Hacklinger gauge

Construction and repair of Classical Guitar and related instruments
SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Mon Jul 31, 2017 2:01 am

jim watts wrote:
Sun Jul 30, 2017 8:51 pm
Here's a link to a video describing it's calibration and use.
http://www.luth.org/images/web_extras/a ... lin_01.mp4
Jim, Thanks for the video. Are the tubing pieces from a telescoping antenna?
As for calibration, don't you have to calibrate the readings to various thickness wood pieces first to make a look up table?

jim watts
Posts: 283
Joined: Mon Sep 05, 2011 7:19 pm
Location: Los Alamos, NM, USA

Re: Hacklinger gauge

Post by jim watts » Tue Aug 01, 2017 3:58 am

The brass tubing can be found at many hardware stores and hobby shops. There are no look up tables you read the thickness straight from the gauge.

SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Tue Aug 01, 2017 6:42 pm

jim watts wrote:
Tue Aug 01, 2017 3:58 am
The brass tubing can be found at many hardware stores and hobby shops. There are no look up tables you read the thickness straight from the gauge.
Hi Jim, if you read the thickness straight from the gauge, that would imply magnetic force is linear throughout the useful range of the device. I thought magnetic force is inversely proportional to distance squared?

jim watts
Posts: 283
Joined: Mon Sep 05, 2011 7:19 pm
Location: Los Alamos, NM, USA

Re: Hacklinger gauge

Post by jim watts » Tue Aug 01, 2017 7:17 pm

Magnetic force does fall off as you say. This is a balanced magnetic system which uses a smaller magnet in between two larger magnetic fields. This basically makes it a linear system. Seems to work.

SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Tue Aug 01, 2017 7:27 pm

It works, that's what counts! I suppose the 2 larger outer magnets should be equal in size and strength? I like the thumbscrew idea with a dial indicator to measure the distance between clicks. It seems more precise and repeatable than using a sliding wedge.

Paul Micheletti
Amateur luthier
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Re: Hacklinger gauge

Post by Paul Micheletti » Tue Aug 01, 2017 8:22 pm

What a great tool. I think I need one in my future. That video was very helpful.

jim watts
Posts: 283
Joined: Mon Sep 05, 2011 7:19 pm
Location: Los Alamos, NM, USA

Re: Hacklinger gauge

Post by jim watts » Tue Aug 01, 2017 9:19 pm

SteveL123 wrote:
Tue Aug 01, 2017 7:27 pm
It works, that's what counts! I suppose the 2 larger outer magnets should be equal in size and strength? I like the thumbscrew idea with a dial indicator to measure the distance between clicks. It seems more precise and repeatable than using a sliding wedge.
Steve,
That is exactly right, the two outer magnets need to be matched. I imagine the more precise the fields are in strength to one another the more accurate you'll be.

SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Fri Aug 04, 2017 3:04 pm

jim watts wrote:
Tue Aug 01, 2017 9:19 pm
SteveL123 wrote:
Tue Aug 01, 2017 7:27 pm
It works, that's what counts! I suppose the 2 larger outer magnets should be equal in size and strength? I like the thumbscrew idea with a dial indicator to measure the distance between clicks. It seems more precise and repeatable than using a sliding wedge.
Steve,
That is exactly right, the two outer magnets need to be matched. I imagine the more precise the fields are in strength to one another the more accurate you'll be.
Thanks Jim! One thing not obvious in the video ( I have not looked at the Luthier #109 yet) is that I think there has to be a stopper in the main tube to prevent the clicker magnet from being permanently attached to the puller magnet. Is that so?

Also, how important is it while measuring top thickness to have the gauge perfectly perpendicular to the guitar top? How much of an error will occur if not perpendicular?

When I have time, I will make one from ideas in the video. I am not going to copy the design but have other ideas. I already have a digital dial indicator from a project on setting injection pump timing. I think I have some blocks of Delrin or other plastics that I have floating around that I can use to build the whole thing out of and not use tubing which will be less top heavy/ lower center of gravity / easier to hold.

jim watts
Posts: 283
Joined: Mon Sep 05, 2011 7:19 pm
Location: Los Alamos, NM, USA

Re: Hacklinger gauge

Post by jim watts » Sat Aug 05, 2017 4:30 am

Steve, you are correct there is an inner chamber for the clicker magnet.
I haven't checked for errors regarding perpendicularity, but I'm pretty sure it would have an impact.
This design was a collaboration between Mike Doolin and Alain Bieber. I'd really recommend getting the back issue to anyone interested in making one as it spells everything out pretty well.

SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Sat Aug 05, 2017 3:15 pm

jim watts wrote:
Sat Aug 05, 2017 4:30 am
Steve, you are correct there is an inner chamber for the clicker magnet.
I haven't checked for errors regarding perpendicularity, but I'm pretty sure it would have an impact.
This design was a collaboration between Mike Doolin and Alain Bieber. I'd really recommend getting the back issue to anyone interested in making one as it spells everything out pretty well.
Thanks for the names of the collaborators! With them, I was able to find this http://www.mimf.com/library/A_prototype ... -2011.html post from Alain Bieber which seems like it was written during the development phase before the version in the calibration video you posted.

simonm
Amateur luthier
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Location: Germany, Würzburg.

Re: Hacklinger gauge

Post by simonm » Sat Aug 05, 2017 3:25 pm

SteveL123 wrote:
Sat Aug 05, 2017 3:15 pm

Thanks for the names of the collaborators! With them, I was able to find this http://www.mimf.com/library/A_prototype ... -2011.html post from Alain Bieber which seems like it was development work before the version in the calibration video you posted.
Same link I posted last week on the first page in this thread. :mrgreen:

SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Sat Aug 05, 2017 3:31 pm

simonm wrote:
Sat Aug 05, 2017 3:25 pm
SteveL123 wrote:
Sat Aug 05, 2017 3:15 pm

Thanks for the names of the collaborators! With them, I was able to find this http://www.mimf.com/library/A_prototype ... -2011.html post from Alain Bieber which seems like it was development work before the version in the calibration video you posted.
Same link I posted last week on the first page in this thread. :mrgreen:
Yes, I see now you have edited your post to add the link, which I did not see until now. :mrgreen:
Nevertheless, it's an excellent thread for those who want to experiment/ build a gauge. :wink: :wink:

SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Wed Aug 09, 2017 9:25 pm

Jim,

I finished mine and checked the accuracy with various thickness wood pieces (dimensions checked with a digital vernier). Initial results indicate it is accurate to about 0.05 mm. I'll have to do more tests to be sure.

I made mine out of a block of Delrin AF that I have laying around. I used 3 mm diameter for the clicker magnet and 6 mm diameter for the other 2, all sphere magnets.

If anyone plan on using sphere magnets, it is important to line up the N/S poles of the puller magnet before attaching it to the screw. I failed to do that the first go around and just epoxied it on without checking the poles and was wondering why the measurements were way off! After lining up the poles before epoxying the magnet, it is a lot more accurate.
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Last edited by SteveL123 on Thu Aug 10, 2017 2:33 pm, edited 1 time in total.

SteveL123
Posts: 365
Joined: Thu Feb 09, 2017 5:05 pm

Re: Hacklinger gauge

Post by SteveL123 » Thu Aug 10, 2017 1:38 am

I checked the calibration using all the wood gauge blocks ranging from 1.4 mm to 5 mm. Each piece was checked for thickness with a digital vernier before calibration of the Hacklinger gauge. I'd say I can get accuracy of 0.03 to 0.05 mm if I turn the wheel slowly and not overshoot it. In the pic above, the wood piece is 2.5 mm and the gauge measured 2.47 mm- not bad!

One problem after trying it out on a guitar. The 3 mm diameter clicker magnet is too small and drops the internal magnet too easily when maneuvering the gauge around the top due to insufficient attractive force. I just ordered some 4 and 5 mm magnets. Will wait and see if that will do it.

For anyone who going to build one here's a tip: You want the clicker magnet's travel distance as short as possible and still audible for best accuracy.

jim watts
Posts: 283
Joined: Mon Sep 05, 2011 7:19 pm
Location: Los Alamos, NM, USA

Re: Hacklinger gauge

Post by jim watts » Thu Aug 10, 2017 3:40 am

Glad you got one built Steve.

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