Large Fly Cutter

[Smouser]

I made myself a large fly cutter for my Elliott TV2 milling machine.

One of the main reasons for the fly cutter was to try and clean up repairs to welded repairs on a pillar drill table.

Background: I previously made a thread of my cast iron welding adventures.

I bought the 280mm disc for the fly cutter from Rapidmetals.

The first job was to clean it up on my lathe. It was too big for the 3-jaw chuck so I had to use the 4-jaw independent.

Next up was to weld a piece of metal onto the plate which will later become the bit the arbor engages with.

I don't weld enough and suffer massively from skill fade.
Luckily, things can be made to look good with grinders and lathes

Cleaning up the weld.

 

[Smouser]

Drilling the hole for the arbour.

On to the milling machine to make the slots with which the arbour's driving dog can engage.

I then made a washer/plug for the bottom of the fly cutter.

Arbour bolted up.

Finally, I milled a slot out on the disc so that a tool holder could be fitted and I also tapped two holes which would later secure the tool holder.

 

[Smouser]

TNMG tool holder installed.

The reasons I chose TNMG inserts are:
1. I have an abundance of inserts
2. They are pretty tough and should hopefully be able to cope with interrupted cuts on weld spots
3. I had an extra tool holder

I cut the excess off the tool holder and installed the tool holder onto the fly cutter.

The test/experiment piece

Keep in mind, the vast majority of the time, I'm pretty clueless about what I'm doing, around 90% to 95% of it.
'Fake it till I make it' is a personal motto of mine.

I set my Chinese Wen Ding power feed to as slow as it will go but it easily stalls/produces jerky table movements.
It seems the power feed can't quite go slow enough without running out of torque.

I quickly recorded the first runs of the fly cutter (shaky camera, poor lighting etc.) but it will at least give you an idea.

As I have already said, my power feed can't go slow enough, so I just kept increasing the rpm on the mill to try and get a smoother finish

@RobCox promptly berated me for the 2000 rpm / 2500 rpm runs. Something to do with the surface speed and melting the surface of the test piece

Anyway, here are some photos I took of the test piece after varying runs and rpms.

Macro photo

I hope I can improve on that in the future.

 

[Seadog]

You probably have too small a tip radius for a perfect finish.

 

[Smouser]

You probably have too small a tip radius for a perfect finish.

Maybe.

I can try a different holder and insert (will need to buy).

Do you have any specific insert shape/types you think will work better?

The fly cutter can also probably do with a counterweight on the 'disc' on the opposite side of the cutter.

 

[minimutly]

Two things above which I would recomend - but can't you just get a bigger radius cutter?
Slowing the feed down would be a plus as well, and you must have the head truly trammed to avoid concave surfaces.

 

[Seadog]

Maybe.

I can try a different holder and insert (will need to buy).

Do you have any specific insert shape/types you think will work better?

The fly cutter can also probably do with a counterweight on the 'disc' on the opposite side of the cutter.

Not off the top of my head.

Slowing the feed down would be a plus as well, and you must have the head truly trammed to avoid concave surfaces.

He's already said that he can't slow it any more.

 

[minimutly]

Not off the top of my head.



He's already said that he can't slow it any more.

Yes but it needs to slow down - might mean an inverter drive supply to the table? new gears inside it? A gearbox between the drive and the table?
Failing that live with the result of a flatter nosed cutter, maybe get one that can be shaped on a diamond grinder?
Actually, I like the idea of a reduction gearbox - so square shaft out of the WenDing, drives a ring gear, which dives a pinion offset to the side, which has a reduction to another pinion driving another ring gear with a square drive onto the lead screw - four sc gears, something like 4 to1 reduction?

 

[Kram]

Nothing wrong with high rpm carbide likes it and particually if you cant slow the feed, provided its making decent chips. A light oil will help with finish.

Fly cutting is a "light finishing" operation whereby its ideal to use one a bit sharper and worry less about it being intermittent.
I found the aluminium/non ferrous grade of milling inserts, APKT1604 H01, to be excellent and reasonably durable on steel - my lathe doesnt have the rigidity for blunt inserts on a large facemill.

I suspect proper face milling inserts will give much better results than lathe types, they have different geometry.

 

[Agroshield]

In the photo, the slot for the cutter looks to be in line with the centre of the disk.

