# Fly cutting



## remout (May 6, 2010)

Experience Level: Beginner

I have a Tormach cnc mill and I want to try fly cutting some aluminum for a great finish.

I have a 1/2" set screw tool holder for the Mill. I'm thinking I need these two items:

http://littlemachineshop.com/products/product_view.php?ProductID=1152

http://littlemachineshop.com/products/product_view.php?ProductID=1231

If the above is correct, my question is how do I sharpen the end of the cutting tool. In addition to the mill, I have a grinder and drill press.

Thanks!


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## kvom (May 6, 2010)

I would suggest getting a flycutter that uses carbide inserts.


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## Dan Rowe (May 6, 2010)

Grinding a bit for a fly cutter is not really all that different than grinding a lathe bit. Obviously the point of the tool has to touch the work first and the edge that is nearly parallel to the work has to have a slight clearance.

For instructions on how to do this see http://www.sherline.com/grinding.htm

Note figure 7 and that is how the tool should attack the work, only the tool will be rotating and the work will be stationary.

Dan


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## JimM (May 6, 2010)

Haven't got as far as flycutting myself but when I do I'll be giving Bogs' method a go Thm:

http://madmodder.net/index.php?topic=850.0

Cheers

Jim


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## remout (May 7, 2010)

kvom  said:
			
		

> I would suggest getting a flycutter that uses carbide inserts.



I found a picture of one. It appears the inserts give you three cutting faces per insert?

With this setup I would just need to make sure the shank fits my mill.


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## Dan Rowe (May 7, 2010)

There is nothing wrong with using carbide inserts but instead of a fly cutter you might consider a large milling cutter with carbide inserts and a R-8 shank. There are several types of inserts and you will need to research that to make sure that the parts all work together.

The advantage of a fly cutter is it can be used for more than simple flat surfaces. The tool bit by Bogs was new to me but it is a good one for flat surfaces. The one I described can be used to bore a hole as Bob did with his home made fly cutter on post #58 of this thread: http://www.homemodelenginemachinist.com/index.php?topic=8381.45

I have also ground up a bit for a fly cutter for trepanning which is simply cutting out a slug like a hole saw with a single tooth.

So there is more that can be done with a flycutter but you will have to learn to grind tool bits which is the first thing I was tought in shop class.

Dan


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## Lew_Merrick_PE (May 7, 2010)

remout  said:
			
		

> Experience Level: Beginner
> 
> I have a Tormach cnc mill and I want to try fly cutting some aluminum for a great finish.



I normally recommend HSS for flycutting aluminum. You can get a really *sharp* edge on it that is just not possible (without extraordinary effort) in carbide. The "contact point" wants to be a nice broad radius with (about) 15° rake and (about) 7° clearance. A few "tries" will do quite nicely. Finish the cutting edge with stones. I usually go from my off-hand grinder to an "India" stone to a "Soft Arkansas" stone to a "Hark Arkansas" stone.


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## remout (May 7, 2010)

Lew_Merrick_PE  said:
			
		

> I normally recommend HSS for flycutting aluminum. You can get a really *sharp* edge on it that is just not possible (without extraordinary effort) in carbide. The "contact point" wants to be a nice broad radius with (about) 15° rake and (about) 7° clearance. A few "tries" will do quite nicely. Finish the cutting edge with stones. I usually go from my off-hand grinder to an "India" stone to a "Soft Arkansas" stone to a "Hark Arkansas" stone.



Lew,

I'm beginning to understand, I found a wikipedia article on rake and clearance.

http://en.wikipedia.org/wiki/Tool_bit

What is an off-hand grinder. I have a "bench grinder" (one grinding wheel and one wire brush). I also have a couple of dremel style tools.

Thanks for your patience!


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## Dan Rowe (May 7, 2010)

For the definations of lathe tool but geometry see:
http://en.wikipedia.org/wiki/Tool_bit

The tool Lew described is the same as the one that Blogs ground on the link already posted.

Off hand grinding is simply holding the tool bit and resting your index finger on the grinder tool rest. This will keep you from getting the tool to hot and burning the steel. When the tool bit warms up dip it into water. Some grinder stands have a spot for a small bucket of water for that purpose. Mine has a hole that fits the larger size of plastic cups from fast food joints.

