New Drag Knife

[Cosmos275]

Got a new one out.

About half the price of the leading brand and some cool features of it's own. Unique construction with single piece solid AL body, 2 double sealed bearing. It uses #19 Heavy Duty X-Acto blades which are the same thickness as utility blades (.025") and inexpensive (couple bucks for a 5 pk.). Blade change is easy and blade is located into position with dowels.

Cuts 1/8" material, offset is 3.0 (~1/8")

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Up on my website: http://cosmos-industrial.com/index.php?main_page=product_info&cPath=3&products_id=20

You Tube video: https://youtu.be/GN1rOmmPcW8

[Thomas Cook]

What's the min radius your able to achieve with this design? Great price so I'm pretty interested.

[gundog]

Looks like a nice design.

[Burkhardt]

Looks good. What I did not see in the video was if the knife is somehow spring loaded or if it is fixed height.

[coryatjohn]

It's probably fixed height. I don't see what good a spring loaded version would be. The height is at the table and anything it runs across (up to .125") is sliced. If it had a spring loaded action, it wouldn't penetrate all the way through the material to be cut.

[myxpykalix]

If anyone buys this i hope you would give us a report on it's quality

[Cosmos275]

Sorry for the delay... auto emails not coming in.

The offset is 3.0mm which is also then the max material and your min radius.

Vectic VCarve Pro and Aspire has a gadget for programming drag knife toolpaths which can do some interesting stuff to optimize the moves.

I picked an offset of 3.0mm (~1/8") as I thought it would cover most needs. I can make one with a smaller offset if you want. I can also modify the design so you can tweak the blade position. Right now, it goes right in to the one position with little wiggle room. I could add wiggle room, but you'd have to pay more attention when setting it up.

Thanks for your interest.

[Cosmos275]

It is fixed height. You want a flat spoilboard under what you're cutting.

I've actually designed up a spring loaded version for a company that makes boat covers. Their machine table are 20-30' long, so they need it to track with the table height. It adds length, which in their case isn't an issue, but probably would be on a CNC router.

Also, if you spring load it, it may go deeper than you want. If you go past the max thickness, it won't corner right or at all.

[919RickR]

Is there any special software needed? What is the smallest radius that it will cut
I watched the videos and on web site no specifics were mentioned about this tool.
I'm interested also
Rick

[Cosmos275]

More thoughts on the design:

For drag knives that are made for use with utility or X-Acto blades (most of them), there are a few defining features:

1. bearing for spin (some would argue the spindle bearing may be enough, but why chance it)
2. blade cutting edge at 45 degrees
3. distance of blade support from tip
4. rigidity of overall device.
5. offset (dictates material thickness and min radius as well)

My design is the same as all the other on #1 and #2. I’m using an X-Acto blade as they are inexpensive and the tip geometry doesn’t vary with many different brands like utility blades.

#3 and #4 are where all the design is and what makes mine different.

On #3, I have the solid AL body taper out to 4.0mm from the tip, so the blade is very well supported. This is important such that when cornering, the device spins instead of just bending the blade.

On #4, I have a solid AL one-piece body design and the blade is locked into position with 2 bolts. It is very solid and there is no play whatsoever.

#5 is just a choice. Because the blade angle is 45 degrees, if you cut more material than your offset, then try to corner, the leading edge of the cutter will have to go backwards to make the corner, hence this is your limit. I picked a middle of the road value, but as I mentioned, I can work with you if you want something different. There are tradeoffs. A smaller offset will allow more intricate work, but mean thinner material and probably means going slower too. My video is very fast (even before speeding up the film) but I’m only cutting card stock.

[Cosmos275]

Rick, here are the specs (copied from site)
Features:

#19 heavy duty Exacto(TM) blade.
Two double sealed bearing rated for 310 static / 750 dynamic pounds radial load
Hardened steel 3/8" shank
Drag offset is 3.0mm
Max material thickness: 3.0mm
Min radius: 3.0mm
Length from collet: 72mm (2.84")
Kit comes with a pack of 5 blades and hex key

Vectric VCarve Pro and Aspire have a "Drag Knife" gadget that can do some cool things for calculating toolpaths. You can use it without that software, but I need to do some research on what the specifics are. Basically, with the spindle off, you can run a profile toolpath and observe where it starts and adjust the blade starting angle manually. When going for more than one profile, you have to be aware of the blade angle, which is what the vectric software does (very cool)

[markevans]

Any chance of a 1/4" shank?

[Cosmos275]

Yes. I went with 3/8" to be as stiff/robust as possible, but I think a 1/4" steel shank will do well also. If you order one, just put in the comments you want 1/4" shank. At some point, I'll set that up as an option.

[Cosmos275]

Here are some notes on programming the drag knife and some test photos

I was sent an image of a letter by a customer trying to get the drag knife going on small letters in thin vinyl. There had been some discussion of bearing drag, but I think the speed has more to do it at this point. The letter “E” was cut at 75IPM

I test cut a couple letters of the same size on a piece of paper (didn’t have any thin vinyl on hand).

