I have gotten out of the habit of regular posting as my current machining focus is a bit off the beam from what this blog started out as. I have finally admitted to myself that it will be a while before significant model railway activity takes place and also have reminded myself why I chose the blog name I did. So, I shall report on what I am doing in hopes that it will be of some interest albeit perhaps not to exactly the same audience.
To recap, I have been developing my machining skills by working on a model beam engine based on plans by Elmer Verburg. This engine is commonly referred to as #24 (Elmer created many plans and made them freely available, may he rest in peace). I have done the base, flywheel bearing, flywheel, eccentric hub, and column. Here is a dry fit of those pieces.
The part in progress is the beam. This is attempt the second as the first effort is now part of the scrap pile with the end of a #55 drill firmly embedded in it. Trying to drill that size of hole with the lathe going at 1100-ish RPM was not a success. The mill going at 4300 and a less ambition depth did the trick.
There are three 1/16th inch reamed holes in that piece. Photographing shiny aluminum close up is still something I need to work on.
Next step will be to flip the part over and mill it down to final thickness and take off the edges at an angle to produce an elongated lozenge shape. I have a plan but it may not work out. On the other hand, the only crucial dimensions on this part are the holes and the thickness of the hub. All else could be done with a saw and a file.
It has been quite some time (March!) since I posted. I have not been idle but work on Comstock Road has been minimal although I have enjoyed a few impromptu operating sessions which have gone surprisingly smoothly given the general lack of activity.
I recently reached a point in my machining journey where I felt it was time to make something that wasn’t a tool for making things. I hit upon a site containing many plans for model stationary steam engines created by the late Elmer Verburg. These plans can be built from standard metal shapes without the need for castings which makes them ideal for beginners who may need multiple attempts to make a part(ahem).
I have begun the process of creating a horizontal beam engine aka Elmer’s Engine #24. I have three parts made with the second and third requiring two attempts each due to measuring errors caused by duffing fractions to decimal conversions. I need a wall chart.
Anyway, here is the project to date with the base and flywheel bearing assembled. Eccentric hub not show as it is currently clamped in a vise awaiting drilling and tapping for a set screw.
All of those holes will eventually get something in them. It is an interesting contrast to the usual railroad model build in that each part is a project in itself requiring planning, setup and machining. It has also been a good skill bilding exercise as I have had to execute a variety of new operations.
Next part will be the flywheel, I think. This will be all kinds of new challenges as I deploy my shiny new rotary table for the first time. Adding a fourth axis to my mill means more thinking and care are required. I have laid in lots of extra stock for the likely multiple attempts. 🙂
The title seems a little silly for this one since most everybody has at least seen calipers if not used them. They are used for a reasonably precise method (I have already covered at least one unreasonably precise method) of measuring the distance between two surfaces in a quick and convenient way. Presuming you can find them, of course. Note that no vernier scale caliper is pictured above even though I own one…
The most used measurement is the outside one. I will often use calipers for marking out a part as well as measuring an existing object to find out what size it is. Handy if you have unlabeled metal stock lying about. In the picture, we can see that the shank of my 3/8″ end mill is about .001″ under sized according to my inexpensive caliper. If I needed more precision, I would get out a micrometer.
Using the other set of blades, one can measure inside distances between flat surfaces. It turns out my 21mm wrench is actually a 21.11mm wrench.
Calipers can also be used to measure depth in two different ways. The first is what I have used for years, the other end of the caliper.
The second is one I only learned about recently and while it is somewhat specialized, it allows a more reliable reading of a step using the end faces of blade end. I held it above the piece for what I fondly hope is clarity.
The alternatives to calipers are fairly well known and are all a tradeoff between precision and convenience. There are probably people out there doing fine work with just a rule or just micrometers but they are giving something up.
Calipers come in Vernier, dial and digital models. Vernier versions are the most robust and proof against fluids (cutting coolant) but slower to read. Many have both Imperial and metric scales on them. Dials are quick and easy to read but only come in one set of units. Digitals can convert between Imperial and metric, can be zeroed at any point and can give implausibly precise readings. And they need batteries which is why my pictured one is not getting used for any of the action shots.
