A Small fly cutter

[LandRoverTom]

So while having access to a lathe and milling machine at work and needing something to occupy myself in the evening I found some inspiration and made a small fly cutter, sized for a 6mm tool:

Not quite as good a finish as I'd like but I still learned a bit which is the main thing.

I'm no good at sharpening drill bits so thus far have shyed away from HSS tools, assuming that I'll be terrible at sharpening them too! And also being a bit lazy.
I fianlly tried using one though and got a much better finish than the tipped insert tools were giving me, admittedly I didn't sharpen it from scratch but some light tickling with a stone a couple of times seemed to go ok and helped take a much finer cut than the tipped tool.

Next mojor goal will be HSS tool sharpening I think to sort out a tool to complete this.
Unfortunately I already have thoughts for mkII - a bigger version with a morse taper and a smoother finish

 

[gaz1]

look up tool and cutter grinder on here

ive bought one others have got bargains

others have made there own will do both drill bits and hss tools as well as milling machine bits as well

 

[LandRoverTom]

look up tool and cutter grinder on here

ive bought one others have got bargains

others have made there own will do both drill bits and hss tools as well as milling machine bits as well

I've got a couple of Harold Hall's lathe books which I've been reading. I think I might have to get his one on tool sharpening and have a go at the sharpening rest/guide that I've heard is in it and pick up a few tips and pointers too.

More importantly is I just need to have a go!

 

[gaz1]

look here much better

https://www.mig-welding.co.uk/forum/threads/tool-and-cutter-grinder-build.96763/

 

[Screwdriver]

Very neat.

Opens up a world of opportunity on the lathe. Have you considered blacking it, chem black is stupidly easy and gives great results.

 

[badabec]

I use a Diamond Tool Holder, uses HSS and they supply a jig to sharpen the bit. Easy. Shipped from the UK

https://www.eccentricengineering.com.au/products/diamond-tool-holder/the-diamond-tool-holder

 

[LandRoverTom]

look here much better

https://www.mig-welding.co.uk/forum/threads/tool-and-cutter-grinder-build.96763/

Thanks for the link, I'll have a read though that!

Very neat.

Opens up a world of opportunity on the lathe. Have you considered blacking it, chem black is stupidly easy and gives great results.

I hadn't considered chem black until you mentioned it. Now it sounds like it might be a good idea...
How durable it the coating?
I might get some to try when I've collected a few bits to do.

I use a Diamond Tool Holder, uses HSS and they supply a jig to sharpen the bit. Easy. Shipped from the UK

https://www.eccentricengineering.com.au/products/diamond-tool-holder/the-diamond-tool-holder

They do look good thanks, I'll have a goood read of their website. I did spot a UK distributor as well as them delivering to the UK themselves.

The next step then, any advice or tips (no jokes!) on angles to grind a tool steel for it to get a nice finish...?

 

[optima21]

I'd say for a small flycutter you're best using carbide if you can, hss will blunt quickly or will take forever to cut a flat surface if you use a slow cutting speed.

here are the two small flycutters I use, which are a bit smaller than yours. the one on the left has a 12mm shank and 18mm dia body and uses a broken 1/8 carbide burr reground as a cutter. the one on the right has a 1mt shank and the tool bar is 40mm long. that cutter is made from a blunt carbide insert for a 6" dia face cutter silver soldered to a steel bar, Ive been using that for 20 years now.

one if the advantages of a flycutter is that they can be used with cheap tooling, the carbide is diamond honed though, but using a cheap cup wheel off ebay in a clarke belt and disk sander

 

[Screwdriver]

I hadn't considered chem black until you mentioned it. Now it sounds like it might be a good idea...
How durable it the coating?
I might get some to try when I've collected a few bits to do.

Not that durable with a simple antiquing fluid, good enough to give it a decent finish, some protection from rust and it should age really well. But let's be honest, how often are you really going to use it? Most of the time it's just going to sit there looking pretty.

 

[LandRoverTom]

Perhaps carbide inset tools will be the way to go then instead of grinding tool steel.
Admitedly I don't have a lot of experience but I have had mixed results with carbide inserts and turning mild steel, 50:50 at best I'd say. on the other hand with HSS I'd have to get the hang of grinding the tools...

Talking of speeds, what sort of speed should I be running a fly cutter at for mild steel? it will be roughly 60mm diameter of the cutting tip...

.... how often are you really going to use it? Most of the time it's just going to sit there looking pretty.

Quite true, and looking good is the most important thing! It would certainly hide my poor turing skills in getting a good finish...

 

[Agroshield]

Perhaps carbide inset tools will be the way to go then instead of grinding tool steel.

Someone please correct me if this is wrong, but I think you will need a left hand insert tool to go in the flycutter. For instance, if you are to use CCMT inserts, the cutter shank would have an SCLCL code. Most common lathe tools are right hand.

E.g. http://www.jbcuttingtools.com/epage...oducts/"SCLCL 06"/SubProducts/"SCLCL 0606 06"

A flycutter is a very interrupted cut so choose a grade of carbide suitable for this situation (i.e. unknown spec. AliGood inserts are likely to break your heart).

