PC 4212 material tearout

[Steve Clardy]

Finally got some time to set this dovetail jig up so I can go to all dovetail drawers.

Using the halfblind joint, which is easy to setup, etc.

I use prefinished maple ply drawer side material to speed things up on my jobs.
But due to the continuous rising costs of material, I may have to rethink using it.

Anyway, my first good joint, second try, I got everything set well.
Sides are nice and flush, and a little tapping with a mallet and they go right together.

But. I've got what I think is massive tearout, which will not work for me.
What to do. Instructions say chipout is common, use backup material. But where?:confused:

Drawer front goes on top of jig, upside down.
Drawer side goes on front of jig, outside towards jig.
I get tearout on both sides of the side piece. Inside is the worst. Should I backup with scrap there? That would mean I would have to adjust the clamp out to hold the side + the scrap.

[Ben Grunow]

That's pretty brutal and worse than anything I've had (so far-give me some time). Are you using a sharp bit and going real slow? Maybe the bit is set so low that the shank is slighty into the wood? Maybe just a bad run of drawer side material, can you try another piece? Are the two pieces tight to eachother in the jig? I usually just skim the surface on the first pass to cut the veneer and finish gently and then work my way in. Just thinking out loud. Good luck.

[Terry Flowers]

Steve, I am speaking not from personal experience with that dovetail jig, but from reading some extensive posts about dovetail tearout. You were very helpful to me when I recently emailed you about the PC guns, so I want to offer what help I can.

It seems that it is a common problem, especially in plywood. I have seen (on David Marks' Wood Works show IIRC) blue tape used to help control tearout. From the pics you posted, it may help at in least some of the areas. A light initial pass before plunging in may also help on one side. The back side probably needs a backer with the required adjustment of the jig. That, and a really, really sharp bit and a slow feed rate.

FWIW,

Terry

[Richard Wolf]

I don't know buddy, but that's pretty ugly.

Richard

[Steve Clardy]

Could be a ply problem. Will run a few more tests.
Brand new bit set at the correct depth to get the sides flush.
1/2" material. Bit is about 5/16".
Shank is not exposed.

On the drawer side in the pics, I get tearout out both sides.
Pieces are tight against each other. I'll try to get them together tighter to stop the tearout on the outer side.
Inner side towards me standing in front of the jig, is the worst tearout.

May order a whiteside bit. Maybe this pc bit isn't up to snuff.
I'll look that over too.

[Steve Clardy]

Steve, I am speaking not from personal experience with that dovetail jig, but from reading some extensive posts about dovetail tearout. You were very helpful to me when I recently emailed you about the PC guns, so I want to offer what help I can.

It seems that it is a common problem, especially in plywood. I have seen (on David Marks' Wood Works show IIRC) blue tape used to help control tearout. From the pics you posted, it may help at in least some of the areas. A light initial pass before plunging in may also help on one side. The back side probably needs a backer with the required adjustment of the jig. That, and a really, really sharp bit and a slow feed rate.

FWIW,

Terry

I'll try the tape method. What thickness backer material?

[Steve Clardy]

Ok. Terry the tape dealie seems to be the ticket here.;)
Have just a small bit of tearout on the inner drawer side.
I wraped tape on both sides of drawer side.

Had to reset the bit depth, back it off due to the tape being on there. Got that under control now.
Bit seems to be good and sharp

[Allen Bookout]

Steve,

If the thickness of the blue tape ever gets to be a problem you might want to try just plain old scotch tape. That is what I always used when cutting marine plywood and could not affort any tearout. It worked pretty good.

Allen

[Steve Clardy]

Thanks Allen. Blue tape is working. Just had to readjust everything.
Taping each side piece is going to be a pain, but I can live with that other than having tearout.

Getting some respectable joints now I can live with.:)
When I insert drawer front, [top of jig] I push hard to get it tight against the side piece.

Also changed router directions. Was going left to right, now going right to left. Climb cutting. Two passes, light, then full depth.


Also remade the scrap piece that's used as a spacer on the front to keep the clamp straight across. Everytime I would insert, remove drawer side, the scrap fell out. :mad: I don't have three hands:rolleyes: , and can't get my teeth in there to hold anything in place:rolleyes: , so I made a L-shaped spacer to hang in the clamp. Stays right where I put it when unclamping the drawer side.

Thanks guys for your help!:D

[Mike Goetzke]

I recently bought this jig. I did a lot of research and also found some had problems with the P-C bits. So I picked up a set of Whiteside bits per recommendations - this may help your tear-out too.

