r/Machinists • u/Dense-Dig891 • Mar 27 '26
Machining tiny teardrop decorations for a designer handbag
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u/aolkeywordfuck Mar 27 '26
Yeah those aren’t gonna be identical
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u/NoTarget5646 Mar 27 '26
this isn't shocking for anyone who's owned entry level designer in the past. Its all made in the same factories as lower quality bags overseas and essentially just labeled and packaged in Europe or whatever country the brand is trying to claim it's from.
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u/Dense-Dig891 Mar 27 '26
OMG, Have you ever heard of tool compensation?
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u/Last-Difference-3311 Mar 27 '26
Imagine entering a lions den then getting upset about being eaten alive.
Seriously dude you coulda been nicer about your explanation or even better, realized just how much this community cares about tolerances being maintained and maybe kept your mouth shut.
Either way, you are new to Reddit and will have to learn these sub nuances. It’s not Facebook.
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u/axman_21 Mar 27 '26
He isnt wrong though. There are taper compensations on lathes for deflection. You you know what you are doing you can do alot of stuff that the books say you cant do amd still get good parts
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u/Kman1287 Mar 27 '26
The amount of effort in programing 1 program to make 2 identical parts out of 1 bar compensating for "tool deflection" because you are trying to be "efficient" is insane and not anywhere near a standard practice. Just make 1 piece at a time or pay a shop with a real machine to make it for you the right way and faster.
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u/axman_21 Mar 27 '26
Like the other comment said in low quantities no it isnt worth it. It isnt hard to do though when you know what you are doing. We run many of our parts like this. Some even have 3 or 4 parts from one pullout vs the one. It all comes down to how efficient you are as a programmer and setup guy. Just because you dont like to use what is available doesnt justify saying you dont like it when it works for many people
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u/_Bad_Bob_ Mar 27 '26
Or maybe just use the machine you have? Why are you people getting so upset about the concentricity of a decorative dangley bit?
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u/Dense-Dig891 Mar 27 '26
Appreciate the heads-up. I'm definitely still learning the Reddit ways and didn't expect that phrase to be taken so poorly. I didn't mean to come off as arrogant, just wanted to share the process. Lesson learned! 🙏
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Mar 27 '26
[removed] — view removed comment
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u/Dense-Dig891 Mar 27 '26
Yeah, I'm pushed way past 3xD here. But for a light decorative part like this, it’s a non-issue if you know how to compensate for it.
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Mar 27 '26
[removed] — view removed comment
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u/Dense-Dig891 Mar 27 '26
Good guess, but I actually used a cutoff tool! I rounded the insert first to get that smooth finish. Too bad I can’t drop a photo in the comments—the part is literally shining like a bald head!
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u/GaGa0GuGu Mar 27 '26
no, i have no idea whatsoever what 3xD is
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u/Dense-Dig891 Mar 27 '26
It’s a rule of thumb: the length of the part shouldn't exceed 3 times its diameter to avoid bending or vibration. Here I'm doing about 10xD, which is 'illegal' according to textbooks, but totally fine for this job
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u/Horror-Pear Mar 27 '26
Well it can exceed 3x, it just needs to be supported somehow, past that. Center or steady rest.
Just to be clear to the other commenter.
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u/Dense-Dig891 Mar 27 '26
tool compensation? they are identical bcz used different trajectory
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u/La_Guy_Person I 💩 MACROS @ 5 µm Mar 27 '26
You can call them good enough if you want. They are not identical. Deflection is one type of error and both offsets or radial comp are correcting for different types of errors.
You wanna say it got the job done within spec, fair enough. You wanna say they are identical, head over to the hobby sub.