Calipers come in a vast range of quality from very cheap plastic models (1.99!) to very uncheap ones you would be careful not to breath on. They also come in lengths from 6″ to 24″, at least at my local tool supplier which lists 83 different models ranging in price from $50CDN to over $500. Mine are much more in the $50 range (probably less) but do a good enough job anyway. I use them to get close and then check final dimensions with a micrometer if it matters.
This is one of those tools that you don’t need until you do. As evidenced previously, I have managed to turn out some parts that are less perfect that one would hoped. While the list of possible sources of error is long, a fundamental part of setting up machine tools is levelling them. Even a solid casting like a lathe bed or a milling machine base can acquire detectable twist in it when you bolt it down. To take out the twist, you put shims under the low corners or some other adjustment until the measured surface is level. To detect twist, you use a precision level.
I have avoided going through what is almost certainly a fiddly process with either of my machine tools but I decided the time has some so I acquired the Starrett level depicted. The certificate in the box asserts that each division on the tube represents .005″ difference in elevation over 0ne foot. This ought to do it.
Initial readings on the mill Y-axis ways (which are the ones that are part of the base casting suggested that my previous attempts with carpenter’s level were less than perfect. At least I didn’t buy this thing for nothing.
Fortunately, the stand has leveling feet so off I went with a wrench and a lot of bobbing up and down and cranking. It turns out that one of those .005″ marks represents about a half turn on a foot. Presuming that the other foot is on the floor… I need to develop a method that avoids trying to level an inadvertent tripod.
After a lot of faffing about, I got to about one mark of level and at least the back and front agreeing on which way that out of level goes. I called it done for now because I was chasing that mark around the corners. I need to do some more reading up but I suspect that this is where the shims come in. The top of the milling vise show just about the same reading so nothing inherently funny is going on.
There are methods of detecting twist in a lathe that don’t involve a level. Twist in a lathe bed manifests as a taper in what should be a parallel turned surface. You can turn two ends of a round bar and measure the result with a micrometer. You then shim whichever tailstock corner is low. Repeat until both ends come out matched.
You can also buy a pre-turned bar, mount it between centers and use a dial test indicator to compare ends. At least I think that’s how it works.
Presumably, you can carry out the same sort of process with a mill but given the way the mill table takes up most of the space, it would be a pain to say the least. You can’t trust the spindle or column at this stage so I think you would have to remove the table and sweep the ways with an indicator mounted on the ways. Suddenly, a fancy level doesn’t seem such a bad idea!
This is one of those purchases that will get seldom used which is why I avoided it as long as I did. My “budget” model Starrett level was about $180CDN. You pay for greater length so my 6″ model is the shortest I could get away with. The 18″ one is about $1200.
There are digital machinist levels that cost more than the analog ones. I don’t know if they work as well. They claim similar resolution and I even found one online that has an app that relays the readings. That would be handy if you wanted to avoid jumping up and down to check as you adjusted things. It would be a huge time saver if you were levelling a CNC machining center, for instance.
At first glance, a vise is not a measuring tool so why am I talking about this thing? Well, a toolmakers vise is a vise (duh) that is precision ground on just about all of its surfaces, certainly all six square sides, the jaws and ways are square and parallel to a high degree. The depicted vise is also a “screwless” design that uses an hex draw bolt instead of the usual screw to secure the moving jaw in both an inward and downward direction. This avoids introducing error due to jaw lift.
Suppose you have a part that you want to check for parallelism of some awkward surfaces. As an example, I have just made some t-nuts for securing things to my milling table. I was wondering how I did with my setup. An actual metrology application or, as a certain Youtuber says, “the surface plate: where dreams go to die”. As you can see, checking the vertical surfaces of the inverted T is not just a matter of plunking it on the surface plate. The darned thing won’t stand up on that face.
And so the vise comes into play. I know that it is very square and so if I clamp the t-nut in the vise, the clamped surfaces should also be parallel to the corresponding vise surfaces. If I check both ends, it will tell me how off it is. To take the reading, I leave the indicator and stand stationary and slide the vise and part around under the indicator tip.
And the answer is, in machinist terms, quite a bit, about .0015 if I am generous. The same error is present on the other nut I made so at least I have repeatably created the error. This is why one makes t-nuts for practice. The required precision is not great and you can mess things up and still have a usable result. If it was important, I would have to investigate the source of the error (milling vise alignment, mill head nod, etc…)
As is probably obvious, you can also use a toolmakers vise for workholding. I have seen various videos of this sort of vise being used to hold a part being milled.
