CNC Routed Salt Box #2: New Vacuum Clamp & Ooops

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Blog entry by SPalm posted 11-12-2011 03:07 AM 9164 reads 0 times favorited 33 comments Add to Favorites Watch
« Part 1: Creating the Top Part 2 of CNC Routed Salt Box series Part 3: Redesigned Vacuum Clamp »

Ever have one of those days, where you take one step forward and two steps back? I finally get a day off from work and proceed to walk backwards.

I ordered some special foam tape from JoeWoodWorker that is intended to hold a vacuum. And since the shopping basket was already open, I threw in a bunch of brass hardware and tubing. Today I drilled a 2” long hole in the side of a HPDE plate and threaded it for a hose coupler. I then drilled a small hole on the top that intersected the long hole from the side. I put some of my new tape on top, and connected the vacuum pump. It worked pretty well, but leaked a little bit when trying to hold wood. So I put some sanding sealer on the blocks, let them dry, and I got much better results.

Here is the new vacuum clamp:

My first attempt at using it did not turn out so well. The foam held the bock down, but it was able to twist some. This really showed up in the routing. So I came up with a board that I could press up against the block. This helped keep the block from twisting quite a bit.

Here is a video about how things went bad. I sped up the video so it is only a minute long (you can only take so much of this). Watch the silver part of the router bit just under the collet and before the red bit. It seems to grow in length as the routing gets going. The bit slipped. So now I have a nice profile routed into one side of the HDPE, and two ruined cherry blocks.

Oh well,

-- -- I'm no rocket surgeon

33 comments so far

View Joe Lyddon's profile (online now)

Joe Lyddon

10124 posts in 4081 days

#1 posted 11-12-2011 03:20 AM


Looks like you stopped just at the right time!

Oh WELL… is right!

Back to the drawing board?

Old Fashioned Clamp? “L” type clamp?

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:"

View lanwater's profile


3111 posts in 2963 days

#2 posted 11-12-2011 03:33 AM

Hi Steve,

You are almost there. I never really trusted vacuum hold downs.
how about small mchinist vise you can clamp down?

I must say that your system is cleaner visually.

-- Abbas, Castro Valley, CA

View JL7's profile


8667 posts in 2994 days

#3 posted 11-12-2011 03:34 AM

Hey Steve – thanks first for sharing that this could happen to you…...the vac clamp is tight but the pressure from that bit is likely just to much…..I know you well enough now, you will overcome…..please keep sharing.


-- Jeff .... Minnesota, USA

View SPalm's profile


5320 posts in 3911 days

#4 posted 11-12-2011 03:43 AM

I guess it was not really the vacuum clamp that failed, but the router bit became loose and slid down, which then let the vacuum out. Ya fix one thing, and another comes up to bite. Arrgh.


-- -- I'm no rocket surgeon

View rance's profile


4258 posts in 3190 days

#5 posted 11-12-2011 03:47 AM

Who says you can just start a cnc and just walk off? Yeah right. All I gotta say is 1) Eeewwwwwww, and 2) glad nobody got hurt. Thanks for sharing Steve.

-- Backer boards, stop blocks, build oversized, and never buy a hand plane--

View Pete Jansen's profile

Pete Jansen

250 posts in 2950 days

#6 posted 11-12-2011 04:08 AM

Pretty cool. I’ve built a cam type clamp to hold blocks at the bottom. It works ok, but not great,
the cams are made of plastic and work their way loose with the vibration of my router table.
Routing the profile on a small box is a tricky one, I just end up using soft jaws in a vise to
hold mine now. I make the jaws out of HDPE and I don’t worry about the end mill hitting them
on the finish pass. That works the best for me. I’d like to try some vacuum veneering some time soon
with a plastic bag setup. Glad to see you dusted off your router table though. I’m working on
a sea salt box this weekend myself. Keep up the good work.

