This contraption?

[Crimson0087]

Y'all use pen or pencil with this contraption? I hate to use pen when getting close to final thickness but the pencil gets thinner as it writes and I have to keep readjusting.

[Davide Sora]

Pencil mandatory, it doesn't wear out that quickly!

Perhaps you use it too tender, a HB or at most B (which according to wikipedia should correspond to #2 and #1 in the USA https://it.wikipedia.org/wiki/Scala_di_durezza_delle_matite ) should be soft enough to be visible and not wear out too quickly.

 

[Don Noon]

I don't use the pencils, but I know some of the artist's pencils have graphite that is extra-large diameter... usually the softer varieties.  I'd probably use that, and leave the tips very dull.

[ernym]

I was lucky when I enrolled ITT Tech's drafting program mechanical drafting with pencils was still part of the curriculum. Eventually the school sold off all the mechanical drafting equipment and bought computers and AutoCAD software, so I was taught both ways to draw.

I think a lead holder might work in those contour jigs. The lead comes in different grades of hardness and you wouldn't have to keep adjusting as often, just push the cap and the lead slides up and down. I'm  still partial to them over wooden pencils.

 

 

 

[Greg Sigworth]

1 hour ago, Davide Sora said:

Pencil mandatory, it doesn't wear out that quickly!

Perhaps you use it too tender, a HB or at most B (which according to wikipedia should correspond to #2 and #1 in the USA https://it.wikipedia.org/wiki/Scala_di_durezza_delle_matite ) should be soft enough to be visible and not wear out too quickly.

 

David: I would like to make gages like yours. How does the screw hold the pencil in place and how does backing off the screw loosen it for adjustment? Thanks for showing these.

[baroquecello]

I'm trying to imagine what use this tool has, can someone enlighten me?

[DiemViolins]

3 hours ago, baroquecello said:

I'm trying to imagine what use this tool has, can someone enlighten me?

Using these tools with different spacings can visualise how the isohypses are. Any irregularity is seen:

 

[Davide Sora]

10 hours ago, Greg Sigworth said:

David: I would like to make gages like yours. How does the screw hold the pencil in place and how does backing off the screw loosen it for adjustment? Thanks for showing these.

It is very simple, there is a cut in the wood and the screw (with nut) tightens this cut blocking the pencil, there is no contact between the screw and the pencil. The nut is held in place with cyanoacrylate glue to keep it from rotating, the screw is tightened with a screwdriver and the pencil must be moved manually when the screw is released. Traditional yellow pencils should be HB (#2)

[Davide Sora]

3 hours ago, baroquecello said:

I'm trying to imagine what use this tool has, can someone enlighten me?

You can see how they work here:

https://youtu.be/CtHE1PYlmmc?t=480

Having more than one serves to always have fixed measurements and to be able to repeat the same isolines several times during construction, without having to change the measurement each time as would be the case if you had only one.

 

[HoGo]

My thickness caliper is made out of plywood and has removable dial and the hole matches standard roundpencil snugly. I use B or HB pencil with rather blunt rounded tip to avoid digging into soft grain of spruce (and avoid moving it against grain/uphill). Even without setscrew it works great to mark topo map on outside during final refining of arch. Any bump in arching is greatly exagerrated by the distortion of map lines. It's quite good alternative to low candle light :-).

Too thick or blunt tip of pencil would distort the marking on steeper arch like near c bouts.

Here is the only pic I could find where you can still see traces of the marks (those are mandolin tops and I marked them before I hollowed the inside)

 

[carl1961]

13 hours ago, Davide Sora said:

Pencil mandatory, it doesn't wear out that quickly!

Perhaps you use it too tender, a HB or at most B (which according to wikipedia should correspond to #2 and #1 in the USA https://it.wikipedia.org/wiki/Scala_di_durezza_delle_matite ) should be soft enough to be visible and not wear out too quickly.

 

Thanks David for your work and pictures, I will do some and 3D print them.

[HoGo]

3D printed pencils won't work :-)

Wouldn't it be much faster just to take three blocks of wood and glue together just like Davide did? You could cobble one together in 15 minutes from some maple offcuts and few drops of CA glue.

[carl1961]

10 minutes ago, HoGo said:

3D printed pencils won't work :-)

Wouldn't it be much faster just to take three blocks of wood and glue together just like Davide did? You could cobble one together in 15 minutes from some maple offcuts and few drops of CA glue.

very true , but my thought , once done any one could print them like I did here for the betts 1704 violin https://www.thingiverse.com/thing:5557507

[HoGo]

Nice work there. I managed to download the Betts CT while it was online but never got to even viewing the file.

Regarding the gages, I think anyone competent enough to have any use for them should be able to make it in 15 minutes.

[carl1961]

7 minutes ago, HoGo said:

Nice work there. I managed to download the Betts CT while it was online but never got to even viewing the file.

