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Evan
01-31-2008, 10:26 PM
This morning I decided to make a proper engraving table using the old aluminum milling table that I made for my South Bend. To use it for an engraving table I needed to face it off with the mill to ensure it was as well aligned as possible with the work envelope. To do that properly I needed a fly cutter. So, I made one.

This is a relatively easy project and would be a good project for a new mill owner. It also is a good way to save some coin. The closest equivalent in the KBC catalog is $60. This cost me bits from the scrap bin and a few hours of enjoyable metal working. Once made I used it to face the table which is 7075 T-6 aluminum. With a hardness about 15 to 20% greater than mild steel it takes a beautiful finish. Nothing puts on a good looking finish like a fly cutter. I used fly cutters in the lathe to do much of the machining of the parts for my mill.

http://vts.bc.ca/pics3/flycut1.jpg

http://vts.bc.ca/pics3/flycut2.jpg

garyphansen
01-31-2008, 11:52 PM
Evan: From what I can see in the photo, the single point tool in your fly cutter does not look like it would produce the nice finish you have. Does the single point tool realy come to a sharp point like it looks in the photo? Gary P. Hansen

rangerod
02-01-2008, 12:05 AM
Evan

The fly cutter is a very nice piece of work. What has been your experience with the use of single point fly cutters? How heavy of a cut would you be willing to take on your mill and what effect do you belive it would have on your spindle? I am just wondering because I used to take some pretty heavy cuts with a fly cutter when I was a very young machinist, never putting mind to what effect it might have on the mill. I used the mill for 8 years with no ill effect that I was aware of. I would appreciate any and all comments. Thanks for the help.

Rod

S_J_H
02-01-2008, 12:19 AM
Very nice job on the cutter. A boring head also works real well as a fly cutter tool holder. It can also be adjusted for balance if need be.

Steve

Evan
02-01-2008, 01:40 AM
The tool is pointy. It has a very small radius lapped on by hand of perhaps .010. However, what you can't see is that it also has a small flat ground on the bottom so that the cutting edge behind the point is nearly parallel with the work for about .040". The sharper the point the better it cuts, especially 7075. It's acting like a razor blade and shaving off the aluminum. 7075 does not machine like the other alloys of aluminum. I used a very slow feed and ran the cutter fast, about 1000 rpm. Thats about 1000 sfm and it could go a lot faster. 7075 produces just about the nicest finish of the Al alloys. 2024 is about as good and not coincidentally almost as strong.

When using a fly cutter on my lathe I would take up to a .100 cut in aluminum and much less in steel or cast iron. The lathe is a different story than the mill though. It has all the mass of the chuck to carry it through an interrupted cut without transmitting the torque pulse back through the drive train suddenly. With the mill I won't be pushing it very far. I will use it as a finishing cut only.

Your Old Dog
02-01-2008, 07:13 AM
Evan, should, or does, the other end of the horizontal piece have a stud to keep it from sliding through should the grup screw fail? My fly cutter is on an angle so it won't likely become a projectile. Just an observation, not to be a safety cop or anything like that.

Evan
02-01-2008, 08:50 AM
That's a good idea. The set screw doesn't just grip though. It is set into a cup drilled in the bar. Still, a fly cutter is definitely an intimidating tool to operate. I always make sure I am out of the plane of rotation when using one on the lathe. That isn't so easy when using it on a mill.

wschoenbeck
02-01-2008, 09:38 AM
Evan, If you happen to have the time would you post a close up or two of the geometry of the cutter bit. I seem to have a diffucult time grinding the bits to get a nice cut when using my angle style fly cutter. A picture being worth a thousand words would go a long way in that regard. I realize the geometry will be different from your 90 degree tool than my angled one. I wouldn't be averse to buiding a fly cutter like yours as well as it looks like a nice one. Many thanks.

Evan
02-01-2008, 10:33 AM
Sure. YOD gave me an idea though so I will post it a bit later.

IOWOLF
02-01-2008, 10:51 AM
Nice Job Evan.

