Gina's Mini Widefield Imaging Observatory

[Tinker1947]

If you were nearer i would sort out the curved edges, in the absence of a router a jig saw will do the job, then sand round the edge, glue the roof  to the edge so there's no end grain showing....

[Gina]

I have a jigsaw but I'm not very adept with it.  I think a router would do a much better job.  It would come in handy for other things too

[Tinker1947]

1/2" collet and variable speed, i doubt you going to use it to often so don't go to deep into the wallet, i will take a photo of a simple jig i made to cut circle........

[Gina]

Thank you   Not sure I would need to go as big as 1/2"...

This is a rough sketch of how I'm thinking of cutting the end pieces out of a 1200mm square piece of marine ply (could probably move the parts around to make better use of the plywood).  Still not quite decided on 9mm or 12mm but tending towards 12mm.

[Gina]

Well... I don't know...  Looks like a router is going to be more difficult than I thought.  I don't think a jigsaw is the answer as not only would that need as much guiding but rips up plywood as well and I haven't got a belt sander so cleaning up would be difficult.

I'm wondering whether to go back to my original plan of a ROR apex wooden roof with rubber covering, though that isn't without its problems - which may be why I haven't done anything on it for ages

Later...  Had a good think about it and although I have a lot of the parts done for an apex roof, there will still be a lot to do to finish it and to automate it would be as difficult as my main observatory.  Then again I like the idea of the "clam shell" roof and I think adding a motor drive would be relatively simple.

On a personal note, I've been outside a bit and although it's sunny it isn't warm, with a rather cold breeze.  I went out to my observatory thinking I might set up ready for tonight but I'm just not feeling up to it.  I'm still suffering from this virus I've had since before Christmas

[Tinker1947]

Cutting those shapes out with a Router would require MDF templates and a guide bush, and some place with a decent flat surface to work on, a Jigsaw while it will tend to tear the ply this would only be on the top side the up cut of the jigsaw would leave a neat cut underneath, the other option is a bandsaw with a fine blade your still get some tearing underneath, this in all cases could be hidden by making the tear side a inside edge and add beading to the join to hide the tearing and give it more strength, as for setting up tonight, i have been digging holes and putting up 6" x 6" posts for a pergolas, plus the Moon will be up around 18:30 so will give it a miss.....

[Davey-T]

And dust extraction .

Dave

[Tinker1947]

And dust extraction .

Dave

Do it outside with a couple of fan to blow the dust away...me i have dust extraction, its not cheap doing it right...

[Gina]

Well I won't be imaging tonight - I'm staying in the warm   The local forecast has turned cloudy again anyway

[Gina]

Rearranged the pieces to cut out of the plywood.

[Gina]

And dust extraction .

Dave

I have a dust catcher that works with a domestic vacuum cleaner.  It's rather like the Triton DCA300 Dust Collection Bucket 20 Litre but metal rather than plastic.  Bought it from Aldi some time back.

[Gina]

1/2" collet and variable speed, i doubt you going to use it to often so don't go to deep into the wallet, i will take a photo of a simple jig i made to cut circle........

Cutting those shapes out with a Router would require MDF templates and a guide bush, and some place with a decent flat surface to work on, a Jigsaw while it will tend to tear the ply this would only be on the top side the up cut of the jigsaw would leave a neat cut underneath, the other option is a bandsaw with a fine blade your still get some tearing underneath, this in all cases could be hidden by making the tear side a inside edge and add beading to the join to hide the tearing and give it more strength, as for setting up tonight, i have been digging holes and putting up 6" x 6" posts for a pergolas, plus the Moon will be up around 18:30 so will give it a miss.....

I'm interested in that jig you mentioned in the first quote above - that should cover the arcs of circle and a straight piece of wood should do for the straight parts.  Some straight parts will be covered by the edges of the square I'm starting with.  I would imagine a piece of wood from the router to the centre with a bolt to act as axle should do arcs

[Davey-T]

That's good, you don't want to get dust down your throat when you're already feeling rough.

