# My New (Big) Fly Cutter



## darkzero

I do have a 2.5" facemill which I use a lot but I also like fly cutters as they give a better surface finish (IMO). The FM can hog out more material than a fly cutter though.

On my project list was to make a fly cutter that will cover up to 6". I didn't want to make a big conventional styl fly cutter with a long cutter hanging out, I'd like to keep my body parts intact while I'm alive. Well I came across one very similar to what I had in mind to make. It's shop made but not by me.

With it, I got 2 other fly cutters for not much more. I don't own any other fly cutters myself so I figured why not. They are all made of 1045 & have 3/4" shanks. I have only tested the big one as that's the only one I cared about.

Well, they weren't as nice as I hoped them to be. For the smaller ones, the body to shank weren't as concentric as I would have liked. No big deal really as they are fly cutters but I was able to fix that up myself so I'm still happy with my purchase. Knowing what I know now after purchasing them, I probably wouldn't have bought them again but it did save me a lot of time not having to make them myself.


Here's what I got.







The big one is 5" dia & can easily cover over 6". It holds 2 tool bits. I'm not actually using 2 bits for cutting though, I only installed the other one there for balancing & it's set higher than the other so only one is actually cutting.




Test cut right out the box using the China C5 tool bits it came with on 6061. Finish is not bad considering I'm using C5 & I did not touch up the cutting edge or anything. Could be a lot better that's for sure.







The big cutter is heavy, I don't like the straight shank on it so I'll be converting to to R8. I also have a new tool bit coming. I'll post an update here.


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## kd4gij

looks good. was that a 1 off or is it for sale some where.


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## darkzero

I got it from ebay seller tmkr-1916. Looks like they list them one at a time as the package I purchased is not up right now. 

The 3 that I got were like $134 or something buy it now. I got it for the minimum bid of $99. They do sell just the big cutter with an R8 shank for $118, min bid $89. So figured for $10 more, might as well get the 2 other small ones. They even sell a bigger one for $169 (min $125) but that's way more than I wanted to spend & too big for me anyway.


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## Rbeckett

That is one huge fly cutter!!!!   Just the weight alone would help power through a tough cut, do you think it will be prone to picking up vibration from such a huge swept area?  I can't imagine ever needing anything that large, but at least I know where to find one of I do.  Thanks for the tool drool!!!  Just gotta get a napkin to wipe it all off the keyboard now.
Bob


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## darkzero

Haha, thanks Bob! I did have slight chatter at the end of one pass. But I'm not sure if that was cause the set screws for the tool bit was loose or cause I only had 1 tool bit in it for that pass. I hope it was the latter as I wouldn't want a tool bit flying out! I think I'm going to slot my new tool bit when I get it so it can't fly out. 

With only 1 tool bit I can feel a slight vibration & is why I installed the second one. With the second tool bit installed it runs very smooth. I don't have a BP style mill so I'm sure it would do fine on a bigger knee mill. The piece I'm facing is 5"x7" and it faced the whole thing pretty nicely.


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## darkzero

Got my R8 arbor yesterday, today I machined it to fit the big fly cutter. I used a boring head arbor.


Here's the stock 3/4" straight arbor & the new R8 arbor. The thread for the fly cutter is 15/16"-16 & the boring head arbor is 1-1/2"-18. The R8 arbor is hardened, but not that hard, so it took some time to get it down to size. Good thing is I'll be left with a large mounting flange which should add more rigidity, although it was fine with the straight shank.




Turned down, recessed the flange, single pointed the OD thread, & tapped the internal thread.










Excellent fit with about 1/2 a thou run out. I'm pretty happy with how it came out.













My new tool bit & inserts should be here Tues. Can't wait to test it out!


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## FOMOGO

Nice job on the arbor. I have a couple of old Harley crank wheels I'm thinking about making fly cutters out of for cylinder head cutting. Mike


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## cammer

look up myfordboy.com  he is in england. he shows how to make a neat fly cutter any size you want


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## darkzero

Update (sorry I got caught up with other work):

Got my indexable tool holders & I'm very happy with the results!


