My 80mm diameter Oertli spiral insert cutter likes 9000 minimum. Anything less does not feel right. I think the one I have is designed for CNC routers. Cutter says max rpm 12000.
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My 80mm diameter Oertli spiral insert cutter likes 9000 minimum. Anything less does not feel right. I think the one I have is designed for CNC routers. Cutter says max rpm 12000.
[OP]
Member
Ok, so I got a 3" dia x 4" tall byrd cutter with a pilot bearing. I was making my second cut of several pattern cut curved pieces as illustrated in my crude drawing. It was cutting like butter....then wham! The cutter grabbed and kicked back, nearly sending the piece through a block wall. The pieces were 3" tall, about 18" long curly maple, and rather thin, about 1/2" at the thin end, 1" at the other end. The pieces fit solidly in the jig, and were secured with destaco clamps. The force broke the stop block off the jig, and the jig was heavy enough that I didnt even feel it when it happened. This is the first shaper incident I have ever experienced. I'd feel a lot better if I knew what I did wrong.
shaper.jpg
Member
Sounds to me like you're taking too deep a pass? How much stock are you removing? I remove all but 1/16 to 1/8 material with a band saw. I tried leaving a bit more and things got scary.
-Lud
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JIm
If I'm looking at it correctly, it would appear that you began to cut into the grain and "caught" the grain as you were shaping the curved section.
If the curve is sweeping like in the pic, and you were feeding right to left, the curved portion should have been the first to meet the cutter, not last. This way you are cutting with the grain throughout the curve.
Just a thought.
"The first thing you need to know, will likely be the last thing you learn." (Unknown)
[OP]
Member
Originally Posted by Justin Ludwig
Lud, yes, I was probably taking 1/4" cut, but it was cutting like butter, and my feed-rate was pretty slow.
Mike, I began the cut in the middle of the board, going right to left, then I flipped the cutter and was finishing the cut left to right. I was about 3" from finishing the cut.
PS. Did notice that there is a broken tooth on the cutter head. Could have happened when the piece kicked back, but what if it broke while cutting and caused the incident?!?!
Last edited by jim mills; 05-24-2015 at 11:18 AM.
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Jim, what RPM? Mine is a different brand but like I said does not like less than 9000. I have also found this head does not like 1/4" on thick work. We usually go 1/8" over our normal 1/4" for our other cutters.
1/2" is pretty thin on the one end and at that height the Destaco might not be enough. That thin, the shaper jig may need a full height piece where the back of the workpiece is. Can you leave the workpiece long and catch it with screws into the backer? Carefully countersunk to avoid the cutter. Possibly a shim spacer on the jig to make the cut in a couple passes.
We normally cut one direction with this head and I would go from the thick end to the thin. But I have never used it on curly maple.
Just some ideas. with small pieces it is all about supporting the work.
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Curly maple that has been carefully picked is big loss if ruined. Again I mention the old spring hold downs that all shops,around here,used to have. Guess they just are not high tech enough now. With one,I would use traditional collars or corg heads with M2 or T1 and safely climb cut.
[OP]
Member
Joe, 9000 RPM. The work WAS supported full height, and with four destaco's. I was wondering if the workpiece could have began to chatter towards the thin end, causing the cutter to grab. I just dont remember that happening.
Ruined? It's a pile of splinters at this point. We've gone over if for hours now. Two of us were feeding it slowly, the cut felt good, then WHAM...
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One thing that helps on a square cut is rounding the top and bottom sharp corners before making the shaper run,either with a router 1/4 inch round over used climb cutting or an orbital sander. Used to be done often, some one here tried it recently and reported it worked. After the initial rounding ,the finish cut will usually work fine with standard forward cut.
Last edited by Mel Fulks; 05-24-2015 at 2:58 PM. Reason: clarity
Contributor
Jim,
At this point I can only suggest light cuts. Maybe 1/16" at a time. With that type cutter and 3" thick 1/4" removal is a lot.
We have shaped a lot of work that thick with ours but never that thin.
Member
Sounds to me like the material got loose and started chatter, there are so many teeth in play on these things that an over feed happens way to quick to keep track of. Do you have any sandpaper on the bottom of the jig, opposite side of the destaco's? That can help give a little traction. When ever possible I go with Joe's suggestion to leave things a bit long and leave a place at each end in the waste for a solid connection with a fastener. Destaco's are great, screws are better. Short of that perhaps a vacuum clamp would keep the 1/2" material from fluttering? Complicates the jig, sure would be cool though! I did hundreds of small curved bars for radius doors last summer, had a few leave the jig.....by the 3rd one I figured out a solution, never got any less scary. I've taken out a 1/4" heavy before by keeping the template off the bearing a bit, shaving an 1/8 on the first pass then going again. You need to be somewhat cooridanated and somewhat stupid to try this as a bobble could turn into a climb cut, you don't want that. Better solution is to get a second bearing that is bigger than the cutter by 1/4" in diameter and use that to do the first pass. Last place I worked had the in 1/16" increments from 2" through 4 1/2", expensive but handy.
Last edited by Peter Quinn; 05-24-2015 at 4:55 PM.
"A good miter set up is like yoga pants: it makes everyone's butts look good." Prashun Patel
Contributor
All the suggestions so far are good- decrease the cut by pre-sawing, increase the blank length and screw it to the jig, add sandpaper to the jig base, increase the rpm, use the powerfeed if possible, use graduated bearings or adjustable rub collar to limit cut depth, use shims to make the cut in several passes in height. Two further thoughts: can you increase the blank width by shaping it from a larger piece and sawing off the excess (or temporarily adding a low value chunk to the blank with a glued joint)? and do you have a backstop to intercept flying blanks before they hit the wall or any personnel in the way? If none of the above works, you may want to consider outsourcing to a competent cnc operator. No guarantees there, but at least the kickbacks happen in someone else's shop. This is a tall cut in a thin piece-lots of cutting surface relative to available traction.
Member
Interesting thread since I had the exact same issue a while back working with figured maple, in fact it ruined the whole workpiece. I bought a Sanding drum with matching bearing and that solved the problem right there and felt much safer.
[OP]
Member
Thanks for all the suggestions. I still have this wierd feeling about the broken tooth, but i may just still be in denial. I dont mind admitting when i make a mistake, but i just wish i knew what it was. i'll do what i can to secure the board better, and do what it takes to take a lighter bite. I like the idea of over sized bearings.
Member
What you did was use the wrong tool machine for the job. secondly you made no risk assessment if something went wrong. If you get any more than 2 to 3 inches around of any cutter(including chip limiting) in a tall cut it will pull you in. This should never have been hand feed and only then with special fixture with full support and wood of a less figured nature. All after a risk assessment is done .
here is how i deal with pattern shaping delicate large/tall work with a lot less brown in the trousers.
Last edited by jack forsberg; 05-25-2015 at 9:47 AM.
jack
English machines
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