Official Luthiers Forum!

Funny thing, lately I have been overwhelmed with headstock templates or machine my headstock shape. Most have Sharp inside corners. I try to explain that this is a rotary tool and the inside corner will not be sharp (must allow for the radius of the tool). To no avail, I get "Well I saw it on "How it's made" so what's the problem?"
The last guy is "starting his line" of guitars using premade necks with a paddle head and wants his headstock design and using Warmoth bodies. I explained the problem and he was saying that Fender does it, so why can't you? I nicely explained I didn't have a 500K waterjet machine but would gladly get one if he would front the $ for the work he needed. LMAO!!!!

So what misconceptions do you see or have to explain?
MK

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I'm outside looking in, just farther from the window than most.

Mike, while I don't normally do custom CNC, I find it very easy to convert a rounded inside corner to sharp with a -sharp- chisel.
I can see where someone who doesn't speak "machining" might not understand the need for this.
Maybe you can develop a shaping tool for us and use the Z axis as a shaper.
Nelson

I often have to explain why low quantities are expensive to customers (ie: if you called Ford and wanted a one-of custom car would you expect it to cost the same as buying a Focus off the lot?). So far as capabilities go, I find there are as many misconceptions about what can't be done as about what can. My machine can make anything I could possibly make with my hands, so long as I'm imaginative enough to figure out how to teach it! Usually an 'unmachinable' part is a limitation of fixturing rather than a limitation of the process.

So far as the templates go: You can cut a sharp corner, just not in plane. The fixturing isn't completely straightforward, but it's not an uncommon operation. It would likely be quicker to finish the corners with the bandsaw as a secondary operation on single custom parts, though, especially if they're in wood.

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Nelson I agree I can do that as well with a chisel. That's is the part of woodworking that we do. Now doing aluminum templates are a different matter. Problem is they want it done by the machine (no effort on there part).

Yes Bob, with some fixture changes in axis I can get that corner as well.I also agree the limits are mine as you so well pointed out. But as we all know No One wants to pay what the time is worth for this. Everyone seems to be in what I call IKEA mode. Cheap and fast.

It becomes annoying at times. Trying to explain in nice terms and it's always the same response.

"but it's just a simple thing and will take no time at all"

oh well. I was just wondering what others find people asking for that are in the misconception zone?

mk

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I'm outside looking in, just farther from the window than most.

I was approached by a local luthier who wanted me to make bodies and necks for him. After a couple of phone conversations it became apparant that he believed cnc machines could bring the price down to......almost free. What disappointed me most about this was that he was also conferring with another local machinist who was claiming an ability to produce 15 Tele bodies an hour. That proved to me that the other guy had never made quality wooden parts before. With price being his only criterion when picking a supplier this "luthier" is now heading down the road to a very expensive lesson. He'll pay the other guy to develop tooling and also pay to educate him on the art of using a cnc to cut wooden parts. In the end, if this guys wants parts that have consitent quality, the other guy will end up being no more productive than I.

When I machine wood, I create tooling and write tool paths to guarantee the highest possible quality and then work from there to speed up the operations. I tried to convey this to him but he was far too interested in getting cheap guitar parts than to process anything else I was telling him. He never even came to my shop.

Sigh.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Just another note on this, One fellow OLFer, Chris V asked for my help with templates as well quite awhile back. He was fully aware of the problems encountered with sharp inside corners and made allowances in his dxf files for this.
I have known Chris a long time and help him in anyway I can. I want him to know that this thread is in no way a reflection on or directed at him in anyway.

So Chris, if you are reading this, you are not and have not been a problem.

Sincerely,
Mike

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I'm outside looking in, just farther from the window than most.

No Problem Chris If you come to Texas you will learn Grasshopper.

Mike

BTW here are some pics of Chris's MDF templates.

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I'm outside looking in, just farther from the window than most.

Mike, I'm probably missing something, but wouldn't the end user be using a round bit to cut the headstocks using the aluminum pattern?
Nelson

Yes, they would Nelson. And mentioning that seems to not make a difference. Since they don't seem to understand that concept as well. Once they get it, they usually say well heck I can do that with my router. Duh! about the only difference is we as CNC can use smaller diameter endmills, which will result in tighter tolerances of the inside corners for drawing purposes, but still they will be limited to the radius of the diameter mill/cutter. Just something that has been a so to speak with people. What has precipitated this is some of the local wood shop/suppliers are sending me these people. It's not just guitar related items. Some things are unbelievable what people want. some I can help others , well you know


Mike

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I'm outside looking in, just farther from the window than most.

You are welcome Chris, I apologize for the delay in these, will ship them by the weekend if the Honey do's don't bite me.

Next up for Chris is an aluminum set. I have a friend who owns a Machine shop. I have free reign of the CNC machines. I have scouted out all of Chris's aluminum from the shop scrap. That will cut the cost for him to "ZERO"

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I'm outside looking in, just farther from the window than most.

Sorry for coming off a little sharp, Mike, I meant that the limits in process ("can it be done") are ours...now, the economic limits ("can it be done cheap") are a whole different story!

The IKEA mode is one side of the cheap/fast/good triangle that I think is just dangerous for us small providers. The hardest lesson I've learned is being able to say 'no' to work you just can't do profitably. I guess the biggest misconception that hurts us is the idea that setting up a part for CNC cutting requires no more time than setting it up on a bandsaw. People tend to be surprised how much it costs to make 1-5 bridges in a custom design, but on something like an inlaid fretboard or anything with complex inlay or carving they tend to be surprised how inexpensive it is to have 1-5 made.

