a load of good videos giving instructions on various aspects of tasks in the workshop, plus step by step videos on a couple of projects. All are very interesting and informative, to me as a relative newbie anyway, and he promotes a "common sense" approach to getting things done. I have learnt a lot, well worth a look, I hope you find it interesting. I obviously have nothing to do with the website other than being an interested pupil and observer!

Chris

Perhaps it's a left hand tool then. As PGK says it gets rather confusing thinking about it upside down and back to front.

It should be a left hand tool.. this presents the cutting edge to the material in the correct orientation with the mill motor / quill rotating clockwise ( normal rotation )

George.

A left hand lathe tool can be used,but it needs a lot more front clearance as it is working as a boring tool,eg just take a fly cutter and plunge it verticaly a few thou into a piece of metal, it effectively machines a circular groove the front clearance on the tool must be within the circle or it will rub, this why a insert tipped lathe tool does not work correctly in a fly cutter ,the tip needs to be set at the same angle as a in a boring tool.A very good finish can be achieved by setting the vertical head over a shade from true vertical,this will eliminate back cut,set it over too much and the machined surface will be hollow in the centre.

.

Where "too much" is, strictly speaking, any number not equal to zero

Seriously though ... excellent advice for general work.

MichaelG.

If the head of your mill is perfectly vertical then no matter what type of milling cutter you use it will give a cross hatch type pattern to the work. This applies to flycutters as well, except, if you're using a fly cutter with a radius equal to or greater than the workpiece. In this instance you can face off a piece of work and get nice arced cutting marks provided you stop once the axis of the cutter has reached the edge of the work. For most purposes I use quite a large radius on my flycutter but on one job I did recently I ground a smaller radius and traversed the workpiece quickly to leave noticeable machining marks which looked very nice IMO. Not somethinfpg to be used all the time but for non critical faces it can look nice.

Another very good video on fly cutter tool grinding is my mate the other Tom, Tom Lipton at Oxtool

https://www.youtube.com/watch?v=tCrJVYF95aE

I can heartily recommend his grind, although i do do it slightly differently myself but that is because I don;t have a standard design flycutter.

As for cross hatching, it is a sign that your mill is set up right not a flaw.

chriStephens

I wasn't suggesting it was a flaw, just that it doesn't always look nice and as said it can be avoided on small parts.

Hi Vic, I must admit I am in two minds about which looks better, but i always try to file away machining marks so it makes little difference in the end one way or the other.

c

Sand blasting does a good job of hiding machining marks and looks nice as well. Also easily touched up if parts get marred.

Jamie,

Which ever way you go be prepared to grind a tool either to prepare it from as bought or to resharpen it in use.
If you are still struggling to come to terms with all the different hands of lathe tools and which way round they go in a fly cutter may I suggest you that you mount a piece of tool steel in the flycutter body and then take a simple end mill, hold that in one hand and the flycutter with tool in it in the other hand and then look closely and compare the cutting edge of one tooth of the end mill with the same facets of the flycutter.
If you can grind the 3 principal facets on the fly cutter to match what you see on the one tooth of the end mill you will have the basic shape. Take care to take sufficient off the trailing edge of the periphery to create clearance as the cutter describes a circle
You can also refine the front face of the cutter to just cut at the outer diameter by slightly angling the end face, again ensuring you keep about 5 degree clearance towards the trailing edge.

Hope this helps in some way
Bob D