# Flycutter tool



## peterw51 (Oct 24, 2012)

Hi, I have just made the mini fly cutter from the plan posted by rake60 in 2007, I am pleased with the results & have found a piece of tool steel to fit, but I wonder if anyone can advise me on how to grind the tool please?

Peter


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## romartin (Oct 24, 2012)

Hi Peter. 

I suggest you start by searching HMEM for existing threads on the subject of fly cutting.

In no way do I feel myself to be an expert on fly cutters. I have made a fly cutter recently after carefully watching some videos on YouTube. The tool was ground from an old (blunt) 6mm center drill. I have used this fly cutter with acceptable results on both the steel Body and the Reference Tool Holder of the QCTP I'm building as described in a thread in the Tools section. I ground the tool as though it was going to be mounted in the normal way in the Tool Holder on top of the Compound. Following what I saw on YouTube, I gave the tool the shape of a metric thread cutter with a gently rounded nose instead of a sharpish point. Naturally, when you mount the tool in the fly cutter you must orient its angles with respect to that diameter of the Fly Cutter which passses through the tip of the tool. I think that it's important to get this angle reasonably precise. 

I hope this is useful to you.


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## peterw51 (Oct 24, 2012)

Hi Ian, thanks for the response, I was not happy with just having a go myself as I have a micro miller with plastic gears, so I wanted to get it as right as I could so as not the over stress the gears. I have looked at a few fly cutters on the internet, but none showed me the cutting face of the tool.

Peter


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## rkepler (Oct 24, 2012)

For the most part the action of the tool relative to the work is the same as a lathe tool on work.  So for a tool rotating clockwise (looking down at the work) you'd want a left hand lathe tool grind (a tool that cuts left to right on a lathe).  Here's a shot of one that came with come QC tooling that uses a 3/8 lathe tool:


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## peterw51 (Oct 24, 2012)

thanks for the information, I was a little worried about getting it right, the picture gives me a good starting place & is a great help to me,

Peter


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## basement_guy (Oct 24, 2012)

This is the way I grind my flycutter tool.
It works for me.
http://start-model-engineering.co.uk/begin-with-bogs/fly-cutting/


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## Omnimill (Oct 24, 2012)

This is one way.

http://www.homemodelenginemachinist.com/f13/bog-standard-9224/

Vic.


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## clivel (Oct 24, 2012)

I am far from an expert on flycutters - in fact I am more or less a complete beginner so take what I say with a pinch of salt 

My first project was an Elmer's wobbler. While making this, one of the biggest difficulties I had was cross drilling as a result I decided to make a "finger plate" for my next project. I had a suitable piece of hot rolled steel for the clamp, it just needed to be cleaned up and made parallel all round. Being a bit too large to hold in the lathe chuck, I thought that it would be the ideal opportunity to try out the fly cutter that was amongst the accessories that came with my little Unimat lathe/mill.
My first attempt was a complete mess, I made sure that the bit was nice and sharp, I tried various speeds and depths of cuts but the surface looked and felt like steel wool.

Looking for a solution I came across a post by Bogstandard on one of the forums where he he used to post (it may have been here), where he gave details of fly cutter tool bit with a curved tip. After a few minutes at the bench grinder, I managed to produce a shape that looked something like what Bogstandard recommended, I couldn't believe the difference.
Hopefully these two pictures will help with the shape. The actual surface finish actually turned out far better than it looks in the second picture.









Unfortunately Bogstandard no longer posts here, and he has removed many of the images from his old postings. You could try contacting him (he hangs out on the Model Engine Maker Forum) to see if he would be willing to upload the images again.

Edit:
Oh I see that both basement_guy and Omnimill have beat me to it, that's what happens when one takes a coffee break mid posting


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## peterw51 (Oct 24, 2012)

Once again thanks for the info, I will try these tools on different metals,
Peter


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## lampy (Oct 24, 2012)

In my limited experience the rounded cutter gives a better finish. My first attempt at fly cutting I used a cutting tool I had ground for the lathe it gave a very poor finish. A search found the same thread Basement Guy posted, following those instructions I can get a mirror finish fly cutting aluminum.


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## Tin Falcon (Oct 24, 2012)

Peter when I ground my first fly cutter tool I had little idea either. I was trained by the air force as a machinist. but only so much can be crammed into  320 or so hours of training. 
I went with a common sense approach. set the tool in the holder and grind about ten degrees clearance on all angles then add a bit of radius. I personally grinding the cutter end back 10 degrees from verticle this allows  plunge cut to make radii. Hope this makes sense.
Tin


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## peterw51 (Oct 25, 2012)

Yes it does make sense, thank you all for the help the forum members have given. I will grind a piece of steel and try it later,
Once again thanks for all the help!

Peter


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## lensman57 (Oct 25, 2012)

Hi,

I have a Sherline flycutter with the brazed carbide left hand tool, it cuts well and leaves agood finish on Aluminium. I have also ground a left hand hss tool with the curved profile, I use this on my Taig mill and the results are good. I have also read somewhere about a Tangential flycutter, which is supposed to minimise the cutting forces and perhaps is suitable for your mill. You describe yours as having plastic gears so I assume it is a Sieg X1, if so these mills do not like flycutting at the best of times so light cuts and very slow feed is the way to go.
If you could find an hss tool bit with a high cobalt content, M42, it may give you a longer edge life .

Regards,

A.G


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## peterw51 (Oct 25, 2012)

I found a carbide tipped tool with a 1/4 shank & tried this, it looked a good finish but a little rough, so I ground a piece of 1/4 square cobalt toolsteel and put a big rad on it, this when used on my ally test piece gave me an almost a mirror finish, job sorted thanks all of you for the  help.
With just a few hours work & a sort through the scrap bid I now have a most useful & versatile tool, so thank you Rake60 for the plans & you members for sorting me out with the tool.


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## monty621 (Oct 25, 2012)

Hi

We all know those cheap, red-painted, carbide-tipped lathe tools (e.g Harbor Freight) that seem worthless on the lathe. I've had excellent results using one (LH-type) for fly cutting. This has been on steel, cast iron, and aluminum.

Greg


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## peterw51 (Oct 25, 2012)

Hi Greg, thats the type of tool I used first, and this gave an ok finish, this may have improved with altering speed & feed & this is what I would try first on Steel & cast iron. All in all the advice I have been given has been sound & useful. I am new to model engineering & still have a lot to learn, but since joining this forum I have updated my Prazimat Lathe so it will now cut threads, learned how to cut a thread, Make my first steam engine & flycutter.
I have now started on my second engine, a Mine Engine! I think I will be needing some help on this later. working on small items is a thing I have not done before, also I didnt have any small tooling, so I am buying things a bit at a time. I am spending a lot of time in my shed and loving every moment of it.


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## peterw51 (Oct 26, 2012)

with your help this is the cutter, tool & results I got, I am pleased with the results.


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## SilverSanJuan (Oct 26, 2012)

Looks pretty darn good to me!  You've learned well. 

Todd


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