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Working an inside a radius


C Craft

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What does everyone do when working an inside radius??? So here is what I have been using.

 

e2629e08-08b7-438e-9edf-d93980584375_145 Or at  least something similar! However my complaint is that they usually last about as long as it takes to change the sanding drum. Maybe I am leaning on them too much but they seem not to last long at all. The grit is gone and the cutting ability is done! I

have tried metal cutting burrs, similar to these,  and in a  couple of minutes they are done!

Image result for metal burr They do not seem to be designed for thicker metal, say than sheet metal. 

So back to the question what are you using to work an inside radius on thicker metal such as a knife blank???

 

Edited by C Craft

C Craft Customs ~~~ With every custom knife I build I try to accomplish three things. I want that knife to look so good you just have to pick it up, feel so good in your hand you can't wait to try it, and once you use it, you never want to put it down ! If I capture those three factors in each knife I build, I am assured the knife will become a piece that is used and treasured by its owner! ~~~ C Craft

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I free hand on my 2x72 using 1" belts. I cut a 2" in two. Works very well.

”Whoever pursues righteousness and love finds life, prosperity, and honor!”

 

George Brackett

American Bladesmith's Society,

Apprentice Member

Hialeah, Florida

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What I use is a plain rod with a slit lengthwise, through which I can insert a strip of sandpaper. As it it spins, the paper curls around the shaft, in the proper orientation. Of course, it's not something that's precise so it's better for the inside of soft curves such as a finger ring. 

Edited by Caleb Harris
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Trying to make each knife just a little better than the last

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Well I was hoping for more advice but thanks for those who replied! I was kind of wondering if someone made some of the drum sanders with better grit! Or I have seen diamond hones but don't think those would very cost effective!!

C Craft Customs ~~~ With every custom knife I build I try to accomplish three things. I want that knife to look so good you just have to pick it up, feel so good in your hand you can't wait to try it, and once you use it, you never want to put it down ! If I capture those three factors in each knife I build, I am assured the knife will become a piece that is used and treasured by its owner! ~~~ C Craft

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I use a small wheel holder on my 2x72.  I have a tool ark with it attached.  You can get different radius wheels as well.  This is where I got it from.

“In the midst of winter, I found there was, within me, an invincible summer."  -Albert Camus

http://www.krakenforge.net/

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Im in the same boat as you C Craft.

 small wheel attatchment, the drum sanders are rubbish as are small flap wheels.

 Not all carbide tools are equal,you definatly get what you pay for.  A 6mm (or 1/4 inch) shanked die grinder and decent (spendy) carbide tools will rip through hardned and whole sale eat unherdned steel , but they are one of the most unpleasent tools to use.

I find that a lot of radiuses I use are the same as the small wheels I have for the belt sander...

forging soul in to steel

 

owenbush.co.uk

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I just dread inside curves smaller than the 4" contact wheel on my grinder. I get as close as I can with a grinding wheel on the angle grinder, but mostly end up using files for shaping. Afterward I'll use one of those sanding drums to clean it up a bit and get a regular scratch pattern. 

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files and paper...

Jake Cleland - Skye Knives

www.knifemaker.co.uk

"We can't solve problems by using the same kind of thinking we used when we created them."

"Everything should be made as simple as possible, but not simpler."

"Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."

 

Albert Einstein

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21 minutes ago, jake cleland said:

files and paper...

Yep.  Did you know you can drawfile with a chainsaw file?  Makes it a little faster to step between big files and paper.

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Thanks everyone!

C Craft Customs ~~~ With every custom knife I build I try to accomplish three things. I want that knife to look so good you just have to pick it up, feel so good in your hand you can't wait to try it, and once you use it, you never want to put it down ! If I capture those three factors in each knife I build, I am assured the knife will become a piece that is used and treasured by its owner! ~~~ C Craft

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4 hours ago, Jon Cook said:

Would it be too much to ask a grinder belt to flex around a sub-1" contact wheel?

Asking for a friend. . .

You are essentially talking about a small wheel holder.  I have 5 small wheels that are under 1 inch.  X weight and J weight flex around them just fine.

“In the midst of winter, I found there was, within me, an invincible summer."  -Albert Camus

http://www.krakenforge.net/

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29 minutes ago, Wes Detrick said:

You are essentially talking about a small wheel holder.  I have 5 small wheels that are under 1 inch.  X weight and J weight flex around them just fine.