That means when you clamp in the cutter, the cutting tip is 'above' centre.

That is going to change the rake and clearance angles of the native insert.

I do not know how much that affects the cutting action.

If you look at a traditional flycutter that takes an HSS bit, the top of the toolbit slot (not the middle) is on or very close to the diameter of the holder.

Suburban Tool make a very nice flycutter. If you look at their insert holder, the insert pocket is very deep, so the cutting tip is roughly midpoint of the holder.

https://www.subtool.com/st/fcs_fly_cutter_sets.html (see also opening still of this video:

)

I suspect proper face milling inserts will give much better results...

How would you hold the inserts? Have you a drawing for the insert pocket for an APKT insert? I would respectfully suggest that Suburban Tool know what they are doing.

 

[Smouser]

I did make the slot for the tool holder to the side so that the tip is on centre with the arbour/axis of rotation.

Crude drawing to illustrate the slot's location.

 

[iNf]

That's a rather large lump of metal to be spinning at those(2000rpm) speeds. Usually you use the same rpm/ diameter as when you turn in the lathe. If you can't alter the powerfeed then feeding by hand looks like the only option. One possible way of getting a ' rounder' tip might be to tilt the cutter slightly outwards so you're cutting slightly on the side of the insert

 

[fizzy]

Lovely job - there are a few good videos on Youtube showing them.
Must get around to making one - although as I have 4 surface grinders not really a priority for me yet.
Very nice tool to have though

 

[Brad93]

TNMG tool holder installed.

View attachment 448276


The reasons I chose TNMG inserts are:
1. I have an abundance of inserts
2. They are pretty tough and should hopefully be able to cope with interrupted cuts on weld spots
3. I had an extra tool holder

I cut the excess off the tool holder and installed the tool holder onto the fly cutter.
View attachment 448277

The test/experiment piece

View attachment 448278

Keep in mind, the vast majority of the time, I'm pretty clueless about what I'm doing, around 90% to 95% of it.
'Fake it till I make it' is a personal motto of mine.

I set my Chinese Wen Ding power feed to as slow as it will go but it easily stalls/produces jerky table movements.
It seems the power feed can't quite go slow enough without running out of torque.

I quickly recorded the first runs of the fly cutter (shaky camera, poor lighting etc.) but it will at least give you an idea.

As I have already said, my power feed can't go slow enough, so I just kept increasing the rpm on the mill to try and get a smoother finish

@RobCox promptly berated me for the 2000 rpm / 2500 rpm runs. Something to do with the surface speed and melting the surface of the test piece

Anyway, here are some photos I took of the test piece after varying runs and rpms.

View attachment 448279

View attachment 448280

View attachment 448282

Macro photo

View attachment 448281

I hope I can improve on that in the future.

I'm gonna break our elliott if you want to buy the table motor/gearbox

 

[Brad93]

you're a braver man than me spinning that at that RPM unbalanced

 

[Smouser]

you're a braver man than me spinning that at that RPM unbalanced

Maybe just more stupid

 

[8ob]

Someone on here once mentioned that one downside of a large fly cutter is it can cut a trough in the finished surface if the head of the mill isn’t bang on.

Bob

 

[minimutly]

Someone on here once mentioned that one downside of a large fly cutter is it can cut a trough in the finished surface if the head of the mill isn’t bang on.

Bob

^ #6

 

[frank horton]

how about a button tip.....
I made a fly cutter but not as big as ur's tho.....
run up the head untill it vibrated then backed it of a bit......
no way could I get the table feed slow enough so did it by had......
pretty much a rubbish finish but no matter on this job as it had to be just flat......
will totaly reveiw the feed gear box, prob add another small g/box that just slips on for jobs like this.....
I'm not convinsed that spending 100's of £'s on a DC drive is the way to go.....well for me anyway....

 

[minimutly]

how about a button tip.....
I made a fly cutter but not as big as ur's tho.....
run up the head untill it vibrated then backed it of a bit......
no way could I get the table feed slow enough so did it by had......
pretty much a rubbish finish but no matter on this job as it had to be just flat......
will totaly reveiw the feed gear box, prob add another small g/box that just slips on for jobs like this.....
I'm not convinsed that spending 100's of £'s on a DC drive is the way to go.....well for me anyway....

A gearbox project if you can cut gears is doable though