Hold Downs?

[dweyant]

I have a question on hold downs...

I have the MDF HS-1, and I'm having a tough time figuring out strategies for holding material down.

I'd be interested in hearing what you are doing to hold down your pieces, what works, and what doesn't.

Thanks!!

-Dan

[georgemyers]

Dan

I hold down methods I have tried.
1. Double-sided carpet tape. Big minus on this. I had a work piece or two come lose.
2. I tried these. www.woodcraft.com/product.aspx?ProductID=148122&FamilyID=20317

They work great but get in the way of the dust boot if your are not careful. I mounted t-track on each side of the router.

Most times I use a brad nailer (air) and shoot a brad in each corner when I use the sacrificial spoiler board.

[dweyant]

George,

You have the Aluminum top correct?

So, do you generally mount a piece of MDF on top of that?

What thickness do you use?

-Dan

[georgemyers]

Dan

Yes, most times I have the MDF on top of the aluminum top. The one I have now is 3/4 inch thick.

I made a mistake using 3/4 inch, that plus the thickness of the aluminum top makes for a short Z travel depending on my work piece. My next ones will be 1/2 inch or less in thickness.

[plasticsteve]

While surfin at work today I found this:

www.cnc4free.org

click on PROJECTS on left

then at the bottom right click on MILL CLAMPS

Ill give this a try this weekend. Kinda feel stupid for not thinking of it myself now.

[Nick]

romaxxcnc.proboards.com/index.cgi?board=general&action=display&thread=147

[greggarriss]

Hi guys,

Here's a fun one.. I'm trying to cut a large number of small parts from sheet veneer. Of course, even with tabs, they tear loose about the time the router is almost done with the part. Any ideas? A vac table would be nice but I don't have the bucks at the moment and this is an infrequent thing to work on anyway. Carpet tape seems to get stuck on the end of the bit and twist loose. Anyone seen a removable adhesive?

Thanks,
Greg

[Nick]

Do you cut the same pattern often? You could make a template hold down that laid over the whole sheet. Do you leave tabs to keep the cut outs connected to the stock?

[greggarriss]

We usually make 1000-1500 fishhooks every summer to give away at festivals here. They're about 2" x 1.5" with some nice curves. But using the CNC, they break loose just before the router closes the loop. Scraps the part when that happens. I've been trying a few things like tabs ( 8 so far ) .1" wide by .035 thick ( Vcarve Pro ). 30mm/sec feed rate. I'm considering two passes to keep the load down. The material ( mahogany veneer ) is .225" thick

[Nick]

0.225" thick? Yeah, that'd need more than 1 pass if you dont want the edges ragged. Tabs sound good, but 1 thing I found out is that I didnt need nearly as many tabs as I thought.

[bjenkins]

This trick may not be helpful in your situation and I bet you have already thought of this but I'll mention it because it is working out for me.

I cut some small parts that are too small for tabs by cutting them on thicker stock and then I use a band saw to cut them out of their nest. Then I sand them to the final thickness. Ron mentioned this idea to me when I was trying to determine if such small parts could be made with the CNC. I use a push pad from my jointer to hold the wood against the saw fence and also use a push stick to move the wood through the saw.

BillJ

[greggarriss]

Wouldn't it be easier to sand the nest to the final thickness first and then do the cut out?

Multiple passes seems to be keeping the load down. I was hoping to get a little more speed and less handwork for these things using CNC. After three years of this, I can cut them out on a bandsaw by hand in under a minute each and they're ready to go. With multiple passes, I'm right at that time and still have to clean up the edges.

[bjenkins]

Yes that does sound like a good method. I think I'll try cutting my small parts without tabs and then sanding the top to get rid of any fuzz and then sanding the bottom to release them. I think I may like your suggestion better than the band saw cut out method.

I like the band saw method but the easier the better. If you come up with a hold down trick, I would like to learn about that also.

Thanks,
BillJ

[Nick]

Its called 'onion skinning' when you leave a very thin continuous tab around the whole part (reminiscent of an onion skin ). Google "onion skin cnc" and you'll probably come up with a lot of ideas.