Evan
02-01-2008, 12:48 PM
Here's a pic of the tool geometry. The arrow indicates the cutting direction.

http://vts.bc.ca/pics3/flycut5.jpg

Here is the idea that YOD gave me. My wife gave me a small present the other day, a Valenite ceramic insert that was very old NOS and never likely to sell. I figured if I was going to put something on the end of the bar to prevent it from coming out under power it might as well be useful. All I have to do is to loosen the setscrew and rotate the bar 180 to bring either cutter into play. A ceramic insert is the perfect match for the high SFM that a fly cutter operates at.


http://vts.bc.ca/pics3/flycut4.jpg

BadDog
02-01-2008, 12:49 PM
I like it. As shown, it's much better balanced than most. It also makes for a much simpler bit profile by mounting 90*, and could be used to trepan things (though lacking in fine adjustment).

BadDog
02-01-2008, 12:51 PM
I wouldn't think that ceramic insert would like the interupted cuts typical of a fly cutter.

Evan
02-01-2008, 01:03 PM
I'll find out. :) I only intend, as I said earlier, to use it for fine finishing cuts. It isn't going to be a scale breaker.

I'm pretty sure it is a silicon nitride insert, Valenite grade Q6. According to them:



Specifically recommended for operations ranging from heavy roughing to finishing of cast iron. Suitable for high speeds, heavy feeds, and interrupted cuts.

andy_b
02-01-2008, 01:28 PM
Evan,

nice job (as usual). one question i have is there appears to be a hole parallel to the mounting shaft on the topside of the cutter body. what is that hole for, or was it just something in the piece of scrap you used.

also, you mentioned the set screw that holds the cutter bar in goes into a cup drilled in the bar. does that mean you can only set it at one diameter (until you drill more cups), or am i misinterpreting what you mean? could you post a photo of the individual pieces?

thanks,

andy b.

Evan
02-01-2008, 01:32 PM
That hole was pre-existing in the scrap stainless steel shaft I used. I don't intend to change the position of the bar from the perfectly balanced position it is at. If I need a different length I will make another bar, also balanced. I can't see getting as good a finish with an unbalanced bar.

I'll take it apart later today or this evening. I have to go to town to buy some supplies and will be off line for most of the day.

rotate
02-01-2008, 02:00 PM
Evan,

What's the cost and machineability of 7075 T-6 compare to the 6061? I may be interested in using that for future projects.

7075 may be slightly harder than mild steel, but I was told that alloying any metal does not significantly impact its modulus of elasticity (stiffness), so I'm guessing that you have to choose your application carefully. Your comment would be appreciated.

comerrm
02-01-2008, 04:00 PM
This tool is giving me some ideas. I currently have a John Deere M 2 cylinder engine getting bored over and the crank ground. The machinist doing it for me said the block deck was cupped (concave) about .004 and he cleaned it up. I did not bring the cylinder head to him as I was hoping to do the valve work myself. I was wondering if a heavier version of this tool could be used to deck the head (only 5 thou at the most) on my round-ram bridgeport. Is this a decent way of going about it or should I fork over another $75 to have him do it? Eventually I would like to start doing this kind of work myself, once I aquire some more tooling and maybe a larger machine as I have plenty more 2 cylinders to fix up.
- Robert Comer

lazlo
02-01-2008, 05:27 PM
What's the cost and machineability of 7075 T-6 compare to the 6061?

7075 is about twice the price of 6061. I've machined a bunch of 7075-T651 and Fortal (which is basically the same stuff) and it machines beautifully. It can get a little gummy in the center if you have a thick section.


7075 may be slightly harder than mild steel, but I was told that alloying any metal does not significantly impact its modulus of elasticity (stiffness), so I'm guessing that you have to choose your application carefully.

7075 has 1/3 the stiffness of steel: 10.4 versus 30 x 10^6 psi. It's slightly stiffer than 6061-T6, which is 10.0 x 10^6 psi.

7075 is slightly harder than mild steel: 150 Brinell versus 135 Brinell for 1018. But it's a lot harder than 6061, which is around 95 Brinell.

Evan
02-01-2008, 05:43 PM
To add to what Robert said 7075 and to a lesser degree 2024 have a tendency to grab the tool when drilling. You can get in real trouble if you drill close to final size and then try to run a slightly bigger bit through. It may just decide to seize so tight that the only way to remove it is to cut it out. Other than that machining 7075 is more like a cross between brass and steel with the excellent machinability of hard aluminum alloys thrown in. The grabbiness is due to the copper content and it also has enough silicon to dull HSS bits faster than you would expect. It has no trace of gumminess and cuts exceptionally uniformly and clean with no burrs.

