Must have material stock?

Hey folks...

Just beginning my journey into model kits, starting with stationary engines and moving up to traction engines.

I'm hearing a lot about kits coming with near or under size stock provided and wondering if there are any common sizes that get this ' that'll do' treatment? Or if there are any common items that perhaps often come with less than ideal grade material?

Essentially I'm asking, as the title suggests, what folk find are 'must have' items to keep in the stockpile?

Thanks, Jay.

I've not heard much of stock material coming near or undersize, that is more the case with some castings.

Of the two suppliers who offer materials (Stuarts and Hemmingway) they are cut sufficiently long for you to be able to make the part though sometimes it can be easier if you have a longer length to hold but not essential.

Some stock such a bright mild steel rounds may be a fraction under nominal size but that would be the same if you bought it or the kit suppler provided it as it is just made that way

Rather than buy in stuff you may never use it would be better to get your chosen kit and drawings and then spend a few hours going through the drawings and making a note of what you need this also allows you to think about how you might make each part and what may be required to hold it and that will depend on what equipment you have.

Also decide if you really want to buy that 300mm length of 5mm square stock to make a part 8mm long when you could mill down the end of some 8mm round to 5mm square and use the rest of that 8mm round for other parts.

J

Edited By JasonB on 18/09/2022 19:47:29

Most cold drawn/cold rolled sections are slightly undersize. They all have tolerances, and by being at the bottom end of the tolerance the manufacturer can save considerable amounts of material.

I don't buy kits, but in terms of stock any bright steel under about an 1" in diameter is bouight in a standard ~3m length. Above that I buy what I need. For hot rolled steel I buy the standard ~6m length. For brass/bronze I buy shorter lengths as needed.

For sizes I use a lot I keep several lengths in stock. For instance I keep stock of steel in 3/16", 1/4", 5/16" and 3/8" diameters plus 8, 10, 11 and 16mm AF hexagon as I am making most of the nuts, bolts and studs for my model engines.

I find it useful to buy more than needed as it allows one to mess up without having to buy more stock with the associated wait. Over time one buiids a stock of material which can often be used rather than buying new.

Andrew

Being new to metal bashing I buy as needed I am slowly getting a small stock of odd ends which if large enough I stamp the grade of steel onto so that I remember what it is.

I find that most places can deliver quite quickly and while waiting I find another job to do. And as Jason I inspect the drawings and order what is needed, this is a habit I have got into when I am woodworking.

When I first set up my home workshop, I purchased what I thought would be a good supply of stock material. I still have some of it after 10 years. I don't buy material in kit form and purchase it as needed for the project. I normally buy extra because I know that it is a size that I use.

As stated, all supplies are made to a tolerance and not to an exact size. Hot rolled, to a wide tolerance and precision ground to a tighter tolerance. (tolerance specifications found on-line). If I need material that is on the maximum supplied size,  I ask if I can check the thickness before they cut a piece for me.

Edited By Paul Lousick on 18/09/2022 23:56:32

I was thinking that having some nominal sizes of brass an FM steel hex bar would be a good shout as you've then got all the potential profiles you could want.

Now it's mentioned though, I realise that most of the instances I've seen this be a thing, on YouTube or what have you, it has been the bright steel bar that's been suspect... In those cases I suspect it's probably best to just suck up the replacement if necessary and save the offending article in the hope of another use? But then if its just the bottom end of the tolerance and offering a good consistency across the length, I guess it's a relative non issue if the machined parts can be adjusted accordingly. I'd just rather not have to compound adjustments across a whole model, if at all avoidable.

I definitely don't want to fall into that trap of buying stuff and have it hanging round for 10+yes, that sounds a bit soul crushing!

As I said earlier you may not get a better replacement as it is simply made a thou or two undersize BUT a lot will depend on what part you are making. If it's simply a column on a steam engine then it's unlikely to be critical but if it's a crankshaft then that needs to be a better fit in a typical spec reamed hole or the hole bored to suit the smaller size.