Regarding the gages, I think anyone competent enough to have any use for them should be able to make it in 15 minutes.

do you have a copy of the actual cat scan? I lost my copy, all i have is the stl that was posted here

[FiddleDoug]

While that "contraption" is fine for some things, it doesn't allow you to reach around thicker things (like edges) to mark thinner things. It also doesn't work well on curves. You can buy marking calipers, but here's one that I made from a cheap caliper. The caliper has spring to it, and usually just gets adjusted to a more closed position by the adjusting nut. I added a couple of extra nuts on the inside to limit how far it closes. I silver soldered the fittings for the pencil and opposing post on the caliper ends, and a couple of finger pad washers to the sides to press on. You adjust the pencil to the right gap using measured thickness gauges, or a calibrated wedge. Works great!

 

[Crawforde]

This is brilliant. Thanks 

how much play is there once it’s squeezed shut to measure/ mark? 

[Don Noon]

The pencil clamping hole/slot/screw in Davide's design I have found to be less than ideal.  You can get a wide clamping range (of pencil diameters) with less screw tightening by adding another hole and extending the slot like shown below.  Extending the slot in the upper part would be a bit of a pain... I'd use a bandsaw and slot the upper AND lower parts.  The lower slot won't affect function, just aesthetics.

[Davide Sora]

11 minutes ago, Don Noon said:

The pencil clamping hole/slot/screw in Davide's design I have found to be less than ideal.  You can get a wide clamping range (of pencil diameters) with less screw tightening by adding another hole and extending the slot like shown below.  Extending the slot in the upper part would be a bit of a pain... I'd use a bandsaw and slot the upper AND lower parts.  The lower slot won't affect function, just aesthetics.

I bow to Don's more appropriate engineering, but it's not exactly essential, and making an extra hole is more time-consuming.

...but I have to take you back for the efficiency of the processing phases, to saw the cut only in the upper part only is sufficient to do it before gluing the three pieces together, as well as making the holes at the same time.

One thing I definitely could have made better is to make the cut wider, I've made them a little tight, and if the pencil isn't the right diameter, they don't tighten well.

[Mark Norfleet]

1 minute ago, Davide Sora said:

I bow to Don's more appropriate engineering, but it's not exactly essential, and making an extra hole is more time-consuming.

As nicely trimming and chamfering the ends of the pencils would also be… 

[Davide Sora]

2 minutes ago, Mark Norfleet said:

As nicely trimming and chamfering the ends of the pencils would also be… 

Del Gesù would never have done that

[Davide Sora]

1 hour ago, FiddleDoug said:

While that "contraption" is fine for some things, it doesn't allow you to reach around thicker things (like edges) to mark thinner things. It also doesn't work well on curves. You can buy marking calipers, but here's one that I made from a cheap caliper. The caliper has spring to it, and usually just gets adjusted to a more closed position by the adjusting nut. I added a couple of extra nuts on the inside to limit how far it closes. I silver soldered the fittings for the pencil and opposing post on the caliper ends, and a couple of finger pad washers to the sides to press on. You adjust the pencil to the right gap using measured thickness gauges, or a calibrated wedge. Works great!

Great refurbishment, looks very efficient!

I have the original Sacconi compass that works on the same principle, but I have never been able to get along well with it, hence the "invention" of the contraptions I made. They are specific for archings, but they have the indisputable advantage over yours (and the Sacconi) of having an extended flat support surface on which to rest the still flat underside of the plates, which allows you to keep the pencil firmly orthogonal to the plane, quite difficult if you have a single and round foothold. I found this to be a great improvement that also speeds up the tracing operations a lot and makes them easier and more accurate. As for tracing on curved surfaces such as marking the thicknesses, in fact they do not work at all, I had to make a variant to the prototype for this use, which being more sturdy and compact than the compass, allows a better grip and is more stable, I find it better than the compass in the practical use.

[Davide Sora]

2 hours ago, carl1961 said:

Thanks David for your work and pictures, I will do some and 3D print them.

Sure, 3D printing them will take a lot longer than simply making them out of wood, but I guess you will find many lazy people willing to pay to get them ready-made and ready to use.

Damn, I should have patented them

[Don Noon]

1 hour ago, Davide Sora said:

One thing I definitely could have made better is to make the cut wider, I've made them a little tight, and if the pencil isn't the right diameter, they don't tighten well.

If drilling a second hole is too much work, I'd at least extend the saw cut some distance past the pencil hole.  And make the cut wider.  

[Davide Sora]

32 minutes ago, Don Noon said:

If drilling a second hole is too much work, I'd at least extend the saw cut some distance past the pencil hole.  And make the cut wider.  

Yep, making the cut wider is essential, and extending it beyond the hole also makes it more functional