Tang Length/Shape

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Tang Length/Shape

Postby Donald Todd » Wed Nov 04, 2009 11:56 am

I've just made a new mandrel according to Paul's directions. I used three screws for the tangs. These are 4 mm diameter and at present project about 18mm; the smooth part of the shank. Is this too long? These are plain steel which I have roughed up to hold better as the previous smaller ones kept pulling out. I have also sharpened the ends all the same way, so if I present it correctly before mounting they will cut the grain and hopefully reduce splitting.
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Re: Tang Length/Shape

Postby paul atkin » Wed Nov 04, 2009 1:01 pm

heres one of mine donald
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tangs 2.JPG
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i use 10mm threaded bar, screw it in about 40mm or so and fix with super glue, these tangs are about 20mm long, grind flats on just with a slight taper or even parralell. leaving a bit of the thread on the edges really helps with holding your blank, i have never needed to use three tangs,,, 4mm i reckon is on the small size but try itand if it fails just make another one
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Re: Tang Length/Shape

Postby Donald Todd » Wed Nov 04, 2009 5:44 pm

I used three just as it seemed more balanced. The mandrel is 42 mm diameter, still a bit small, making the tangs rather close together, but the lathe won't take very big bowl blanks. I am not sure I want to build another lathe, partly as I was getting quite a lot of pain in my (static) hip when turning the last 2 bowls. It's barely noticeable doing spindles. I was just getting into this and I have a BIG bit of Norway Maple!
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Re: Tang Length/Shape

Postby paul atkin » Wed Nov 04, 2009 6:11 pm

Donald Todd wrote:I used three just as it seemed more balanced. The mandrel is 42 mm diameter, still a bit small, making the tangs rather close together, but the lathe won't take very big bowl blanks. I am not sure I want to build another lathe, partly as I was getting quite a lot of pain in my (static) hip when turning the last 2 bowls. It's barely noticeable doing spindles. I was just getting into this and I have a BIG bit of Norway Maple!

are you using a plank for your treadle ???????? if so stand on a block to bring your hips up level it saves a lot of pains
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Re: Tang Length/Shape

Postby Donald Todd » Wed Nov 04, 2009 6:54 pm

I'm using the basic bodgers' treadle with the cross bar set very low; too low for the required power; I forgot to change that from when I was doing demos. I did "shorten" the treadle by lowering the cord attachment. I do see what you mean about balance. I found that it was easier, even desirable, to change foot; I was leaning into the lathe.
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Re: Tang Length/Shape

Postby paul atkin » Wed Nov 04, 2009 7:01 pm

try using a plank matey, its a lot easier on the old body, in the workshop i use a lump of 6x2 about 7/8 foot long, i cut some bulk out of it to reduce weight but left myself a nice lump on the end for my foot
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Re: Tang Length/Shape

Postby Donald Todd » Wed Nov 04, 2009 7:09 pm

Thanks, I've just reverted to spindle mode to make a stool for my Mum ; it might be a while before I get back to bowls. I need to reconfigure the whole treadle system; complicated by the lathe being very light and moveable. I have been moving it around the garden and even use it in the greenhouse!
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Re: Tang Length/Shape

Postby Donald Todd » Fri Nov 06, 2009 5:44 pm

I had to finish the spindles in the greenhouse this morning as it was p…ing with rain. I haven't tried bowls in the greenhouse yet; certainly no room for an 8' plank, which I just realised that I have, though it may be a bit flimsy. This of course means I will need a much stronger pole!
I am assuming that the idea is to get near vertical movement of the tip so the cord can run through the bed; the easier action being a fringe benefit. I seem to recall seeing a picture of Gavin's somewhere. Have you any idea how much effective movement you get? With the foot being so near the "treadle" tip, I don't expect it to be much more than the foot's movement. I am at a disadvantage here as I am only 5' 5"!

found Gavin's post… topic by Declan Kenny on "treadle"here.
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Re: Tang Length/Shape

Postby paul atkin » Sat Nov 07, 2009 4:34 pm

as for movement donald, just turned a little 6 in bowl and i get just over 2 revs on each stroke, the mandrel is about 45mm or so, also i use bungee cord in the workshop
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Re: Tang Length/Shape

Postby Donald Todd » Sat Nov 07, 2009 6:16 pm

It will take some getting used to. Spindle turning I get 10+ turns per stoke and no noticeable inertia until the work is 2" or more. The slower rate of pedalling feels very odd. Have you tried one of those Spanish jugs yet?
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Re: Tang Length/Shape

Postby paul atkin » Fri Nov 13, 2009 8:05 pm

no time to play at the moment matey, tons of stuff to do and falling behind day by day but one day i will have a go
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Re: Tang Length/Shape

Postby Donald Todd » Sat Nov 14, 2009 5:37 pm

Latest mandrel fine for a wee bowl but I had trouble getting the core off. I tried splitting it and bent the tangs! This is just a result of too small a bowl(4"): I took too much core away. I'll knock it off next time.
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