Milling Pallet

Much of my shop time in the last year(!) has been consumed with making tools for my tools. A later addition that turned out to be way more useful than I expected is my milling pallet.

A milling pallet is a flat piece of metal with a bunch of threaded holes in it. Matching bolts, clamps, and whatever are used to fix pieces of stock in place for machining. Mine is a 6x6x1″ square of aluminum with a grid of holes spaced 1″ apart. This is a common shop project so there was lots of ideas to glean from the internet but here are the features I settled on:

  • Through holes are tapped M6 except that the top 1/4″ is reamed .25″ to take dowel pins. The pins can be used as something to bump against in a repeatable setup.
  • A shallow step is milled into the bottom to allow clamping the pallet into my milling vise. The edges of the pallet are square with that step which means I can use the edges to align things, even before clamping the vise.
  • Extra counterbored holes allow me to bolt the pallet to the top of my rotary table. The rotary table only has four radial t-slots so this greatly improves my clamping options.
  • I made two sizes of .25x.50″ toe clamps that combine with an assortment of M6 hardware to do most of my clamping.

Here is the flywheel for my beam engine project in progress clamped on the pallet on the rotary table.

What All the Fashionable Vises are Wearing

I made my milling vise some chaps! Inspired by YouTuber Yuchol Kim’s Vise Chaps 2020 (and the aggravation of trying to clean chips out of the vise innards), my holiday shop improvement is a protector for the open top of the vise.

This is just a piece of leather secured to the back of the moving vise jaw using the available outside jaw mounting points and a piece of aluminum.

I milled a 1/8x1x4″ length of big box building store mystery aluminum into a retaining bar. There is a .040″ indent milled across the entire back except the top 1/8th to give the leather somewhere to hide behind and hopefully soak up less cutting fluid.

The leather is a piece of craft store tooling leather which means it is unfinished, easy to cut and will probably soak up things well. For instance, that stain in the bottom left corner is machinist blood from when the alleged machinist forgot that end mills are sharp and failed to remove the current one from the mill when done.

One of the less noted advantages of a name brand vise is that the specs for the hole layout is well documented so I just had to put in two clearance holes for 3/8-16 bolts in the aluminum bar. And make a second trip to the big box for a third bolt after one of the first two went missing during final assembly. My shop is much tidier as a result of the ensuing hunt but I still only have two bolts. The struggle continues.

Sensitive Drilling

One of my ongoing challenges is drilling small holes in metal. The ideal RPM for a drill is aimed at acheiving the recommended surface feet per minute just like turning and milling. The problem is that my smallest end mill so far is 3/16″ whereas I have needed to drill holes less than 1/16″. For 1/16th in aluminum, I should ideally have a spindle speed of at least 12,000RPM. The maximum on my mill is 4k while the lathe is 1.1k.

Too slow RPM is a common cause of breaking small drill bits at least in my case. Pushing too hard is very easy as the leverage on my mill downfeed is designed to be happy with a 3/4″ drill. Thus my new sensitive drill feed. This handy tool is a spindle that held in the mill collet, holds a small chuck on one end and is held by a non-rotating collar. There is about 1/2″ of sprung downfeed you can do with your fingers. It is easy to feel how the operation is progressing and hopefully harder to push too hard and jam things up.

I have only used it once so far but it worked well. Pro tip: get ahold of the collar before you start the mill/drill since otherwise it will spin. Not going to grab it a knurled knob going 4,000 RPM!

Tap, Tap, Tap

In my exploration of metal working, I have had to learn a few things about taps and tapping holes.

Here are three taps from my growing collection, all for M6x1.0 thread.

All three taps look similar but if you look at the ends, you can see some differences. In order from left to right, they are:

  • Straight 4 flute tapered hand tap – this is the default one we are most likely to have used. The tapered end makes it easy to start threads but it doesn’t cut full threads until about the 5 the thread up. This can be a problem if you need threads to the bottom of a hole that doesn’t go all the way through.
  • Straight 4 flute bottoming tap – the solution to the taper tap’s limitation. It cuts almost to the bottom but would be hard to do an entire hole with. One typically goes as far as possible with the taper tap and follows up with the bottoming one.
  • Straight 2 flute spiral point or gun tap – the spiral point cuts a continuous chip that is pushed ahead of the tap. Not for holes that don’t go all the way through but good for power tapping. I made a fixture plate for clamping things (a future post) that has more than 30 tapped holes in it. It would have taken me a week to hand tap all those holes if I didn’t lose my marbles before that. Using the gun tap allowed me to use my milling machine to tap the holes under power in about an hour. Moving the work to the next position took longer than tapping a 1 inch deep hole. It is also the only time I have used the reverse on my mill.

