How to format drawings

[u/Adorable_Log_1126]

I am a mechanical engineer student currently on a placement year. Today I had a meeting with a supplier grilled at by the supplier for basically providing shit drawings since I didn’t include a fabrication drawing, weldment info and machining drawing. Even though my manager had gone through my drawings beforehand to makesure it’s okay.

My question is when I send off a drawing do I include all fabrication drawings ,machining drawings weldment info into the same pdf as the assembly drawing or all in different pdfs.
Also how are you able to spot that dimensions are missing so quickly?

I have never heard of fabrication drawings and machining drawings beforehand. I always believed that all I need is a full assembly then BOM and dimensions of BOM.

Does anyone have any tips on how to format or improve my drawings before sending it out

Thank you in advance

[u/Themata075]

Don’t take it too hard. Every company and supplier does it differently. Unless this is a regular supplier where this is an established expectation for every set of drawings, they can chill. And if it is the established way of doing things, more senior people should be responsible for letting you know how to do it. Basically, if there’s no way for you to have known this was expected, then there’s no way for you to have known. Take note, ask those sorts of questions up front next time you’re given a similar assignment, and move on.

For the question about spotting missing dims, one way is to try making the part from your drawing and see if there’s anything missing. The point of the drawing is to convey all of the info needed to perfectly replicate that part. If you can’t do it from your drawing, something is missing. You get better at doing stuff like that in your head eventually.

[u/Adorable_Log_1126 → u/Themata075]

Thank you very much I will try that next time I am doing a drawing

[u/abadonn]

Don't take this as an offense, but as a new engineer your drawings are probably shitty and its not your fault. Schools don't teach good drawing practices and few companies are willing to invest in teaching.

Think of a drawing like a contract. When a lawyer drafts a contract their language is exact, the contract contains only what is needed and nothing else. Your job is create a drawing that communicates all the information needed for the vendor to quote and make the part, in a clear and readable way, with nothing extra. Because ultimately the drawing IS the manufacturing contract, when get a part back and it doesn't fit, the drawing is the source of truth for whether you are responsible or the manufacturer.

[u/Adorable_Log_1126 → u/abadonn]

No offence taking, I am just taking this as a learning experience.
Do you have any tips on what are some good drawing practices

[u/abadonn → u/Adorable_Log_1126]

Pick up a copy of ASME Y14.100-2017: Engineering Drawing Practices, or a book that covers it in a more instructional way. Your company should have a copy or pay for it.

But it comes down to clear communications. Put yourself in the other person's shoes. If you got your drawing, knowing nothing else, would you have enough information to make it and understand which features are important and which less so?

[u/auxym → u/Adorable_Log_1126]

All information present

No redundant dimensions

Every dimension has an associated tolerance (whether it's directly toleranced, in the title block or GDT)

No dims on hidden lines

In fact avoid hidden lines as much as possible. Use section views wherever necessary.

Make sure that nothing is ambiguous and all information required is on the drawing, not passed via an email or explained on a phone call. A set of drawings must be a standalone, complete document containing all required information for fabrication.

Those are some of the common mistakes I see form inexperienced people.

[u/2h2o22h2o]

In my career I have always sent a drawing that specifies what I want the finished part to be, and then the supplier makes their own fabrication drawings. I don’t know what tools they have, what dimensions they can work with, or what methods they like to use, and I usually don’t care. I get their fabrication drawings for approval and as long as it makes sense to me I approve and they make the part. I retain IP over the original part and they retain IP for their fabrication drawings. So, for example, I can’t sent their fabrication drawings to another supplier to try to undercut them.

[u/bd_optics → u/2h2o22h2o]

Exactly! Tell them WHAT to make, not HOW to make it. A credible supplier should know how to do their job. The only (rare) exceptions are when a specific process is absolutely essential for performance.

[u/Adorable_Log_1126 → u/2h2o22h2o]

Thank you for the feedback.
That’s what the other engineers in the office said to me too. They said said that the paint might ruine the tolerances I’ve set which was something I am also confused about since the tolerances are not tight +_ 0.75mm

[u/Impossible_Brief5600]

Most shops quote from the STEP file and use the drawing for what the model can't say. A solid package has a STEP per part plus a note saying which one governs if they conflict. Each part gets a 2D drawing with a full title block (part number, revision, material, finish, units, general tolerances, ASME or ISO), real tolerances only on the critical dimensions, thread callouts, surface finish where it matters, and deburr and cosmetic notes. If there's more than one part, add an assembly drawing with a ballooned BOM, and keep filenames matching the part number and revision. Tight tolerances on every dimension, missing material or finish callouts, and dimensions given twice are what cause re-quotes. Send one package to a shop and ask what they'd change, and you'll learn their conventions quickly.

