Jonathon Gillham 4606 Posted September 14, 2020 I am sorting out the battery mount for my FF04. Continued lockdown buys me more time but also means shipping times are terrible so I would rather buy local bits and make it. I need a threaded tube about 2cm long to fit M3 bolts. I can tap a thread, but what size tube do I need? And wall thickness? I assume to end up with M3 I need about 2.5mm internal diameter, and probably 1.5mm wall thickness? Any one know for sure? Share this post Link to post Share on other sites
Lee76 638 Posted September 14, 2020 Tap drill size is correct at 2.5, what material is the tube and do you know the type/class of bolt/stud you’re using. Aluminium 2618 T6 you’d be ok with around 1.5 wall, the OD of the internal thread is 3.172 which would give you 6.172mm OD, call that 6mm.. head of the std M3 is 5.5mm so it’ll look about right. section of your tube is around 20.3mm2 2618 al yield is 370Mpa, so you can take a compressive load of ~7.5kN which off top of my head is about the clamp load you’d have from a decent grade steel m4 fastener, so you’d be ok with any M3.. working back the calc, the fastener head size 5.5 would allow for 5.87kN load same materials applied, which might be adequate for cheap cheesey screws not over torqued... happy to delve deeper if you have more details. 1 Share this post Link to post Share on other sites
Lee76 638 Posted September 14, 2020 Ps... if you’re making steel tube be aware the properties for the different steels range from <300 - >2500MPa yield.. so super thin walls to thicker than the aluminium.. 1 Share this post Link to post Share on other sites
KEV THE REV 2319 Posted September 14, 2020 6mm B&Q alu rod will do fine . Or find a Frog / Brat etc. hex spacer and cut it down / use that 1 Share this post Link to post Share on other sites
Jonathon Gillham 4606 Posted September 15, 2020 Thanks for the responses, I will try and track down 6mm aluminium tube and see if it works. It will be cheap so not the end of the world if it doesn't Share this post Link to post Share on other sites
Jonathon Gillham 4606 Posted September 15, 2020 Just searching where is closest to buy and they stock aluminium, brass and copper tube. Which will be best? Or will it not really matter? Share this post Link to post Share on other sites
KEV THE REV 2319 Posted September 15, 2020 10 minutes ago, Jonathon Gillham said: Just searching where is closest to buy and they stock aluminium, brass and copper tube. Which will be best? Or will it not really matter? I use B&Q raw 6mm alu rod . I've made threaded rod with it before . They stock it and it's cheap . Share this post Link to post Share on other sites
KEV THE REV 2319 Posted September 15, 2020 14 minutes ago, Jonathon Gillham said: Just searching where is closest to buy and they stock aluminium, brass and copper tube. Which will be best? Or will it not really matter? I use B&Q raw 6mm alu rod . I've made threaded rod with it before . They stock it and it's cheap . 1 Share this post Link to post Share on other sites
Re-Bugged 10146 Posted September 15, 2020 2 minutes ago, KEV THE REV said: I use B&Q raw 6mm alu rod . I've made threaded rod with it before . They stock it and it's cheap . B&Q = Bunnings on this side of the world 😉 1 Share this post Link to post Share on other sites
Jonathon Gillham 4606 Posted September 15, 2020 32 minutes ago, Re-Bugged said: B&Q = Bunnings on this side of the world 😉 I stopped in Bunnings and they had nothing suitable, but Mitre10 (Kiwi version of Bunnings, often next door to Bunnings) has a big range, and it looks like they now stock a decent range of model stuff. That's ideal, scratch built projects can get hidden in the household budget much easier! 1 1 Share this post Link to post Share on other sites
