It looks like Adam mounted the sensor in the spindle cap and is using putty to hold the magnet on the spindle. I would have done it a little differently.
Here’s an idea I haven’t seen before. Adam made a very inexpensive tachometer for his variable speed X2 mini-mill using a cyclometer (bicycle speedometer). Almost any wired cyclometer will work and you should be able find one with a nice big display for less than $15. (You probably don’t want to get one that has a wireless sensor because they’re more expensive, you’ll have an extra battery to replace occasionally, and you might get erroneous readings caused by the receiver picking up electrical noise from your motor).
Someone left a comment with a link to a tutorial on Instructables with more details about making one of these. The author, Jose, explains that you basically just have to glue the magnet that comes with the cyclometer to your spindle and somehow mount the sensor so it’s within a 1/4-inch or so of the magnet when it spins around.
The sensor sends a signal to the cyclometer every time the magnet goes by it. The cyclometer uses that information to calculate the bike’s speed using the wheel’s circumference, which you have to tell it. In this case though, we don’t want to know speed, but RPM instead. So Jose says to use 268 mm for the wheel circumference if the cyclometer displays the speed in MPH, and enter 167 mm if it is displaying the bike’s speed in KPH.
He says those numbers will display the RPM in hundreds, regardless of circumference of the object you mounted the magnet on. I don’t why that is, even though I was once good enough at math to get an A in college calculus III. There’s a chance I’ll wake up in the middle of the night with the answer, or have a revelation while in the bathroom. But just in case I don’t, I would appreciate it if you would leave a comment with the answer if you have a good “explanation for dummies.”
I want to tell you about Ralph Patterson’s free plans for a ball turning tool post that will fit a 7-by-whatever mini-lathe, and show you how he used it to fix a broken shower head. I’ve also included a YouTube video that shows a similar tool post being used to make a ball end for a tool handle. Near the end of the article you’ll find a link to download the plans for this tool, along with a link to where you can get Ralph’s other plans. And if you read carefully you’ll also find a link that leads to plans for a ball turning tool that will fit a 9×20 lathe.
This ball turning tool post is part of set of more than 25 free plans that Ralph made for some very useful mini-lathe accessories and modifications. He also designed a boring bar holder, a quick change tool post, a leadscrew hand wheel, two versions of a tailstock lock, a carriage clamp based on Vicki Ford’s design, a die holder, a modification for slowing down the leadscrew feed rate, a file guide, a spindle indexer, a spindle crank, a height gage that uses a digital caliper, an adjustable tool rest for a bench grinder, and much more. In addition to drawing nice plans, Ralph also did something that I think is very smart. He included photographs with most of them so that those, like me, who don’t have a lot of experience reading prints can easily see how the parts fit together and what the finished project will look like. He also includes a parts and material list with his more complicated designs, which is something that I wish more people did.
The original swivel neck was made from plastic and it broke
Ralph is obviously a smart, gifted designer who knows a lot about mini-lathes, a skilled machinist, and a excellent CAD drafter. I’m very surprised that his designs and plans aren’t more widely known. (I intend to do something about that if he doesn’t mind).
His ball turner is adapted from one that Steve Bedair made for his 9×20 lathe. If you go to Steve’s web site you will not only find free plans for his design, but also photos showing how it is made and used, along with pictures of some of the things he has made with it. Besides things like ball ends for handles, this kind of tool post can also make beads on a straight rod, and with a little modification it can also do coves. They’ve also been used to make the lenses for optical center punches.
Ralph’s ball turner attaches to the top of the cross-slide with a couple of bolts and it doesn’t look like it will be hard to make. The parts will need to fit together properly they won’t help cause chatter, but still allow the body to turn smoothly and easily. The most critical dimension is the height of the cutting bit and Steve Bedair has a nice picture that will show you how he measured that. The base has a recess that can probably be bored on a lathe if you have a 4-inch, 4-jaw chuck, otherwise you’ll need a mill and a boring head. Ralph gives you a choice of four different tool bit holders that you can make. Three of them use carbide inserts and they’ll require you to mill a number of angles, some rather precisely. A forth version uses a HSS cutter made from a 3/16-inch drill bit. Both it and the HSS cutter look like they should be fairly simple to make.
If you would like to get in touch with Ralph or thank him for the plans then the best way to do that is to join the excellent 7×12minilathe discussion group.
