Breaking router bits :(

[suraj]

Im trying to route two 1/8" wide slots in a neckthrough blank for steel reinforcements. But im a newbie at routing and have broken two bits so far. One 1/4" bit broke while routing the TR channel. And while routing the reinforcement channel I broke the 1/8" bit.

Obviously I'm doing something wrong here. But I've only been routing a maximum of 2mm-3mm per pass. I feel one of these things i'm doing are wrong -

1. I bought a single speed router that runs at 22000rpm.

2. Im probably feeding too fast, as I'm not getting any burn marks. My bit broke literally after 6 inches of a 2 mm pass..!! it was a solid carbide bit.

3. Maybe 2-3mm per pass for a 1/8 bit is too much.

4. Maybe my collet isn't as clean as it should be. The collect adapter has some rust on it but everytime i install a bit I clean the collet, the collet adapter and the bit shank with isopropyl alcohol. The bit seems to rotate without any vibration.

To give a rough figure I fed the router at maybe 12 seconds per foot. And I didn't hear any bit straining or the router bogging down or anything. Just the sound of the router running at full speed.

Please help me out

 

[Smilodon]

If you clean tools with alcohol you should add a bit of oil. Of not they will rust even more.

It sounds like you feed rate is ok, but does it sound/feel like the router is slowing down or is working hard? and can you feel any excess vibration when the bit spins freely?

How is the color of your bit? Does the parts that are bare metal change color? Does it clog with wood shavings?

 

[suraj]

Thanks for the cleaning tip. I will do that from now on.

No the router did not make any sounds of slowing down or working hard. Its a very powerful router. When I turn on the router the bit seems to spin without any vibration at all, although when I turn it off, and when the bit is slowing down, there does seem to be a VERY slight amount of play, but I feel no vibrations. As soon as the bit broke, I picked it up from the floor and it was mildly warm. not hot at all.The bit was of very good quality, brand new, and very sharp. I don't know what i'm doing wrong here.

The bit colour is the same as it was before use. The bit is not an upcut or downcut, it has two straight flutes, and while I was cutting, all the saw dust accumulated in the slot itself. Nothing was thrown out. The cut quality was very good. The bit broke off very cleanly right in the center of the cutting length.

 

[ctmullins]

3. Maybe 2-3mm per pass for a 1/8 bit is too much.

I'm putting my money on this one.

What brand bits are you buying?

What wood species are you routing?

 

[suraj]

The brand is a local Indian company called master. Well i'm sure none of you guys have heard of this, but its the most expensive bit I can find here that comes in a fancy locking acrylic box and was solid carbide. Very sharp, seemed like it was of very good quality..

 

[mikeyswood]

Solid carbide is extremely fragile. It's not your bit; it's your technique. The slightest vibration will break the bit. At that speed there is a LOT of vibration.

You want to set fences on both side of your piece so that you are passing in one direction only. You also want to make sure you're applying a LOT of down pressure to prevent vibration in the vertical direction.

I expect that you are using a low weight table. Is that correct?

 

[praisegig]

One thing that comes to mind, is how you are installing the bit into the collet. Some router bits have a radius between the cutter and the shank, and sometimes if the bit is pushed to far into the collet and tightened, the bit will work loose when cutting. SNAP. If that is the case for your bits, insert them into the collet and then pull back out about an 1/8", then tighten the nut. I use a small rubber o-ring pushed down on the shanks, to keep the collet from tightening down on that radiused area. JMHE

 

[suraj]

Solid carbide is extremely fragile. It's not your bit; it's your technique. The slightest vibration will break the bit. At that speed there is a LOT of vibration.

You want to set fences on both side of your piece so that you are passing in one direction only. You also want to make sure you're applying a LOT of down pressure to prevent vibration in the vertical direction.

I expect that you are using a low weight table. Is that correct?

I will think about setting fences on both sides, but if both sides aren't perfectly parallel, it will be difficult. BUT, I have an edge guide set up on the router, with a long straight piece of wood bolted to it, and it runs along the straight edge of the neck blank. Plus i cut only in one direction. I feel my setup is good and there seems to be no play. Maybe there is some play in the bit or collet but its not visible to my eye. According to me the bit is spinning in a stable manner with no vibrations. Im applying a LOT of down pressure as well as side pressure for the edge guide. I've even clamped stop blocks so my router hits the block and stops at each end of the channel. My table is a 20mm granite on 20mm plywood so I guess that isn't low weight at all.

One thing that comes to mind, is how you are installing the bit into the collet. Some router bits have a radius between the cutter and the shank, and sometimes if the bit is pushed to far into the collet and tightened, the bit will work loose when cutting. SNAP. If that is the case for your bits, insert them into the collet and then pull back out about an 1/8", then tighten the nut. I use a small rubber o-ring pushed down on the shanks, to keep the collet from tightening down on that radiused area. JMHE

I'm actually using a 12mm collet, with a 12mm to 8mm collet adapter. I know I should use the right collet instead but it isn't available locally. I insert the adapter flush with the top of the collet. Then I insert the bit till the shank starts tapering toward the cutters. This bit wont bottom out in the collet as its small. My 1/2" bit would bottom out, but I don't let them, I always pull out about 1/8" and then tighten. My bits are always held securely and don't loosen and fall out.



