standard callout for "stock size" in drawings
standard callout for "stock size" in drawings
(OP)
Hi
What is correct way of specifying stock size for machining print. For example if holes need to be drilled on a 1/4" thick plate.
- Reference the dimension in parenthesis "()"
For example - (.25)/(.250) - depending on level of tolerance looking for stock.
OR
- calling out "STOCK" after the dimension?
For example - .25 STOCK / .250 STOCK
thank you very much,
pavvpk
What is correct way of specifying stock size for machining print. For example if holes need to be drilled on a 1/4" thick plate.
- Reference the dimension in parenthesis "()"
For example - (.25)/(.250) - depending on level of tolerance looking for stock.
OR
- calling out "STOCK" after the dimension?
For example - .25 STOCK / .250 STOCK
thank you very much,
pavvpk





RE: standard callout for "stock size" in drawings
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: standard callout for "stock size" in drawings
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: standard callout for "stock size" in drawings
Leave it up to the machinist to use available sizes. Don't tie them down to a certain size.
If you call out a .25 plate, and he/she uses .38 plate, does it really matter?
Chris, CSWA
SolidWorks '15
SolidWorks Legion
RE: standard callout for "stock size" in drawings
Any size tolerance usually gets controlled by the parts list or bill of materials where the relevant material standard would be included.
"Know the rules well, so you can break them effectively."
-Dalai Lama XIV
RE: standard callout for "stock size" in drawings
In any case, the thickness should be a firm callout and there must be traceability to tolerances for thickness, flatness, et al. The number of decimal places on stock dimensions have no effect on tolerances for stock material characteristics.
RE: standard callout for "stock size" in drawings
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II
RE: standard callout for "stock size" in drawings
Be aware, while the thickness spec on 'stock' material may be ok, it often has bad flatness - especially if at some point it was on a roll of material.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: standard callout for "stock size" in drawings
I don't call out stock size. I call out the dimension I want, and I specify the tolerance, parallelism, and flatness. I try to ensure that my numbers are achievable by the stock size.
Let the machinist figure out how to do .250±.030. There must be a way!
--
JHG
RE: standard callout for "stock size" in drawings
Few colleagues pointed out about - flatness, tolerance issues etc if we specify that thickness dimension as "STOCK" or reference one. But if that thickness dimension needs have precise tolerance/flatness control or surface finish, I wouldn't leave it as stock or reference. I would call out required tolerance specification so that machinist will machine that part to obtain required control.If any stock plate is available with required tolerance or flatness control, I would call that plate purchasing info in the print so that would guide people to procure same or equivalent material - to avoid unnecessary machining cost.
The question here relates to a stock material(with .25 or .250 thickness)& which doesn't require controlled features - either flatness or surface finish..etc.
Looks like ASME Y14.5 doesn't suggest to use or not to use "STOCK" or "(reference)" methods.
Rule 1 only says each dimension should have tolerance (or govern by general note) except ones that says "STOCK" or referenced ones or MIN/MAX...etc.
So can we take it as - use of "STOCK" or "STK" is approved by ASME Y14.5?
Also, I would like to know if you run into any issues by using "STOCK" or "STK" for stock size?
thank you,
pavvpk
RE: standard callout for "stock size" in drawings
Here, we treat it as a REF dimension (that rule was established before I came here and I have had to reason to challenge it).
The popularity of dovetail vices has rendered "STK" dimensions a PITA for anyone hired to make parts. Yes, the part can be made from 1-1/2" thk bar stock, for example, but they'd rather start with 1-5/8 or 1-3/4 so they can machine a dovetail into it and cut on all 5 remaining sides while it's in a dovetail vice.
I also wouldn't rely on the flatness, straightness, roughness tolerances of stock material. Depending on your supplier, you may or may not be getting material in such condition. Yes, it might have started that way when it was fresh off the rollers from the mill/foundry, but you don't know what you're going to be delivered. It's sometimes cheaper to just get something 1/8 or 1/4" thicker and machine it down than to pay a higher price for stress-relieved flat stock at the 'finish' thickness. Depends on the part of course.
