Marking out holes, for setting out/welding table

[Shox Dr]

Reading on another forum, about a guy wishing to build a setting out/welding table. wondered how to make out the grid and drill Quote "I will be using a waterjeted layout jig to transfer punch all the hole locations, but does anybody have any suggestions on how to line up the mag drill with an annular cutter over the hole location after I have transfer punched it? I could always change out the cutter with a drill chuck, use a center finder to make sure I was lined up....


Is so happens I building a table as well and have given the marking out and drilling of the grid, some thought and the best I have come up with so far is.

Clamp bar to longest edge, drill 1st hole then using a milled sq former to the dimensions you require C-2-C less half the distance to the centre of the mag, and the diameter of the hole you are going to drill.

Then placing a pin in the 1st hole and butting and clamping the former sq to pin and bar. You can then cut the next hole, etc etc. Once the first row has been drilled place pins in the holes and butt the bar to it, the next lot of holes can then be drilled. Remembering the former will have to be modified to take into account he Pin dia, and bar.

Hopefully at the end, the table will have a sq grid.

If that makes sense.


Any comments/suggestions

 

[Hitch]

Why can you not just mark out and drill....line up the pin with the centre dot...
Quality or the rotabore will determine the accuracy....dont want an old wobbly one if you are going for tight tolerances...

.

 

[Shox Dr]

Accuracy, is my biggest worry. Making out every hole is an opportunity for error, then the accuracy in centring the mag drill

 

[Shox Dr]

As you say Mag drill condition will only add to the error

 

[Hitch]

You could get the template made up then just broach through it....thickness needs to half sensible then though.... How big/thick is this table going to be?

 

[Shox Dr]

Not me using the template fella, that was the other guy I was quoting.

Table will be 8x4x5/8"

 

[Hitch]

I wonder if its worth you giving parkers or similar a tinkle, they will have a machine for doing such......accuracy would be second to none on the hole centres then....

 

[Shox Dr]

Parkers?

 

[Hitch]

Parker Steel, or a few others that have a drilling line, probably get an 8x4 through on a beam drilling line, not 100% on that mind.

Had an email from them back along....hang on....

 

[Hitch]

Here you are, http://www.parkersteel.co.uk/Drilling

 

[Welderpaul]

Thats some bit of kit.

I'd buy the plate water-jet/plasma cut. Either get the holes cut through to the finished size, or if you want to drill them, get them cut 2/3mm dia so the broach pin drops into the hole to centre the cutter up.

 

[Shox Dr]

Here you are, http://www.parkersteel.co.uk/Drilling

I already have the plate

 

[astro_al]

I don't see what the problem is. The centring pin of a mag drill will ensure I is concentric to the centre punch marks. I would just mark it out with engineers blue and a good scribes, then an optical centre punch for the drill to follow then just mag drill the crap out of it. Easy.

Al

 

[Drains]

Am I missing something? For accurate mag drilling, I've always centre punched, drilled to the dia of the pin, a few mil deep ( for centring and allowing the slug to be pushed out) and broach away. For better centring use a lathe centre drill.
I'd expect a guaranteed accuracy of +/- 0.5mm. Anything better required, use CNC plasma or an enormous mill

As Al says, mark first with blue if required, off a datum ( if the hole patterns are symmetrical use centre lines as datums). Don't mark hole to hole as errors will compound.

 

[Shox Dr]

No you're not missing anything fella, just thinking out loud, on a boring drunken Saturday night .

I've only one shot at this and I have never needed to markout something so large to such critical accuracy.

I haven't a straight edge that long, so scribing 8' long lines is out.

 

[mike os]

not laser/plasma/waterjet it? or too big for most?

I would have thought that the simplest ( probably cheapest too) and most accurate?

 

[inchpincher]

How do you decide on the number of holes you'd like in the plate?

Sorry no help regarding the drilling