Issues cutting rings on a drill press

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Gary Mac

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I've been cutting my rings from plywood on a drill press, but the cheap Chinese circle cutters don't seem to last (photo attached or my recently bent cutter), or cut that well in the first place. I'm often doing work outside the normal 38/76/98/etc steps, so custom adjustable hole sizing is nice. Does anyone have tips on finding a source of replacement or better cutters, or am I already at the best there is? I wasn't a fan as much of the router method when I tried it for the thicker plywoods in HPR. Not a fan of router kick.

https://www.amazon.com/gp/product/B073DXH972/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

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General Tool makes a better single cutter version, that has better cutters and is easier to sharpen. I use the hole cutters for my ID's only and the OD I do on a disc sander after cutting to approximate close size with a bandsaw. I have four General Tool Circle Cutters set to 54mm, 75mm, and 98mm MMT tube sizes the Harborfreight circle cutter I no longer use as its kind of sketchy/sloppy. One problem is people try and run the circle cutters at too high of speed and too much pressure. The best speed is as slow as possible for your drill press and light pressure, keep the cutters sharp.

The unit you have pictured is also a serious hand/finger hazard due to its extreme length.

https://www.amazon.com/General-Tools-55-Cutter-Adjustable/dp/B00004T7P1
 
General Tool makes a better single cutter version, that has better cutters and is easier to sharpen. I use the hole cutters for my ID's only and the OD I do on a disc sander after cutting to approximate close size with a bandsaw. I have four General Tool Circle Cutters set to 54mm, 75mm, and 98mm MMT tube sizes the Harborfreight circle cutter I no longer use as its kind of sketchy/sloppy. One problem is people try and run the circle cutters at too high of speed and too much pressure. The best speed is as slow as possible for your drill press and light pressure, keep the cutters sharp.

The unit you have pictured is also a serious hand/finger hazard due to its extreme length.

https://www.amazon.com/General-Tools-55-Cutter-Adjustable/dp/B00004T7P1
It is indeed quite terrifying to spin a 12" cutter at 300 RPM, 1" from the feed handle. It has been known to send my assistants fleeing for cover at the sight of it starting up - I won't be sad to step down to a smaller size. Thanks for the recommendation.
 
I usually use brad nails to tack the ring material to a larger board that can be clamped to the drill table....or at least get my extremities clear or the whirly bits...
I also use the tacking method when cutting narrow rings like 3" to 54mm mmt.
 
I usually use brad nails to tack the ring material to a larger board that can be clamped to the drill table....or at least get my extremities clear or the whirly bits...
I also use the tacking method when cutting narrow rings like 3" to 54mm mmt.

I use two sided tape. After cutting I slip a drywall blade between the layers and they come apart.
I don’t really like to use a fly cutter to make 4 inch or larger rings though, for the reasons mentioned. I prefer to cut the rings out just oversized, attach it to an mdf template, and use a pattern following bit in my router table to trim the new centering ring to size.
Over years I made my mdf templates by pattern following commercial centering rings.
 
I use two sided tape. After cutting I slip a drywall blade between the layers and they come apart.
I don’t really like to use a fly cutter to make 4 inch or larger rings though, for the reasons mentioned. I prefer to cut the rings out just oversized, attach it to an mdf template, and use a pattern following bit in my router table to trim the new centering ring to size.
Over years I made my mdf templates by pattern following commercial centering rings.
I do very similar but since double sided tape sometimes leaves nasty residue, I've started using blue painter's tape with CA and accelerator. Tape both the ring material and the base. Put CA on one and accelerator on the other and merge. Once done, they split with the putty knife like you're used to. This method has been used for metal-to-metal attachment in CNCs so its plenty strong and leaves virtually no residue on the wood.

I've also use my lathe to cut rings. I can spin it slower than my drill press and I use a jacobs chuck in the tailstock to hold the fly cutter. I think its safer since the wood is spinning and the cutting tool is stationary and I can advance the fly cutter very slowly and in a controlled method by turning the tailstock handle.
 
i dont think ive had a circle cutter that had the right steel used for the cutter. you are gonna want HSS. you might be able to find a local machine shop that can hook you up.
 
i dont think ive had a circle cutter that had the right steel used for the cutter. you are gonna want HSS. you might be able to find a local machine shop that can hook you up.
Good news is that its easy to grind your own cutters with the right size stock.
 
I do very similar but since double sided tape sometimes leaves nasty residue, I've started using blue painter's tape with CA and accelerator. Tape both the ring material and the base. Put CA on one and accelerator on the other and merge. Once done, they split with the putty knife like you're used to. This method has been used for metal-to-metal attachment in CNCs so its plenty strong and leaves virtually no residue on the wood.

I've also use my lathe to cut rings. I can spin it slower than my drill press and I use a jacobs chuck in the tailstock to hold the fly cutter. I think its safer since the wood is spinning and the cutting tool is stationary and I can advance the fly cutter very slowly and in a controlled method by turning the tailstock handle.

The lathe would be the best way, definitely. All you have to do then is advance the tool bit which isn’t moving fast or far.
Good tip on the tape and CA.
 
My tactic is to use holesaws and then finish up on the lathe. Those fly cutters scare me, and holesaws are much faster.
  • Drill 1/4" hole in the blank (whatever your holesaw pilot drill size may be, usually 1/4")
  • If you have a hole saw that is slightly larger than the OD, use it (drill press operation here). Otherwise cut to rough shape.
  • Clamp the blank on a 1/4" spindle - a bolt with a couple of nuts and washers works fine - and chuck it up in the lathe.
  • Turn the OD to size. Can be done on the drill press if you don't have a lathe.
  • Go back to the drill press and use another hole saw for the ID, centering it in the pilot hole
  • Enlarge the ID hole to fit properly. If you can chuck the ring OD in your lathe, you can do it very precisely. If the OD is too big for your chuck, you can just do it with a Dremel sanding drum.
 
I have been working with smaller stuff but for them I have found the step bits are very good for the inside holes for 18 and 24mm motor mount tube. You just need to be sure the ring is secure when drilling and go slow and easy. There is virtually no tear out with even the harbor freight bits... For the outside I just cut close to the line and then sand with either my sanding disk on the belt sander or by hand with a sanding stick.

-Bob
 
I too had much frustration and offset rings (long burn rings) in my attempts with the drill press...but am an ACE with bulkheads.

The cheap circle cutters wont go through craft 1/4 inch plywood well but are useful in marking a circle on it. When i can get it through it..when i drill the center it is slightly off ..it shifts .

My cheap holesaws are more of the same but i use the smaller holesaws to rough in the center hole.

After its cut i use sandpaper on a thick dowel to enlarge for mmt. After it is almost perfect ..i grab a paper template of the desired centering ring. You can slide the stock on your mmt..then add the template ..then trace the outer edge of the template with a sharpie. Then flip the stock over and do the same .

Take the stock and make the drawn ring disappear..dremmel jigsaw sanding belt ect . flip over and more of the same.

When close start checking to see if it will slide into airframe. The rings are not laser perfect but all tend to be useful and the hole is in the middle.

Have done smaller rings and bigger rings in this way. .and with a bit of practice it works .. a few of small steps instead of 2 big perfect cuts.

Another useful tool is left over tube stock if an inch long ..vent band sizing - can be used to check your sizing of rings and bulkheads without the main tube coupler or main tube falling over near your workspace..or if its chucked on a drill press..can be slid on to check size without unchucking material.

Kenny
 
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