I forgot to say that don't try bending it and it is considered to be unweldable except for some types of spot welding.

piniongear
02-01-2008, 06:04 PM
Very nice job on the cutter. A boring head also works real well as a fly cutter tool holder. It can also be adjusted for balance if need be. Steve
I have a Criterion DBL203D boring head with a set of five 3/4 inch diameter boring bars that I just unpacked last week and have yet to use it.
I bought the head set to bore large holes, but I assume the horizontal hole in the head is used for the fly cutter set up?
How can I balance the set up?
How well will this work and is there anything I should watch out for, except my hand and fingers of course?.......pg :D

topct
02-01-2008, 06:12 PM
Evan, do you know if that is tooling plate?

Evan
02-01-2008, 06:25 PM
It's actually a big chunk of Fortal that I bought from Mousebar before he shut down. That is simply 7075 that has been treated to the top of the 7075 spec. The only difference to tooling plate is that the surface is ground to within a tolerance of .001" or so. This piece was so ground so I guess it qualifies as tooling plate. For that matter, most of the major parts of my mill are made from tooling plate. The local job shop owner sold me a 3/4 sheet of 3/4" 6061 tooling plate for $100. Virtually every scrap of that 3/4 4x8 sheet is in the mill.


How can I balance the set up?

To balance mine I just lay it on it's side. If it doesn't roll then it is close enough.

lazlo
02-01-2008, 06:54 PM
It's actually a big chunk of Fortal that I bought from Mousebar before he shut down.

I still have a big stash of Fortal from then. Some new guy is flooding Ebay with Fortal cutoffs, but they're nearly twice as expensive as the Mousebar days...

Evan
02-01-2008, 07:35 PM
I still have quite a bit too. He was a nice guy to deal with and his prices were extremely fair. I paid $2 per pound for 60 lbs IIRC.

andy_b
02-01-2008, 10:24 PM
This tool is giving me some ideas. I currently have a John Deere M 2 cylinder engine getting bored over and the crank ground. The machinist doing it for me said the block deck was cupped (concave) about .004 and he cleaned it up. I did not bring the cylinder head to him as I was hoping to do the valve work myself. I was wondering if a heavier version of this tool could be used to deck the head (only 5 thou at the most) on my round-ram bridgeport. Is this a decent way of going about it or should I fork over another $75 to have him do it? Eventually I would like to start doing this kind of work myself, once I aquire some more tooling and maybe a larger machine as I have plenty more 2 cylinders to fix up.
- Robert Comer


come on, post pics (in a separate thread if you want)! i have a '54 JD 40 that i rebuilt. there have been photos of it posted here before.


and to get back on topic, Evan, no need to disassemble it. your description answered my questions. now to keep my eyes open for a nice piece of suitable scrap. :)

andy b.

S_J_H
02-02-2008, 11:57 AM
I have a Criterion DBL203D boring head with a set of five 3/4 inch diameter boring bars that I just unpacked last week and have yet to use it.
I bought the head set to bore large holes, but I assume the horizontal hole in the head is used for the fly cutter set up?
How can I balance the set up?

This is an old pic of mine, To balance I just mounted a pointy scribe in a vise and by trial and error made punch marks in the flycutter shaft until I found the point of balance.Then install so that the center set screw in the boring head aligns with the balance point on the cutter shaft. When running the flycutter you can then make slight changes in the offset of the boring head for a real nice running balance if need be.
I have test run this setup at 4200rpm with a 3.25" sweep without vibration.
http://i109.photobucket.com/albums/n48/S_J_H/test024.jpg
Steve

piniongear
02-02-2008, 12:58 PM
Thanks Steve. Appreciate the photo as well. I will have to set mine up and see how out of balance it is........pg

JCHannum
02-02-2008, 01:23 PM
The purpose of the cross hole in the boring head is for boring holes larger than the body of the boring head.