If you do decide to but some materials to keep in stock then think about whether you want to work in metric or imperial, most older designs of kit will be imperial, some dual dimensions and the more recent ones in metric which will affect what you buy.

I tend to make less from kits than I do starting from scratch and also prefer to work in metric so things like steel in the smaller diameters upto 12mm dia I by in 3m lengths (3 x1m for postage) as it works out a lot cheaper than they typical 300mm or 1ft lengths that most ME suppliers sell after that it may be 1m lengths then 500 or 300 as the diameter goes up. I do like to keep a stock of steel, brass, bronze and aluminium but over 40yrs I have got to know what I use and my uses are not just kit making.

Of the brass and hex you say you may keep as stock items I would be more inclined to keep some 230M07 (EN1A) in say 6, 10, 12, 16 and 20mm diameters and aluminium in 6, 12 and 25 not so much to use as actual parts but if you need to knock up an arbor or some filing buttons then they can be used for that. Imperials would be 1/4, 3/8, 1/2, 5/8. 3/4 and 1" short lengths would do to start with. If you are going to the Midlands show then Nogginend tend to sell bundles at a bit of a discount which may be worth looking at.

Good tip thanks Jason

I have in the past bought bags of bar ends, various sizes, usually steel mostly with their identifying painted ends. Still have quite a stock of round, rectangular, also odd bits of stainless. This does entail finding a steel stockist who saws into billets for customers and also visiting often as possible and getting to know the people so you can find out when they are available.

The only problem I have found is that each supplier has their own colour coding. I found this out when I asked what grade a off cut of ali was by the red colour code on the end piece. So unless you know the supplier and what colours they use it is a mine field

Edited By Derek Lane on 19/09/2022 08:52:00

My supplier said much the same as Derek's. I asked what the colour code on my end meant, and he said "it shows where we got it from". Presumably the retailer sprays stock to identify the wholesaler in case there's a problem with it. It's a colour code Jim, but not as we know it...

To answer Uncouth's question, to save time I laid in a stock of common sizes in Brass, Steel and Aluminium that roughly suit the sort of work I do, but don't rely on it to do everything.  I order whatever extra is needed to do a specific project, generally buying somewhat more than needed to beef up my junk box. 

Laying in a lot of stock without knowing what it's for is expensive.  Some of the "common sizes" I bought at the start have barely been touched after 8 years - waste of money.  Now I think it's better to build stock by experience.

Buying scrap is risky unless you know what it is.   My entry to the hobby was almost derailed because I'd collected various bits of old metal on the assumption it would be 'good enough'.   Silly me, how naive!  Turned out my entire collection of scrap was vile - squishy Aluminium, hardened steels, and various alloys difficult to cut or get a good finish on.  Although with patience and skill most things can be machined, I prefer to buy metal known to have good machining properties.

Dave

Edited By SillyOldDuffer on 19/09/2022 10:41:59

If you are a member of a club they often have available bits of metal in little auctions of a sales table at meetings though some will moan that it is of unknown origin, type, quality etc. You could get a few bits in standard sizes like 1/4,3/8,1/2 or metric equivalents as they are bound to be used one day. If you are concerned about precise size then get the next 1/16 up and you will soon have some undersized bits as you practice turning them down to precision bar.

I don't get hung about stock tolerances. Out of interest I've just measured some offcuts of 3/16", 1/4", 5/16" and 3/8" steel rod, all are between 1 and 2 thou undersize. That is perfectly acceptable for most applications with a reamed hole. Bearings need a gap for the oil film to work properly.

Tolerances are only of concern to me for precision stock, mainly silver steel and gauge plate. A couple of pieces of silver steel measured 0.03mm undersize.

If I really need accurate and straight then I grind my own, but a pretty rare occurrence:

Andrew

So a bit of a 'storm in a teacup' situation then... Well that's something of a relief.

I'm nowhere near ready to start buying anything in significant enough lengths as to make a difference to price, so I'll just stick a pin in that idea for now and wait n see what I find I'm using a lot of...

Cheers all.

Jay