Metal parts for pole lathe

discussion of the niceties of turning on a bow, bungee or pole lathe.

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Metal parts for pole lathe

Postby TomBartlett » Fri Oct 18, 2013 10:10 am

Hi all, I've been toying with the idea of setting up a pole lathe. With winter coming and my local woodland doing regular coppice work, finding the wood for an lathe shouldn't be too difficult, however not entirely sure on how to make/source the various metal parts needed. Any advice? Thanks.
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Re: Metal parts for pole lathe

Postby Bob_Fleet » Fri Oct 18, 2013 11:09 am

Where are you?
Put it in your profile.
I can supply and so can a few others. Not sure of commercial sources.
Screwfix 12mm threaded ss rod and a friendly welder for the handle and a bench grinder are what you need.
3 sets out of 1m rod.
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Re: Metal parts for pole lathe

Postby AlexanderTheLate » Fri Oct 18, 2013 7:14 pm

Depends on how fancy you want to go... My first lathe had two of those screw in hangers as centers, the end of the screw was ground down on a bench grinder (which in it's self is a jack-tar set up) and twisted into a slightly undersized hole drilled in the stocks. The hook was used as the handle (the stocks were pieces of 2X4). You can imagine it was rough. You could even forgo the screw adjust centers and just point off two pieces of metal and drive them into the stock (but the lathe will have to be 'loaded' by bashing the tail stock with a hammer into the work piece, if that makes sense)

The usual set up is to chisel out a slot on your tail stock to fit a bolt in. Then point off a piece of threaded rod (Files,or a bench/angle grinder) that will fit the bolt. The handle can be welded on, or you could put a wooden one on with bolts and lock washers. The head stock center is the same thing, only the center does not need to be adjustable, so just drill an under size hole and tread your center into it.
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Re: Metal parts for pole lathe

Postby Brian Williamson » Sat Oct 19, 2013 10:40 am

AlexanderTheLate wrote:
The usual set up is to chisel out a slot on your tail stock to fit a bolt in. Then point off a piece of threaded rod (Files,or a bench/angle grinder) that will fit the bolt.


I'm not understanding that - do you mean a nut?

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Re: Metal parts for pole lathe

Postby AlexanderTheLate » Sat Oct 19, 2013 4:10 pm

Yes a nut... Like me. Sorry.
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Re: Metal parts for pole lathe

Postby Mark Allery » Sun Oct 20, 2013 8:01 am

I don't tend to worry about welding a handle - at least to get started with.

Just use thickish threaded bar for the centres - around 12mm or 1/2inch whatever you have access to. Drill the hole slightly undersize for the threaded bar so that it cuts it's own thread as you wind it through the wood of the poppet.

After a couple of years you might need to fit a nut if the threading comes slack through use - but maybe not - you can just pack it with some jute soaked in beeswax/linseed oil.

For a handle to wind the adjustable centre I just use an appropriate piece of metalwork or wood a few inches in length trapped between two nuts on the end of the threaded bar. An old landrover normally serves to provide all of the parts needed except a length of threaded bar for the adjustable centre. I often use an old shock absorber bolt for the fixed centre and a spring hanger for the 'handle'.

Frankly whatever works to get you going - I have seen polelathes working on just two nails as the centres and a wedge to 'adjust' one of the centres, so you can be as basic as you like or spend as much time overengineering as takes your fancy,

cheers

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Re: Metal parts for pole lathe

Postby tagnut69 » Sun Oct 20, 2013 6:52 pm

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Re: Metal parts for pole lathe

Postby TomBartlett » Fri Oct 25, 2013 4:31 pm

Thanks for the responses. I'm Southend-on-Sea, Essex, UK. The woodsmith store stuff is exactly what I was after.
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Re: Metal parts for pole lathe

Postby jrccaim » Sat Oct 26, 2013 5:37 am

I made a gigantic post on the subject -- and it went away. This is because I neglected to to check the "log me in automatically" box on login. Poster beware!

