Hello and welcome to the forum. Dave here and I am working on my first rifle, like yours a Chambers Lancaster. The only place you will likely use a rasp is on the butt plate install. The Chambers kit stock is pretty close to final dimension and other tools can get you there fairly quick. I purchased an Auriou brand rasp from this site:
http://www.lie-nielsen.com/catalog.php?cat=543Mine is a 10 inch, 9 grain – it exceeded my expectations in butt shaping work on the Lancaster and I am sure would be very useful if working from a blank.
The most useful chisels I have found for my build are the smaller flat chisels, 1/8th inch to ½. One chisel I bought from Track of the Wolf was a ¼ inch wide crooked neck made out of bar stock ( I have since made a couple of others like it for other jobs), I used it a lot as a scraper and a chisel for finish bedding of the barrel. For gouges again the smaller sizes are useful but choice, since there are so many available, is according to what you anticipate your need will be, general carving out this and that or for decorative work. Check out Acer’s tutorial on carving here on ALR:
http://americanlongrifles.org/forum/index.php?topic=23123.0Lots of useful information in the Tutorial section, I go there often.
Regards Nicholson files, yes, quality is down unfortunately – I have found a few in small hardware stores that have Made in the USA stamped on them – I snapped them right up and they are great files. Do not purchase any files at the local Mega Home repair places, you know the two main ones… Their Chinese made files are out and out junk. Anticipating my build I purchased several, including a 4-in-1 rasp, my old one had gotten dull after years of use. This new one lasted about a half day of working oak, I noticed it becoming harder to remove wood, and the file skating on the wood (thought I was just getting tired). Upon examining the file I found it practically worn out. You are most defiantly going to need some good files but will, as I have, buy them made in Germany or Switzerland. I have some of those on order. You will need a good 10 inch mill file for barrel work and some small ones for working on the lock and other steel parts, keep the good files for steel. If you have them use old files for brass work. Here is a good link to file and stones for steel:
http://americanlongrifles.org/forum/index.php?topic=2585.0Our man Acer knows his stuff – as do many here far more than I, like I said I am working on my first rifle.
Good luck on your build and you have chosen one of the best kits available, Jim Chambers and his crew are top notch as are the products he sells.