Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`MAKE IT FROM
`~"'-._~~
`
`METAL
`
`MENU
`
`RESOURCES
`
`MACHINING
`
`WELDING/FABRICATING
`
`SPECIAL PROCESSES
`
`FORGING
`
`MATERIALS
`
`HOBBYIST GUIDES
`
`Machining Square Inside Corners: Conquer the
`Nightmare!
`
`1 of 22
`
`9/8/2020, 9:53 AM
`
`Page 1 of 22
`
`
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`MAKE IT FROM
`~"'-._~~
`
`METAL
`
`MENU
`
`RESOURCES
`
`MACHINING
`
`WELDING/FABRICATING
`
`SPECIAL PROCESSES
`
`FORGING
`
`MATERIALS
`
`HOBBYIST GUIDES
`
`Machining Square Inside Corners: Conquer the
`Nightmare!
`
`1 of 22
`
`9/8/2020, 9:53 AM
`
`Page 1 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Few words will make a machinist swear as quickly as "sharp inside corners".
`
`There's good reason for this. They're an absolute pain, and often totally unnecessary.
`
`Let's go over why square inside corners face such animosity from machinists, how you can
`
`design machined components so that they won't need these corners 99.99999999997%
`
`of the time, and what can be done when you're facing the 0.00000000003% of occasions
`
`that actually require them.
`
`If you want to skip straight down to the part on how to make them, then use the table of
`
`contents to navigate.
`
`Table of Contents
`What is a Square Inside Corner?
`Alternative Styles of Corners
`Radiused Corner
`One-Sided Undercut
`Two-Sided Undercut
`Using Smaller Cutting Tools
`Tools and Equipment for Sharp Internal Corners
`
`2 of 22
`
`9/8/2020, 9:53 AM
`
`Page 2 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Broaches
`Filing/Hand Work
`Shapers
`Wire EDM
`Sinker or Ram EDM
`Alternative Manufacturing Methods
`Laser Cutters
`Casting
`3D Printing or Metal AM
`
`What is a Square Inside Corner?
`These dreaded square inside corners are anywhere that a round cutting tool will have a hard
`
`time reaching. Let me illustrate:
`
`accessible
`ergeome ry
`
`Pocket geometry with square corners - doesn't really work so well.
`
`Since the tool needs to rotate in order to cut, there is no way for one of these styles of tool
`
`to make a sharp inside corner.
`
`Alternative Styles of Corners
`While these square corners look great on paper (or a computer screen), they're often simply
`
`not a good way to make machined components. Let's look at some common alternatives.
`
`3 of 22
`
`9/8/2020, 9:53 AM
`
`Page 3 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Radiused Corner
`For many applications, (approximately 99.735% of the time, actually) you can simply allow
`
`for a radius to be in the corner. Typically this isn't a big deal, so unless there is a very specific
`
`reason as to why having a normal radius is impossible, just go this route.
`
`Here's an example of what this would look like, using the example of a pocket:
`
`A 0.250" radius will allow for a 1/2" endmill to easily and inexpensively cut this pocket.
`
`This is the way that the aerospace industry has been designing components for centuries.
`
`Ok, maybe not centuries, but you get the idea.
`
`A radius on internal corners is a good thing.
`
`Ok, so let's say that simply putting a radius on the inside corners won't work for you. Maybe
`
`there's a mating part that's square and it needs to fit in that pocket that we were using as an
`
`example above.
`
`There are a few ways around this. Either you can round the corners on that mating piece to
`
`make it fit, or you can make undercuts in those corners. Let's take a look at some examples.
`
`One-Sided Undercut
`
`4 of 22
`
`9/8/2020, 9:53 AM
`
`Page 4 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`This is the easiest type of undercut for manual machines, since no extra calculations are
`
`required. All you need to do is cut half the diameter of the tool further in one axis. Here's an
`
`example:
`
`One-sided undercut
`
`And here's an example of what it looks like with a mated part:
`
`One-sided undercut with mated block
`
`5 of 22
`
`9/8/2020, 9:53 AM
`
`Page 5 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Block
`
`Undercut allows
`block to fit
`accurately within
`the pocket
`
`Two-Sided Undercut
`This is an undercut that balances the removed material on either side of the corner, and the
`
`result is an overall stronger corner. It takes a little bit more calculation for manual machines,
`
`but for CNC it's extremely straightforward. This style is my go-to whenever it's allowed.