Mike

[Bob Childress]

Steve and everybody,

Thanks for dealing with this issue. I have just started cutting some doves with a Rockler half-blind jig and was getting tearout. Decided it was just me needing more practice (which is partly true, I'm sure) but these tips and techniques should prove to be a big help.:)

Once again, SMC comes to the rescue.

[Larry Norton]

Steve, the instructions say to backrout to cut the dovetails. For those who don't know, back routing is cutting in the opposite direction of the way you should be. You have to be careful, because back routing will try to pull the router instead of you controlling it. I just made some drawers with my brand new PC 4110, which is the same DT jig without the through DT template. It tells you to cut from right to left. It really isn't that much of a problem because of the fingers of the jig holding the bit in place.

Try it and see what happens. I'm thinking it might solve your problem.

[Steve Clardy]

Yes. Did that on the last couple of tries. Climb cutting. Much better.

Guess my instructions lack that item, or it whizzed by me without seeing it:rolleyes: which is probably what happened.

I'm satisfied with the cuts now. Down the road I need to figure out something different than having to tape every drawer side. Thats going to be a little time consuming.

[Julio Navarro]

Steve: Can you score the material with an exacto blade the shape of the pin?

Not sure this is what you are asking but if you just lightly score the shape of the pin on the back of the drawer side the blow out prob wont happen.

[Steve Clardy]

Julio. I'll check into that. Probably would have to make a scoring template so I could score each one in the right place.
But looks like the tape method would be faster for now, which is working ok.

If doing dovetails is going to be to time comsuming, I'll have to go back to my lock miter joints.
I do this for a living, so my time counts a lot in material preperation.

[Julio Navarro]

Julio. I'll check into that. Probably would have to make a scoring template....

Use the first drawer side you make. Even if you get blow out you can keep it as your templet. The score doesnt need to be very accurate and it can be inside the boundery of your pin so you wont be able to see it once the tail is cut out.

Blow out usually happens before you get to the limit of the tail guide so if you score the grain before that blow out should be eliminated.

[Ken Fitzgerald]

Steve.......Have you tried dovetailing on some solid stock versus the plywood? I have a PC 4112 and didn't have any problems using it on the solid poplar. I'd wonder about...direction of cut.....light initial pass and possibly the material......sharpness of the bit......I can't see why the jig itself would cause the problem. Goodluck! I know you're doing this in a production/professional mode versus my hobbiest mode.

[Wes Billups]

I fought with tear out when making some baltic birch drawers a couple of years ago. I changed out to a 1/2" shank bit and have zero tear out now. Just another option.
My 1/2" shank bit was even heavily used and I still got better joints than with a new 1/4" shank. I just chalked it up to cutter vibration in the narrower shank.

Wes

[Cliff Rohrabacher]

It's not the jig. If there's any doubt: Convince yourself of that by taking a same depth guided cut into the same material with the same bit - without the jig.


I think it's either the bit or the material or both.
Can you increase the speed of the bit?
Can you take lighter passes?

Get a whiteside bit and try that.

[Cliff Rohrabacher]

For those who don't know, back routing is cutting in the opposite direction of the way you should be. You have to be careful, because back routing will try to pull the router instead of you controlling it.

I can't imagine why they didn't use the traditional Tool Maker's expression of "Climb Milling" I'ts so much more descriptive.

At any rate it's the same thing.

[glenn bradley]

That would mean I would have to adjust the clamp out to hold the side + the scrap.

I have not been able get good results on ply no matter what the quality of the material but then, I'm a schlep. I get 'okay' results using a backer board as you mention (that takes care of the exit wounds to an extent) and lightly backrouting the first pass (this seems to help enough with the front tearout to make it worth the time). My final solution is to use a solid secondary wood for backs and sides. I'm sorry that is probably not practical in a production situation.

[Steve Clardy]

It's not the jig. If there's any doubt: Convince yourself of that by taking a same depth guided cut into the same material with the same bit - without the jig.


I think it's either the bit or the material or both.
Can you increase the speed of the bit?
Can you take lighter passes?

Get a whiteside bit and try that.


Yes. Never said, complained that it was the jig.

Bit seems to be fine, but I'm a whiteside fan so I am going to go ahead and get a couple of them.
Either the bit or the material. Bits get here that should determine whether its the bit or not.

More than likely its the ply material.