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Drilling large diameter holes ...
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AndrewC



Joined: 14 Feb 2008
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Location: Belgium

PostPosted: Fri Nov 12, 2010 1:25 pm    Post subject: Drilling large diameter holes ... Reply with quote

Looking for some advice on machining large holes in Acetal or maybe wood about 20mm thick. I want to make some mounts for some T tubes and other optical tubes (Micro 4/3 adapters and the like). The mounts are basically to hold optical assemblies on macro benches when I'm using a compact camera attached to extension tubes. Diameter is around 51mm. That is way too big for my bench press. The ideal tool would be a lathe but I don't have one. I was thinking of maybe using a hole cutter (tubular saw type designed for ripping out large diameter holes) then sawing across a diameter, line each semicircle with thin cork and then compressing them around the tube. Or maybe the same thing but cut out a square and clamp that around the tube - would give me 4 points of solid contact. Any other suggestions ?

Andrew
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elf



Joined: 18 Nov 2007
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PostPosted: Fri Nov 12, 2010 2:21 pm    Post subject: Re: Drilling large diameter holes ... Reply with quote

AndrewC wrote:
Looking for some advice on machining large holes in Acetal or maybe wood about 20mm thick. I want to make some mounts for some T tubes and other optical tubes (Micro 4/3 adapters and the like). The mounts are basically to hold optical assemblies on macro benches when I'm using a compact camera attached to extension tubes. Diameter is around 51mm. That is way too big for my bench press. The ideal tool would be a lathe but I don't have one. I was thinking of maybe using a hole cutter (tubular saw type designed for ripping out large diameter holes) then sawing across a diameter, line each semicircle with thin cork and then compressing them around the tube. Or maybe the same thing but cut out a square and clamp that around the tube - would give me 4 points of solid contact. Any other suggestions ?

Andrew


Is a bench press the same thing as a drill press? I think a flycutter style hole saw would work best because you can adjust the size accurately. Replacing the pilot drill with a counterbore would also help.

Another option would be to just use PVC pipe and add 3 nylon screws to hold the lens or adaptor. It may take several rows of screws to keep the lens/adaptor from tilting.

p.s. I don't think adding cork will gain you very much as neither wood nor acetel should scratch the lens/adaptor.
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AndrewC



Joined: 14 Feb 2008
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PostPosted: Fri Nov 12, 2010 3:51 pm    Post subject: Reply with quote

Yes, bench press is the same as a drill press. The cork was just to provide some kind of malleable layer to get a snugger fit - I was thinking maybe 1mm thickness.

I thought of the PVC pipe and centering screws but something puts me off - not sure what - maybe not firm enough ?

What's a flycutter hole saw - I thought flycutters were for surface finishing ? Do you mean something like this: http://www.holepro.com/drillpress.html

Andrew
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elf



Joined: 18 Nov 2007
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PostPosted: Fri Nov 12, 2010 4:15 pm    Post subject: Reply with quote

AndrewC wrote:
Yes, bench press is the same as a drill press. The cork was just to provide some kind of malleable layer to get a snugger fit - I was thinking maybe 1mm thickness.

I thought of the PVC pipe and centering screws but something puts me off - not sure what - maybe not firm enough ?

I think the cork would only be necessary if you expect a lot of movement between the acetel/wood adaptor and the lens.

The PVC pipe and centering screws would be my last choice as well. It wouldn't be as secure as a solid piece that can grip all the way around the lens.

AndrewC wrote:

What's a flycutter hole saw - I thought flycutters were for surface finishing ? Do you mean something like this: http://www.holepro.com/drillpress.html

Andrew

That's what I was thinking of, but you should be able to find single cutter ones in any hardware store for quite a bit less.

I'm imagining you need something like this: http://www.photomacrography.net/forum/viewtopic.php?t=5660 but without the fiber optics attached.
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g4lab



Joined: 23 May 2008
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PostPosted: Fri Nov 12, 2010 5:20 pm    Post subject: Reply with quote

I recommend the fly cutter too.

If you have Harbor Freight or some similar importer of inexpensive far east tools you should be able to buy one for under $10.

I was looking at one to make holes in wood for ocular storage.

http://www.harborfreight.com/power-tools/power-accessories/adjustable-circle-cutter-37370.html
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Harold Gough



Joined: 09 Mar 2008
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PostPosted: Sat Nov 13, 2010 1:47 am    Post subject: Reply with quote

Not the most elegant method: Drill a start hole just inside the circumference and cut with a jigsaw (power tool) or a keyhole saw (muscle power). For the latter, Stanley Knife accessories include a blade (possibly not as fine as the proper tool).

http://www.amazon.co.uk/Stanley-1275B-Saw-Blade-Wood/dp/B0001IW5IG

Harold
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AndrewC



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PostPosted: Sat Nov 13, 2010 2:42 am    Post subject: Reply with quote

g4lab wrote:
I recommend the fly cutter too.

If you have Harbor Freight or some similar importer of inexpensive far east tools you should be able to buy one for under $10.

I was looking at one to make holes in wood for ocular storage.

http://www.harborfreight.com/power-tools/power-accessories/adjustable-circle-cutter-37370.html


I'll try one and see - I was told a while back that the cheap ones were death traps and the cross bar could fracture or blades fly off, some come with a clear containment dome which seems a good idea.

