Hi all
ok here goes , basically as you know it all made from 25mm MDF , first rip the sheet in equal half across it’s width this gives you two pieces roughly 1.2m square turn one end over by folding end – end length ways and square up and line up the two machined cut edge’s .
First measure in 600mm from left hand machine edge along the front edge & repeat along top edge and mark a pencil line , now repeat 600mm up the left & right hand sides and mark a line , you have now divided the sheet into four 600 mm squares . This is then giving you the common centre point where the lines cross each other.
Next measure the foot print of the base of your saw. mine was 540mm across the front * 680mm in depth if my memory is correct , (adjust measurements for your own saw size), so now half these measurements , starting from your vertical centre line at the common centre point where the lines cross mark up 340mm and down 340mm and on the horizontal line mark 270 mm in both direction from the centre line , when line are drawn in, this is gave me the footprint size of my saw .
On my saw I have four feet 100mm Square * 30mm wide (L shaped) if you have something similar draw these onto the board as well (it’s important later) ok once you done that you need a large compass, or a set of trammels, measure about 25mm inside the inner edge of the four feet by about 25mm set trammels or compass and draw your first circle this is the first groove for your ball bearings now do the same about 60mm outside the corner of the feet and mark the second circle (second groove for ball bearings) , this now places your saw directly between the two grooves which will displace the weight evenly between the two ball bearing runs , right now strike you outer finish circumference from centre common point - to the left hand edge of the 1.2m square sheet and mark the circle , It’s important to do this I cut mine circumference on the band saw , it’s so simple, honest.
Ok so far.
Now whilst both sheets are still together depending on what size dowel rod you have drill a hole of same diameter through both the sheets at the common centre point , this hole will first be used as the centre swivel point whilst cutting the out diameter on the band saw and whilst routing out your grooves for the ball bearings also now whilst the new circular base is still at the band saw remove the surplus off cuts from around it , (cut one sheet at a time NOT both together as they are much to heavy to handle for safety reason) when both circles have been cut the centre common point will need to be drilled larger 12.7 ish or there a bout’s to accommodate the bolt to bolt the two section together which you’ll need to chop the hexagon head flush into the underside surface before the lower circle is secured to workshop floor first before final assemble .
MAKING THE JIGS TO CUT THE CIRCLES
1ST JIG
You’ll only need scrape timber don’t use any thing expensive. Find something wide enough to balance a half sheet of 25mm MDF on it only need to be about 300mm. I think at this time I let the picture explain how it’s done quite simple really. Jig clamped to bandsaw. Photo showing centre swivel pin. That’s your first jig done.
CUTTING THE CIRCLE
Ok, all I can show you here because I didn’t take any photos of the circle being cut but what I can show is the waste material left in position which I think you’ll get the idea how it is done , with the half sheet in position with the end of sheet resting against the band saw blade and the centre common swivel dowel through the hole you previously drilled in your half sheet of MDF when machine is running just feed the sheet through your hands from right hand to left hand with a steady flow of movement your band saw will cope with the full circle easily , I used a ¾” blade with no problems at all , there as I said simple, any way a photo.
Please bear in mind this photo was taken as a mock up for this post only normally the blade height would not be set that high up when in use. Now repeat again for second circle.
2nd JIG.
Ok again just scrape wood In this case I used hardboard only because that’s all I had.
Remember this Photo is also a mock up for this thread only. Here I’m sorry you have to use your imagination that the circle of MDF is there the swivel dowel is in the inner hole to cut the inside groove for the ball bearings , the other hole you see if for the second groove for the ball bearing. Once you cut the two grooves into both circle your now ready to start assemble, (but don’t forget to enlarge the centre common hole to take your centre bolt and also cut the hexagon bolt head into the underside of the bottom circle), do that and then secure bottom circle to the workshop floor (hope your floor is level) if not you know what to do .
BALL BEARINGS
Ok so now the bottom circle is secured to the floor , I used 12.7mm ball bearing with the grooves cut to about 5.5mm in depth on both circles this left a space between the two surfaces of about nearly 2mm ( now you need a 2mm washer slip it over the centre bolt roll all ball bearing into the grooves, I bought 250 in all which to be honest wasn’t quite enough, so buy about 300 in all this should leave just a few over , but don’t do what happened to me when opening the box the inner plastic bag split open and yep all over the workshop floor, oh pipper it took hour finding them all , What joy. Now slip on the top circle and the set of grooves will mate up with the ball bearing and gentle tighten down the centre bolt , there you go it’s ready to lift and position your saw to it .
This shows the legs of saw sat between the two ball bearing grooves
finally the turntable still not yet finished or secure more to follow as soon as possible .
hc
.hc
