Sign in to follow this  
Michael_Molnar

Mike Molnar's Bench

Recommended Posts

On 9/1/2019 at 7:24 AM, Michael_Molnar said:

We had a family event in New York City, so we made a stop at the Met to see  Stradivari 's 1711 "The Antonius".

IMG_9797.thumb.jpg.42e387cf0624f2e852f649f96d63489d.jpgIMG_1402.thumb.JPG.ee46d7dbbf05966aa0fe35b38c760ccd.JPGIMG_1403.thumb.JPG.27b00915a926b79ef4dac05320f89dcd.JPG

nice

 

Share this post


Link to post
Share on other sites

I am back on the air with the CNC. I laid out an entire new top trying to get closer to a Strad contour. I had to redo the f-holes. My program lets me tweak the position X,Y position and rotate them a few degrees around the vertical Z axis at the CNC machine. That f-hole "needle" end mill is only 0.75 x 6 mm going at 35K RPM. I go down to 5 mm in three passes at a snail's pace.

Although this is a test plate of red spruce, 0.41 density, I may use it because it came out so good. I guess I am getting good at this. Usually I destroy one or two plates before getting a good one.

If you look closely you can see a surface ripple that I blame on a cheap ball socket screw assembly on the Y-axis. However, I am not after a micron finish. This plate will easily clean up with a scraper. I am pleased with so little tear out. This contour cutter is a bull-nosed (not a ball end) 1/4" end mill from Precise Bits (0.06"radius corners 2 flutes. I immediately noticed from its cutting sound that it is s good cutter.

Tomorrow, I will flip this plate over and hog out the inside. The f-hole center plugs will then fall out.

I also expect to get in some brown oxide pigments for testing. I can never get enough pigments.

 

IMG_1435.thumb.JPG.a11a8530e783ba73050ae6d01be3ab95.JPG

IMG_1436.thumb.JPG.46b542f0f56e8d2d514c399a8a5c1f05.JPG

 

Share this post


Link to post
Share on other sites

Thank you for the mill info. Comes in handy for us newbies. I think I am going to order those. Been chipping away at some modeling. Any particular reason for the tail at the bottom of the plate? Love the hold down setup!

Share this post


Link to post
Share on other sites

The plate shape for a top is identical to a back. I use the same program for both. The neck button will be removed as well as the bottom tab from a top. There are three reasons I attach these tabs.

1. The tabs reduce breaking the glue seam due to router vibrations. This is insurance in a way.

2. I use these tabs for holding down and supporting the plate upside down to hog out the inside.

3. The bottom tab serves as a narrow extension for the end mill to start cutting the wedge end gently. Without it, the end mill does not know where the edge begins. My plate wedges are various lengths. The tabs cut the wedge down to size and avoid crashes.

Of course, the button is not cut off a back plate. I committed that sin only once amd have been doing penance ever since. :D

Share this post


Link to post
Share on other sites

Now here is a photo of hogging out the inside of the plate. Note how the f-hole cutouts fall out. You can also see how I use the bottom tab and tie-downs to raise and support the upside-down plate. After I cut off the tabs and tie-downs, I will start purfling. 

Life is good when everything works. :)

IMG_1438.thumb.JPG.9e5630d8f005b48d6e0a3e2a322c3690.JPG

Share this post


Link to post
Share on other sites

Ahh I see, dual use of the tabs for inside material removal! I was wondering how I would accomplish that. Assuming your outside arch is finished, what would you recommend leaving for final scraping? I was thinking .2 or .3 mm.

Share this post


Link to post
Share on other sites

The amount of scraped material depends upon the surface quality and how close you are to the final shape. I like to leave some meat on the bones as it were. My CNC'ed plates are about 5mm thick overall. I then scrape the top to a final smoothed contour. Then, I remove the excess as I graduate the interior. A lot of handwork remains after CNC'ing. 

Share this post


Link to post
Share on other sites

I finally cut up the split billets of log 1704 from Kevin Prestwich.  After sawing off the ends to view the grain pattern, I pick the straightest section (40 cm) and use the plastic template to find the cleanest cuts. The red tape on the template is needed to find it on my cluttered bench. I then use the planer to flatten and align the spine's grain lines. I feel that the Grizzly jointer/planer saved the day. IMG_1444.thumb.jpg.57140acf60af356ca6c2b16ec7127dfa.jpg

IMG_1445.thumb.JPG.2345fd4652f3ca09aa8f6cc9e28fadb2.JPG

IMG_1454.thumb.JPG.de9cff1081208f9d5dd8bcb946eb6395.JPG

The wedges are then sawn on my bandsaw. It's a helluva lot of work and sawdust - something that Rover, the robovac, can appreciate.

Share this post


Link to post
Share on other sites

One nice thing about resawing your own tops out of Kevin's billets:  there's plenty of wood there for blocks and bass bars, and sometimes even an extra set.