The most important thing about routing is good jigs which you generally have to make by hand so try to make one jig does all and don't forget to allow for the guide.

Why is it I keep seeing the thread title as Gina's Minefield, hope it's not an omen 

Dave

[Gina]

Ah - I can see how you could read it as that   I decided a dust collector was needed when I was using my large mitre saw   I imagine a router is going to produce a lot of fine dust.

Good point about allowing for the guide   I shall probably practice on some scrap plywood or OSB left over from my observatory build.  I realise that any guides need to be pretty solid.  I am always particularly careful when using power tools - I've heard of some quite horrific injuries   I think the most dangerous power tool I've used is a chain saw - vicious things    Yes, I still have all my extremities perfectly intact   And I always protect eyes and ears too!

[Tinker1947]

Guide bushes for routers fit on the base plate, the cutter goes through the middle, 6mm MDF is cut to the shape you want then clamped to the material to be shaped, taking into account the width of the cutter and the guide bush this make the jig slightly smaller than the radius of the required shape a good example is this slot cutter picture....

http://www.axminster.co.uk/axminster-slot-cutting-jig

[Gina]

I have ordered the  Bosch POF 1400 ACE 1400 Watt Router

[Tinker1947]

I have spent around 2k on router bits with these people, this goes back 30 years, never had a bad one........there are some good help files on the site......i would have still looked at a  1/2" but the that Bosch Model would be top of the list for a 1/4"

http://www.wealdentool.com/

[Syed Saif Alam]

Mind blown !!!!

[Gina]

I have spent around 2k on router bits with these people, this goes back 30 years, never had a bad one........there are some good help files on the site......i would have still looked at a  1/2" but the that Bosch Model would be top of the list for a 1/4"

http://www.wealdentool.com/

Yes, very helpful - thank you

[Horwig]

Gina, a bit left field, what about giving the pattern cutting to one of the local water jet people? You can then cut the real wooden pieces by router, my local firm were a lifeline for me with my telescope build, all I had to supply were tiffs to scale.

BTW, the router I bought to build my dome was a cheap Titan 1/4 inch one from Argos, with a profile cutter from screwfix:

http://www.screwfix.com/p/trend-guided-profiler-router-cutter-shank-12-7-x-25-4mm/1613f

The water jet people might even cut the real pieces for you

Huw

[Gina]

Interesting idea but I prefer to do things myself

[Gina]

The Bosch router is here :)  It looks great   A manageable weight with nice comfortable handles and good balance.  A nice collection of accessories are included too.  The combined fence for straight lines and trammel bar with attachable point for cutting circles is a great bonus, particularly as it will easily go out to 310mm radius   I think that might be just enough - I still need to check the measurements though.  I'm thinking I will probably go for 300mm, 305mm and 310mm for the radii giving 4mm clearance with 1mm thickness of aluminium for my mini observatory roof.  Just wondering if I can achieve this level of accuracy

[Tinker1947]

As they say, "Measure twice cut once" practice on scrap first, the straight edge cutter works but its so easy to wander away from the edge, getting a second fence means you can put slots in a wooden to with in thou's of a inch provided the wood is square and been through a thicknesser (PAR from wood yards will have been....

Hole cutting or cutting your radius curve is easy, just take your time and only go in 1/4" at a time or you cutter will end up in 2 pieces...

[Gina]

I've taken the plunge (as they say ) and ordered the marine ply in 12mm thickness and a sheet of aluminium 750mm x 500mm x 1mm thick.  Just the one sheet ATM to see how the thickness works out, I'm not familiar with handling this size of ali sheet.  It needs to bend easily but not be too floppy.  The thickness I've chosen is pure intuition

[Gina]

The aluminium sheet has arrived   It's stiffer than I expected and will take a bit of bending to a 300mm radius in the short direction.  Going to look for thinner sheet...

A bit later 750mm x 500mm x 0.5mm found