Help with purfling?

[David Burgess]

27 minutes ago, David Stiles said:

Mine is very similar and came from Dictum. 

https://www.dictum.com/en/cutting-tools-jbe/purfling-channel-cutter-702522

 

 

That's the one I needed to heavily modify. Notice that the horizontal portion protrudes so far inward from the cutting blade position, that it will inevitably have a conflict with the arching  (or at least a somewhat normal arching) in the C bout.

The OP's marker/cutter doesn't appear to have that issue.

[David Stiles]

3 minutes ago, David Burgess said:

That's the one I needed to heavily modify.

I know what you mean.  I need to have the blades protruding further than I would like, so that the end of the bar clears the arch.  This means I need to be extra careful as blades can flex around a bit.  I notice Davide has a firm backing piece clamped alongside his blades and I want to try that out.  What mods did you do? 

[JacksonMaberry]

1 hour ago, David Burgess said:

Can you share your source for that purfling marker/cutter?

It's very much like the one I prefer to use, but mine took a lot of dinking to get it to where yours is.

I like to have backup tools.

The similar unit sold by International Violin is better in my opinion. Only the blades need to be modified for it to work well.

[Wood Butcher]

https://int.gewamusic.com/product/12408/gewa-purfling-cutters.html

[HoGo]

Here is my own version. I made it to try cutting binding ledges on mandolins by hand instead of routing. Worked great. I cut almost all the way with just this tool (set at 1.5mm fromedge). Blade is from old broken bread knife (approx. 1mm thick, I have also another one in case I will do a violin purfling). Body is from walnut and bone and piees of maple. It's got just one wedge holding it together. The other tool is my first attempt from many years ago. I use it in tight spaces around body scroll.

[JacksonMaberry]

41 minutes ago, Wood Butcher said:

https://int.gewamusic.com/product/12408/gewa-purfling-cutters.html

Interesting! It wouldn't be possible to set this one up such as the vertical rod is bearing against the edges of both plates due to the knurling. That takes away the advantage of this style of marker, in my opinion, which is being able to hold it underhand very close to the action and having the two-plate-edge stabilizing contact. 

[Wood Butcher]

36 minutes ago, JacksonMaberry said:

Interesting! It wouldn't be possible to set this one up such as the vertical rod is bearing against the edges of both plates due to the knurling. That takes away the advantage of this style of marker, in my opinion, which is being able to hold it underhand very close to the action and having the two-plate-edge stabilizing contact. 

I don’t purfle on a closed body, so it’s not an issue for me.

I do like the handle to be below the edge of the plate, I find this gives it better stability, and less likely to tilt over, plus I can see what I’m doing easier.

[JacksonMaberry]

21 minutes ago, Wood Butcher said:

I don’t purfle on a closed body, so it’s not an issue for me.

I do like the handle to be below the edge of the plate, I find this gives it better stability, and less likely to tilt over, plus I can see what I’m doing easier.

Definitely agree with that. And you're right, if you're purfling free plates it's another story. 

Edit- one think I like about the model at international (at least I think it's the same from the small, blurry photo - mine is from sai gao originally) is the depth stop. But if you're not using it to cut to depth -and have modified the blades to accomplish that - not a problem.

[Davide Sora]

Gewa's system with the screw from behind is clever to reduce the protrusion that conflicts with the arching. Another clever way would be to replace the screw with a headless screw like these:

https://www.amazon.com/Screws-No-Head-Fasteners/s?rh=n%3A17290023011%2Cp_n_feature_two_browse-bin%3A3269098011

 

[HoGo]

I miss the long cross bar on the Gewa tool it's easier to control the blade position with the long bar otherwise the handle would want to turn (in this case the knurling helps).

On mandolins I cut after the body assembly and hold the tool below the level of plate so I can clearly see where I'm cutting.

[Crimson0087]

The purfling cutter came from yinfente.com out of china. Also bought their thumb planes which actually worked quite well...but the blade on the purfling cutter was really bad and I'm not sure how I'm gonna go about sharpening it yet...

[DMartin]

It’s been some 30 years since I last purfled. A few weeks ago, taking on the challenge yet again, l messed around in quick and dirty mode to work out these “bench slider" concepts.  Thought they would fit this thread as they worked well for me. They allow a low grip.

 

The aluminum snap-on ring of the cutter/marker tool has a region filed to the thickness of the purfling to enable quick switching between inner and outer cut while using a single blade. 

 

The picker blade shown in the 5th photo can be mounted in place of the cutter to scrape the bottom of the purfling channel.

 

The scratch stock helped establish the edge channel. Right thumb grips in place of the purple clamp.

 

I found it easiest to set the cutting depths with the calibrated wedge technique.

[JacksonMaberry]

That's cool!

