Powermatic Millrite MVM Milling Machine
|List of All Documented Equipment|
|Hive13 Asset Tag: HV0053|
|Make/Model: Powermatic Millrite MVM (google)|
|Arrival Date: 11/2019|
|Does it work?: Yes|
|Certification Needed?: Yes|
|Contact: CNC Warden|
This particular "Millrite" is what is known as a 'knee-and-column, turret-type' vertical milling machine.
It is a manual machine. It has sufficient weight, power, and rigidity to perform a wide-range of general-purpose metal-cutting (milling and drilling) operations. Vertical mills of this type have been ubiquitous in job shops for the past century.
In the capable hands of a knowledgeable user, a sequence of specific harder-metal rotating tools can be safely brought into controlled interference contact with a softer metal workpiece. The resulting cutting action produces metal chips and finished parts. The action is similar to wood-cutting machines that produce sawdust, but the metal-cutting forces are much higher and less forgiving. A sequence of subtractive milling operations transforms the original workpiece stock to create specific round and flat surface features to precise tolerances. Dimensional tolerances measured in single-digit thousandths of an inch (+/-.001") can be repeatedly produced.
In the inexperienced hands of a neophyte user, such a mill is highly dangerous. An unsafe milling process can quickly result in serious personal injury and catastrophic damage to the machine.
Learning to use such machines has traditionally been a multi-year, on-the-job, experience-based process. Individuals went through a lengthy 'apprentice' period and then spent their entire career working on a single machine to develop the knowledge-base and 'feel" for this highly-skilled trade craft and become a 'machinist' or a 'tool-and-die maker'. There are many ways to be inattentive, careless, do it wrong, and get into trouble. It is a constant challenge to be attentive, diligent, do it right, and stay safe.
History of this machine
This particular Millrite MVM was made in Cincinnati in 1971, in the Oakley neighborhood, on Brotherton Avenue, at a company that was founded in 1915. Member JimD bought the machine from as small job shop in upstate New York in 1980. It has been in his home shop for the past 39 years. In 2019, JimD put this machine on indefinite consignment to Hive13 for gentle use by considerate members.
Further information on the history of the company and the Millrite product line can be found on this page https://wiki.hive13.org/view/Powermatic_Millrite_MVM/History
We do Mill and Lathe certification on an as needed basis. Email the warden to request certification. Only the following people are permitted to certify you on the mill:
Certification Goals – Don’t hurt yourself. Don’t hurt the machine.
- Mill safety and setup
- Tool selection for milling operations
- Holding parts using the machinist vice and parallels
- Change tools and set spindle speeds
- “Zero” the X, Y and Z axis using the DRO
- Perform basic facing cuts on steel
- Mount and secure work using parallels and hold downs
- Demonstrate understanding of Backlash
In preparation for certification please; Read the manufacturers manual and study the excellent materials from Case Western
Take the milling quiz.
https://www.proprofs.com/quiz-school/story.php?title=mill-quiz When you have a score of 100% print out the certificate and contact the CNC warden for your certification check ride.
Current Status (2019-11-11)
The mill is re-assembled and connected to power, available for limited initial use by members that are certified to use this tool. JimD has consigned a starter kit of tooling for use with the mill. JimD is also working on a 'Good2Go Mon' badge-activated power box for this machine and other certified-user machines at the Hive. You are encouraged to use the machine, but are cautioned to be SAFE for your sake, and for the sake of the machine. Things can get out-of-hand quickly if you do not know what you are doing.
Please contact Jim at firstname.lastname@example.org and/or cell 513.300.5164 to share your questions and plans for use of this mill.
Related Tooling (2019-11-11)
Traditionally, tooling is sub-divided into two categories; 'Durable' tooling and 'Perishable' tooling.
- Durable tooling can include a wide assortment of work-holding devices such as vices, parallel bars, step blocks, clamp sets, and other fixturing that can be general-purpose, or part specific. The re-usable parts of cutting tools (collets, end-mill holders, drill chucks, and such) are also considered to be durable tooling. Metrology items such as dial indicators can also be considered as durable tooling.
- Perishable tooling includes all the different consumable items such as end mills, drills, cutters, and inserts. The Hive owns a variety of high speed steel end mills which were purchased used on eBay. You are welcome to use these. They are in a box under the Enco mill labeled 'Good enough'. If you damage one, report it to broken (at) hive13 dot org.
The number of items in a resulting kit of durable and perishable tooling can grow quite large and be very expensive, often growing to exceed the cost of the machine itself. While JimD has consigned a starter set of tooling, the Hive may consider to vote to procure additional tooling if there is sufficient group interest. You should consider to procure your own perishable tooling, particularly if you have special, or high volume needs.
There are many considerations in selecting the proper tooling for a given part and cut.
- For the workpiece fixturing, RIGIDITY is the primary consideration. The part must be held VERY SECURELY to avoid deflection and vibrations from the cutting forces that can be heavy. An associated consideration is clearance for the range of motion of the cutter.
- For the durable tooling, RIGIDITY and clearance considerations remain of primary importance. Rigidity typically means short and stubby tool holders for stiffness and vibration resistance purposes.
- For the perishable tooling, RIGIDITY and clearance are still primary considerations, but there are many added factors to consider. Selecting even a 'simple' end mill requires proper consideration of multiple factors based on the desired cut. These factors include tool material (typically carbide, or high-speed steel); tool coatings (such as TiN); tool diameter; tool length; flute length; number of flutes (typically two flutes (center cutting) or four flutes (NOT center cutting); and corner radius.
Even with selection of the proper workpiece fixturing, tool holder, and cutter, there are additional milling process decisions to make. These decisions include choice of climb or conventional milling, axial depth of cut, radial depth of cut, chip load per tooth, and related tool RPM and feedrate. It is very easy to apply forces that can break steel tools at the shank. Such incidents over-stress the machine structures, lead screws, and spindle bearings. Flying pieces of loose tool steel can be a personal hazard.
There are many web resources to learn about tooling. This brief [YouTube Video on avoiding chatter] is a good start.
The principal elements of the Millrite are detailed in the following:
- Spindle Drive Motor
- Spindle Speed Range (via belt and step pulleys)
- Knee (Z-Axis)
- Saddle (Y-Axis)
- Table (X-Axis)
- Column and Base
- Change Spindle Speed (via belt and step pulleys)
- Change Tool in R8 Spindle
- Dry-run cut before actual cut
- Clean-up when done (leave it better than you found it)
- After each use (each certified member user)
- Once-per-month (clean the Hive Saturdays)
- Once-per-year (JimD and/or area warden)
- Way Oil (Vactra #2)-- 
Sites to buy from for cheap
Manuals & Guides
- Overview of the Millrite line of machines
- User Group for Burke Mill Owners
- Vintage Machinery Website History of the Burke Machine Tool Company
- "Traming" a mill drill
- (PDF Link) Interesting book on how to use a milling machine
- The Machinists Handbook
- A Treatise on Milling and Milling Machines (pub 1919)
- Archive.org search for Milling Machine books