Large Forstner bits on a lathe?
1 - 16 of 16 Posts
That might be a but big. I haven't seem them that big but if you found them, I would think you would have to start much smaller and move up in size.
I would for see a problem with the drill chuck in the tail stock spinning. With that much force and torque coming from the headstock and piece of wood, it would spin the bit with the wood. You would really need to lock it in there and go really slow.
You could get a smaller, say 3" bit and cut the rest out with a chisel.
Do you want to cut out the end grain or make a natural edge bowl? What kind of wood?
I would for see a problem with the drill chuck in the tail stock spinning. With that much force and torque coming from the headstock and piece of wood, it would spin the bit with the wood. You would really need to lock it in there and go really slow.
You could get a smaller, say 3" bit and cut the rest out with a chisel.
Do you want to cut out the end grain or make a natural edge bowl? What kind of wood?
Joined
·
107 Posts
Time factor.. I have some very nice bowl gouges but would like to bore the jars out as large as possible, first.. the largest I see in a quality Forstner is about 3.5 inches
Darkmoor is a business and this will be production work
Joined
·
2,609 Posts
Have you considered metal-work style boring bars or fly cutters?
They'd require a starter hole and multiple passes, but would probably be faster than using a hand-held gouge.
Or maybe one of the many articulated-arm hollowing systems?
Joined
·
1,048 Posts
These people http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/forsbit.htm carry a 4" but chucking would present a problem. If you could remove it from the lathe and than bore on a drill press that would be ideal. You would want to run at very low rpm's.
Joined
·
4,801 Posts
You're going to spend almost as much time backing out that bit, clearing the waste, and letting the bit cool; not to mention that you'll probably have to do this at a much slower speed than you would if you just turned it.
Joined
·
107 Posts
Good info, thanks guys.. maybe a combo of Forstners followed by a bowl gouge.. bigjoe, the plan is to use 8 to 10 inch diameter sections of tree trunks with the bark left on, and end bored, for 'bark on" cookie jars, for retail sale. Have much redwood, honey locust, birch, alder curing
Also larger "bark on" redwood planters after we get the smaller process worked out
Also larger "bark on" redwood planters after we get the smaller process worked out
Joined
·
119 Posts
i hope you have a gigantic and powerful lathe, trying to use a 4" plus forstner bit takes ALOT of power.....
Joined
·
107 Posts
Joined
·
3,257 Posts
The gouge is really fast if you cut across the grain. Drill a hole 2" or so to get rid of as much of the end grain as you can down to about the depth you need to do. Then cut from the center out with a bowl gouge. I prefer to go a little deep and then cut out at an angle so I'm cutting across the grain at an angle.
The flute should be about 45 degrees or about 10:30. Make a bunch of cuts leaving the edge just a little thicker than you need. Go down about 1 1/2" or so and then cut straight down from the lip and thin this area to the final dimension. Don't go back, this area is done. Cut another inch or so and then cut down trying to blend the previous stop line. Shear scraping works well for this if your gouge technique isn't that good.
When you have about 3" left you an just go ahead and hollow it all the way and then do the last finishing cuts.
Guys who thin really large and thin pieces like lamp shades often use a really thick straight coring cutter to core out a cone shape. This makes it go faster but probably isn't necessary for what your doing.
The flute should be about 45 degrees or about 10:30. Make a bunch of cuts leaving the edge just a little thicker than you need. Go down about 1 1/2" or so and then cut straight down from the lip and thin this area to the final dimension. Don't go back, this area is done. Cut another inch or so and then cut down trying to blend the previous stop line. Shear scraping works well for this if your gouge technique isn't that good.
When you have about 3" left you an just go ahead and hollow it all the way and then do the last finishing cuts.
Guys who thin really large and thin pieces like lamp shades often use a really thick straight coring cutter to core out a cone shape. This makes it go faster but probably isn't necessary for what your doing.
Joined
·
163 Posts
Quest ..
I think that we are talking a maximum thickness of 5-6". Is that right?
If so maybe just use a Forster Bit say up to 2".
The use carbide square insert tools to widen hole say 1/4-3/8" at a time. Come straight in from the end grain. Should not take too long.
You really have to be tight at the chuck. Seems that the size of the hole would be limited by strength of the wood, how thin, does it have checks, how dry?
I have made hollow columns that 4" long and 5" diameter in such manner.
Alan
I think that we are talking a maximum thickness of 5-6". Is that right?
If so maybe just use a Forster Bit say up to 2".
The use carbide square insert tools to widen hole say 1/4-3/8" at a time. Come straight in from the end grain. Should not take too long.
You really have to be tight at the chuck. Seems that the size of the hole would be limited by strength of the wood, how thin, does it have checks, how dry?
I have made hollow columns that 4" long and 5" diameter in such manner.
Alan
Joined
·
107 Posts
You got it, just trying to speed up the process a bit.. makes sense to me, thanks
Will be relatively thick walls, solid dry woods, birch, sequoia, alder, maple, etc
Joined
·
119 Posts
Not too mention a large drill press to spin it, a harbor freight belt driven jobber wouldn't do it.....
Joined
·
107 Posts
I have a chuck fitting for the Jet lathe.. hope that will get the job done
1 - 16 of 16 Posts
Join the discussion
