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Purfling knife for first build


TerryOnStrings
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I hesitate asking questions about tool recommendations because everyone has different preferences and opinions, but I'm struggling to find clear information about the type of knife to use for cutting the purfling channel after it's marked. Searching for a 'purfling knife' typically gives results for purfling markers, and I already have one of these. I also see results that include the double-beveled Hock violin knife, which I'm sure is a great tool, but I'd think a single-bevel blade would be more appropriate here.

So here goes... any recommendations for a purfling knife for a first build?  Angled tip? Rounded tip? Note as woodworker I'm used to making custom tools, but with all the new tools, jigs, molds etc. I've already made for this first build, I'd really prefer to just buy a decent knife and get back to work.

Thanks,
Terry

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1 hour ago, TerryOnStrings said:

I hesitate asking questions about tool recommendations because everyone has different preferences and opinions, but I'm struggling to find clear information about the type of knife to use for cutting the purfling channel after it's marked. Searching for a 'purfling knife' typically gives results for purfling markers, and I already have one of these. I also see results that include the double-beveled Hock violin knife, which I'm sure is a great tool, but I'd think a single-bevel blade would be more appropriate here.

So here goes... any recommendations for a purfling knife for a first build?  Angled tip? Rounded tip? Note as woodworker I'm used to making custom tools, but with all the new tools, jigs, molds etc. I've already made for this first build, I'd really prefer to just buy a decent knife and get back to work.

Thanks,
Terry

I use two double beveled knives. A 20mm knife to gently firm up the marked line and correct any chatter of the marker followed by a single cut as deep as I can go all the way around on both sides of the groove. Then I use a second knife with a slimmer grinding angle to make a final pass as deep as I can before picking out the waste wood. The second knife can cut deeper because the slimmer blade doesn't drag on the sides of the previous cut. If you search Purfling site:maestronet.com you should find an in depth discussion of this topic.

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I use these, double bevel blade, modified to shorten it by grinding the back to make it more stiff, and re-sharpening them on the water stones to make the bevels smoother and not concave, and sharper.

https://www.amazon.it/STANLEY-0-10-401-Escalpelo-hobby-pm/dp/B00449ESAG/ref=sr_1_1?__mk_it_IT=ÅMÅŽÕÑ&crid=L795U6RESLSD&keywords=STANLEY+0-10-401+tagliabalsa+120mm&qid=1647597529&sprefix=stanley+0-10-401+tagliabalsa+120mm+%2Caps%2C78&sr=8-1

Of course, a "traditional" double bevel knife with a thin tip is fine too, but you will have to spend a lot of time re-sharpening it every time the tip breaks. Even with these replaceable blade cutters it can happen, but you can easily restore the tip very quickly by modifying the back only, instead of redoing the bevels on the grinding wheel every time.

I have never been happy with single bevel, because the knife has to cut both along convex and concave curves, and the flat side of the single bevel doesn't work well if it has to cut facing inside the concave curves. The cutting edge will tend to snag and to go straight, leaving the track.

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I've used the "exacto" blades just like in Davide's link above but I had bad luck with the handles (blades coming loose unexpectedly) so I take a round wood stick (maple offcut of similar diameter to the original) cut quick notch in the end with thin kerfed saw and glue the blade in with CA glue, I usually wrap the cut in the handle with few turns of a thick thread and apply some CA to that. I shape the wood handle so that it creates a spine on the thin blade almost to the tip (before gluing he blade in) and I remember I broke the tip just once when the knife rolled from bench and hit ground exactly with the tip.

I mostly resharpen on 600/1200 grit paper on flat surface and follow up to 3000 or I reshape the back of the blade just lie Davide noted.

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14 hours ago, TerryOnStrings said:

I hesitate asking questions about tool recommendations because everyone has different preferences and opinions, but I'm struggling to find clear information about the type of knife to use for cutting the purfling channel after it's marked. 

Since everyone has slightly different methods of maintaining control of their tools, different preferences are expected I think.  :) 

I used (and the past tense is due to the fact I primary restoration now, so the knife is used on those occasions I need to cut a new section of channel) for the bulk of the cutting when making a new instruments. I made it from straight razor steel almost 40 years ago. You mentioned it would be nice to find something "ready made", but once you get into modifications the effort saved may be less than desirable.

The knife blade has curved & polished sides and the width tapers from just a smidgeon over 1 mm at the handle to a (fine) width a few mm  from the point; in a very slight "bullet" shape, which gives the business end of the steel a little more support. The handle is about 15 cm in length which gives me a good visual (to make sure I don't swing wide or narrow). It cuts smoothly, the tip rarely breaks unless I do something stupid, the blade follows the scribed line from the purfling marker well and doesn't tend get stuck as you cut down to depth. Long and short of it is: it works for me.  Your results may vary!

