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Discussion Starter · #1 ·
New user (and pretty new to woodworking) here....

I was trying to cut a 1/4" wide and 3/16" deep groove into a piece of purpleheart using a new Freud 1/4" Up Spiral Bit (75-102).

After a couple of test passes in pine to check depth and distance from fence, I attempted the cut into the purpleheart. I didn't get more than 1/2" into the pass when I heard a crack and the stock shook violently. I quickly turned off the router and first inspected the wood as I thought something happened there -- of course, it was damaged (looked like a drill hole that wandered a quarter inch) but couldn't understand why until I looked at the router bit. It was cut off at the collet! Looking around, I found the top of the bit along with a small cracked bit near/under my compact router table.

I know bigger router bits should be at a slower RPM, but I didn't think much of a 1/4" wide bit. I found (on this site) a PDF with Freud router bits and max RPM for 1" and under at 24,000RPM. With my single speed router at 25,000RPM, does that mean I can't use any Freud bits with that router?!

So lots of questions:

Does the wood matter? Is purpleheart too hard?
Was the bit defective? Are 1/2" shank size necessary?
Do I need to invest in a new VS router? I already have a VS trim router, but it doesn't fit in my table and doesn't accept 1/2".

Or was it technique? Was 3/16" too deep?

A little gun shy to go back....

Thanks in advance for your advice!
 

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Theo
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Sounds to me like routing too fast, and possibly too deep (depending on how fast you were moving the router).
 

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David - Machinist in wood
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Welcome to the forum! Add your first name to your profile to clear the N/a in the side panel and so we'll know what to call you. Add your location, as well.

Yes, significant difference between Pine and Purpleheart as it relates to hardness. My preference is to run about 18k rpm but I wouldn't think taking 3/16" in one pass would be too much unless you're feeding it WAY too fast. Did the bit grab and pull you into the wood or was that first 1/2" smoothly fed?

So that leaves you with two choices, 1) same bit, same 25k rpm, slower feed, same DOC, 2) same bit, same 25k rpm, same feed, take two passes, and C) get a variable speed router and do the same as 1 but at 18k rpm.

David
 

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welcome to the forums N/A...

what David said and you could change to a different type/style of bit like a mortising bit or a simple 2 flute straight bit...
https://www.freudtools.com/products/04-104

do the groove w/ your trim router and a edge or straight guide???
no reason a trim router can't handle that small of a cut in 2 passes...
 

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Welcome to the forum. Sounds like you may have been moving to fast. 3/16 might be a little deep as well. Solid carbide bits are hard and brittle they don't like heavy side load if your feed speed was to fast it could cause it to break. The other thought is the collet was not tight enough and the bit started pulling up into the wood as you where making the pass. The up spiral bits have a tendency to pull out if they are not tight enough causing the bit to make a deeper and deeper cut till it broke off. Don't ask how I know that from experience
 

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Hi Jim and welcome. Just out of curiosity were you routing from left to right or right to left when it happened?
 

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Discussion Starter · #7 · (Edited)
Thanks for the replies!

I don't think I was feeding too fast, probably on the slower side if anything as the piece was small (4"x4"). One other point is that the stock is 3/8" deep (which is I trying to cut a groove half way (3/16"). That reminds me, I was using a push block and push stick for the cut -- wonder if uneven pressure somewhere could've been a technique failure...

I don't recall exactly, but I think the first 1/2" went in smooth, and then I heard the cracking (and instant shake), but I could be wrong.

I was routing right to left...
 

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Thanks for the replies!

I don't think I was feeding too fast, probably on the slower side if anything as the piece was small (4"x4"). One other point is that the stock is 3/8" deep (which is I trying to cut a groove half way (3/16"). That reminds me, I was using a push block and push stick for the cut -- wonder if uneven pressure somewhere could've been a technique failure...

I don't recall exactly, but I think the first 1/2" went in smooth, and then I heard the cracking (and instant shake), but I could be wrong.
I'd use a tablesaw w/ a FTG or TCG blade for that groove...

.
 

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David - Machinist in wood
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If your bit was pulling the work piece away from the fence, and you were trying to hold it against the fence, then it's possible you got into a bind with uneven pressure holding the piece and the bit snapped. I would just take lighter passes or do what Stick said.

David
 

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Discussion Starter · #10 ·
I did end up making the cuts using a TS (with sled) and two side by side passes but with an ATB blade as I don't own a flat top blade. I may try and chisel the bottom but probably unnecessary as this is the groove for the inside of a box.

