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Finding some means of fixing polished stainless steel shafts rigidly to the declination axis housing [and also the saddle] has proved difficult. Initial euphoria at finding affordable, conical locking bushes at RS was short lived. The price doubled in the time it took to look around the website's list of different bushes!
So I looked elsewhere using various terms for "bushes" and then found an alternative in very attractive, stainless steel, necked flanges. Which sell at about the same price as locking bushes but are of much larger diameter. Sadly I never found any QD split bushes outside of the US.
These neck flanges have a smooth machined bore. In standard 1½" water pipe [DN40?] fittings there is a 150mm [6"] diameter flange listed with a 48.3mm bore in a raised neck. The advantage is that it offers enough depth for a rigid joint. The downside is that it needs a tiny smidgen bored out to bring it out to the full 50mm diameter to fit the shaft. However, the top is flat and easily large enough for our purpose without needing extra load spreading plates necessary for the much smaller bushes.
Alternatively, and perhaps easier: the axes shafts could be turned down very slightly to fit the original [and presumably, highly accurate] flange hole. Just putting the flange in a lathe may throw off the accuracy of the nicely finished bore. The resulting, slight shoulder in the shaft might have location advantages for the Polar axis. Though the declination axis might be far too long to fit in many lathes and will not likely benefit from a shoulder when it is pointing downwards. I am not a fan of thinner, declination shaft extensions. The counterweight mass is applied at distance and may find a natural resonance of mass x length x compliance.
Alternatively, and perhaps easier: the axes shafts could be turned down very slightly to fit the original [and presumably, highly accurate] flange hole. Just putting the flange in a lathe may throw off the accuracy of the nicely finished bore. The resulting, slight shoulder in the shaft might have location advantages for the Polar axis. Though the declination axis might be far too long to fit in many lathes and will not likely benefit from a shoulder when it is pointing downwards. I am not a fan of thinner, declination shaft extensions. The counterweight mass is applied at distance and may find a natural resonance of mass x length x compliance.
Moreover, these pretty flanges have enough length in the "neck" to allow [grub?] security screws to ensure it stays safely in place on a pre-dimpled shaft. Which just means the newly drilled holes in the flange neck are spotted through with a marker pen. Or even the drilling continued into the shaft long enough to make a dimple. Or, the shaft can be removed from the flange and the markings drilled just deep enough to securely locate a grub screw's 'pointy' nose on reassembly. You'll have to remove the shaft from the flange to thread the security screw holes anyway. Always use a weighted rubber or plastic hammer to avoid marring the nice stainless steel finish of these components if one is needed.
Always keep firmly in mind that an unintended/accidental separation of a flange from a shaft might be a hideously expensive and potentially fatal affair! Particularly in the sizes and considerable weights we are discussing here. Imagine dropping a priceless historical achromat or large APO from ten feet up! Absolute security of the shafts in their flanges must be assured 150% or better. Having a shaft drop out of a mounting while it is carrying a huge telescope on this scale is very likely to kill you! Even if it only injures you, but you break an irreplaceable instrument, you may feel like finishing the job off yourself! [Though this is obviously not a serious suggestion.]
Always keep firmly in mind that an unintended/accidental separation of a flange from a shaft might be a hideously expensive and potentially fatal affair! Particularly in the sizes and considerable weights we are discussing here. Imagine dropping a priceless historical achromat or large APO from ten feet up! Absolute security of the shafts in their flanges must be assured 150% or better. Having a shaft drop out of a mounting while it is carrying a huge telescope on this scale is very likely to kill you! Even if it only injures you, but you break an irreplaceable instrument, you may feel like finishing the job off yourself! [Though this is obviously not a serious suggestion.]
Over time, bare stainless steel contact surfaces tend to "freeze" together if they are a nice tight fit. Though this should never be relied on for a fixing. Alternative fixing methods might be industrial adhesives like Loctite. Not some cheapo, water soluble "superglue" from the supermarket! Loctite industrial adhesive would need heat to separate the flange from the shaft if it proved necessary at a later date. It may also need special cleaners and/or primers to achieve their claimed adhesion levels. Check the instructions very carefully and make sure you are using the correct adhesive. There are many Loctites! All flange or bush security screws should be lubricated from the first tightening. Then checked at regular intervals for corrosion and tightness. Opposed screws, or three spaced at 120° intervals are far safer than trying to get away with only one.
Stainless steel is tough to drill unless the drills are brand new. The material easily work hardens with blunt drills. Cutting threads also takes quite some care to avoid breaking the fragile tap. Those without the necessary skill or tools could ask a local engineering firm to do the job properly for you. A through, split [roll] pin might be employed if you can find one long enough and the fit of the shaft in the flange is good enough. You must never rely on a pin [nor screws] in a floppy fitting shaft/flange as the pin or screws will soon wear or even break! Disaster awaits the negligent or "it'll be-alright" type!
