hCore Profling help

[Leon87]

Hi guys

Im having a nightmare with my cores.
Ive made a couple a good boards but have probably wasted about 4 cores!

Im having so much trouble securing the core to the router jig, it lifts in places so i cant get a smooth profile, in place it gets so bad that i have to scrap the core.

Ive tried hot gluing it, using sticky tape and leaving the core alot longer so i can screw it down.
Any tips as its getting soul destroying now!

Thanks
L

[chrismp]

Build a vacuum table like this as the base for your router table: http://www.youtube.com/watch?v=fOrkvPF0pro

It's the only way we were finally able to hold our cores in place properly (even the crooked ones!) and it's cheap!

[twizzstyle]

My method on my CNC router is to cover the bottom of the core blank with masking tape or decal application tape, and then spray glue that down to a piece of MDF that gets bolted to the table. That has worked great for me, it can be a little tricky getting it off the MDF when you're done, but the masking tape/application tape peels right off.

[Leon87]

thanks for the replies.

I might try the vac table. it likes pretty simple. i thought it would be alot harder!

do you use a simple hoover for the suction?

[chrismp]

We use three vacuum cleaner motors, but we have a huge box that covers the whole working area of our cnc (2.6x1.2m). A regular vacuum cleaner like shown in the video works well on smaller boxes. We went with the bare vacuum cleaner motors because you can achieve better suction if you attach the hose directly to the motor. If you decide to strip down an old vacuum cleaner or buy a new motor, try to get one that has a fan for cooling the motor in the back. Like this one:

[Leon87]

Can you do just like in the video? he uses just a vacuum cleaner, will that hold down a core?

[loganimlach]

my setup consists of hooking my shopvac up to the bottom of this:



the channel is routed 3/8" into 3/4" MDF with a single hole at the center that goes all the way through to an adapter (2x4 w/ lots of silicone haha) that hooks to my shopvac.

works well, as soon as i kick on the shopvac the only way to move the core is hit it with a hammer, i can't even move it with my hands.

[chrismp]

Yep, a regular vacuum cleaner will hold down a core as well. As for the type of suction system I found the box with multiple holes to work better than the channel loganimlach posted. We've tried a similar channel and had some trouble getting it to suck down crooked core blanks. With the holes you cover a much larger area of the core and you can adapt easier to different core sizes by covering the open holes with a plastic sheet (we use garbage bags ).

[dvollebregt]

I'm working like lomanimlach and it works great, using bamboo cores.

[knightsofnii]

what about using a down cutting bit as opposed to a flat or up cutting bit?
I notice my up cutting bits will pull the material up sometimes, especially when making holes.

[chrismp]

Another issue we had with the channel like on lomanimlach's table was that the thinner nose and tail got sucked into the channel just a bit which lead to inconsistent tip/tail thicknesses.

[skidesmond]

Another cheap alternative is to use a wide tape that has a rough surface. Might be called grip tape. You can find it on skate boards to keep your feet from slipping. I use it on my planer crib.

[chrismp]

For planer cribs griptape works well since the planer rollers themselves are pushing the core down into the crib, but for a router bridge or cnc you need something to hold the core down.