Milling CF

[Chris*33]

Hello,

My question is not directly knife-making related, but the thread looks appropriate, let me know if this is not the place.
I am planning on making some folder accessories from CF (clips/backspacers/scales), but before spending my money on a mill bit and a steadier collet i would appreciate any input from experienced members.
My main goal here is to get the CF scales to the desired thickness, and not any fancy machining. After that, i will shape & finish the part using a small belt grinder, a dremel and hand tools.

I'll be using my bench drill (i know it's not the tool for the job, but let's leave this out for now as i can't afford a mill at the moment) which goes up to 2450 rpm.
Apparently, that's quite low for CF, but i've read that it should be enough if i'll be using a larger bit (0.4/0.5").

Also, do you think i could use a router with a carbide flash trim to get the CF to the shape of an existing scale?
In this case i would be using an actual router so no problem on the rpm, here. You think the CF would respond well to the carbide bit?


Any thoughts/suggestions on the processes i have described would be greatly appreciated!

 

[navman]

Sharp carbide is the ONLY way to go for carbon fiber. CF is very abrasive and will wear tooling quickly. Wear the proper PPE at all times while working CF (Full face mask would be best), long sleeves and disposable gloves.

HSS may work for one or two pieces, but will likely lead to a poor finish and tear out.

 

[Daniel Fairly Knives]

You can do it! CF is really easy to work with, just very dangerous (think asbestos level) and super hard on tooling. It grinds crazy fast with ceramic belts like butter, hand sanding also goes fast. I like to do my sanding in a bucket of water under the water.

No advice on the router, I use a few for making guitars and think they are sketchy. I think you would spend a lot of money on bits. It should be easy to run on a router table with a premade thick template to follow.

No tools and silly cheap budget? buy a drill press and 1x30 grinder... drill and shape, hand sand to finish. Use regular cobalt bits, for a little more maybe get a mini drill press for under 100 as they run really high rpm for cheap and are great for carbide which you will run on it. Running carbide with a lot of runout on a cheap press will just break bits.

Slightly better budget - get one of those 1018 mini cnc routers if you have time to mess with it, learn cad/cam. They are super fun and cheap.

 

[Chris*33]

Sharp carbide is the ONLY way to go for carbon fiber. CF is very abrasive and will wear tooling quickly. Wear the proper PPE at all times while working CF (Full face mask would be best), long sleeves and disposable gloves.

HSS may work for one or two pieces, but will likely lead to a poor finish and tear out.

The PPE guidelines are appreciated and will be strictly followed, i assure you! Do you think that the 2450rpm will be OK with a larger size bit, as i've described above?

You can do it! CF is really easy to work with, just very dangerous (think asbestos level) and super hard on tooling. It grinds crazy fast with ceramic belts like butter, hand sanding also goes fast. I like to do my sanding in a bucket of water under the water.

No advice on the router, I use a few for making guitars and think they are sketchy. I think you would spend a lot of money on bits. It should be easy to run on a router table with a premade thick template to follow.

No tools and silly cheap budget? buy a drill press and 1x30 grinder... drill and shape, hand sand to finish. Use regular cobalt bits, for a little more maybe get a mini drill press for under 100 as they run really high rpm for cheap and are great for carbide which you will run on it. Running carbide with a lot of runout on a cheap press will just break bits.

Slightly better budget - get one of those 1018 mini cnc routers if you have time to mess with it, learn cad/cam. They are super fun and cheap.

I appreciate the input, the underwater sanding should make it much safer i take it, since no dust will be be created to get airborne.

Two problems with buying machines for me: i live on a small island (Cyprus in the EU) where you can't really find machines like that -or any type of machines suitable for knife making such as belt grinders, disk sanders, drill mills, etc, so even if i buy something from within the EU the shipping is actually killing me (being an island i mean). I was lucky enough to find a local guy who made a homemade 2x60 belt grinder because he wanted to try to forge-weld steel, and after a knife or two he decided to sell it. So any purchases without trying it out first our out of the picture at this moment.

 

[JV Knives]

An added tip is to select an end mill designed for "composite" material. Google makes that easy to find. The design of the flutes and cutting edges are optimized for cutting composite plastics, such as carbon fiber. Don't worry too much about your spindle speed limitations as you can somewhat compensate by reducing your feed rates. (Speed + feed) / cutting edges = chip load. If you can hit close to the optimal chip load then the only thing that will be reduced by your spindle speed limitation is the time it takes to perform the cut.

Finally, if cost is a consideration (it always is), spend your money on the right breathing PPE. As others have said, carbon fiber is no joke and the dust will do short and long term damage. You don't want lungs full of that crud or you will have a bad few days to remind you not to do it again. Good luck!

 

[Chris*33]

An added tip is to select an end mill designed for "composite" material. Google makes that easy to find. The design of the flutes and cutting edges are optimized for cutting composite plastics, such as carbon fiber. Don't worry too much about your spindle speed limitations as you can somewhat compensate by reducing your feed rates. (Speed + feed) / cutting edges = chip load. If you can hit close to the optimal chip load then the only thing that will be reduced by your spindle speed limitation is the time it takes to perform the cut.

