I need to trim 15mm off the ends of my truss poles so I can achieve focus with a paracorr.
Does all the same advice apply here for cutting aluminium tubing? Hacksaws and the like are out of the question as I need square and clean edges and absolute repeatability on the cuts.
To do this it's a good idea to "borrow" a proper pipe cutter. You can buy a reasonable quality one for under $50, but thats a lot of money to cut 8 pieces of pipe. If you know a plumber he will have one or alternatively you could go to a metal fabricator who might charge you $10 or so to do the 8 poles. No point doing a 1/2 pie job on a beautiful SDM scope.
I need to trim 15mm off the ends of my truss poles so I can achieve focus with a paracorr.
Does all the same advice apply here for cutting aluminium tubing? Hacksaws and the like are out of the question as I need square and clean edges and absolute repeatability on the cuts.
Or go and have a nice afternoon out in the contryside and get Peter to lop the ends off for you! (I'm pretty sure he uses a std pipe cutter)
MY FRIEND RICHARD AT HERES THE LINK http://www.baytop-observatory.com/
he has cut aluminium several times quite succesfully with a circular saw with a mitre blade.. do not use a ripping blade thats all
cheers skelty
the use of a carbide tipped blades is a no no for cutting aliminum. The correct saw to use is an aliminum blade; they look similar but are very different. Using the former can and does throw teeth and could cause serious injury. The item can also be ejected from the cutting bench and cause further injury. An ali blade will set you back a bit , but will be worth the money.
BTW I know this because my employees use ali blades for cutting Ali T Bar for exposed grid systems in office and commercial buildings (tiled ceilings). I am a ceiling fixer by trade and have seen ali cut with standard blades in the past and the disasterous results that can occur even in the hands of experts. Something which most of you are not. (No offence intended I just don't want to see anyone get hurt).
Don't risk the blade exploding and causing your death.
I personally don't agree with people recommending cutting aluminium with a circular saw in any way shape or form. As Paul points out the use of the wrong blade can be very dangerous. For trades people and skilled handymen who know what they are doing, it's fine. To tell someone who may not understand the different complexities of circular saw blades how to do it in an internet message is like sending a 10 yr old boy in to open against Brett Lee.
BTW Geoff a Hack saw is fine. To be a square line simply wrap a piece of paper all the way around the pole at the correct cut off point and then mark that with a fine tipped texter. Take the paper off and cut with the hacksaw. I typically use a 32 tooth blade for cutting ali by hand. Once cut then use a fine file to take the edges off. It will be clean and just what you want. Something like this you want to take you time with. Unless you are familiar with a drop saw I would not attempt it. You can cut it on the wrong side of the tooth and that will ruin that pole.
Sorry for off topic, but since you guy's are talking about gutting things and
sound alot more knowledgeable than me. I brought a angle grinder the other
day and it came with a few different blades and a steel brush.
So my Q is what would you cut with a diamond tip blade?
Thanks John and Paul for the warnings re carbide tipped blades, which incidentally I have seen recommended on tool vendor websites for cutting aluminium
I don't want to risk manual hand cutting with a hacksaw, as any variation in final lengths may throw out the alignment at the top end of the scope. 1mm error at the bottom would cause maybe 5mm displacement at the UTA. It looks like I'll have to track someone down with the correct machine tools.
Diamond blades will cut all masonary including concrete and brick. It will cut plastic also.
Why of course, you see the council cutting up the pathment with the o'l
diamond blade motor mower looking thing all the time. Doh! I guess I should
thought about that one a lil more. Although I dont think I'll attempt that with
my you beaut fathers day special $30 angle grinder from Mitre 10
A whole $30! I think I bought mine for $18.94 or similar. I suspect it's not designed for a full tradesperson's workload! But it's done a few small jobs for me successfully.
I don't want to risk manual hand cutting with a hacksaw, as any variation in final lengths may throw out the alignment at the top end of the scope. 1mm error at the bottom would cause maybe 5mm displacement at the UTA.
If it was me, I would cut it off with a hacksaw and the put the end into my mill and run a cutter over the ends to make them "identical". Don't you have a mill in your garage? Do you want to "borrow" mine? I spent most of the weekend in the garage working on my mill and lathe...
Trevor the ends of each pair of truss poles are screwed to a wooden device which clamps to the uta (see pics) and removing the fitting to work on the poles singly might screw things up (alignment).
The ideal arrangement would be some kind of drop saw with a depth stop so that each cut could be made identical and perfectly square. I need to take identical lengths off each pole and am nervy about the prospect of stuffing it up
I don't know how you could easily do that...if you decide the fitting needs to be removed then I can run a cutter over the ends to square them up for you. This would allow each one to be trimmed to a fraction of a mm with a nice machined end.
You could run a pipe cutter around the ends but I don't know if it could be set to cut exactly the same lengths, cutting to right depth and not damage the fitting inside I don't think would be a major problem. How would you get the cut off bit off the end?
Looking at the pic I'd say you have no alternative to removing the fittings. Any good machinist should be able the then trim the poles to within thousandth of an inch and redrill the screw holes in a like manner using a mill. Having said that, it looks like given how the truss is constructed, any tiny misalignment will be compensated for by adjusting the secondary mirror during collimation. Just the observations of a retired fitter
I suspect it's not designed for a full tradesperson's workload! But it's done a few small jobs for me successfully.
.
