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radius of curvature of gouge size


Seth_Leigh

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The great majority of gouge sweeps are arcs of circles, and those are the ones that have been discussed here. My "close enough" multipliers won't determine a form pattern for an ovoid or "V" shape gouge, but then, neither will the mathematical formulas put forth.

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John- I wasn't making light of education with my Sagitta, MI comment- I have great respect for the sciences & those that utilize them. I just think it's foolish to have to repeat an excercise like that each time someone may want to make a gouge.

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Hi Seth,

I've been using two 3 sweep gouges to do the edgework (called 'gucia'in Italian) one narrow one about 3 mm and the other about 5-6mm and that has worked very well for me. I use the same gouges to carve my scroll. In fact all I use are three #3 sweep gouges for all my scrolls and edgework and have been since 1986 when I studied violinmaking in Ialy.

What a helpful and useful discussion this has been for you-everyone seems so eager to help you solve your problem you know, make those gouges.

So what are you going to do?

Oded Kishony

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Hey Oded thanks for the comments. I've read some of your posts on the mailing list and visited your site. I've liked seeing the sites people have linked about making gouges. I'm starting to think I should be using a U shaped form and beating my gouge inside that as one article showed using hacksaw blades.

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Quote:

Hi Seth,

So what are you going to do?

Oded Kishony


I got a piece of 1" steel pipe and put it in my vice with this 10mm wide piece of O1 steel and started beating on it cold with a hammer. I got some amount of deformation, but it's not enough and it's hard going. It's not nearly a solid enough mounting for me to be beating on in earnest. I think I'm going to make a U shaped "inside form" as one of the articles someone linked shows and beat the gouges that way.

I also made myself a very nice maple/cherry/maple knife handle with some of the maple left over from the neck block of my first violin and some of the cherry I used to make my second violin's new mould. It turned out great and I'll be making the same handles for the gouges when I've got them done. I hope to make a matching set of gouges and knives (matching in terms of the handles).

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  • 10 years later...

This is an old thread, but useful to me as I am STILL working on the problem of how to cold-form flat O-1 steel into gouge curves.  I have used a 20 ton hydraulic press to form 3/32 inch steel. I was not sure 20 tons would do it, but no problem there.

 

So the next issue is how to make the lower die parts. After considering drill large diameter holes in 1 inch steel, I gave up that idea in favor of this one --  use concentric pipe sections.  For the upper die part, I will have to find some solid cylinders. For the smaller diameters, this should be easy. For the larger ones, say 3 inch diameter ones, well, I am exploring how to do that, short of getting a machine shop to do it.

 

In the fullness of time, I hope to be able to make these gouges.  I will report back as progress is made.  If anyone else is attempting this same project, I would like to talk with him/her.

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I love the small finger scrapers you made for me. I use them a lot. So, I am very interested in this project.

 

Mike

Mike,

 

Thanks for that. I am planning to make one large gouge for roughing, maybe 30 mm wide with a radius of about 37 mm. Then much tighter radius for edge fluting and scroll work.

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Why do you want to cold bend, John?  Usually fine grain steel tends to crystallize and potentially develop fractures when worked too quickly.

 

Bill,

 

I want to bend it cold because heating to red heat might cause loss of carbon.  Hey, I am certainly no steel expert. Just going on what I have read.  But you raise an interesting point. The one piece I tried seems to be ok, but of course I don't have any way to examine the microstructure.

 

In addition, I don't have a forge. But I do have a friend with a 20 ton press. B)

 

The scroll scrapers are pictured here, before final polishing.

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Chet Bishop could probably offer more info, but from what I know you won't burn the steel unless you heat it to a bright orange-yellow. You should be able to heat it hot enough for shaping with a MAP gas or acetylene torch.

 

After shaping, it just needs to be hardened, followed by drawing the temper.

 

The top two scrapers look almost identical to some I made a few years back. The only difference is I put a different radius on each end, so it's a double ended scraper.

 

I made sort of a similar hook shaped scraper from the stub end of an Olfa 1" blade. It works nicely for scrolls too.