Ralph said that carbide insert he normally uses wouldn't provide enough clearance to cut the left side of the ball. So he temporarily rigged up a larger cutter.
The finished repair
If you watch the end of the video you’ll see how the ball unscrews from the shaft it was made on. You’ll also find some links to other things you can make with ball turning tool post.
I’m not exactly sure who Dave Akin is, but he’s obviously a wise man. He wrote these thirty-three Laws of Spacecraft Design that are full of astute insights and observations that can be applied to many other engineering, design and management situations. He’s kindly granted permission for them to be reprinted, and so here they are:
1. Engineering is done with numbers. Analysis without numbers is only an opinion.
2. To design a spacecraft right takes an infinite amount of effort. This is why it’s a good idea to design them to operate when some things are wrong .
3. Design is an iterative process. The necessary number of iterations is one more than the number you have currently done. This is true at any point in time.
4. Your best design efforts will inevitably wind up being useless in the final design. Learn to live with the disappointment.
5. (Miller’s Law) Three points determine a curve.
6. (Mar’s Law) Everything is linear if plotted log-log with a fat magic marker.
7. At the start of any design effort, the person who most wants to be team leader is least likely to be capable of it.
8. In nature, the optimum is almost always in the middle somewhere. Distrust assertions that the optimum is at an extreme point.
9. Not having all the information you need is never a satisfactory excuse for not starting the analysis.
10. When in doubt, estimate. In an emergency, guess. But be sure to go back and clean up the mess when the real numbers come along.
11. Sometimes, the fastest way to get to the end is to throw everything out and start over.
12. There is never a single right solution. There are always multiple wrong ones, though.
13. Design is based on requirements. There’s no justification for designing something one bit “better” than the requirements dictate.
14. (Edison’s Law) “Better” is the enemy of “good”.
15. (Shea’s Law) The ability to improve a design occurs primarily at the interfaces. This is also the prime location for screwing it up.
16. The previous people who did a similar analysis did not have a direct pipeline to the wisdom of the ages. There is therefore no reason to believe their analysis over yours. There is especially no reason to present their analysis as yours.
17. The fact that an analysis appears in print has no relationship to the likelihood of its being correct.
18. Past experience is excellent for providing a reality check. Too much reality can doom an otherwise worthwhile design, though.
19. The odds are greatly against you being immensely smarter than everyone else in the field. If your analysis says your terminal velocity is twice the speed of light, you may have invented warp drive, but the chances are a lot better that you’ve screwed up.
20. A bad design with a good presentation is doomed eventually. A good design with a bad presentation is doomed immediately.
21. (Larrabee’s Law) Half of everything you hear in a classroom is crap. Education is figuring out which half is which.
22. When in doubt, document. (Documentation requirements will reach a maximum shortly after the termination of a program.)
23. The schedule you develop will seem like a complete work of fiction up until the time your customer fires you for not meeting it.
24. It’s called a “Work Breakdown Structure” because the Work remaining will grow until you have a Breakdown, unless you enforce some Structure on it.
25. (Bowden’s Law) Following a testing failure, it’s always possible to refine the analysis to show that you really had negative margins all along.
26. (Montemerlo’s Law) Don’t do nuthin’ dumb.
27. (Varsi’s Law) Schedules only move in one direction.
28. (Ranger’s Law) There ain’t no such thing as a free launch.
29. (von Tiesenhausen’s Law of Program Management) To get an accurate estimate of final program requirements, multiply the initial time estimates by pi, and slide the decimal point on the cost estimates one place to the right.
30. (von Tiesenhausen’s Law of Engineering Design) If you want to have a maximum effect on the design of a new engineering system, learn to draw. Engineers always wind up designing the vehicle to look like the initial artist’s concept.
31. (Mo’s Law of Evolutionary Development) You can’t get to the moon by climbing successively taller trees.
32. (Atkin’s Law of Demonstrations) When the hardware is working perfectly, the really important visitors don’t show up.
