Cutting fret slots

[Anonymous]

I am having a dickens of a time getting fret slots cut. I've looked at all the other posts on this, but they don't seem to solve the problem I've got.

I have a radiused board with the fret lines projected to the surface. I use a parallel cut to clean & radius the board, but when I try to do a trace with a bit, all it does is barely scuff the surface. I can't get the bit to dig down into the wood no matter what settings I try.

Unless there is absolutely no other way to do this, I just want to draw where the slots go with a line and have a tiny bit center itself on the line and follow the curve at a preset depth. I don't want to 'model' the slot as, depending on the bit I use, the widths could change. 

I've shared a sample of what I'm trying to do

http://a360.co/2gYOw1Q

I'm just using a 1/8 flat endmill so I can see better. All i want to do is "trace the curved line to a specific depth below where the line actually is", I just can't figure out what I'm doing wrong.

[LibertyMachine]

I will try to take a look at the file tonight, but I suggest trying "Project". Trace is a rather "dumb" toolpath and not going to give you the result you are looking for (typically)

Project does require a line drawn on centerline of the slot, preferably at the top surface or even higher.

[Anonymous]

Thanks. I did project onto surface from above. The projected line follows the curve exactly, and I could easily use a 'sweep' to carve out the necessary channel and then just use Pocket  for it, but that would mean each fret slot would have to be swept, and 24 of 'em would take forever. Plus, add in that I might want to change the width based on the bit, and I'd prefer just a line and whatever 2D tool to cut along the center would be.

I appreciate the eyeballs on it!

[LibertyMachine · Accepted solution]

If using Trace, you need to set a value in the Axial Offset tab, assuming you want to go deeper then where your sketch line exists:

[Anonymous]

THAT's what it was. I couldn't figure out how to get it to carve deeper.

The only issue i guess I'll have now is how to do that in multiple passes so I don't break the bit, but worst case scenario I can just copy / paste & run a few times, each with a slightly deeper Axial Offset.

Thanks!

[LibertyMachine]

Tsk tsk. Axial Oddset Passes, the button right below Axial Offset 😉

[Anonymous]

Can you tell I'm new at this? 😉

[LibertyMachine]

We all start somewhere. Every now and again, I go alllllll the way back to my first few posts and remind myself that I was very lost in the beginning

[robpage]

I'm wondering if I could ask for some help with this too.  Thanks SO much for the axial tip, I was having the same issue.  I'm getting depth now but Fusion has changed a bit since this thread started—seems we no longer have an "Axial Offset Passes" button.  So I checked "Multiple Depths" which we do have now, made the max stepdown .01 (wild guess, no idea what it should be for that teeny tiny bit) but then it asks how many stepdowns I want.  Why isn't the system just dividing my Axial Offset by the max stepdown I specified and determining how many stepdowns it needs to make?  Clearly I'm missing something.

Also, I have my feedrate set to 10"/min—another wild guess.  Can anyone recommend feed/plunge rates for this microscopic .0236 bit?

Thanks a bunch!

[matthewrjacobs]

Rob,

1st,  10in/min is fine.  

2nd,  IIRC, you will need to set your stepdown to .075/7 to get a depth of .075in, just the way it is. 

BTW, I do full depth passes at 10in/min, and haven't had a bit break on me(knock on wood)

[robpage]

I feel like such a dummy... what does "IIRC" mean? hahaha. Can you tell I'm a noob? And by "stepdown" you mean the axial offset, right?

So if I'm understanding you correctly, I have it set right: axial offset -.075 with 7, .01" setpdowns. Yeah?

But if you're doing full depth passes then conceivably—if I had balls—I could turn off Multiple Depths and just do the entire -.075 in one pass?  Very scary...

[matthewrjacobs]

IIRC, it's shorthand for If I Recall Correctly

Below are a couple of examples to show you  what is going on.  Both have axial offset set to -.075in, the top one is .075/7 with 7 stepdowns.  the bottom one is .075/7 with 8 step downs.  you can see if you exceed the offset, the 1st stepdown is raised so the final depth  is -.075".   

[robpage]

@matthewrjacobs you are the best.  And your guitars on your site are beautiful!

Thanks for the help.  Really appreciate it.

[robpage]

My run time for the fret slotting is 31 minutes at 7/.01 stepdowns.  If I change to 4/.02 it gets me down to 19 minutes.  I'm too nervous to do it though.  But you say you're going full length in one pass?  Did I get that right?  Seems like that would snap that little bit in a heartbeat.

[matthewrjacobs]

I haven't got a ton of CNC'd fretboards under my belt, 5 or 6.  But my buddy has dozens and he's the one that turned me on to full depth.   one caveat,  we both have precisebits collets,  so that probably has something to do with our success rate.

I don't see how putting all the force on the very end of the bit could possibly reduce the chance of snapping a bit.  where full depth you are at least moving some of the force up the bit. I could be completely wrong though.  

I think you are safe with .020" stepdowns

[robpage]

Thanks!

[robpage]

Broke a bit on the sixth fret...  I started a new thread here if any of you guys can help.  Thanks...