Help needed with understanding accuracy in measuring tools. I want to go straight :-)

[Boyan Silyavski]

I've got both and the bevelled edge is far more versatile and the one used most.

You cannot angle the straight edge like you show because your straight reference edge is lost because it's bending and will just follow the curvature of the surface. The reference edge is only meant to be used in one direction and must be 90deg to surface your checking any tilt/bend and error is introduced.

Thanks, i get it now. Ok, i will look for a beveled one.

Now recapitulating everything it seems that the Maun even if not ultra accurate is made from carbon steel opposed to all other mentioned. And at theit web site i saw it was beveled.

So i send a couple of emails.

-To Maun, to ask them if its hardened carbon steel, cause at their web they don't say so, say steel. No carbon at any place. All sellers say carbon. We will see.
-To Measuresop which Greeny suggested, cause here they have some beveled straight edges which look quite cheap , so i asked about the accuracy.
-To Precison tools to see if they will ship to Spain this and if this can serve as a straight edge, cause it states tolerance 40micrometers
- to ebay member who is selling the Igaging 36 inch to ask if he could check straightness before sending. yes, back here, as the brand ones a very expensive.

Will see what happens.

[mekanik]

Hi M8
This is only my opinion and i am sure others may disagree but i would forget about the Maun straight edge, i couldn't see any thickness quoted so it's more than likely a bendy one,the other bevel edge rule is quoted as steel and galvanised and i didn't see any tolerance/flatness quoted, i would stick with the magic numbers DIN 874/2 a parallel straight edge of reasonable thickness should be fine you can see the smallest of gap by placing a light behind the straight edge.
Take no notice of e-bay sellers the DIN 874/2 rules will be checked under controlled temperature conditions in a tool room using some rather expensive gear. a box for your precision straight edge is a must buy.
Hope that helps, i am now awaiting the flack.
Mike

[JAZZCNC]

Hope that helps, i am now awaiting the flack.
Mike

No flack from me I'm 100% in agreement. My bevelled edge is 5/8" thick came from Vickers tank factory and would cost more than a small car today and weighs nearly has much. It also has stamped on it working temperature range it's accurate at and it's quite narrow, it will also be fair way from calibrated by now so I treat it with kid gloves and it's away in it's wooden case ASAP.

You get what you pay for.!!

[Boyan Silyavski]

Thanks a lot for the info!

The Maun edge if happens to be from hardened steel/ still no info/ , could be good for drawing straight lines
Here is the drawing from their web:



I will stay with the magic number.
Will fiddle until the end of the week and if nothing more interesting jumps, will buy from Germany. They answered me and told me that the scale also is a straight edge. Yes, i wanted beveled, scale and hardened and inox but ...$$$.

[Boyan Silyavski]

2 more questions before i push the button:

-Wood box i will do. But how you keep it in the wood box? Horizontal? And if horizontal, laying on its thin side or its flat side? Cause i will make the wood box if it comes without any

-I live near the seaside so everything rusts. The product i use is called Barricade rust protection for firearms. I treat all machines with it. Its oily and dries quickly in ultra thin film.
Is it ok? Stainless beveled edges are out of my league/1m i mean/

[mekanik]

Hi M8
All our straight edges in the stores where i used to work (VSEL)were laid horizontal on dexion shelving, so not flat by any means. so yes lay it on its flat side. The only problem i can see is in the shipping of your precision gauge if it is not already in a substantial box.
Mike

[Boyan Silyavski]

Thanks for the info. They would ship it together with flat wood piece for protection, i believe.

You were right. I get what i pay for :-)

The Igaging digital protractors came. Hughghghgh. Checked against my new supersquares and even against my ordinary squares, when zeroed on flatish surface and then measured 90 degrees, they show 89.75 or 90.25, depends if you take the measures from inside or outside. Ha ha ha. for 11 euros each, that's all folks. However i played around with them and noticed that the electronics and the dro discs are extremely accurate. The problem comes because they did not drill the axle hole on the right place.

I thought of throwing them to the bin. Then decided to think deeper. Measured the plates, each is perfect. Then what? Opened them to 180 degrees so both corners touch a flat plane. Zeroed. Closed so again both corners touch a flat plane. Spot on 180 degrees.

So, i invented a cure. Open them flat to 180 degrees until they are dead flat. Zero. Close them untill shows 180. One edge is not at the same plane compared to the other. Scrape it and repeat until they are spot on. In other words file untill the bolt is where it should be- at the center.


PS. I couldn't do it. At least for educational purpose opened it to see whats making it tick. Now i get it. Wasnt the problem in the steel axle hole placement. Encoder disc attached to the axle which enters a cavity, like a bearing entering its place. So , plastic in plastic. That means the screws and the plastic construction of the device is the problem. The encoder disc not being in perfect center makes the problem. And as its not a tight fit, it could never be centered.
Bottom line: You get what you pay for