A Visual Guide for Diagnosing Common Manufacturing Defects

Published on 06/15/2025Product Idea Validation (Non-SaaS)

Okay, I'll use the previous analysis as a template for spotting a new opportunity from the Reddit data.

The user shared a photo comparing a well-made and poorly-made part, asking for the cause of the differences. This kind of curiosity about the 'why' behind manufacturing quality is pretty common among engineers, machinists, hobbyists, and those involved in quality control or procurement. The comments highlight numerous potential causes: "Worn tooling. Insufficient workholding. Incorrect speed/feed. Rattletrap Soviet machine. Inadequate finishing," "cranked the feed up to decrease machine time," "skilled labor issue," "blunt" vs. "sharp" tooling.

This presents an opportunity for an information resource: a "Visual Guide to Common Machining & Manufacturing Defects: Causes and Prevention."

This could be:

  1. A comprehensive online database/website: Featuring high-resolution images of various defects (e.g., poor surface finish, chatter marks, burrs, dimensional inaccuracies, material deformation) across different materials and machining processes (milling, turning, grinding, etc.). Each defect entry would include:

    • Multiple visual examples.
    • A list of common causes (e.g., tool wear, incorrect speeds/feeds, improper workholding, machine condition, operator error, material issues).
    • Diagnostic tips (how to confirm the cause).
    • Recommended corrective and preventive actions.
    • Perhaps short video clips demonstrating the defect formation or correction.
  2. A durable, laminated workshop poster series: Each poster focusing on a specific type of defect or machining process, offering a quick visual reference.

  3. A detailed physical or e-book: Serving as a more in-depth reference and training manual.

Expected Benefits:

  • For Manufacturing Professionals & Hobbyists: A quick and reliable diagnostic tool to identify the root cause of manufacturing issues, leading to faster problem-solving, reduced scrap/rework, and improved part quality.
  • For Students & Trainees: An invaluable learning resource to understand the practical consequences of process parameter deviations and tooling issues.
  • For Quality Control Personnel: A standardized reference for identifying and classifying defects.
  • For Designers: Better understanding of how design choices can impact manufacturability and potential defects.
  • Revenue Stream: Sales from the book/ebook, subscriptions for premium website content/features, or sales of the poster series.
  • Community Building: A website could host a forum for users to share their own examples and solutions, further enriching the database.

This resource would directly address the user's question ("What would cause this?") on a broader scale, providing a much-needed practical tool for anyone involved in making or inspecting physical products.

Origin Reddit Post

r/machinists

What would cause this?

Posted by u/BTMedicrn06/15/2025
My question is other than the obvious quality control issue. What would cause the difference between these. These are from Romanian firearms. The one on the right is from the height of commun