Harold: I'd have thought a jig saw would give a worse cut than a hole saw, my experience is that they are hard to cut small radii and keep the blade perpendicular.
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AndrewC



Joined: 14 Feb 2008
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Location: Belgium

PostPosted: Sat Nov 13, 2010 2:47 am    Post subject: Reply with quote

elf wrote:
....

AndrewC wrote:

What's a flycutter hole saw - I thought flycutters were for surface finishing ? Do you mean something like this: http://www.holepro.com/drillpress.html

Andrew

That's what I was thinking of, but you should be able to find single cutter ones in any hardware store for quite a bit less.

I'm imagining you need something like this: http://www.photomacrography.net/forum/viewtopic.php?t=5660 but without the fiber optics attached.


Something like that Smile Once I've made it (or drawn it) it will be more obvious. Basically a tube clamp on a block with an A-S bevel cut into the bottom. Actually, I wonder if I can get a 52mm tube/pipe clamp ?

Doesn't a single side cutter put a lot of asymmetrical load on the drill bearings ? I seem to recall someone once telling me that you need the double side cutter for thick material to cut out a groove - one blade faces "in" and the other "out"
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elf



Joined: 18 Nov 2007
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PostPosted: Sat Nov 13, 2010 2:49 am    Post subject: Reply with quote

Flycutters are pretty easy to make as well. Here's a couple of bad snapshots of one I made a few years ago:





It's just an aluminum rod with an angled hole drilled to fit an HSS round cutting bit. The bit is just superglued in the hole. The wood counterbore part was used added later for a different sized pilot hole.
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DaveW



Joined: 04 Aug 2006
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PostPosted: Sat Nov 13, 2010 4:24 am    Post subject: Reply with quote

If its through timber, being an ex carpenter I would have used either an expansion bit or a Forstner bit.

http://sawdustmaking.com/Drill%20Bits/drill_bits.htm

Of the two I would think the Forstner bit would be preferable for holes larger than the usual run of wood bits as they can be used in a drill press.

http://www.machinemart.co.uk/shop/product/details/rpfbs16-16-piece-forstner-bit-set-14-to-21/path/augers-forstner-and-flat-wood-bit-sets

A Forstner bit will cut a flat bottomed hole, so to go right through one piece of timber you would need another piece of wood underneath to drill through into.

Even Amazon list Forstner bits in various sizes in the UK.

DaveW
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Harold Gough



Joined: 09 Mar 2008
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PostPosted: Sat Nov 13, 2010 5:33 am    Post subject: Reply with quote

DaveW wrote:
If its through timber, being an ex carpenter I would have used either an expansion bit or a Forstner bit.

http://sawdustmaking.com/Drill%20Bits/drill_bits.htm

Dave,

I have tried several times and every time IE gives up waiting for the site to open up.

Harold
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AndrewC



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PostPosted: Sat Nov 13, 2010 5:48 am    Post subject: Reply with quote

DaveW wrote:
If its through timber, being an ex carpenter I would have used either an expansion bit or a Forstner bit.

http://sawdustmaking.com/Drill%20Bits/drill_bits.htm

Of the two I would think the Forstner bit would be preferable for holes larger than the usual run of wood bits as they can be used in a drill press.

http://www.machinemart.co.uk/shop/product/details/rpfbs16-16-piece-forstner-bit-set-14-to-21/path/augers-forstner-and-flat-wood-bit-sets

A Forstner bit will cut a flat bottomed hole, so to go right through one piece of timber you would need another piece of wood underneath to drill through into.

Even Amazon list Forstner bits in various sizes in the UK.

DaveW


Forstner bits are great, I've got a selection. For some reason they tend not to be available in 52mm
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g4lab



Joined: 23 May 2008
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PostPosted: Sat Nov 13, 2010 8:20 am    Post subject: Reply with quote

I have a sturdier circle cutter than the $5 one I linked to. It only has one cutter and I have used it twice on plastic. So I don't claim to be an expert on them.

But I saw the $5 one in the store while looking for something else and was tempted to buy it because it was so cheap. It did not look like a hazardous item and it has two rather than one cutter.

I would think they come apart if you don't assemble them properly or put too much force through them.

Hole saws come in 52mm also. and Forstner bits too
http://www.woodcraft.com/Product/2080329/28215/MaxiCut-Forstner-Bit-2.aspx
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DaveW



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PostPosted: Sat Nov 13, 2010 9:54 am    Post subject: Reply with quote

Link is opening up fairly quickly for me Harold. Are you using the latest IE 8?

IE 9 is also available in Beta now, but I prefer to wait until it is in its final form:-

http://www.microsoft.com/windows/internet-explorer/default.aspx

Metric 52mm Forstner bit available as 2-1/16" Imperial?:-

http://www.total-cn.com/product/forstner-bit/FORSTNERR-BIT.htm

http://www.ptreeusa.com/forstner_bit_sets.htm

DaveW
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AndrewC



Joined: 14 Feb 2008
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PostPosted: Sat Nov 13, 2010 10:21 am    Post subject: Reply with quote

Found some larger imperial Forstners at my favourite German tool shop (www.fine-tools.com). I figure 2" will probably end up as close to 52mm once cut - otherwise I can always sand it out a bit.

I'm always curious about the difference in quality between what appear to be identical items but sometimes 5-10x difference in price when ordering from Asia. I figure as I'm not a professional it's probably worth buying cheap and so what if it only lasts a few goes. So I'll probably buy a two blade circle cutter as well - plenty on eBay for under a tenner.

Andrew
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