Journal of the Home Metal Shop Club of
Houston, Texas
See back page for meeting information.
President - John Korman, V. Pres.- Bill Sperry, Treasurer - Alan
May
Secretary - J.D. Wise, Editor - George Carlson , Email
geotek@wt.net
Membership is open to all those interested in machining metal and tinkering with machines. The purpose of the club is to provide a forum for the exchanging of ideas and information. This includes, to a large degree, education in the art of machine tools and practices. There is a severe shortage of written information that a beginning hobbyist can use. This makes an organization such as this even more important. For membership information and forms, call John Korman at (713) 723-8597.
First, I'd like to thank Bill Sperry for organizing and scheduling programs for the next 6 months. These programs are what the members requested.Second, a thanks to the members who volunteered to present programs. They are: Doug Blodget, Tom Moore, Bill Swann, George Carlson, and Mark Van Scoter. This is what it's all about; members giving back to others what they have learned. More participating and sharing makes for a stronger club.
One of the problems beginners have when they get a new mill is learning about what accessories are needed and how they are used. This article is meant to be an introduction to the use of a vertical mill and what tooling the beginner should start out with. Information herein is based on my experiences as a self taught machinist, and advise I’ve received from the many talented Job-Shop machinists I have worked with over the past 25 years.
Work Holding
The primary piece of tooling every mill ought to have is a good milling vise. The vise of choice today is the "Kurt" type. Import vices purchased from local dealers such as Rutland and J&L are good deals. On sale, 6" versions of these vises, with a swivel base, can be found for less than $200. Since they weigh-in at near 100 pounds, buying one locally is a good idea. If you do have a problem, it is much easier to carry it back to the supplier, rather than paying freight.
Another handy item is a Clamping Kit. This is an assortment of "T" nuts, Studs, Nuts, Step Blocks, and Step Clamps. An import clamping kit in Bridgeport size runs less than $60. Be sure to measure the "T" slot in your milling table before buying the kit. Most Mill Drills can use the Bridgeport size, but the "T" nuts must be ground a little thinner to get them to slide in the slots.
Measurement Tools
As for any other metal working operation, Calipers and Micrometers are indispensable. For the Mill, you should also have two or three dial indicators with at least 1" travel. These can be used for precise movements on the X or Y, and precise depth control. See the December 1996 issue of the newsletter for more information. Another device, that is very useful for center indicating and setting the vise true, is the test indicator. Again, see the December 1996 newsletter for details.
Edge finders are used to quickly find the edge of the work-piece. I use an edge finder with a diameter of .200". The shank is .375" in diameter and can be held in a chuck or collet.
Chucks and Collets
The ideal situation is to have three drill chucks. One very small chuck, 0 to 0.187", for fine work. A high precision chuck from 0 to 3/8" for general work. And a large, maybe 1/8" to 5/8", for the bigger work. Good chucks use a Jacobs taper on the back of the chuck. This is used with an adapter for conversion to a straight shank, Morse taper, or R8 taper. On my small chucks I use a ½" straight shank. I cut the shank off so that it sticks out of the chuck only about 3/4". The chuck is then used with a collet. The reason for shortening the arbor is to make the chuck easier to use if the spindle is close to the work. This is very important for those of you who have mill drills. It prevents having to move the head when switching between drilling and milling operations. For Bridgeport users it means less back pain from cranking the knee up and down. I use an R8 taper on the big chuck. This provides the high torque grip required for heavy drilling.
I use collets for holding end-mills. There is quite a bit of controversy on this matter. The problem has been with end-mills being "pulled" from the collet because of the lift forces of the flutes of the end-mill. This can cause you to damage the work-piece, vise, end-mill, table, or all of the above. I have found that if you use a good quality collet, and tighten it properly, you will not have a problem. This allows you to keep the head closer to the work, and speeds up tool changing quite a bit. Buy high quality collets (the $15 ones) in the following sizes: 3/16", 1/4", 3/8", 1/2", 5/8", and 3/4". These are thew sizes used by standard end-mills. The 1/4" size is not used by end-mills, but is used by other tools such as counter sinks (which may be used to mill decorative chamfers).
