Adam,,,your good self ,Pete from Edge prec.and Robin (too busy for RU-vid,these days😊) all give brilliant little snippets of machinist/toolmaker joy......thanks 👏👍🍻 P.s. not meaning to discredit all the other brilliant content you all create ,I must say 😊
I’m a manufacturing engineer in aerospace and I’ve seen every single one of your points regularly when reviewing designs. These little nuggets of industry knowledge that speed up fabrication and lower costs can literally make or break a company’s development program. Often times the designers never get to see (or want to see) how their design decisions impact the machinists. Your videos highlighting real world DFM examples are going to help so many engineers. Love watching them!
the best shop i ever worked at had the designers and the assemblers work in the same location, so the assemblers call the designer that made a mistake down to assembly and explain how to not fuck up again. Generally great place, the designing engineers had to work a month each in machining, programming and assembly within the first year of working there, that really helped with the amount of assemblers being annoyed at engineers XD
I agree with your comments "Often times the designers never get to see (or want to see) how their design decisions impact the machinists". What's even worse, is that they don't want to see how their design decisions impact the end user from an operability standpoint. I have seen manually operated valves placed in positions where no hand can get to them without pulling an engine. Or the infamous O2 sensor up next to the fire wall that requires as sub-frame and engine to be removed to get at it when changing the angle of the hole would have at least given someone a shot at getting it out. Thanks for the comment.
I work machines for a company that accepts a lot of aerospace works, and as machinists we have no way to talk to the designers. Even our workshop boss usually has no way to tell if a flat bottom hole really has to be flat or not
About press fit dowel pins in blind holes: There are press fit pins with a small flat on the cylinder and a threaded hole in the top (DIN 7979). You can thread a slide hammer into the end to get the pin back out, and the flat allows air into and out of the blind hole. Great little pins.
If you need ideas for some further topics where machinists and designers hiring them could use some common-ground education: Thin parts Surface finishes Edgebreaks/chamfers/deburring (I liked the aside into that on the cross-hole section) 3D surfacing Text and other engraving Keyways, gearing, cam surfaces; shafts, bushings and bores etc. Great videos, def looking forward to more.
Your last three design tips videos are a must watch for everyone entering the realm of designing parts for machining. I will share them with my employees. Thank you, and keep up the good work!
Solid gold, Adam! All of these practical design tips have been tremendously helpful. The fact that they seem so obvious when you explain them is a testament to how well you know and can teach your craft. Thank you for sharing your expertise.
I had a buddy that worked for ping the golf company. They owned a rare semi custom mill that could go down a hole and then drill a precise hole at a precise angle. They used it for making injection molds. Anyway they got a call from the DOD asking if they wanted some side work milling parts. The part was a magnesium billet that was basically finished. But it needed holes for the detonators. The hole was where explosives were cast for a tomahawk warhead. They didn't want 1 company doing all the work. And the last part was the most secret. They did a bunch of them right after desert storm to stock up. My buddy did maintenance on the equipment. Would have been something to see.
There's a blog called "engineeringdog" where he talks about how the maximum required number of threads for a full strength threaded joint is 6. The only reason I've seen to need more is if your tolerance stack up requires more certainty that you'll hit 6 threads minimum at LMC.
Yeah, their generally isn't a great deal to be gained with super deep threads. Sometimes its nice from a bill of materials standpoint, since a slightly deeper thread in a few places can allow a commonized fastener. not sure how much buying one fewer box of fasteners is worth in terms of aggravation though.
@@adamthemachinistif the assembly area is tight enough, that decision will be made. Also, with more manufacturing bottlenecks occurring, it has made my job of ordering parts post-shutdown a real challenge.
I learned in uni for engineering that there is no point having more than 8 engaged threads. Obviously that is just a rule of thumb and depending on the material and screw that might change slightly, but for metric fasteners thats not even 1.5xD.
I've been doing mechanical design (mostly of fixtures and jigs) for a few years now and am VERY happy to have came across your channel. Thanks for the effort you put into your vids. Keep 'em coming!
Thank you Adam, I've been a long time watcher and those DFM videos couldn't have been more timely! I'm an R&D engineer currently designing some quite complex prototype parts that I was about to send in for CNC machining with many of the issues you highlighted. After seeing this and your last two videos, I went back to my designs and modified several features according to your recommendations, and I now feel more confident that my parts will come out great and won't cause unnecessary headaches for the machinists. Thank you so much!!!
