Ultimate flush trim bit grief

[George Yetka]

I have and like the Whiteside machine ultimate trim bit. Until recently it has been great.The past 2 times I had it in my table I have been left with violent events. No injuries. In both cases the workpiece was slowly moved into the bit and immediately kicked off of it, leaving severe tear out and a rattled operator. Any ideas on the cause. I am slowly feeding the work piece edge grain first into the bit. the Work piece is walnut and the cut is 3/4 inch tall by about an 1/8". Im wondering if maybe the bit is bent slightly I will check this after work. Has anyone had these issues?

[Mark Hennebury]

Photos of the setup and operation would clarify, so you will have a better chance of getting the correct answers.

[George Yetka]

Ill grab them tonight to post up tommorrow

[glenn bradley]

If you are leading a starting edge into the bit you run this risk. A starting pin can minimize the risk but some sort of a sacrificial "rider" on the bearing is your best bet. If you are flush trimming there is obviously a surface that you are using for a reference. If this surface does not extend an inch or so beyond the "keeper", there in lies your problem. The bearing and bit should be engaged prior to beginning to cut your "keeper". I do not know if I am being clear.

Notice the reference surface that you are flush routing to . . . the template in this case . . . extends beyond the actual cutting of the blank. This allows you to fully engage the bit prior to your excess stock beginning to be cut flush.

Template routing lead in.jpg

If you try to start at the point that the reference surface and the blank both start you can get kick back. A starting pin can work if you are experienced with this operation but, a lead in will almost guarantee a smooth cut without kick back.

[Prashun Patel]

Whiteside bits are usually high quality.

How old is it? Has it been dulled?

[Mel Fulks]

Could just be a grain issue. Use sandpaper , or preferably a small round over bit “climb - cutting “ to get rid of sharp corners before using the
trim bit.

[Christopher Charles]

Gret tips Glenn. I’ve used starter pins but hadn’t thought about a rider on the template.

[George Yetka]

20220926_183201.jpg
This time around I did start with end grain. The Bit is about 4 years old but it probably only has 100 linear feet of use. I am going to set up a test where I have a very little bit to cut that has a good starting point and test the bit low in the table and run with push blocks, if I still have issues Im replacing it

[glenn bradley]

I see now that this is a top/bottom bearing bit. This means you can always route with the grain. That is, by using the top or bottom bit on the template piece as required you never have to exit at an unsupported location or route 'uphill'. All this blathering is me trying to say that I do not know that the bit is the issue. It may be an operational problem.

If I were trying to make the cut I see in the pic I would set the fence close to flush with the bearing's edge that is closest the operator position. I would then let the material to be removed ride the fence and be cut away as the template meets the bearing. Much like a jointer operation it may take multiple passes. Even if you only did this for the first inch or so at each corner you would avoid that troublesome area.

I do a lot of template routing and now and again I am faced with a situation where the cut begins right at a corner with no lead in from the template. What I should do is stop an make another template that provides a "take off and landing" surface that extends beyond the material. Sometimes I don't and I get away with it. Sometimes I fail and have to take much more time making a new blank than stopping to do the operation correctly would have taken me. When this happens I thank the shop gods for teaching me humility

[Mike Henderson]

If the work is straight, one thing that has worked for me is to use the fence and adjust the fence to be exactly aligned with the bearing. Then, I slid the work into the bit and the work is well supported.

Mike

[Prashun Patel]

I think your problem is taking too aggressive of a cut (exacerbated by starting on the end grain).

Those compression bits may give cleaner edges, but I don't think they are any less aggressive than straight fluted FT bits.

These top/bottom bits are an issue because you are required to take off the whole bite at once. It's way more work, but switching to a top bearing pattern bit first allows you to nibble the cut at repeated depths. Even going half way with that and then switching to the bottom bearing bit will improve your chances of success.

If that's just too painful, I will glue on the template and then take it to the bandsaw and cut off the corners and end grain to within a whisper of the final dimension before taking it to the router table.

[Mark Hennebury]

Looks to me like a simple case of you not keeping control of the wood. You need to start contact around the side, so you have a surface to press against the bearing without cutting anything, keeping the wood firmly pressed against the bearing start to pivot around the corner to the end grain. If you are nervous and not pressing the wood hard against the nearing you will get the bounce and digging in. You need a sharp bit. The bit is cutting in the correct direction, so it won't do that damage unless; it is really dull, and or you are not keeping the wood tight to the bearing. A dull bit would make work harder to keep the wood pressed against the bearing, but it still wont do that damage unless you let it.

[Ben Schmidt]

Starter pin! I have the same bit and it's a beast, will grab especially at end grain. But I slowly rotate the piece into the bit with a starter pin as the fulcrum, and then it's pretty easy after that as long as you maintain contact with the bearing for the rest of the cut. Lots of pressure down into the table as well.

[Richard Coers]

Besides the other good advice, 1/8" x 3/4" is a lot of wood to remove in one cut. I leave 1/2 that amount. It's not the bit's fault for the grab.

[Bill Dufour]

I do not see a fence or a pin. I would remove 90% of the cut on the jointer or tablesaw. use a safety cutter so it can not dig in so deep.
BilLD