`
`The two-sided undercut balances the material removed on both sides of the corner and
`removes the least amount of material
`
`6 of 22
`
`9/8/2020, 9:53 AM
`
`Page 6 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Two-sided undercut with block
`
`Here's a sketch that illustrates how to design the two sided undercut:
`
`The circle is coincident with the corner, and then two sketch lines with vertical/horizontal
`constraints are made equal length to center the circle around the corner.
`
`Now in these examples, there is no clearance. If the mating part has a broken edge, this isn't
`
`a problem. If it's a sharp edge, I like to add a bit of clearance on that corner undercut to make
`
`sure it will always cut cleanly. Something like 0.010" on a 0.25" radius undercut usually
`
`works perfectly fine.
`
`Here's a pro tip: If you're wanting something CNC machined, make the radius slightly
`
`oversized from the intended tool diameter. What this does is reduce the contact area of the
`
`cutter against the finished part geometry, and will result in a better surface finish.
`
`I'll usually try to give an extra 0.010"-0.015" extra clearance for most tools. So, for example,
`
`7 of 22
`
`9/8/2020, 9:53 AM
`
`Page 7 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`if I'm using a 0.250" endmill, I'll make my corner radii 0.135" instead of 0.125". If I'm using a
`
`0.500" endmill, I'll make the rads 0.265". ltjust works better.
`
`My favorite way of designing this is to add the radius to match the exact cutter diameter,
`
`then offset the surface by the 0.010" or 0.015" - that way you get both your smooth,
`
`chatter-free surface finish and the extra corner clearance to make it work every time.
`
`Using Smaller Cutting Tools
`This is one option that often comes up in conversation. If you really need corner rads, how
`
`small you can make them?
`
`The real question is how small they need to be. The smaller the rads, the more time and
`
`expense there will be in the process. Let's go over some guidelines that can help you make
`
`this call.
`
`What's basically going on here is that the practical radius of the inside corner is heavily
`
`related to the length of the tool required to cut it. So if you need a deep pocket cut, you'll
`
`need a long tool.
`
`Really long, skinny tools just don't have the rigidity to work that well in real life. If it's at all
`
`possible to avoid them, please do so.
`
`Thin, long end mills perform wonderfully on a computer screen when you're first learning
`CAM. In real life, they're miserable.
`
`For a good reference, look up what endmills are standard length and which ones are extra
`
`8 of 22
`
`9/8/2020, 9:53 AM
`
`Page 8 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`length. Standard length endmills can be run with no problem whatsoever. Extra length
`
`end mills need to be run slower, and a good surface finish is more difficult the longer the tool
`
`gets.
`
`As a rule of thumb, here are some comments on a few length to diameter (D) ratios:
`
`2xDto
`3xD
`
`No problem whatsoever, use this whenever possible.
`
`3xDto
`5xD
`
`Extra length tooling needed for reach, but still doable. It just needs extra
`consideration.
`
`5xDto
`lOxD
`
`The machinist will likely use your name as a curse word. Special tooling is
`generally required.
`
`Over
`lOxD
`
`At this point, you should be considering whether traditional machining alone is
`the best route, or whether other processes should be considered. This will
`start to get expensive quickly.
`
`Now these aren't hard and fast rules, and some shops specialize in jobs that require long
`
`tools. But you'll probably find that the majority of general machine shops will follow this
`
`trend.
`
`Tools and Equipment for Sharp Internal Corners
`There are actually a lot of tools and equipment out there that will give you sharp internal
`
`corners to varying extents, but they nearly all share something in common: they're
`
`expensive.
`
`Let's go over them.
`
`Broaches
`A broach is a toothed tool that's used to remove material. There are two kinds - linear and
`
`rotary.
`
`Linear broaching is probably the most common of the two. It's a typical way of making
`
`9 of 22
`
`9/8/2020, 9:53 AM
`
`Page 9 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`square through holes in thinner plates or keyways.
`
`Even though the tools themselves can be expensive, they're a great solution for production
`
`runs.
`
`For linear broaches, the function is similar in concept to a band saw blade, except that each
`
`tooth is higher than the next. You can drill a hole in a plate, insert the broach, then use a
`
`machine (like an arbor press, hydraulic press or a broaching machine) to push the broach
`
`into the workpiece, with each tooth removing a small amount of material until the final
`
`geometry is reached.