You can see the letters “A” and “T” in the other two pictures. They came out pretty good for a 3mm offset tool. I do plan to come out with a 1.5mm offset tool soon (geared towards smaller work).

Programming notes:
The speed I ran was 12 IPM (1/6th the speed of the bad quality letter)
Cut depth was .13mm (.0051”)
Pivot depth was .12mm (.0047”)

I did some manual edits of the G code to remove the first pivot and the last pivot generated by Vectric’s Drag Knife Gadget. I noted the initial blade direction and set that manually before starting. With that, removing the first and last pivot eliminated some small damage the pivots do at the start and end.

So I think the main takeaway is for small details like letters, you must go slow. This allows the device time to pivot. Freeling up the bearing may help, but still, slower will give better results (if you already bought one, talk to me about making the bearings spin more free. New units will ship with this modification). The other takeaway is the Drag Knife Gadget in Vcarve is a good start, but isn’t perfect. It can be cleaned up doing some manual G code edits.

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[joe]

Very interesting tool. My complements!

Why is it called a Drag Knife Cutter? Most of us old hands know vinyl cutters are true drag knifes and the original tangential cutter like Gerger 4B moved in the same way at this one. When cutting thick materials like Sandblast Mask this is the way to go.

With concern about spring loaded: This is a novice question. OK here's a case, When cutting sandblast mask on a large rough cedar panel, you need some spring action in the blade. With this kind of work you wouldn't want to destroy the surface texture by surfacing.

When using SB mask it's sometimes best to make two or three passes. That's because the rubber can stiffen up when the temp drops. The reverse is so during the summer. All my masks,for this kind of work, was done with a Brad Point Roundover bit. I've posted on this topic several times. Today, on this forum, there are so few people sandblasting it's probably not worth considering.

http://www.talkshopbot.com/forum/attachment.php?attachmentid=27748&stc=1

[Cosmos275]

Some other concerns, as I see it, with a spring loaded design would be there's nothing preventing the blade from going deeper than planned. This could cause problems cornering or possibly just bogging down. For the most part, you can just cut into your spoilboard a little, so I'm not sure the added complexity it worth it.

[joe]

Cosmos 275. who ever that is,

You might be right about bogging down. When I'm cutting SB mask with a Brad Point bit I find it an advantage to go through the mask a little. Because you never know if the wood has a devit or two.

Sure like the tangential moves this knife makes but there is no dragging involved. It's under power at all times.http://www.talkshopbot.com/forum/attachment.php?attachmentid=27749&stc=1

[Cosmos275]

Cosmos is my first name :) Life story located here: link (http://cosmos-industrial.com/index.php?main_page=about_us&zenid=h47lkbgra15igbm9gf29p38aa7)

Ran some 1/16" rubber gasket material today. Easy. Tomorrow, I'd do some thick cardboard.

https://youtu.be/AEqYhbeKc6A

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[8Ball]

I'm looking for a diamond drag tool holder. Could this be modified to be a spring loaded diamond drag tool holder?
I would be very interested in one.

[Cosmos275]

This one is not spring loaded, just to be clear. I'm confused. I've seen diamond bits for engraving.. I'm not sure why you'd need to drag it.

[jerry_stanek]

I have the widgetworks diamond drag tool and use it to etch mirrors and metal objects by just dragging it across the surface on spindle on

[8Ball]

Tormach has one for $110 less at $69. The problem is it has a 3/4" shaft and my router won't accommodate that diameter.
I have found a few others for less than $100 and I've even considered making my own. It would just be simpler to purchase one at this time.

Some of the drag tools say they can be rotated while cutting, but most do not recommend it. I don't believe rotating a diamond will result in any better cut than dragging it across the surface.
There are a lot of videos showing the drag cut and it is very sharp and detailed.

[joe]

I'm impressed with the Cosmos tool. If I were you I'd give it a try. I'd bet they would gladly be willing to give you a refund if it didn't do what they are saying.

What kind of work are you doing? What kind of masking material are you needing to cut? I'd bet there are guys on this forum who could give advice.

Here's a most important question. Will it make you money? If so, it's nickels and dimes. I've had several custom made costing more. And as everyone knows bits can quickly loose their edge.


Attached is a photo of a panel with rubber sandblast mask. When blasting hardwood like this Yellow Pine it's necessary to have a tough mask. We apply the mask directly and cut it on the wood. I like cutting the resist a little extra deep.

http://www.talkshopbot.com/forum/attachment.php?attachmentid=27834&stc=1

[Cosmos275]

These are two very different products. Diamond engraving and a drag knife like mine are for very different things.

A typical Drag Knife like mine adds capability to your machine. You can slice up gaskets, cardboard, cardstock and the like easily that would be very time consuming and difficult with an end mill. If you want to do super fine very shallow cuts, it's not the optimal tool, and there are some smaller ones out there like widgets, but those won't do any sort of thickness. If you want to make vinyl signs, you're better off buying a vinyl cutting machine.

If you want, I can design a spring loaded holder for a Dremel 9929 bit (diamond engraving). I can easily beat widget's price. info@cosmos-industrial.com

[Davo]

What causes the lines going across?

