2" shaft mounting Pt.25: 60-50mnm wormwheel sleeve adapters.

Since the wormwheels had been supplied with 60mm bores, instead of the 50mm I ordered, I had to make some brass adapter sleeves. This was very time consuming since so much material had to be removed from the only stump of brass bar I had left in a suitable size. This required a diameter and length which would provide two 45mm long adapters plus enough material for parting off and something to hold firmly in the 4-jaw chuck. Though I had a number of options to ensure concentricity I chose to bore and finish turn both sleeves without ever removing the brass bar from the chuck. 

I found a stump of yellow brass 65mm diameter and made a start on making the packing sleeves. First I center drilled the stump and took a cleaning cut. Then fitted a center and 'clocked' the piece in the 4 jaw chuck. The chuck jaws were tightened securely to avoid losing concentricity. Then I ran a 10mm drill in the tailstock chuck deep enough to give clearance for the nose of a boring bar.

In the picture above I have reached 45 mm bore and will continue deepening and widening the bore until I can part off two sleeves for the wormwheels. In fact I worked on the bore of only one adapter at a time due to the depth matching my medium length boring bar. That concludes tonight's effort.

Next day I finished boring and turning the first adapter sleeve. By sheer luck I was able to use the smaller wormwheel as a gauge to sneak up on the correct diameter. In between I had used a vernier caliper to reach the correct diameters. I also had my original, short stump of SS shaft which could be used to fine adjust the bore size.

Finally I parted off the first sleeve and started boring the second. This went much more rapidly because I could now trust my measuring tools to rough out to get close to finished size. Once that was finish turned to size I could part it off with the lathe in the slowest back gear. You would not believe how much swarf was left in the lathe's tray!

Now came the marking for the three radial holes in each sleeve for the adjustable clutch pads. These consisted of short lengths of ~8mm diameter nylon rod. Each of these is pressed against the axis shaft by a stainless steel grub screw to allow fine adjustment of friction/slippage so that the telescope can be pointed anywhere in the sky without having to retract the worms.

Instead of marking the radial holes with a marker pen I chose to tighten the grub screws straight onto the brass sleeves. This left clear imprints from the hollow nose of the screws which could then be carefully center punched. After using a small drill to ensure an accurate starting point I used a series of larger drills to open out each hole. Then all it remained to do was open out each hole with a tapered broach to aid entry for the nylon plugs. The alternative would have been to open out all the holes to 9mm which was slightly too large.

I have deliberately made the brass sleeves slightly too long so that there is a linear thrust bearing surface if needed. Should I later decide to make them flush with the wormwheels the sleeves are easily removable by backing out the grub screws. Meanwhile the nylon clutch plugs locate the sleeves securely in the wormwheels so that they do not rotate independently of the wormwheels. It is obviously desirable that the only bearing surfaces are formed by the close fitting brass sleeve and nylon plugs on the axis shaft. There is no slop either internally or externally on the brass sleeves to cause any eccentricity. Which would obviously badly affect the tracking.

I have been notified by the parcel service that my Baader SC filter can be picked up. Do other countries have such a sophisticated parcels/package services? When you buy something online you give your email address and telephone number to the vendor. These are then used to automatically contact you by SMS or email when the items is waiting at a local package/parcel outlet or post office. Far more reliable and user friendly than waiting in all day for the post person and then not get the package. Or they didn't bother to ring the doorbell and took it back to the sorting office. Almost every village has a collection center so they are usually within easy reach and particular outlet options are suggested depending on one's home address and can be specified when ordering. A further option is to have the item delivered directly to one's place of work.

Click on any image for an enlargement.


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