Im very confused as to what i'm doing wrong here All this makes me feel my feed speed and my depth of cut should have been lesser.

Maybe i'll try routing only 2mm per pass and feed at maybe 24seconds to a foot. Breaking another expensive bit would be pretty frustrating though

 

[Musiclogic]

Your feed rate is fine, what wood are you routing? I make 3mm deep passes in purpleheart with a 1/4" bit and have never broke one. Actually never had a bit break in my life, it may be the bits themselves. Can you order Amana bits from Israel? These are very high quality bits. I don't believe your feed rate is too fast, and you are not taking too much material, are you putting so much side force as to flex the bit to break? From what you have said, this is the only thing I can think of with what you have said.

 

[suraj]

No im just putting enough force to keep the edge guide on the neck edge. Still puzzled. Im sure its not the bits cuz ive broken two in the exact same way. I'll check again if my router collet is spinning off center..

 

[ejmy]

Are you going full depth in one pass ?

 

[suraj]

No not at all. I went to 2-3mm depth per pass. I've broken one 1/8 bit and one 1/4 bit. Both broke the same way and landed on the same place on the floor. Im pretty sure the 1/8 bit was a high quality one so i'm sure i'm doing something wrong somewhere. The 1/4 bit was a no name chinese bit. i guess i'll only realize once i break a few more bits. Wasting money on broken bits is one thing, but personally i'm terrified of a broken piece flying across the shop.

 

[iamlowsound]

It is the bit, carbon is really brittle. I use bits that are steel with carbide cutting edges.

lowsound

 

[FBB Custom]

Breaking a 1/4" bit is somewhat concerning. Carbide is brittle and 1/8" bits are rather fragile. I broke one once, cutting plywood, while taking too deep a cut. Since then I go very slowly and take very shallow passes (probably 2mm) and I have not had problems.

As I said, 1/4" bit is quite another story. I would be concerned about the router and collet setup after breaking one of those. Is there any way you can borrow a router from someone else? Can you make a very shallow cut (1mm) over a short distance on a soft wood and measure the wobble to see if you are getting more vibration than you think?

Do be careful of bits as they break loose. A face shield is not a bad idea in any case when routing, even better if there is a history of broken bits.

 

[suraj]

I couldn't get a steel bit tipped with carbide at such a small size of 1/8, so I bought carbide.

I guess I will have to inspect the router and collet setup, other than eyeballing I dont know what more I could do though. I don't know anyone near me who I could borrow a router from, but I would like to know how to measure wobble..I feel I am getting more vibration than I think as I have nothing else to compare it to, so this is possibly the explanation to why i've been breaking bits.

 

[Bruce Johnson]

A couple of thoughts for you:

I don't think I've ever seen a carbide-tipped steel router bit in 1/8" diameter. Almost all 1/8" bits are solid carbide. You can get some HSS (High Speed Steel) 1/8" bits for cheap, but they are useless for just about everything. So you're stuck with carbide. About the only choices are straight flutes or spiral flutes. Generally, spiral flute bits in small sizes will be stronger. The straight flute bits that you bought were probably intended for use in a CNC machine, where you have much better control over the feeds and position.

As far as cutting depth, I have a general rule for routing blind slots with straight bits: I never cut deeper that one half of the diameter of the bit. With a 1/4" bit, I don't go deeper than 1/8". With a 1/8" bit, I don't cut deeper than 1/16" (0.062" or 1.6mm) per pass. Overall, I think that's your problem. You are cutting too deep per pass. You're overloading the bit, and any slight physical bump or the bit loading with chips, and it will snap.

Since you're trying to inset some steel reinforcing bars, I'm assuming that you're trying to rout a pair of slots that are 1/8" wide by about 1/2" deep? In the big picture, that's a tricky job to do. With a CNC machine, it could be done with 8-10 gentle passes. With a guided hand router, it's bound to be frustrating with broken bits and hurled profanities. I personally wouldn't attempt cutting those slots with a straight router bit. I'd set up something with a saw blade, like a slitting saw blade in a milling machine, or a modified small electric saw in a sliding fixture. But those all require equipment and work.

Suggestion: Save yourself a lot of frustration and rout the slots 1/4" wide x 1/2" deep. Then lay in the bars with a thin strip of maple along side them. Routing the 1/4" slots should be easy; go with 4 passes of 1/8" deep.

Hints about the steel bars, from personal experience:

Glue them in with a good hardening epoxy like West Systems or System 3.

Wipe the preservative oil off of the steel, but then wipe them lightly with wax. You want the steel to be able to slip slightly within the hardened epoxy.