[joe]

Davo,

Are you not familiar with Sandblasted Signs?

This one was made several years ago. It's back in the shop for a repaint. The wood has help up well.

With the last post Cosmos has informed us about the optimal products to cut with his tool. I'm in full agreement about cutting vinyl. A plotter is a much preferred method however for cutting thicker products like stencil materials his knife will do a better job. Not too sure about SB mask. That material has always been more difficult.

http://www.talkshopbot.com/forum/attachment.php?attachmentid=27842&stc=1

[Cosmos275]

I was sent some sandblast material. I will cut here in the next day or two and report on it. I think it will be easy. The gasket material I cut seems just as tough.

I think Dave is asking about the wavy texture you have cut into the background.

[Davo]

Yea I have zero clue about sandblasting but wouldn't mind learning

But was curious about the wave background pattern and how that's accomplished

[joe]

OK, Here's a quick description.

I didn't carve the wavy grain. That a function of choosing the wood. The boards are chosen for their vertical grain. The sandblasting takes out the soft wood, leaving the wood grain standing. The thing about cutting SB mask is it's stiffness. During the winter, because it's rubber, you will have to make more than one slow pass. For that reason I apply the mask directly to the wood and then cut it.

Sandblasting isn't anything you guys will end up doing. It' dangerous, time consuming and not worth the effort. That work should be farmed out.

http://www.talkshopbot.com/forum/attachment.php?attachmentid=27849&stc=1

[Cosmos275]

Cut some sand blast mask. This was Anchor 1.1mm sand blast mask. It cut easily, one pass, maybe 60 degrees in the shop.
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[joe]

Cosmos,

What you've tested is Anchor's lightest resist. SB resists come in lots of thicknesses supported by different adhesives. Blasting on glass isn't nearly as demanding as stone or wood. Wood is much tougher than stone. What you cut was the lightest. It's made for hand cutting. If you check Anchor's list of products I think you'll see lots of options. I think they offer about thirty different types.

Another excellent resist is Hartco. It's a little tougher material to cut but stands up to blasting much better. It's a heart break to go to all the work for blasting and have it fail. That's the norm when getting into this business.

I'm sure your knife will cut mask of this type but it may take several passes. I like lots of passes since it guarantee's a complete cut.

http://www.hartcoservice.com/sandmask

[Cosmos275]

Joe, when you used that stuff, how did you hold it down when cutting? Vacuum table?

[joe]

No hold down necessary. The mask is installed directly on the wood. That's where all the cutting and routing takes place. For years I cut the mask on a plotter then transferred it. What a waste of time. O, I may have forgot to mention we cut the mask with a bradpoint router bit. The depth of cut is only .125.

http://www.talkshopbot.com/forum/attachment.php?attachmentid=27852&stc=1

[Cosmos275]

Oh right.. it's on the wood.

[Cosmos275]

The Drag Knife is back. It was discontinued for a couple years do to a shop move and some other things. It's back in 7075 and gray ano. 3 different offsets available.

Thanks!

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https://cosmos-industrial.com/index.php?main_page=index&cPath=4

[Cosmos275]

Got a new one out:

Adjustable Offset Drag Knife (https://cosmos-industrial.com/index.php?main_page=product_info&cPath=4&products_id=61)

https://cosmos-industrial.com/images/3005-300.JPG

Adjustable Offset: 2-12mm (~1/16 - 1/2”)
Blades: Any standard sized utility blade. This lets you use HSS, Tin coated or Carbide edged blades.
Set screw is used to recall offset position between blade changes.
Body: Gray anodized 7075 Aluminum (high strength). 62.3mm long (not including blade stick out)
Bearings: Dual 7/8” diameter ball bearings offer best balance between radial load capacity and minimal overall length
Shank: Hardened steel 3/8”. 36.2mm length.
Clamp: 303 stainless steel. M5 bolt


https://www.youtube.com/watch?v=ETAtPFRSulI

Made in Fort Worth, TX
Days to ship: 1-2 (usually same day)

[khaos]

Love the simplicity of the design.

[Mike Windsor]

Have you tried cutting 3mm coreplast ? ---I cut a lot of that for a local sign shop with a 1/8" spiral end mill. the chips are very clingy and the dust collection is never 100 percent effective . I'd love to do it with a drag knife , but wonder what would happen when it went against the ribs at an angle in the coreplast ?

[Cosmos275]

I have some on hand but might be thicker. I will try to fit in a test this week. I'd think you could dig in extra to the spoilboard to keep it straight.

[Mike Windsor]

It might be 4 mm that I cut
I'd definitely be interested in the drag knife if it could cut it

[Cosmos275]

It might be 4 mm that I cut
I'd definitely be interested in the drag knife if it could cut it

It does alright, but not the ideal material for sure. The stuff I have is 4mm. I cut this diamond shape out (8" pt. to pt.), so the edges are at 45 degrees to the grain. The edges are pretty straight. I was just on double sided tape on a metal plate, so I wasn't able to dig into the MDF for any help. That should help. Also, the drag knife gadget tears a little on exit which I did not attempt the clean up in the code.

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