Sean Couch’s Bench

[Mike Atkins]

1 minute ago, Sean Couch said:

I made an error right out of the gates. I ordered my form and templates off of eBay so I don’t even know what my starting point is supposed to be. That doesn’t excuse my long corners, if I put my template on my rib garland, I can see my mistakes. I can’t honestly tell you why I didn’t check them when I was carving the corner blocks. Either the excitement of a new project got to me or I had a senior moment, or a combination of both. Hehe

I spent some time with the SVG files from the “making the violin” website so I think I have a set of drawings that “should” be good to go. The raw SVG files were out of scale for me. I think the author used 90 dpi instead of 96 so depending on what you use to open the files, the scale could be wrong.

My neighbor is a member of a local “makers guild” so I have access to a laser cutter. I may go that route also, or use your drawing and make the form by hand. I have a bunch of options and nothing but time, so I am all set.  

If you want I can look up the SVG files and manipulate them in adobe illustrator, then send you a pdf to scale so you can print it out at the right size.

[Sean Couch]

I might hit you up on that offer in the future. For right now, I am good. Thanks though.

I am working in Ubuntu Linux and I don’t think the Adobe products work there. I loaded some other programs and they got me squared away for now. I just can’t print them out because of the odd sizes of paper needed, but there is a printing place a mile from me. I’m sure they could get it done.

[Sean Couch]

I haven’t made much progress in the last few days. I did reorganize my workspace and changed my lighting. Now I have some good oblique light to help me see the contours of the plates.

I did practice purfling. The marking/cutting tool and I are not friends anymore. lol. I may try some more but I can’t seem to hold the tool at a consistent angle, even when practicing on a 19mm thick piece of pine. I can’t get short controlled cuts either. It is almost like I need to dull the blades a bit so they don’t bite as much. I get a bunch of the blade biting, then I add a bit more force, and then it skids ahead. Usually doesn’t mess things up, but sometimes it does.

The best luck I have had is by not using the marking tool and just drawing the lines by hand with a pencil and then cutting the line with a knife. It’s not a bad row to hoe doing it that way.

I also tried using a 1.2mm carbide cutter in my mill at 3000 rpm. I cut a small piece of brass rod and clamped it in the vise to act as my guide and then used the vise top as my bearing surface and rotated the part through. Seems to be promising. Here is a practice piece I was drinking around with. That hogged out portion on the right side is where I was testing out to how bad I could mess it up.

[Mike Atkins]

1 hour ago, Sean Couch said:

I get a bunch of the blade biting, then I add a bit more force

Oooo... I would let the tool do the work. Maybe you could use the force to lighten the cut vs adding pressure? Sometimes if a tool is being aggressive I just put effort into making it a lighter cut. It might be preferable over dulling it as a sharper tool should be easier to control. This is also a good rule for starting a saw cut with a handsaw IMO, just back it off a bit.

 

1 hour ago, Sean Couch said:

The marking/cutting tool and I are not friends anymore.

I hear this...

[Sean Couch]

I will give the purfling marker another go. I didn’t clamp the workpiece in anyway. I’ll try clamping it and using two hands on the cutter. The second hand to try and control any skip and the downward pressure.

I think what is happening is that the blade hits the harder grain, then I add more pressure and the harder grain cuts but there is no resistance until the next band of hard grain, but I have too much momentum for the hard grain to stop the cutter.

I agree with you that I shouldn’t dull the blade. Kind of goes against conventional norms. Plus, I like my blades hair popping sharp. 

[Mike Atkins]

27 minutes ago, Sean Couch said:

I will give the purfling marker another go. I didn’t clamp the workpiece in anyway. I’ll try clamping it and using two hands on the cutter. The second hand to try and control any skip and the downward pressure.

I think what is happening is that the blade hits the harder grain, then I add more pressure and the harder grain cuts but there is no resistance until the next band of hard grain, but I have too much momentum for the hard grain to stop the cutter.

I agree with you that I shouldn’t dull the blade. Kind of goes against conventional norms. Plus, I like my blades hair popping sharp. 

Do you have a soft rounded point on the blade? or is it sharpened to a pinpoint? That could also make a difference maybe?

[Sean Couch]

It is a sharp point. I have not modified it since I received it. They are replacement blades for a current production purfling marker.

I tried clamping the wood and using two hands to guide the tool, but it was still a struggle. The inner most line, in the picture below, is with the marking tool with one blade, the bevel is against the waste. The skidding kills me.

[MikeC]

here is a picture of my marker blades.  Don't try to cut with it, just mark lightly. 

[Mike Atkins]

10 hours ago, Sean Couch said:

the bevel is against the waste

Ahh... so with a blade shaped like this, I don't think you can always have the bevel against the waste because it only cuts in one direction. Really you need to cut "downhill" or the grain will fight with you and pull the blade away from you...I added arrows showing the cutting direction where the grain should give the least resistance.