 

[LandRoverTom]

Someone please correct me if this is wrong, but I think you will need a left hand insert tool to go in the flycutter. For instance, if you are to use CCMT inserts, the cutter shank would have an SCLCL code. Most common lathe tools are right hand.

E.g. http://www.jbcuttingtools.com/epages/es461493.sf/en_GB/?ObjectPath=/Shops/es461493/Products/"SCLCL 06"/SubProducts/"SCLCL 0606 06"

A flycutter is a very interrupted cut so choose a grade of carbide suitable for this situation (i.e. unknown spec. AliGood inserts are likely to break your heart).

Thanks for that link, they give a handy drawing of the profile/type of cut on the page of each tool.

If my mind is working correctly then yes, a left hand tool makes sense I think.
By left hand I mean one that cuts from left to right and in the fly cutter it should be set up to cut on the down stroke so it forces the work piece down rather than on the up stroke as that would try to lift the work which would be less secure?

 

[optima21]

Talking of speeds, what sort of speed should I be running a fly cutter at for mild steel? it will be roughly 60mm diameter of the cutting tip...

run it as fast as you can get away with. for hss, model engineers handbook would suggest 60ft/min for mild steel and 80ft/min for free cutting steel, but that will also depend on the rigidity of the setup, the depth of cut and the feed you use. so at 60ft/min that would be roughly 100 rpm and 80ft/min that would be roughly 150rpm for 60mm diameter, although that does sound to be pretty slow, but I only seem to make small items so just use what speed feels right......in comparison my flycutters will normally be used at 1000 to 1600rpm.

 

[LandRoverTom]

'Recommended' speeds, feeds and depths of cut are something I am struggling to get my head around at the minute. I'm sure they are pretty straightforward but for some reason the penny hasn't dropped yet.
I was thinking it would be slow due to the interupted cutting but on the otherhand thinking that faster would give a cleaner cut and smoother finish perhaps?

 

[optima21]

talking about milling at home (and flycutting) with hss cutters and bits, dont worry about feeds and speeds they are just general, and the ones quoted will normally be for industrial machines, when you would be assuming that the machines are rigid and want to remove the maximum amount of metal with the minimum tool wear. home users will generally take lighter cuts which can extend tool life and you can run higher speeds for finishing cuts. finishing cuts will normally be light cuts so will have less heat generated at the cutting tip so will create less wear, as its the heat build up at the cutting tip which causes tool wear. the interupted cut may need a slower speed as it will introduce vibration on lighter machines which can show as chatter on the parts you're making. just have a play and go from there, you'll learn what works for you and what doesn't.

on lathes feeds and depth of cut can be more critical as they can have a big impact on the shape of the swarf, on some materials that can come off like pieces of string that wrap arround anything, turn the feed and depth of cut and the swarf can come off as tiny chips. (with carbide inserts)

 

[Morrisman]

I'm no good at sharpening drill bits so thus far have shyed away from HSS tools, assuming that I'll be terrible at sharpening them too! And also being a bit lazy.
I fianlly tried using one though and got a much better finish than the tipped insert tools were giving me, admittedly I didn't sharpen it from scratch but some light tickling with a stone a couple of times seemed to go ok and helped take a much finer cut than the tipped tool.

Next mojor goal will be HSS tool sharpening I think to sort out a tool to complete this.
Unfortunately I already have thoughts for mkII - a bigger version with a morse taper and a smoother finish

Understanding the basic principals of rake and clearance make it very easy to sharpen your own drills and HSS tools on a bench grinder. I’ve been doing it for years, it is a very useful skill to have.

 

[Agroshield]

By left hand I mean one that cuts from left to right

Yes. The left- and right- hand terminology comes from a lathe. On a lathe, the chuck is on the left. Generally you are cutting from the right to the left so the most common tool is a right hand tool.

If you need to cut towards the tailstock, on the right, you cut from left to right and need a left hand tool. This is how your flycutter would look if placed in a lathe tool post.

Understanding the basic principles of rake and clearance make it very easy to sharpen your own drills and HSS tools on a bench grinder.

A cheap way to start is a piece of 25mm square wood and a disk sander. You get a super-enlarged version of a tool so you can see clearly the different angles you grind in. Less fiddly to hold than a piece of HSS, does not get hot and burn your fingers and you can mark lines (e.g. 5 degrees) on the platen of the sander using a protractor to help you.

There is a guy on Youtube called Rustinox, who shows some good sketches of the grind angles for shaper tools. These are quite relevant to a flycutter.

 

[DAPPH]

On my ancient 10 inch Sphere I've been using a 1/2" precision square tool steel as a fly cutter tool , ground flat diagonally so one point is the leading edge & proud of the rest when it's set in the four jaw chuck . Put the lathe on a slow speed & slow compound cross feed advancing the work to the cutter a thou at a time . It took about 35 passes for the whole 70 mm face I was working on to get trued up .

 

[LandRoverTom]

Well after a lot of trial and error I cound't get a HSS tool shaped to work well and give a clean cut.
I am also unable to get hold of a 6mm shank insert tool at the minute so I modified the fly cutter to suit to tools I had available and tried a left hand insert tool and I'm very impressed with the results!
0.2mm Depth of cut, between 100 and 200 rpm (I can't remember the exact setting) spindle speed, and the slowest feed rate on the lathe.