Anyway, for a pole lathe you need two metal pieces: the headtstock center and the screw-in tailstock center. The headstock can be made of mild steel rod. You need maybe 50mm of it, a couple inches. Not precision stuff! For the tailstock screw-in you need either threaded rod or a longish bolt, threaded all the way. . It should be maybe 10-15 cm long and again, not precision work. Somebody suggested M6x1 (Imperial 1/4-20) for both. I suggest M10x1 (US 3/8-16) and the thread count (pitch) is not important. I like the thicker diameter because it is beefier. You can use whatever you have.

Next job is to make a 60 degree point on both centers. 30 deg each side, 60 deg included angle. For this I suggest making a template.I use beer or soda cans, readily available at your friendly roadside. It is a fishtail template. You can cut beer cans with scissors. Lay it out very carefully. Now we go cut the point. If you have a metal cutting lathe, easy. Set topslide at 30 deg and go cut it. Don't have one? Chuck it in any electric drill. Get a file. Turn on the drill. File the point until it matches your template. It is actually faster than a metal cutting lathe (I have done both). Do not drill any holes in the poppets yet.

Now we drill some holes to accept the centers. It is absolutely essential that these holes be at the same height, whatever you have determined it to be. Way I do this is to do the headstock first. Mark out the headstock center first. Drill a hole that is a really tight fit on your center. You should have to pound it in with a soft hammer. If you are a bit loose, I suggest epoxy. You should have maybe 10mm of center hanging out. Let epoxy, if any, set before going on. Then bring tail stock hard against headstock. Hit tailstock a good whack with a mallet. This puts in a "centre pop" and you can drill right there. It is essential that both holes be level and square. If you have a pillar drill, USA drill press, this is easy. If you do not, use a level taped to the bit as a level guide and a square as a square guide.

Next, how big are these holes? The headstock should be a very tight fit. The tailstock hole is more complicated. You are going to tap it without a tap. The proper diameter is determined by the tap equation: hole diameter = nominal outside diameter - pitch. Example M 12x1. Hole is 12 - 1 = 11mm. This works in Imperial as well, but you will need a calculator to do it. If in doubt drill undersize. Now you force the screw into this hole, turning clockwise. For this I attach vise-grip pliers to the screw and use all the pressure I can get. If you used a long bolt you can use a spanner or wrench depending on you sider of the pond. Wood is not as compliant as metal. It may be too tight. Slather oil all over the screw and work it back and forth until it goes in easily. If it is too loose, wrap a piece of plastic (supermarket shopping bag, for instance couple of times around screw, really tight, the threads should show, and twist it back in. Magic. It will hold now. This, after all, is how a nyloc nut works! All this megilla is unnecessary if you have a say M10x1 tap (or whatever) on hand. In this case just tap the tailstock as if it were metal, and it is much easier than forcing the screw in. A M10x1 tap is probably a few quid, the tap handle is more, so maybe you are out ten quid. Up to you whether it's worth it. It is so much easier to use a tap. I have done both. I have a fairly comprehensive tap set, Imperial up to 3/8 and metric up to M12. One of my "best buys" from Grizzly.com at $70. So nowadays I just tap the hole in the tailstock but I assure you you do not need a tap set. Just more work, that's all.

Oh golly what a long post. But last point. "Welded handles" for your tailstock. Are you joking? No!! What I do is cross-drill the screw to accept a reasonably sized nail. Over the sharp point of the nail I put a suitable stopper. Keep the nail from falling out. Currently my polecat lathe sports a wine-bottle cork as a stopper. Available really cheaply (indeed, free) almost anywhere. Enjoy the wine.
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Re: Metal parts for pole lathe

Postby gavin » Mon Oct 28, 2013 8:01 pm

jrccaim wrote:Now we drill some holes to accept the centers. It is absolutely essential that these holes be at the same height, whatever you have determined it to be. Way I do this is to do the headstock first. Mark out the headstock center first. Drill a hole that is a really tight fit on your center. You should have to pound it in with a soft hammer.

Always a good idea to drill some test pieces first and try the fit of your metal thread with slightly differing diameters. If you can use the same species and ideally similar stock as your real poppet heads.

jrccaim wrote: If you are a bit loose, I suggest epoxy.

