How do I Sharpen HSS Blanks For Fly Cutting?

[Ulma Doctor]

Hello Friends,
When removing material from stock on a mill, i have never used a fly cutter.
I have always used end mills of varying dimensions.
none of my experience is in a production setting.
mainly, one off reproductions for replacement of factory components, either no longer available or way to costly to consider having some one else make them.

I try very hard to get materials that are factory quality or (in my sole estimation) better than OEM materials.
I've had a problem for years on a particular brand of saw that is very well made but has 2 Achilles' heels
#1 Cost, it's very expensive in it's market and is an industrial quality piece of equipment.
#2 Use of Derlin parts where metals should be used.
Which brings me around to my point....

I'm in the process of reproducing one of the Achilles' heels out of 6061 Aluminum Bar from material i'm going to re-purpose.
the material is 2 1/2" Square and i need to remove approximately 35% total material from 2 faces.
i considered using a large endmill and just goin' at it, but i have a set of fly cutters that accept square bits
i have not used a fly cutter ever, and i want to remove more material per pass.
secondary to that i would like to learn how to grind the tool correctly for flycutting.
i'm proficient at grinding HSS blanks for the lathe, but i'll admit i have no idea how to do it for the mill.
rather than damage my work piece or wreck something else i thought i'd ask the gentry here.
I'm sure i'm not the only one who doesn't know, maybe it will help someone else as well...
Thank you in for taking the time to read and post your explanations
mike)

 

[TomS]

Hello Friends,
When removing material from stock on a mill, i have never used a fly cutter.
I have always used end mills of varying dimensions.
none of my experience is in a production setting.
mainly, one off reproductions for replacement of factory components, either no longer available or way to costly to consider having some one else make them.

I try very hard to get materials that are factory quality or (in my sole estimation) better than OEM materials.
I've had a problem for years on a particular brand of saw that is very well made but has 2 Achilles' heels
#1 Cost, it's very expensive in it's market and is an industrial quality piece of equipment.
#2 Use of Derlin parts where metals should be used.
Which brings me around to my point....

I'm in the process of reproducing one of the Achilles' heels out of 6061 Aluminum Bar from material i'm going to re-purpose.
the material is 2 1/2" Square and i need to remove approximately 35% total material from 2 faces.
i considered using a large endmill and just goin' at it, but i have a set of fly cutters that accept square bits
i have not used a fly cutter ever, and i want to remove more material per pass.
secondary to that i would like to learn how to grind the tool correctly for flycutting.
i'm proficient at grinding HSS blanks for the lathe, but i'll admit i have no idea how to do it for the mill.
rather than damage my work piece or wreck something else i thought i'd ask the gentry here.
I'm sure i'm not the only one who doesn't know, maybe it will help someone else as well...
Thank you in for taking the time to read and post your explanations
mike)

IMO machining 7/8" of material from two sides of a 2-1/2" square piece of aluminum using a fly cutter is a lot of machining. Depending on the rigidity of your milling machine I would say a .050" depth of cut by 2-1/2" wide is a lot to ask of a fly cutter. Again, that's my opinion without knowing what type of mill you have and the condition it's in. I would approach this by removing most of the material with a roughing end mill then finish with your fly cutter. This would be much faster and easier on your mill.

Now to answer your question about grinding a tool bit. I'm assuming your fly cutter is at least 2" in diameter and has a slot for at least a 5/16" HSS tool bit. I grind my fly cutter tool bits just like a lathe turning tool for machining a shaft from left to right up to a square shoulder. Again I'm assuming your fly cutter tool bit slot is at an incline from the horizontal. Wish I had a picture of my tool bit to show you but I'm out of town and can't take a photo.

Hope this is helpful information and your job is a success.

 

[DMS]

I used to try to get a fancy grind on my fly cutter bits, but now I just use a left hand turning grind like TomS suggested. Make sure there is a decent radius, and give it a once over with an india or arkansas stone. Fly cutters are not known for taking huge cuts, mainly they take really wide, shallow cuts. The main benefit is a really fantastic surface finish. They are also really great at throwing material further than any other cutting method ever conceived. I was using my fly cutter to square up some steel blocks (2x4x4.5). I had the diameter set to about 3", and was taking about 0.025". I was getting pretty decent finish considering it was A36 steel. This was with a HSS bit, so I had to turn it pretty slow; after that I broke down and ordered a Tormach "Superfly", which should be here tomorrow. I guess I'll see if it is an improvement at all.

Ideally you want to set your fly cutter so that it covers the whole surface in a single pass.

I don't really understand your statement about removing 35% of the material from a face, are you cutting a step? In any case, you will probably get better material removal from a roughing endmill. I have started using these recently, and I really wish I had started earlier; they really just hog out material like nothing else.

