So make the whole MDF box in a way that would be easily removable!
EDIT: The main advantage would be that you'd guarantee that the entire PCB would be laying flat across the surface!

Kind of a pain for tool change. I could make 3 in a job.

 

I once saw a machine that used a vacuum pump to suck air from underneath a piece of MDF, its porosity would then help hold the work piece while it was being drilled and routed on. No clamps needed!

Yes I have installed those, but you need a proper Vacuum pump, not a shop vac etc, as they will overheat and burn out, as they need the air flow for cooling.
The fittings can be common PVC pipe.
Max.

 

Kind of a pain for tool change. I could make 3 in a job.

Yes, it could be a pain... I'm just brainstorming here...

 

they will overheat and burn out, as they need the air flow for cooling.

good point

 

Yes, it could be a pain... I'm just brainstorming here...

I think the vacuum table might not be doable for me.

The look awfully thick.

http://makezine.com/projects/make-4...ot-desktop-universal-vacuum-hold-down-system/

 

I think the vacuum table might not be doable for me.

The look awfully thick.

http://makezine.com/projects/make-4...ot-desktop-universal-vacuum-hold-down-system/

How much did that machine cost you?

 

How much did that machine cost you?

Can't remember. Around $400 US. The drilling alone was worth it to me. My hand eye coordination and shaky hands just can't get those ic sockets and connectors perfectly straight. Now I can!

 

I might go to the hardware store tomorrow and see if they have something that can grab those rails. Some sort of clamp.

 

This is the type of toggle clamp I referred to earlier.
Max.

 

This is the type of toggle clamp I referred to earlier.
Max.

I was thinking along the same lines... I think you could order them through Grainger

 

Unfortunately they do not include a tap set for each size, when tapping you need to use a taper tap first followed by a second and plug or bottoming tap

As a 50+ year die maker, that is a fallacy. That was before the advent of spiral point taps. I've never even seen a 'taper' tap in industry. Except in an Acme screw thread tap set. There it is needed because of the amount of metal that needs to be removed in the thread.

 

As a 50+ year die maker, that is a fallacy. That was before the advent of spiral point taps. I've never even seen a 'taper' tap in industry. Except in an Acme screw thread tap set. There it is needed because of the amount of metal that needs to be removed in the thread.

I always use tap #2 directly on most metals, and then the bottoming tap, if needed. I seldom use tap #1, except in hard metals and maybe some stainless steels.

 

Also a two flute tap cuts better than a four flute tap. And if you break one in the hole, it's easier to remove.

 

good point

I am going with your original idea. Sandwich the "clamps" between two bars that will run along the X axis. I think I can make it so the top bar can be loosened to allow movement of the clamps. No tapping should be needed. I think I can make this work. I might need a bit more material.

 

As a 50+ year die maker, that is a fallacy. That was before the advent of spiral point taps. I've never even seen a 'taper' tap in industry.

What can I say? My machine shop supplier can still sell me the 3 of a (US made) set.
Max.

 

At a party so I can't sketch it. Cut a MDF sacrificial surface, THAT JUST FITS BETWEEN TWO SLOTS ON THE EXISTING TABLE.

Make aluminum or steel T blocks to slide in the table slots. Tap a hole in these blocks.

Make two cross bars, that extend beyond the slots. Drill a hole in the slot centers, that bolts will fit through freely.

Place your material on the table. Put the cross bars on top, aligning the holes with your T blocks in the slots.

Screw the bolts through the cross bars into the T blocks. Tighten to clamp the work piece.

Voila!

 

At a party so I can't sketch it. Cut a MDF sacrificial surface, THAT JUST FITS BETWEEN TWO SLOTS ON THE EXISTING TABLE.

Make aluminum or steel T blocks to slide in the table slots. Tap a hole in these blocks.

Make two cross bars, that extend beyond the slots. Drill a hole in the slot centers, that bolts will fit through freely.

Place your material on the table. Put the cross bars on top, aligning the holes with your T blocks in the slots.

Screw the bolts through the cross bars into the T blocks. Tighten to clamp the work piece.

Voila!

I don't know why I did not think about this before! It is so simple. I sure hope the metal shop takes back that far of aluminum I bought.

 

I don't have a proper mill but I bet I could drill then file a slot into those cross bars. I could then place two other bar across the first two forming a square that I can adjust. I will use flat bar instead of the square that I bought.

 

This is going to work out well. The local home supply store has MDF in 7.25" boards. I will get them to rip it to size and I will have a lifetime's worth of spoils boards.

https://www.lowes.com/pd/Actual-0-656-in-x-7-25-in-x-8-08-ft-Medium-Density-MDF/1000033719

And because the board won't be as wide as the original table, I will have a tool change area. My current spoils board is smaller and what I do now is to modify the G-code to take the machine to a spot where there is no spoils board giving me a bit more room for tool change.

 

Rather than MDF, I'd use Masonite. It's thinner and just as flat. That table looks like it's made of a generic 80-20. Most people use carriage bolts instead of buying the 80-20 bolts or making something to fasten stuff to it. https://www.8020.net/

One of the places I worked we had to make test samples for a company, tensile samples of carbon fiber material. It had to be ground to a very specific thickness and size. No way to clamp it and grind it. So we used double sided tape, carpet tape. If I was doing a PCB milling I'd use double sided tape to hold it down. No clamps to get in the way. To release the tape you only need to heat it with a hair dryer. As long as it isn't stuck down for a long time, and the adhesive is still fresh it comes up real good. It doesn't work that good if the adhesive is dried out though, and that takes longer than milling a PCB. Any adhesive that still sticks will come up with acetone, Goof off or the like.

And both the tape and Masonite or MDF are surprisingly consistent in thickness. As good as or probably better than the PCB board.