Long story short- there's a lot of variables at play that you don't see if you're not familiar with buying material and making parts from it. IMO it's best, as a designer, not to create expectations of what stock material to use unless it's critical to your design. You're not doing anyone any favor by suggesting they use 1" x 1/2" bar stock. They will look at your part and decide what stock to start with. They likely know much better than you do, based upon their supply chain and in-house capabilities.
*edit* Fixed a couple grammatical issues
_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5
RE: standard callout for "stock size" in drawings
Chris, CSWA
SolidWorks '15
SolidWorks Legion
RE: standard callout for "stock size" in drawings
You're confusing general rule #1 with the first fundamental rule. The rule you mentioned is the first of about 13 or 14 fundamental rules. General rule #1 is one of 4. General rule number one states that form must be perfect when a regular feature of size is at it's MMC. By identifying a thickness as STK, you are releasing that requirement and the form is then subject to mill standards. I think JNieman nailed it perfectly. Every time I've seen a thickness identified as STK it's the engineers attempt to be helpful. He/she also thinks they are saving money by not requiring material to be faced down. The real world scenario is that most of the time, facing surfaces to get them flat and parallel makes other operations go faster and makes for a better looking--and sometimes more accurate--part.
John Acosta, GDTP Senior Level
Manufacturing Engineering Tech
SSG, U.S. Army
Taji, Iraq OIF II
RE: standard callout for "stock size" in drawings
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: standard callout for "stock size" in drawings
2JL
RE: standard callout for "stock size" in drawings
Let's break problem into pieces:
1. STK is legitimate abbreviation for "stock" (I don't have ASME on me, but MIL STD says so). No arguing here.
2. Sometimes specifying stock does more harm than good. I remember working in a shop making simple small parts about 1/2 x 1 x 3 inches in size. One week we would cut them from 1/2 x 1 stock, and another 1 x 3. Clearly it 'd be better not to mention stock anywhere.
3. Specifying reference stock size may be helpful with non-machined flat plates and sheet metal.
4. Surface of cold-finished steel is actually strengthened by the process applied to it (rolling, drawing. etc.), so it may beneficial to show on the drawing that certain size should not be machined, but fabricator should make an effort and find stock of proper size.
Just 2 cents
"For every expert there is an equal and opposite expert"
Arthur C. Clarke Profiles of the future
RE: standard callout for "stock size" in drawings
RE: standard callout for "stock size" in drawings
".250 C/U" means:
1- Start with a 1/4" stock piece and machine it until it's cleaned up without exceeding LMC/LMB of the 3-place tolerance.
2- Start with 1/4" stock and clean it up until it's machined on both sides, regardless of resultant thickness.
3- Same as above but one side only.
4- Doesn't matter what you started with or what the C/U means, that is a .250 three-place dimension and you have to be within tolerance.
5- "I don't care that much, just gimme a plate that's reasonably flat and smooth, without mill scale/bark and somewhere close to 1/4" or so" (designer)
Such ambiguity is why I say "STK" is over-used and should only be used when it's clear, and means something, though I believe it to be rare.
The other issue is that I doubt many engineers/designers understand that stock size is a NOMINAL dimension. Example: If we order tool steel it will come in .030" oversize as it's assumed we intend to make it clean up exactly at the nominal dim after squaring/grinding/whatever. The dimension may be right-on or intentionally over-sized or under-sized depending on manufacturing process; whether it's a rolled shape, extruded shape, cast plate, etc. I expect that the vast majority of designers/engineers writing "STK" on their drawing have no idea that "3/8 STK" may come in at a wide variety of actual sizes depending on the /type/ of material being ordered.
_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5
RE: standard callout for "stock size" in drawings
You could not specify STK or C/U and then expect a machinist to hold +/-.005"
At least I wouldn't anyway!
RE: standard callout for "stock size" in drawings
Diego
RE: standard callout for "stock size" in drawings
"MAXIMUM PLATE MAXIMUM AS ROLLED PLATE THICKNESS SHALL NOT EXCEED 3.00
THICKNESS INCHES."
A quick glance through the drawing seems to indicate the part will not exceed 2.25 at it's thickest.
That leaves things open but yet... controlled. I thought that may be a solution for some circumstances this topic addresses.
_________________________________________
NX8.0, Solidworks 2014, AutoCAD, Enovia V5