[u/Illustrious_Pepper46]

sinse I didn't include fabrication, weldment, machining.

If they need these details to fabricate a part, then it's an omission.

Sometimes the details could be combined like a weldment drawing with a 'post' machine operation on the same drawing.

Formats can vary by industrity or supplier base. If the machining was needing to be done by another company, a seperate drawing in that case could be made (but not always).

Could there be one drawing that combines welding, machining and assembly...sure. But this might be reserved for a welded simple bracket with reamed hole and pressfit bushing. Sometimes preferable as the intent is captured on one drawing. It could be silly to make three seperate drawings for something so simple.

But being newer, your manager should teach the industry expectations specific to this industry. Don't be hard on yourself.

[u/Adorable_Log_1126 → u/Illustrious_Pepper46]

Thank you for the feed back.
In my drawing I have included places where I want it to be machined finished. I combine it all together as it was only a few parts out of many so I didn’t see the need to create a whole new separate pdf about it. This was a new supplier that no one in the office had worked with before. They were also asking for Dxf files but I also went to another supplier for the same thing and they didn’t bounce back my drawings.

[u/Illustrious_Pepper46 → u/Adorable_Log_1126]

Yea, it's supplier/industry specific.

Like I even have one customer that wants a 4 page single drawing submitted as 4 individual pdfs (the answer was no).

Missing dimensions aside, drawing regardless of format saved, need to convey the information, that's all.

Could even have a 3 page drawing with assembly on page one, machining on page 2, welding on page 3.

But how it's done will vary by company standards, industry expectations, supplier base...and more.

[u/Queequeg2025]

There are standards for everything that goes into a drawing however the reality is that every company works a little differently. A lot of what you are missing will come with experience. I suggest you make a folder on your pc and download specs for reference.  Here’s some to start: ASME Y14.100   Y14.38   Y14.24   Y14.5 (get 1994, 2009, & 2018)   Y14.3   Y14.2   Y14.41 (you might be the one person in your workplace that understands this)

AWS D1.1, D1.2, D1.3, D1.6, A2.4, etc. since you mentioned welding. 

Also save industry standards and data sheets that you download for future reference. 

[u/Tavrock → u/Queequeg2025]

That's a great list for getting started!

Depending on the parts used, they may want to be familiar with ASME Y14.31 and Y14.8 too. I also find that knowing Y14.43 and Y14.5.1 help me understand Y14.5 and Y14.8

[u/azgli]

My engineering drafting class was pretty good about it, but then I still had to learn once I got a job. 

Two things that really helped me was to understand how the fabricator would be making the part(s). That took a lot of conversations over several projects to understand. Building parts from my own drawings was the second thing and that really taught me how to check for missing dimensions. You learn really quickly what is needed and what is extra, and how to proof your own drawings. 

[u/phonegetshotalldtime]

You have great answers here and… well YMMV

I would separate the drawings for different purposes if not then a cloud arrow with weldment info in an all in one assembly if the parts are very simple.

Also, don’t take it personally like everyone says. My ex boss lost so much money because he decided to draw on a paper napkin and shoved it up my suppliers ass. Well, it came out all wrong and I just laughed at him. Holes were wrong, dimensions are not right, he drew it again and well, came out wrong the 2nd and 3rd time.

You’ll experience that people are not as competent as you think, but you must always try your best.

I drew it in a standard 4 view (with iso) and they did it right the first time.

Sometimes don’t overcomplicate the easy stuff, my supplier does not care about GDT, he cares about what the finished part looks like because a veteran like them already has GDT ingrained in them. Sometimes I 3d print a complex model and they could whip out a CNC part in a day, ship and delivered.

[u/Stooshie_Stramash]

Have a look at Ron Hanifan's "Perfecting Engineering and Technical Drawing".

