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Discussion Starter #1
Hello all. First post, howdy!

I recently made a pin router attachment for my cheap harbor freight router table and just got around to testing it out on some patterns. Almost immediately I was greeted with some kickback. It didn't throw the piece accross the room or anything but it kinda routed inside where the pattern shouldn't have allowed it to somehow in a quick jerking fashion. I am using a brand new whiteside downcut 1/4" spiral bit on 1/2" birch ply, doing about a 1/4" pass.

On one of the pics you can see the "kickbacks" on opposite sides of the wood because I attached the pattern to the other side of the wood to experiment again with a first pass after the first test had issues.

Im pretty surprised at this, I had previously done similar patterns but using a pattern bushing hogging the entire 1/2" plywood in one pass without this happening. At that time I was using a 1/4" upcut spiral though. I thought I would be on easy street with the pin attachment and taking 1/4" passes.

On my second try on the other side of the wood I was able to get one side of the pattern to go without a hitch but the other 3 sides still had an issue. This is happening on a very slight concave curve on the pattern mostly which all 4 sides of the pattern have. It's really not a big curve at all.

I am somewhat a rookie at this router table madness. Do any experienced folk have any input into this issue? Is it no bueno to use a downcut spiral bit for pin routing, dadgum it makes a smooth cut when it's not gouging the heck out of the wood. Should I be doing a full depth pass? Maybe it's my technique or something? This gouging can't be good for the bit either, right? I really appreciate any insight, thanks!
 

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Ross
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Welcome to the forum.
 

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Welcome dcdc. How stiff is the pin. If it can move a bit it may allow the bit to grab the wood. The down cut is also pushing the wood up so I would add some feather boards or at least some guides attached to the fence that would prevent the workpiece from lifting up.
 
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Discussion Starter #4
The pin seems very stiff, and I am not pressing the template against it very hard. I think you may be on to something about the featherboard/hold down for the workpiece and template. I just hadn't seen that on any of the other pin router pics and vids I had seen. Maybe the downcut requires this though. I think I may add 2x 1/4" rods parallel with the table at the height of the piece/template combo, one on each side of the bit. It would be nice to make it adjustable in height but I'm not sure how that could be done with my janky setup and resources hehe. I will mainly be routing all the same plywood though so one height will do for now.
 

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WHen I pin route I don't use a fence. the pin routing I do is for curved surfaces and if the part gets trapped between the fence and the pin and the template wants to turn it can cause a binding and force the bit into the unwanted areas. Your set up can trap the piece between the fence and the pin and the bit . My pin arm is mounted independent of the fence.

Could be a possibility.
Herb
 

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Discussion Starter #6
hah, I guess it could be adjustable in height by just raising the whole pin router attachment thingy up since it is just clamped to the crappy stock fence of the harbor freight table. Still couldnt go down, but 50% is 100% better than 0%...or something.
 

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Discussion Starter #7
Well i don't use the fence for any...fencing. It just happens to be what the pin attachment is mounted to for convenience. Nothing ever comes into contact with it.
 

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go w/ a bearing guided flush trim bit...
 

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Discussion Starter #9
Well then I wouldn't be able to do inside work like shapes for resin inlays. Plus it would make the whole pin system a waste of time. And from what I understand the 1/4 inch bearings don't last very long besides being unavailable locally, and it has to be 1/4 inch because of the shape of some of the pattern, not seen in the pics.
 

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Discussion Starter #10
Do you guys think 2x 1/4" passes is appropriate for 1/2" birch ply with this 1/4" down spiral bit? Maybe I should do it in 3 passes instead? I would really like to keep the number of passes down, but I don't currently have a bandsaw to cut the stock within 1/16 to do one pass.
 

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Well then I wouldn't be able to do inside work like shapes for resin inlays. Plus it would make the whole pin system a waste of time. And from what I understand the 1/4 inch bearings don't last very long besides being unavailable locally, and it has to be 1/4 inch because of the shape of some of the pattern, not seen in the pics.
improve your pin system...
lower the block holding the pin so that's it's closer to the work thus reducing flex...
add gussets to the pin block and fence..
add gussets to the table and fence..

Not so w/ better bearings...
better bearings will out last the bit many times over...
there are bearing guided ¼'' spiral flush/trim bits..
Industrial router bits-Double-bearing spiral flush trim router bits-CMT tools
Whiteside Machine Company

Do you guys think 2x 1/4" passes is appropriate for 1/2" birch ply with this 1/4" down spiral bit? Maybe I should do it in 3 passes instead? I would really like to keep the number of passes down, but I don't currently have a bandsaw to cut the stock within 1/16 to do one pass.
experiment...
4 passes...
then drop to three then two passes...

would a 3/8'' dia bit work???
way many more choices...

I believe that two ¼'' passes is a bit much for for a ¼'' bit...
also, the glue in the BB isn't/won't be the bit's friend...

use a jigsaw.
w/ a good saw and the right blade you'll be amazed how quick and efficient it can be...
in a lot of cases faster than a BS...
 

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One of your problems could be the bit flexing so the extra passes would help in that case. You can get straight bits with a shear angle on the cutter. Not quite as good as a spiral and not quite as cheap as a straight angled straight bit but a decent compromise between the two.
 

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Discussion Starter #13 (Edited)
Thanks for the tips, it's daylight and I can get back to experimenting finally. I also think I didn't have the bit far enough into the collet...now my collet is kinda stuck to the router probably from the chatter during the events. Hopefully it's not a big problem. What a bonehead!
 

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we gpts PDF's for that too...

didn't think of that the bit may have moved...
 

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