Gina's Observatory Build - Abbreviated - Finishing Touches and Improvements

[Gina]

Boring out now completed as per the sketch but with the sharp corners chamfered a little.  I may just lap the bearing surface a bit to get the bearing in.

[Gina]

While I'm waiting to sort out the narrow parting off tool which I want to cut the notch in the V groove as well as parting off, I've been cutting the V groove on the second wheel.

[Tinker1947]

Thinking back a bit...well its quite a way back, i seem to remember people used spent hacksaw blades as parting off tools with the end ground to the right shape.....???

[Gina]

Thinking back a bit...well its quite a way back, i seem to remember people used spent hacksaw blades as parting off tools with the end ground to the right shape.....???

Yes, I've heard of that   Would need to make up something to hold it, of course.

[Tinker1947]

I think 2 pieces of steel with 6 allen screws 3 along the top, 3 along the bottom with the blade in the middle would do the job then held in the tool post with some shims for the right height....i will have a search around the boxes in my workshop if i had one it won't have been thrown away, just got a bit deeper under other bits and bobs.....

[Gina]

We had some storm damage last night but the obsy roof stayed on alright.  The horizontal rain as from a power spray found a small gap just under the roof where it got blown upwards and into the scope room - no damage done, just a puddle on the floor.  It missed all the kit except for the car battery that supplies the winch but wet won't hurt that.

The sun lounge was not so fortunate   One roof panel blown off and 3 wall panels.  A full length end wall panel (facing roughly west) has completely disappeared - well, put it this way... I haven't found it yet.  I haven't explored the whole property for damage yet.

Fortunately the storm has gone and the weather is fine and dry with some sunshine today.  Many roads still flooded though.

[Tinker1947]

Good luck with your search is this a valid insurance claim....

[Gina]

I think 2 pieces of steel with 6 allen screws 3 along the top, 3 along the bottom with the blade in the middle would do the job then held in the tool post with some shims for the right height....i will have a search around the boxes in my workshop if i had one it won't have been thrown away, just got a bit deeper under other bits and bobs.....

Thank you   Might have a piece of broken hacksaw around around here - I'll have a look.  Yes, that method of fixing it should be fine

[Gina]

Good luck with your search is this a valid insurance claim....

Thank you   I've found all the itinerent panels now and, if I have time before it rains again, I'll put them back this afternoon.

[Lonestar70]

Hi Gina,

Sorry to hear of your storm damage and hope you did not loose anything from within the sun lounge, either blown away or water damaged.

It has been pretty bad up here for the last 2 days with several areas flooded, trees down and power lost.

I see you have been doing some more with the turning but are facing problems with parting etc.

A hacksaw blade will work for small depth cuts, if you can find a safe way to hold it, but cannot be used for deep parting, since it's side profile will be wrong and it would also flex badly at longish extension from the toolpost.

Long term I would suggest one of these: -

http://www.ebay.co.uk/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.XLathe+HSS+parting+tool&_nkw=Lathe+HSS+parting+tool&_sacat=0&_from=R40

And the 1/6" x 1/2" blade for it shown directly below it.

The only sharpening, when required, would be to the front edge... the side rake is built into the blade.

To align the blade at exactly 90deg to the work... run the carriage up so that the tool is up against the front flat face of the chuck... adjust the toolpost to get the blade side flat against the chuck... simple.

Adjust for tool height as normal.

This is the type I use on the Myford and can easily part of 3" dia stuff with it.

Hope you get everything back together and weather tight.

Stay safe.

Best regards.

Sandy

[Gina]

Hi Gina,

Sorry to hear of your storm damage and hope you did not loose anything from within the sun lounge, either blown away or water damaged.

It has been pretty bad up here for the last 2 days with several areas flooded, trees down and power lost.

I see you have been doing some more with the turning but are facing problems with parting etc.

A hacksaw blade will work for small depth cuts, if you can find a safe way to hold it, but cannot be used for deep parting, since it's side profile will be wrong and it would also flex badly at longish extension from the toolpost.

