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

[Tinker1947]

I have sets of taps and dies Whitworth fine and course, Metric, and BA each tap and die has its own drawer in the same drawer are a clearance and taping drill, does save a lot of drill bits if you were to buy sets of drills, i have normal sets 1/2 mill increases (1mm to 15mm) HSS,Titanium and Cobalt (up to 10mm) and just buy others as required....This does cost a few pennies but when done over a number of years it not so bad....

[sloz1664]

Hi Gina,

For you to cover all your tooling needs (including morse taper drills and/or reamers)

would cost a fair amount of cash. The best place you can pickup a lot of

good quality tooling, albeit ol, is the good old car boots.

There are some fantastic bargains to be had. Just remember to take a

shopping list and your digital caliper to measure your drill / reamer diameters.

cheers

Steve

[Gina]

I have sets of HSS drills 1mm to 10mm in 0.5 steps.  I need to get 10.5mm to 13mm in 0.5mm steps and tapping size drills for M3, M4, M5, M6, M8 and M10.   I'll look at pricing but I'll probably get the tapping drills indivually.

Car boot sales are a good idea - thanks Steve

[Gina]

I have the outside of two aluminium wheels virtually finished plus the inside of one.  Can't do the inside of the second until I've parted off the first, of course.

 

The acetal wheel will be a different design.

[Gina]

This looks like a decent set of drills up to 13mm

[Tinker1947]

They look like there could drill a nice hole, not seen this type before they will fun to sharpen....

[Gina]

I've used this type before - they're brilliant for hand drilling - pilot drill built in   And they don't wander off course or drill funny shaped holes in thin metal like ordinary drills.  A centre punch is all that's required before drilling and the hole is spot on.  For lathe use the centre part will act as as centre drill.  They are also useful for drilling semi-blind holes so that Allen headed bolts/screws can have the head below the surface - as in dovetail bars.

I haven't tried sharpening them though    Sharpening ordinary drills is bad enough!

[Tinker1947]

I've used this type before - they're brilliant for hand drilling - pilot drill built in   And they don't wander off course or drill funny shaped holes in thin metal like ordinary drills.  A centre punch is all that's required before drilling and the hole is spot on.  For lathe use the centre part will act as as centre drill.  They are also useful for drilling semi-blind holes so that Allen headed bolts/screws can have the head below the surface - as in dovetail bars.

I haven't tried sharpening them though    Sharpening ordinary drills is bad enough!

Practice sharpening on old drill bits some metals like Brass require the drill to be backed off a bit other wise they grab the metal, your local boot fair will have loads of bits that need a bit of love...

[Gina]

We have a number of old drill bits lying around.  Now I have a nice new bench grinder I shall have to collect them up and sharpen them.  Most will be imperial but they're still useful.  And, as you say, good for practice

My first piece of acetal rod came today - 45mm OD x 90mm approx in white.  It's lower in surface friction than I thought and I'm looking forward to seeing how well it machines.  I'm beginning to think of just taking the ali out of the chuck and going all out for the acetal roof wheels.  With the latest design they will be much easier to make - no complicated step bore with accurate mounting for a ball bearing.  Just a plain 12mm hole through the middle and turned hub (plus the V groove).

[Lonestar70]

Hi Gina,

That set of drills from DeWalt are not a good purchase for lathe work, they are better suited to sheet metal working (hence the double ground points)... and you would need a cutter/grinder to sharpen them properly... no way you will be able to do it by hand.

A better, and much cheaper set for your work would be these: -

http://www.tracytools.com/hss-drill-sets/drill-set-10-13mm

I can vouch for their quality as I have 2 of the same set from these people, one of which I have backed off for brass use... I also have the 1 -10mm x 0.1step set.

Tracy tools are a long established engineering tools supplier and offer excellent tools at very competitive prices.

I buy the majority of my toolsteel, drills, taps and dies etc from them and have never had a bad one in 20 years.

Keep happy.

Sandy.

[Gina]

Took the 4 jaw chuck off complete with the aluminium workpiece and put the 3 jaw chuck on instead and clamped the 45mm OD white acetal in that.  Needed the outside jaws as the piece was too big for the inside jaws.  I found it very difficult to hold the work firmly enough in the chuck but by tightening up hard and then tapping the workpiece on the RH end I was able to get it pretty much straight and running true.  The exposed face had been cut far from square and facing off had to be done very carefully.  This material machines like a hot knife in butter - lovely   I cut a skim down part of the length using the power feed and it went beautifully.  Then having tidied up the end I cut a boss and then a pulley groove.  Yes, the swarf is rather a nuisance and tends to get in the way of seeing what you're doing but it's soft and delicate compared with aluminium swarf.  I didn't use any cutting lube - cut it dry - seems to work fine

[Gina]

More experiments with turning acetal today also with grinding my own lathe tools.  Found two main things with acetal - the low friction makes it very difficult to hold in a chuck so after replacing it and aligning it as well as I could I trimmed off the end again and cut a dimple in the end with a pointed tool to take a centre-bit.  So now its held in chuck and centre in tailstock - that's that fixed   Secondly, the pointed tools I've been using for aluminium are not ideal for acetal - they produce very fine swarf which gets everywhere and particularly all around the cutting tool.  A wide tool works much better   So I've been making my own custom shaped tools on the grinder with the fine wheel.

