Measuring beyond the decimal place for distances >600mm

You can ask questions here about Trevor and Gerard's exciting new book on Luthiery.

Moderators: kiwigeo, Jeremy D

Post Reply
User avatar
lamanoditrento
Blackwood
Posts: 242
Joined: Thu May 05, 2016 9:50 am

Measuring beyond the decimal place for distances >600mm

Post by lamanoditrento » Mon Sep 17, 2018 7:42 am

I have bought a 610mm engineer's straight edge that I thought was guaranteed to be accurate to +/- 0.025mm. But that turns out to be for its straightness, not its length.

So now I am wondering the best way to measure my straight edge to an accuracy for setting up a full nut/saddle compensated setup?
Trent

User avatar
Trevor Gore
Blackwood
Posts: 1379
Joined: Mon Jun 20, 2011 8:11 pm

Re: Measuring beyond the decimal place for distances >600mm

Post by Trevor Gore » Mon Sep 17, 2018 9:45 am

I use a piece of 1/8" by 1/2" brass rod (Bunnings) that I machined to length on a milling machine with a good digital readout. It turned out to be 0.2mm short, but I just zero my calipers at +.2 to take care of that.

If I was doing it without heavy machinery, I would likely just make a number of scratches approx. 150mm apart on the material, deep enough to locate the tips of my 150mm calipers. (The Mitutoyo ones that I've used for years open to 153mm). Step out until the distances sum to exactly 600mm and file to that using a shooting board to keep the end square.

There are likely better ways...

Andos
Sassafras
Posts: 41
Joined: Tue Apr 25, 2017 4:12 pm
Location: Taranaki

Re: Measuring beyond the decimal place for distances >600mm

Post by Andos » Tue Sep 18, 2018 2:53 am

Here is a 650mm Vernier caliper https://m.ebay.com/itm/STARRETT-NO-123M ... 2731788098.

The other way is to take the straight edge to a machine shop and give them the length and tolerance to machine it down to.


User avatar
lamanoditrento
Blackwood
Posts: 242
Joined: Thu May 05, 2016 9:50 am

Re: Measuring beyond the decimal place for distances >600mm

Post by lamanoditrento » Tue Sep 18, 2018 9:37 am

Great thanks, Trevor
Trent

User avatar
kiwigeo
Admin
Posts: 9533
Joined: Sat Sep 29, 2007 5:57 pm
Location: Adelaide, Sth Australia

Re: Measuring beyond the decimal place for distances >600mm

Post by kiwigeo » Wed Sep 19, 2018 4:41 pm

If you can't afford a micrometer these are far cheaper :mrgreen:
index.jpg
index.jpg (5.67 KiB) Viewed 448 times
Martin

Post Reply

Who is online

Users browsing this forum: No registered users and 6 guests