I am a woodworker and have used hole saws on my drill press for some time. Has anyone sized or located hole saws that will cut to the diameters needed … such as 29 mm for an engine mount tube.
Hole saw for centering rings
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Here's what I use. 1 3/16" for the 29mm tubes and 1 5/8" for 38mm tubes. You'll notice shortened teeth on the larger bit. I found it was just a bit too wide. The teeth that splay outward, once eliminated, make it cut just a bit smaller. Now tubes fit perfectly in the CRs.
A lot of us use fly cutters, adjustable hole saws that have a sliding bit on an arm.
Guys, thank you both.
Once upon a time, probably 20 years ago, I started to put together a sheet to show what size Forstner bits to use for each size of PML/Giant Leap or LOC tubing. I never got very far and have upgraded computers multiple times since.
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Instead of hole saws invest in a Jasper jig for a router and get a 3/16" and 1/4" spiral fluted upcut bits. I cut centering rings for years with this setup before I bought a laser cutter.
I use my router with Jasper circle-cutting jigs for cutting inside and outside circles. They give you 1/16" steps for the cut diameter with a single 1/4" router bit. You can cut other diameters by adjusting the router bit diameter. I usually just sand for the final fit.
https://www.amazon.com/Jasper-400J-Router-Circle-Cutting/dp/B00009K77Dhttps://www.amazon.com/Jasper-200J-Circle-Cutting-Plunge/dp/B00009K77A
https://www.amazon.com/Jasper-400J-Router-Circle-Cutting/dp/B00009K77Dhttps://www.amazon.com/Jasper-200J-Circle-Cutting-Plunge/dp/B00009K77A
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JimByrne
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I use hole saws to make centering rings and e-bay caps all the time.
Most of the time I go a little oversize with the O.D. (no better choice) then put them in the lathe and trim to fit.
Most of the time I go a little oversize with the O.D. (no better choice) then put them in the lathe and trim to fit.
You mentioned you do woodworking -- Why not add a CNC to your tools?
rharshberger
Well-Known Member
I use hole saws to get "close enough" and then use 3d printed router patterns with a flush trim bearing bit to make them perfect on my router table.
Indeed. That’s the only way to fly and is infinitely adjustable.
Thanks for that tip!
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I like the Jasper Jig recommendations for sure - great for doing lots of stuff. You can make a rocket specific router base similar in concept if interested, as its not too hard.
I'm not generally a fan of hole saws. Another option is a jig to cut circles using a bandsaw, although I've never done that.
No question, a laser does make things quite a bit easier, even if it just making the jigs. Lots of amazing stuff has been done with hand made jigs and that is a super valid path to follow, probably one of the things that makes me happier than using the laser.
Sandy.
lakeroadster
When in doubt... build hell-for-stout!
Money? Space? Witchcraft?
You can cut centering rings or bulkheads slightly oversize with a holesaw and then use a short piece of threaded 1/4-20 rod as a mandrel to hold the centering ring with nuts on either side. Then you can chuck that mandrel in the drill press or battery drill and use sandpaper to size the OD of the centering ring down to the correct fit.
Money? Space? Witchcraft?
Fair enough -- but there is a huge community of entrepreneurs who make a ton of $$$ from their CNC machines (and many woodworking shops are somewhat centered on them these days) -- that is why I asked.
If someone is not that committed, even a really cheap ($200) CNC can cut centering rings and fins (from wood as well as other high-power-appropriate materials).
I've got a box of Sarrett hole saws ranging from 5/8" to 4", about 30 of them that I'll likely never use again as I have no room for a drill press.
lakeroadster
When in doubt... build hell-for-stout!
How many centering rings can you buy for $200? Point being if rocketry is your hobby, there are many other methods that are much more cost effective.
lakeroadster
When in doubt... build hell-for-stout!
I've got a box of Sarrett hole saws ranging from 5/8" to 4", about 30 of them that I'll likely never use again as I have no room for a drill press.
They make a table top drill press that you fasten a drill into. The foot print takes up less space than a piece of paper.
Drill Press Stand for Hand Drill
All of the above,Money? Space? Witchcraft?
Actually, you said a cheap cbc can be had for $200. That I would consider.
