Jointing on the Router Table

[radhak]

I want to edge a ply tabletop with mahogany hardwood, and have been trying to joint the hw on my router table. I made a split fence yesterday of plywood that goes over my Incra fence, and am using a plastic shim (0.04" thick) on the outfeed side to support the piece after the router shaves off a that thin a skin (0.04").

I am using a 1/2" carbide tipped up-spiral bit. The workpiece is 50" long. I am doing this on a 6" wide piece and shall rip it later.

Everything seems to be working fine, but the final edge is not good enough for glueing. On close examination I can see a couple of bumps that seem to be the spots when I am 'changing hands' on the workpiece. I tried a couple of times to keep that as smooth as possible, but am unable to eliminate it completely.

Even beyond that, the edge so formed seems to be not so straight. I put it against my standard edge guide (a length of mdf that I have checked in the past to be very straight) and there's daylight at a bunch of spots : maybe 1/32"; I had done better when I had ripped the piece on the tablesaw !

Is there something I could do better in technique? Or is it something that would resolve once I joint the mating piece (the ply tabletop) also?
(I am planning to joint it face down, so if there's any issue with the router bit not square, the two pieces would compensate out).

[dbhost]

Are you using a fingerboard to keep the stock tight to the fence? I think I recall from the Wood Whisperer's demo of that technique that Marc Spagnulo used featherboards to keep the stock tight, so all he was doing with his hands was pushing (via a push stick).

(Do you have enough space to do a 6" board with featherboards????)

Never mind... I am not sure with stock that wide how to do that..

[pecker]

.04"is a pretty thick slice...I usually only do .032 on my real jointer. Maybe try half that amount.
How did you get the face of the mahogany flat? If it isn't it will rock as you go along, screwing up your edge. You can rip the board to a narrower size to help get rid of bow or cup.

I've done what you're trying to do , but only on shorter pieces...like 24" long. Try to verify your fence is flat over it's length, also.

[LarryG]

The first question I have is: what kind of router table do you have, and how is the router mounted in it? If you have a lift or drop-in insert plate, it could be moving around in the cutout enough to cause the problem you're having. If you're using a plunge router, there could be a little slop in the plunge mechanism that is causing the bit to move laterally at some points during the cut.

I'd also like to suggest you invest in a quality metal straightedge, rather than rely on that piece of MDF. I have the 38" version of this aluminum model from Lee Valley. Every shop needs a good reference straightedge, but they are particularly important in those that don't have a full complement of tools (in this case, a jointer) and must resort to alternative methods to try to get the same results.

[radhak]

Hmmm - feathboards...might have to think up of a way to do that; might help in keeping the piece firmly against the fence.

0.04" is too much...? Didn't look like that (visually)...I have thinner shims (0.02 and 0.01) too; could try those too.

The board is absolutely flat, checked on my TS's top. The two parts of the split fence are only 12" long and 5" tall. I am hoping I don't have worry about needing more length, and being 3/4" ply should be flat. Did check but could not discern any cup/warps either.

thanks for the input, keeps me thinking!

[radhak]

Larry, I have this table/insert/precision lift combination from Woodpeck, with a PC 7518 router.

You do have a point about that edge : I have been schlepping around far too long; need to get one of those now.

[pelligrini]

Featherboards or springboards should help quite a bit. I prefer them from the side and top.

Verify your fence position too. Similar results that you've had can come from the bit being very slightly in front of your outfeed side of the fence.

[radhak]

I went and checked the router/table as Larry suggested; I could not find any movement at all - rock solid.

I need to figure out how to put a featherboard in front of the workpiece, as it's wider than my usual pieces. Maybe I'll clamp one to the table.

Shall check the bit too - thanks for all the suggestions.

[herb fellows]

.04"is a pretty thick slice...I usually only do .032 on my real jointer. Maybe try half that amount.
How did you get the face of the mahogany flat? If it isn't it will rock as you go along, screwing up your edge. You can rip the board to a narrower size to help get rid of bow or cup.

I've done what you're trying to do , but only on shorter pieces...like 24" long. Try to verify your fence is flat over it's length, also.

Thanks for the flat advice, I never gave it a thought myself, but it makes perfect sense. That's why I love this website; you get answers to questions you didn't even know you had!

[Grampy122]

One piece fence

You might do better with a one piece fence like this one
http://us.oak-park.com/catalogue.htm...-&product=F020

[dkerfoot]

Featherboards are a huge help and I agree about using a thinner shim. I also have had better results using a wider bit. If you think about the cutter head on a jointer, they use a 2" or (usually) greater width. A 1/2" bit present a really small surface area and will accentuate any little joggle that you do with the workpiece.

[radhak]

Grampy, that fence is neat - the sort that'd remove all doubts at least about one factor. Of course I have to stop and think if I want to really buy something that I should be able to replicate in the shop...

I used a featherboard and tried a couple of times more. It's better in some ways but not enough to satisfy the 'absolute glue line' I was hoping for. My workpiece is now 5" wide !

After a lot of thought (and re-tries!), I get a feeling the plywood I am using for the fence is not as rigid/firm/straight as it needs to be. I need to replace it with something laminated on both surfaces with melamine or something, like the shelf material from the Borg.

The thickest (diameter) straight bit I have is 3/4", and it's not tall enough (the workpiece is 1" thick). Looking at how the piece only touches the bit at a single point, how'd a thicker bit help?

I do get that the shank should be thick and my bits are 1/2" shank.

I am using spiral bits first time, and want to go back to regular straight bits to see if that could be an issue - any thoughts?

[poolhound]

After a lot of thought (and re-tries!), I get a feeling the plywood I am using for the fence is not as rigid/firm/straight as it needs to be. I need to replace it with something laminated on both surfaces with melamine or something, like the shelf material from the Borg.

The thickest (diameter) straight bit I have is 3/4", and it's not tall enough (the workpiece is 1" thick). Looking at how the piece only touches the bit at a single point, how'd a thicker bit help?

I do get that the shank should be thick and my bits are 1/2" shank.

I am using spiral bits first time, and want to go back to regular straight bits to see if that could be an issue - any thoughts?

YOu may have found your issue. if you fence is not rock solid and true it will cause many problems. Just think that the fence represents the solid cast iron base of a jointer. Also the debate on wether to use 0.04" shims or smaller becomes rather moot if your fence is not flat, straight or unmoveable.

BTW the thickness of the shim really depends on how much you want to take off. .04 is less than 3/64s , cleaning up a rough edge is easier an quicker with a thicker shim, even 1/16". Then move to a thinner shim to do a final cleanup cut. Thats basically the process I use on my jointer, first take off as much as is necessary to get the edge straight followed by a few light passes with the table at its greatest height.

[Ed62]

There was an article in Handyman (I think) that showed a shop made featherboard. It was a long board that had kerfs cut in it to accept "fingers". This was long enough to support the workpiece on both the infeed and outfeed sides. It seems like just the thing for jointing on a router table.

Ed

[dkerfoot]

The thickest (diameter) straight bit I have is 3/4", and it's not tall enough (the workpiece is 1" thick). Looking at how the piece only touches the bit at a single point, how'd a thicker bit help?

I'll let the engineers in the house check me for honesty, but my take on it is that a wider bit will have a flatter shear angle. If you joggle the workpiece it will still be an imperfection, but it will be a little wider and flatter, so instead of a narrow cove, you end up with a more gradual error that will be less obvious.

It has been my observation a wider bit helps, but it could just be my personal bias.