These design for manufacture and machining videos are so great! For the US engineers this is something not taught often enough. One rule of thumb I like is contextualizing things in diameter ratios. Like how close things are to edges, drill depth, and so on. I like to start with the golden ratio if I don't know where to start 1.6xD.
Great series, other ideas for future topics: tolerances and their effect on manufacturability and cost, choice of and use of standard fits, precision mating location of parts (don’t over constrain), design to make parts easy to inspect critical features with standard measurement techniques, design for process type or number of processes (design a part for mill work, lathe work, grinding, broaching etc.), designs that minimize number of setups, designs that facilitate setups, where is the line for what is machinable vs what could only be made with additive manufacturing, minimum order quantity to make difficult work holding or custom tooling viable (or what types of features are only practical to machine as a one off vs what types of features are only practical to machine in bulk quantities)
Excellent videos, They could easily be "machinist complains about designers" But they are nothing of the sort You give , friendly conscise definitions of issues and solutions in real world applications while highlighting cost and efficeincy benifits ..it's a win win .. An excellent teacher.
This is the exact content I've been looking for for about 2 years now. Thank you for producing this video, the information is much more thorough and understandable coming directly from a machinist. More content on DFM would be greatly appreciated!
I've been designing and building machines for about 14 years and I try to consume as much DFM content as I can, to save machine shops from having headaches when I send them RFQ's. But I still picked up several new-to-me tips from your latest vids. Please keep making these! They are fantastic. For any other engineers who are trying to not be a P.I.T.A. for the shops they work with-- the Send Cut Send youtube channel has put out some similar types of videos, on DFM for sheet metal fabrication.
This is incredible stuff. I'm a mechanical engineering student, only spent about a year working as a design engineer through internships so far, but I've sent parts with some of these design problems to machine shops already that I'm sure were quoted at a much higher price than they needed to be as a result. I'm really happy to have found these now instead of thirty years into my career. Keep 'em coming!!
I love this! This is really interesting and really helpful since I’m currently starting my own company and am trying to get parts made. Idea for next video. Tolerances in parts for slide or press fit. I have an application where a brass part is supposed to slide back and forth in a stainless part. (Or should it be stainless part sliding in stainless part. Still figuring out all the information, on metals working with each other. Galvanic corrosion, anodising for protection, temperature differences winter / summer… It’s a lot!
I believe these videos are best, sooner or later this channel will boom with viewers as there are many designers out there who need to know these stuff & no university is teaching this
Absolute wealth of info, thank you putting it out there! The deep drilling points brought back some pain for me. Aerospace designers are something else.
Subscribed within 2 minutes. I'm only a hobby guy, but, wow, so much information presented in such a relaxed manner. I feel a binge session coming up. Thank you!!
Valuable information, clearly conveyed, great format. To have this constellation of design rules at the forefront of one's design process is good for everyone. Well done Adam.
Great infomational video. Should be taught in university, too. Had fallen in many of this pitholes as a beginner engineer and got a lot of calls from machine shops like "Do you really need that thread go all the way through the part?"🤔😅
One of my customers has a tendency to want countersinked holes with the edge touching another feature. On the 3d model sure theres a "wall" of material but in reality theres nothing. You cant even put a dimensional tolerance on it. Same goes for your example of threaded holes as we usually get the 3d models with holesizes recommended for the specified thread; Like an Ø5 hole showed for an M6 tap. Part looks fine with the hole - but there isnt any wall left once the thread is done 🙃 I could be pedantic and just make the part per the drawing/3D model - and sometimes that works out fine - except when it doesnt and I "should have known better". Ive watched several of these videos from you and they are VERY interesting. I see myself facing a lot of these issues on the daily myself
That is great man, thanks!! We need more cost-saving tips like that! I remember designing a pulley which I lightened throug many slots and then a friend suggested me to do many holes instead to make it cheaper to manufacture.
Adam these last couple videos are amazing! I see many engineers fall into bad practices because shops make parts with sub-optimal design and then assume it was good DFM because the machinist/shop did not complain. Content like this perfectly explains the simple steps to optimize part design for CNC.
Hi Adam, I machined lots of parts myself but by now I mostly design parts for others to make. There is still a lot to learn from your manufacturability design videosas they cover more advanced details - most others cover the simplest things as internal corners. Please continue that series for us :). One thing that often bugs me is the tradeoff between making one complicated part or two simle parts that are connected. Often, I would make two parts if I had to machine them, but when ordering at machineshops the complex parts are surprisingly often cheaper. Would be nice to learn more about that.
