When you say ‘first project’, how much machining background do you already have? An IC engine is not an easy thing to build correctly and a thorough understanding of the characteristics of materials to be used is essential.

Experienced engineers will already have a general idea of best practice, and will simply research areas they are not familiar with. There isn’t really a one-size-fits all answer to your question, although I’m sure other members of the forum will advise where they can, but I’m surprised that whatever plan you’re working from doesn’t give specifics.

Standards for materials define many, many critera, such as workability, machining finish, stress tolerance, wear characteristics etc etc . For non critical parts, many guys simply use whatever they have already lying around.

1050 is pretty much pure (and hence soft). 5251 and 6082 are both high strength alloys (which is what you usually want). Do pay attention to the temper as this determine the actual properties of the alloy. Here are a bit more info:

https://www.azom.com/article.aspx?ArticleID=2805
https://www.azom.com/article.aspx?ArticleID=2813

The TLDR is 6000-series T6, it’s the most common structural alloy with good all-round performance.

The Webster is a common first IC project particularly in the US and you can be a bit flexible with some of the materials, others should be adhered to.

6082-T6 would be my choice for the frame and 95% of other aluminium parts found in most model engines. You may find some of the ME suppliers list this as HE30

For Brass I would go with CZ121 which is not too soft and machines nicely.

Anything on the drawing that calls for Drill Rod will be Silver Steel in the UK.

CRS is Cold Rolled Steel which is  a bright mild steel such as 230M07 (EN1A) and for the built up crank I would suggest using PGMS which is precision ground mild steel

Bearing bronze would be SAE660 or in smaller sizes Colphos is reasonable to machine

The 12L14 for the cylinder is a leaded steel 230M07pb or EN1Apb but my choice would be to go for iron GR17

M-Machine would be my choice of supplier.

Jason has given specific recommendations,  but a more general way of doing it is to search the web and check what the material’s specification says about machinability.

For example, Aalco say: ‘In the T6 and T651 temper, alloy 6082 machines well’.

Phrases in the spec like “free-cutting” are good, but avoid anything that mentions ‘work hardening’, or any other hint of poor machinability, unless there’s a special reason for using it.  (Copper doesn’t machine particularly well, except it’s other properties outweigh that when making Boilers.)

Alloys of the same metal vary wildly, so it pays to check.  Of the US 1000 to 7000 Aluminiums, only alloys in the 6000 series have specifically good machinability, and though many of the others do machine, bit tricky, some are vile; I believe the entire 1000-series are all too soft to machine well.

Dave

On 3 April 2024 at 12:00 JasonB Said:

2011 T3 and 2014 (old HE15) can be very nice to machine, not just the 6000series

The problem with suggesting Google is that if the drawing just says “Aluminum Alloy” and as a beginner you don’t know what you actually want property wise it is hard to know if what you find is what you need. You will also end up with a load of info on American spec material that is not going to be much use if buying in the UK or ROW when you want an “AluminIum Alloy”

This is where I come unstuck with the different grade numbers across the globe, is there a list of comparisons from one side of the planet to the other

Straying a wee bit off topic but that’s a good heads up on 6061 T6. It is silly expensive in the UK and the only reason to use it is the availability of thin wall tube and sheet that you can’t get in UK spec 6082 T6.