Ideally a bevel that comes to a soft v would allow you to keep the bevel on the waste side and cut in either direction while the shape of yours doesn't. Also the blade probably needs to be sharper...it's hard to tell from the photo but it looks like maybe it isn't sharp enough. Usually when it's really sharp it will look like a mirror and you won't see a single sharpening scratch (on the flat and on the bevel side).

[Mike Atkins]

This video of Mr. Sora doing the purfling is helpful to see his technique, granted his skill level is really really high so most of us mortals are going to have a harder time with it...
 

 

[MikeC]

Here's the purfling marker I made in 1985 when I made my first attempt at a violin. It wasn't very

good. The violin I mean, not the marker,  the marker worked ok but the violin was not good.  That's an exacto blade with some spacers in it. 

 

 

[Sean Couch]

I’ve been whittling away at the back. Getting closer with every stroke of the plane/gouge.

[Mike Atkins]

Nice!

[Sean Couch]

I think both my top and bottom plates are ready for purfling. I am going to double check my overhang and corners again before I start. Right now they look pretty good to me, and the top and back plates are very close to having their profiles match.

[Mike Atkins]

17 hours ago, Sean Couch said:

I think both my top and bottom plates are ready for purfling. I am going to double check my overhang and corners again before I start. Right now they look pretty good to me, and the top and back plates are very close to having their profiles match.

They're looking good Sean! Nice work!

[Sean Couch]

Thanks Mike. It’s a good thing I went back and checked my overhangs. Found some more places that needed some work. Now I reckon I should do one last check before I plug the locating holes. 

[Sean Couch]

Yesterday I built a platform that I can clamp in my mill vice. It is made out of 3/4” plywood with a 1/4” brass pin in the middle to act as a guide while cutting the purfling channel with a carbide cutter.

So today, I finally worked up the courage to give it a go. It was absolutely terrifying. Lol. All I could imagine was losing hold of a plate and having the mill toss it across the room. Thankfully all went fairly well and the channels look ok. I will finish the corners and under the button by hand.

[Sean Couch]

The purfling is in. Could be worse and definitely could be better. I tried to do the Roger Hargrave method and it seemed to go just fine. I brushed on the boiling water a little over an hour ago.

I have a chipped corner in the bottom bout, right hand side in the picture. That was my first corner cutting in by hand. I also had some trouble on the back under the button. I’m not going to blame my tools for my errors, but I need a better knife. Might be time to make that violin knife.

As you can see, I have some other gaps as well. I’m hoping they are mitigated when I cut the fluting, but I am not expecting them to get much better. I am also not sure how far the boiling water penetrated. I brushed it on pretty liberally but my channel was pretty snug. I didn’t have to hammer the purfling into the channel, but it didn’t just drop in freely either.

What is the best way to fill the gaps and the chipped corner? For the corner, I can make a little maple plug and glue it in, not sure what the best method is for the other general gaps or if they should be filled or not.

My hacked up corners:

 

Purfling cut and bent:

How they look now after brushing on the boiling water:

[Mike Atkins]

That doesn't look too bad at all...better than any attempt I've made!

[Sean Couch]

On 5/27/2024 at 8:11 PM, Mike Atkins said:

That doesn't look too bad at all...better than any attempt I've made!

Thanks, it is coming along.

[Sean Couch]

Worked on the fluting on the violin back today. It went fairly well, I’m just slow. I think the fluting did mitigate some of my poor purfling channel cutting skills. 

I tried to leave a 1mm edge around the fluting but it is not very consistent. The bottom of channel is at about 3.3 to 3.4mm thick so I have a bit more to go to get to 3.1mm. I need to figure out a better way to measure it. The graduating calipers I bought are not very accurate and I don’t trust them (I didn’t expect much for $30, but better than what I got). Sometimes the measurement is 0.3mm off compared to my good calipers. Unfortunately my good ones are just straight jawed. I will make some rounded anvils for it tomorrow.

Sorry for the bad pictures, but it wasn’t easy to get the fluting channel to show.

 

 

[Mike Atkins]

Looking good, and the purfling is looking cleaner like you said with the fluting too, nice work!

[MikeC]

yeah it's looking good.  How did you go about carving the arching of your plates?   Mine is taking a long time but I don't get to work on it for very long at a time.  

[Sean Couch]

10 hours ago, MikeC said:

yeah it's looking good.  How did you go about carving the arching of your plates?   Mine is taking a long time but I don't get to work on it for very long at a time.  

I’m still working on the arching. I have been going back and forth trying to use my templates to show where to take away material. I have had trouble trying to get my sixth template to fit. Hoping now that I have the fluting in and fairly close, I can get my long arch to fit better.

[Sean Couch]

The top was much quicker to get down to the same level as the maple back, it took me about 1/3 of the time as the front. They both need to be refined a bit, but that will have to wait until I get my arching closer and also for me to figure out my thickness gauge issue. I am leaning towards just buying a decent graduating caliper. I do have a digital 25mm travel micrometer that I could use and would have to make my own frame.