Any recommendations for a 4” fly cutter?

[erikmannie]

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.

 

[erikmannie]

If I were to make my own, I wonder what sized tool shank I would plan for. The Made in India 100mm diameter fly cutters accept a 1/2” shank.

 

[Nutfarmer]

Make your own. That way you have what you want. Mine are all old school and tool bits are high speed steel or brazed carbide. I like the looks of Suburbans , but can’t justify the cost. They do make fine quality tooling

 

[erikmannie]

Here is the Made in India one. There is reason to suspect that it is junky, so I would return it if it was not good enough:

https://www.amazon.com/diameter-cutter-Carbide-Indexable-Drawbar/dp/B09RVFVDXJ#aw-udpv3-customer-reviews_feature_div

 

[erikmannie]

Make your own. That way you have what you want. Mine are all old school and tool bits are high speed steel or brazed carbide. I like the looks of Suburbans , but can’t justify the cost. They do make fine quality tooling

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).

 

[pontiac428]

The best fly cutter design I've used is the Lopre dual cutter setup. Now sold by Flexbar.

https://www.mscdirect.com/product/details/08253247

The way it works is you feed at half your tool tip radius. The first tool roughs, the second tool (set .010 deeper) finishes. So on a .030 DOC pass, the rougher is clearing .020 and the finisher takes a .010 pass. Easy peasy, I use mine on cylinder heads for a perfect finish.

Probably best to make your own, just need to broach two square holes for 3/8 tooling.

 

[erikmannie]

The best fly cutter design I've used is the Lopre dual cutter setup. Now sold by Flexbar.

https://www.mscdirect.com/product/details/08253247

View attachment 441227

The way it works is you feed at half your tool tip radius. The first tool roughs, the second tool (set .010 deeper) finishes. So on a .030 DOC pass, the rougher is clearing .020 and the finisher takes a .010 pass. Easy peasy, I use mine on cylinder heads for a perfect finish.

Probably best to make your own, just need to broach two square holes for 3/8 tooling.

View attachment 441225

+1 on the link to a Made in USA part. I was trying to reach out to 5” or so. I will look for these in a 5” cutting diameter.

 

[erikmannie]

At some point am I making life tough for my spindle bearings here? Somebody on here was saying that fly cutters are rough on spindle bearings.

 

[erikmannie]

As an aside, let me make it perfectly clear that the very next discretionary income that I get is going straight to a forum membership! Since my membership expired, I have only spent money on a regulator rebuild that was already underway, as well as $13 on a WelderSkills membership. Supporting this forum is a top priority for me, & I will get a platinum membership here very quickly.

Along those lines, I think I will use what steel I have on hand here to make an old school 4” fly cutter. Hopefully it is good enough to weld together some cutoffs of round stock which may be 1018, 1145, 4120 or 4140PH. And then buildup the diameter with welding filler material.

Gosh, just give me any reason at all to stick weld something, and I am in!

 

[pontiac428]

At some point am I making life tough for my spindle bearings here? Somebody on here was saying that fly cutters are rough on spindle bearings.

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.

+1 on the link to a Made in USA part. I was trying to reach out to 5” or so. I will look for these in a 5” cutting diameter.

Mine is a 7" cutter. I've seen them from 3" to 10". Still, making your own definitely counts as a USA part.