Finally, if cost is a consideration (it always is), spend your money on the right breathing PPE. As others have said, carbon fiber is no joke and the dust will do short and long term damage. You don't want lungs full of that crud or you will have a bad few days to remind you not to do it again. Good luck!

Appreciated!

 

[navman]

not really the speed that I would be worried about, more the rigidity of the overall set-up. The reason a mill is recommended is because the colum/quill is more rigid and can stand up to side load required for milling. While it may not be an issue in a "softer" material like CF, it may lead to some destroyed projects because of chatter, flexing , etc. When machining materials speeds are a part of the equation, FEED rate is the other.

edit: just saw JV addressed it.

 

[Chris*33]

not really the speed that I would be worried about, more the rigidity of the overall set-up. The reason a mill is recommended is because the colum/quill is more rigid and can stand up to side load required for milling. While it may not be an issue in a "softer" material like CF, it may lead to some destroyed projects because of chatter, flexing , etc. When machining materials speeds are a part of the equation, FEED rate is the other.

edit: just saw JV addressed it.

I agree with you but no other option at the moment. I'll experiment on scrap pieces from hard wood laminates/G10/ micarta whatever i can find to see if it can be done smoothly (as possible..) and find the appropriate feed rate, then.
Thank you for your input navman

 

[navman]

Just food for thought: I started with a bench-top mill/drill from Sieg (many of them are rebranded as Grizzly, HF, LMS...) and it was perfectly adequate. I eventually sold it and bought a J-head Shop Fow, but that was more for gunsmithing.

 

[Chris*33]

Just food for thought: I started with a bench-top mill/drill from Sieg (many of them are rebranded as Grizzly, HF, LMS...) and it was perfectly adequate. I eventually sold it and bought a J-head Shop Fow, but that was more for gunsmithing.

Sieg is the brand that i've come across quite a few items as far as budget mill drills go, actually. They still start from 450 euros (510 USD) which is good for an entry level machine i guess, but still a considerable investment for the time being. If i do like the process and decide to take the next step i'll be getting a slightly better model from the get-go (still from sieg), maybe at 750USD more or less, since it would be more more stable, powerful, with a larger work area and also with a brushless motor, and most importantly, at that point i would really know that it will be an investment and not an experiment!

 

[C_Claycomb]

Okay, I haven't seen anyone raise this, so maybe I am missing something.

....
My main goal here is to get the CF scales to the desired thickness, and not any fancy machining. After that, i will shape & finish the part using a small belt grinder, a dremel and hand tools.
...

How exactly are you going to control cut depth (that gives you what you hope is the desired thickness), and how are you going to be feeding into the cutter?

Drilling in laminates, especially G10, has shown me that constant pressure does not equal constant cutting. The cut depth jumps when the bit passes through one layer of glass and is cutting mostly just epoxy between layers. Without rigid vertical control, I would expect this to affect finished part thickness. My drill press has a scale on the side that allows me to track how far I pull the handle, so can be fairly consistent for hole depth, but that is not the same as the sort of accuracy needed for aftermarket back spacers.

Feeding by hand isn't a good idea.

What is your plan?

All the best

Chris (too )

 

[Chris*33]

Hey Chris, thanks for the feedback!

I understand your point, and i'm sure i'll struggle with tolerances for quite a few reasons, but would i face the same problem with milling? I can see why the thickness "jumps" when drilling such a material since you come at it vertically through the layers, but when coming from the side, and if the feed is slow enough to give the bit time to do the job regardless if it's epoxy or glass, wouldn't it eliminate such an issue?

The plan is to make a custom stand that goes all the way up to the bit, so i can use the drill in its retracted position at all times, anyway.
The frame will be done from mild steel, with a wooden top, which will have two t-tracks running parallel to each other. The t-tracks will hold another rectangular piece of wood, bolted on all 4 corners on the t-tracks, for stability.
Finally, a machining vice will be bolted on that second wooden piece, again on t-tracks and on all 4 corners, but the tracks here will be running perpendicular to the lower level, so i can work in two dimensions (each board will run a different axis, x/y). All the the bolt screws will have a knob for faster adjustment.
The actual feed it will be done manually by moving the boards along the tracks using a couple of knobs, probably.

Due to the inherent imprecision of the whole build, i'm not planning to get it all the way to the desired thickness, but i will leave some extra material just enough to be able to sand it down by hand, which would allow me to fine-tune the thickness and also leave a nicer finish.
Now, to adjust the height on my work rest, to compensate for different sizes of material thickness or desired thickness, i can use washers or extra nuts underneath the vice (the height of the base will be all the way to the bit so only small adjustment would have to be made).

Other thoughts:
- I thought of building either the whole base or the vice onto a car lifting jack, if i can find a spare, old one.
- Another direction would be to bolt the whole wooden top construction onto the existing rest of the drill, and cut off part of the vertical tube stand of the drill to bring the work rest to the same height as the bit in the retracted height.
I do feel, though, that a custom base bolted on the same bench as the drill would be steadier and more accurate (given that it's built to be 90 degrees to the bit)

*Keep in mind that i do not plan on making this my full-time job, it's rather something i enjoy and it wouldn't hurt if i could make some money off it.
As long as i'm clear that everything is hand made without cnc and fancy equipment, thus no tight tolerances and the pricing is competitive enough to reflect that, i feel that i could sell a few parts. I would (and i have done so many times) certainly buy something at a good price even if it has a minor defect, as long as it doesn't mess with any mechanical properties or intended use of the product.



