I am trying to cut some legs for an Arts & Craft chair using a flush trim bit and I am getting a tremendous amount of tareout. I’m not sure what I am doing wrong.
I am using 1 1/2″ cherry stock.
A fairly low speed (have changed it around a little, but doesn’t seem to matter)
Triming 1/8″ to 3/16″ max.
I am using a 1 1/2 inch bit from Woodcraft (Do I need a better bit).
I’m trying to let the bit do the work and not force feeding it.
What am I doing wrong? Wrong bit? Too thick of stock? Trying to remove too much material?
Replies
An 1/8" is the max I'd try, probably less with 6/4 stock. One thing you can try is scallop (sp?) some material off before running around the pattern. Using you router about every 1/2" or so cut into the cherry's waste around the pattern. After you are done it should look someing like this: uuuuuuuuuuu . This will reduce the tear out and won't be so hard on the material and router. A spiral pattern bit , 1/2 diameter in you case or larger, cost more but will not tear out as baddly as a straight cutting bit....Good luck, Dale
If you've got the nerve for it Lostsouth, try running the bit backwards, i.e., instead of going left to right with the router as you look at the job, try going right to left using what's known as a climb cut. The router will tend to want to run away from you but you might get a better result, and you can progressively press harder against the pattern or jig as you go the 'wrong way.'
This technique is not one I'd suggest is used on powerful machines such as induction motored spindle moulders or shapers, but you can often get away with it using the typical 3hp+ routers--- with some care and practice.
Edited 9/1/2003 7:40:40 PM ET by Sgian Dubh
In my experience, that's just what cherry does. And I wouldn't describe it as tear but more like chunk out (well that' what I have experienced.... bits or chucks of stock breaking loose from the part...... when I think of tear out, I think of oak and that stringy grain). Anyway......
I would take much more shallow cuts. To me 1/8" cut sounds kind of big if you are experiencing "chunk" :) out. When I had the problem, I took very light passes and then also did a light climb cut (not following the pattern strictly but just a loose pass in the "wrong" direction to take off some stock so that the final pass was even lighter still).
But I don't think I would attempt a climb cut on such a large diameter bit. I think I would go for a smaller bit (1/2") with more flutes (4) and spin up the rpms to max. But of course then you will be fighting with burning (so watch out for that).
Good luck,
Rob Kress
Thanks for all the replies and quick too. Yes, it is a "chunk out", just didn't have that term at my disposal. Just to clarify a couple things, I am using a router table and the bit is 1/2" diameter with two flutes.
Based on the advice above, I plan to get a spiral cut bit and take shallower passes (or cut it closer with the bandsaw). With the exception of the "chunk out", I like the patter approach especially since I am making a whole set of chairs, so the investment in a good bit makes sense. I was a little tentative with the bandsaw. I'll trace around the template and cut right up to the line. This should get me to a 1/16".
Only one of you mentioned turning the bit speed up high. Is this what I should do?
Thanks again for all the input.
Skinny dull cutters will tearout thick stock without much ado. Would use the largest diameter cutter; at least an 1". Your overhang, no matter what cutter, is too generous. A router cut this thick is problematic, even 1/16" is too much wood. Take the cut in stages, even if the stage cut is in thickness, say 5/8(north/south) x 1/16/pass. This is a job for a shaper; routers are trimmers, alright, but not for this much trim.
Routers
LOSTSOUTH
If you try a climb-cut with the router table mounted, the feed would be reversed. It's safer to climb cut on a router table than free-hand. Not safe, but safer.
sarge..jt
If I can get up and get motivated today (out too late for our 8th aniversary dinner last night), I am going to play around with some of the ideas everyone mentioned with the scrap wood I created yesterday which I should have done with some of the scrap I already had.
I tend to be over-confident sometimes in the abilities I lack.
I used to do a lot of pattern routing when I used to make guitar necks and bodies. There is a permanent solution to the tear out problem- get two cutters, one with bearing at the collet end, and another with the bearing at the end. Then, do all the cuts that are with the grain with whichever cutter is in, then turn the pattern/job over, change the cutter and do all the other cuts. Thisd is the only way to get over this problem.
DO NOT TRY CLIMB CUTTING
John
john
And I agree with you also. I use climb-cutting as a last resort. Not exactly my favorite past-time. Standing in the middle of a inter-state highway is probably safer. ha..ha..
Good idea using the over-head bearing pattern cutter and a bottom mounted bearing on a flush trim bit to stay with the grain. Will definitely add that to my "bag of tricks".
Regards for safety and good call...
sarge..jt
I'll second John's post: Don't climb cut at this stage in the game. I thought about recommending climb cutting to you in my earlier post. But decided not to for the following reasons:
I'm assuming you are new to this type of work?
1/8" x 1.5" will jerk your material out of your hands and send it flying, plus possibility eating your finger(s) along the way.
Practice climb cutting on something else that is not removing so much wood.
Be safe,
Dale
Nice to have my post seconded, doesn't often happen to me, thanks
I spent years working on this problem, and experimented with climb cutting a number of times. Only way I would try it now is with some kind of power feed system.
John
Try pattern sanding instead of pattern routing. Put a rubbing block under a sanding drum on your drill press and use the block to guide the pattern. There was a plan for this set up in Wood Magazine# 16, October (I think) 1991. I've used it to good effect on cherry.
Certainly I'd agree that climb cutting is more dangerous if the router is inverted than if it's attempted with the router hand held. I don't use the climb cutting technique with an inverted table mounted router. I use it reluctantly in hand held operations too, but only if the amount being removed is small.
As someone else suggested, two routers, one set up with a bottom bearing bit, and the other with a top bearing bit is a good method too. Website
It just happens I have been doing a good bit of pattern work of late and was not pleased with the results. The first bit I was using was a two bladed 1/2" Freud with top bearing. Rough cut, too often had grain tear-out and if you did not watch your step it would take the work from you! Second bit was a three bladed 1/2" Whiteside w/single top bearing. Much better cut but still lacked the smoothness I was hunting for. Still had the bit grab the work and messed up the cut edges at times from tear-out. Use of a solid starting pin is an absolute must! Also raised the old heart rate a bit! Final bit is a 1/2" Whiteside solid carbide spiral, down thrust w/ dual top bearing. 100% improvement! Very smooth cut, gentle on the cut force and very predictable. Also, every attempt is made to remove no more than a 1/16". A heavier cut will work on long straight sections but I do not recommend it on curvy work! These solid carbide spirals cost easily double that of a dual straight cutter but IMHO and from my experience they are very well worth it.
I almost bought that bit when I was at Woodcraft, but couldn't get the guys attention. As expensive as 8/4 cherry is, I think I have decided to get it close with the bandsaw and clean it up with hand tools.
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