Share this post


Link to post
Share on other sites

After a long hiatus, I fired up the CNC after making a lot of repairs. Like me, the machine is showing its age. However, we are still functioning. These photos show the plate shape and hold-down tabs which are sawn off after the top surface is done.  The next process is to do the surface contour tomorrow.

A71B2375-0D9C-44FC-9DD7-5C93C85E8291.thumb.jpeg.193e370eba6a2e3648e12c9d1f7cebb8.jpeg

 

 


B4574573-2BBA-4B01-B339-E17C15AEC245.thumb.jpeg.774491977b0f67afd6b30b692d5f381c.jpeg

Share this post


Link to post
Share on other sites

Here is the next step, contouring  using a new model made with the help of a friend’s critiques. I am using a bull nosed end mill with 0.060” corners. 

This photo is taken through the window of the dust cabinet.

855BFC5E-4632-46BA-ADD1-F9BF96DA0FAF.thumb.jpeg.a805273782048f0ae39f0afd0a10bc0c.jpeg

Share this post


Link to post
Share on other sites
On 1/19/2020 at 7:44 PM, Michael_Molnar said:

After a long hiatus, I fired up the CNC after making a lot of repairs. Like me, the machine is showing its age. However, we are still functioning. These photos show the plate shape and hold-down tabs which are sawn off after the top surface is done.  The next process is to do the surface contour tomorrow.

A71B2375-0D9C-44FC-9DD7-5C93C85E8291.thumb.jpeg.193e370eba6a2e3648e12c9d1f7cebb8.jpeg
 

It is hard to tell from the pic but is that a straight flute bit to cut the outline? From the fuzz on the top edge it almost looks like an up cut mill at work.

Share this post


Link to post
Share on other sites

I use this straight flute for holes (!) and edges. It is neither up-  nor downcut. Yes, the edge will have fuzz with this cutter, but what does that matter? I know you are thinking of chip removal, but wood does not behave like a metal. The wood chips fly out. I think it’s due to air turbulence. 
 

For deep holes, I stick with upcut spiral flutes.

Share this post


Link to post
Share on other sites

Thanks, UL. Here’s another family photo. :D

Here is the flip side being hogged out. This end mill is a 1/4” 0.060” corner bullnose.  The edge is about 7 mm thick and I’m taking the plate thickness down to 4+ mm.
 

64456008-DCDE-4B97-BD58-7DAD53B63849.thumb.jpeg.6294bea329b2ab9a5b60d1d8e6deb8f0.jpeg

Share this post


Link to post
Share on other sites

I am in the midst of rolling the edges with files. The first three left to right are crossing files 00, 0, 2 Swiss pattern. The fourth is a half round 0.  Next I will be graduating the plate.

518A9CCC-6579-4244-ACED-5EC6B6168E00.thumb.jpeg.4d30dec99dc75f693416005dfe25c247.jpeg

Share this post


Link to post
Share on other sites

Life goes on here. At the bench I glued a top, garland, and back together

DE6358D9-F1E1-4857-8954-A1865E1BCA4E.jpeg.fefa6d628b6b3659f458d8f6c5650de9.jpeg

Next I pulled from the shelf a neck/scroll done on my CNC a long time ago. I also inserted some stiff graphite rods as an experiment as you can see. Now, I scrape and gouge away this roughed out scroll. 
 

5D91D4A3-9827-400A-A64D-B77ADA19FF47.jpeg.a1351eb17af38534b99be8140fd83677.jpeg6040692C-9776-4A18-87CF-D8FC3E6A392C.jpeg.b05bb2c01adcaa21413f4a3db535929b.jpeg

 

I will refer to this latest work in progress as my coronaviolin.:rolleyes:

 

Share this post


Link to post
Share on other sites

Work on the coronaviolin continues. Today I glued the fingerboard and nut onto the neck. I know this clamp setup is not kosher, but it works well for me. Tomorrow, I will remove the clamps and finish up this neck assembly.

3E3A39EB-6686-45C2-A7F3-3523EB0E068A.jpeg.b8cb50fc1d2afd341f26912b24c3fdf9.jpeg
 

I hope that everyone is well and safe.

 

Share this post


Link to post
Share on other sites
2 hours ago, Michael_Molnar said:

Work on the coronaviolin continues. Today I glued the fingerboard and nut onto the neck. I know this clamp setup is not kosher, but it works well for me. Tomorrow, I will remove the clamps and finish up this neck assembly.

3E3A39EB-6686-45C2-A7F3-3523EB0E068A.jpeg.b8cb50fc1d2afd341f26912b24c3fdf9.jpeg
 

I hope that everyone is well and safe.

 

Mike Molnar, Frank Sinatra..."did it my way!" looking good

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.