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Large Forstner bits (55mm plus)

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Spectric

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Only having used a lathe for metal work is there not a woodworking equivalent of the boring bar?
 

Gerard Scanlan

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A German or Swiss forstner bit that size with set you back in excess of 100 quid.
If you are going to be using it a lot (weekly for years) they are your best bet.
However if it is for hobby or incidental use it might be worth trying a carbide tip model ordered direct from China. I have compared Famag Bormax (supplied by Workshop Heaven) and Chinese Carbide tip models (direct from China). The carbide tip models are better for deep cutting. The Famag work better on thin material. But both are excellent. I use 50 and 60 mm carbide forstner bits on my lathe and they work very well. But I have not made holes deeper than 100mm (length of the shaft limits the depth).

Hope this helps
 

Stevekane

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Please forgive my complete ignorance but if I found myself haveing to drill a hole nearly 3ins wide and 10inches deep and I had access to a lathe I think I might try sharpening up the teeth on a Core Drill and seeing if with a bit of force and a lot of clearing if it would drill through, if its softwood you maybe stand a chance but if its dense stuff like MDF it probably wouldn't work,,,
Steve
 

Wood&StuffLtd

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I regularly drill holes, mainly in softwood turned vases up to 25cm deep and 6cm dia, by working up to that size by progressively boring out using augers and forstner bits on an extension piece fixed with a keyless chuck on the tail stock. I drill at around 400rpm. I use beeswax on the bit and vacuum out any debris each time. Seems to work ok.
 

KT -andy

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I've been using a cheapo carbide 75mm one , just on soft wood . Deepest I've got so far is about 6" .
no small one first - just straight in with the fat lad !

I tried the saw toothed Forstner bits - didn't work very well .
Holesaw was a waste of time .
 
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Snailman

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I have two 75mm or slightly bigger Forstner bits I bought from Wealden Tool Company many moons ago for boring into green oak posts, unfortunatley they no longer supply that size.
I use them in a very large industrial drill press on a slow speed feed rate, I did have to get the sides of the shank flattened off to stop the bit spinning in the chuck. From memory I only go 200mm deep but it does stay straight.
Have also had cheapo ones from fleabay at a slightly reduced size, you need to keep on top of the sharpening but they work fine.

8" x 8" oak post
IMG_192471686432043.jpeg


Fred
 

Duncan A

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No idea if this would work, but worth considering for £63:
.
I notice that it has a hex shank so less chance of slipping in the chuck.
115mm effective depth plus quill/chuck length would possibly do the job without using an extension althoug quite a lot of faffing about to withdraw it for chip clearance.
Duncan
 

Mike foulkes

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Hi there,
I am looking for a quality forstner bit with a 70mm diameter. I know Fisch do them, but i cannot find any company in the uk that supplies that size. Anyone out there know where I could get this, without going into Europe.
obviously I could use a smaller bit and then hollow out the rest, but I need to go about 250mm deep.
Thanks, Dirk
Have you tried Axminster tools.
 

sometimewoodworker

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Hole saws are limited by their depth, mine all tend to smoke a lot too... Need new ones
30 mm to 70 mm with a 350 mm depth of cut are reasonably easy to find and not expensive, they are designed for cutting concrete so will have no problem with wood they are designed to be used in an SDS drill but can be modified if needed. You will need to break out the core at regular intervals
E8ED5BB4-1312-44CA-86C7-CF6D15AF0422.jpeg
 

Adam Pinson

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30 mm to 70 mm with a 350 mm depth of cut are reasonably easy to find and not expensive, they are designed for cutting concrete so will have no problem with wood they are designed to be used in an SDS drill but can be modified if needed. You will need to break out the core at regular intervals
View attachment 107454
These look pretty sturdy
 

sometimewoodworker

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These look pretty sturdy
They are, the grind on the carbide is not optimised for cutting wood but they will certainly do it, though you will probably be backing them out for chip clearance often. You might be better off with the Bosch or Lenox saws with an extension bar. I didn’t get the 70mm as I only need the 35mm & 50mm ones. They cost about £15
BF80244E-5CAF-4CF8-B1F9-6A14B81F3A52.jpeg
A7E0CD56-FFFD-4847-8195-37E27AE2EB49.jpeg
 

Adam Pinson

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They are, the grind on the carbide is not optimised for cutting wood but they will certainly do it, though you will probably be backing them out for chip clearance often. You might be better off with the Bosch or Lenox saws with an extension bar. I didn’t get the 70mm as I only need the 35mm & 50mm ones. They cost about £15
View attachment 107462View attachment 107463
I think a combination of this product and my DVR motor is a winning team, journey to the centre of the earth....... How clean is the cut I wonder?
 

minilathe22

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I have found with 50mm+ forstner bits, you may find the bit spins in the chuck unless it is a good one, and you may also find the chuck taper spinning in the tailstock. I have a 70mm and 100mm forstner bits that I regularly use, but I have to really hit the chuck into the taper with wood/rubber mallet for it to stay put. This is an MT3 taper.

The 100mm one was only £7 from China, and has lasted suprisingly well. It has a hex shank which I think is useful. The 70mm one I have, has a round shank and I have to make sure the chuck is very tight.

If you can cut the wood while its recently felled and still wet, you will have a much easier task.
 

Johnny65

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I have made bird nesting boxes out of 5 to 6 inch dia logs, I bore them out 200mm deep.
1st tool 20mm twist drill.
2nd tool 60mm forstner bit.
3rd tool 100mm forstner bit.
Takes time and a bit of backing off and cleaning out but not had a problem, done on a Coronet Herald.

Cheers John.
 

Adam W.

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Should have asked someone who deals with the larger bits of treewood.........

Milwaukee self feed bits, 116mm Ø big enough for you ?

They also do a 76mm one for the little boys, but you need a hefty, high torque, slow speed drill with a loooooong handle and a wall to brace it against. They have a hex shank, so it's you who'll do the turning so make sure your thumbs are rally driver style, as they may get broken.

Not sure if my V300 will handle it though and as I have the drill and the the large solid object to brace it against (a house) I won't be trying, because I like my lathe too much.

 
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