Small face mill using tangential cutter

Homebrewed:
After reading and re-reading your article, I am more convinced this simple tool can be built to suite the requirements of most Mini-Mills. Specifically the LMS 3960 or similar units. a single R8 Arbor can be used to hold different sized versions of this cutter.
The unique properties I envision is that of a small "Fleet" of Fly Wheel based cutters using the tool bit of choice in a Fly-Wheel of sorts to provide the diameter of the cut required. One Arbor forms the basis for the tool and different diameter Fly-Wheels using the available tool bit. This reduces the storage issues as only the Fly-Wheels of the differing Diameters are required to be stored.
As you have already stated the sharpening is simple and one Tool Bit can be used in all the differing sizes of the Fly-Wheels.
Many of us have our Work Shops like Harry Potter under the stairs or some other impossibly small location so any and all space is at a premium.
I have even given thoughts to a single large Fly-Wheel with the appropriate holes drilled according the the required radius of the cut required. The holes would have to be spaced about the Fly-Wheel so as not to weaken the structure or upset the balance of the Fly-Wheel.
Note: The Fly-Wheel now has to be designed as an integral part of the spinning cutter.
Home-brewed, you have spawned a monster that may go viral. ha ha
Again Thanks for Listening
 
courierdog said:
Homebrewed:
After reading and re-reading your article, I am more convinced this simple tool can be built to suite the requirements of most Mini-Mills. Specifically the LMS 3960 or similar units. a single R8 Arbor can be used to hold different sized versions of this cutter.
The unique properties I envision is that of a small "Fleet" of Fly Wheel based cutters using the tool bit of choice in a Fly-Wheel of sorts to provide the diameter of the cut required. One Arbor forms the basis for the tool and different diameter Fly-Wheels using the available tool bit. This reduces the storage issues as only the Fly-Wheels of the differing Diameters are required to be stored.
As you have already stated the sharpening is simple and one Tool Bit can be used in all the differing sizes of the Fly-Wheels.
Many of us have our Work Shops like Harry Potter under the stairs or some other impossibly small location so any and all space is at a premium.
I have even given thoughts to a single large Fly-Wheel with the appropriate holes drilled according the the required radius of the cut required. The holes would have to be spaced about the Fly-Wheel so as not to weaken the structure or upset the balance of the Fly-Wheel.
Note: The Fly-Wheel now has to be designed as an integral part of the spinning cutter.
Home-brewed, you have spawned a monster that may go viral. ha ha
Again Thanks for Listening
Click to expand...
There are worse monsters out there :) Anyway, you're the one taking the ball further downfield, so I say Go For It!!

In my mind, the main issue right now is to figure out why the cutter with a larger included angle (smaller grind angle) doesn't work as well. A larger included angle should produce a more robust cutter. I suspect the optimal cutter orientation is not exactly tangential to the swept-out circle; or perhaps there is a subtle relationship between the amount of stick-out and the cutter orientation needed to get the best cutting action.
 
homebrewed said:
There are worse monsters out there :) Anyway, you're the one taking the ball further downfield, so I say Go For It!!

In my mind, the main issue right now is to figure out why the cutter with a larger included angle (smaller grind angle) doesn't work as well. A larger included angle should produce a more robust cutter. I suspect the optimal cutter orientation is not exactly tangential to the swept-out circle; or perhaps there is a subtle relationship between the amount of stick-out and the cutter orientation needed to get the best cutting action.
Click to expand...
Homebrewed:
I am the middle of rebuilding my shop and until it is completed, I am restricted to research, this is when I stumbled across your article.
now I am on the look out for an R8 arbor, that fits the LMS 3960 which uses the 7/16 x 20 threaded arbor. My first thought is to find an arbor on eBay or Amazon. I have found some wonderful ones which come with a Face Mill attached. I am trying to avoid them as I will learn more by using you concept and building the actual cutter. My tooling consists of 1/4 inch Square and Round HSS and Carbloy. I have some simple projects in mind. While I have some end mill which came with the Mill I really like the concept of the single facet Face Mill which can be employed to make the simple Cuts I have in mind.
None of my projects large, as my tooling are Table Top machines this suits my current dreams. Finding the concept of a single facet Face Mill like yours just opens another window of learning which can be done using my existing machines with tooling built in my shop.
My first new tool will have to be an appropriate R8 Arbor to which my plans are to affix various sizes of Face Mill (Fly-Wheel tool holder or the other idea I have running around my head of a single Fly-Wheel with multiple positions into which the tool bit will be slid into and the appropriate screw(s) tightened to hold in place.
Optimized single Tool Holder vs a single tool holder with multiple tool positions.
First the Arbor
Then a first pass at the tool holder
After that multiple versions of different Radius.
Then we try it out as a Single Facet End Mill, ha ha
Any suggestions
T f L
 