Good points regarding the type of bit itself -- webpage for the one I used says "wood, plywood, and composites" whereas the double flute one Stick links to specifically says "hardwood" -- not sure if it's just a marketing difference...

There have been several mentions of going too fast... Although I didn't think so, I guess it's always possible.

Thanks again everyone!
 

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Hello again N/A...

we have put some helpful information together at this here link to help you get up and running in the world of routers... We hope it to be useful to you... Enjoy...
do take some time and read the safety PDF's... PLEASE!!!
Blood and trips to the ER, we find, are very annoying... Not to mention – expensive...

here is some information on dust collection at this here link if it you need it...
 
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I did end up making the cuts using a TS (with sled) and two side by side passes but with an ATB blade as I don't own a flat top blade. I may try and chisel the bottom but probably unnecessary as this is the groove for the inside of a box.

Good points regarding the type of bit itself -- webpage for the one I used says "wood, plywood, and composites" whereas the double flute one Stick links to specifically says "hardwood" -- not sure if it's just a marketing difference...

There have been several mentions of going too fast... Although I didn't think so, I guess it's always possible.

Thanks again everyone!
Any time I can I like to make a cut on the table saw to remove some to most of the waste. That does two things.
-It gives the router bit less work to do and router bits suck at hogging out waste whereas saws and drill bits do a wonderful job of that.
-It also gives the chips the router bit makes an escape route so that the bit isn't cutting them over and over again PLUS it lets air in to cool the bit. In a mantle shop I worked at once we had a special little plastic clip that required a proprietary router bit to make the groove it fit in. I found we could extend the life of those bits by 3 x by cutting a preliminary groove on the TS first.
 

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1... I did end up making the cuts using a TS (with sled) and two side by side passes but with an ATB blade as I don't own a flat top blade. I may try and chisel the bottom but probably unnecessary as this is the groove for the inside of a box.

2... Good points regarding the type of bit itself -- webpage for the one I used says "wood, plywood, and composites" whereas the double flute one Stick links to specifically says "hardwood" -- not sure if it's just a marketing difference...

Thanks again everyone!
1... clean it up w/ the router or a router plane...
since you don't own a FT blade make your own plane...
or get the LeeValley router plane.... be sure to scroll the page...

2... it's not marketing, at least w/ Freud it isn't...

.
 

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Discussion Starter · #14 ·
If your bit was pulling the work piece away from the fence, and you were trying to hold it against the fence, then it's possible you got into a bind with uneven pressure holding the piece and the bit snapped. I would just take lighter passes or do what Stick said.

David
I was definitely trying to hold it against the fence! I thought moving right to left on a router table pulled it towards the fence ?

Is there such a thing as router table kickback? Is that what you're describing?

Stick -- good links! Thank you! Dunno if I'd invest $179 for a Lee Valley or Veritas router plane but those plans look great...

The posts regarding using TS to start the groove -- great advice, which I hadn't really thought of doing. Will incorporate into thought process!

-Jim
 

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Imo, it's very unlikely you were going too fast. A router is capable of cutting far faster than most people think.

When a bit snaps at right at the collet, that's a sign that the collet is bad, and should be replaced.

My guess is that the wood moved away from the fence, and the bit grabbed it and slammed it into the fence. The sudden increase in force likely caused the bit to snap. While a standard steel shank bit will flex and "give" a little bit, a solid carbide spiral is extremely stiff and rigid. This also makes them somewhat brittle. While they are incredible strong, and can handle very high foces, sudden "shocks" can easily snap them.

The bit didn't snap from too much speed, but from something going wrong, and a sudden very high force on it likely snapped it.

A bit if advice regarding straight bits. Always use the shortest bit possible, especially when routing extremely hard woods. A spiral bit with a 3/4" flute length will be much stronger, and give a better quality cut, then a bit with a 1-1/4" flute length.
 

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Mike
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(looked like a drill hole that wandered a quarter inch)
Welcome to the Router Forums.

Did the bit actually try to come out of the collet?

Pictures might give us more to go on. We like pictures.
 

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Adding to what Gerry said solid carbide bits don't tolerate chatter very well either. If you feel it chattering in the cut it's at risk of snapping. Going right to left was the correct direction by the way.
 
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Mike
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That just looks like damage from the bit snapping. I don't think it was trying to come up out of the collet so I say chatter got you. Feather boards might help.
 
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