Tinker's Construct is a remarkably well documented mod compared to most Minecraft mods, especially those in FTB. In fact, it even gives you pretty awesome in-game manuals. However, it took me forever to figure out what you actually have to do to get making custom tools.
As you probably gathered from the first in-game book, you need some workshop blocks. However, what you might not have understood is that, to start out, you just need a Stencil Table, Part Builder, and Tool Station. They're all just wood. Make a couple of spare blank patterns as well.
Shove a blank pattern in the Stencil Table and click Next and/or Previous until you find a fragment that looks useful (I recommend pickaxe head). Take it out. Shove that into a square slot in the Part Builder and some wood or cobble in the ingot-like slot. Take the new piece out.
This does not work with metals. For metal, you need a Smeltery. You can do similar things using just this set-up to make pretty lame composite tools if you figure out the Tool Station. In the Tool Station, you click the type of tool you want to make on the left and then put in the components in the slots which will appear.
However, I think it's pretty easy to advance to the next stage: smelting. Gather a whole bunch of clay, sand, and gravel. Combine it into grout and smelt that into Seared Bricks. Create exactly 18 Seared Brick blocks, 1 Smeltery Controller, 1 Seared Tank, 1 Seared Faucet, 1 Smeltery Drain, and 1 Casting Table. Put a 3x3 square of the Seared Brick blocks on the ground to start. Then, up one level and not directly above the bricks, place the Controller, Tank, and Drain facing in. Complete a ring around the outside (corners unnecessary) with the rest of the bricks. Attach the Faucet to the outside of the Drain and place the Casting Table directly underneath it.
Once that's all done, grab a bucket of lava and use it on the Tank. It should light up the Controller as well. You now have a functional Smeltery! Now, find those tool parts you made earlier and right-click the Casting Table with one. It should insert itself. Pop in 2 gold ingots or 1 ore into the Controller and let it melt. Right-click the Faucet and the liquid should pour into the Table. If you've set things up correctly, it will cool after three seconds, producing a solid cast around the part. Pop both of them out, and you have a cast! I'm fairly certain you can just throw out the cheap part.
Now, it's time to make a part with metal. If your Smeltery still had liquid metal in it, break and replace the Controller. Casts must be filled with a different material than was used to make them. Put in metal of your choice (I did iron the first time). Pop the cast back into the Casting Table and, once the metal is liquid, right-click the Faucet. If it doesn't cool into the part after a few seconds, put in more metal. Once solid, pop both of them out and you have a metal part!
Once you've made enough parts for a tool, put them together in the Tool Station. You can also modify them there by adding unusual substances found in the second book you got.