Interesting thing you say. I think it depends on the situation. With mastercam, what uses to be complex single parts are not so complex nowadays. It's sometimes only one setup with a lot of tools available in the shop. Two parts require two setups at least. And I often have a problem where it's easier to hold one bigger part than two small parts, no matter simple or not. We will sometimes machine two parts back to back, using one to hold the other one, then cut them in half, just to get around the "holding the simple part" situation
Fantastic series!! I appreciate the time and effort you put into each video you make. An idea for a future expansion of the series, you could go over the selection of different metals and what typical applications they have (I know this is extremely broad). Or perhaps a discussion on different conditions of materials and how that affects machinists. For example, hardened tool steels vs annealed, non-ferrous metals (1/2 hard vs full hard or T2/T4/T6 etc), solution hardened stainless and their different conditions, etc.
Awesome content Adam, loving these. I know you mentioned the hardmilling strategies being a little niche, but I'm sure you'd make it interesting. Should you ever tire of making parts you're an natural educator.
*Design Considerations for Machining Holes: A Machinist's Perspective* * *0:00** Holemaking as a Superpower:* Emphasizes the importance of understanding holemaking tooling and techniques for efficient and cost-effective part design. * *0:40** Length-to-Diameter Ratio Limits:* For standard CNC machining, the practical limit for hole depth is around 30-40 times the diameter. Beyond that, specialized techniques like gun drilling are required. * *1:28** Machine Head Height Limitations:* Highlights the importance of considering the machine's Z-axis travel and tool holder length when designing deep holes, especially those that can't be accessed from both sides. * *2:56** Drill Deflection Issues:* Drilling into or out of angled surfaces can cause deflection, reduced hole quality, and excessive burrs. Suggests using counterbores or modifying the part design to avoid these issues. * *6:07** Small Hole Proximity Challenges:* Drilling small holes close to other features risks the drill wandering and damaging the part. Recommends increasing the distance between features if possible. * *9:12** Drill Tip Angle Discrepancies:* Explains how the increasingly common use of blunt drill tips (130-150 degrees) can impact hole clearances and fluid passageways, especially in intersecting holes. * *11:23** Step Drills for Complex Holes:* Recommends considering step drills for applications with numerous holes of varying diameters and angles, as they can be a cost-effective solution. * *12:33** Tapping Depth Limits:* Typical tapping depth in a machine is limited to around three times the diameter due to chip evacuation constraints. * *13:25** Strategies for Minimizing Thread Depth:* Encourages designers to explore alternative design approaches, such as using shorter threads with back-drilled holes, to reduce machining complexity. * *15:36** Threaded Holes Near Walls:* Warns against placing threaded holes too close to part walls, as the threads may break through. Recommends modeling threads to the minor diameter for clarity. * *17:13** Drill Depth for Threaded Holes:* Explains the need for extra drill depth to accommodate the chamfered portion of taps. Suggests using thread milling for precise thread depth control in shallow holes. * *19:17** Flat Bottom Holes for Die Springs:* Highlights the importance of accurately machining flat bottom holes for die spring applications. Recommends using specialized flat bottom drills and a center relief design for optimal results. * *21:34** Counterbore Considerations:* Discusses the challenges of deep counterbores and suggests using piloted counterboring tools. * *24:21** Limitations of Flat Head Screws:* Discourages the use of flat head screws due to their susceptibility to stripping, especially in corrosive environments. Recommends using alternative head styles like socket head cap screws whenever possible. * *28:43** Reamer Chamfer and Clearance:* Explains that reamers require a starting chamfer and cannot ream into a flat bottom. Recommends leaving a gap between the reamer's end and the bottom of the hole. * *29:44** Through Hole Advantages for Dowel Pins:* Suggests using through holes for slip-fit dowel pins or for creating knock-out holes for press-fit dowel pins. [From Comments] One commenter mentioned using press-fit pins with a flat and threaded hole for easier removal from blind holes. * *30:15** Avoid Press-Fitting Dowels into Blind Holes:* Strongly advises against press-fitting dowels into blind holes due to the difficulty of removal. I used gemini-1.5-pro-exp-0801 to summarize the transcript. Cost (if I didn't use the free tier): $0.09 Input tokens: 24013 Output tokens: 842
When you mentioned the major diameter of threads breaking out of the hole I had flashbacks to all the times I see that on gun slides cut for red dots and a footprint that doesn't *quite* fit onto the slide.
