What taps and dies do I need?

A full set of 26TPI Cycle thread taps and dies, 1/4" to 3/8", some Whitworth taps, 1/4" to 3/8" and that should do you to be getting on. Anything else is rarely used, if ever. Gordon.

Gordon's quite right about the fairly limited range that will be used most of all but if you can't obtain them easily then it might be worth having a slightly wider range rather than having to wait for weeks while an extra one arrives through the post.

I assume that you're thinking of repairing damage rather than fabricating a full range of components ?

The official descriptions have changed slightly over the years but BSW is simply British Standard Whitworth. This is the coarse thread generally found in alloy castings so it's rare to have to clean up the male threads. As Gordon says, the smaller taps should see you through most jobs such as cleaning up castings.

Norton rarely used BSF (British Standard Fine)

CEI is Cycle Thread (sometimes shown as BSC). It is the most comon thread on Nortons of this period and is mostly (but not always) 26 tpi. However, Norton were quite fond of the non-standard forms. I would be inclined to purchase a set running from 1/4" to 5/8" . However, if the threads are the same as the earlier generation and you also want to tidy up larger threads such as crankcase bolts and wheel spindles then you're also likely to need 3/8x20, 7/16"x20 and 9/16"x20 cycle taps and dies. If you have a thread guage then it's worth measuring the larger threads before you order.

You may also need BA (British Association) This is generally found on electrical and instrument fasteners but also on some makes of handlebar controls. Generally the 'even' numbers are most common but you may find 1BA and 3BA on some controls. Just the taps should do as the screws generally need replacing if they're damaged.

Unfortunately, you're probably unlikely to find a standard boxed sets of taps and dies 'suitable for 1948 Norton' and whatever you buy, you're still going to get caught out needing an oddity.

Great advice from Gordon - re sizes to look out for.

The only other thing to be aware of is any replacement or aftermarket parts.

If these are UK (or European) sourced, threads could be Metric

Some US parts could be UNC or UNF.

I have been collecting used taps and dies from eBay - they come up all the time (usually when engineers retire). These are well worth the investment, as they are likely to be High Speed Steel so will last you forever. The cheaper, new Carbon Steel taps and dies are fine for cleaning up threads, but my preference would be the much better quality HSS which second hand are around the same price.

Hope this helps, and enjoy the 48 ES2!

I get all of my tap& Die sets from The Tap & Die Co (www.tapdie.com) in London. Just about every thread form and size is available, in HSS, and also 'HQS'. A useful motorcycle boxed set they do is from 1/4" to 5/8"CEI. They dispatch the same day, worldwide.

The Tap & Die Co are certainly a very good supplier, and I bought my BSW BSF and BA sets from them. Since Bryon is in Canada, he might want to try Mike at Walridge Motors in Ontario, I bought a very nice set of CEI taps and dies from him, and shipping would cost less than from London.