Sorry for the reflection, in the photo (bright touch-up lights on today), but I think you'll get the idea.  Good luck!

idea.IMG_2157.jpg

 

 

 

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My wood-working background is from crafting American Flintlock Longrifles. I inlet wood and metal by stabbing-in the mortise with a flat or slightly nosed (radiused) chisel for the long sweeping curves and gouges for the tighter curves  rather than using a knife.  I stab-in and rocking-walk the chisel or gouge along the guide lines. For Maple, I use a small rawhide mallet to tap in the chisel, but hand pressure alone suffices for the softer wood of the belly plate.  The waste wood in the channel is then cleared out with chisels or a purfling pick. 

Not my tool set, but chisels similar to these.

spacer.png

 

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I've tried many and varied knives but have ended up with the below profile.  While it might be hard to imagine this working well, it actually does.  Amongst other things, it is possible to make both pull and push cuts which can be helpful especially with spruce.

P1060357.JPG

P1060356.JPG

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Thanks for all the responses and sharing your experiences. I'm not at all surprised to see a variety of different solutions being used successfully. I think that's great. I'll pick as few of these to try an see what works for me. I have some extra purfling and spruce cutoffs to experiment with.

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2 hours ago, John Harte said:

I've tried many and varied knives but have ended up with the below profile.  While it might be hard to imagine this working well, it actually does.  Amongst other things, it is possible to make both pull and push cuts which can be helpful especially with spruce.

P1060357.JPG

P1060356.JPG

If the dimensions are small (blade a few mm wide) I think this shape can work really well, and there is no tip that can break.:)

However, the actual dimensions are not clear from the photo, important information is missing.;)

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12 hours ago, Davide Sora said:

I use these, double bevel blade, modified to shorten it by grinding the back to make it more stiff, and re-sharpening them on the water stones to make the bevels smoother and not concave, and sharper.

https://www.amazon.it/STANLEY-0-10-401-Escalpelo-hobby-pm/dp/B00449ESAG/ref=sr_1_1?__mk_it_IT=ÅMÅŽÕÑ&crid=L795U6RESLSD&keywords=STANLEY+0-10-401+tagliabalsa+120mm&qid=1647597529&sprefix=stanley+0-10-401+tagliabalsa+120mm+%2Caps%2C78&sr=8-1

Of course, a "traditional" double bevel knife with a thin tip is fine too, but you will have to spend a lot of time re-sharpening it every time the tip breaks. Even with these replaceable blade cutters it can happen, but you can easily restore the tip very quickly by modifying the back only, instead of redoing the bevels on the grinding wheel every time.

I have never been happy with single bevel, because the knife has to cut both along convex and concave curves, and the flat side of the single bevel doesn't work well if it has to cut facing inside the concave curves. The cutting edge will tend to snag and to go straight, leaving the track.

This is why I follow you and why! Totally open and honest what you do (I do the same BTW not because you do, but...). It is the simplest way with mothern tools (combined with old ways to get things done)

Way to go!

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3 minutes ago, Davide Sora said:

If the dimensions are small (blade a few mm wide) I think this shape can work really well, and there is no tip that can break.:)

However, the actual dimensions are not clear from the photo, important information is missing.;)

Blade dimensions: 8mm wide, 1.44mm thick.  Length of blade protruding from handle 25mm.

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I use the veritas carving knife. I like the metal components, as it helps "drive" my cut, and eliminate chatter and whatnot. 

https://www.leevalley.com/en-us/shop/tools/hand-tools/carving-tools/knives/31088-veritas-carvers-knife

I use the bullet shaped blade for the bulk of the work, and the very fine straight blade for the corners. The hooked ones I pretty much just throw away. The handle even has a little plug in the end that has a magnet so you can store the blades that you are using. 

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Cutting edge 35 mm long. Back of blade tapers tapers from 1.4 to .6 mm near tip. Handle end 2 mm thick.

To get a really acute edge you need to start with thin stock. So using a disposable blade like a Stanley is the easiest way to achieve that.

The one I have made in the pics is about as acute as is possible with hand grinding. And it is very hard steel that's why I have hollow ground it to make honing easier. It is bevelled on both sides.

