1/4 inch dado - Woodworking Talk - Woodworkers Forum
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post #1 of 25 Old 03-12-2015, 12:47 PM Thread Starter
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1/4 inch dado

on a few different projects I've needed a 1/4'' dado - 1/4'' deep. I've used my router table to do this but inevitably the 1/4 straight cutting bit gets too hot (i'm assuming) and breaks. I've also tried an up-cutting bit - same broken bit. I tried a 1/4 slot-cutting bit but that also gets extremely hot. in both cases the router was set to ~4,000 rpm

I could always go back to using a dado blade but it makes stop dadoes pretty clunky.

can anyone suggest an easier way to make a stop dado with a router table?

thanks in advance!
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post #2 of 25 Old 03-12-2015, 12:52 PM
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Are you cutting the dado in a single pass? I usually make several passes on the router table. I haven't broken any bits (including the 1/4 inch and the 3/32 inch for plywood drawer bottoms).

Freud and Whiteside make up most of my bits, along with a few from MLCS.
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post #3 of 25 Old 03-12-2015, 12:56 PM Thread Starter
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yes, single pass. sounds like i need to break it down to 3 or 4 ?
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post #4 of 25 Old 03-12-2015, 01:53 PM
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It could be one of several factors: feed rate (too fast), dull bit, too aggressive a cut in dense wood or any combination of these.

Those who say it cannot be done should stay out of the way of the people doing it.
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post #5 of 25 Old 03-12-2015, 03:49 PM
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Quote:
Originally Posted by jeffreysmith300 View Post
yes, single pass. sounds like i need to break it down to 3 or 4 ?
I think so. A good sharp bit is nice to work with. I built 22 drawers for our kitchen (hard maple and poplar), and fourteen for my sister in law's rent house (poplar), and 18 more on other projects (maple and poplar) and never had any trouble.

Good luck.
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post #6 of 25 Old 03-12-2015, 08:18 PM
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Quote:
Originally Posted by MT Stringer View Post
Are you cutting the dado in a single pass? I usually make several passes on the router table. I haven't broken any bits (including the 1/4 inch and the 3/32 inch for plywood drawer bottoms).

Freud and Whiteside make up most of my bits, along with a few from MLCS.
He is only doing 1/4" deep. Should be absolutely no problem.

I would guess poor quality bits.

George
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post #7 of 25 Old 03-12-2015, 08:50 PM
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Ya this seems odd...1/4 wide by 1/4 deep should be pretty easy for a good bit. The speed should be much higher than 4000 rpm...what kind of wood are you cutting?

The tools don't make the craftsman....
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post #8 of 25 Old 03-12-2015, 09:33 PM
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1/4 inch dado

I would try running the router faster. Like 20,000 rpm.
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post #9 of 25 Old 03-12-2015, 09:42 PM
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It sounds like it's building up debris causing friction. You might try a spiral bit.
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post #10 of 25 Old 03-13-2015, 12:36 PM
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I am curious to know what he is cutting also, if cutting wood are you using HHS or carbide bits. 1/4 inchX 1/4 inch should be no problem at all in most woods.

If you are popping bits there is something wrong.

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post #11 of 25 Old 03-14-2015, 12:54 PM
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Try the 1/2" shank versions.
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post #12 of 25 Old 03-14-2015, 02:11 PM
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I made the mistake of buying a hss bit once.....never again. It burned and clogged and worked terribly. Good bits make all the difference.

The tools don't make the craftsman....
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post #13 of 25 Old 03-16-2015, 09:19 AM Thread Starter
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Thanks to everyone for the responses. I'll try to answer some questions this brought up. I've tried 2 methods for cutting these grooves in both cases I'm cutting walnut and at the same rpm (about 4,000 i believe)

1. New whiteside carbide tipped slot cutting bit - 1/2'' shank - cut burnt the wood so badly, i didn't finish the first one.

2. New 1/4'' up cutting bit - first several cuts worked very nicely but after about 6 or 7 the bit just broke off.

thanks again!
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post #14 of 25 Old 03-16-2015, 10:23 AM
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If your rpm is really at 4000 then your feed rate is too fast and that's why you're snapping bits. You should be at 20,000 rpm or greater. A 1/4" router bit set for 1/4" depth should chew through walnut with no trouble at all. The bits are snapping because you are forcing the cut and applying side pressure to a bit that has nowhere to go because it can't cut the wood fast enough.

Those who say it cannot be done should stay out of the way of the people doing it.
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post #15 of 25 Old 03-16-2015, 11:10 AM
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Quote:
Originally Posted by jeffreysmith300 View Post
Thanks to everyone for the responses. I'll try to answer some questions this brought up. I've tried 2 methods for cutting these grooves in both cases I'm cutting walnut and at the same rpm (about 4,000 i believe)

1. New whiteside carbide tipped slot cutting bit - 1/2'' shank - cut burnt the wood so badly, i didn't finish the first one. we do this all day on small shaper at 8k rpm. 4 cutter or 3 cutter should work fine! check rotation.

2. New 1/4'' up cutting bit - first several cuts worked very nicely but after about 6 or 7 the bit just broke off. can't push too hard/fast on this. up your speed to 15k+ rpm.

what was the reason for 4k rpm? router bits are designed for higher rpm.

thanks again!
....
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post #16 of 25 Old 03-16-2015, 03:53 PM Thread Starter
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i don't have a specific reason for the 4k. I don't recall why my router is set there - i'll crank it up a bit and see how that goes.
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post #17 of 25 Old 03-16-2015, 07:33 PM
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Quote:
Originally Posted by jeffreysmith300
i don't have a specific reason for the 4k. I don't recall why my router is set there - i'll crank it up a bit and see how that goes.
Run it full speed. The only bits that get run any slower in my shop are larger diameter bits that probably achieve the same cutter speed at a slower rpm.
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post #18 of 25 Old 03-16-2015, 08:17 PM
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Is there any chart showing recommended surface feet per minute for various woods ?
In machining the formula is Surface Footage X 3.82 divided by the diameter of the bit.
Feed rate in inches per minute is = Chip Load ( how much each tooth of the cutter is cutting per pass) X RPM X number of teeth of the cutter.
An example in steel .
With a recommended 250 sfpm to machine tool steel ., I would run a carbide end mill at 3820rpm(250x3.82= 3820)
Charts would tell me recommended chip load so that I could calculate feed rate.
Feed rate would not be so useful as many things are hand fed by feel( in woodworking) , but I would think surface footage could come in handy.

Last edited by Tree Hugger; 03-16-2015 at 08:19 PM.
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post #19 of 25 Old 03-17-2015, 09:48 AM
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Quote:
Originally Posted by jeffreysmith300 View Post
1. New whiteside carbide tipped slot cutting bit - 1/2'' shank - cut burnt the wood so badly, i didn't finish the first one.
i would recommend that you check the rotation direction on this cutter. slot cutters would have easily cut through hardwoods, for more than one board. maybe the cutter was assembled onto the arbor facing the wron direction, 50-50 chance.
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post #20 of 25 Old 03-18-2015, 08:43 AM Thread Starter
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Unhappy

Thanks TimPa - looks like you hit the nail on head and boy am I embarrassed. The bit I'm using is a 1/2'' shank with a replaceable cutter head and in my case, I put the cutter on upside down. That certainly would explain the lousy performance! I flipped the cutter bit over - I'll give that a shot but I'm pretty sure with the blades in the right direction I'll do much better!
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