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Parallel Hollows

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Lonsdale73

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When hollowing out end grain, how do I get the sides parallel? I need a hole 36mm in diameter, approx 10mm deep and my largest drill bit is a 35mm Forstner. I thought I could use that to hog out most of it away and the remaining mil or so on the lathe. I'm there on the width on the outside face but the walls curve inwards like a bowl. Not sure if I'm using the wrong tool or (most likely) right tool wrongly.
 

marcros

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what tool are you using. I would probably drill and use the sharp point of a skew or a parting tool to take the last 0.5mm, taking care to make sure it is at 90 degrees to the face of the wood. you can't be sloping in too much it it goes from 36 to 35mm
 

Lonsdale73

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I've tried parting tool, a slim parting tool, skew, spindle and bowl gouge. I did think either parting tool or skew should do the job so good news is no expensive outlay on another tool to learn. Bad news, my technique needs a lot of working on! It wouldn't be the end of the world to start this part again from scratch. If I do, would it be better to start with a psrting tool to define the outer diameter and then use a smaller Forstner, e.g 30mm to make short work of the rest?
 

Lonsdale73

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CHJ":33xnbess said:
I Bore them out with a carbide tip, as I would on a metal lathe.
Now that raises another question: what does something like the Robert Sorby Turnmaster offer over a set such as their 67HS?
 

Dalboy

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Before you start to refine the inside have you measured it sometimes a bit can drill slightly oversize. Depending on the wood when sanding the inside this also can take the sides down to size.
Why does the piece have to be the exact size as some woods even when dry can move to make the round hole slightly oval therefore messing up the dimensions, unlike metal which as a lot more stable?
 

kevinlightfoot

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To finish to correct size I would use a half inch scraper'end cutting but the tool should have the side under cut to form an angle that won't touch the side of your bored hole ,just like making a recess for a box lid.It is a fairly simple task and you have very little material to remove
 

Lonsdale73

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Dalboy":1rik0gfg said:
Before you start to refine the inside have you measured it sometimes a bit can drill slightly oversize. Depending on the wood when sanding the inside this also can take the sides down to size.
Why does the piece have to be the exact size as some woods even when dry can move to make the round hole slightly oval therefore messing up the dimensions, unlike metal which as a lot more stable?
The tenon I've cut is 36mm in diameter, hence sizing. The bit hasn't cut slightly over as the tenon wouldn't go near the hole till I'd taken a bit more out on the lathe. Now it goes in a few mm and stops because of the curvature.
 

Dalboy

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Lonsdale73":3qszsaof said:
Dalboy":3qszsaof said:
Before you start to refine the inside have you measured it sometimes a bit can drill slightly oversize. Depending on the wood when sanding the inside this also can take the sides down to size.
Why does the piece have to be the exact size as some woods even when dry can move to make the round hole slightly oval therefore messing up the dimensions, unlike metal which as a lot more stable?
The tenon I've cut is 36mm in diameter, hence sizing. The bit hasn't cut slightly over as the tenon wouldn't go near the hole till I'd taken a bit more out on the lathe. Now it goes in a few mm and stops because of the curvature.
Ok that is fine but for further reference try to cut the mortice first as sizing the tenon is much easier especially on smaller holes.

How far in does the tenon need to go as sanding may sort the problem or as stated a skew on its side or carbide tool will be ideal maybe even a scraper. This all depends on the tools you have available that is
 
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