A single head with multiple cutter positions sounds interesting. I've already run into a couple situations where my little tool was just a bit too small.
 
homebrewed said:
I recently made a small face mill that uses a 3/16" diameter HSS rod for the cutter. The idea was to replace an indexable face mill with something that would handle interrupted cuts better (I always seem to chip the inserts). I like the concept of the tangential cutter because they're dead easy to sharpen. To simplify some of the machining steps I made the face mill in two parts -- the arbor and the holder for the cutter. I started with a 3/4" rod of HRS for the arbor and some 1.25" diameter 4140 for the holder. The photos below show a few steps in the process of making it, after I did the initial lathe work to turn the 3/4" rod down to 11/16" to fit my R8 collet and smoothed/faced the holder down to a .486" thick disk (there was no specific thickness target, it just ended up that thick).

This photo shows the holder in my angle vise. The vise is set to 12 degrees from horizontal, and I'm milling a flat preliiminary to drilling the 3/16" hole for my HSS rod.
The slot (machined in a previous step) is .1" deep and .5" wide, and matches a tang milled on the end of my arbor. With this approach the bolt that joins the two pieces doesn't have to resist the torque produced by the cutter when it's removing metal....and I can make different-sized holders as needed. To make it easy to accurately rotate the holder 90 degrees, before breaking down the previous setup I also milled two flats on the side of the holder. That gave me a nice secondary reference plane.
View attachment 313586

The photo below shows the holder and arbor assembled to make sure they fit OK. This photo actually predates the first one shown above. My old drafting ruler is there to provide a sense of scale. I was able to machine the slot and tang accurately enough to get a friction fit. 'Course, if I hadn't done so well I wouldn't have mentioned it :rolleyes:.
View attachment 313588

Below shows the finished product, complete with a shortened hunk of HSS that's been ground to 30 degrees on the end. I wrote a spreadsheet to calculate the offset necessary to place the tip of the cutter so it is exactly tangential to the circle swept out by the tool, when the cutter is projecting .1" below the bottom face of the holder. I also used the same spreadsheet to determine where I needed to drill/tap the hole for the set screw.
After grinding the HSS I did notice a small burr on the end so I honed it with a 600 grit diamond file. That produced an edge that would easily shave my fingernail.
View attachment 313589

Below shows the result when I tried my face mill on a piece of 6061. I also tried it on some HRS with a .01" depth, full .75" wide cut and it worked just fine. No chatter, nice smooth surface. This was done on my Sieg SX2 mini mill, not the most powerful beast around, so I call it a success.
I was concerned that the cutting forces would push the cutter into the holder but that wasn't a problem. Not so far, anyway....
View attachment 313590
Click to expand...
Nice job and nice surface finish
 
