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Small hollow form

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Chippygeoff

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Hi Folks.

I am going to make a series of hollow forms, about 20 in all. They will all more or less be the same, I am only going inside a maximum of 2inches. the top opening will be an inch wide and as i go down it will widen to an inch and a quarter and then tapering down to nothing if that makes sense, rather like the shape of an inverted half of an hour glass. I will probably drill an inch hole to begin with and the widen the wall inside. I was wondering if a side/round 3/4 scraper would be the tool for this as I will have to clean up all of the inside and ideally with the minimum of sanding. I will have to go and buy the tool so would like to get it right first time. Many thanks.

Geoff
 

chipmunk

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Hi Geoff,
I think that it's a difficult question to answer because there are so many unknowns (some known and some unknown - with acknowledgement to Donald Rumsfeld :wink: ...

How big are the hollow forms and how thin are you planning on making the walls?
End grain or side grain? If it's side grain, getting a good finish straight from a scraper will test your sharpening and tool control
Timber? Some timbers like cherry will almost cut themselves whereas something like sapele will fur up unless cut cleanly.

Rather than using a conventional scraper I personally would try to use a spindle gouge for that limited amount of hollowing. A 3/8 SG with finger nail profile should make relatively light work of that. You can also use it to scrape the inside too if you feel the need. A 1/2" SG sharpened finger nail style would also work and the Richard Raffan back-hollowing technique would be ideal if you know what that is.

If you are looking for an excuse to buy a new tool :wink:, then I'd be inclined to try a Sorby 826H shear scraper since this will come closest to giving you a good finish from a scraping tool. Try googling an image of "Sorby 826H shear scraper". It's designed to sit on the toolrest on one of the faces of the square shank and present the round cutter at 45 degrees to the work to produce a shearing cut.

Incidentally it's also a very easy tool to make yourself. You can buy the round cutters for about £7-8 and then it's just a piece of 1/2" square bar (Homebase or B&Q sell rolled square section of this size in 1m lengths) mounted in a handle with a step in the end shaped and tapped for an M5 screw. Sorby also sell the M5 socket head screws or you can buy stainless ones in bulk from Screwfix.

Sharpening the round cutter is very easy on the lathe with a Jacobs chuck in the headstock, a short length of metal rod tapped for M5 in the end and a diamond hone. Alternatively lay the cutter top face down on a flat stone or hone and rub :D

Hope this helps
Jon
 

jumps

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chipmunk":3l6e560f said:
Incidentally it's also a very easy tool to make yourself. You can buy the round cutters for about £7-8 and then it's just a piece of 1/2" square bar (Homebase or B&Q sell rolled square section of this size in 1m lengths) mounted in a handle with a step in the end shaped and tapped for an M5 screw. Sorby also sell the M5 socket head screws or you can buy stainless ones in bulk from Screwfix.

Sharpening the round cutter is very easy on the lathe with a Jacobs chuck in the headstock, a short length of metal rod tapped for M5 in the end and a diamond hone. Alternatively lay the cutter top face down on a flat stone or hone and rub :D

Hope this helps
Jon
Well it helped me! After reading this earlier I found myself in B&Q....light went on and, amongst the things I walked out with was a 1m 12mm12mm rolled iron bar.

Having a number of cutters with a swan neck multitool (Sorby) it took 10 mins to make up a 'tool' to handle (no pun intended) deeper/straighter with the triangular cutter head and the other half of the bar will only take a little longer to knock up as a dedicated sheer scraper...I just had to turn up an old pine log to try it out instead of finishing up on tool building.

Now I am sure the same rod, or better :D , cheaper elsewhere but it was one of the better £6 I've spent.
hanks for the tip.
 

Chippygeoff

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Thanks Jon and Nev. Got it sorted now. I have two of those multi tip tools, one by crown and the other by Sorby. I just cannot get on with them, as far as I am concerned they are the most useless tools i have ever bought. I know it is probably me not using them right but I have tried several times to use them for cleaning up bowl gouge marks inside bowls but to no avail. I now have proper scrapers and they are a delight to use. I cannot see the 826H in any of my catalogues but I went and bought the 824H hook nose scraper and it did the job brilliantly, it is the first time i have used a scraper to hollow out from start to finish. Thanks again.

Geoff
 

chipmunk

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I'm glad you found it useful ... and inspiring :D

I have to admit that I very rarely buy the basic sorby cutters these days and have taken to making my own out of HSS metal lathe parting tool blades cut with a Dremel cut-off wheel and drilled with a 5mm TCT tile drill. Old planer blades would work too. It's pretty easy to shape the basic ones on the grinder.

These guys sell the blades and their service is excellent...
http://www.arceurotrade.co.uk/Catalogue/Cutting-Tools/High-Speed-Steel-Toolbits

If you are going to try drilling HSS, use plenty of cutting/tapping fluid and drill slowly after dimpling the surface of the HSS in the right place with a grindstone in a Dremel. I find one cheap tile bit will drill about 3 holes before chipping away so make sure you buy more than one.

Trouble with going down this road is that you can quite easily end up making more tools than you really need!

...but that's a nice problem to have 8)

Jon
 
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