Long term I would suggest one of these: -

http://www.ebay.co.uk/sch/i.html?_trksid=p2050601.m570.l1313.TR0.TRC0.XLathe+HSS+parting+tool&_nkw=Lathe+HSS+parting+tool&_sacat=0&_from=R40

And the 1/6" x 1/2" blade for it shown directly below it.

The only sharpening, when required, would be to the front edge... the side rake is built into the blade.

To align the blade at exactly 90deg to the work... run the carriage up so that the tool is up against the front flat face of the chuck... adjust the toolpost to get the blade side flat against the chuck... simple.

Adjust for tool height as normal.

This is the type I use on the Myford and can easily part of 3" dia stuff with it.

Hope you get everything back together and weather tight.

Stay safe.

Best regards.

Sandy

Thanks Sandy   Though not particularly cheap, that looks like a good idea.  There are several things I have planned that will want a deep parting off so worth going for I think

I found all the polycarbonate sheets for the sun lounge and have replaced them - though the roof panel is only placed in position and not fastened down.  "Rain stopped play."  Hoping to secure it tomorrow morning.  I don't think anything serious has suffered damage

[Gina]

I've ordered those bits - should be here between Christmas and the New Year.

[Lonestar70]

Hi Gina,

Pleased to hear that you have not lost anything important and that you have all the panels now replaced.

there are more strong winds forecast over the next few days so forget turning and get your panels secured... perhaps a few 6" nails here and there

I suppose the parting tool does look a bit expensive when compared to a couple of pieces of tool steel, however, it has many advantages... the blade is deeper, making it stronger in the main load direction; meaning it can extend further from the toolpost when necessary,... it has built in side rake (both sides) so sharpening only requires a few thou of the front face... the blade can be pulled in or out to achieve the necessary extension (normally you would keep this to the minimum required for smaller parts... you can increase the blade width easily just by swapping to a thicker one (I think your comes with a 3/32" and the spare is 1/16")... the blades last for years and are relatively cheap when replacement does become necessary.

I have had mine for 15years or more and have only had to replace the blade 4 times... and I do a lot of turning making steam engines and boilers.

Try doing all that with a couple of  pieces of 5/16" square tool steel.

 Did I tell you lathes can be just as damaging to your wallet as astrophotography    

Have a great Christmas Gina and a very happy New year.

Best Regards.

Sandy.

[Gina]

Thank you Sandy   You have a great Christmas and New Year too - main celebration will be Hogmanay for you I expect   Have a good one

Yes, I expect to spend a bit on tools etc. for the lathe but so far it's looking a lot less costly than astro

Been looking a bit more at acetal/Delrin.  In large diameters it generally works out dearer than aluminium but cheaper for 60mm or smaller.  I've been wondering if it would have been suitable for the obsy roof wheels

[Lonestar70]

Hi Gina,

Acetel/Delrin would be ideal for your obsy roof wheels, it has very good wear characteristics (especially in wet conditions) does not corrode like ali and is very easy to machine providing you use very sharp cutters and keep the speed low (otherwise it can overheat at the tool contact point and melt onto the cutter... resulting in a very rough finish).

The trickiest part when turning it is keeping control of the swarf, which comes of in a long single strand and goes everywhere... often it tangles round the chuck...

Delrin is actually used nowadays for a lot of smaller boat propshaft bearings (especially the underwater end).

It does absorb a very small amount of moisture (around 0.3%) from the atmosphere but this does not create any appreciable dimension change... unlike Nylon which can swell up as much as 5% overnight.

As for tooling costs... well, just as with astro, you get what you pay for; and cheap tooling is a complete waste of money. This is particularily so when it comes to drill bits... cheap ones are soft, often out of round and also can be of doubtfull dimensions.

A good set of 1/16" to 1/2" in 1/64th" increments (or the metric equivalent) can set you back £50 - £70... but will last a lifetime... cheap ones aften break or bend on the first use. 

The same goes for taps and dies.

Good tooling can cost more than 2 times the cost of the lathe.

Keep happy.

Sandy.

[Tinker1947]

A set of morse taper drills with the same size fitting your tail-stock, bench drill, and milling machine would be nice, not sure if the chinese have started producing these yet, very nearly all my tools are 10 to 50 years years old mostly made in the UK.....

