Fly cutter questions

[Batmanacw]

I have watched lots of videos on YouTube of large diameter fly cutters and they mostly seem to be disks. Is this solely for rigidity?

I was considering mounting a 13" long piece of 2" wide by 1" tall piece of aluminum on one of my spare shell mill arbors and punching a hole at 4", 5", and 6" from the center to hold a 1/2" boring bar with two set screws per hole to hold the boring bar sticking out the bottom.

I figure that leaving the bar long will help with balance. I'd cut the boring bar short because length isn't useful. Shorter the better.

I'm sure aluminum might not be ideal but it doesn't swing as much weight and I'll rarely use it. It would be easy to balance with the boring bar in the middle hole and end up pretty well balanced.


I've turned down a job dusting off the top of a tractor head because I couldn't clean it all up in one pass. I'd like to be able to max out at 12".

 

[mmcmdl]

At that diameter balance is the issue . A 12" would mean a 6" swing . Better have a large spindle .

 

[682bear]

You are very likely to get too much flex from that bar, causing bad finishes and inaccurate cuts.

Also, depending on what mill you have, you may end up beating the spindle bearings to death flycutting large diameters.

-Bear

 

[682bear]

A good many years ago, I worked in a machine shop at an injection molding company.

A co-worker machined a 12" diameter flycutter to use on the Leblond milling machine... the Leblond was significantly bigger and heavier than a Bridgeport.

It wasn't long before the spindle bearings gave up and had to be replaced... the company banned the use of his 12" flycutter after that...

-Bear

 

[mmcmdl]

They make machines for doing this type of work . Blanchard Grinder .

 

[matthewsx]

They make machines for doing this type of work . Blanchard Grinder .

I had a couple of pieces for my mill/drill project ground on one of these. Amazing machines, it’s good to realize that we might not be able to accomplish everything we want in a hobby shop. There’s no shame in farming out a job you don’t have the tools to do….

john

 

[Batmanacw]

My goal was to limit the stock removal to 0.005". Small radius on the tool and a couple thousandths per revolution. I'm not imaging too much shaking going on. It very well might flex too much. That's the big gamble.

 

[Cadillac]

When I use a fly cutter .010 is about as much as I take in 1 pass. Usually .005 or less. I use a facemeill when wanting to take more.
I just had a job Monday for work which entailed surfacing a three cylinder head for a engine rebuild I’m doing. Head had a 6” span and my largest fly cutter would only do 4” comfortably. So I ended up making my own bar with a replaceable insert that would swing at least 6”. Took about a hour to make and it worked perfectly. It took a total of .010 to just clean up this head.

 

[Batmanacw]

When I use a fly cutter .010 is about as much as I take in 1 pass. Usually .005 or less. I use a facemeill when wanting to take more.
I just had a job Monday for work which entailed surfacing a three cylinder head for a engine rebuild I’m doing. Head had a 6” span and my largest fly cutter would only do 4” comfortably. So I ended up making my own bar with a replaceable insert that would swing at least 6”. Took about a hour to make and it worked perfectly. It took a total of .010 to just clean up this head. View attachment 442504 View attachment 442505 View attachment 442507 View attachment 442506

That is exactly the kind of job I was looking to do. Very light passes and wide area.

My only reason for doing a 13" long bar was for balance. I only want 12" of coverage. Maybe I'll do an 8" setup first.

 

[Batmanacw]

I'm watching the Suburban tool video and I realized my idea would be much shorter than their design. I might make it just so you guys can laugh at me if it doesn't work. Lol.