homebrewed:
I for get where I read where someone actually made a non adjustable cutter, but made provision for more than one tool bit giving the ability to have different radius settings.
With a Fly-Wheel based holder and the simple hole drilled at the desired radius, place different positions around the wheel.
In your example it is a simple hole drilled at 12 degrees. A Fly-Wheel of 3 inches by a nominal 1/2 to 3/4 inch thick will provide sufficient mass. It should be possible to have 4 possible 6 different positions for the desired cutting radius.
Now comes the tricky part. How and where to place the holes. Keeping in mind this Fly-Wheel is a dynamic tool and a simple static balance will be extremely deceptive.. I think it will be an interesting experiment. The results may be insanely brilliant or we may have to consider comment the designer to an institution. ha ha
I found an insanely inexpensive 4 Facet Face / End Mill from China. Delivered is less than $50CDN so I broke down and ordered it.
I have also read that there are several grades of inserts and there are inserts tailored for the cutting of specific material.
Back to our topic of Home Made Tooling.
I like the simple tooling concept as it uses simple everyday cutting material such as HSS or Crobalt which are both easily sharpened on the bench grinder.
I have found that the Tangential style cutter does not seem to suffer like other tooling when it runs into an unknown spot like a weld which can be exceptionally hard. I found while insert tooling will sometimes shatter when it runs into a weld the Tangential tool virtually laughs it off.
I am really hoping your concept will allow me to use the Mill in such a way so I can use my favourite type of current for simple edge removal and such where I normally have to use an end mill to cut away a simple side notch in a surface.
Yours is one of those articles which has my brain running several different ways at the same time thinking of new or at least different ways to construct or use this concept.
Thank You Ever So Much for providing the stimulus for me to get up and finish the shop to move onto more interesting tool concepts.
Your simple and practical approach is what makes this hobby worth while.
Stay Safe, Stay Well
Dave C
 
the next chapter
I am currently working on the computer to design a Flywheel style Fly-Cutter.
I have two objectives
1. to produce flat smooth surface
2. to produce a precise corner for a step
While not totally exclusive the cutter face to achieve either case may require a different approach.
Typically a smooth surface requires a wide radius of the cutting edge while the sharp edge is a corner requires a sharp defined edge tooth cutter.
The simplest approach is a round tool bit for the smooth surface running at a tangential angle to the cutting surface see the concept from https://www.hobby-machinist.com/threads/small-face-mill-using-tangential-cutter.82442/
The Sharp corner I would think would start from square stock tool bit this approach is most easily achieved using any of the conventional Fly-Cutter designs
My current challenge is to design one Disc or Flywheel which can hold either a round or square tool bit.
The basic concept must comply to the above article as it can be accomplished by most people
A square can hold either a Round or Square Tool bit stock.
While a simple 12 degree (facing the direction of the turn) drilled hole can accomplish the concept mentioned above.
The same approach using a square clamp would require the Flywheel to be cut at the desired radius and a 12 degree angled v cut into each side of the flywheel. When mated back together the two pieces would form the clamping square for either a round or square tool bit stock. The design concept is to turn the clamping square such that the tool bit is a tangential cutter capable of providing a square corner in any material it cuts on the edge.
It will also be quite capable of producing a good finish on both the vertical wall and the floor of the cut.
It will take some time mostly in coming up with the working angles as in this design once cut the angle is fixed and the design concept should be capable of using the standard Tangential Tool bit which in a lathe use a 12 degree by 12 degree cutting angle.
The typical grind is a nominal 30 degree. This provides a very strong and long lasting cutting surface and easily resharpened when the cutting edge requires resharpening. The other advantage to this concept is returning to the same cutting depth is a simple matter of adjusting the too protrusion from the Tool holder (Flywheel)
OK this is a very long winded explanation of the concept to bring the tangential Lathe tool approach to the Milling Platform.
The problem with the Mill is rotating the tool and we do not need any additional flying objects seeking more human blood to feed upon. More design work is required to minimize additional protrusions other than the cutting surface.
The thickness of the flywheel is to hide all or most of the tool bit and provide the nominally balanced flywheel
The diameter of the flywheel is to provide the designed radius.

IF there is anyone who can add to this concept you are more than welcome to add your comments as all ideas are welcome, as this is a hobby where we can share our ideas both good and not so good.

I wish I could draw what is in my head for the design concept then it would be much more clear for everyone to see and add their two cents to improve it for everyone else.

Thanks for Listening
 
I've been thinking more about the problem I encountered when I tried a cutter with a larger included angle (a shallower grind on the end). I think it may be related to what the workpiece "sees" as it's being machined.

When you cut or grind a cylinder at an angle, the profile is an ellipse-like form. A belt grinder would produce a true ellipse because it removes material on a single plane, whereas a grinding wheel removes a shallow arc so the profile isn't **exactly** elliptical, but it's close enough.