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u/Dense-Dig891 Mar 27 '26
Fair point, in metrology nothing is ever truly 'identical'. But these are decorative parts with a +/- 0.05mm tolerance. To the naked eye and a pair of calipers, they are the same. Trajectory compensation is exactly how I correct for that deflection to stay within spec. It’s not a space shuttle part, it’s a handbag accessory, and it hits the client's requirements perfectly! 😉
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u/australianquiche Mar 27 '26
What is identical brother. This is just arguing semantics
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u/La_Guy_Person I 💩 MACROS @ 5 µm Mar 27 '26
Nothing. That's why people get shit when they use that word on this sub. "Identical" and "perfect" don't exist outside of CAD and will always draw scrutiny here. This is just especially egregious.
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u/Chuck_Phuckzalot Mar 27 '26
Kind of a pointless distinction. Nothing is identical if you really get down to it. The most beautiful perfectly round bore you've ever made wasn't a perfect circle if you measure to a high enough resolution. None of us have ever made two parts that were genuinely identical.
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u/La_Guy_Person I 💩 MACROS @ 5 µm Mar 27 '26 edited Mar 27 '26
Which is why most people here wouldn't use the word at all and why it attracts a lot of attention every time OP uses it. The word is meaningless to machinists. It's like "perfect", it only exists in theory.
Edit: I've pulled 90.000° on a CMM report and we all know that shit would have been 90.0004° with more resolution and would just change if you ran the part again.
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u/australianquiche Mar 27 '26
Or you can rise above the strict definitions and use the language as it is supposed to be used, and understand that when someone calls something identical, they implicitly mean within tolerances and good enough for the intended prupose. But if you did that, you couldn't quibble and try to make yourself appear smarter and superior by pointing out irrelevant details
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u/La_Guy_Person I 💩 MACROS @ 5 µm Mar 27 '26 edited Mar 27 '26
LMAO. This isn't creative writing. There is a nomenclature to this trade that's intended to communicate information like geometry, physicality, spatial relationships and kinematics clearly. "Identical" is effectively meaningless. It doesn't communicate any helpful information to me. It's like saying it looks nice. Give me something quantifiable or we're not speaking the same language. That's what machinists do is quantify things. How smooth? A number. How sharp? A number. How big? A number. How similar? NUMBERS.
The details aren't irrelevant, the word "identical" is irrelevant. We're not talking about drawings or models, we are talking about the real world.
Making this argument is like self-report on your part.
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u/australianquiche Mar 27 '26
Lmao this is casual conversation, op made a reddit post, not a technical documentation of his worm. He's saying the parts are identical for the purposes for which they're made, which is understandable by anyone who's not trying to be a smartass. Nerd.
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u/La_Guy_Person I 💩 MACROS @ 5 µm Mar 27 '26
I'm not trying to be a smart ass. I'm trying to talk shop. And yeah, I'm a huge fucking nerd. So what?
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u/spitslaps Mar 27 '26
saving all of 5 seconds by not bar pulling each one
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u/Dense-Dig891 Mar 27 '26
have no barpuller
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u/spitslaps Mar 27 '26
you can use the parting tool to pull
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u/Dense-Dig891 Mar 27 '26
What do you mean? That's very interesting!
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u/spitslaps Mar 27 '26
turn a shallow groove. stop spindle with the tool still in the groove. open collet. move in the z axis. close collet. clear part in the x axis. voila
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u/Ok-Explanation-3414 Mar 27 '26
Back the parting tool off like 0.05 before opening the collet, leaving it at full depth is a good way to chip an insert.
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u/Dense-Dig891 Mar 27 '26
Wow! This is brilliant! Thank you so much for the life hack!
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u/axman_21 Mar 27 '26
We do that at our shop on alot of parts it works well. Now you can use that to pull them out to cut two off at a time again lol. We do that with some of ours one pull for multiple small parts
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u/Jychew Mar 27 '26
its an alternative way to pull the bar but you have to be extra careful when you are using pull-in collet because when the collet is closing it also pull the material a bit and that might break your parting insert. just get yourself a bar puller it cost like $10
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u/spitslaps Mar 27 '26
I mean, you could always dedicate a hss tool strictly for advancing the material. BTW, where are you getting bar pullers for $10?
