Corner Tunnels

[mikkojay]

Hello,
I have not had a bunch of time to experiment, but it seems like all of the signs I have made so far are exhibiting a symptom I can only describe as 'corner tunnels'. My first guess is that my Z depth may be slightly off. If so, it is off the same amount, every time. I am using a Techno Isel gantry router with a touchoff pad that I can guarantee accuracy to at least .005 inches. I will post a couple of pictures so you can see what I mean. Any suggestions would be appreciated. I am sure it is just a matter of getting a few tweaks down.
Also, I am using a 90 degree V bit that is pointed.

Thanks, Mike

[Dman]

Mike,
From the looks of the picture I would have thought the v-bit had a flat on the end instead of a sharp point. If your z depth is off the rounded area would only show up at the very top of the carving but looking at the pictures it appears that it runs all the way from bottom to top. I would maybe try another v-bit. Could it be possible the bit is not running true or the sharp point is offset?

[mikkojay]

You would think so.
I will attach a picture of the bit I have been using. It is virtually new, and sure looks pointed to me- but I have been known to hallucinate. I forgot to mention that when I originally carved out the BullsHead sample with the ornate scrolling on the letter B, the edges looked really crisp as you would expect. I did that one using the same bit. Now that I am trying to make signs that I have edited myself, the edges are just turning out wierd.
Just for kicks, I might try your suggestion of another bit. Stranger things have happened! My first reaction was, "no way!" but now that I think about it, it would only take a few minutes to test the theory. I'll swing by the hardware store tomorrow and pick one up. Worst case scenario: I have a spare bit. Best case scenario: easy fix, and I didn't waste a bunch of time trying to chase my tail.
I do have one fact that may blow a hole in the bad bit theory- look at the flat area on the second example. See the tight parallel lines from the multiple passes made to create the flat area? How could I wind up with lines like that without a sharp, centered point? I'll let you know what happens.
Thanks, Mike

[CRFultz]

Take the bit and press down onto a piece of paper...does it make a little round hole? A sign makers bit has a additional flute cut at the tip to make it a point viewed from the cutting end. Sears sells sign makers bits...a 90 and a 60 I think. This doesn't appear to be your problem, not sure about the upsweep in the corners...they should be sharp.

Chuck

[mikkojay]

Thanks for the feedback-
I live right down the street from a Sears, but I am off to work at the moment. I will pick one up after work and try it out when I get home. I should know something about 10 hours from now.
Thanks again,
Mike

[Tony Mac]

Hi Mike,

The problem could be related to cutter run-out (not running concentrically) which results in the tip spinning off-center and creating the flat region where there should be a sharp line.

If there is a small flat on the tip of the cutter it's best to define it as an Engraving Tool in the Tool Database, adding the approximate Flat Tip Diameter. Remember to specify the half angle - 45 degrees for a 90 VBit.

Another thing to be aware of is the results you get if the cutter angle is out by a few degrees. The images below show the results of programming a toolpath with for a 90 degree VBit but actually cutting the job with 80 and 100 cutter degree cutters.

Let us know how you get on with the tests,

Tony

[mikkojay]

Now I see the flat part you guys are talking about-
I went to Sears and bought the only 90 degree V bit they had- as I was walking to the car, I saw how it differed from the V bit I am currently using (it has more of a flat spot than the one I was using).
The blue one is my original, the black one is the one I bought at Sears.
I will mix things up and let you know what happens.
Thanks, Mike

[mikkojay]

Just checking in-
Yeah, its looking more and more like I need a better bit.
I have tomorrow off, so I am going to go on a quest for some high quality bits.
I have a steady stream of trick-or-treaters knocking on my door now, so I need to go.
Happy Halloween!
Mike

[CRFultz]

Originally Posted by mikkojay Just checking in- Yeah, its looking more and more like I need a better bit. I have tomorrow off, so I am going to go on a quest for some high quality bits. I have a steady stream of trick-or-treaters knocking on my door now, so I need to go. Happy Halloween! Mike

Mike,
I buy my vbits from here

http://www.routerbits.com/cgi-router...665146_5775+21

There made from Whiteside and they have fast shipping...prices are about the same anywhere else.

Chuck

[mikkojay]

I went and found a really beefy new V bit today. I bought it at a company that sells nothing but woodworking equipment. That place was like a candy strore- I had never been, but I am sure I will return. To make a short story long, the new bit did wonders for the quality of my corners. So thanks Dman and everyone else for your input! I now see that you get what you pay for when it comes to bits. I still have a tiny bit of software tweaking to do, but things are looking MUCH better. The new bit has a 1/2 inch shank instead of 1/4 like my old one.
The pictures are not that great, but I think you will be able to see an improvement. The corners are nice and sharp, bit I may have just a tiny bit of the phenomena in Tony's 3rd sample picture happening. I noticed that you can use the up/down arrows to change the bit angle by 5 degree increments, but you can type in whatever you want. I may need to try and tweak that setting a couple of degrees to get it just right.
Thanks Again, Mike
Now I am off to my next topic- dust control. Right after I wire a new 15 amp breaker & circuit to by back porch, to power that killer dust collector I saw at the candy store. Am I thinking out loud? Later

[Dman]

Mike,
Glad to hear and see your problems getting worked out. I am not sure how long you have been running Vcarve but I think you will find that the support at Vectric is top notch. If you haven't already joined the Vectric forum you should look into it. Support there is fantastic both from other users and the Vectric team. Can't wait to see the dust collector!
Dman

[HayTay]

Originally Posted by mikkojay I went and found a really beefy new V bit today. I bought it at a company that sells nothing but woodworking equipment. That place was like a candy strore- I had never been, but I am sure I will return.

This store wouldn't happen to be Woodworker's Supply, would it???