Advice sought, cnc a joint for scarfing

[simso]

Folks,

Wonder if someone out there has done this or knows of others that already do this.

Currently when I need to make a neck that is angled, I simply do the scarf on a table saw, and glue the joint up.

To turn that into a neck, I either do it by hand or I strap the whole assembled unit and cnc machine it using a long cutter.

Necks like teles and strats and so forth, I can draw up in cad and have the cnc punch them out in about 15 minutes a unit, that is shaped, slotted for truss rod and rear contour profiled, we use these in our kits that we supply to others to "assemble"

I wish to make a joint system like a lego click together, that allows me to create a scarfed neck on the cnc, clearly it would be in two pieces, but ideally, it would click together. Taylor used a fingerjoint option and so do deering banjos, so that is an idea

I have been over thinking this one for quite some time and just cannot get my head around it, anyone doing it at the momment or have ideas or seen something similiar

Ideally I do not want to simply machine a slip joint, I can do that now if necessary, but think it could be way better than that

Thanks in advance

Steve

[jeffhigh]

The CNC "V" joint on the Cole Clark is one of the few details I like on them.

[blackalex1952]

Might I suggest that you research Japanese carpentry joints. I feel that the philosophy would be ideally suited to CNC machining...the main purpose of a strong joint is to maximise glue surface area and to minimise weakness due to the grain running in the wrong direction relative to shear forces. Also dissimilar timbers joined together would require different treatments, perhaps.
some links:
http://www.amazon.co.uk/Art-Japanese-Jo ... 0834815168
http://www.flexiblestream.org/project/5 ... ood-joints

[demonx]

When I started using CNC I put some thought into how to tackle this and I came up with nada.

Having a 3 axis machine limits the possibilities. If we had five or six axis machines you could start looking at jigsaw joints etc, but that's just be too time consuming on a 3 axis.

[blackalex1952]

This might be of interest:
http://openbuilds.org/?category=cnc-rou ... lds&id=286

[blackalex1952]

I am only just getting interested in CNC machining. I would appreciate as much input (pun intended) as possible! Here is something I found on YouTube:
https://youtu.be/Ovc9bfeXS1A

[demonx]

I am only just getting interested in CNC machining. I would appreciate as much input

Here's my 2c now that I've used a few different machines.

After having a tool changer, I could never own a CNC without one. After owning a solid, quality machine, I would never consider even looking at the cheap hobby type machines. They're not worth the headache.

My advice is set a budget, then add money to whatever you think you want to spend, probably put a zero on it, and that is your starting price. Anything less is simply too much of a hassle and you're better off doing everything by hand than investing in a lesser quality machine.

Also, people have all sorts of weird and wonderful ideas about a CNC building guitars and pumping them out by the container load. Remember it's just a router on a frame and the computer is the template, nothing more.

[simso]

After having a tool changer, I could never own a CNC without one. After owning a solid, quality machine, I would never consider even looking at the cheap hobby type machines. They're not worth the headache.

So true.

Also, people have all sorts of weird and wonderful ideas about a CNC building guitars and pumping them out by the container load. Remember it's just a router on a frame and the computer is the template, nothing more.

You can do this, we do it on occassion, but the difference is our main cnc machine (we have a few) is larger than most family cars

Thanks for all the ideas so far to everyone, still looking.

Steve

[simso]

For those that may be interested

We currently supply scarfed heads to any supplied drawing, ready to go for other builders / repairers at 12 or 14 degrees normally

This however is not what Im trying to achieve here, and it has me stumped to an idea

I want to make a better system for our in house complete necks that are scarfed

Steve

[Allen]

I am only just getting interested in CNC machining. I would appreciate as much input (pun intended) as possible! Here is something I found on YouTube:
https://youtu.be/Ovc9bfeXS1A

Both of the examples you have posted are nothing more than toys. Their working envelope, rigidity and mass will forever limit their usefulness to the curious hobby builder. Then there is the tool holders and tooling. Start adding that up and it can take your breath away.

And before you ever think about plunking down $$$ for a machine, you had better wrap your head around the design software. It's far, far more involved than most people ever consider.

[Allen]

For those that may be interested

We currently supply scarfed heads to any supplied drawing, ready to go for other builders / repairers at 12 or 14 degrees normally

This however is not what Im trying to achieve here, and it has me stumped to an idea

I want to make a better system for our in house complete necks that are scarfed

Steve

Now, that is a challenge Steve.

I had always assumed that the head stock scarf joint would be done on the saw and then laminated onto the neck plus heel. Then machined. But now that I think about it, there really should be a better system to do this.

[simso]

Now you see my interest.

I can already cut a normal scarf by table saw or cnc, but you still run a slip joint. Ideally it would be nice to have a joint that interlocks together, you glue and clamp and wolla all done, maximised glue area and a joint that cannot slip during assembly,

The downside with slip joints is they move some during glue up, not an issue when you fudge some extra material in to machine of later, but when making something with the precision of cnc, it would be good, to go lego part A click into lego part B and glue, and you have the exact same joint every time

Steve

[simso]

I just had a light bulb momment.

Edit,Just realised I ddint

[Allen]

Perhaps this idea might jog the grey matter. The birds mouth joint might do the trick.

http://www.tormach.com/John-Bower.html#.VdmcwrTC27g

[kiwigeo]

I just had a light bulb momment.

Edit,Just realised I ddint

You've been living in Perth for too long....

[simso]

Yep, thanks for the link allen.

More food for thought.

Steve

[routout]

I guess the problem with the scarf joint is the thinnest point is always going to be a problem to work with ,so I guess there needs to be a square edge where they butt together left after shaping the underside just a thought.

[kiwigeo]

I guess the problem with the scarf joint is the thinnest point is always going to be a problem to work with ,so I guess there needs to be a square edge where they butt together left after shaping the underside just a thought.

2 x 4mm diameter dowel locater pins would be a more sensible option to stop joint sliding while glue is setting.....normal headstock veneer would cover pin topside and a backstrap would cover pins on underside of headstock.

[jeffhigh]

The holes for the dowels could be blind, only 3mm deep on both sides rather than through.
Much Like a lego lug,

[Allen]

The problem arises when you consider working in just 3 axis with only one set up. By drilling holes that dowels are going to be used to line up 2 parts that are on some other angle other than the one that they are machined on, you hit the brick wall.

The only way around this will be to have a second operation that requires some sort of fixture that holds the parts in the correct plane for the next machining, i.e. drilling for dowels.

I haven't been able to wrap my head around another method yet.

[kiwigeo]

The problem arises when you consider working in just 3 axis with only one set up. By drilling holes that dowels are going to be used to line up 2 parts that are on some other angle other than the one that they are machined on, you hit the brick wall.

That's where the Cray computer comes in.....I forget to mention same in my last post

[simso]

I haven't been able to wrap my head around another method yet.

Spot on, on all accounts, without repositioning the head during machining then its a hard one to do machining on one side and match up on another piece thats been cut at a different angle.

Steve