Toolmaker’s vises come in different designs and many sizes. Mine is only about 2.5″ long overall. They can get expensive really fast.
As an alternative, you could clamp the part against a 1-2-3 block and rest it on the plate. Or use a v-block or some other way to prop it up vertically. In this case, you would likely need to move the indicator stand around which is finicky in that you can tilt things and mess up your alignment.
As always, you can spend a lot of money on a toolmakers vise if you want to. There are some beautiful makes and models out there that are breathtakingly expensive and certainly more than most hobbyist need. The cheapest 25mm/1″ version I found online goes for about $60CDN. Mine is a somewhat higher quality model but still accessible at least in this small size.
Today I decided to swap out the default blade that came with my metal cutting bandsaw in favour of a bi-metal blade which is a recommended upgrade. Much to my dismay, when I went to install it the direction of the teeth was backwards. How could the vendor do this to me when I bought both at the same time? ARRGH!
A bit of online research later, I found a saw vendor’s note about how you can just flex the things and turn them “inside out” and thus change the direction of the teeth… I am very glad I did the look up before I called the store to announce my ignorance.
Telescoping gauges are for measuring the diameter of holes, the width of slots, and any other gap that is impossible to get calipers into. The standard model is T-shaped with the bar of the T composed of two sprung arms with round ends. The other end of the handle has some sort of locking mechanism. You stick the appropriate sized gauge into the hole, lock the arms, pull it out and then measure the result with a micrometer or calipers.
I say appropriate size because each gauge has limited range of measurement and thus telescoping gauges come in sets or at least collections. Mine is a motley assortment bought from a used tool store.
For small holes, there is a different style of gauge that is a split cylinder with a center plug that adjusts the split. I only have one of those.
There are digital and dial direct reading bore gauges which are the more precise but more expensive choice.
The basic import sets go for about $40CDN and cover a range like 5/16″-6″. You can spend more for better ones just like other measuring instruments but for the money a dial bore gauge set would be a better buy, I think. I don’t have one of those because I have not had cause to use my telescoping gauges enough to start wanting better.
I consider this sine bar to be the most exotic measurement tool I have. I bought it mostly for fun. A sine bar consists of two cylinders of the same diameter fixed with their centers a known distance apart. The top of the connecting bar is parallel to the line between the two centers. All this done with as much precision as you are willing to pay for.
What the bar is used for is to “construct” precise angles between the bar surface and the surface the bar is resting on, typically a surface plate. Given the desired angle, one does the appropriate calculations (hence the sine name) to get vertical displacement for one end and builds that height out of gauge blocks.
Here as an arbitrary example, is a setup to get an angle of 32 degrees, 16 minutes and 27 seconds. Reference to an online calculator produced a displacement of 2.670″.
I called this tool exotic because it is difficult to conceive of a circumstance where I would actually need to measure to set up an angle this precise. I can use it as part of a machining setup or to check something like my engineer’s protractor for accuracy. I expect that an experienced machinist has more uses for one so who knows.
Budget sine bars cost less than $50CDN new so it wouldn’t break the bank if you decide you needed one. There are lots of protractor variants that are probably more practical for most jobs.
The “sine tool” family includes plates and vises. The plate is just a wide bar. The vise is a vise but includes some sort of angle locking mechanism and the two cylinders to allow precise angle setting. Like a lot of precision tools, spend as much money as you want for increasing precision well in excess of the average hobbyist’s needs.
Some may be wondering about the recent focus on machining related topics. The pure model railroading has been on a bit of a hiatus as I get geared up for some model engineering. The latest project, and it is indeed a project, is a new milling machine! I am not changing direction just adding more of them or at least the distances I can travel.
Why Get One?
After my initial experimentation with milling on the lathe, I concluded that I needed more capability to accomplish my long term goals. Getting set up was an involved process and once there, the milling “envelope” was small and speeds available were limiting. An end mill smaller than 3/8″ would require spindle speeds in excess of the Myfords ~1000 RPM top speed.
Why This One?
