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Fly cutting

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Qdeathstar

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#1
Hello.

I was fly cutting some steel bolts. I don't think the bolts were hardened because they are chinesium grade.... I followed some guy on on YouTube to sharpen an hss blank for use in the fly cutter, and I am cutting at around 1000rpm.

At a depth of cut of .01" the cuts look good, but if I try to cut .02" the fly cutter turns in the collet... (the collet spins, but the fly cutter does not).

What am I doing wrong? It seems like even if I am cutting too deep, that the fly cutter should not spin in the collet, which makes me worried I do not have it installed in the machine correctly. (A flying flycutter seems like bad times).



Thanks.
 

benmychree

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#2
Sounds like too fast of rotation what cutting diameter is the fly cutter?
 

Bob Korves

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#3
Also, many collet systems only hold material quite close to the nominal diameter tightly. What type of collet and size, and what size is the shank on the flycutter to the nearest .001"? .010" is also a fairly deep cut for fly cutters on many mills. The interrupted cut shocks them pretty hard.
 

Qdeathstar

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#4
I am using a 1/2" collet, I measured the shank using a caliper and got .4988"

Excluding the tool, the fly cutter is 1.5" around. The tool sticks out about an inch.
 

Bob Korves

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#5
What kind of mill are you using? How tight did you tighten it down?
 

Qdeathstar

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#6
i am using a grizzly g0762. How tight is sort of hard to describe. I tightened it down with my hand, and then gave it two-three more turns.
 

Bob Korves

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#7
That mill should handle it no problem. Try using lighter cuts and see how they work for you, then go little by little more if you are not having issues.
 

grzdomagala

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#8
I am using a 1/2" collet, I measured the shank using a caliper and got .4988"

Excluding the tool, the fly cutter is 1.5" around. The tool sticks out about an inch.
That sounds like "swing diametr" of about 3.5''. (Fly cutter body dia + 2 times "stickout"). At this diameter 1000rpm sounds way to high for anything except aluminium - i bet cutting oil smokes?
Formula from wiki https://en.m.wikipedia.org/wiki/Speeds_and_feeds#Spindle_speed produces around 100rpm for mild steel - which sounds more reasonable (but im metric so my "gut feeling" for imperial measurements cannot be trusted)

Wysłane z mojego GT-N7100 przy użyciu Tapatalka
 

British Steel

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#9
I'm with GRZ - way too high a cutting speed! Assuming HSS tool and "average" steel you're looking for about 60 - 100 feet-per-minute where tool meets work - with a fly cutter take the diameter (about 3.5"?)multiply by three and a bit for the tool's travel per rev (in inches) and convert that to feet - so you have a tool travel of around a foot, 60 - 100 RPM would be about right.

Fly cutting always gets me frustrated, the single cutting tool means you can only advance (feed) a few thou" per rev of the spindle, so for e.g. 3 thou" chip load you can only advance about 1/4" per minute at 80 RPM.... Luckily my new-to-me mill's big enough for multi-insert face mills and has 3HP to drive 'em! Just need to spend the money for a few now :/

Dave H. (the other one)
 

T Bredehoft

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#10
Depth of cut (.100 or .200) is a LOT for any but a really heavy machine. Then you would use a multiple insert cutter. Or am I reading it wrong?
 

rowbare

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#11
How big are these bolts? Are you cutting a flat on the bolt shank, or are you cutting the ends or head down? Unless the bolts are massive, a fly cutter is the wrong tool for that job.

For any reasonable sized bolt, a 4 flute end mill of an appropriate size would do a much better job. Fly cutters are best used for larger areas.

bob
 

Qdeathstar

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#12
I am cutting the head shorter. I'm not sure why I went with a flycutter actually, I think it makes a lot more since to use an end mill now that you mentioned it.

I actually did use an end mill to also cut the sides of the bolt head down and to cut a flat on the shank as well.
 
Last edited:

grzdomagala

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#13
Fly cytter is a very useful thing. They don't need to be big - i build one with half inch swing (was an experiment to test if fly cutter for proxxon mf70 is a viable tool). The biggest advantage of fly cutter - it's cheap, easy to repair and sharpen. Biggest disadvantage - it's slow.


Wysłane z mojego GT-N7100 przy użyciu Tapatalka
 

JR49

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#14
Fly cytter is a very useful thing. They don't need to be big - i build one with half inch swing (was an experiment to test if fly cutter for proxxon mf70 is a viable tool). The biggest advantage of fly cutter - it's cheap, easy to repair and sharpen. Biggest disadvantage - it's slow.


Wysłane z mojego GT-N7100 przy użyciu Tapatalka
I couldn't agree more, grzdomagala, and I have an advantage that offsets that one disadvantage--I'm old and RETIRED, so I have plenty of time. Happy Machining, JR49
 
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