-- Lovin' sawdust in beautiful Fort Collins, Colorado

View Snookie's profile


173 posts in 2521 days

#7 posted 11-12-2011 04:19 AM

This is all beyond me! I am just a simple did it myself girl! :-)

-- Snookie, Jasper,GA

View Joe Lyddon's profile (online now)

Joe Lyddon

10124 posts in 4081 days

#8 posted 11-12-2011 04:24 AM


I replayed it and stop-started per mouse click/click… the bit went through the bottom while it was on the left side… hen started to really start moving the blank when getting to right side.

I guess you will have to Route in timed sessions (time-outs) where you can do Safety checks on Tightening bits, etc. (??)

-- Have Fun! Joe Lyddon - Alta Loma, CA USA - Home: ... My Small Gallery:"

View Karson's profile


35126 posts in 4430 days

#9 posted 11-12-2011 06:12 AM

Steve: That’s really scarry to have a router bit move in the chuck.

Was it oil or just not tight enough. Today, I saw two vacumn hold downs pick up a 2” plank 12’ long and 36” wide. Each vacuum pad was about a 12” circle with foam on the outside edge. It picked the board up and moved it from the sawmill to the holding cart. As easy as could be.

The vacuum area that you had should be able to hold 40-50 lbs with ease, however it might want to move as you experienced, requiring the block to keep the movement in check.

Here is a picture of Lee Jesberger holding a piece of wood with a small vacumn clamp.

-- I've been blessed with a father who liked to tinker in wood, and a wife who lets me tinker in wood. Southern Delaware soon moving to Virginia †

View Bob Kollman's profile

Bob Kollman

1798 posts in 3220 days

#10 posted 11-12-2011 08:55 AM

I use vacum on my lathe all the time at work, judging by the size of the fiture you were
probably holding on by a good 500-1000 ft lbs, but it also looks like you had your block
halfway off the vacum plate. Better wach your Z’s mister!!!! Look at the bright side, with that
big gouge in your vacum plate your next block of wood might hold better!!!...:)

-- Bob Kenosha Wi.

View BritBoxmaker's profile


4611 posts in 3065 days

#11 posted 11-12-2011 05:10 PM

Oops indeed. Better luck next time, Steve.

-- Martyn -- Boxologist, Pattern Juggler and Candyman of the visually challenging.

View Lee A. Jesberger's profile

Lee A. Jesberger

6859 posts in 4009 days

#12 posted 11-12-2011 05:10 PM

Hi Steve;

That could have gone a lot worse. I would walk away from that feeling quite lucky.

Thanks for keeping me incognito, Karson. I wouldn’t have recognized me. I take it you were at Hearnes Hardwoods when you saw the vacuum hold downs. I’m sure you guys had great time.


-- by Lee A. Jesberger

View kiefer's profile


5619 posts in 2696 days

#13 posted 11-12-2011 05:44 PM

Steve I am sure you know all of this This problem of bits coming loose is generally caused by inserting the bit all the way into the chuck and not pulling it back out a 1/16 ”, another problem I have run into is by not cleaning the rust protection off
the shaft on a new bit.
When I install a new bit I clean the chuck out , clean the bit and use a o ring to prevent bottoming out of the bit.
I would not blame the hold down in this case .
Hope the next box goes well !


-- Kiefer

View SPalm's profile


5320 posts in 3911 days

#14 posted 11-12-2011 06:32 PM

I don’t know why the bit came down. It is an old bit that I used to cut all the other boxes, so no grease stuff. I always insert a bit all the way and then pull it out a bit, so it was not that either. So I guess that I did not tighten the collet enough. Or the collet is bad, or the bit is bad (?).

But the vacuum plate worked. And of all times to get a loose bit. At least I filmed it :)


-- -- I'm no rocket surgeon

View Bob Kollman's profile

Bob Kollman

1798 posts in 3220 days

#15 posted 11-12-2011 08:39 PM

Wow I didn’t see that. Should have read your comments more carefully.
Why it came loose is a good question. Maybe you would have better
results with a standard End Mill. Also look at reducing your chip load.
Reducing your depth of cut by 25%, reducing your feed rate by 25%
from that point you can work your way up. Well you probably already
thought of all that, hope your next run is a success!!!

-- Bob Kenosha Wi.

showing 1 through 15 of 33 comments

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