- 3 May 2019
- Reaction score
If precision needed you just drill a cluster of holes and choose the best one. A cordless hand drill will do fine, 1mm twist bit etc. You don't have to adjust both holes - just the pin hole so 0.5mm adjustment needs 0.5mm.... Trammel (two holes in a piece of wood):is fine as long as you don't need to fine tune the size of circle. If you do need to fine tune it it can become a real headache and you discover that your drill technique isn't as good as you thought it was (speaking for myself here): to get 0.5mm tolerance in diameter you need 0.25mm accuracy in hole spacing. Pillar drill helps. If you need to tune size more finely than that you're going to end up cutting quite a few and it will take time. .
I use a trammel tool for drawing large radius circles. Just Google it to se a large variety of types including pensil holders.Unable to find one (some?) online.
I'm looking for a pair of compasses, up to say 16" radius, big version of the old brass school compasses?
Anyone know where I can find them please (UK ideally)
If this is a one-off, I found Just4funs suggestion is quick cheap and practical. Its 15 minutes or less to make a trammel of that size. If you need to change the diameter a lot, then probably best to buy a quality trammel. Compass's get unwieldy at that size, although both quit hard to keep the point in place for both trammel and compass at longer diams. If just a few uses, its quicker and cheaper to make it. Home made work very well.<grin/> Don't be so darned practical ;-)
Yebbut what if you want to adjust it by, say, 0.1mm?If this is a one-off, I found Just4funs suggestion is quick cheap and practical. Its 15 minutes or less to make a trammel of that size. If you need to change the diameter a lot, then probably best to buy a quality trammel. Compass's get unwieldy at that size, although both quit hard to keep the point in place for both trammel and compass at longer diams. If just a few uses, its quicker and cheaper to make it. Home made work very well.
Another benefit of Trammels vs compass is its easyer to make an ellipses as well as circles, you just use the major and minor axis, whereas many more measurments with a compass. Here is one I was using recently, its a foot long, its actuallly a bit easyer to make longer ones accurately.
A tips on making, drill pilot hole for the nail, and from the bottom up (so that the exact radius is on the bottom, important to keep the hole perpendicular, or drill more than one hole!!. See phot the many nails is I ended up doing more and more diameter measurements, just lower the one needed and tap the others back, should really buy a proper one... The two end holes for pencil when doing an ellipse. Good luckView attachment 104685
I agree - if you may be able to see in the photo I put up earlier, that there is is more than one nail width wise to get very small changes in diameter down to about 1mm. If you need realy fine, they buy an expensive metal one. Its so simple I suggest you give it a go and if it doesnt suit you then you can spend money. I only use the tammel one in a while so find making it work well. Much better an string, as the pencil wobble about on string. My son made one 8 foot long to mark up a scooter ramp and that worked fine.Easier than that - you drill a cluster of holes near the pin hole until you get one as accurate as you want. They don't have to be in line.