[Gina]

Hi Gina,

Acetel/Delrin would be ideal for your obsy roof wheels, it has very good wear characteristics (especially in wet conditions) does not corrode like ali and is very easy to machine providing you use very sharp cutters and keep the speed low (otherwise it can overheat at the tool contact point and melt onto the cutter... resulting in a very rough finish).

The trickiest part when turning it is keeping control of the swarf, which comes of in a long single strand and goes everywhere... often it tangles round the chuck...

Delrin is actually used nowadays for a lot of smaller boat propshaft bearings (especially the underwater end).

It does absorb a very small amount of moisture (around 0.3%) from the atmosphere but this does not create any appreciable dimension change... unlike Nylon which can swell up as much as 5% overnight.

As for tooling costs... well, just as with astro, you get what you pay for; and cheap tooling is a complete waste of money. This is particularily so when it comes to drill bits... cheap ones are soft, often out of round and also can be of doubtfull dimensions.

A good set of 1/16" to 1/2" in 1/64th" increments (or the metric equivalent) can set you back £50 - £70... but will last a lifetime... cheap ones aften break or bend on the first use. 

The same goes for taps and dies.

Good tooling can cost more than 2 times the cost of the lathe.

Keep happy.

Sandy.

Yes, I've read that acetal is used for bearings, having low friction and good wearing properties.  Maybe I could use acetal wheels directly on SS bolts without ball bearings.   Must say I like the idea of running acetal wheels on the ali angle (upside down "V").  The wheel V angle could be 90 degrees and there should be no problem with contact at different radii causing rubbing friction.   If I use plain bearings maybe I could get away with 60mm OD wheels.  I have ordered some 60mm white acetal stock for making pulleys etc.  Going from 60mm up to 80mm increases the price by 50%.  OTOH "I don't want to spoil the ship for a ha'porth of tar".

As for tooling costs, I quite agree.  I tried buying cheap drills and ended up with ones that looked like they were meant for going round corners   Since then I have stuck to the well known good makes.

[Gina]

A set of morse taper drills with the same size fitting your tail-stock, bench drill, and milling machine would be nice, not sure if the chinese have started producing these yet, very nearly all my tools are 10 to 50 years years old mostly made in the UK.....

I was wondering about getting morse taper drills to use directly in the tailstock rather than balacksmiths drills and chuck.   I was also doubtful about buying that cheapo set on ebay.

[Tinker1947]

Its a shame the old tool shops have gone to the wall, nothing nicer than looking along shelves of engineering kit and just buy bits on impulse....as for the cheapo on ebay, are there alternatives if there are  just buy a few at time if they are good quality....

[Lonestar70]

Hi Gina,

Providing that you use good quality stainless BOLTS with repeatable PLAIN shank diameters that are truly ROUND; then running directly on these with Delrin would be fine, with perhaps a smear of waterproof grease... failing that then stick with ball races.

I would think that 60mm (minus a light skim to true up the moulded OD) dia would be perfectly acceptable... you would, of course, need to adjust the mounting height of the wheel carriers (approx 10mm) to account for the smaller diameter.

Morse taper drills, to suit your tailstock size, would be a much better idea than Blacksmiths drills... they are a good bit more expensive though, but perhaps 9/16", 5/8", 11/16" and 3/4" sizes would be a suitable set to start with.

Below 1/2" dia then a good set of 'Dormer,  'Chesterman' or 'Starret' HSS drills would be the way to go in conjunction with a good 'Jacobs' 1/2" tailstock chuck (one with a chuck key... I hate those keyless ones).  

You could go mad and buy a set of Cobalt steel drills... Fab... but around £150.00 for a 1/16" - 1/2" set.     

If It were my Obsy... I would go the Delrin route, even if it meant buying 80mm OD.

Keep happy.

Best regards.

Sandy.

[Gina]

Thanks Sandy - that's good   I think I'll save the 3" x 100mm billet of aluminium for something else such as astro adapters and make my roof wheels of acetal.  The current setup is 100mm rubber tyred wheels with needle roller bearings running on 12mm SS bolts with plain shanks.  The needle rollers actually run on the SS axle.  Hence I shall be remounting the wheels anyway.

