I need some giant double ended wood screws of maybe 10mm or 12mm diameter by 100mm long. (or bigger)
(fixing 5"x5" timber baulks upright to 10" x 5" oak railway sleepers to form a handrail over a bridge). So far I've failed to find a supplier so may have to make them..
So how the heck do you cut a tapered woodscrew thread on a screwcutting lathe???
AWEM
Depending on the lathe, you can do screw cutting combined with a taper turning attachment. This only gives you a cone shape for the minor diameter, but that can work. Do the major diameter parallel with a taper to the point.
Mark Rand RTFM
If you predrill the holes the screw doesn't need a sharp point. You can turn them between centers and just step the end down with shorter and shorter cuts, then file smooth.
IIRC I used my vee-belt pulley bit and stopped each pass 0.020" shy of the previous one to get a starting taper.
jsw
You could use M12/12mm Dowel screws, cut the M12 down to about 12" long and use a studding connector to join two together. A short counterbore will accomodate the stud connector.
--Try a chandlery; if you can make do with wood screw on one end and a machine screw on the other these are common.
Get some suitably sized coach screws, cut the heads off and weld them together.
Bob
Dunno but why don't you just fix them with angle brackets and normal length screws?
That would solve the small matter of how to screw in the second one, too. Do you rotate the handrail or the bridge?
jsw
That would work for the first screw but what about the rest,
*shrug*
Maybe Andrew doesn't NEED a rest after his first screw? --
Chris Edwards (in deepest Dorset) "There *must* be an easier way!"
ay!" =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0
Double-ended?
jsw
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sleepers
'cos it would look tacky !!!
AWEM
sleepers
That would solve the small matter of how to screw in the second one, too. Do you rotate the handrail or the bridge?
jsw
Handrail fairly obviously will be fitted when all uprights have been planted. This brdge is 6 metres long and is slightly arched (3 metre radius iirc) So the handrail will be several 5" x1" planks laminated as they are fitted, and held down into the curve as the glue sets. When firmley glued it will be carved/ planed / routed to a smooth shape
AWEM
Seems unlikely as that makes it a semicircle that hardly fits the slightly arched description!
Now that coupled with the above dimensions calls for steaming them before bending. On balance I reckon the radius of curvature is wrong. Should it be 30 metres radius? Henry
Around here the big-box home improvement stores sell them pre-bent to that shape.
jsw
Use a taper turning attachment!
Steve R.
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You may well be right. The 'hump' is about 18" over the full length. By the time the uprights are planted on it the radius will be even gentler and I don't anticipate issues bending the planks if I can get them in full lengths.
AWEM
With a screwdriver!
Chris
PS. Yeah, I know but it's been wanting to be said for quite a few days now.
What does a screwdriver for double-ended screws look like?
A double-ended screw with the center knurled, probably not what's needed here:
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