I've worked on nice ways to say 'I can't do that profitably at a price that seems fair for the part being made'. Sometimes the client is a bit annoyed, but often they get curious about where the costs lie and are then OK with the let-down or they say 'OK, what do we need to do to make this happen'? That last group are the clients I keep, and it's like having a job with the most amazing co-workers on the planet

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Bob, you in no way came across sharp. I knew what you were saying. I also agree, some, once you explain the process of setup and other factors understand this and work with you. These are the ones that become not only working relations but friends as well.

Again, many though could care less how much I or you have spent on, the machine, tooling, software, electrical needs, etc.. etc.. It's well so and so said they can do it, or I saw it on TV so it must be true. LOL!

Like I said, I was just wondering what others experience as misconceptions are about our machines?

Mike

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I'm outside looking in, just farther from the window than most.

Some people think that anyone who does CAD/CAM/CNC must be smart.
I've proven them wrong.

Better sharp than flat, I say.

At least when you're sharp you're overachieving.

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

Yeah. the corner radius thing is a pain -although honestly I haven't worked with anyone that naive in many moons.

Solution: have them buy you a 4th axis and surface your external notches that are no narrower then 90 degs and charge accordingly. So now the end user can use a router and a guide bushing to produce a radius in the very same corners they want you to eliminate. We call this a "punitive quote". Those who pay get to eat a fat bill, and those who can't -go away or get duped elsewhere.

Agreed. Doing quailty wood work isn't anything like flogging aluminum or plastic parts (and 15 tele bodies in an hour is abusive to the machine and to the bodies) -there's abrasive tool wear, there's burning, there's chipping and tearout to account for.
Try to charge a initial consultation fee when discussing a job for a client. Get them to understand that you aren't making any money disscussing a waste of time job (put this nicely of course). Remind them that the time to program a part is the same for 1 part or 1 million parts and that wood needs special considerations.

I like that process

Very much like the lady that brought me her Oval Street signs made from mahogany to V Carve the Numbers in. Who ever did the oval cuts was shall we say not all there? Finding center was a new experience

Then she wanted the numbers gold leafed and paint the ovals with black lacquer. I cut the numbers, that was all. LOL! she was definitely clueless. Oh well takes all kinds to make this world we live on spin.

MK

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I'm outside looking in, just farther from the window than most.

Bob, now we really knows what he thinks of you!

Mike

I still can't wipe the grin from my face

I've heard that humans are worse at hearing sharp notes than flat ones, so it's really true!



I totally didn't notice that! If Mike K weren't such a nice guy that would have been a championship sneak attack

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Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

LMAO!

Hope every ones day is going well.

Here's a new project that just came in yesterday.


Thought I would share a repair that just came in. A 1982 music Man bass (Pre Ernie Ball) 2 piece Ash body. Someone tried to install a trem bridge on this (sure ruined the value of this thing). The new owner finally found a string through Music Man bridge. So I now have to fill in the cavity and install the bridge. So here are the pics before I start.







I'll be using my CNC router for this. Needless to say tests cuts will be made in MDF before the body is under the gun.

So the plan is to make an insert for the pocket.




Then pocket the offended area. This process will progress from being undersized by about 0.030" and profiled by 0.005 or less" until a perfect fit is achieved.



MK

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I'm outside looking in, just farther from the window than most.

Mike,
Why not jig-jag the part into place? Not sure how to describe it other than make no two points the same connection point.( not a square/rectangle block) When we do furniture repairs we never do abrupt squares but try and match in the grains with some pattern that is not picked up by the eye as a prominate patch. Another trick is to cut the patch and the holes in a taper so when the patch is in place it tights snug as it goes down. Even a dovetail style patch in my opinion would look better than the square/rectangle as you show. I realize much of this is covered but there are some area's that are seen.
My two cents.

Kevin

Hi Kevin, actually all of this is covered by the bridge. It also allows me not to remove the original bridge post inserts. Mainly this patch gives the support needed for the string thrus.

MK

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I'm outside looking in, just farther from the window than most.

That's the approach I take to fits but in my experience using a .005" progressive increment is far too aggressive when sneaking up to a fit.

If a tool has never been sharpened (re-sharpening reduces the diameter) the diameter will be exact. When cutting both the plug and the cavity net to the contour...there is no possibility of producing a fit...and certainly not too large of a fit. Furthermore, the difference between a large interference fit and a loose slip fit can be as low as .0005"....but figure .001" is a good increment to progressively step out your profile cut as you make the fit happen. If you use the .005" increment you risk blowing past a nice fit and have quite a bit more gap than you really wanted.

As a rule do this:

1. Cut the male plug net to the contour line.

2. Cut the female cavity to the contour line and leave .001" (the most precaution I ever take).

3. Continue to write contour (profile) toolpaths that step out progressively in .001" increments. Do this until there are 20 or so to guarantee that once the program is out to the machine you won't have to go back to the computer and generate another toolpath. One of 'em is GOING to fit. It's important to write all these subsequent contour paths with a high retract height so that between each cut you have room to check the fit.

If your machine is rigid and accurate, and you follow the plan above...I predict a nice, tight fit at around cut +.007"

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I read Emerson on the can. A foolish consistency is the hobgoblin of little minds...true...but a consistent reading of Emerson has its uses nevertheless.

StuMusic

I agree Stuart, I have found that an interference fit of about 0.004/0.007 is about right with most wood types. and yes I figured I would sneak up at the last passes in the 0.001 range,

Mike

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I'm outside looking in, just farther from the window than most.

20 programs? good grief! this sounds like a lotta work. doesn't your machine have cutter comp?