Waste board/work holding idea


(Tom) #1

What do you all think about this waste board/work holding idea? Anyone using something like this (without aluminum t slot)?

IMG_5757

My main concern is if the mdf is strong enough. To me the method used in the picture is much stronger than in the video. I see pros and cons to both methods. This will be the cheapest option for my new xxl - so I’ll be giving it a try.


#2

I would guess that the MDF will fail if you do not use something to spread the load. There isn’t much eat on that bolthead under the MDF lip, and the lip is out fairly far.

The optimal situation is a) large contact area between the bolthead (or nut, if that is what is used) and the under surface of the overhang, and b) contact as wide as possible-- get as close to the inside corner under there as you can-- to reduce the bending moment trying to open up that inside corner.

This is most easily done by making up rectangular washers that just fit the slot and the bolt will grab. For this application, aluminum plate is fine, steel sheet is fine, and even a hardwood would probably be ok. Thickness as thick as will still let the bolt/washer slide freely in the slot.


(Phil Thien) #3

Get some t-slot bolts from Rockler, or even toilet bolts from the hardware store, to get more purchase on the MDF.


(Tom) #4

Now I’m rethinking this idea…

Liking the bench dog work holding method too.


(Evan Day) #5

If you have a threaded wasteboard already, here is a series of cam clamps I made. They are based on those videos, but I tried something different. Holes are for 1/4-20 bolts which then match my threaded board. By using the bolts, the cams don’t get loose at all.


#6

Hold downs (straps) have a prominent place because they are secure, when properly installed, and provide positive pull down to the bed. Disadvantages include that they can be difficult (or impossible) to keep entirely below the top surface of the stock.

Cams are useful for fast setup and easy positioning, especially for repeatable positioning sine they provide lateral force against a stop, and are also easier to set up so that they are entirely below the stock surface. They can, on the other hand, cause stock to tend to lift, and are more likely to work free than bolted straps.

Both have advantages and disadvantages, and neither is inherently better.


(Carl Hilinski) #7

Just so it gets mentioned in a topic on work-holding, vacuum clamping has a place. I do a lot of repetitive pieces that are milled from scrap…think cribbage board style scoring track with peg holes. Each one is 3 x 4.5 inches. It’s so much faster to replace a finished piece with new stock when you don’t have to work with mechanical clamps. I just release the vacuum, remove the piece, put on a new piece of stock, start the vacuum and start the CNC. It takes only seconds. I don’t have a full vacuum table; I have vacuum “pods” that I made that look like these https://www.veneersupplies.com/products/Podz-Vacuum-Clamping-Jigs.html .


(mikep) #8

I’ll throw in a tip I learned from watching some milling machine videos - use a large ball bearing (or a largeish metal dowel) between the material and the side clamp. The side clamp will often “lift” the material a little when it clamps. The ball prevents that, but can leave a mark on the edge of the material. For us, usually that mark isn’t of any concern because it’s out on waste.