33. Space is a completely unforgiving environment. If you screw up the engineering, somebody dies (and there’s no partial credit because most of the analysis was right…)
My workshop is in the back of small, detached and mostly uninsulated garage. I have an assortment of kerosene, propane and electric heaters that can make it pretty comfortable to work in it during most of the winter. But this year it has been so consistently cold here in upstate New York that there’s been no point in even trying to warm it up, especially if I only have a couple of hours to spend in the shop. Although the heaters can quickly warm up the air temperature enough to make me comfortable, it takes a lot longer for the machines to warm up and I don’t like running them while they’re still cold soaked. I also have some other issues with the garage, like my wife wanting to put her things in it, and having to walk a few feet through rain or snow to get to it.
That’s why I’ve started thinking about moving it to a corner of our basement that I partitioned off and once used as a home office, which was affectionately known as “Rob’s Cave.” The room is not much bigger than the space I’m using now, so I need to carefully plan where everything is going to be. I also want to do some things differently this time. For example, in the past I’ve usually made workbench tops by gluing together two thicknesses of .75-inch particle board, rounding over the front edge with a router, and then giving them a nice painted finish. They’re sturdy, dense, inexpensive, and their heavy weight helps prevent and dampen vibrations. But oil based paints are almost impossible to obtain now, and the latex paint I used still feels a little tacky almost two years later and it hasn’t held up that well. I also really wish I had drawers under the benches, but I don’t want to spend time making wooden ones that I’ll have to leave behind if we ever decide to move someday.
This time I’m probably going to buy some laminated kitchen countertops for the new shop, if I build it. But I don’t know what I’m going to put them on. I don’t want to use kitchen cabinet bases because even cheap ones will probably be too expensive. I also want my bench tops to be at least two or three inches higher than normal because I’m tall. To get the drawers I want I’ve thought about buying some roll-around tool cabinets, taking the wheels off of them, and putting them under the workbenches. But I still want a frame and not the tool chests to support the bench tops, and I haven’t figured out how I can build a strong frame that will have enough height underneath it for the cabinets and still keep the countertops about 39-40-inches high.
I also have to figure out how I’m going to control the swarf and keep it out of the rest of the house. Even though I’m pretty good about keeping my shop vacuumed, I still somehow occasionally manage to track some of it into our house, which always gets my wife worried that one of our cats, dogs or grandkids will get cut by a piece. I also just realized that I might have a problem keeping Jack, our Labrador, out of the new workshop. He’s a great dog, but I don’t like him around when I’m working. He usually stays out of the garage because he doesn’t like it, but that’s not true for the basement. The room has a door, but we also have cats that don’t deal well with closed doors when they know someone’s inside that might give them a treat or some attention.
I want to tell you how I made the walls for my basement office in case you might need to quickly, easily, inexpensively or temporarily close off part of your basement or garage for a work area. About seven or eight years ago we needed a quiet private space in our basement for a home office and a lot more shelves for storage. So I went and bought three Gorilla Rack heavy-duty shelving units from a wholesale club for about $50 each. They’re 4-feet wide, 6-feet high, 18-inches deep and much sturdier and heavier than sheet metal shelving units. I bolted them together end-to-end to make a wall in my basement and positioned it at just the right distance from an existing wall so that I could hang a pre-hung interior door in the opening. I then took 4×8-foot sheets of luan plywood and cut them to length to match the height of the ceiling, and then attached them to the backs of the shelves with small bolts and washers. The luan was mounted so that some of the shelves were accessible from the office and the rest from the other side of the wall. The final step was to cover up the seams between the units with some attractive pine boards and paint the wall white to help reflect light and brighten up the room.
Which somehow finally brings me to the cool picture of Mtneer Man’s workshop. I like looking at other people’s workshops because I’m always hoping to get some good ideas for my own. Well if you look at the pictures in Mtneer’s photo gallery you’ll see that he has lots of good storage ideas, lots of tools, and apparently enough space for at least four workshops dedicated to different things.
I’d like to look at more pictures of workshops, so if you’ve got some send them along or send a link. I’d also like to know if you have any suggestions for me.
This essay by “Mikey” is the winner of our “Machining Metal as a Hobby” contest. The object was to tell visitors about home machining and try to get them interested in doing it as a hobby. I think he wrote a wonderful essay and I would like to thank him for taking the time to enter the contest. — Rob
“Hmmm … this isn’t as easy as it looks.” I had just taken the first cut with my new lathe and the piece of aluminum rod I was cutting looked like a rough rutted road instead of the nice shiny surface I thought I would get. The noise and vibration didn’t thrill me, either. I eventually figured out that the speed control was actually important, as was the feed wheel I had so merrily cranked. After a few tries I finally got a mirror finish on that part but I realized that I had just flunked Metal Cutting for Dummies, Special Ed Division.