While a boring head can be used for a fly cutter, that is not what I would recommend as the best application. A Criterion boring head is a precision tool, and costly. Fly cutters are easily fabricated, and purchased imported sets are cheap enough that misusing a boring head is unecessary.

piniongear
02-02-2008, 06:07 PM
The purpose of the cross hole in the boring head is for boring holes larger than the body of the boring head.

While a boring head can be used for a fly cutter, that is not what I would recommend as the best application. A Criterion boring head is a precision tool, and costly. Fly cutters are easily fabricated, and purchased imported sets are cheap enough that misusing a boring head is unecessary. Well, boring a larger hole was what I thought the horizontal hole was for. I was surprised to hear it could be used as a fly cutter (surprised that it never occurred to me anyway) and so I asked the question.
Precision indeed, and I would like to keep the $600 plus set that way, so I believe I shall not be using it for facing purposes. Thank you for your comment......pg

S_J_H
02-02-2008, 06:09 PM
JCHannum, maybe if one was using a top quality unit I could go along with you and never said it was the best application and was just tossing out a simple setup. I have several flycutters and I'll be damned if any of them do a better job than the boring head setup. The cheap heads work just fine and I honestly don't see much difference in flycutting vs boring forces on the tool unless you have a large intermittent cut. I have used it for a lot of flycutting. There is no wear and tear on it for such use. But I don't have big machines that might take a heavy cut with a flycutter either.
Steve

Evan
02-02-2008, 06:34 PM
Well, I am making good progress on the engraving table. The fly cutter is doing exactly what it is supposed to do. I picked up some metal yesterday and put some wings on the 7075 plate. The assembly is an exact fit to the mill table such that when taken off and replaced it must go back in the same place. When I add and engrave a right angle fence to the left and back it will be precisely aligned to the axes. Then I need to make some very low profile cam-locks and a bunch of holes to put them in for different sizes of work.

http://vts.bc.ca/pics3/engtable.jpg

lazlo
02-02-2008, 06:52 PM
Nice surface finish Evan. Did you use that Cermet you had?

If you did, I'm surprised it didn't fracture under the interrupted cut on the edges, especially since it's (in your words) very old, New Old Stock.
Modern cermets are supposedly much tougher (I haven't tried any), but the cermets from just a few years ago were so fragile, they were relegated to un-interrupted finishing passes.

Evan
02-02-2008, 06:59 PM
Yes, I used the insert for the final passes. I'm pretty sure it is silicon nitride and it is more like metal than ceramic. The reason I say "pretty sure" is that it was made by Valenite as a special for a machine manufacturer that my wife deals with. It's a spare part and the only numbers on it are proprietary. It even took a skim off one of the cap screws without complaint.

BobWarfield
02-02-2008, 07:18 PM
Somebody on one of the boards (PM or here I think) was saying PCD inserts leave an awesome finish on aluminum, FWIW.

Nice looking table. Will be interesting to see it come together.

Best,

BW

JCHannum
02-02-2008, 07:38 PM
The choice of how to use your tools is entirely up to you. I was merely pointing out that the purpose of the cross hole is not for use as a flycutter.

Zippy
02-02-2008, 07:49 PM
I still have a big stash of Fortal from then. Some new guy is flooding Ebay with Fortal cutoffs, but they're nearly twice as expensive as the Mousebar days...

Mousebar is back but he isn't mousebar anymore. I live about 30 minutes from him and have seen some of his interesting projects. He is on Ebay as zmove. Search for 7075 aluminum and he will come up. The guy who has expensive Fortal is about 20 miles away from him. I see mouse doesn't use the word fortal anymore in his auctions. I wonder if they are in it together?

JRouche
02-02-2008, 10:12 PM
Nice surface finish Evan. Did you use that Cermet you had?

If you did, I'm surprised it didn't fracture under the interrupted cut on the edges, especially since it's (in your words) very old, New Old Stock.
Modern cermets are supposedly much tougher (I haven't tried any), but the cermets from just a few years ago were so fragile, they were relegated to un-interrupted finishing passes.

I have and use a fair amount of ceramic inserts. Only used them for turning and on some hard shafts. Shafts with keyways and I dont have any problem with interrupted cuts. I do spin it very fast, I think Im burning through more than anything. Sparks and all. Not that I know anything Im doing is right, just seems to work. JRouche