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View Full Version : The ellipsograph used in "The Woodwright's Shop"



gwilson
08-10-2011, 03:40 PM
http://i1111.photobucket.com/albums/h463/gwilson5/DSC_0004.jpg

This was a special tool we made for the Anthony Hay cabinet shop in Williamsburg. They were reproducing an old toolchest with large oval inlays. They also wanted this tool to use as a demonstration for an upcoming woodworking forum in Williamsburg a few years ago.

It was also seen in a presentation of "The Woodwright's Shop" on T.V.. Marc Hansen and Ed Wright,two of my journeymen were demonstrating how they were doing the inlay work inside the toolchest.

I also made a sharp swivel knife that can be used in place of the pencil for cutting out paper patterns.

I made the knurls that were used on the various knobs. They were made by running concave knurl blanks against a rotating tap in a lathe. Just normal taps for cutting threads.

The base is mahogany. The length of the mahogany bars is about 6".

By adjusting the knobs where the 1/4" square brass rod goes through their blocks,ellipses of different shapes and sizes can be generated.

gwilson
08-10-2011, 03:44 PM
http://i1111.photobucket.com/albums/h463/gwilson5/DSC_0006.jpg

Another view of the ellipsograph. The brass blocks slide quite smoothly in the T slots.

Underneath the mahogany base are 2 very small,sharp pin points to keep the device from skidding around as it is used.

gwilson
08-10-2011, 03:49 PM
http://i1111.photobucket.com/albums/h463/gwilson5/DSC_0005.jpg

A view of the swivel knife attachment. The rod just fits through the hole that the pencil normally uses. This also shows the old fashioned knurls that were made using taps.

madwilliamflint
08-10-2011, 03:53 PM
That's beautiful.

How's the brass attached to the mahogany?

gwilson
08-10-2011, 03:57 PM
They have flat head screws silver soldered underneath the brass pieces. These screws go into drilled holes filled with glue. Doing it this way prevents the inevitable reappearance of the heads of screws put in through the top and filed flush when the wood slightly responds to humidity changes.

Tony
08-10-2011, 04:17 PM
brilliant work!

and here's a coincidence for you.. I just watched that episode a few
days ago! Here's the link:

http://www.pbs.org/woodwrightsshop/video/2800/2810.html

gwilson
08-10-2011, 04:21 PM
It was on here last night,too.

Hal
08-10-2011, 05:37 PM
G

Those knurls are great. They sure add a touch of class.
One of these days I'll try to make some.

Thanks for sharing your work, it's inspiring.

Hal

alsinaj
08-10-2011, 06:01 PM
GW, can you describe how the old-fashioned knurls are made with a tap? Thx.

Black_Moons
08-10-2011, 07:18 PM
They have flat head screws silver soldered underneath the brass pieces. These screws go into drilled holes filled with glue. Doing it this way prevents the inevitable reappearance of the heads of screws put in through the top and filed flush when the wood slightly responds to humidity changes.

Silver soldering screwheads and then glueing in the threads? Nifty doublehack! Never would of thought of that.

sasquatch
08-10-2011, 07:28 PM
Beautiful piece of work!!

gwilson
08-10-2011, 08:03 PM
I did a pretty thorough posting of making knurls on the Practical Machinist forum several months ago. You could go there and do a search. Lots of pictures of the process.

If anyone wants to paste it here,that's fine. I don't know how to do that.

Chester
08-10-2011, 08:44 PM
Is this the one?

http://www.practicalmachinist.com/vb/general/how-make-knurls-pictures-212670/

gwilson
08-10-2011, 08:49 PM
Yes,I believe so. Thought it had more pictures,but those are enough. Plus the lengthy explanations. I've had a few guys make their own knurls from reading that post.

Scottike
08-10-2011, 09:23 PM
Beautiful workmanship, G.W.! I love how you made the knerls with the tap. A tap and overcome!

Your Old Dog
08-11-2011, 12:33 AM
Really great workmanship. Is the tap under power or turned by hand when you made the knurl? What ever you did it worked great. Was this the process known as hobbing?
http://www.practicalmachinist.com/vb/attachments/f38/27240d1287488652-how-make-knurls-pictures-img_0225.jpg

j.bain87
08-11-2011, 06:13 AM
Here's another one, goes by a different name tho'.


http://growabrain.typepad.com/growabrain/2008/05/bull****-grinde.html

fciron
08-11-2011, 09:42 PM
Is this the one?

http://www.practicalmachinist.com/vb/general/how-make-knurls-pictures-212670/

That's the one! I've got my knurls and a project I used them on at the end. :cool: Hmmm,

I've been ogling ellipsographs in a book on drawing instruments. I might have to give it a go at some point.

gwilson
08-12-2011, 11:08 AM
Old Dog,I suppose it is a home grown form of hobbing. Since I am telling you about it,it probably is hob-knobbing.

Chester,your link doesn't come up,but I can tell from the title that it is a reference to the old B.S.grinder,or "smoke grinder",etc. that used to be wooden toys. Exactly the same principle. Just make sure the sliders fit well in their T slots so you don't draw shaky looking ellipses.

EddyCurr
08-12-2011, 12:53 PM
gwilson, thank you for the image showing your technique for concave knurling
and thanks to Chester for providing a link to the PM thread with your original
discussion of the subject.

To others here who, like me, may wonder how gwilson's convex knurls shown
on the ellipsograph are made, the answer can also be found in the PM thread
(first make a concave knurl, then use this to cut a convex one.)

.

gwilson
08-12-2011, 01:00 PM
Yes,Eddie,a concave knurl makes a convex knurl on the work you are doing. Or,you can use the concave knurl as a "mother knurl" to make a convex knurl,should you want to produce a piece of work with concave knurling on it as a decoration.There is no practical application for concave knurling I can think of,except for use on jewelry,perhaps.

EddyCurr
08-12-2011, 01:12 PM
On the subject of tools for making ellipses, I am reminded of a thread from
earlier this year 'Machining Ellipses' (http://bbs.homeshopmachinist.net/showthread.php?t=46538) by sbmathias.

I am not comparing craftsmanship or design, only drawing attention to
sbmathias' description of a simple technique for creating ellipses with a
router (and possibly a mill) for those here with an interest.

.

EddyCurr
08-12-2011, 01:19 PM
There is no practical application for concave knurling I can think of, except
for use on jewelry, perhaps.My interest was for decorative work but I believe that concave knurling would
also serve a useful purpose on rolls intended for feeding/restraining rope-like
material.

.

gwilson
08-12-2011, 01:20 PM
That sounds useful.