I didn’t set out to be a machinist, hobby or any other kind. I simply had a whole slew of other interests that I was involved with and machining was supposed to be a supporting activity. I realized that it was a major advantage to be able to repair almost anything, make something that is difficult to find or doesn’t even exist, or improve something that could be made better. So rather than make do, I decided to make parts. At least that was the intent.
This was 13 years ago and my interest in machining has turned into my main hobby! My other interests have taken a definite back seat and I’m happy to say that while I never intended to be a hobby machinist … that is what I am.
So, what happened? What could be so interesting about this hobby that it can keep someone engaged for more than a decade and put all his other interests on a back burner? I think it’s because you’re always learning. You see, hobby machining is not just about machining. Its also about understanding your metals and other machineable materials and how they like to be cut, tools, tooling, cutters and their geometry, coolants and chemicals, heat treating, electricity and electronics, physics, geometry and trigonometry, hydraulics, machine design, and a myriad other subjects. This pursuit of knowledge is driven by each project you do or problem you need to solve. Before you know it, you know a lot about a lot of things! This enriching experience coupled with the ability to make just about anything is really what keeps this hobby so interesting.
My Tru-Cut P-20S reel mower, restored to like-new condition for under $400.00 in my shop. Unlike its $1700.00 new counterpart, this one has precision bearings, stainless fasteners, and a reconditioned motor that runs great. Restorations like this are simple for a hobby machinist. Like I said, you can make stuff.
Whenever people ask me what I can make on my machines I answer, “Oh, just about anything.” They always look puzzled because “anything” covers a whole lot of territory. So here is the honest answer – you can make almost anything from just about any machineable material that fits within the working envelope of your equipment. If you need a custom part such as a hose adapter with metric threads on one end and SAE threads on the other, this is easily done. Need a mandrel to make a pen on your lathe? Make the mandrel, slip the wood onto it and turn the pen. Model cars, model engines, steam engines and incredible locomotives are made by hobby machinists all the time. How about parts for an invention you have in mind, or an adapter to fit a special lens onto a camera it normally wouldn’t fit? The possibilities are seemingly endless and, once you learn how to machine stuff, you can make them.
I will tell you up front that this is not the cheapest of hobbies because you will need to buy some precision machine tools and their related accessories, precision measuring tools, and materials to make stuff from. Depending on the size of the equipment you choose this can range from affordable to very expensive. Most of us purchase a basic package to get us started and buy accessories and other tools as needed so that the cost is spread out but the cost is still there.
Is it worth the cost? Absolutely. In fact, while your equipment will cost you up front it can save you a lot of money in the long run by allowing you to make things that may be quite expensive. My last project was an interchangeable-tip live center. The commercial version of this tool runs about $1500.00; I made mine for about $25.00 and it is every bit as accurate as that expensive commercial model (they don’t even make one to fit my lathe). The cost of this tool alone would have paid from my lathe and my mill!
This live center is made from 1144 semi-hardened steel, with heat-treated O-1 steel tips. It was made entirely on the lathe and outperforms the OEM live center in both function and accuracy.
I also recently repaired a kerosene-burning clothes iron. It was an heirloom owned by a friend and the brass pump handle had snapped. I was able to reproduce the handle, repair the piston and it fired right up. It now sits on a shelf next to her grandmother’s picture. You can’t put a price on the smile I got from her!
There have been so many situations where being able to make something has salvaged a broken item or vastly improved the function of something that it’s hard to list them all but you get the idea. So, what does it take to do this stuff?
At the heart of any machine shop you will find a lathe and a milling machine. These are the two pieces of equipment that enable a machinist to do his or her thing.
The lathe works by turning your work piece while you move a cutter into it to cut it to the size and shape you need, producing a cylindrical object with precise dimensions. Things like shafts, pins, knobs, screws and bolts, nuts – anything that needs to be cylindrical or round. Called the King of machine tools, the lathe is one of the most useful and versatile tools you can own.