Also a piece of nylon cord laid in the hole before you re-introduce the metal thread will work to make the apparent hole diameter smaller - for which idea I credit Mike Abboot author of the sadly out-of-print Greenwoodworking
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Re: Metal parts for pole lathe

Postby jrccaim » Tue Oct 29, 2013 5:19 am

Agree with Gavin completely, as usual. One more thing on drilling holes for centers. All drill bits are not the same. If you buy say an M12 drill, chances are that it is slightly oversize. Especially if you buy the usual woodworking bits. They are intentionally oversize. This is so's you can push a nominal 12 mm dowel through it. The dowel itself will very wildly, but that is off-topic. So my practice is to measure the drill before I do the hole. I also measure the center itself. Steel rod is a lot more accurate than a wooden dowel, but still, maybe it was Monday morning at the factory :). A machinist's tight "press-in" fit.is .002" (about .05 mm) in steel. That is, the hole should be .05mm smaller than the rod. In wood we cannot get these accuracies, so we settle for 0.1mm. Or even less depending upon species; pine can be forced much more than, say, ash. Now most people building pole lathes are lucky to have bits in even millimeter sizes, or the usual Imperial fractional series. So what do you do then? I say epoxy. If it is a sliding fit, or even a mildly fiddly tight fit, put some epoxy on it. Make absolutely sure there is no trace of oil on the center. Rough the shank up with a coarse file, or a cold chisel. (Not the point!) Make sure the hole is as clean as can be, no chips or sawdust. Let the epoxy cure at least overnight. Epoxy is wonder stuff, but oil defeats it completely. So do chips, sawdust and other debris.

Which brings me to the subject of measuring drill bits, or steel rod. For this purpose a ruler is of no use. What you want is vernier calipers (or callipers. both spellings common). If you want to be fancy you can get a pair of digital calipers that will read out to .0001" or 20 microns, will work metric or Imperial, can use it as a scribe, hardened tips, wonderland ... but it will cost you about 25 quid UK per Axmister. For one pole lathe? Not worth it. For years I made do with a pair of plastic vernier calipers made in China of course. The big one can hit .05mm and less by interpolation. Perfectly good for bodger's work, the little one good for miniatures, I still use them even though I use the digital brethren for machine work. The plastic calipers cost me 0ne Dollar. In Britain you can also find these things at car boot sales really cheap. Made in metal, too. You will have to learn to read the vernier scale. I learned this in High School in Venezuela and I am sure you can too. Lots of stuff on the net to get you started. The dial calipers are good too, but actually the vernier scales are more accurate, if somewhat harder to read.
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Re: Metal parts for pole lathe

Postby Jan Krobot » Thu Mar 05, 2015 6:41 am

Hi
Is it better to heve pointy ends of those metal centres needle-sharp or bit blunt?
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Re: Metal parts for pole lathe

Postby Ian G » Thu Mar 05, 2015 9:08 pm

Hi Jan, I would make them as sharp as you can and if you have a felt wheel on your grinder get them well polished. I've attached a picture or threaded rod, if you hacksaw four notches in the end of the rod it will cut a clean thread through your poppets. 11mm hole for a 12mm rod. I've done this with all my poppets and they are still going strong after several years of heavy use. Before I did this wee trick my poppet metal work would work loose in a couple of years with hard use. Hope this help. Enjoying all your posting it good to see someone asking plenty of questions..that's what the forum is all about.

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Re: Metal parts for pole lathe

Postby gavin » Thu Mar 05, 2015 10:25 pm

Jan Krobot wrote:Hi
Is it better to heve pointy ends of those metal centres needle-sharp or bit blunt?
Jan

60 degrees and get the pointy bit bang in the centre
If you can find someone with a metal working lathe, get them turned on that.
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Re: Metal parts for pole lathe

Postby Jan Krobot » Fri Mar 06, 2015 12:56 pm

If you can find someone with a metal working lathe, get them turned on that.

I know local blacksmith with metal working lathe and already gave him two bolts to turn, 60 deg as you advised somwhere here. On his advice I didn't use threaded rod but long bolts. It's because of their higher strenght compared to threaded rod. I tried to bend one (and actualy bent it) and it realy IS stronger, far stronger :) Maybe it's not necessary but "better oversized than potentialy undersized".
I would make them as sharp as you can

I will too :) ...and what are "poppets" you mention, dictionary is no use here, nor wikipedia.
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