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Bill,

 

I want to bend it cold because heating to red heat might cause loss of carbon.  Hey, I am certainly no steel expert. Just going on what I have read.  But you raise an interesting point. The one piece I tried seems to be ok, but of course I don't have any way to examine the microstructure.

 

In addition, I don't have a forge. But I do have a friend with a 20 ton press. B)

 

The scroll scrapers are pictured here, before final polishing.

 

Hi Violin88 - took a break from work and came pegboxxing...

 

- interesting comment about loss of carbon. Earlier in the posts you mentioned using charcoal and I made a note to warn you that by going that route you might be adding carbon to your steel!

 

Don't quite understand the problem myself - heat using a propane torch -  forge to curve - slight reheat to hardening colour - hold for about 5 minutes for full transition - quench. Takes less time than thinking about it.

 

There's no free oxygen inside the propane flame - so no decarburization.

 

An alternative for accurate work - such as a rifle chamber reamer - is to machine to a fraction of a gnat's b--l hair from final dimensions, then warm slightly while drizzling borax powder over the important end. Once completely coated with bubbling borax Raise temp colour to the required look - hold for about 5 minutes and plunge vertically into the quench medium and "freeze". Any waving around during quench will result in a banana shape. (Don't ask! However if anyone is planning on making a 0.270 WIn rifle for shooting against cross-winds I have a special reamer for you. Only works for winds blowing from left to right)

 

Comes out of the quench with a clean and silvery look - no scaling at all.

 

cheers edi

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 funny I thought that you were a part time blacksmith for some reason,  with your knife making and all, but there is lots of info on a site called  "I forge iron" , it does not take much to put together a simple forge ,  and you already know about the finishing process, it might be a fun new hobby for you with all the spare time you have !  

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 funny I thought that you were a part time blacksmith for some reason,  with your knife making and all, but there is lots of info on a site called  "I forge iron" , it does not take much to put together a simple forge ,  and you already know about the finishing process, it might be a fun new hobby for you with all the spare time you have !  

Actually, you are correct. I would love to be a blacksmith. My grandfather was a master machinist for the railroad.  Pounding red hot steel and working hot glass are things I would love to do.

 

Ed,

Thanks for the comments. I will try to do some tests.

 

When I was doing experiments with O-1 steel, I developed a sharpness test and found a heat treatment regime that really works for violin makers.  I control the temp. very precisely. Maybe the torch can do the same. I am sure in expert hands it could.

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Hi John you wrote - Maybe the torch can do the same. I am sure in expert hands it could.

 

Not sure that "expert" is what its about. The main problem is that you are not doing this on a daily basis - on the same type of steel - with the same torch. So there'll always be an element of hit and miss.

 

 

When making flat springs for old English shotguns I would make three springs.

 

Heat treat the first one and then test it by closing the spring with a pair of pliers. One of three things happened...

 

i) it snapped (now you know why you made three)

 

ii) it yielded and didn't return to it's original shape.

 

iii) it returned to its original shape.

 

If iii) happened you gave yourself a gold star and regretted the extra time spent making the other two blanks.

 

Most times the result was i) accompanied by a sharp crack and a sharp edged irregular shape flying around your ears. This tells you that you didn't temper it enough.

 

Rarely was ii) the result - for me at any rate - but it tells you two things - you didn't take it to a high enough temperature before quenching or you tempered at too high a temperature.

 

OK - now you have carried out a calibration test of your "flame generator, behaviour of the steel, temper-colour technique" - grab no 2 and adjust your technique according to the results of test No 1.

 

This usually gives you a working spring. You rejoice and do no 3 immediately.

 

Now you also have a spare.

 

cheers edi

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The top two scrapers look almost identical to some I made a few years back. The only difference is I put a different radius on each end, so it's a double ended scraper.

 

I made sort of a similar hook shaped scraper from the stub end of an Olfa 1" blade. It works nicely for scrolls too.

Here's the ones I made. Interesting that we arrived at very similar shapes.

post-24795-0-94439800-1417491493_thumb.jpg

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