Sort of accidentally started a new build...

[blinddrew]

Interesting, I did buy an EZ-lock mandrel and a set of their cutting wheels. They too just disintegrated whilst mildly polishing the cutting surface (aluminium in this case if I recall).

[PJSprog]

The thing about cutting metal that most people don't know is that speed is not your friend. Slow and steady is the ticket. Think of how slow the blade on a cold saw turns.

[Dikkybee007]

Been a Toolmaker for over 40 years and while I have used every machine in my line of work the only electrical devices I use making my guitars is a drill press because I like my holes to line up when using a hardtail bridge, a random orbital sander and a battery hand drill. All shaping or material removal is done with rasps, files and scrapers. I find more satisfaction in using my hands as it takes more skill.

Speeds on any cutting device is relative to cutter diameter and type of material being cut and the cutter material. Most good cold saws have 2 speeds, slow for harder materials and quicker for soft. Stainless/ferrous you always run slow, aluminium/non ferrous you use the faster speed and of course there is various teeth pitches and configurations. Cold saws blades are fairly large so you run them slower than a Dremel cut off wheel as the speed is relative to surface speed produced by the outside diameter and the material the blade is made of. Cold saw blades are tool steel so it runs slower than Carbide cold saw blade which runs slower than a abrasive cut off wheel which runs slower than a Dremel cut off wheel.

I have used Dremel cut-off wheels and they are a little bit temperamental if you don't know how to use them. The faster you rotate them the better. Make sure the job is securely held as any movement will destroy the wheel so holding it in your hand is a no-no and use 2 hands on the Dremel. DON'T try and use it like a 4" angle grinder as you will break the wheel quite easily. The more pressure you put on the wheel when trying to cut anything the quicker you will destroy the wheel. A steady LIGHT pressure is all that is needed. The more you try to cut through the more the wheel will destroy it self. If it isn't sparking, it isn't cutting and no mater how much harder you lean on it wont make it go quicker.

Grinding wheels cut by using friction to melt the material and that is why they spark. Grinding/cutting disks have to run fast as they use the speed to melt the material. The Dremel website says you can use their wheels on Aluminium, Brass, Copper and plastic. None of these materials will produce sparks and all they will do is clog the wheel with material and will make the resulting wheel explosion much more spectacular. NEVER use a grinding wheel on non ferrous materials, unless you want to spend some time recovering from being hit with a piece of an exploding disk.

To cut the piece you are trying to reduce in length McCreeds way will work. The other way is to use a hacksaw with a 32 TPI or if you can find finer pitch blade and have a spare hacksaw blade that you will use later on. Clamp the item in a vice by the 2 ends, that way you don't crush it and make it out of round and cut so you just break through to the inside diameter and then rotate and repeat. Once you get to roughly to the half way mark, or a little further, the item will start to grab the blade and jam. You use the spare blade and place it it the cut to help stop this. The hacksaw will cut wider than the spare blade due to the blade having a wave profile but the spare blade can be used with a piece of paper wrapped around the blade to take up the extra width. More than likely you will need to file the ends square/flat so to hold the item you can sit the larger flat end down on a spare piece of wood that is held in you vice and strategically use some round/pan headed screws, probably at least 3 but 4 would be better and clamp it down. You could use countersunk as well but I would use the round/pan head. If you have a screw that is the same diameter as the inside of the item screw it into the wood inside and below the top surface as it will also give you some support when using a file to finish the end. If you have a screw that is slightly larger then just put it in a electric hand drill and use a file to make to diameter smaller so it fits neatly in the inside. Easy as.

[blinddrew]

Ok, bit of contradiction in the comments but clearly I'm going to have to get a bit of scrap steel and have a play.

[Simon Barden]

Dicky is right here. There's a big difference between a steel cutting blade and a cutting disk.

The blade relies on having sharp serrated edges to cut. Get the steel blade too hot and it looses its temper and goes dull and soft and then fails to cut properly. So you want to work slowly and ideally lubricate the cutting area to remove heat.

The disk relies on a fast speed generating friction and heat, so it needs to run quickly. There's a trade-off between speed and the centripetal forces on the disk that are trying to pull it apart. If it's quite flimsy, then if you run it too fast, it may simply break apart without even touching anything. Add in the forces on one small section of the disk when it's brought into contact with the metal its cutting, and you can see that they can be quite fragile. The lighter the contact touch with the metal, the less likely the disk is to break. So whilst having the disk run as fast as possible is the ideal. For small, fairly weak, disks, you probably have to find a compromise between speed and the tendency for it to break.

Applying any sideways force on the disk once it's cut a groove and the disk will snap and break. It's easy to get a lot of leverage on the edge of the disk, so as Dicky says, it's important to keep the disk at a constant angle to the workpiece.

[blinddrew]

I think yesterday was what you might call 'a mixed bag'...

Painted up the headstock, rough fade work for the back of the neck:


Filled in a few spots around the edges


Bit of sanding to prep the fade


And a bit more sanding to tidy up the front of the headstock


Then I went to add some poly...

Now it's important to note that, having used these paints before I was expecting a bit of 'lift' (even relying on it to smooth that black / brown transition).

What I wasn't expecting was this:




Back-tracking a step, because the original 'brown' paint I was using was very orangey, I'd added some red dye in there to make it that slightly darker, slightly redder colour you can see on the back of the neck.

But when I started applying the poly it has lifted the dye out of the paint!

I was not expecting this.

There is an upside to it though.

Because there is now no way that this will look like anything other than a dog's breakfast I no longer feel the need to spend more time on applying multiple layers of poly, sanding back etc etc to try and get a smooth finish.
Once this is dry I can drill the holes for the tuner screws, put it together and see if it works.

If it does then at some unspecified point in the future I can actually spend some money on it and buy some more filler and some spray paint to make it look nice.

For now it will just be about making it make a noise.

[blinddrew]

Ok, so here we have the Guinjo







And a little video of how it sounds: https://www.youtube.com/watch?v=L36NEZtcvI4

[Simon Barden]

I thought you were going to demonstrate your clawhammer technique*.

Looks like it still needs a lot more setting up.

What note is the head tuned to?

*steel claw and a sledgehammer.

[blinddrew]

Not sure on the head tuning - not sure how to measure it really.
As well as a little more setting up I need to work out how to get the most out of is in terms of playing technique - it's definitely different to a guitar.

[blinddrew]

I have just watched a video on tuning a banjo head. Interesting. I am not sure that the drum skin will take that kind of tension, but not being a drummer I don't know how much tension a drum skin is normally under.