Fly Cutters

[kingmt01]

I just started using fly cutters & wow I didn't know what I was missing. Anyhow to the question.

At what angle or direction should the tool meat the work. The slots in my first set turn the bit so that it is angled slightly away from the work at the bottom edge. To me this seems like it would cause the tool to deflect up & ride on top of the work. I put a shim behind it in my first set of cutters to turn it sligthly twords the work so it cuts into it like you would peel with a chisel. I just ordered a new set from Enco to find that these are the same way. Am I wrong in my thinking? By the way the other set will be offered up in a new thread I'll be starting later on. Is like to know if this is a defect in the way the tool is made before posting tho so they know what they are getting,

 

[kingmt01]

I don't know if that was explained well but maybe this makes sense.
Tool meets like this /--- to work.
I changed it with a shim to meet like this \--- /&\ being the tool --- being the work.

I didn't bring the face of the tool. I only ground relief to the bottom.

 

[John Hasler]

I don't know if that was explained well but maybe this makes sense.
Tool meets like this /--- to work.
I changed it with a shim to meet like this \--- /&\ being the tool --- being the work.

I didn't bring the face of the tool. I only ground relief to the bottom.

I grind flycutter tools similarly to left-hand turning tools.

 

[pollardd]

Hi Kingmt,
Can you post some pictures of the cutters so we can see what you mean.
I also agree with John, Fly cutter tool bits are shaped like left hand lathe tools.
Fly cutters suffer a bit more impact than lathe tools as the cut is always intermittent and not continuous like a lathe.
To counter this I put a bit more radius on the nose of the tool.
It seems like you are describing a negative rake angle. The only time I ever needed a negative rake angle was cutting brass or bronze. It stops the tool digging in. You will have noticed this effect using a regular drill bit on brass.

Hope this helps
David

 

[John Hasler]

I just started using fly cutters & wow I didn't know what I was missing. Anyhow to the question.

At what angle or direction should the tool meat the work. The slots in my first set turn the bit so that it is angled slightly away from the work at the bottom edge. To me this seems like it would cause the tool to deflect up & ride on top of the work. I put a shim behind it in my first set of cutters to turn it sligthly twords the work so it cuts into it like you would peel with a chisel. I just ordered a new set from Enco to find that these are the same way. Am I wrong in my thinking? By the way the other set will be offered up in a new thread I'll be starting later on. Is like to know if this is a defect in the way the tool is made before posting tho so they know what they are getting,

I just took a look at Enco's Interstate flycutter sets. I don't see any that come with bits. The bits they offer for them are blanks, as were the ones that came with a set I bought a while back. They aren't ready to use: they have to be ground.

 

[Silverbullet]

When I was in vokie we were taught to make our own fly cutters . We even made them with the bits turned straight down , we sometimes had two or three tool bits in one cutter even set a few with straight and angled . Set the tools using a flt scrap on the bed to make the tools work together. If I remember we used to get some very fine finishes with just a slight radius on the tips of the bits. You can run them either direction with the right bits. I had some 316 stainless clamps we made for trainer missiles for the government I used a fly cutter on because that steel just ate the endmills we used back then . My boss gave me a big raise and a higher position for that smart idea. 2nd shift foreman yupp needed it then too .

 

[kingmt01]

Mine didn't come with any ether. I'm not talking about the to being ground with a negative rake but the holder being machined to cause a slight one. It probably isn't enough to show up it a picture but was enough to see by eye. I stock a piece of paper in it about the thickness of a couple pieces of card stock & that was enough to cause about the same amount of positive take as I had negative. It might have been a bit thicker them card stock.

The one thing I looked at on grinding for a fly cutter didn't show grinding any rake on the front of the cutter. Only the bottom & the nose. It also said to put a little radius on the nose.

 

[pollardd]

I understand what you mean but it is good to use the correct names for each of the angles. That way it is clear what you are talking about.
The angle that makes the chip curl is rake. There is back rack and side rack. Thinking about a lathe tool the back rake makes the chip move away from the work and side rake makes the chip go to the right. The same principles work for a fly cutters only it is round and round.

The other angles are called Clarence angles so that only the cutting edge touches the work.
It sounds like your cutters are fine, you are just expected to create most of the angles yourself on the grinder.
The cutter probably has one of the Clarence angles built in. You should try different angles and see what works best for different materials.
David

 

[kingmt01]

Thanks David for the good explanation. Things are a little more clear. I'm still a little fuzzy on the angles tho so I'll do a little more searching on it. I'm mostly self thought on my machining experience so I probably do several things wrong & don't know the terminology. I do some internet searching, YouTube, & recently reading up here to learn also but mostly I just look at it & try to think it through. Even when grinding the tools.

I assume the tool should be ground so that only the point is contacting the work same as the lathe tool correct?

Also about how much of the tool should extend from the holder? One of them takes a 3/16" tool. I wouldn't think it could stick out very much at all.

Sounds like my tools for the fly cutter at ground wrong but they sure are leaving a nice finish anyway. I guess I changed their clearance to my rake angle & ground the clearance angle when I should have left the clearance & ground the rake. This makes sense now. I guess I didn't think that one through enough.

 

[John Hasler]

Thanks David for the good explanation. Things are a little more clear. I'm still a little fuzzy on the angles tho so I'll do a little more searching on it. I'm mostly self thought on my machining experience so I probably do several things wrong & don't know the terminology. I do some internet searching, YouTube, & recently reading up here to learn also but mostly I just look at it & try to think it through. Even when grinding the tools.

I assume the tool should be ground so that only the point is contacting the work same as the lathe tool correct?

Also about how much of the tool should extend from the holder? One of them takes a 3/16" tool. I wouldn't think it could stick out very much at all.

Sounds like my tools for the fly cutter at ground wrong but they sure are leaving a nice finish anyway. I guess I changed their clearance to my rake angle & ground the clearance angle when I should have left the clearance & ground the rake. This makes sense now. I guess I didn't think that one through enough.

If your cutters are getting the job done and leaving a nice finish they aren't ground wrong. They should stick out of the holder as little as possible.