Any recommendations for a 4” fly cutter?

pontiac428 said:
Two concerns mainly, one is fly cuts are always interrupted, so thump-thump-thump. The other reason is most fly cutters are horribly imbalanced (which is why the two cutter head I posted above is great). For you and I and the rest of us with 3 hp heads, I'd say its not much of an issue within reason.


Mine is a 7" cutter. I've seen them from 3" to 10". Still, making your own definitely counts as a USA part.
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The reality is that I could have come up with the money for an econo-import part (or round stock for shop made), *but* I do want quality and the Made in India one had reviews that concerned me.

I cannot afford a quality manufactured one, and I like your idea of making my own.

I happen to have a lot of welding supplies on hand, so I just need to decide which type of fly cutter to make. Now I am leaning toward making one of each type.

I should have labeled this thread: I am broke & I want to make a fly cutter that can finish a 5” diameter.

EDIT: Upon re-reading your last post, I have tuned in to the issue of imbalance, so I am only going to make the one like you showed. Imbalance does bother me.
 
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Further thoughts:

(1) I usually fly cut at under .002”, & never over .008”. I am often not happy with the finish that I get with a face mill, so the fly cutter is used in order to get a great surface finish.

(2) I would have no idea on a spindle RPM or a feed speed (for, say, a .002” DOC) for the fly cutter shown above finishing the cylinder head. I would guess a low spindle RPM due to the huge diameter of the cutting tool.
 
I'm pretty sure I have all the material you'd need, either round or bar, to make a fly cutter. I'm also pretty sure I have an indexable cutter you can have that works need ideal. Text me some dimensions and I'll have a rummage.
 
mattthemuppet2 said:
I'm pretty sure I have all the material you'd need, either round or bar, to make a fly cutter. I'm also pretty sure I have an indexable cutter you can have that works need ideal. Text me some dimensions and I'll have a rummage.
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Thanks, Matt. You & I texted this evening.

I am definitely going to make my own, and it will be of the Flexbar variety.

I am going to start a new thread on this project.

Link to the “Freebie Flexbar” thread:

www.hobby-machinist.com

New Project: Shop Made Flexbar Fly Cutter

So my budget is zero here, but I can do this. I am going to make one of these: My first concern is that I haven’t yet found a way to make the square holes. I don’t have a broach.
www.hobby-machinist.com www.hobby-machinist.com
 
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erikmannie said:
I do think that making my own is the best idea. I wonder if I should use medium carbon steel (1145?), or maybe some chromoly pre-hard.

For the money that I would have spent on an import fly cutter of questionable quality, I’ll bet I can buy a length of round stock.

One can save a lot of material cost by welding the round stock (that will end up being the straight shank) on to the head. If it is to be truly an integral shank, one would have to turn 4” down to 3/4”.

I think I will use 1018 steel & weld as described above. It seems ridiculous to turn 4” down to 3/4”.

I will try to shove a 5/8” tool shank in there, too. I don’t currently own a quality 5/8” tool shank. I have 3/4”, but isn’t 3/4” obviously too big to put in a 4” diameter fly cutter? There might be a good reason that the fly cutter linked above accepts a 1/2” tool shank (see photo).

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You are over thinking it. Keep it simple.
 
erikmannie said:
I have an econo-import 2-1/2” R8 fly cutter that accepts 5/16” (or maybe 3/8”) tool bits. I use an econo-import indexable tool shank. This setup does really nice work, even with el cheapo inserts. This setup was really affordable!

Now I am looking for a 4” fly cutter. It will be used in an R8 machine, but it would be fine for me to have one with a straight shank.

The problem is that I sure can’t find one that I am ready to pull the trigger on in a 4” (or 100mm) diameter!

I have almost entirely stopped buying products from PRC (for reasons that cannot be discussed on the forum). I would rather spend several days making my own fly cutter than send my money there.

The Made in India 4” fly cutters have some pretty rough reviews, including issues with difficulty in returning the product. Amazon offers the Made in India ones, so that may address any problems with any potential returns.

Am I in the position of making my own here? I would make one with an integral 3/4” straight shank. I would be using a quality LH tool holder (what I call a “tool shank”).

I definitely cannot afford the Suburban Tool fly cutter, even if it is used. That one is too big, anyway.
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If you need some thing to make it out of I should have a piece of 4140 3inch dia. That would work.
 
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