My model engineering aspirations date back more than 40 years so it definitely not an impulse buy! I essentially compromised on the biggest bench mill I could imagine safely fitting down the basement stairs and onto a stand in beneath my 7 foot ceiling. I suppose if I eventually end up with a ground floor shop I might add a full sized Bridgeport type mill but this ought to do and I am proceeding on that assumption.
Based on the assumption that the mill acquired would it for the rest of my life, I set out to find as good a mill of not more than about 400lbs with as many bells and whistles on it as I could manage. And that I could bring myself to pay for.
The pay for part meant either a used mill of North American or European origins or a new one of Asian manufacture. While I wouldn’t say no to a Schaublin, Deckel or Fehlmann, the new ones are way more than I could justify. A multiyear search for used bench mills turned up effectively no candidates. Lots of big manual knee mills but not bench mills. They are out there in Canada because I have seen Tom Senior mills in other people shops but nobody was selling one where I was looking. It looked like buying new was the way forward.
After considerable research, I landed on the Precision Matthews PM-728V-T. It is made in Taiwan to claimed higher standards than most modern imports. Here are the features that I considered important:
square column: two axis to tram is enough
pre-installed 3-axis digital readout(DRO): counting turns of the handwheels and allowing for backlash got old quick on the Myford
power x-axis feed: x is the side-to-side direction and the usual one involving a lot of cranking, at .100 per crank, 20 inches is a long way
370lbs: I could imagine managing that
R8 spindle: this is what Bridgeport’s have and tooling is abundantly and locally available.
120VAC power: three phase is not somewhere I want to go.
Getting the thing out of the driveway, down the stairs and on to the stand was an incremental production of about 5 days, mostly spent in preparation: building a ramp, a gantry, removing doors and handrails, etc. (Moving 400lb lumps of iron is not the time to be lackadaisical)
After the mill was in place, various infrastructure and assembly tasks were needed before any actual work could start. Assorted tooling was required as well which was a challenge in the current lockdown in Ontario.
All that being said, chips are being made and I expect everything to settle back into balance with layout construction in the near future.
Just like surface plates are a standard for flatness, gauge blocks are the machinist’s standard for length. And also like surface plates, they are less simple than they appear.
Created from well conditioned steel and polished to a very find degree, gauge blocks come in sets of different sizes that are combined to get whatever length is required. An imperial set is typically 81 blocks and covers ranges from .001-12.000″ in .001 increments and .2000-12.0000 in .0001 increments. The odd starting point for the ten thousands is because the first block is .1001 or such since nobody can make a durable block .0001 thick. Making up the required combination may count as playing with blocks. 🙂
The assembled length is used to compare or calibrate whatever you are trying to evaluate against the standard. My singular “real” usage so far has been checking the accuracy of various used instruments I have purchased. As I mentioned somewhere previously, one can mount a dial test indicator on a height gauge, zero it out on the gauge block(s) and use it to check parts for expected length.
A fun feature of gauge blocks is that you can “wring” them together. The highly polished surfaces allow a close enough fit that they will stick to each other. Very handy when you need to move a pile of four blocks.
If you don’t have a gauge block set, you can start with a micrometer and measure some object, take the result and compare it to the resulting measurement from other instruments to see if they agree. Some higher end micrometers come with a block usually called a “standard” which is used to check the mic. This is effectively a single gauge block.
Cheap gauge block sets go for about $180CDN new and things go up from there. In my case, I opted for a used set of some personal and historical interest which I will now enthuse about:
In the 1800’s, New England was a center of industrial excellence with the precision manufacturing aspect perhaps most famously represented by the Waltham Watch Co. Where you have machinists, the tool manufacturers follow and so it was with Massachusetts. That industrial sector is a shadow of its glory days but the shadow is a long one with the L.S. Starrett Company still in business. I have more than one Starrett measuring tool but my gauge block set is a product of a less well know competitor, Van Keuren.
The Van Keuren Company still exists as a brand but no longer operates out of its building in Waltham, MA. (As an aside, I worked in the Waltham area for about six years, love those brick mills) I know they still were there in 1942 because that is when my block set was manufactured. The three digit serial number suggests either an early product or one that didn’t sell a lot.
The set sill contains the inspection certificate with the deviation from labelled size in millionths! for each block. I do wonder if they still conform to those results but am unlikely to need to care. 🙂