Cut the slots just a bit longer than the bars. There needs to be a small gap at either end to allow for the expansion/contraction of the wood in relation to the steel.

When the epoxy is dry, trim off the excess on the top surface of the neck carefully with a large flat file. You need the surface to be flat, and you want the top surface of the steel bars to seat solidly against the underside of the fingerboard.

I hope this helps!

 

[FBB Custom]

All of Bruce's advice is good (as usual).

In regard to measuring the wobble of the bit - I simply meant to route a slot very slowly in a softer wood, and measure how wide the slot actually is to see if there is an unacceptable amount of vibration/wobble in the router.

 

[suraj]

A couple of thoughts for you:

I don't think I've ever seen a carbide-tipped steel router bit in 1/8" diameter. Almost all 1/8" bits are solid carbide. You can get some HSS (High Speed Steel) 1/8" bits for cheap, but they are useless for just about everything. So you're stuck with carbide. About the only choices are straight flutes or spiral flutes. Generally, spiral flute bits in small sizes will be stronger. The straight flute bits that you bought were probably intended for use in a CNC machine, where you have much better control over the feeds and position.

As far as cutting depth, I have a general rule for routing blind slots with straight bits: I never cut deeper that one half of the diameter of the bit. With a 1/4" bit, I don't go deeper than 1/8". With a 1/8" bit, I don't cut deeper than 1/16" (0.062" or 1.6mm) per pass. Overall, I think that's your problem. You are cutting too deep per pass. You're overloading the bit, and any slight physical bump or the bit loading with chips, and it will snap.

Since you're trying to inset some steel reinforcing bars, I'm assuming that you're trying to rout a pair of slots that are 1/8" wide by about 1/2" deep? In the big picture, that's a tricky job to do. With a CNC machine, it could be done with 8-10 gentle passes. With a guided hand router, it's bound to be frustrating with broken bits and hurled profanities. I personally wouldn't attempt cutting those slots with a straight router bit. I'd set up something with a saw blade, like a slitting saw blade in a milling machine, or a modified small electric saw in a sliding fixture. But those all require equipment and work.

Suggestion: Save yourself a lot of frustration and rout the slots 1/4" wide x 1/2" deep. Then lay in the bars with a thin strip of maple along side them. Routing the 1/4" slots should be easy; go with 4 passes of 1/8" deep.

Hints about the steel bars, from personal experience:

Glue them in with a good hardening epoxy like West Systems or System 3.

Wipe the preservative oil off of the steel, but then wipe them lightly with wax. You want the steel to be able to slip slightly within the hardened epoxy.

Cut the slots just a bit longer than the bars. There needs to be a small gap at either end to allow for the expansion/contraction of the wood in relation to the steel.

When the epoxy is dry, trim off the excess on the top surface of the neck carefully with a large flat file. You need the surface to be flat, and you want the top surface of the steel bars to seat solidly against the underside of the fingerboard.

I hope this helps!

Firstly thank you so much for giving advice on glueing the steel rods. That just saved another thread and a couple of other questions

My routing depth is actually only 1/4, not 1/2 so I guess I could take 4-5 light pass with the 1/8 bit, OR I could use my 4" circular saw, and saw out the slot almost to the final depth, using a guide, then make the final pass with the 1/8 bit, along with a couple of passes, at the ends where the radius of the 4" circular saw needs to be removed.

I guess with patience and light passes I could get the job done, but if that doesnt work out, I would take your advice and route a 1/4 wide by 1/4 deep channel and glue a 1/8 strip of maple or wenge.

All of Bruce's advice is good (as usual).

In regard to measuring the wobble of the bit - I simply meant to route a slot very slowly in a softer wood, and measure how wide the slot actually is to see if there is an unacceptable amount of vibration/wobble in the router.

I misunderstood your last post and thought, it cant be that easy

I guess i've already done what your telling me to do. When I was routing the 1/4 channel for the TR, my first pass was a 0.5mm pass just to see if the channel is centered in the neck and if the width of the channel matches with the TR. It was a perfectly snug fit. Even after I routed the channel to the right depth, the TR fit snugly. Also I measured the slot with my calipers, the slot was 6.55mm in width, So I guess I have hardly any noticeable or measurable wobble. Hope that makes sense.

 

[Smilodon]

<snip!>

I guess i've already done what your telling me to do. When I was routing the 1/4 channel for the TR, my first pass was a 0.5mm pass just to see if the channel is centered in the neck and if the width of the channel matches with the TR. It was a perfectly snug fit. Even after I routed the channel to the right depth, the TR fit snugly. Also I measured the slot with my calipers, the slot was 6.55mm in width, So I guess I have hardly any noticeable or measurable wobble. Hope that makes sense.

Actually, that is too wide if your bit really is 1/4". Measure your bit and see how wide it really is. It could be a perfect match, but if the bit is exactly 1/4" you have 0.2mm wobble. I have no idea if that is acceptable or not, though...