Material Hold Downs, Jigs and Things

[srwtlc]

I wanted to start this thread for two reasons.
1)To discuss various ways that we have come up with to hold down material for cutting, mainly odd or small parts, by use of various jigs or the like. (Happiness is a well made jig that works well) ;^)
2)I have need of ideas on how to hold some 5" x 7" blanks to cut a circular pocket in the middle, trim, radius the corners, and round over the edges of them with an ovolo bit.

Because of not being able to hold them from the top, and vacuum not being strong enough without edge contact, the one way I keep coming back to is to screw them to a backer board using a template for alingment then placing the screwed down group on the table in the same place every time by indexing it. I have to do 700 of these so I'd like to come up with something quicker than two screws in each blank. Anyone have some other ideas?

I'll make my contribution to the jig discussion with my jig for holding blanks for boxes that consist of two 5" x 8" x 3/4 pieces, one is the top with a deep recess and one is the bottom with a shallow recess that gets either a pocket for a badge, knife, etc. My jig is a two-part jig that is sandwiched together. The top layer is 3/4" thick that has 20 shallow 5" x 8" pockets in the top with a slightly smaller rectanglar hole all the way through. This layer is on top of another piece of 3/4" material that has a manifold cut in it connecting all the openings to vacuum from a shopvac. This setup works very good for this type of project with a master file that allows me to place any type of pocket or whatever in all 20 pieces quickly.

So how about it, any other ingenious jigs or methods out there? Any suggestions for my other project?

Scott

[gerald_d]

Scott, your 5" x 7" problem:

What material? How thick?

If, for example, they are pine and 0.5" thick, we would cut them out of 6" x 0.75" planks. Hold the plank down with 2 G-clamps, cut everything 0.6" deep (in a very careful sequence), then run plank through a thicknesser to remove the bottom skin.

[davidallen]

one trick I use when machining metal is hot melt glue. the piece to be cut is glued to an oversize metal plate. the metal plate is then fixed to the table in any convienent fashion. after cutting, the metal plate is warmed enough to release the glue and the part is removed.

if you have a finished back side, the glue may be hard to remove. if it's a felt back, after sanding and finishing the front, the felt can be ironed on with the residual glue.

[rgengrave@aol.com]

Scott I use T-Track, I can hold anything from 1"x1" to 6 inches tall.
With T-Track you do not need a vacuum table or any other hold downs, you will be able to cut all the way thru the material too without it ever moving.

Ron V

[steve]

what about the plastic nails fired in from a nailgun instead of the screws?

[jorgy.tucson@worldnet.att.net]

Add additional cutting zones (1 to 3)so the router never stops while you change parts. Program so that have no wasted tool path. Limit z up to just clear the part. Set move and jog at max speed without sacrificing cut quality. I would suspect that you can do 700 in about a day and a half.

[srwtlc]

Gerald,

My material is red oak at 3/4" thick. I thought about cutting them out of boards, but the ovolo bit I want to use has a 1/2" diameter at the tip which would require a lot of waste. I can yeild better by ripping/crosscutting my blanks to 1/8" oversize and then having the Shopbot do the rest with the ovolo bit that can do the three cuts needed.

Ron,

I like the idea of the T-track. I've been thinking about something like that because I do so many different things and most are smaller items. My current table is starting to look like a pincushion. Is your T-track of aluminum, and do you have it flush or below the surface? Do you have some type of low profile clamps then?

I'm considering using two, what I would call palettes, that I can load up with as many as I can as close as I can with a template and then place them on the table at two different positions. That way I can be loading up one while one is being cut. And like John said, optimize the tool path.

Scott

[rgengrave@aol.com]

Scott send me an email and I will get some pictures for you, it will show you how you can use your whole table.
When you finish 1 peice just remove it while the rest is still cutting, then just add a new peice for when you run the file again.

I did 25,000 letters for Lowes last year doing it this way, it is a time saver and you will never mess up your table with screw holes

Ron V

[gerald_d]

Hi Ron V, I am also curious to see how you use "T-track" to hold a 5"x7" part so that the whole outer perimeter is clear for a cut right around the outer edge. My e-mail is mechtron@iafrica.com.

Scott, Have you considered the depth (z) control for the ovolo bit? If you want the radius to meet the top surface exactly (without a rebate mark) then it is essential to set the z dimension very accurately. On one of our jobs it was easier to do the ovolo work afterwards on a table router (the client-supplied blanks were of varying thickness). An ovolo with a ball-bearing on the nose works fine for this. The ShopBot doesn't automatically replace ALL traditional routers.

Theoretically, using a high vacuum (ejector or piston/vane pump) with a rubber inter-mask/seal will give you more than 300 pounds of clamp force. However, vacuum would only be considered as a very last resort - the special masks, seals and pumps tend to be very specific to a particular job and your 700 pieces still sounds a bit too low for such an investment/(experiment).

[gerald_d]

Thanks for the photos Ron V. I think you missed the fact that Scott wants to cut his blanks 1/8" oversize and do all the finishing in the ShopBot. In other words, he wants access to all the edges (the whole perimeter) right down to the full depth/thickness of the workpiece.