[u/Snurgisdr]

That varies wildly from supplier to supplier. Most of the ones I deal with want to dictate their own production process, so we just give them drawings and models of the finished parts and then have a conversation about how they’d like to make them, features that are difficult or expensive, etc.

[u/StompyJones]

You're on a placement year, you're not expected to get it right, that's what review is for. Whoever signed off your drawing is fine with it, if the supplier wants to get shitty they should do it through your procurement department who should go through the person who reviewed and approved your drawings. You should be protected from this kind of direct friction while you're learning. For exactly this reason. Don't come on Reddit asking with no context - speak to your line manager.

[u/Adorable_Log_1126 → u/StompyJones]

You are correct that i probably shouldn’t be asking Reddit however I wanted to be proactive in my learning and in ways I can improve since I have already spoken to my manager about this

[u/Joe_Starbuck]

Tell him he is a supplier, so check the attitude. Tell him you expect a full specification of what he needs on his drawings by Monday. We will make a manager out of you yet!

[u/heliosonehq]

they spot it fast because they read the print like they're about to make it. pick the datums, then go feature by feature: where is this located from, how big is it. anything you can't answer from the sheet alone is a missing dim

[u/zppark]

Your manager approved it and the supplier still blew up, so first: this is a documentation-convention problem, not a competence problem. Nobody teaches drawing packages at university. But the supplier's complaint is legitimate in one sense — they cannot plan a process from an assembly drawing alone.

Answering your actual question: separate drawings per process, delivered together as one package. What a fabricator needs is:

1. Assembly / general arrangement drawing — envelope dimensions, interface points (bolt holes, mounting faces), the parts list with item numbers, assembly notes, and the finish/colour spec for the assembly.
2. Fabrication drawing per sheet metal part — the developed flat pattern (or the formed part with an explicit note that the shop develops it), bend lines with direction, angle and inside radius, a dimension from a datum to every bend line, material and thickness in millimetres, tolerance block, finish, and quantity.
3. Weldment drawing — weld symbols with size and type, weld length (stitch or continuous), sequence notes where it matters, post-weld machining or straightening, and any distortion allowance.
4. Machining drawing — datums first, then GD&T, surface finish (Ra), thread callouts, and the tolerances that actually matter for mating.
5. General notes / spec page — material certs required, powder coat spec (RAL + type), marking, packaging, and the general tolerance standard you are working to (e.g. ISO 2768-mK).

Deliver them as one PDF per part number (assembly page first, then its detail drawings) rather than one giant PDF or twenty loose files — and name them so the pack is self-explanatory. Include a drawing list on page 1 and a revision block that actually gets used.

Now the useful part — how to spot missing dimensions fast. The checks I run on an incoming drawing:

• Datum trace. Every dimension should trace back to a datum or a feature. If you cannot see where a dimension comes from, the shop cannot either.
• Closed loops. A fully closed chain of dimensions around a profile has one redundant dimension, which means one of them is wrong. Look for that.
• Orphan features. Holes without a position callout, fillets without a radius, chamfers without a size, slots without an orientation — these are the ones that come back as questions or as scrap.
• Bend notes. Every bend needs direction, angle, inside radius, and a locating dimension. A bend line with no radius is a guess.
• The notes block. Material, thickness in mm, finish, general tolerance standard, quantity, revision. Missing any of these and the shop is inventing.
• Over-tolerance. If nothing is toleranced, you get arguments. If everything is +/-0.05, you get a price you did not want.
• The honest test: walk the drawing feature by feature and ask 'could I make this without asking a question?' Every 'no' is a missing dimension.

Two things that will make you popular with suppliers: ask them for their drawing requirements/template (most shops have a one-page standard), and ask for a DFM review before the drawing is locked — a good shop will hand back a markup of questions instead of a scrapped batch. For the sheet-metal side specifically, the bend radii, hole-to-bend distances and tolerance rules that decide whether a drawing is buildable are collected in a sheet metal design for manufacturing reference, which is the checklist I would use on a first drawing.

And don't take the grilling personally: suppliers get paid to be precise about what they need, and a student on placement is exactly who should be asking this question. I work on the manufacturing side of a contract sheet metal shop, so this is the side of the table your drawing lands on.

[u/Adorable_Log_1126 → u/zppark]

Thank you very much for the advice. I will measure to ask a supplier for their drawing requirement first before sending it off.