Very nice content, thanks! I do agree on 100% of it! As a CAM-programmer and machinist these things are an everyday hassle for me 🙄 It REALLY bugs me that all designers and CAD-tools still are using 118° drills 😤
Really nice video with some good bits and pieces! To remove dowel pins from (non fragile) parts. Clamp them into a strong cross-hatch serrated bench vise and use a rubber hammer on the part.
Loved the note on flat head screws. When I was just getting into designing and had no real machining experience I liked to use them because I thought they looked nice. Now with a lot more experience in both those areas I would need to have a very very good reason to ever use a flat head, and I am not shy about asking if a part someone else designed can be modified to replace them with a SHCS.
For keeping all fasteners the same length I prefer to use longer fasteners everywhere. I can avoid the long counterbores, and instead counterdrill the tapped holes to keep the thread depth reasonable. If the tap shank is a lot bigger than the major diameter this may not be practical, but I've done it with 10-32 (~M5) and it worked well. My reasoning for favoring the longer fasteners is that it should better resist loosening from vibration. (I want at least a couple diameters between head and thread engagement.) It also reduces angular misalignment when the holes are slightly out of position. It's also a lot easier to clean the head out on a fastener that's near flush than one down a hole. The counterdrill trick is also helpful to reduce the torment of flat-head screw overconstraint, but the conical seats will still fight one another to some degree.
On the topic of blind dowel holes, there are collet dowel pin pullers that can be a life saver for pulling dowel pins out. I purchased a set from Fastenal that had both metric and SAE collets for the normal smaller sizes. It was probably one of the best tools I have bought as far as saving the day. I do agree though, dowels should not be blind of at all possible. I often spec a drill size smaller pilot for a punch access, but it does mean having access to the back of the part.
Don’t forget machining countersinks for those larger flat head screws. In a pinch I have surfaced some with a ball nose end mill because I didn’t have tooling to countersink those holes.
with dowels in a blind hole: in my apprenticeship we had hardened dowels with a little notch lengthwise and a threaded hole in the end, so it wouldnt trap heat when you pressfit it in, and you could pull it out with a pullhammer on that thread. Through holes are the easier solution for assembly, but if its neccessary it might be worth it. I remember a part where i had to pre-drill, then flat bottom drill and then ream with a special reamer with coolant coming out the tip to flush the chips out the top so i could ream down to about 0.5mm clearance of the flat hole bottom. Was a pain, but i got half a day off for not breaking tools or scrapping parts on that one-off XD
You are a gem. We in the community really appreciate your insights into design and machining. Knowledge about the interface between two disciplines is valuable as it takes years of seeing poor designs from a lack of understanding about the principles of machining. Would there be a better solution for the ejector plate example than using shoulder bolts?
I really appreciate this series, there's nuance conveyed in the long format discussion that doesn't come through otherwise. Your note on step drills applies to reamers too. We had to ream a pair of aileron bushings to final size in-situ, which were different diameters for a stepped pin. The guys initially had a lot of difficulty keeping the holes coaxial during the reaming process. A custom ground reamer with two pilot diameters and two cutting diameters cost less than the two individual reamers did. I'm really like to know whether modelling chamfers on tapped holes adds value. We call out hole prep for helicoils per NASM33537, which details the specific hole geometry. Are chamfers in the model useful for CAM programming?
I'm just a guy with hopes of one day having a little hobby shop, and making things for fun. I watch your videos just to learn for a hobby I want to get into, so take my suggestions with that in mind, since someone who could readily apply any information on your videos might not necessarily be interested in what I am curious about. Coming from the hobby side of RU-vid machinist I watch, I was really captivated by what you call hard milling. I was under the impression that you would mill your parts first, then harden them, and you would need to calculate for how much your part deforms. I knew you could use a surface grinder on hardened parts, so you leave some material to be ground, right? But what about other features that couldn't be ground? For example, a threaded hole, or a pocket with 4 walls and so on. You're the only machinist that I have found on RU-vid has gone into detail about processes I didn't even know existed to be honest, so that's why I'm suggesting for a "hard milling for dummies" video. In any case I'll be here for the next one because I'm always learning, and you explain things very well.
The threaded hole being to close to the the wall being something you see regularly I would find concerning. I've been doing mechanical design for a decade now, and I would not allow that to pass drawing checking. Even in steel, a properly torqued bolt will start distorting the surrounding material. Worse yet is if it's parts that see any vibration. We avoid less then 0.5D wall thickness around the major diameter. Edit to add: if you're doing a dowel into a blind hole, use a hollow/ring dowel. Air can escape during install and usually can be grabbed with a needle nose pliers without much hassle.