I bought this one:
https://www.amazon.com/Genmitsu-3018-PRO-Control-Engraving-300x180x45mm/dp/B07P6K9BL3/
I have cut hundreds of sheets of 1.5-2mm plywood for rocket fins and been happy with the result. It would have no issue with 1/8" plywood (I usually cut 2x 2mm sheets stacked) and should do carbon fiber sheets as well (mask required I think). I bought the 3040 upgrade kit to give me a 300x400mm bed so that it was easy to mount the 200x300mm stock I buy. There are much better CNC's out there but this one has kept me quite happy and has transformed my experience designing and cutting rocket fins.
Here is the 3040 upgrade:
https://www.amazon.com/Genmitsu-Extension-Accessories-Compatible-3018-PRO/dp/B08RYGQ28W/
lakeroadster
When in doubt... build hell-for-stout!
I have used hole saws to rough out the diameter, then used my wood lathe to turn the rings to size. The actual body tubes can be used as fitment gauges.
More here.
That's all well and good for the inner hole, but none of the Forstners I've seen could cut the OD and leave the ring or bulkhead. With hole saws, one should be able to secure the stock with double sided tape, cut one diameter, then switch bits and cut the other. Leave the outer a little big and the inner a little small so that you can come to final dimensions by whatever means you have available: lathe, sand paper, or something in between.
You’re absolutely right. I got ambitious and overly optimistic for a while so whenever I bought a kit with new sized centering rings (new for me) I used a template following bit on a router table and made one copy of each size centering ring out of MDF. The plan was that I could use that as a pattern to make more out of whatever material I wanted. Ultimately I became a victim of my own laziness though and now I just order extra rings as needed.
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BigMacDaddy, really? Cause this has me VERY intrigued. I cut balsa, basswood, and up to 1/4 inch (but mostly 1/8th or 3/16ths) lite ply or plywood.
I do this mostly by hand using a table top bandsaw and table top 6 inch sander.
This will do the job? Centering rings and fins? I thought of maybe a laser cutter head for a 3D printer... but this might work on thin FG as well (???)
It will definitely do the job. I leave tabs to hold the pieces together but you can also use blue tape and crazy glue or other methods. For me cutting tabs is not difficult. It was critical to upgrade to 3040 for me to be able to cut 200x300mm sheets of plywood which are pretty cheap per sheet (like $1.25-$1.50 per sheet). If someone has a business doing woodworking or similar I would recommend a higher-end CNC -- for $2000 or so you can get a much better unit with a bigger bed.
A laser cutter will also do the job and can be faster / reduce the need for clamps / hold-downs and larger tabs. However, diode lasers (the style you attach to the gantry directly) are pretty underpowered for cutting. A K40 laser will apparently cut thinply like butter (I am working to get mine setup now) but relies on a big laser tube so moves mirrors around on the gantry to redirect the laser beam. K40 lasers are not that expensive either (I have no experience with this one but came across it recently): https://www.amazon.com/OMTech-Engraver-Desktop-Engraving-Detachable/dp/B099KK2HGH/ (although you will need to purchase water pump, air pump, vent tube, etc...).
The CNC is loud and makes lots of dust (I have not fit a dust shoe yet) but the laser needs to be vented to outside and can cause fires so needs to be monitored all the time (i.e., you need to be next to it and paying attention). If I am cutting a couple of sheets of 2mm with dozens of small fins it might take 30 or even 40 minutes for the CNC but I can just walk away and do something else. Simpler fin setups take 10-15 minutes or even less. The CNC can also do other materials -- like carbon fiber or fiberglass (although enclosure, mask, and ventilation may become necessary with other materials) and can be used to make airfoils or otherwise bevel thicker material. A laser can make cleaner cuts as well -- CNC leaves some fuzzies that are easily sanded away unless your bit is brand new.
For me cutting fins was pretty annoying and stressful (particularly since I moved over to plywood long before I got my CNC) and curved shapes were a nightmare. Having a CNC has really changed how I design rockets. I like the reproducibility -- I like to design something and be able to reproduce that design repeatedly (or modify and make again without starting from scratch).
Here are some pics of my CNC and the fins I make with it.
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You may have convinced me... the link you sent + the expansion? Will I need bits? Or ???? BTW: That looks like the Centaurus from ... oh what was the name of the company...??? I have it and the Swarm still in the boxes.
I will refer to those by several names. One name resembles a Christmas decoration but cannot be used on the forum. The fly cutter earned it when it flew off and almost hit me in the groin. The other is the flying wheel of death.
If you use one for this purpose, ensure the grub screw is tight.
