Jig Ready

Posted by Paul

The long rails are set to the bench and the cross rail is made and slides easily in its track. There are only 2 things stopping me from shaping the blank. I have yet to glue the Cedar blocks for the sheave into the blank and the router bit I have does not reach deeply enough through the jig to the blank so I either need to raise the blank in the jig or get a longer bit. I will try to set the blank up higher first to save me buying another expensive router bit.

I set the back rail up to the bench using a stringline and I found that there is a 5mm dip in the bench, most of the length was at the right height to the stringline but both of the ends were low so it needed to be raised by packing them up with wedges. Once the back rail was set to the stringline, meaning it was both straight and level, just to the line not necessarily to the rest of the world although ironically it was now level to the rest of the world. I then set about making the front rail level and straight to the back rail. The method here was to run a level at each end and set one corner level and at the correct distance (any distance just choose one that works) from the back rail, then using a tape measure ensure that the rest of the front face of the front rail is at exactly the same distance from the front face of the back rail. I had to pack the end with a 3mm mdf strip to get it to be level with the back rail. I then repeated this at the other end and it also needed a 3mm packer and was set to the exact same distance from the back rail.

I then set a stringline along the front rail to firstly make sure that the rail was straight which it should be if the back rail is straight and the front was set to the back rail. Only the ends are secured at this stage so there could be bends in the front rail so the tape measure and the stringline ensures that it is set straight. I then had to be sure that the front rail was at the correct height along its entire length. It needed 3mm packing along its entire length in order to be level using the 1 meter spirit level. I learnt that level can be out so you should just pick an end of the level to be at the front and use it that way the whole time, this ensures that the job stays level. Once it was packed and set and the stringline and the level now also agreed you can be sure there is no twist, no kink no dips etc and the train will run smoothly on its tracks.

I joined the 2 parts of the cross rails into one with mdf slats leaving a slot down the middle for the router bit to slide along and plenty of room in the rail to attach the router. I then attached guides underneath to stop the cross rail from moving backwards or forwards. Once the router is attached it can now only move side to side (it can also move up which is ok because it cant do any cutting if lifted up but it cannot move down any further than the side rail height).

Once the blank is secured to the bench and is square and level with no twist in it (which I will check by running a stringline down the middle at the spine) it will be a simple matter to run the router along its length resetting the height of the router to the moulds on the end as I go along the profile from back to front. I will pack the underside of the blank where needed to ensure it is steady but it will be important when doing this that I don’t create a bow in it up or down because even though I will shape the blank level with the router, any bend created under pressure will just pop out again when the blank is released from the jig. It needs to be sitting in there under no pressure at all either up or down.

I am very close to being ready to shape now. Pretty soon there wont be any reason to not shape them!

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