It also turns out that the projection of an ellipse onto a plane (i.e., the cutter's presentation to the work) also is an ellipse. As the ellipse becomes more and more co-planar to the plane of the work, the projection of the ellipse onto that plane flattens out. In the limit where the ellipse is exactly parallel to the plane, it is a straight line. This is a horrible profile for a cutter.

It should be noted that the 12 degree tilt angle will also, in effect, flatten out the ellipse. For instance, the second grind angle I tried was 17 degrees. In combination with the 12 degrees from vertical, the end result is a very "flat" ellipse, tilted just 5 degrees relative to the work.

This variation in geometry has a bearing on my cutter's performance. If the DOC is greater than one half the effective "height" of the projected ellipse, the width of the area being cut goes across the entire width of the cutter. I think you'd see a problem before that because at some point there's not enough "lift", if you will, of the material to break it free of the work (when it then becomes swarf). So you'd get a nasty raised edge all along the cut path.

Based on the relatively good results obtained with a 30 degree grind angle, there must be a sweet spot for cutter included angle vs. the maximum DOC it handle---and that should also depend on what material you're cutting. Tough stuff like plastics, which will deform more before they break, will likely be the pickiest, followed by aluminum, various grades of steel and (probably) brass will be least problematic. Would Young's Modulus be a measure of a particular material's "pickiness"??

Rotating the cutter so it can shear off the raised edge left by a previous pass may be a way to fine-tune the cutting action. If the raised edge is allowed to rub against the top of the cutter, that's when the cutter will struggle and produce a poor surface finish.

My mill currently is down but hopefully it will back in operation soon so I can test some of these hypotheses. It won't be possible to vary the vertical angle with my current design but it wouldn't be too difficult to come up with something that could do that. Basically a variation on a trepanning tool.
 
A quick calculation regarding the ellipse "height" on my 3/16" HSS rod, when ground at 17 degrees, found that a DOC equal to or greater than about .008 inch would encompass the entire width of the cutter. I think this pretty much explains why that grind angle produced such a poor result.

The calculation was very straightforward. If A is the effective angle of the ground facet relative to the work and H is the height of the heel of the facet relative to the tip, H = D*tan(A)/2, where D is the diameter of the rod. Why the division by two? Because the halfway point marks the maximum width of the ellipse.

If the vertical angle is reduced to 8 degrees the DOC increases to about .020 inch. This is not an exact calculation because the effective "width" of the cutter is slightly larger due to the tilt angle. It's a bit on the optimistic side, but isn't too inaccurate for small deviations from the vertical.

I chose 8 degrees as an example because that is a commonly used angle when grinding lathe cutting tools, there's nothing magic about it.

BTW, my calculations do NOT say that you could actually obtain good results with the 17-degree angled cutter with, say, a .005" DOC -- as I indicated in my previous post, there has to be enough lifting action to break the cut portion loose. But they would be a starting point.
 
Homebrewed: In my case my grinders happen to be 10 inch wheels which produce far less eclipse than the standard bench 6 inch grinder wheel.
Regardless I believe you are onto something. And this is another reason I have invested in the Acute Tool Sharpening Kit. My firm belief is the simpler Diamond style tool bit is easier to use by the average amateur machinist. The key here is keeping the Tool bit simple and thus simpler to sharpen. In the case of the Tangential or Diamond shaped tool bit a simple single surface can be sharpened by the beginner and achieve amazing results.
My current objective to take your concept to the next level.
My current line of thinking is the make the Flywheel with a split clamp and turned concentric. Instead of the Drilled Hole my initial idea is to mill a two part square instead of the drilled hole. This will permit the use of Round or Square stock as the tool bit.
The two part Square clamp will have to take into consideration the Cutting Angle of a Tangential tool bit that can be of square stock. The Rotational Angle can be adjusted to conform to a Tangential cutter regardless if the Tool Stock is Round or Square.
This allows the Cutter to match the requirements of the finish or cut required.
This is as far as I have gotten so far.
Calculating the angles and cuts required will involve more of a 3D approach which I do not have the program app to design with.
 
You must log in or register to reply here.
Back
Top