With the mill, the cutter turns instead of the work piece. The work is held in a vice or fixed to the table and is moved into the cutter to produce the shape or profile you want. This table is able to move in two axes (side to side and front to/and back), while the headstock that holds the cutter can move in a third axis (up and down). Control of these three axes allows you to shape a work piece into just about any shape you need. The mill is said to be the only machine that theoretically can reproduce itself and most of the work in a machine shop is actually done on this machine.
Each of these machines performs their basic functions – a lathe cuts a cylinder and the mill profiles and shapes. Each machine is able to perform a huge variety of other things by using attachments or accessories that expand on these functions. For example, a lathe can cut a cylinder, which can then have a knurled finish put on it by using a knurling attachment.
This is a rear-mounted straddle knurler adapted from a design by Chris Heapy of the UK. It is made of steel and 6061 T-6 aluminum. Other than the spring and screws it was made entirely on the lathe and mill. On the right is a knurled finish made with this tool; it will become a knob for an archery bow sight.
Lathes and mills come in a wide variety of sizes, from tiny watchmaker’s machines to gargantuan shipyard machines. The machine is generally chosen to suit the needs of the user. For example, if you live on a farm and must make repair parts for a tractor you need a lathe with enough capacity to do that. On the other hand, if you live in an apartment and your shop is in the spare bedroom then you will need a much smaller machine that you can carry and put away when you’re done. In general, the cost of the machines and their accessories is proportional to their size, and the size of machine is chosen by estimating the largest work piece it will have to work on.
For the beginner this size thing can be a conundrum. How do you know how big a part you need when you haven’t needed to make it yet? I can’t tell you that but it may help to know that I am an average user who lives in a city and makes parts for my own use. I own a Sherline long bed lathe and milling machine to make stuff for cars, machine restoration, welding and woodworking equipment, car audio, archery equipment, lawn equipment, fishing stuff, general repair work – the list goes on and on. For me, the vast majority of my work is under 6″ long and less than 1″ in diameter. I do need to go larger on occasion and my lathe can turn a piece up to 3″ in diameter (up to 5″ with risers) and up to about 15-17″ long. I can turn or cut most materials, from wood to plastic, mild steel to stainless steel, and just about anything in between. I have not exceeded the capacity of my lathe or mill yet but I’ve come really close.
My point is that a small machine – in my case a “miniature” or “mini” machine – is capable of doing the vast majority of the work I need. This class of machine is probably amongst the lowest in cost; there are a LOT of them to choose from and most are available as manual or CNC machines. Rather than go into a description of the field I would suggest doing some homework if you are considering joining us in this hobby. There is a lot of information on the net, in videos, books, magazines and the maker’s websites so you can make an informed decision. Or you can always ask Rob!
Before ending I want to offer a bit of advice about buying precision measuring tools, and only because it is a potential sinkhole. In this hobby you will discover that you can only cut as accurately as you can measure and to measure you need tools. I’m sure you’ve heard of micrometers, vernier or dial calipers, dial indicators and the like. These instruments vary in cost and quality but, in general, you get what you pay for. If I were just getting into machining here is what I would do. Go to the Long Island Indicator Service website and learn about what these instruments do and which ones are the best ones in each category, then go out and buy the best one – and buy it once. You don’t need to buy it from Long Island Indicator Service, though if you do you will find them to be honest and of high integrity. Many of the finest tools are for sale on eBay for a fraction of their retail cost; this is where I would check first.
If you know a photographer with a really good tripod I would bet money they have 3 or 4 cheaper tripods sitting in the closet that more than equal the cost of the good one. Precision measuring instruments are like tripods. Save the money by buying the best instrument for your needs and only buy it once. You will be very glad you did … and don’t ask me how I know this.
I hope this discussion gives you an idea of what this hobby is like. It isn’t just for guys, it isn’t hard to do, you don’t have to be rich or have a huge shop, and you don’t have to be “mechanically inclined.” You can get into it to craft incredible model aircraft or jewelry, carburetor parts … or you can do it to make stuff, like me! You’ll learn a great deal about a wide variety of subjects and the confidence you gain as you hone your skills is priceless. The only thing I can think of that is more fun than this is maybe your favorite Black Diamond ski slope … nope, not even that!
Mikey
2010
This is a hub for a custom coffee roaster, shown with a tap in one of 13 precision-spaced holes. It was turned on the lathe and finished on the mill in well under an hour.
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