I started with a rounded end (semi-circular) for cutting round grooves for rope pulleys.  Worked a treat   Nice clean round bottom groove just right for 6mm rope.  It also works well for straight cutting - I trimmed up the cylindrical surface with it.  Nice clean result without the usual fine grooves.  Acetal machines beautifully with a wide tool, producing wide swarf that's much more manageable than the fine stuff you get with a pointed tool.   I then went on to produce a special tool for the notch at the bottom of the V groove for the roof wheels.  This has two 45 degree sides and a narrow round ended projection in the middle.  Sounds difficult to do on a bench grinder but was much easier than I expected.  Just needed careful handling and patience.

This photo shows two round bottom grooves and one special shaped for the roof wheels.

[Gina]

Here's a close-up of the tool end and groove.

[Tinker1947]

Do you have a white grinding wheel they take the heat away from the tool, and should leave a nice clean grind......

http://www.axminster.co.uk/aluminium-oxide-white-grinding-wheels

[Gina]

Do you have a white grinding wheel they take the heat away from the tool, and should leave a nice clean grind......

http://www.axminster.co.uk/aluminium-oxide-white-grinding-wheels

Slight problem... wrong size bore for my grinder - it's 12.7mm.  There's some on ebay though.

[Tinker1947]

Slight problem... wrong size bore for my grinder - it's 12.7mm.  There's some on ebay though.

I linked the white wheel more for the description than the size, try for a fine grit and be very gentle...

[Gina]

Right.  Axminster quote 60, 80 and 100 grit but the others just quote "Medium".  I could turn an adapter to fix the bore.

[Gina]

I have worked out most of the Modus Operandi for making my roof wheels   This is for acetal wheels with plain bearings.

  1. Turn the RH side to make a hub using the home made round ended tool

        

  2. Use home made special tool to cut a notch to the full required depth in one go.  

     

  3. Set the crosshead to 45 degrees

  4. Using the knife tools cut the full V groove

     

What I still have to wok out is making the centre hole and parting off if the work is held between chuck and centre.

[Gina]

The roof wheel cutting example on the test piece.

[Gina]

The roof wheel cutting example on the test piece.

[Gina]

Another piece of acetal came in the post today - not the 80mm yet but the 60mm OD x 250mm in white.  I'm not expecting the 80mm OD piece until well after Christmas.  So I'm just wondering whether to try making the wheels for the much lighter north side from 60mm stock running on 8mm SS rod axles rather than 12mm.

[Tinker1947]

Will making the wheels different sizes alter the way the roof fits like the overlap ect....

[Gina]

Will making the wheels different sizes alter the way the roof fits like the overlap ect....

No, it's just a matter of drilling holes for the axles in the wooden framework in the right places.

[Gina]

The 80mm OD x 250mm black acetal arrived by courier this afternoon so I'm hoping to be wheel making soon.

I measured the spacing of the ROR support frame timbers today in a break in the rain (in fact we had some sunshine) and it's about 45mm - more than I thought.  In view of this I think I shall stick with the 12mm bolts as axles.  I had considered 8mm but worried about the bending moment at least for the heavy south side.  I could turn wheels with a width of 45mm less the thickness of a couple of SS washers but that would use a lot of acetal.  I think I'll use 25mm width at the hub with spacers made from separate material.  I think 25mm would be quite adequate for stability as a plain bearing on the 12mm SS bolt shank.  Then I shall want a little under 10mm spacers each side.  My original plan (with the ball bearings) was to use ali tube as spacers but I'm not keen on ali next to SS so I'll make them from acetal.  I'll probably find another use for the 3/4" x 10g ali tube

[Gina]

I've just checked that the 80mm acetal will fit in the 4 jaw chuck - it will - easily   Since the wheels will be spaced away form the woodwork there is no need for a hub - the wheels might as well be just cylinders with a V groove around the outside and a 12mm hole through the middle - even simpler to produce.  So next job will be to attach the 4 jaw chuck and mount the bar between that and the tailstock centre then chop off sections of the acetal 25mm wide.  I can do this with the parting off blade held in the parting tool clamp taking the tool to within about 5 or 6mm of the center.  Next take the work out and saw the sections off.  The blanks can then be drilled with a 12mm hole by just holding them in the chuck.  These blanks are now ready to be mounted on a 12mm mandrel and have the V groove cut into the outer edge.