Advice sought, cnc a joint for scarfing

Talk about musical instrument construction, setup and repair.

Moderators: kiwigeo, Jeremy D

Post Reply
simso
Blackwood
Posts: 1768
Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Advice sought, cnc a joint for scarfing

Post by simso » Sat Aug 22, 2015 1:57 pm

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
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

jeffhigh
Blackwood
Posts: 1536
Joined: Thu Feb 07, 2008 5:50 am
Location: Caves Beach, NSW
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by jeffhigh » Sat Aug 22, 2015 3:49 pm

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

blackalex1952
Blackwood
Posts: 776
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Re: Advice sought, cnc a joint for scarfing

Post by blackalex1952 » Sat Aug 22, 2015 10:53 pm

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
"Everything I say on the topic is based solely upon inexperience and assumption!"

User avatar
demonx
Blackwood
Posts: 1395
Joined: Sat Jul 14, 2012 6:55 pm
Location: Ballarat Victoria
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by demonx » Sun Aug 23, 2015 8:59 am

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
Blackwood
Posts: 776
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Re: Advice sought, cnc a joint for scarfing

Post by blackalex1952 » Sun Aug 23, 2015 10:36 am

"Everything I say on the topic is based solely upon inexperience and assumption!"

blackalex1952
Blackwood
Posts: 776
Joined: Tue Aug 27, 2013 6:36 pm
Location: North East Victoria

Re: Advice sought, cnc a joint for scarfing

Post by blackalex1952 » Sun Aug 23, 2015 11:10 am

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
"Everything I say on the topic is based solely upon inexperience and assumption!"

User avatar
demonx
Blackwood
Posts: 1395
Joined: Sat Jul 14, 2012 6:55 pm
Location: Ballarat Victoria
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by demonx » Sun Aug 23, 2015 11:41 am

blackalex1952 wrote: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
Blackwood
Posts: 1768
Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Re: Advice sought, cnc a joint for scarfing

Post by simso » Sun Aug 23, 2015 12:15 pm

demonx wrote:
blackalex1952 wrote: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.
demonx wrote:
blackalex1952 wrote: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
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

simso
Blackwood
Posts: 1768
Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Re: Advice sought, cnc a joint for scarfing

Post by simso » Sun Aug 23, 2015 2:40 pm

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
Attachments
scarf.jpg
scarf.jpg (44.67 KiB) Viewed 19389 times
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

User avatar
Allen
Blackwood
Posts: 5252
Joined: Thu Oct 11, 2007 5:39 pm
Location: Cairns, Australia
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by Allen » Sun Aug 23, 2015 2:57 pm

blackalex1952 wrote: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 R. McFarlen
https://www.brguitars.com
Facebook
Cairns, Australia

User avatar
Allen
Blackwood
Posts: 5252
Joined: Thu Oct 11, 2007 5:39 pm
Location: Cairns, Australia
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by Allen » Sun Aug 23, 2015 3:01 pm

simso wrote: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.
Allen R. McFarlen
https://www.brguitars.com
Facebook
Cairns, Australia

simso
Blackwood
Posts: 1768
Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Re: Advice sought, cnc a joint for scarfing

Post by simso » Sun Aug 23, 2015 5:48 pm

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
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

simso
Blackwood
Posts: 1768
Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Re: Advice sought, cnc a joint for scarfing

Post by simso » Sun Aug 23, 2015 6:08 pm

I just had a light bulb momment.

Edit,Just realised I ddint :gui
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

User avatar
Allen
Blackwood
Posts: 5252
Joined: Thu Oct 11, 2007 5:39 pm
Location: Cairns, Australia
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by Allen » Sun Aug 23, 2015 8:21 pm

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

http://www.tormach.com/John-Bower.html#.VdmcwrTC27g
Allen R. McFarlen
https://www.brguitars.com
Facebook
Cairns, Australia

User avatar
kiwigeo
Admin
Posts: 10582
Joined: Sat Sep 29, 2007 5:57 pm
Location: Adelaide, Sth Australia

Re: Advice sought, cnc a joint for scarfing

Post by kiwigeo » Sun Aug 23, 2015 8:28 pm

simso wrote:I just had a light bulb momment.

Edit,Just realised I ddint :gui
You've been living in Perth for too long.... :mrgreen:
Martin

simso
Blackwood
Posts: 1768
Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Re: Advice sought, cnc a joint for scarfing

Post by simso » Sun Aug 23, 2015 9:02 pm

Yep, thanks for the link allen.

More food for thought.

Steve
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

routout
Blackwood
Posts: 289
Joined: Mon Jun 15, 2015 7:34 am

Re: Advice sought, cnc a joint for scarfing

Post by routout » Mon Aug 24, 2015 8:27 am

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.
John ,of way too many things to do.

User avatar
kiwigeo
Admin
Posts: 10582
Joined: Sat Sep 29, 2007 5:57 pm
Location: Adelaide, Sth Australia

Re: Advice sought, cnc a joint for scarfing

Post by kiwigeo » Mon Aug 24, 2015 8:53 am

routout wrote: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.
Martin

jeffhigh
Blackwood
Posts: 1536
Joined: Thu Feb 07, 2008 5:50 am
Location: Caves Beach, NSW
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by jeffhigh » Mon Aug 24, 2015 9:31 am

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

User avatar
Allen
Blackwood
Posts: 5252
Joined: Thu Oct 11, 2007 5:39 pm
Location: Cairns, Australia
Contact:

Re: Advice sought, cnc a joint for scarfing

Post by Allen » Mon Aug 24, 2015 1:00 pm

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.
Allen R. McFarlen
https://www.brguitars.com
Facebook
Cairns, Australia

User avatar
kiwigeo
Admin
Posts: 10582
Joined: Sat Sep 29, 2007 5:57 pm
Location: Adelaide, Sth Australia

Re: Advice sought, cnc a joint for scarfing

Post by kiwigeo » Mon Aug 24, 2015 1:20 pm

Allen wrote: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 :mrgreen:
Martin

simso
Blackwood
Posts: 1768
Joined: Mon Apr 25, 2011 10:36 pm
Location: Perth WA

Re: Advice sought, cnc a joint for scarfing

Post by simso » Mon Aug 24, 2015 2:31 pm

Allen wrote: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
Steve
Master of nothing,

Do your own repairs - http://www.mirwa.com.au/How_to_Series.html

Post Reply

Who is online

Users browsing this forum: Google and 108 guests