Sewing help needed please! I am confused with correct way to cut lovely material.

[OldCrowMedicineShow]

I have not made anything from a pattern since school many years ago ds has a school ceilidh tomorrow and they need to wear tartan.
I found a beautiful piece of good wool tartan plus have a waistcoat pattern. Everything is ready but before I cut the tartan, there is a correct way and a wrong way to cut. Words like 'bias' 'selvage' and nap lurk around but I don't remember anything about them.
I am also going to attempt making a tie.
The same selvage/bias/nap confusion for some silk type material for the back so it hangs nicely.

Please help!

[Orangeanddemons]

Selvedge is the neat edge running down the long edges of the fabric, this runs parallel to the grain. Tartan doesn't generally have a nap or a pile, but can have a one way pattern. Also make sure you match the pattern on the seams and cf up

[Orangeanddemons]

The back will be cut on the bias, which means place the grain at 45 degrees to the selvedge

[OldCrowMedicineShow]

Thank you!

I pinned then cut the back pieces, the material is a silky polyester with silk slubby bits and it is quite heavy so sits beautifully.
Am gathering up courage to cut the tartan but there is a lot of material for matching up the check. It is nerve wracking, though!

Should I put a little iron interface (lightweight) around the shoulders? It says to interface the entire back but the material is fairly stiff anyway plus doubled (the two parts of the back).

[Orangeanddemons]

The most important nit to match up is the cF. Make sure you allow for seam allowance.

You could interface the tartan shoulders, neck and fronts. But I wouldn't interface the back if it is all of the silky stuff. Actually, I would, I'd put some around the back neck.

[OldCrowMedicineShow]

Thank you, Orangeanddemons.

I have hit a huge problem. The new patterns do not include seam allowances and I'm not sure how to get an accurate edge. How do you do this, please? I don't have a stabby wheel and am desparing now
How do you mark exactly what is on the pattern from the pieces which have been cut out?

[Orangeanddemons]

You will gave to measure the seam allowance. Pin the pieces on and measure1.5 cm out with a tape measure and tailors chalk all the way round.

You do tailor tacks for pattern markings or just poke tailors chalk through the pattern piece to mark markings.

[KatyN]

Tie two pencils together with a rubber band and draw around the pattern pieces with them. The outer line is your seam allowance.. Measure what it is and then find the corresponding line on your machine!!

[OldCrowMedicineShow]

Geniuses!

[FuckOffJeffrey]

A bit late to the party and you will have sewn your waistcoat by now but for seam allowances I tape two pencils together and draw around the pattern again (I save the original pattern and trace a new one in tracing paper or greaseproof paper) It gives a nice even seam allowance.

[OldCrowMedicineShow]

Thank you FuckOffJeffrey

Not late to the party at all, the waistcoat is 'resting' in the sewing pile and I had to wait for a while until a tracing wheel then dressmaking carbon paper arrived then I lost the pattern my nerve. Child will be a fully grown adult by the time this project gets finished.