Top Comments

u/igetmywaterfrombeer
Shoulda gone with a Cugir.
u/Western_Ladder_3593
Nyet! Rifle is fine!
u/AM-64
Tons of different things not to mention it's almost a guarantee both of these were produced on manual equipment.
u/StepEquivalent7828
All the skilled labor went to the West
u/monkeysareeverywhere
A Fadal would cause this.
u/BTMedicrn
Romania wasn’t at war, but it definitely looks like it
u/dan0o
The worse one was made in a preparation era, looks made no difference as long as it worked. And they just pumped em out of production, well that and the above Edit: typo
u/Droidy934
These faces were cut with a slab mill ...on the right when it was sharp on the left when it was blunt.
u/iamwhiskerbiscuit
Same story as always when a company gets bought out and turns to shit. The new owners cared more about cutting costs than upholding quality standards and focused more on quantity than quality
u/K_Labs
Oh I know the answer to this one! Minimum wage causes poor surface finish.
u/Western_Ladder_3593
Nyet! Rifle is fine!
u/jrhan762
How much time you got? Worn tooling. Insufficient workholding. Incorrect speed/feed. Rattletrap Soviet machine. Inadequate finishing. The list is endless.
u/Terrible_Ice_1616
Poor tooling and or machine tools. My guess is the ones on the right were made with the same machine and tools as the ones on the left, just 40 years later
u/StepEquivalent7828
All the skilled labor went to the West
u/monkeysareeverywhere
A Fadal would cause this.
u/Podsully
Let’s see the trunnion markings👀
u/BTMedicrn
😂
u/CCCCA6
I’m interested as to the dimensions. To me it looks like before and after hand working or finishing.
u/BTMedicrn
Everyone can tell it’s a sadu lol
u/BTMedicrn
That was what I was thinking, it’s a non critical part, but even the critical parts are rough. Probably as rough as could be made and still get a functional product.
u/jrhan762
My guess would be they cranked the feed up to decrease machine time and reduced finishing to reduce overall effort and cost. That kind of thing almost always happens over the life of military
u/SkilletTrooper
This is it.
u/LeageofMagic
The one on the left seems to be made of wood. Hope this helps.
u/markwesti
Parts on the left are war finish .
u/Terrible_Ice_1616
Poor tooling and or machine tools. My guess is the ones on the right were made with the same machine and tools as the ones on the left, just 40 years later
u/Podsully
😂😂😂 I just built a beautiful one out I’m sure you seen the post on r/ak47
u/NonoscillatoryVirga
I’d guess 2 suppliers. One on the right has a decent machine and proper tools to go with it. One on the left is using marbles for spindle ball bearings and tooling that is way beyond needing
u/BTMedicrn
I guess that was my biggest question, was it more worn tooling or a skilled labor issue. Probably a mixture I would guess. Interested in what this sub thought about it.
u/BTMedicrn
Have less interesting
u/AnIndustrialEngineer
If you’re operating a manual machine tool and you have no money, the company has no money for replacement tooling, the economy is falling apart in your country, and you’re drunk at work then
u/Trivi_13
The one on the left looks partially made. It might have slipped through quality control. 
u/jrhan762
How much time you got? Worn tooling. Insufficient workholding. Incorrect speed/feed. Rattletrap Soviet machine. Inadequate finishing. The list is endless.
u/igetmywaterfrombeer
Shoulda gone with a Cugir.
u/NonoscillatoryVirga
I’d guess 2 suppliers. One on the right has a decent machine and proper tools to go with it. One on the left is using marbles for spindle ball bearings and tooling that is way beyond needing
u/CCCCA6
I’m interested as to the dimensions. To me it looks like before and after hand working or finishing.
u/dan0o
The worse one was made in a preparation era, looks made no difference as long as it worked. And they just pumped em out of production, well that and the above Edit: typo
u/Podsully
Let’s see the trunnion markings👀
u/BTMedicrn
😂
u/Droidy934
These faces were cut with a slab mill ...on the right when it was sharp on the left when it was blunt.
u/BTMedicrn
I guess that was my biggest question, was it more worn tooling or a skilled labor issue. Probably a mixture I would guess. Interested in what this sub thought about it.
u/Trivi_13
The one on the left looks partially made. It might have slipped through quality control. 
u/BTMedicrn
Everyone can tell it’s a sadu lol
u/AM-64
Tons of different things not to mention it's almost a guarantee both of these were produced on manual equipment.
u/markwesti
Parts on the left are war finish .
u/Podsully
😂😂😂 I just built a beautiful one out I’m sure you seen the post on r/ak47
u/RepulsiveBaseball0
All it’s doing is gouging. Shorter tool increase axial cut DOC. Looks to be skipping along not biting, then the runnout resolves the issue causing a large cut and gouging. The swirls look lik
u/jrhan762
My guess would be they cranked the feed up to decrease machine time and reduced finishing to reduce overall effort and cost. That kind of thing almost always happens over the life of military
u/LeageofMagic
The one on the left seems to be made of wood. Hope this helps.
u/AnIndustrialEngineer
If you’re operating a manual machine tool and you have no money, the company has no money for replacement tooling, the economy is falling apart in your country, and you’re drunk at work then
u/SkilletTrooper
This is it.

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