Collets can also be used to hold drill bits. The drill bit should be within 1/64" of the collet you plan to use. A set of R8 collets from 1/16" through 7/8" by 32nds would make the drill chuck just about obsolete. Remember, for drilling and such, cheaper collets are fine, use high quality collets for milling. Never use a drill chuck to hold an end-mill. The shank on an end-mill is very hard (unlike a drill bit) and can damage the drill chuck
Cutting Tools
For machine operations done in thew lathe on mill, screw-machine length drill bits are generally preferred. They are much stiffer than jobbers-length which makes hole location more accurate. It also helps to reduce the distance from the spindle nose to work. A point valuable to those using a mill-drill.
For aluminum, the polished flute drills work best, followed by the TiN coated bits. For steel, cobalt bits will outlast HSS, but they can sometimes be more brittle. Don’t waste money on cheap drill bits. Generally the USA brands or name brand imports are worth the extra money. This is true of cutting tools in general.
Reamers are used to finish precision holes. First the hole is drilled a undersize using a drill bit, then the reamer is used to remove the last .003 to .016" of material. Chucking reamers are most useful for use in the mill.
End-mills come in single and double ended, two or four flute, and center cutting on not center cutting. For aluminum, and milling slots in steel, use a two flute end-mill. I don’t think there is any advantage to a non-center cutting end-mill except cost. For general milling of steel, and finish cuts on aluminum, four flute end-mills are best. Two flute end-mills are generally center cutting, this means that they can be plunged into the work. Four flute end-mills can be purchased either way. For starting out, I recommend buying a set of import end-mills. Then as those end-mills are used up, replace them with high quality USA or name brand import. Travers Tool (1-800-221-0270) sells a 20 piece set of end-mills that have the range from 3/16" to 3/4" in both two and four flute versions for only about $60. I think Enco and some of the other suppliers have similar deals. This will allow you to experiment with different milling configurations without endangering high-dollar cutting tools.
Ball-nose end-mills are also available, buy these as requirements arise. The same can be said the Woodruff keyway cutters. Buy them as you run across the need.
Special Tooling
Fly cutters can be used to mill large areas very flat. Make sure your mill is "Trammed-In" properly. The fly cutters will really show-off a mill where the spindle is not dead-on perpendicular to the table.
With a boring head you can make any size hole (within the confines of the boring head and cutter) you desire. Boring heads can also be used to trepan (fly cut) large holes in panels. To do this you must sharpen the cutter in a special way, but it is not difficult. For most machines, a 2" head is a good place to start. The head has holes that are used to hold special boring bars. A 2" head usually uses 1/2" boring bars. The boring bars can also be used in the lathe for boring operations. A 2" import boring head with shank and a set of boring bars can be found for just over $100.
To cut slots you can use saw-blade type cutters in the mill. There are two basic types: Jewelers saws, which use a small diameter arbor and have fine teeth, and Slitting saws that have course teeth and larger diameters. A 1/2" arbor with a straight shank is a good size for the Jewelers type. For slitting saws try the variable size type with an R8 shank. Watch your speed when using saws. A 4" blade has a one foot circumference, so it shouldn’t be run any faster than about 50RPM for steel. Also use some sort of coolant.
Just a Start
I hope this little article has helped you sort out what tooling you may need for your new machine. Much of your needs will be defined by the type of work you plan to do. Tooling a lathe or mill is an ongoing process. I’ve been tooling my milling machine for about 15 years, but I’ve been able to do many, many interesting projects along the way.
May - Dividing/Dividing Head (Tom Moore)
June - Layout (Doug Blodgett)
July - Homebrew CNC (Bill Swann)
August - 3 Phase Converters (George Carlson)
September - Welding Technology (Mark VanScoter)
October - Hand Tap Operation (Doug Blodgett)