shopbot CNC version of my cracker holder

Dave Kauffman

Member
Messages
180
Location
Fort Washington, PA
A while back I posted a method of making one of my best selling items at shows, a simple cracker holder. Update, I make them on a Shopbot CNC router now, and thought some might like to see the process.

Here is the bot. It comes from Shopbot with a 1/2 inch thick aluminum table drilled with 1/4 x 20 holes so you can attach your own table depending on what kind of hold down setups you will be using. I opted to build this T-track table on it because I will be using a lot of product specific jigs and needed lots of options orientation-wise to be able to attach the jigs to the table. So far it has worked out great.

Here is the bot with the cracker holder hogging-out jig attached to the table ready for a blank.

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Here is a pic of that jig loaded with a blank ready to hog out. That small piece of aluminum angle iron in the bottom right corner of the jig is how I orient the router/bot to the jig when I set up for this job. I'm using a 1/2 inch solid carbide spiral upcut bit for the hogging, and I move the router close to the area of the angle, then nudge the jig till it's touching the inside of that angle. I then tell the bot that that point is zero. The program I wrote assumes that, and it then moves specific distances in the x and y axis to do the hogging. You can't see the bit in this pic because I still have the dust collector shell around the bit. I will remove that for a few pics so you can see the action better.

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I played around and tried lots of methods to actually hog it out, and through trial and error came up with a method that make the cleanest cuts in most kinds of wood without the bit burning any corners or bottom. Method I came up with first goes around and bores a hole at each corner, and then works around the inside of the blank in 5 left and right passes to clean out a layer. The area I am hogging is 7/8 inch deep, and I found that I could do the whole hog out with one 7/8 inch deep cut, but I had to slow the bot down to do that, and it tended to burn some wood like maple and cherry. So I decided to write the program to do the hog in 4 "layers"... 3 hogs each 1/4 inch deep, and then one final 1/8 inch deep final hog. At the speed I set it for this job, it takes about 2 minutes start to finish all four passes.

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Here is the finished rough product ready for the next step, sanding and 1/8 inch roundover all around, then drill the hole in the handle, and finish it with walnut oil. The one on the bot is cherry, the row of holders on the table are already oiled, they came from red oak I milled from a log this past January. It dried fast, was down to 14%MC already, and for this project that's fine to use right off the stickered pile.

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Very cool, Dave. Someday, if money and space permit, I'd love to have a CNC setup. Properly used, it seems it could pay for itself many times over.
 
Dave, I like the jig and the cam clamps. Will have to consider that when I've got several parts to cut out on mine next time. I built my cnc from scratch. Been collecting parts for a larger one, somewhere around a 4' x 8' table. Figure I'll have about $2000 in it when done, not including software.

Thanks for posting, great info.
 
I made those cams from osage orange because it's so strong and tough, and they work great. They are only 1/8 inch out of round so they put a tremendous force on the blank. They speed things up because they are quick to use but yet they hold as tight as anything else. Because they put so much force on that blank though, I had to redo the stop behind the blank. Originally it was just glued and screwed, but the cams had so much force it kept pushing that stop to where it started to move. I then dadoed it into the base and glued and screwed, and so far it hasn't moved.
 
Dave,

That is one very cool machine. Looks like it could crank out a lot of those trays in an evening.

Rennie, that's one of the reasons I invested in a bot... besides having plans for things like wooden gears for an all wooden clock, things that would take way more man-hours than I could charge at shows and make any money, I also wanted to use it to do some of the monkey work like hogging out the center of this thing. If I make a run of blanks and just keep feeding the bot, it takes about 2 1/2 minutes per taking into account loading and unloading the blank, restrarting the hogging program etc. So I can knock off 20+ of these per hour. Added plus is during that time while the bot is actually doing it's thing hogging, I'm stepping 10 feet to the right and using that Mill/Drill machine you see in the background to drill the hole in the handle and then countersink it. So I can sortof multitask. Catch is I do have to keep an eye on things, I can't leave the bot unattended... there are a dozen things that can go wrong. Router bit hits a knot and the blank flying apart, or worse case a piece gets stuck and starts burning. At 20000 rpms, it doesn't take that bit spinning in one spot very long before bad things start to happen. I have to be close to that big red cut off switch at all times.
 
Excuse my ignorance, but what is a cracker holder?

A device to hold crackers (fireworks)?
A device to hold nut crackers?

Thanks
It's simply a holder for round or square crackers... here in the states saltines are standard 2 inches, so that's the inside width of my holder. This one is made from redcedar. For those who are interested, my cherry holders sell the most, followed by oak with redcedar a close third. For whatever reason, maple, unless it's curly or birdseye, doesn't sell very well with this item.

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