Shellac bubbles when drying

The keyhole toolpath has been in CC for some time. I use a Frued 70-104. Go to the OEM website to get the exact specs of your keyhole bit. Be careful about F&S from the OEM. For instance the Freud website has fantastically high F&S. I think they are calculating for an industrial CNC and not a hobby CNC. Simply substitute your bit measurements for what I have and also your unique tool number.

The basic operation is to draw a circle the diameter of your keyhole bit. Then tell the toolpath how for to plunge forward. Super easy. The keyhole toolpath plunges full depth for the screw head and then moves forward the amount you set in the toolpath. Then the bit reverses and plunges back out the entry hole. Just make sure you plunge far enough to have some meat in the wood where the screw will actually hang on the wall. If you make it too thin the keyhole could break out.

The keyhole bit diameters are as follows. The diameter of the keyhole bit at the bottom. Then the thickness of the large bottom of the keyhole bit. Then the shaft of the smaller part of the keyhole bit. So you can calculate about 1/8" of meat in the smaller slot and likely about 1" of distance the keyhole will move forward.

Here is my custom tool database for the keyhole bit.

number vendor model URL name type diameter cornerradius flutelength shaftdiameter angle numflutes stickout coating metric notes machine material plungerate feedrate rpm depth cutpower finishallowance 3dstepover 3dfeedrate 3drpm
701 Freud 70-104 701 Keyhole end 0.39 0 0.25 0 0 2 0.125 0 10 60 16000 0.4375 1 1 60 16000
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Thanks! I will give it a try, my bit came in a $100 assortment from Lowe’s so I’m not not I have the specs on it but I’ll give it a try and if needed but a new bit.

Just measure the bit and enter your measurements in the custom tool database. Even using my tool database would work. You are just drilling a hole, plowing forward. The key is that the entry plunge is big enough around to get a #8 pan head screw through. You could slow down plunge rate and ipm down and bring them up till you are comfortable.

Just get a piece of scrap and practice

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5 posts were split to a new topic: Adjusting design for successful cutting

Shellac and poly both dry very quickly and the result is that the wood may have some moisture content that cant escape, thus bubbles appear. First, make sure your wood is dry 7-10% level , if not try warming the board somewhat and avoid spraying in cold environments. You can use a hair dryer as noted, but from your pictures, you may be attempting too thick of a coat instead of multiple lighter coats. Tom

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Good point, I was not thinking of moisture in the wood. I may have put the first layer on thicker but not by much if anything. I tried the heat gun and it definitely helped. I think next piece I’ll try heating it with the heat gun first then quickly after.

I’ve had bubbles in shellac even when the wood was kiln and vacuum dried.

My theory is that some alcohol wicks into the wood, gets trapped under the now drying shellac, turns into vapour and causes bubbles. Temperature is a contributor to this, higher temperature causes the alcohol in the shellac on the surface to evaporate faster.

Just my 2 cents, YMMV or YKMV(for us metric users).

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