 

 

1672331212_DSC_00024.jpg

124019471_DSC_00013.jpg

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16 hours ago, Rico Suave said:

My wood-working background is from crafting American Flintlock Longrifles. I inlet wood and metal by stabbing-in the mortise with a flat or slightly nosed (radiused) chisel for the long sweeping curves and gouges for the tighter curves  rather than using a knife.  I stab-in and rocking-walk the chisel or gouge along the guide lines. For Maple, I use a small rawhide mallet to tap in the chisel, but hand pressure alone suffices for the softer wood of the belly plate.  The waste wood in the channel is then cleared out with chisels or a purfling pick. 

Not my tool set, but chisels similar to these.

 

 

HI Rico  I have some experience building a long rifle also and I have one now that needs some repair when I get time. I recently converted it from percussion to a small Siler flintlock. 

 Are you a member on Americanlongrifles forum?   

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I have used an exacto knife but don't like it so next build I'll make a custom blade for the purpose.  What I don't like about the exacto is the point breaks off and also I don't like the straight edge.   

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16 hours ago, John Harte said:

Blade dimensions: 8mm wide, 1.44mm thick.  Length of blade protruding from handle 25mm.

Thanks for specifying, it's just a little big for me but I guess it works perfectly for you. In this kind of thing, I think that getting used to your tools is fundamental to bring out the best, it's a personal thing and what works for me doesn't necessarily mean the same for everyone.;)

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In the vein of Davide's post - Bard Parker no 11 rib backed scalpel blades are great for purfling, and especially excell on corners. Having some of those and their (or those by Feather) curved scalpel blades makes short work of the task. They're inexpensive and are always much sharper out of the box than hobby knife blades. Started using them for voicing harpsichord quills years ago, where minute cuts on tricky materials is required (delrin, celcon, bird quill). 

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17 hours ago, Peter K-G said:

This is why I follow you and why! Totally open and honest what you do (I do the same BTW not because you do, but...). It is the simplest way with mothern tools (combined with old ways to get things done)

Way to go!

Thank you!:)

I think that sharing experiences is fundamental in our work, we don't need to be afraid of competition. In any case, I am not afraid to share because I am aware that it is not the only good way to do it, and I always hope to know how others do to learn something to think about too. Then, even knowing what I do in detail, the hardest part is being able to do what I do getting the results I get. You have to work hard to acquire the necessary dexterity, which remains the main factor whatever the tool or method you use.;)

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5 hours ago, MikeC said:

HI Rico  I have some experience building a long rifle also and I have one now that needs some repair when I get time. I recently converted it from percussion to a small Siler flintlock. 

 Are you a member on Americanlongrifles forum?   

I am

I'm not as active since I'm currently concentrating on (re)learning to Fiddle and reviving my dormant luthierie interests, but here is a chronicle of my last build

https://americanlongrifles.org/forum/index.php?topic=61420.0

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3 hours ago, Rico Suave said:

I am

I'm not as active since I'm currently concentrating on (re)learning to Fiddle and reviving my dormant luthierie interests, but here is a chronicle of my last build

https://americanlongrifles.org/forum/index.php?topic=61420.0

wow that's a nice build.  I'm very envious of your ability to engrave!  I tried that on mine and it didn't turn out very well.

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19 minutes ago, MikeC said:

sswow that's a nice build.  I'm very envious of your ability to engrave!  I tried that on mine and it didn't turn out very well.

 

Thank you for the compliments. I feel my engraving is ham-fisted and could be more refined with more practice. 

I took an NRA Sponsored 2 week long Basic Engraving Class at Lassen Community College (Northern CA) back in the late 90s, so I have a good foundation of the basics of chase engraving with Hammer and Chisel. 

I was fortunate to also take an NMLRA sponsored Carving Class at Conner Prairie, IN, taught by Jim Chambers, also in the Late 90s.  

Now, Luthierie fascinates  me and miss the opportunities to learn that SCAVM (Southern California Assoc. of Violin Makers) afforded before they went defunct. I was able to attend a few meetings, tho'.

BOT - lots of ways to skin a cat and I'll likely try some of the ideas offered here. 

 

 

 

 

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4 hours ago, Davide Sora said:

Thanks for specifying, it's just a little big for me but I guess it works perfectly for you. In this kind of thing, I think that getting used to your tools is fundamental to bring out the best, it's a personal thing and what works for me doesn't necessarily mean the same for everyone.;)

Yes exactly, it is personal.  I wouldn't say that what I use is perfect, merely my go to for purfling at the moment.  I do use other knives including options similar to what Jackson mentions.  It all depends on what is encountered along the way.  While what I am able to achieve is reasonably tidy, it is not in your league.:)

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