I briefly considered screwed flanges and threading the end of the shafts but there are serious pitfalls. Threading the shafts requires that they be very tightly gripped. On water pipe this means nasty toothed jaws gripping down hard on the softer steel/iron pipe to resist the massive torque applied by the threading die. Then there is the very difficult problem of threading tough stainless steel with a cutting die meant for much softer stuff. This job really ought to be done with a properly shaped, thread cutting tool in a large and equally tough lathe. The flange will probably need to be faced off afterwards on the flat side to undo any inaccuracy in the thread cutting process and final assembly. Don't forget a locking screw or pin in case the whole thing unscrews over time!
Black and galvanized flanges are also available as is plain steel shafting. If you don't want to get involved in stainless steel then follow the black "iron" route. Lower cost and much more easily worked and threaded [or welded?] if you want to try that. Just remember to keep the inevitable rust at bay or the mounting may never come apart again! This is no joke [at all] when you can't change the counterweights to balance a new telescope.
Update: I went ahead and ordered pair of stainless steel, weld-on, neck flanges in the 48.3mm bore size 150mm [6"] OD. Those who want to copy me will need quite a large a lathe. Or know somebody who has, to skim the bore to match the 50mm shaft size. Or turn your shafts to match the flange bore if necessary or even possible.
Anybody with easy access to QD split bushes can ignore my choice and still have a bolt together, heavy-duty mounting. You just have to match the bore of the QD bushes to your shaft size and slip them on, tighten to the supplied instructions and you should be in business. The flange sizes of QD bushes are likely to be much smaller than those I am using. Those locking bushes I found were 92mm outside diameter but cost 25% more than the neck flanges.
N.B. I can only suggest how I might overcome the various build problems myself. I can accept NO responsibility whatsoever for unsupervised work carried out by an unskilled, untrained, drunk, drugged, tired, senile and/or slapdash person on the other side of the world. Nothing I say here should ever be considered as a license to cause real or potential injury, or loss, to yourself or others. Copying any of my suggestions here will NOT make me liable for your unknown inadequacies. I have a lifetime of experience in many constructional and metal working fields. You may not even realise the obvious dangers which an experienced worker would spot from a mile off. For example: I can use a motor mower and power tools/machines without losing any fingers or toes. [So far.] It seems that many others can not. Enough said?
I briefly considered screwed flanges and threading the end of the shafts but there are serious pitfalls. Threading the shafts requires that they be very tightly gripped. On water pipe this means nasty toothed jaws gripping down hard on the softer steel/iron pipe to resist the massive torque applied by the threading die. Then there is the very difficult problem of threading tough stainless steel with a cutting die meant for much softer stuff. This job really ought to be done with a properly shaped, thread cutting tool in a large and equally tough lathe. The flange will probably need to be faced off afterwards on the flat side to undo any inaccuracy in the thread cutting process and final assembly. Don't forget a locking screw or pin in case the whole thing unscrews over time!
Black and galvanized flanges are also available as is plain steel shafting. If you don't want to get involved in stainless steel then follow the black "iron" route. Lower cost and much more easily worked and threaded [or welded?] if you want to try that. Just remember to keep the inevitable rust at bay or the mounting may never come apart again! This is no joke [at all] when you can't change the counterweights to balance a new telescope.
Update: I went ahead and ordered pair of stainless steel, weld-on, neck flanges in the 48.3mm bore size 150mm [6"] OD. Those who want to copy me will need quite a large a lathe. Or know somebody who has, to skim the bore to match the 50mm shaft size. Or turn your shafts to match the flange bore if necessary or even possible.
Anybody with easy access to QD split bushes can ignore my choice and still have a bolt together, heavy-duty mounting. You just have to match the bore of the QD bushes to your shaft size and slip them on, tighten to the supplied instructions and you should be in business. The flange sizes of QD bushes are likely to be much smaller than those I am using. Those locking bushes I found were 92mm outside diameter but cost 25% more than the neck flanges.
N.B. I can only suggest how I might overcome the various build problems myself. I can accept NO responsibility whatsoever for unsupervised work carried out by an unskilled, untrained, drunk, drugged, tired, senile and/or slapdash person on the other side of the world. Nothing I say here should ever be considered as a license to cause real or potential injury, or loss, to yourself or others. Copying any of my suggestions here will NOT make me liable for your unknown inadequacies. I have a lifetime of experience in many constructional and metal working fields. You may not even realise the obvious dangers which an experienced worker would spot from a mile off. For example: I can use a motor mower and power tools/machines without losing any fingers or toes. [So far.] It seems that many others can not. Enough said?
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