 

[GK1918]

Hi Mikey, Its a plain sob for me to explain things without a pics. and for me a pic. is way harder to make or load in this thing - it take hrs. sometimes it works some times it refuses. Anyways, I am old school so for you, I would put a HSS blank in the fly holder, and lower the quill to the work (anything)
so it touches. Now take a hard look at it. Place something sqare against it and mark with a sharpe. grind that angle, put it back in- lower quill it now is flat to the work, do the same on the end to get that angle. Put it back in and it will be flat to the work. Now another hard look at it to grind a little releif angles and a little rounded edges. Now with a piece of soft junk rotate by hand and watch what it does. Like in slow motion you are looking for 'like', a new razor blade. Now tweek it or whatever it takes. I keep in mind of one of them ginsue knifes. Its a try & grind and a grind & try thingy. You will find after spending time or much time this will be imbedded in your mind, and it will become automatic. These things the old man taught me, he taught me there is no shame in using a string to measure things or No shame in two sticks to measure things. Seems everybody thinks high tech not so here.
I'll see if I can draw something up for ya. is this any help? the bottom is the end view:: sam

 

[GK1918]

I forgot to add, that I gave up on stoning my grindings, what does work for me is my trusty air grinder with a cut off blade held sideways, it does take
a steady head I just figure if some dentist can I can. I think I can say, is that, a fly cutter is kind of like " a rotating shaper tool" and just for kicks I fly cut
a piece and shaped a piece and the shaper won????

 

[Rbeckett]

A surfacing pad on a die grinder will also polish up a hand ground HSS bit quite nicely pretty quickly. There are several grits available and I use the brown course 3M pads marked Roloc. They are a tad more expensive, but last much longer and do not leave a bunch of scratches on your freshly smoothed surface. Takes a minute or two to get a really nice even shine.

Bob

 

[Bill C.]

Hello Friends,
When removing material from stock on a mill, i have never used a fly cutter.
I have always used end mills of varying dimensions.
none of my experience is in a production setting.
mainly, one off reproductions for replacement of factory components, either no longer available or way to costly to consider having some one else make them.

I try very hard to get materials that are factory quality or (in my sole estimation) better than OEM materials.
I've had a problem for years on a particular brand of saw that is very well made but has 2 Achilles' heels
#1 Cost, it's very expensive in it's market and is an industrial quality piece of equipment.
#2 Use of Derlin parts where metals should be used.
Which brings me around to my point....

I'm in the process of reproducing one of the Achilles' heels out of 6061 Aluminum Bar from material i'm going to re-purpose.
the material is 2 1/2" Square and i need to remove approximately 35% total material from 2 faces.
i considered using a large endmill and just goin' at it, but i have a set of fly cutters that accept square bits
i have not used a fly cutter ever, and i want to remove more material per pass.
secondary to that i would like to learn how to grind the tool correctly for flycutting.
i'm proficient at grinding HSS blanks for the lathe, but i'll admit i have no idea how to do it for the mill.
rather than damage my work piece or wreck something else i thought i'd ask the gentry here.
I'm sure i'm not the only one who doesn't know, maybe it will help someone else as well...
Thank you in for taking the time to read and post your explanations
mike)

Also make sure you zero in the head of your milling machine. Fly cutters show everything when it comes to alignment. I have used fly cutters, they are a good tool for large surface clean up. Depending on the diameter of the cut and the rigidity of your milling machine. I remember borrowing one to clean up some HRS plate stock years ago. Sometimes HRS has a crown on one side and a valley on the other.

 

[DMS]

I got my SuperFly earlier today, and of course, couldn't wait to try it out. I was squaring up some 6061 stock, and tried it out with one of the aluminum specific inserts. FANTASTIC! At 3.25" diameter, I had noticeable chatter at 0.020". Pulled the the cutter in to about 2.75", and things were much better.

 

[PurpLev]

I use "regular" left hand grind on my fly cutter with a slight modification on it of making the angle a bit shallower because the presenting angle on my fly cutter is very shallow to begin with (If I would to do it again I would make the angle on my fly cutter more 'standard' to be able to use any left hand ground tools 'off the shelf').

Also as mentioned - fly cutters are finishing tools. I normally take .002 - .010" cuts with it as a last step on a surface to clean it up, but not as a roughing tool to remove a lot of material as the tool isn't the most sturdy in it's design.

I would recommend cutting (bandsaw/etc) as close as possible to finish line as you can/comfortable with, rough machine to being the surface within .010-020 to final dimension - and then use fly cutter to give it a nice surface finish. your miles may vary obviously.

 

[LJP]

I find all this information very helpful concerning flycutters. I am in the process of learning how to use a flycutter as well.
I hope this is a relevant question and not a "hijack".

I have some steel with a rusty surface on all faces. Is a flycutter an appropriate tool to clean up a surface with rust?

Thanks, Larry

PS: Sam, your drawing was a great help!