`
`I'm going to make use of videos to illustrate these manufacturing methods, since they will
`
`allow you to quickly wrap your head around how they work. I didn't make these videos
`
`myself, and I apologise in advance for the awful music. You may want to mute your speakers.
`
`Here's what it looks like when you're using a broaching tool with a press:
`
`Square Hex Push Broaching I 800-247-2024
`
`a
`
`Here's an example of a large broaching machine, which is generally only used for very large
`
`production runs:
`
`10 of 22
`
`9/8/2020, 9:53 AM
`
`Page 10 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Vert ica l Hydraulic Broaching Machine - MEGA i6
`
`a
`
`There are different styles of linear broaches, too. Some attachments can be added to
`
`machines like a CNC lathe to cut internal keyways and other geometry. Here's an example:
`
`LinA Live Tool Lathe Broach Video
`
`a
`
`Rotary broaching is really cool - it's a way of making internal polygon geometry, and it can
`
`be done extremely quickly in a CNC mill or lathe. It can also be done for making external
`
`geometry, such as splines and hexes.
`
`Here's an example of what this looks like:
`
`11 of 22
`
`9/8/2020, 9:53 AM
`
`Page 11 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Internal and External Rotary Broaching
`
`a
`
`The downside to rotary broaching is that the units themselves are very expensive, so they're
`
`typically only practical for medium or high-volume production.
`
`Even for linear broaching, any tool that needs to be custom-made can easily cost tens of
`
`thousands of dollars.
`
`Generally, though, off-the-shelf broaches aren't terribly expensive. Some shops will stock
`
`common sizes for regular work, such as keyway broaches.
`
`Filing/Hand Work
`This is more so appropriate for hobbyists. You can use a file to square up corners.
`
`Obviously, it'll be tricky to maintain any kind of accuracy with this method, but it's possible.
`
`Some guys have old die filing machines, which speeds up the filing process, and makes it
`
`slightly more accurate.
`
`Here's a video to show you what this looks like:
`
`12 of 22
`
`9/8/2020, 9:53 AM
`
`Page 12 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Die Filer Making a Square Hole
`
`a
`
`Alternatively, you could use a pneumatic Dynafile to get it close-ish if the hole is large
`
`enough. There's a 98.2% chance that it will end up a total hack job.
`
`Some guys can do absolutely beautiful work this way, although they're usually the old(cid:173)
`
`timers and they're a dying breed. It's just not a modern way of doing it.
`
`But, ultimately, if you're the type that likes to grow your own cotton, spin your own thread
`
`and hand weave a new T-shirt, this might be right up your alley.
`
`Shapers
`These machines can usually be found in back corners of machine shops with older
`
`equipment.
`
`A Shaper is a machine that uses a single-point cutting tool in a linear motion (no rotating) to
`
`slowly cut away material.
`
`What's nice about these machines is that the tooling for simpler shapes are generally fairly
`
`straightforward, and not really all that expensive. If you're using a shaper for an internal
`
`spline, though, you'll need professionally made cutters.
`
`Here's an example of one of these machines in action:
`
`13 of 22
`
`9/8/2020, 9:53 AM
`
`Page 13 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Cincinnati Shaper
`
`a
`
`As you can see, they're not terribly fast.
`
`One thing that's worth noting about these machines with linear feeds: you need to have
`
`relief at the end of the cut. Otherwise, the chips will have nowhere to go and things will
`
`break.
`
`For most geometry, it's common to add a groove or crosshole so that the chips can properly
`
`dislodge and clear out. Here's an example:
`
`GARANT broaching - Hoffmann Group
`
`a
`
`14 of 22
`
`9/8/2020, 9:53 AM
`
`Page 14 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Wire EDM
`These are really cool machines, but they're very mysterious to a lot of people. Not a lot of
`
`machinists have worked on them.
`
`EDM stands for Electrical Discharge Machining. Basically, an electrode uses voltage to
`
`break down and desintegrate material, rather than using an actual "cutting" tool.
`
`Essentially, you're using electricity to erode the workpiece.
`
`Here's an explanation of how it works:
`
`How Wi re EDM Works
`
`a
`
`Technically, you won't get true square corners - you'll get a tiny radius that's equal to the
`
`radius of the wire (plus a little extra for something called a spark gap). Typically this will be in
`
`the neighborhood of 0.005"-0.006", although it can be smaller.