Not a native english speaker, so i hope i've explained this clearly

 

[C_Claycomb]

Very clear explanation.

What handle material starting thickness are you limited to? What is stopping you from getting a range of thicknesses?

That all sounds very complicated and like you could spend a lot of time working on the tool.

I have often spent a lot of time and money pursuing an idea first conceived as a way to save money…and in the end not got the results I hoped for.

it might be more efficient in the long run to spend a bit more money at the start to get material closer to sizes you want, so you need only sand to final thickness.

For reducing stabilized wood scales to thickness, and making parallel, I use a plunge router and a frame around the material that is thicker than the wood to be thinned. Wood is held down with masking tape and cyanoacrylate glue.

 

[Chris*33]

There are folders that have a main titanium scale/liner with an thin scale/overlay of another material on top (such as the ZT0393, ZT0640, ZT0562.... Spyd. Bradley seems to be built that way -which is one of my next knives- and all these are among my favorite designs) have a very thin scale/overlay on top of the actual titanium scale/liner and i can't find such thin CF.
In order to use a thicker stock as an overlay i would need to source longer screws, and i already got bored just by writing "longer screws", so it's not something i want to deal with.

Most other models i have available to work with, are close to a thickness that is available on the market, so no problem there. These can be sanded down easily by hand.
You could say that i could leave the aforementioned models out of my plans, but i want to enjoy what i do, and working with knives i like, is a part of that.

All that being said, i do understand the points you make and the possible limitations ahead (machinists and craftsmen that went through such procedures laugh here ), and i will be starting with projects that would only require some sanding down of the material, while working at the platform at the same time. I'll get there, i believe

 

[C_Claycomb]

Thank for the explanation! I wish you all the luck in the world. I am still curious about the thickness you need and what you can get. Is shipping to Cyprus from the UK and elsewhere difficult? I have some 3mm crimped fibre sheet that I got in a trade, horrible splintery stuff, and haven’t tried carbon since. I have worn down end mills on G10 and carbon is by all accounts more abrasive. So I don’t have a “source”.
However, in the UK, if I look on eBay, I can find multiple people selling carbon fibre from 0.5mm to 5mm, in 0.5 and 1mm steps.

Another thought. Have you considered laminating very thin carbon fibre with colored G10 (Alpha Knife Supplies in the US has a lot for liners and spacers)? Could get some interesting effects.

All the best. Looking forward to seeing photos, whether of the machine of the finished knife scales.

Chris

 

[Chris*33]

Importing from anywhere outside the EU does incur extra charges. Alpha Knife Supplies is on my radar, actually, they have a great selection of materials.
I can find 0.125" thickness material from camocarbon (which is still thick considering that the 0562 scale, for instance, is 2.4 mm) but i would prefer to source something from the EU.
The laminating process is interesting, given that i decide to order from outside the EU, i'll keep it in mind.

Thank you very much for your thoughts and input Chris, i really appreciate it. Here are a few pics from my latest project, done for myself alone (my very first backspacer!):

 

[C_Claycomb]

Nice looking back spacer. The red looks good in there.

I had another look on eBay. AHLtec Leonhardt. Based in Germany. Might be worth a look. 2.5mm twill material….and forged fibre

 

[Drew Riley]

I'd probably re-think the drill press as a means for doing anything much more than drilling.
If you already have a wood router, get the largest endmill it will hold, and make your self a flattening sled for your router. I'd even look into something like a surfacing bit with some indexable carbide blades. You can likely get one around 1-1/2" to 2" diameter that will fit your router, especially if it takes up to 1/2" bits.

If you don't know what I'm talking about, you can find a kinds of examples on youtube. Here's one that came up that shows a couple of options:

 

[Chris*33]

I'd probably re-think the drill press as a means for doing anything much more than drilling.
If you already have a wood router, get the largest endmill it will hold, and make your self a flattening sled for your router. I'd even look into something like a surfacing bit with some indexable carbide blades. You can likely get one around 1-1/2" to 2" diameter that will fit your router, especially if it takes up to 1/2" bits.

If you don't know what I'm talking about, you can find a kinds of examples on youtube. Here's one that came up that shows a couple of options:

It's funny that you propose this now, as i have decided to make a base similar to the one in the video, so like a 3D router base.
After a few calculation regarding chip load, it seems that 2450rpm won't be satisfactory (apart from the obvious fact that i'd be using a drill), so last night i decided to go with the router solution, as well.

Now that i've seen this video, i think to build a large one like that since i was trying to find a solution for also flattening wood for cheap.
Maximum shaft diameter for my router is 1/4", so the bit would have to be smaller.

Your suggestion for an indexable carbide blade sounds good, as well. I'll compare prices with standard milling bits and also the cost of replacement carbide tips for it.

Thank you