Awesome. I knew I'd seen something to that effect, but I couldn't remember the scale.

It's great to know I can skip sanding drums once I get a big boy grinder. 

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Jon, take a look at the link Wes provided, https://www.knifegrinderparts.com/collections/small-wheels

Anything can be overcome with enough money or the ability to fabricate yourself!! LOL Got to love this obsession. I work in the shop and I say, God when I die please don't let my wife sell my tools for what she thinks I got in them!!!  :jawdrop:   :s12137:

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C Craft Customs ~~~ With every custom knife I build I try to accomplish three things. I want that knife to look so good you just have to pick it up, feel so good in your hand you can't wait to try it, and once you use it, you never want to put it down ! If I capture those three factors in each knife I build, I am assured the knife will become a piece that is used and treasured by its owner! ~~~ C Craft

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34 minutes ago, C Craft said:

Anything can be overcome with enough money or the ability to fabricate yourself!! 

Truer words never spoken :)

“In the midst of winter, I found there was, within me, an invincible summer."  -Albert Camus

http://www.krakenforge.net/

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Here's a possible solution to those quickly worn Dremel brand drums:

 

You could use zirconia or ceramic and probably have some nice drums.

Has anybody tried this?

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You can get Ceramic grit drums for those smaller mandrels, but I've never found any Zirconia or ceramic alumina drums for those bigger sizes like the ones you could mount in a drill press chuck. I've tried the red AO drums, but they're made for wood and AO wears out too quick and gets too hot on steel. Plus they mostly come in 100-220 grit, not ideal for anything but cleaning up scratches. You would need a barrel full to get any work done.

The KMG small wheel attachment is OK for some things, but for shaping in a sub-hilt for example, it's no good due to the belt angle.

I prefer this style, where the belt goes under the forward contact wheel. 

smallwheel1.jpg

Or the Burr King style:

965attach.jpg

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17 hours ago, C Craft said:

Jon, take a look at the link Wes provided, https://www.knifegrinderparts.com/collections/small-wheels

Anything can be overcome with enough money or the ability to fabricate yourself!!

I'm not opposed to some mad scientist shenanigans. 3D printer, anyone? Either abs parts, or casting forms.

And how insane would it be too mount a lathe chuck off the side of a 2x72 with a vfd? 

I'm probably going to try those diy drums at some point.

It's all about investing in efficiency for me.

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1 hour ago, Brian Madigan said:

Those small wheels are super easy to make yourself. .. if you have a lathe :)

3D printed wheels? They wouldn't last as long, but no lathe required. Might be worth it if you have easy access.

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5 hours ago, Jon Cook said:

3D printed wheels? They wouldn't last as long, but no lathe required. Might be worth it if you have easy access.

I don't know that I would suggest this.  Plastic wheels would eventually fail structurally and there is no way in hell I want a 50 grit belt coming around to slap the piss out of me.  Food for thought. 

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“In the midst of winter, I found there was, within me, an invincible summer."  -Albert Camus

http://www.krakenforge.net/

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I get things close on the belt sander, then perfect the shape with drums either on a router or dremel.  One of the keys to getting the most life out of the drums is to keep it moving and use the entire width... And buy them in bulk....

George Ezell, bladesmith

" How much useful knowledge is lost by the scattered forms in which it is ushered to the world! How many solitary students spend half their lives in making discoveries which had been perfected a century before their time, for want of a condensed exhibition of what is known."
Buffon


view some of my work

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These are available with .25" and .125" shafts.  

 

https://www.google.com/search?q=mounted+points+grinding&rlz=1C1SAVS_enUS546US601&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjEmtDIxuXTAhVMxoMKHUE2AMsQ_AUICygC&biw=1920&bih=901

 

Also, are you removing scale before you attempt to shape the inside radius?

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The small diameter bands on the rubber drums need to be run fast. Maximum speed for a 25mm x 25mm (1" x 1") Spiraband is 24000 RPM and they seem to like being close to that speed.

Metal removal rate is tediously slow and their life (in minutes) seems no longer (possibly shorter) when run at drill speeds.

They are really intended for use in die grinders, though I have used a cheap import trim router to spin them quite successfully.

Even at the correct speed, they'll never last well compared to a small wheel attachment on a 2 x 72: a 1" Spiraband is about 3" long so there's 18 times the abrasive surface on a 72" belt.

Edited by timgunn
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