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Taper screw

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Gordon W14/11/2009 10:18:14
2011 forum posts
Does anyone have any ideas? I want to make a taper thread, like the end of a woodscrew, about 2" dia X about 6" long ,coarse thread, this will be for a log splitter, so OT a bit. My lathe is 8" swing x 16".No probs turning the taper, only thing I can think is to weld a spiral on then hand fettle, this is a one off so don't want a huge amount of tooling to make. And no I don't have a mill.
Circlip14/11/2009 11:18:34
1723 forum posts
Use Tailstock offset method for tapering and screwcut as normal. Use Ball end centres.
 
  Regards  Ian.
Gordon W15/11/2009 11:34:44
2011 forum posts
Thanks for idea, just been reading other thread about taper turning, seems the offset will be way too much for this angle and depth of cut. It will need a pointy end, more or less. Just had idea,_ drill and weld in large coachscrew to get the sharp point, then offset tailstock and screw at shallower angle, will go and fiddle about. Where can I get a bell end center drill (mail order)?
Ian S C15/11/2009 11:54:37
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7468 forum posts
230 photos
Just off set the top slide,you'll need to move it along a time or two,but you won't have to set over the tail stock,and more important you won't have to reset the thing after you'v finished(thats the important bit).As gordon says the angle is really too big for this method-setting over that is.IAN S C ps if you were in this part of the world no way would you buy a bellend center.
Terryd15/11/2009 13:57:33
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1946 forum posts
179 photos
Just a bit of information. A traditional woodscrew does not taper.  The crest of the threads are parallel, it is the core that tapers.
 
TD
chris stephens15/11/2009 17:21:25
1049 forum posts
1 photos
Hi Gordon W,
I seem to recall that ARCEURO sell them, but be very careful when using theirs. The small pilot is very small and will break easily, don't ask, don't be tempted to drill normaly. The technique is to "peck" drill, this way the swarf will not jam up the flutes quite so quickly. It is good practice to do this with all centre drills! Saves a lot of breakages.
chriStephens
Gordon W16/11/2009 14:48:58
2011 forum posts
Thanks for the info. will buy bell end cd for other job. For interest the best ideas so far are 1-turn taper on t/slide and weld spiral on. 2-hand turn the screw thread, never tried that, sounds scary.
charadam16/11/2009 15:13:40
185 forum posts
6 photos
Could one of these in the 1 1/2" diameter form the basis?
 
JohnF16/11/2009 23:13:14
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1243 forum posts
202 photos
Do you have a taper turning attachment for your lathe? If so the job is easy -- just turn your taper with the top slide set at 90deg to the bed [or 90deg to the taper] then screwcut as normal with the taper turning attachment still engaged.
Ian S C17/11/2009 08:58:01
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7468 forum posts
230 photos
Gordon what pitch is the thread?I would have thought it would be too coarse to cut on the lathe as a normal thread ie 20 to 30mm or 1 per inch or more.IAN S C
Gordon W17/11/2009 09:44:45
2011 forum posts
Hi, charadam-thanks for that link, one of those would maybe work, will go down the pub and see if anyone can get one.. Don't have taper attachment, one day will make one but for a one off seems a lot of work. Pitch I,m guessing at 2 or 3 per inch but this is the experimental bit.
Ian S C17/11/2009 10:21:11
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7468 forum posts
230 photos
Will your lathe cut that?My 1324 BH Taiwanese lathe will only go to 4tpi,I thought that was fairly coarse,I'v used that to make some ordenary wood screws somewhere about 1/4" dia.
Gordon W17/11/2009 11:33:44
2011 forum posts
IanSC:_hello,I've just been in the shed counting changewheels, should be able to cut 10mm pitch if the wheels will fit in the banjo, but I've got the toothache and all brain power has stopped. Will try again in a couple of days.
charadam17/11/2009 23:15:36
185 forum posts
6 photos
Posted by Gordon W on 17/11/2009 09:44:45:
Hi, charadam-thanks for that link, one of those would maybe work, will go down the pub and see if anyone can get one.. Don't have taper attachment, one day will make one but for a one off seems a lot of work. Pitch I,m guessing at 2 or 3 per inch but this is the experimental bit.
 
   Gordon,
 
Strange story -  i was mowing the lawn a few days after the Post Office had renewed a telephone pole in my garden. Nearly ran over a 1/14" sample of the coach screw (it apparently is, or was used on the past,  to secure footsteps to large diameter poles) that they had discarded on my patch.
I didn't know such beasts existed until then - and if I can find the item in my scrap pile, your are very welcome to it!
 
ATB,
 
Charles
Steve Bell 118/11/2009 10:09:40
5 forum posts
Might sound a very poor way of doing it but it's worked in the past for me, and comes from something my father read.
 
Turn the taper as per usual  then undo the retainng for the cross slide screw, so the cross slide can be pushed backwards and forward by hand.
Set up for screw cutting as per normal and use a light spring to apply the force to pull the cutting tool onto job. A long spring is needed if the diameter of the taper changes a lot so as not to put excessive pressure on the larger diameter.
When I did it I used an elastic band (!) and got surprisingly good results.

Steve
Ian S C18/11/2009 10:43:54
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7468 forum posts
230 photos
Charadam,if the telephone pole hardware in uk is the same as here in NZ I think you will find it similar to wrought iron ie if you cut it up you find layers of slag inclusions.I often use old bolts,and other junk,and have tried pole hardware,including climbing bolts(screwed in side of pole to climb for servicing),usually can't use the item because of the inclusions.Some times you can get coach screws either hex or square head ungalvanised,ie black like machine bolts,these are mild steel.IAN S C
Gordon W19/11/2009 10:22:47
2011 forum posts
Charadam:_ strange story, have just been at the back of one of my sheds to clear rats, and uncovered a rotten wooden box containing old ex telephone/electric pole fittings inc. large coachscrew, very heavy galvanising on all. Thanks for the offer tho'.   SteveB, like the idea,but with deep threads might be too much, wonder if a taper guide at back of slide will work? Sort of hand held taper turning atttachment. Any way this idea will stay just that until I do a few calcs., (and paint the bathroom)
Ian S C19/11/2009 11:09:43
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7468 forum posts
230 photos
I'm a bit far away,but I'v got some wood screws here from the nearby railway line,used for screwing the tracks to the wooden sleepers,aprox 2 threads to the inch.IAN S C
Nigel McBurney 124/11/2009 21:44:53
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1101 forum posts
3 photos
Hi  Woodsplitter screws  have a buttress thread,they are hardened and difficult to cut,if driven by tractor pto they need to be l/hand,the point is detachable /replaceable to cope with wear and the thread is finer on the detachable point about 2mm pitch,the body part is  threaded coarser at about 3mm.the only sensible way is spiral milliling but even the universal dividing head will will run out of gears,a short lead attachment is essential and in fifty years I have not even seen one of these attachment though they are illustrated in most older tech books,if the thread is worn they will not work.so do not bother unless the screw can be hardened,I know i have tried the points cost over £70 and the local woodman has asked me many times if I can make them cheaper,for home made splitters go hydraulic,screw splitters are peferred in the trade as they are quicker,hydraulic are more reliable . nmcb
Gordon W25/11/2009 16:43:22
2011 forum posts
Thanks Nigel,I've just been to look at a tractor/hydrualic screw splitter and of course you are right.My idea was to make one electrc motor/flywheel drive but looks like a non-starter. But I've been reading Milling in the lathe, Tubal Cain. In there is description of spiral fluting and etc. using a cutter head in the toolpost, this might be adaptable to scerw cutting 2 or 3 start threads on a taper, but will have to wait.

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