Putting some dimensions on the new wheels, the V grooves are 12mm deep so the OD dimension is reduced by 24mm diameter plus another 2mm for the groove at the bottom of the V.  ie. 26mm.  With the ali wheels I started with 3" = 76.2mm and turned down (to skim up) to approx 75mm giving a diameter at the bottom of the V of 49mm.  The ball bearings I chose are 12mm ID x 37mm OD x 12mm wall so there is a thickness of (49 - 37) / 2 = 6mm.  If I were to use 80mm OD acetal with the same bearings I would get a bit under 8mm thickness of material between bottom of groove and bearing outer.  Not sure I'd be happy with this with acetal - would it be strong enough? I wonder.

OTOH if I were to use plain bearings with the 12mm SS bolts I already have and the 60mm acetal I have on order, the diameter would probably start at 58mm after skimming up.  Minus 13mm x 2 = 32mm.  The bearing diameter would be from 34mm (1.33") to 58mm.  There would be a 10mm thickness at the very bottom of the V groove.  I think these wheels would be a bit too small with the current design of V groove depth.

Now with 80mm acetal everything would be 20mm larger diameter than the 60mm.  Bearing diameter on the angle would be 54mm minimum (just over 2").  On the 12mm axles there would be 20mm thickness of material between V groove bottom and axle.

Of course, I don't have to use the 12mm SS bolts - I could get some smaller ones.  I only got 12mm because that's what the rubber tyred wheels wanted.

I think I shall order some 80mm diameter acetal in black then I can always use it for astro adapters where the additional strength of aluminium is not needed.  Cost of 100mm is £17.47 + £5 delivery = £22.47.  Cost of 250mm is £28.07 + £5 = £33.07.  I can easily get 250mm between chuck and centre in tailstock so for an additional tenner I think I'll go for the 250mm length.  That will set me up in round acetal for a few years to come I think

[Gina]

Tailstock is MT2 and I think I'll just buy drills as and when I want them, one at a time, good quality ones

[Tinker1947]

Tailstock is MT2 and I think I'll just buy drills as and when I want them, one at a time, good quality ones

That's a plan.....

[Lonestar70]

Hi Gina,

Given the dimensions you have posted, I agree that the 80mm Acetal is the better option.

An 8mm clearance between the ball race and the Vee groove would probably be adequate... it's tough stuff Acetel.

If you feel that a smaller bearing would be beneficial; is it possible to remove the needle bearings from the old rubber wheels and insert them into the Acetel ones.

Alternatively, if you want to retain the rubber wheels... Arc Euro sell small needle roller bearings of a suitable size: -

http://www.arceurotrade.co.uk/Catalogue/Bearings/Needle-Roller-Bearings

Part Number HK1212... ID = 12mm, OD = 18mm and width = 12mm... should be perfect.

Buying larger Morse taper drills as you need them is probably the best idea... it spreads the cost.

I would invest in a good HSS set of 1mm - 13mm x 0.1mm steps though... these will get a fair bit of use on astro items... especially the 6mm and under... the 0.1mm steps will cater for metric taping drill sizes... which would be =  OD - pitch.... e.g. M5 x 0.8 = 4.2mm tap drill.

Also 3, 4, 5 and 6mm taps and dies... again very common sizes for astro bits.

The list keeps growing does it not!!!

All the best.

Sandy.

[Gina]

Thanks Sandy   I have ordered the 80mm OD x 250mm lump of black acetal.  I think I'll try plain bearings with the wheels.  As I recall, I checked the SS bolts for imperfections and for size and roundness with a micrometer and they were fine   I can make hubs the full width of the gap between timbers less the thickness of SS washers between wheel and wood.  That would save making spacers.  Might just finish off the two ali wheels in the lathe at present... or would it be best to start afresh with the acetal?  The ali wheels have been good turning practice anyway

I have a set of taps and dies with holders which I got from Axminster Tools a while back but I don't have the exact size drills for tapping so a set os finely spaced HSS drills would be a good idea

Cheers