`
`If that's not acceptable for your application, it's not uncommon to do a very small undercut
`
`like what's common practice for end mills.
`
`Wire ED Ms do have their downsides, though. The cut needs to go straight through the part
`
`so that the wire can be held taut and cycle through the workpiece. A cool thing about wires,
`
`though, is that they can tilt - you can cut tapers and other interesting geometries with these
`
`machines.
`
`15 of 22
`
`9/8/2020, 9:53 AM
`
`Page 15 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Another con to this route is that these machines are very slow, especially when compared to
`
`CNC cutting tools. This means that wire EDM jobs have the potential of being pretty
`
`expensive.
`
`A huge advantage, though, is that these machines are insanely precise, and can give a great
`
`surface finish.
`
`Sinker or Ram EDM
`This process has more names than you can shake a stick at.
`
`Instead of using a wire as the electrode, a ram EDM uses a block of material (like graphite,
`
`copper, etc) to erode the material.
`
`The cool thing with this is that you end up with the negative imprint of the electrode that
`
`you made. So, for example, you can machine half the part in a CNC mill, then use the ram
`
`EDM to reach what you couldn't on the mill.
`
`Here's a video that explains the process:
`
`Introduction to Ram/Sinker EDM
`
`a
`
`The down side to this process is that you need to make an electrode, which will wear out
`
`quickly and need to be replaced. If you need something very precise, you may need to make
`
`a roughing and a finishing electrode. Ram EDM is also a very slow process, so it ain't cheap.
`
`16 of 22
`
`9/8/2020, 9:53 AM
`
`Page 16 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Alternative Manufacturing Methods
`It might be that the part you want to produce doesn't need to be machined. Or maybe it
`
`could be made using a few different processes.
`
`Here are some other manufacturing methods that might be useful.
`
`Laser Cutters
`If you have work that's 2D and made out of sheet metal or thinner plate, laser cutting can be
`
`a great solution. It's very economical, and there are laser cutting shops nearly everywhere.
`
`You still won't have perfect square corners, since the laser has a diameter and the kerf is a
`
`little larger than the laser, but usually this radius is so small that it's negligible.
`
`The main disadvantage to laser cutting is the surface finish and accuracy. While you can
`
`usually get features just that are+/- 0.005" on something like a 1/4" thick steel plate, you'll
`
`find that the surface finish is considerably rougher than a machined surface.
`
`Here's a video:
`
`fiber laser cutting machine for mild steel sheet 4mm
`
`a
`
`Casting
`Casting metal can be a great way of getting wonky shapes, but this can be quite the art to
`
`17 of 22
`
`9/8/2020, 9:53 AM
`
`Page 17 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`learn. Lots of guys can rig up a setup to cast metal in their back yard, but the results can be
`
`pretty wildly variable.
`
`If you need something precision and you have a high volume of parts, die casting can be a
`
`really interesting solution.
`
`What is t he Die Casting Process? The High Pressure Die C ...
`
`a
`
`That's just one of the many ways of doing casting, though.
`
`Different casting methods have different design constraints. For example, for casting
`
`processes that use hard moulds, draft angles need to be added in order for the parts to not
`
`shrink and become stuck in the molds.
`
`For lower a lower cost method, sand casting might be practical. The main challenges with
`
`this method are getting a good surface finish and dimensional stability, since metal shrinks
`
`when it cools.
`
`3D Printing or Metal AM
`This is a rapidly growing technology, but the basic idea is to take the opposite approach to
`
`most traditional manufacturing methods.
`
`Instead of taking a block of metal and whittling it away into a finished product, metal AM
`
`(additive manufacturing) takes raw metal (often in powder form) and fuses it together, like
`
`18 of 22
`
`9/8/2020, 9:53 AM
`
`Page 18 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`with a laser or electron beam.
`
`It's pretty cool stuff.
`
`Where I work, we use the Direct Metal Laser Sintering process. It fuses metal powder layer
`
`by layer, and it's really impressive to see what kind of geometry is possible.
`
`Here's a video that gives the basic idea of how it works:
`
`How it Works: Direct Metal Laser Sintering (DMLS)
`
`a
`
`Of course, there are still limitations (just like there is with anything).
