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Bushes, dowels and circlips.


RichardS

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In my previous article I mentioned that the next job was to align and join the ‘stage boards.’ What I didn’t mention was a particular feature that one of these must have.

1b98d-img_20200114_1426151.jpg?w=1024The board that needs to be removable is the one in front of the door on the left.

Portable layouts normally use some form of alignment which can be part of the joining mechanism or can be stand alone. Almost without exception these stick out and this means that some ‘wriggle room’ is needed to disengage a board from its neighbour. However, a large and heavy permanent layout is not amenable to wriggling. Thus I required a means of being able to align a board as well as allow it to be removed without moving it’s neighbours. The method I used is not, I am sure, novel or unique and I lay no claim to its invention but it seems to work.

I anticipate that Bosmelin will remain ‘up’ most of the time and only taken down during the winter for dry storage or hopefully on occasions when it might be required for an exhibition. And as it fills most of the ‘Railway Parlour’ – blocking the door in the process – easy access is definitely required as few of my circle are lissom youths any longer! Furthermore Dawn requires access to the garage.

Essentially, I have fitted removable dowels at each end of one board. I had some brass tube and round bar which by a stroke of luck were a sliding fit. The problem was I didn’t have much of either. The tube was o/d of 5/8″ (a tad under 16mm) and the i/d was 1/2″ (about 12.5). As I was attending the London Model Engineer’s Exhibition I assumed that I would be able to easily obtain some matching brass tube and bar even if it was metric now. Not so. All the stands that were selling such material had none that were a sliding fit and it seems that the gauge of the tube was less. In discussion with stallholders it seems that my tube and bar were left over from a special job. (Or as I suspect they are quite old and in those days material was more generous!)

Much humming and harring followed about the best way to overcome the shortage of material. To cut the story short my solution was to cut the bar into short lengths and to use this as a ‘bush’ fitted into the wooden board ends. The 1/2″ bar is pretty sturdy so there’s little risk of any misalignment due to bending. The chief risk is that I lose one of the four dowels I made from the bar for reasons which will be obvious. So next I need to concoct a means of attaching the dowels to the boards permanently. I think a length of cord attached to an anchor will suffice.

ee00c-img_20200126_1234331.jpg?w=1024Dowels and bushes during manufacture. Won’t win any prizes but are functional and hidden in the ends of the boards.

Drilling holes in round things can be tricky and in my collection of acquired tools I have a vee block with a ‘U’ clamp. I used this to cut the bar for the dowels and will also use it to drill a hole into the bar for the cord to pass through.

00bba-img_20200126_1230581.jpg?w=1024An excellent way to hold round things when you need to cut, drill, mill or anything really.

For drilling accurate holes a drill press is an enormous help although a high quality one with assured accuracy will be expensive. Most hobbyists therefore tend to look at the more economical machines most of which are made in China. I expect that the quality of today’s offerings is higher than older machines. Mine is an older model which I’ve had for some time. The main area of concern is spindle wobble and it was a bit hit and miss if, and how bad, these earlier machines might be in this respect. I was lucky and mine was always quite good. I was however, never very happy with the supplied chuck and had in mind a replacement for some time.

A new 13mm chuck was therefore one of my purchases at the MEEx. The taper on the machine is a B16 and RDG tools sell a range of suitable replacement chucks which seem much better than the original. They are noticeably chunkier and consequently heavier.

When I removed the old chuck the spindle also came out of the drill. The spindle is the part driven by the motor and is held vertical in the head by the quill which usually has two fixed bearings top and bottom. The quill is the bit which moves up and down and is held in place by the handle and a spring. The spindle is held in the bearings by a single external circlip. It’s anything but complicated.

When the spindle came out the circlip had obviously failed. This necessitated taking the whole contraption to apart to access the circlip which was bent. At least it was an opportunity to clean the sliding surfaces and re-grease and oil the moving parts.

I thought I had some circlips but despite searching high and low I could not find any. I did find my tin of M8 bolts which I needed so the effort was not entirely wasted. Resigned to buying some I retired to browse the Screwfix website. Circlips……. right…….a Thousand! I don’t want a thousand. £13.00 as well. I only want one and maybe a spare. I found the range sold a small blister pack of various unspecified sizes for £1.49. It was worth a punt – but nothing inside was the right size. Eventually I found a handy pack (64 clips) at Toolstation for £2.71 advertised as ranging from 6mm to 25mm but no mention of the intermediate values. Fortunately, there was one in the pack that fitted and the remainder are now on the shelf where I expect they’ll gather dust for ever.

So now I was ready to drill the holes for my alignment bushes. I had tried to find a 5/8th drill at the MEEEx with no success the nearest I found was 41/64ths – a fraction too big but as I planned to glue the bush into the wood a tolerance would be useful. But, 41/64 was too big for my new chuck. I had toyed with the 16mm option but it was a good deal heavier than the 13mm and decided it was too beefy for my drill. I returned to Toolstation and bought a 16mm ‘Blacksmith’s’ drill with a reduced shaft that would fit the 13mm chuck. Away we go!

Not so fast Gunga Din! The board end that I was drilling was so big it could not be fixed to the table so needed to be held this meant that the big drill tended to vibrate the wood. This was not going anywhere. So it came about that I drilled the hole with a 16mm flat bit held in a Black & Decker hammer drill. The depth drilled was at the most 68mm and I was concerned that it wouldn’t be straight.

aa189-img_20200127_1424161.jpg?w=768

As it happened I got away with it. The bushes were glued in with Gorilla glue and while this set the dowels were inserted to ensure alignment and the boards held together with 2 off M8 bolts held by T nuts (one in each board -a threaded and a clear drilled.) These also help alignment and can be used alone but accurate dowels are er.. well… more accurate.

52f31-img_20200127_1424261.jpg?w=768The finished fitting. Sliding brass dowel for alignment and M8 Bolt in T Nuts for joining.

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