Looking to find some 4" diameter wood .... something reasonably hard, but does not have to be oak ... a dense softwood would do. But very open grain softwood no good.
Will be used as a roller, so has to be pretty good in round section.
Only need around 12" of it .... anybody any idea where I can get some (don't have a lathe)
If your hand tools skills are good, you can use the boatbuilders method of making masts and spars - google "spar gauge" and look at several explanations until you get the idea.
This will give you some of the idea:
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design shows pencils, rather than scoring/marking with pins - as I was taught)
It's a fairly accurate technique for marking out a square section piece of timber, so that you then plane off the corners - to make an octagonal section.
You repeat the process to make a sixteen-sided section, and after that
- you can probably identify the high points by eye, and reduce it to a circular section by sanding with a long belt of sand paper, drawn back and forth around your mast/spar/roller.
(NB, the ratios on the spar gauge are slightly different between 8 sides and sixteen. Some texts say don't worry about it - the difference is too small. Others texts seem unaware of the difference. Often though, you can judge marking out the sixteen sides by eye, and don't use the gauge again)
Irrelevant aside to what the OP wants to make:
The joy of using a spar gauge is that it is no more difficult to make a tapered circular cross-section, as it is to make one of a constant diameter - the gauge simply marks out the correct ratio - provided the square section timber has had the correct taper cut on it (if it's solid timber - usually done with a bandsaw), or built up (if it's been glulam'd together out of smaller timbers).
How about the legs for children's swings. Usually made from pressure treated redwood - may be dense enough for your needs. I know you can get them in 4" dia.
Plenty of ways to do this. Much depends on the weight, the point loading, the wear life and the weatherproofing.
Plastic pipe, filled. Hard, smooth, weatherproof. Easy to embed a steel axle.
Fencepost. Usually larch, which wears quite well but isn't quite as hard as some timbers. Will be quite smooth, but may be slightly oval (shrinkage on drying after rounding) and may have a spiral pattern that causes loads to shift on a long roller.
Recycled wooden rollers. Salvage yard and look for old mangles. My stash of lignum vitae is old freight handling rollers from dockyard warehouses.
Turned wood. Make a lathe. The easiest sort is a rectangular plywood "gutter" with end plates to carry centres (screwed spikes) and a router on an extension baseplate slides over the top. Manually rotate the roller and pass the router up and down. A variant uses an angle grinder with an arbortech cutting disk (I use this a lot for rough turning). A deluxe version uses a woodturning lathe (unpowered, or just at creep speed) as the centres and rests the router on a similar plywood guide. If you make your roller of two halves, it's again easy to embed an axle.
Constructed masts and barrels of multiple staves. Almost certainly too much trouble, and the weight advantages are minimal at this size.
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