DROp Dead Gorgeous

A fine old machine and her new cybernetic enhancement! After much (years) consideration, I decided to invest in a digital readout (DRO) for my Myford ML7 lathe. The DRO experience I have gained on my milling machine convinced me that increase in accuracy and precision would be worth it. (A DRO measures actual positions unaffected by backlash in the screws)

Next came a version of the build vs buy dilemma. Go with the UK vendor that sells machine specific kits for the ML7 or cobble together my own from components sourced on the internet. This sort of design challenge in an area where I am decidedly inexpert can cause me to decent into analysis paralysis for a long time. Maybe forever. Thus, I eventually decided to substitute money for stomach lining and invest in the machine specific kit from Machine DRO.

Upfront, I will say that I estimate that the kit cost roughly twice as much as buying individual components off the net would have. Given my historical propensity for underestimating things, the actual savings would be less than that when the job was finally complete. If, I should say. With the proven design and excellently written and illustrated instructions from M-DRO, I have a working installation 4 calendar days after the package arrived.

The kit is mostly bolt together using the included hardware including 1/4″ BSF hex studs that bolt into the existing taper attachment mounting holes on the back of the lathe bed. I challenge anyone to find those on this side of the Atlantic! The one notable exception and one that is optional but preferred, is installing the magnetic tape on the cross slide. This requires drilling and tapping two holes for mounting an extension block on the back of the slide and milling a 1.8mm slot in the bottom of the slide. My very first experience in working with cast iron!

I discovered that my milling machine had about of 1/4″ of room left when I set up to drill those holes.

The cross slide is way too big to hold in my milling vise so I had to clamp it directly to the milling table. This is another first and the also the first time I really used the clamping set that everybody buys when they get a mill.

The green painters tape is intended to keep debris off of the important sliding surfaces of the slide. Cast iron doesn’t produce chips but rather grey dust that is very abrasive. I ended up following along the milling passes holding my shop vac nozzle right up by the cutter. Who knew you needed dust collection for metal working?

All when according to plan and I have got the display mounted, at least temporarily on the backsplash. I am not entirely please with this but it will do for now. The backsplash is not as solid as it should be for this sort of purpose and I plan to eventually mount the display on the supplied mounting arm but I need to execute my under lathe cabinet plan first.

Final cleanup remaining is cable management and grounding the display. The read heads come with what I presume are standard length armoured cables that clearly would work for going all the way from one corner of a full sized mill or enormous industrial engine lathe. The kit came with copious hardware for this purpose which is much appreciated.

I am looking forward to learning how to use this thing and see what it can do to improve my results.

Learning the Rudiments of 3D Printing

I have been working on improving the organization and storage of my machine tooling and have decided to use that as pretext to learn a bit about 3D printing. Uncharacteristically avoiding leaping into yet another manufacturing technology, I took a class and am using the printing facilities at one of the Toronto Public Library system’s “Digital Innovation Hubs”. Only basic PLA fused deposition printing is available but that is more than good enough for learning.

Pictured is my design for a bracket that Ican hang one of my lathe’s quick change tool holders on. I have seven of those so far with a strong likelihood of more. They currently sit on a shelf and I keep picking them up one by one to find the one I want. With this bracket, I can hang them all in an orientation where I can see the tools they are holding.

I started out with a different design downloaded from Thingiverse but that proved unsatisfactory due to an overly tight fit and not being the orientation I wanted. This led me to bashing through the basic TinkerCAD tuturials and creating my own design. My design also minimizes print time since the TPL standard printing time slot is 2 hours. There is an all day option but that presents other challenges.

Perhaps I will one of the new resin printers eventually but the library option is working for storage widgets, at least.

Metrology Monday: Calipers

What Are Calipers For?

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.

Alternatives

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.

Options

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.

Metrology Monday: Precision Machinist’s Level

What Is A Precision Level For?

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.

Alternatives

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!

Options

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.

Metrology Monday: Toolmakers Vise

What’s A Toolmakers Vise For?

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.

Alternatives

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.

Options

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.

Backwards Bandsaw Teeth

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.