[uguntde]

On 1/17/2022 at 1:20 AM, Michael Darnton said:

 

This works fine:

Cheap and easy.

 

I prefer this one:

https://darntonviolins.com/purfling-machine-eight-views/

Where does the power come from to turn the rotor.

[David Burgess]

16 hours ago, Crimson0087 said:

The purfling cutter came from yinfente.com out of china. Also bought their thumb planes which actually worked quite well...but the blade on the purfling cutter was really bad and I'm not sure how I'm gonna go about sharpening it yet...

https://www.yinfente-shop.com/Violin-Purfling-knife-Violin-Making-carving-clean-groove-knife-Luthier-Tool-p2345269.html

[Michael Darnton]

5 hours ago, uguntde said:

Where does the power come from to turn the rotor.

It is the handpiece of a Foredom flexible shaft [whoops, thanks] tool.

[Brad Dorsey]

Michael means "Foredom flexible shaft tool."

[CaseyLouque]

I modified mine same brand as op to work more like the way other have posted.

@Davide Sora Has made an excellent point that the cutters included are too thick to be used to actually cut they are 1.3mm each. I have some exacto no. 2 blades and they are 0.6mm each. With a very small shim cut and modified they would work perfectly if you cut grind and modify.

This should be an improvement to the original tool.

This takes a good bit of grinding and polishing on 10 different angles to get this shape and it could be done better.

[jezzupe]

Which reminds me, then of course we could throw in the Dremel rig/jig or the Foredom as an alternate. I always like to have options and I'm not opposed to either or. I do think beginners should go through the motions of being able to execute channel carving the traditional way, but, on the other hand there's nothing like a good LMI or Stewmac downcut bit on a properly set up jig, depending on what your doing, for example if I'm doing a guitar with a very hard material I don't mind "cheating" a bit.

I know of two violin makers who primarily use "rotary" as their main "thing" mostly due to wrist problems. But I don't think there is anything wrong with even if you don't, it is faster and easier and as long as you have primo bits you won't get any burring.

I'm sure there are some in the "wood has feelings"  or perhaps "traditionalist's" {not that there's anything wrong with that} category that think rotary along with sandpaper and electric saws are fundamental sins and that the violin police might want to bring you down to the station for questioning, but I think anything that helps you stick a fork in it is ok and heck the two that I'm aware of that use rotary{excluding myself} are pretty up there if that makes you feel any better about "cheating" 

But I do suggest a good jig that does not rely on "freehand" control, that's a good way to eff shi up. 

 

[David Burgess]

38 minutes ago, jezzupe said:

But I do suggest a good jig that does not rely on "freehand" control, that's a good way to eff shi up.

Most any sort of semi-hand-guided machining process can eff things up in a hurry... faster than human reflexes can react. Been there, done that.

I don't know of anyone who has been able to construct a really good violin by machining processes alone. There is always some following handwork, and in my opinion, being skilled at the preceding handwork steps contributes a lot to bringing the final handwork to fruition.

[Crimson0087]

Oh my goodness I ordered the Dremel guide off stewmac and a 1.2 mm spiral down it bit and it's amazing! Why did I not do this from the start? I'll never go back! I did in 3 min on the back what took 3 hours on the top!

[JacksonMaberry]

1 hour ago, Crimson0087 said:

Oh my goodness I ordered the Dremel guide off stewmac and a 1.2 mm spiral down it bit and it's amazing! Why did I not do this from the start? I'll never go back! I did in 3 min on the back what took 3 hours on the top!

I've found that, unmodified, the stewmac guide doesn't do well on many violin models at the corner radii. But doing the corner mostly by hand anyway, even if you do the rest by machine, gives you a lot more control over the miters/stings

[Bill Yacey]

2 hours ago, Crimson0087 said:

Oh my goodness I ordered the Dremel guide off stewmac and a 1.2 mm spiral down it bit and it's amazing! Why did I not do this from the start? I'll never go back! I did in 3 min on the back what took 3 hours on the top!

I use a dremel for everything except the corners, but you can certainly do a lot of damage in 300 milliseconds if you don't have a strong, sure hand on the guide.

[jezzupe]

5 hours ago, Crimson0087 said:

Oh my goodness I ordered the Dremel guide off stewmac and a 1.2 mm spiral down it bit and it's amazing! Why did I not do this from the start? I'll never go back! I did in 3 min on the back what took 3 hours on the top!

Oh, ya ,well, we just like to see people suffer the old fashioned way 

[uncle duke]

On 1/23/2022 at 11:19 PM, CaseyLouque said:

If it were mine I'd like to be able to go a second time around deeper if needed. 

Anyway of grinding the outsides flatter without ruining the metal?  I try to go 2 mm deep most times.  I have done wore out my routers and favorite bits so it's back to the hand method of cutting.