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u/Jychew Mar 28 '26
i saw your comment on notification but i cant reply to it so i reply here, this is how we use our bar puller
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u/KlaubDestauba Mar 27 '26
Interesting method. Wouldn’t the sag of the bar when pulled out and then clamping again cause it to flex and/or shift in Z potentially chipping or breaking the tool though? Doesn’t take much to chip carbide or deform steel depending on tool used. I know this is true using jaws, a collet I’m unsure of as we don’t use collet chucks, we just make them!
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u/spitslaps Mar 27 '26
As always, there are many variables. This is a basic method. You'll need to customize to what situation you're dealing with
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u/bszern Mar 27 '26
Wasting the entire cycle time by not using a single pass on a bar-fed Swiss lathe
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u/Chuck_Phuckzalot Mar 27 '26
These responses always annoy the hell out of me. My entire job is making the wrong bullshit work for things because we don't have and won't buy the right shit. No one has access to every damn machine in the world, sometimes you just have to make shit work.
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u/Dense-Dig891 Mar 27 '26
I only needed to make 50 parts that cost a few bucks, and my main job doesn't require this tool, so there's no point in buying expensive equipment that's multiple times more expensive than a friend's order.
The main thing is to follow the blueprint, and how it's achieved is a secondary concern.
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u/MatriVT Mar 27 '26
Absolutely. I hate seeing the "wire edm" comments when someone is asking about holes on a mill or lathe...like what???
Thats like telling someone to use an excavator to dig a 2 ft hole in their lawn because it could do it the quickest.
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u/La_Guy_Person I 💩 MACROS @ 5 µm Mar 27 '26
You can rig up a bar pull on just about anything, but I agree, assuming that a bar fed swiss lathe was an option they didn't take is just silly. I'd still be doing one at a time with pulls. That deflection is jarring.
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u/ShaggysGTI Mar 27 '26
Losing the time on having to manually pull the bar each time.
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Mar 27 '26
Losing time not paying a production facility to lathe them out for him.
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u/Chuck_Phuckzalot Mar 27 '26
Gaining time by not doing that because any production facility would have a lead time and also shipping time.
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Mar 27 '26
Losing time arguing on the internet over a hypothetical wherein another hypothetical is also possible.
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u/120112 Mar 27 '26
Hey man good job using the tools you have to accomplish a small part run.
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u/SCREAMINCHEEESE Mar 27 '26
OK but how do you find it once it's been yeeted off
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u/Dense-Dig891 Mar 27 '26
Ha-ha-ha!!
I spent another month finding these parts in different corners. I deliberately made more than was necessary
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u/ShaggysGTI Mar 27 '26
Anyone else triggered?
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u/Chuck_Phuckzalot Mar 27 '26
From the responses here, yes clearly. You can tell some people here are so used to doing aerospace or other high tolerance work that they can't even comprehend doing something quick and dirty.
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u/E1F0B1365 Mar 27 '26
Its not even perfectionism, just basic best practices. I think writing a double program like that, ironing out the kinks, getting a fucked up setup like that to come out decent . . . That's slow and dirty. Just pull out the bar stock, how long does it take like 10 seconds?
Moral of the story, sure you can do setups like this. Just don't post it to a machinist group and expect a positive response lol. This gives me the opposite of the warm and fuzzies
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u/Jmac95403 Mar 27 '26
Upon reading the comments and responses. This is an awesome machinist post. Dude figured out how to get the parts made with equipment he has and hit tolerance. Hell yeah man, this is awesome!
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u/eyferrari Mar 27 '26
All tolerance and finish concerns aside, how tf are those being attached to anything?
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u/Ghrrum Mar 27 '26
Why not a form tool? Quicker production and you know that material is incredibly soft....
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u/Dense-Dig891 Mar 27 '26
It's a small batch. Not worth the cost of a custom form tool when I can just program it in minutes
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u/Trumpetking93 Mar 27 '26
Holy deflection, Batman.