There is some stuff on u tube about this but I have not watched the vids to see how good the tips are.
http://www.youtube.com/results?search_query=metal+lathe+tool+grinding&aq=2m

Dan


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## tombstone (May 7, 2010)

Hi Remout
If you are looking for a good inserted side & face cutter for a brilliant finish in aluminium the one in the image is excellent I have used it on 4 & 5 axis machining of 8 foot wing spars no problem, it is a Hertel cutter I dont have the part no. but Hertel was taken over by Kennametal so if you are based in the US you should be able to get info on it. I have the Kenna part no for the inserts 	BGHX15L5PCFRGG these were made in Germany.If you get a cutter like this it is worthwhile getting an arbour to suit your spindle to ensure all the inserts are cutting evenly this is an R8 which would suit you. I used this cutter to cut the 2 top faces and end faces on the case in the Whittle V8 thread images.


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## Lew_Merrick_PE (May 8, 2010)

remout  said:
			
		

> What is an off-hand grinder. I have a "bench grinder" (one grinding wheel and one wire brush). I also have a couple of dremel style tools.



Remout,

Offhand grinding is as described in Dan's response. When you have a dozen of so grinders configured for various tasks, merely saying _bench grinder_ is not fully descriptive. I have *four* _bench grinders_ (all 8" X .75 hole wheel types) configured for different tasks. One has *no* table of any type used for grinding long blades and the like -- called a _machete grinder_. Another has a _round bar table_ that allows me to rest my hand on while grinding contours -- called a _contour grinder_. Another has a set of adjustable supports for a pivot that allows me to grind various radii -- called a _radius grinder_. My _offhand grinder_ has an adjustable (for angle) table that provides access all around the wheels for hand controlled edge grinding.

[Can someone explain to me how I embed a picture? My offhand grinder set-up might be of interest.]

Although I have several standard commercial bench grinders, I have a design that makes an incredibly useful general purpose bench grinder. It uses about 40 lbs of steel, so it has some real heft to it. It has interchangeable table supports with the idea that it will make (almost) any configuration in one unit. The one I built three years ago got sold to a client who just had to have it. My shop fits really nicely in 2500 square feet -- and it is currently crammed into 880 square feet. So I have been looking at "multi-purposing" many of my smaller tools.


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## Longboy (May 8, 2010)

.......Flycutting is just too cool for its finishing effects. You can visually eliminate the joint line of metal pieces butted up against one another! 8)


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## remout (May 8, 2010)

Lew,

The long boring picture story
Many forums don't allow you to load the pictures on their server. This takes bandwidth and cost's money. So you link to your pictures.
One option is www.photobucket.com 
You can setup an account for free and load a few pictures. For a fee you can load all you want. 

If you use photobucket.com, there is a option in your account that reads "sharing -> get link code -> IMG for bulletin boards & forums ". Right click and copy everything in the box (or highlight it and hold the ctrl key and hit the "c" key). Now get back here and while typing your message click on the third button from the left in the row above the emoticons (smile faces).
Two groups of brackets will appear with some html (code) between. Paste the link code you copied from photobucket between the two groups of brackets and when you hit post or preview only your picture will show (not the brackets or code). Below is a photobucket stored pic of a flywheel I cut today in modeling wax.









When you are done and hit post all that will show up is the image.

I bet you are sorry you asked  Hope this helps.


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## firebird (May 16, 2010)

Hi

I haven't tried fly cutting yet but I bought a fly cutter at the Harrogate show last Saturday in anticipation of having to do some.

I had a wander round to Julian's workshop yesterday afternoon, for a couple of beers and a chat and on the way back I just happened to look in a skip outside a house that is having an extension. It yielded 5 off cuts of angle iron 3 1/2 X 3 1/2 ranging in length from 4 to about 6 inch. Can't pass up things like that can you. They could make useful angle plates. A quick check with a square found them to be, well not square. Right then, this is a good opportunity to try out the new fly cutter. A search through the box of might be useful one day tools and I came up with a carbide tipped left hand lathe turning tool with the right size shank to fit the fly cutter, 3/8. The next photo shows the set up. The piece of angle iron is clamped to a small angle block I have to hold it as square as possible and another vise jaw I made holding it the other side.





The next 2 shots are after a couple of light passes









I like it. Not bad for a first try. I'll flip the angle over and fly cut the the other face which should give me a useful angle plate.

This is a shot of the workshop floor after cutting the first face.





The benches and floor are covered, it seems fly cutting throws chips every where. I'm thinking of knocking up a screen of some sort. Eye protection is essential.

Cheers

Rich


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## shred (May 16, 2010)

If you're going to get a holds-a-lathe-tool flycutter like these for the Tormach: http://littlemachineshop.com/products/product_view.php?ProductID=3094&category=
I suggest getting 3/4" shank tools (LMS doesn't sell those, but places like Enco, CDCO and Shars do). Then they can be used as-is or adapted easily to TTS tools. Unless you know now you never want to go TTS, I'd be planning for it (likewise you might want to minimize on R8-shank tools since they're more of a nuisance to swap in)


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