As part of the staircase upgrade I need to mould a piece of handrail to give me a 90 degree corner piece. Moulding the outside radius is easy. One way is to rough cut the outline on the bandsaw, fit the stock to a pivot point (preferably adjustable so you can gradually make the cuts deeper) and slowly rotate the stock past the cutter.
Or you can make another one of these templates and cut to the right shape
which is what I did and an absolute doddle.
I added some shanks at either end to give me a straight piece for joining to the straight handrails and also let them splay out slightly so I could finish them to size once fitted.
But how to safely mould the internal curve :eusa-think:
One suggestion was to fix it to my spindle moulder fence which has a fine adjust and gradually pull the fence back thus pulling the stock gently into the cutter. But the opening in my fence isn't large enough.
So o.o.o take a piece of 18mm ply and fix it to the bed of the moulder. Cut an opening for the shaft.
Hog out most of the inside waste on the bandsaw yielding a rough 'U' shape.
Accurately mark the centre line to coincide with that of the shaft and centre the block over it.
Now those two 'legs' are a potential disaster waiting to happen such as being snapped off if the cutter strikes a high point. In hindsight I should have cut them off but even so that possibility of the remaining leg being snapped off is still there. Plus we need a way of controlling the stock into the cutter. So take a piece of 9mm plywood as a base.
Scribe to suit the U-shaped stock and cut away. Screw the stock to this reinforcing base.
Cut two pieces of wood exactly the same height as our stock plus a smidgeon (where 1 smidgeon = 2 gnats). Centre the block on the centre line, add a 1mm spacer at each side for wiggle room and fix those uprights to the main baseboard thus providing a channel into which our stock can be gently pushed. The reason for those spacers and their wiggle room is to allow me to sideways adjust the block relative to the cutter in case my centreline is not quite spot on. This then limits any unwanted sideways movement of the stock and prevents the cutter from getting too excited and hurling the stock into the corner of the workshop.
Fit the cutter head, flip the reinforcing board round and adjust the cutter to the correct height. Re-flip the board and slide in. Add a couple of top boards to stop the cutter throwing the stick in a vertical direction.
We now have a nice smooth tunnel into which we can gradually push our stock. But we're not there yet.
We've made a bit of a windtunnel and so to minimise stuff being sprayed into our face and to have a modicum of protection if it all hits the fan...add a top cover and handhold.
And we're good to go.
Gently and carefully I edged the stock in and gradually moulded the inside curve. Nothing untoward happened. Nothing exploded. I still have all my fingers. Kept switching off to withdraw the stock from the tunnel to check progress and make measurements. Finally getting down to the end goal but by this time the moulding of the endgrain was a bit extreme. So reckoned I could go 1mm more. So I clamped an end stop with a green 1mm spacer.
Removed the spacer and finished the last bit. And here we have it. Prudence being the better part of valour and I will finish off the remaining part by hand.
You can see that the moulded endgrain is getting a bit brutal
So well worth the effort to make that jig and if you recall I was concerned about making room for some sideways wiggle if I'd not quite giot the centre line and tunnel perfectly aligned ? Well, I measured the ends of the shanks and they are within 0.3mm of each other whivh I reckon is pretty good.
Or you can make another one of these templates and cut to the right shape
which is what I did and an absolute doddle.
I added some shanks at either end to give me a straight piece for joining to the straight handrails and also let them splay out slightly so I could finish them to size once fitted.
But how to safely mould the internal curve :eusa-think:
One suggestion was to fix it to my spindle moulder fence which has a fine adjust and gradually pull the fence back thus pulling the stock gently into the cutter. But the opening in my fence isn't large enough.
So o.o.o take a piece of 18mm ply and fix it to the bed of the moulder. Cut an opening for the shaft.
Hog out most of the inside waste on the bandsaw yielding a rough 'U' shape.
Accurately mark the centre line to coincide with that of the shaft and centre the block over it.
Now those two 'legs' are a potential disaster waiting to happen such as being snapped off if the cutter strikes a high point. In hindsight I should have cut them off but even so that possibility of the remaining leg being snapped off is still there. Plus we need a way of controlling the stock into the cutter. So take a piece of 9mm plywood as a base.
Scribe to suit the U-shaped stock and cut away. Screw the stock to this reinforcing base.
Cut two pieces of wood exactly the same height as our stock plus a smidgeon (where 1 smidgeon = 2 gnats). Centre the block on the centre line, add a 1mm spacer at each side for wiggle room and fix those uprights to the main baseboard thus providing a channel into which our stock can be gently pushed. The reason for those spacers and their wiggle room is to allow me to sideways adjust the block relative to the cutter in case my centreline is not quite spot on. This then limits any unwanted sideways movement of the stock and prevents the cutter from getting too excited and hurling the stock into the corner of the workshop.
Fit the cutter head, flip the reinforcing board round and adjust the cutter to the correct height. Re-flip the board and slide in. Add a couple of top boards to stop the cutter throwing the stick in a vertical direction.
We now have a nice smooth tunnel into which we can gradually push our stock. But we're not there yet.
We've made a bit of a windtunnel and so to minimise stuff being sprayed into our face and to have a modicum of protection if it all hits the fan...add a top cover and handhold.
And we're good to go.
Gently and carefully I edged the stock in and gradually moulded the inside curve. Nothing untoward happened. Nothing exploded. I still have all my fingers. Kept switching off to withdraw the stock from the tunnel to check progress and make measurements. Finally getting down to the end goal but by this time the moulding of the endgrain was a bit extreme. So reckoned I could go 1mm more. So I clamped an end stop with a green 1mm spacer.
Removed the spacer and finished the last bit. And here we have it. Prudence being the better part of valour and I will finish off the remaining part by hand.
You can see that the moulded endgrain is getting a bit brutal
So well worth the effort to make that jig and if you recall I was concerned about making room for some sideways wiggle if I'd not quite giot the centre line and tunnel perfectly aligned ? Well, I measured the ends of the shanks and they are within 0.3mm of each other whivh I reckon is pretty good.
