Last Phase of Hollowing Rig

[Dan Mosley]

Today i fiinished up the little things and tried the rig out on a much larger pc of olive wood. I took off the safety stops and wired up the laser to test it out (5 volt laser from Laser Land). The log is 15" long and 12 1/2" wide.
I drilled a deep hole with a old bit I had by welding in a pc of drill rod.

I hollowed as usual by hand for awhile and then setup the rig as shown in the pictures below (pictures 1-4) . It cut great until i got about 2/3 of the way into it and then it started acting very jerky. I tried raising up the tool rest but it didn't seem to work and then tried rotating the cutting tip down slightly - didn;t help either... I had to reposition the cutter several times due to the jerking tork that the tool was getting.
What im wondering is if I should have made the cutting tips so they just solidly mount into the 3/4" round bars instead of the adjustable one ive been using (picture 5). Like taking the bar steel and putting a 45' hole in it with a set screw to hold the cutter and I could do the same for a straight tool...........thoughts ??
Anybody have any other ideas ????

thanks Dan

 

[john lucas]

Dan It looks like a 3/4" bar. Mine starts to chatter about 12" in and that's with a solid bit locked in place with a set screw. I find the direction of the cut has a large affect on the amount of chatter. Still I did a vessel that I turned 16" deep so I could cut off the last inch. I really fought the chatter that deep. I think a 1" bar would be better at that depth.

 

[Mark Mandell]

Dan,

For boring bars, the general rule is the bar's reach is limited to 15 times its diameter. Your 3/4" bar will be overcome by the leverage beyond 12" which is about what you've described. If I go to 15-16" depth, I'm mounting a 1" bar. I also have a 1-1/4" and 1-1/2" bar to fit my Kobra's mount. The Kobra system design will handle more vibration than your Sudol/Jamieson clone arrested "D" rig, but even so, I switch out the bars sooner to get better, more easily controlled cuts.

I suggest that you get some heavier bar stock; O-1 drill stock from ENCO is fine, then have a bit of machining done to fit your D's socket and to hold your cutters on the working end.

 

[Dan Mosley]

John....Mark............yeah im going to get a pc of 1" round cold rolled steel in a few days when im off. If I remove the adapter on the front of the D-arm that is holding the 3/4" goose neck in the picture then the 1 1/4" square tubing will accept a 1" round nicely. I tried it with a pc of scrap and it will work well.
Im thinking i can heat it up in a vice and put a bend in it - drill a hole in the tip of it to hold a 3/16 HSS bit - then tap a screw hole to secure it.
Anyway, making it with the tip secured in a bored hole sounds like a stronger way to attach it......It will probably work better than the rotational tip I made on the one in the picture.

Thanks Dan

 

[Mark Mandell]

Hi Dan,

If you're going to try bending the 1" bar, make it easier on yourself.

Get stock that's 6" longer than you will actually need, and do your hot bend before you drill. The extra length is used on the end to be bent to give you stock to clamp in the vice and leverage to bend with an even curve. Once you have the curve set, carefully anneal the steel, then cut off the excess, and lastly drill your cutter holes. If you drill first, the bending process will deform the holes and you'll have to ream them back to round.

I also drill my boring bar ends a bit off-center and then use the heavy side for the set screw; gives a more positive fixing and doesn't compromise strength. Tapering the bar ends back about 1/2 - 3/4" will give better clearance from the cut-face of the wood. The attached photo is of my 3/4" bar with bent holder for a Hunter #4.

As an alternative to bending the big bar, you can simply end-drill it to accept tool holders (as I did in the picture). Short lengths of 1/2" or 5/8" rod and a 3/8 or 1/2" bore in the big bar work quite well. Also easier and cheaper than having several profiles in 1" or above bar stock.

Hope this helps

 

[john lucas]

do you really need a 1" bent bar. Usually you use the bent bars for the 1st 1/3 of the vessel. After that I use a straight bar.

 

[Dan Mosley]

John - I see what you mean about using the bent for the upper portion of the vessel and near the top lip area. I am going to try just using the straight like your saying and would be easier to make also