Ornamental Turning Book of Knowledge
Cutting Frame

Horizontal Cutting Frame


Universal Cutting Frame
Images courtesy Bill Ooms

The cutting frame is similar to a circular saw in the way it works. It has a spinning cutter which is engaged with the wood to cut into it.

For use, it is held in a quick change tool post (QCTP), and the QCTP bolted to an cross slide (much like a metal lathe's tooling is held in the compound rest).

There are a number varieties of cutting frames, but the first 4 are the most used today :

  1. horizontal cutting frames (HCF) - where the cutting head spins horizontally along a vertical axis. This is the one which is shown in the upper picture on the right.

    If you wish to make your own HCF, Bill Ooms has provided great directions. Additional notes from my own experiences making an HCF are on this page.

    The video below shows an HCF in use.


  2. vertical cutting frames (VCF) - where the cutting head spins vertically along a horizontal axis.

    If you wish to make your own VCF, Bill Ooms has provided great directions.


  3. universal cutting frames (UCF) - where the cutting head can be rotated up to left or right, making the cutting head spin along an axis determined by the ornamental turner. This is the one which is shown in the lower picture on the right.

    In the pictures of the horizontal and universal cutting frames to the right, the brass part at the end of the arms is the cutter head. The pointed part in the cutter head is the cutter.


  4. internal cutting frames (ICF) - which are basically drilling frames that hold a cutter perpendicular to the axis of rotation. These are particularly useful for cutting the inside of cylinders and egg-shaped objects.

    Cutters for ICFs take various shapes, and some examples from Holtzapffel's Turning and Mechanical Manipulation, vol. 5 - The Principles and Practice of Ornamental or Complex Turning are shown below.

    Figures 177-184 - Turning and Mechanical Manipulation,
    vol. 5 - The Principles and Practice of Ornamental or Complex Turning
    (1884)

  5. eccentric cutting frames (ECF) - a variation of the fly cutter, but the cutter's body is held in a drilling frame.

  6. elliptical cutting frames - another variation of the fly cutter.

  7. epicycloidal cutting frames - another variation of the fly cutter that is basically the merger of a eccentric cutting frame and a geometric chuck.

  8. rose cutting frames - really interesting fly cutter where the cutter's holder rides along a rosette for it's movement (whilst also spinning).


Key Note : Cutting Frames are where the quality of ornamental cutting comes to life. If there is vibration in the cutting frame it will be transmitted to the cuts, and the quality of the work will be poor.

When you are using the ornamental lathe, listen for noise in the cutting frame.

  • The cutting frame should have a whir like a finely tuned machine, and the noise level should be low.
  • If there is vibration, the noise level will be higher. Sometimes much higher. And the tone of the noise will be higher. It won't sound or run like a finely tuned machine.

Cutters

There are two types of cutters :


  • Carbide Cutter
    Image courtesy
    Bill Ooms
    Carbide cutters - these are triangular pieces of carbide held by a screw in the brass cutter head. An example is shown in the picture to the right.

    Advantages of using carbide cutters are :

    1. There are two on the wheel, making the cutting action happen twice as fast.
    2. The carbide cutters stay sharper longer.
    3. The carbide cutters can be easily replaced when they become dull.

    The insert recommended is from Circle Machine Co., part number is 2828732 (the industry number for them is TDAB-505-C25). It is grade C25 carbide, and has a 0.007 inch corner radius. This radius is recommended over those cutters with 0.002 inch radii (or smaller).

    A larger corner radius "blurs" the definition, and that may be what you want as an artist. However, a corner radius smaller than 0.007 inch will not necessarily give better definition. Those will amplify each and every striation in your cuts, making them look like someone dragged a rake over your workpiece.



  • Fly Cutter
    Image courtesy
    Bill Ooms
    Fly cutters - these are sharpened rods put into a holder which spins it around. In the picture to the right, the fly cutter is the sharpened piece of steel held into place in the brass cutter head.

    Advantages of using fly cutters are :

    1. The holder of the cutter can be easily made on a bench top metal lathe; no milling machine is needed.
    2. The fly cutters can be resharpened by the home ornamental turner (sharpening instructions for fly cutters are on my Sharpening Handbook web site).
    3. The fly cutters can be ground to different shapes than simply a triangular bit. This is of particular note as I have found that rounding over the end (vs. taking it to a point) makes the results better for softer woods (e.g., cherry) and woods with wider grain patters (e.g., ash).

    Traditionally, fly cutters were flat pieces of metal with various shapes, and there are some ornamental turners who use these still today. Many of these are used with vertical cutting frames, but they work on other cutting frames : It just really mattes what the turner is trying to achieve.

    Some examples are shown below.

    The smaller cutters shown above would be used in internal, eccentric, elliptical, and epicycloidal cutting frames, whilst the larger would be used in vertical, horizontal, and universal cutting frames. (There much more information about these, and pictures, in Holtzapffel's Turning and Mechanical Manipulation, vol. 5 - The Principles and Practice of Ornamental or Complex Turning.)

    Below is a YouTube video showing a fly cutter in use :


    Fly Cutter for a Rose Engine Ornamental Lathe

    Eddie Bell gave a presentation about variations on the Eddie Gorst finials at the 2018 Ornamental Turners International Symposium. This is a nice presentation about the effect fly cutter shapes can have on the object shape.


Slitting Saw

At the 2018 Ornamental Turners International Symposium, Steve White introduced the idea of using slitting saws in a cutting frame. These are the same saws that get used in milling machines for cutting slits in an object.

Steve's use of this was to cut a slit of a certain size (say, 1/16 inch) along the Z axis in an object at various locations (e.g., every 90° around the circumference), and then insert a piece of contrasting wood into the slit. This is different from segments glued together with thin contrasting woods. In this case, the slits did not traverse the entire length of the piece, only a part of it. (I realize a picture would be great, and I'm working on getting one.) It is a great way to produce a uniformity and beauty that couldn't be easily done via other methods.


Jon Magill authored an article titled, "The Cutting Edge of OT" that has more pictures and details. That article was published in the AAW's magazine, "American Woodturner" in Spring 2008, pages 32-35.

The cutting head is traditionally rotated using an overhead drive, but direct drive approaches are also used.

Cutting frames can be purchased from a number of vendors (see also, Buying a Rose Engine Lathe), or you can make your own. Directions for making a cutting frame are nicely described by Bill Ooms. There are additional notes about this at making a Cutting Frame.

If you make your own, you will need belting for it (that is the orange stuff in the universal cutting frame picture, above). I used the same cable belting for this as I used on my overhead drive.


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Disclaimer : eMail comments to me at OTBookOfKnowledge @ Gmail.com. The process of woodturning involves the use of tools, machinery and materials which could cause injury or be a health hazard unless proper precautions are taken, including the wearing of appropriate protective equipment.