`
`For example, the surface finish out of the machine is generally pretty rough. Anything that
`
`needs to be highly precise or smooth will need to either be machined or postprocessed
`
`some other way.
`
`It's also an expensive process, so it's often cost-prohibitive for simpler parts.
`
`There are other metal AM technologies that aren't as expensive, but not quite as high
`
`performance. Binder jetting is one of these technologies - it can fairly quickly make
`
`complex geometry (including square internal corners) but they material will be a blend of
`
`metals that aren't the same as your typical billet.
`
`Ultimately, square corners are a great thing to avoid whenever possible! All of these
`
`19 of 22
`
`9/8/2020, 9:53 AM
`
`Page 19 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`processes have pros and cons - until we reverse engineer the Star Trek Replicator, that is.
`
`Do you have any questions? Or do you have a few tricks up your own sleeve on making
`
`square corners? Share them in the comments below!
`
`Jonathan Maes
`
`I've been working in manufacturing and repair for the past 14 years.
`
`My specialty is machining. I've managed a machine shop with
`
`multiaxis CNC machines for aerospace and medical prototyping
`
`and contract manufacturing. I also have done a lot of
`
`welding/fabrication, along with special processes. Now I run a
`
`consulting company to help others solve manufacturing problems.
`
`Recent Content
`
`20 of 22
`
`9/8/2020, 9:53 AM
`
`Page 20 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`there's typically a duty cycle mentioned in
`the technical specifications. Duty cycle for
`welding means the ...
`
`likes to make stuff. This is probably why
`multi process welders are so intriguing.
`Can they really do it all? Are ...
`
`CONTINUE READING
`
`CONTINUE READING
`
`HEY, l'M JONATHAN
`
`I've been involved in metalworking in its various forms for the past 14 years. On this
`website, I share some of the really cool things that I've learned while working in all kinds
`of different shops.
`
`LEGAL
`
`Make It From Metal is owned and operated by Maverick Manufacturing Solutions. Make
`It From Metal is a participant in the Amazon Services LLC Associates Program, an
`affiliate advertising program designed to provide a means for sites to earn advertising
`fees by advertising and linking to Amazon.com. Make It From Metal also participates in
`affiliate programs with Bluehost, Clickbank, CJ, ShareASale, and other sites. Make It
`From Metal is compensated for referring traffic and business to these companies.
`
`21 of 22
`
`9/8/2020, 9:53 AM
`
`Page 21 of 22
`
`
`
`Machining Square Inside Corners: Conquer the Nightmare! – Make It Fr...
`
`https://makeitfrommetal.com/machining-square-inside-corners-the-night...
`
`Want something made overseas?
`Let me help you get your parts sourced globally the easy way.
`Request a quote
`
`• Privacy PolicY-
`
`© 2020 Copyright Make it From Metal
`
`Exclusive Member of Mediavine Home
`
`22 of 22
`
`9/8/2020, 9:53 AM
`
`Page 22 of 22
`
`
Accessing this document will incur an additional charge of $.
After purchase, you can access this document again without charge.
Accept $ Charge
Still Working On It
This document is taking longer than usual to download. This can happen if we need to contact the court directly to obtain the document and their servers are running slowly.
Give it another minute or two to complete, and then try the refresh button.
A few More Minutes ... Still Working
It can take up to 5 minutes for us to download a document if the court servers are running slowly.
Thank you for your continued patience.
This document could not be displayed.
We could not find this document within its docket. Please go back to the docket page and check the link. If that does not work, go back to the docket and refresh it to pull the newest information.
Your account does not support viewing this document.
You need a Paid Account to view this document. Click here to change your account type.
Your account does not support viewing this document.
Set your membership
status to view this document.
With a Docket Alarm membership, you'll
get a whole lot more, including:
- Up-to-date information for this case.
- Email alerts whenever there is an update.
- Full text search for other cases.
- Get email alerts whenever a new case matches your search.
One Moment Please
The filing “” is large (MB) and is being downloaded.
Please refresh this page in a few minutes to see if the filing has been downloaded. The filing will also be emailed to you when the download completes.
Your document is on its way!
If you do not receive the document in five minutes, contact support at support@docketalarm.com.
Sealed Document
We are unable to display this document, it may be under a court ordered seal.
If you have proper credentials to access the file, you may proceed directly to the court's system using your government issued username and password.
Access Government Site
