Amen to that. Every tool is dangerous if used wrong.
Centering Rings
- Thread starter David Schwantz
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lakeroadster
When in doubt... build hell-for-stout!
rharshberger
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Neither did routers, or table saws but both can be dangerous tools in the shop/worksite.
lakeroadster
When in doubt... build hell-for-stout!
Tools are NOT dangerous. It is the operator that IS !
The list, for what it's worth, is by number of incidents. Lots more people use ladders, lawn mowers, and hammers than fly cutters and table saws. Injuries per use (by hours or by tasks) would tell a different story.
And, since David is absolutely right, the story it would tell is of which tools are most easily misused or often used by people who only think they know what they're doing.
And, since David is absolutely right, the story it would tell is of which tools are most easily misused or often used by people who only think they know what they're doing.
back in the high school vocational school days they showed us a film in wood shop that was a typical Hollywood production but it showed a guy pushing a board through a table saw and had a kick back and then it showed the guy with the lumber basically stuck halfway out his backside, you know with lots of blood and so none of us wanted to go anywhere near the table saw after seeing that film. 
My father bought me a table small saw many years ago, and told me that for his sake I should be careful, because he didn't want to be the one who had to tell my wife I'd cut a finger off. He also said the saw is safe to use as long as you're just a little nervous each time. Not terrified, but just that little bit nervous.
rharshberger
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Actually lack of understanding of what can go wrong with certain tools is what leads to many accidents. An experience wood worker learns to read the grain of a board to get some idea of how the wood and the saw will interact, a tool is a tool.
rharshberger
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I have a very healthy respect for what my 5hp Grizzly Cabinet Tablesaw is capable of....
Many years ago I learned a lesson with my newly acquired radial arm saw. I forgot to utilize the ant kickback device when doing a rip cut. The material came flying out just over my shoulder, missing my face by inches. Whew, close call!
lakeroadster
When in doubt... build hell-for-stout!
rharshberger
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Thats great for general circles but for centering rings which need to be very precisely fitted there is still a lot more work to be done.
bobbyg23
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This is what I do for centering rings. Works perfectly with minimal work to be done afterwards.
bobbyg23
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Mine fit better than most I get from rocket manufacturers
I usually 3D print mine (although I have a CNC, plywood is more expensive than filament)
rharshberger
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They should fit better, you can finesse them to a perfect fit, rocketry manufacturers tend to make them a bit under on the OD and a bit over on the ID so they slide on/in easier otherwise people whine about how much work they have to do to make them fit. I no longer use flycutters, and the bandsaw or scrollsaw only for rough work, router templates make almost perfect rings straight off the router table.
rharshberger
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Maybe what you are buying but 1/4" baltic birch from my supplier is about $25 per sheet and it makes lot of centering rings from a 60"x60" sheet. See if you can buy from a local cabinet shop, they use lots of 1/4' baltic aka 6mm for cabinet drawer bottoms and the like.
I've done a bunch like that lately. Pretty dang quick. Hole saw in the center hole with arbor after cutting out on the saw and it's literally a couple minutes of work to have a centering ring if your measurements and/or template is good.
I've found with the blade I am running now, anything less than 2.5" diameter can be a bit tough, may look for a smaller blade.
Ah... the number of cabinets that I have thrown away that I could have broken down for plywood... My house would look like Sanford & Son Salvage if my wife would let me keep everything. I have managed to keep all the acrylic sheets from old storm windows / doors. I need a 3-car garage or a barn...
Seriously though - I am all low powered right now so would use something smaller. It is hard to compete with cost and on-demand aspect of 3D printing for these for a low-powered rocket (not sure about durability of these ABS prints on a high-powered rocket). The frame centering ring above for a BT-80 tube is $.09 in filament the solid one with motor mount integrated (actually that one is made to mount a BT-50 tube / 24mm motor mount tube) costs $.24 in filament.
EDIT: I guess as I am calculating this the 2mm plywood I am buying is around $1.50 per sheet for a 200x300mm sheet so I could cut around 11 BT-80 centering rings from one sheet so still not too bad (and would be lighter than the 3D prints).
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For low power ... sandwich 2 pieces of cracker box glued together at 90 degrees and cut with xacto knife. Pattern from OR or Rocksim.
That's very nice for bulkheads, but how do you cut the inside hole dead-on center?
(OK, I see a way. I'll reveal it later, after hearing others' answers.)
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bobbyg23
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Drill bit through the center hole. Easy peasy
Or a hole saw. But hole saws tend to be sloppy.
bobbyg23
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I use a nice forsner bit.
lakeroadster
When in doubt... build hell-for-stout!
What tool you use is based on what thickness material you are cutting through... and what type of material the centering ring is.
The thicker / more durable the material... the easier it is to cut. But if we're talking about lpr, and basswood or balsa, not destroying the ring is the tricky part.
The reason I bring this up is.......
Please, tell us more. What diameter drill bit are you referring to? A BT-50 would need a 1" drill bit. If you're using a standard 1" twist style drill bit to make a centering ring it will destroy a thin LPR centering ring.
Even a forstner bit will destroy thin basswood / balsa.
Removing a minimal amount of material, like using a fly cutter, band saw or scroll saw, works best in regard to not destroying the delicate lpr ring material..
The thicker / more durable the material... the easier it is to cut. But if we're talking about lpr, and basswood or balsa, not destroying the ring is the tricky part.
The reason I bring this up is.......
Please, tell us more. What diameter drill bit are you referring to? A BT-50 would need a 1" drill bit. If you're using a standard 1" twist style drill bit to make a centering ring it will destroy a thin LPR centering ring.
Even a forstner bit will destroy thin basswood / balsa.
Removing a minimal amount of material, like using a fly cutter, band saw or scroll saw, works best in regard to not destroying the delicate lpr ring material..
bobbyg23
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I am usually making 4" of with 38mm or 54mm motor tube holes.
lakeroadster
When in doubt... build hell-for-stout!
So your making a 4" thick stack of centering rings?
bobbyg23
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Autocorrect bit me again. 4" od. For 4" body tubes with 38mm or 54mm center holes for motor tubes.