I went with SCLCL holders & some generic CCMT 21.52 C2 uncoated inserts.




The Micro100 one is 5/16" so I had to mill it down to 1/4" to fit the smallest fly cutter.




The TMX one is 3/8" so no need to mill it down but I did need to shorten it to fit the large fly cutter. Also made a dummy shank out of 1018 to fit the opposite side for counterbalancing which works great.




Also picked up a cheap SRDCN holder that uses RCMT 6mm round inserts. I have alumn specific RCGT inserts already so I figured I try them also. Also shortened the shank so it would fit the large fly cutter if I wanted.




The small & medium size fly cutters.




Yeah, yeah, I know, enough already & onto the results.

The large fly cutter with CCMT 21.52 insert.










And the medium size fly cutter with RCGT insert.







As you can see I'm pretty happy with the results. I think I can get a better finish with the round inserts if I mess with speeds & feeds. The CCMT inserts seem to cut more freely though & I think I'll stick with CCMT on the large fly cutter.

That's the end of my fly cutter saga & searches. Thanks for looking.


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## JeepsAndGuns

I just did some fly cutting for the first time. Mine came with my mill and is pretty small (uses 1/4 tool bits) 
I had acceptable results. I really like the ones you show that use a carbide insert tool bit. Looks like you had a much better surface finish than I did. I may have to look into one of those.


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## zmotorsports

Awesome looking flycutter Will.  Great job on converting it over to R8 shank too.

Mike.


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## Ulma Doctor

Sweet flycutter!!!!
wow, that's a nice finish with the round inserts!!!


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## Andre

I think the reason the CMMT inserts cut freer because they have much less contact with the work, but the round insert gives a better finish because the relief angle is gradual and lets off cleaner than a more distinct point. That's the same findings I have found on HSS flycutters for smaller ones I use a 1/8" corner radius and zero rake, and on the larger ones I use a 1/32" corner rad on a RH turning tool profile with about 7* of rake. Flycutters are fussy for sure!

I wonder if you could use the large double flycutter, and have the CMMT do the bulk of the cutting then have the round insert trailing behind maybe 1/8" and set to a .002" cut? That might be cool!


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## rgray

Nice ...very nice. Didn't think those arbors would be machinable. Figured they would be hard hard hard. Is it that they are just case hardened, or are you using some magic your holding out on us?............Looks like it makes a very nice finish....can I ask what RPM you turn the big one?


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## kvt

Looks nice,  I want to make a large one for doing some items,  but it is down the list a bit. The mill came with a small one that is working for now,  Jut takes several passes for some items.    For some reason all these projects just keep making the list longer,   Oh well,  some times they get shifted based on what I'm needing at the time,  Right now I'm going to have to make a knurler in order to finish a project,   First I have to decide diamond or straight.


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## darkzero

rgray said:


> Nice ...very nice. Didn't think those arbors would be machinable. Figured they would be hard hard hard. Is it that they are just case hardened, or are you using some magic your holding out on us?............Looks like it makes a very nice finish....can I ask what RPM you turn the big one?



Thank you. Yeah I didn't think so either. I figured if anything I better buy an import, but it wasn't the crapiest import. I got the Pro Series from ABS Import tools. They're actually pretty nice & I have a few others from them, full electroless nickel plated.

I new it was hardened but figured it was only case hardened & couldn't be that hard. One of my files was able to bite into it. But I had to take small DOCs to bring it down to size, well for my 12X lathe anyway. This made me worry on whether or not I was able to single point it & tap it. As you can see I managed fine, I did use a Kennametal nitirde coated cobalt vanadium tap which tapped it with ease. I had it on hand as that is what I use for Ti 6-4.

For the big one, I had it spinning at about 1200 RPM.


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