# 1/4" shank roundover bits



## Mario (Jun 2, 2009)

Looking at the picture bellow it becomes apparent that a large diameter roundover is crucial to speakers' smooth response in the upper range. Now the problem is that I have a 1/4" router and as hard as I've been looking I could not find a roundover bit with radius larger than 1/2". I was wondering if there's a solution to this dilemma, besides getting a new router.


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## JCD (Apr 20, 2006)

Yeah, I think you might have a problem there. I suspect that the larger bits need the stronger shank. I just checked on MLCS and I found the same thing you did -- 1/4" shank only went up to 1/2".


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## Anthony (Oct 5, 2006)

You would get terrible vibration modes with a larger bit at 1/4" shank diameter. That would ultimately fatigue the bit and it would shatter (not something we want at 20000 rpm)

1/4" shank routers are usually just for trimming laminate, routing door hinge mortises, and putting small decorative edges on trim moulding and the like.

I recommend the Bosch 1617 series. They sell a kit with both fixed and plunge bases and it comes with a 3/8" and 1/2" shank. You won't have any problems finding a larger roundover with the 1/2" shank.

Good luck.


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## meniscus (Jul 13, 2006)

You may be able to achieve the same effect with a 45 degree chamfer bit, then sanding the edges for a round over effect.

Mark


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## Anthony (Oct 5, 2006)

I seem to remember someone either here or at DIYaudio who did a roundover to chamfer comparison. It was actually pretty close.


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## looneybomber (Sep 20, 2006)

If you do get a 1/2" shank, this site has a 1.25" roundover on sale for $30, along with a few other bits. I picked up a few Porter Cable bits for $5/ea, along with some other stuff. I also was able to take advantage of the free shipping over $50 purchase 

http://www.rockler.com/product.cfm?page=2127

If they would have had a 1.5" roundover, I probably would have bought two, but a 1.25" is still pretty good!


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## Mario (Jun 2, 2009)

After all I decided to buy another router. Got a used one on ebay. It's a plunge router AND accepts 1/2" bits. My old one was fixed base, so I basically killed 2 birds with one stone. However now I have a different problem. I tried to cut some holes over the weekend using a cheap 1/2" spiral bit I got at Harbor Freight and had a very unpleasant experience. The bit was overheating a lot, even burning MDF in few places. And the edges turned out very rough, like it was tearing the material rather than cutting it. Do I need to getter a better bit or is there something I'm doing wrong?


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## meniscus (Jul 13, 2006)

I can't imagine you can get a high quality carbide, spiral bit from HF. That is no doubt the problem.

A general rule for cutting - make the depth of the cut no more than the diameter of the bit. For your 1/2" bit, plunge no deeper than 1/2" on the first pass.


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## Anthony (Oct 5, 2006)

for 3/4" mdf, I do three passes with the plunge router.

Burning is a sign of dullness, and I imagine HF dulls quick. There is no substitute for good carbide. I use Bosch bits from Lowes, or Infinity bits (internet order). I also pick up bits on sale at Woodcraft, but those are usually specialty bits. For the spiral bit, go with the Bosch and make several passes. It will stay sharp for a long time.

And safety goggles. Spiral or "zing" bits are known to explode if they are worked too hard or accidentally levered during a cut. I never had one break, but a friend of mine has gone through two (no injuries, thankfully)


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## mosconiac (Jan 31, 2009)

I came up with this drawing as a result of thinking about how to create something like a 2" round for a large slot port I'll be using for a Shiva-X enclosure. With a simple tablesaw, you can get close to the round over you want in three cuts (45/60/60)...with some simple sanding to perfect it. The five cut version (45/60/60/75/75) gets incredibly close and would require very little sanding.

Even just the 60/60 cuts alone would be pretty good & might look interesting/different...


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## Mario (Jun 2, 2009)

That's an interesting technique, mosconiac. One problem I see is that it'll be hard to line up the cuts perfectly. This will take some calculations and precise tooling.


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## Anthony (Oct 5, 2006)

For setup of that type of cut, you can get artists triangles from an arts store, Michaels, or even Staples. They are plastic, and I've seen them in several angles (commonly a 45-45-90 or 30-60-90). they are cheap and make for very easy setup. Surprisingly accurate considering how little they cost.

If you organize and do all your cuts at the same time, you can minimize setup changes and do them all as a batch.

Another thing I do is always make an extra part or two to perform test cuts or router bit depth. If the target wood is expensive, I use MDF or poplar as a mock up. Simply do all the trial and error on the mockup and the final cuts usually turn out much better.


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## StereoClarity (Apr 22, 2008)

Mario, did you still need help with this? I'm in the DFW and I could give you a hand. I've got a Bosch router and it's been one of my favorite tools since I bought it. Shoot me a PM if you need some help still.


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## Mario (Jun 2, 2009)

ItalynStylion said:


> Mario, did you still need help with this? I'm in the DFW and I could give you a hand. I've got a Bosch router and it's been one of my favorite tools since I bought it. Shoot me a PM if you need some help still.


Thanks, but I recently bought a new router and a 3/4" roundover bit. these 1/2" bits are expensive. But I've already learned to spend a bit extra rather than go with cheap Chinese surrogates.


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## StereoClarity (Apr 22, 2008)

Mario said:


> Thanks, but I recently bought a new router and a 3/4" roundover bit. these 1/2" bits are expensive. But I've already learned to spend a bit extra rather than go with cheap Chinese surrogates.


Good to hear man. I spent about $200 on my Bosch router kit and never looked back. Thing runs like a champ! I think I used it for a solid two hours of nearly constant routing earlier today when I was cutting some circles.


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