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View rut's profile

Problem with dovetail jig

by rut
posted 10-29-2018 01:09 AM


17 replies so far

View johnstoneb's profile

johnstoneb

3131 posts in 2735 days


#1 posted 10-29-2018 02:23 AM

I think you’re to shallow on the vertical piece. The tails. I always cut some on a scrap piece the same shickness until I get it right.

-- Bruce, Boise, ID

View Redoak49's profile

Redoak49

4275 posts in 2551 days


#2 posted 10-29-2018 11:01 AM

Generally, how loose or tight the dovetails fit is controlled by the depth of cut…ie the height of the router bit.

View Markmh1's profile

Markmh1

113 posts in 1006 days


#3 posted 10-29-2018 01:10 PM

I believe you have something out of adjustment.

I would check how far the cutter is moving in on the horizontal plane first. It also looks like the depth is incorrect, perhaps too shallow. In any event, it does look like a compound problem. Two things out of whack.

Cutting 1/2 blind dovetails on this fixture was difficult for me, it didn’t happen right away. Start over, take a deep breath, and recheck EVERYTHING. IMO, the directions suck, but it looks like you’re very close.

Mark

View Redoak49's profile

Redoak49

4275 posts in 2551 days


#4 posted 10-29-2018 01:20 PM

The manual is very clear. This is the same with almost all dovetail jigs.

If the joint is too loose you need to take a deeper cut.

If it is too tight, take a more shallow cut.

Try a deeper cut and see what happens. You may need to make several trials to get it right. Keep track of your changes and the results.

View HokieKen's profile (online now)

HokieKen

11563 posts in 1701 days


#5 posted 10-29-2018 01:24 PM

As stated, tweak your cut depth on some scrap before you work on your project pieces.

-- Kenny, SW VA, Go Hokies!!!

View bilyo's profile

bilyo

910 posts in 1665 days


#6 posted 10-29-2018 02:54 PM

You asked about the size of the guide bearing. In addition to the comments above, it is important that the correct guide bearing be used to match the finger template being used. The Porter Cable jig came with several sized bearings. Use the one that fits between the template fingers with minimum side play. If that bearing is missing from the set, you will need to get a replacement. You will not get good fitting DTs without it. I’m going from memory, but I think that bearing guide you need is 1/2”. I don’t know if you can buy them individually or not, but it is a standard size and will be included in any set you buy.

Otherwise, it looks like you are close with your settings. Once you get the correct bearing, make some test cuts and make some fine adjustments in cutting depth.

View rut's profile

rut

73 posts in 2944 days


#7 posted 10-29-2018 09:28 PM

I guess I wasn’t thinking it was a depth issue. The depth appears really close to me. But the side to side space doesn’t look like it would be fixed by changing the depth. I’ll play around with it though.

Thanks

View johnstoneb's profile

johnstoneb

3131 posts in 2735 days


#8 posted 10-29-2018 09:39 PM

Too loose and too tight is always a depth issue.

-- Bruce, Boise, ID

View Ocelot's profile

Ocelot

2370 posts in 3200 days


#9 posted 10-29-2018 09:42 PM

I have the omnijig 24 and tried for a few days to make one good joint and put it aside a few years ago. When you figure it out, write about it.

In my case, I had trouble with the boards slipping in the clamps.

-Paul

View Redoak49's profile

Redoak49

4275 posts in 2551 days


#10 posted 10-29-2018 09:58 PM

I have a Leigh jig and have had problems with slippage also. I glued some sand paper back to back and put it between the wood and clamp. This prevented slippage.

View Kazooman's profile

Kazooman

1386 posts in 2515 days


#11 posted 10-29-2018 10:03 PM

I have a Leigh dovetail jig and can concur that your problem looks to be related to the depth setting. If this was a guide bushing problem I would expect to see more of a variation in the side to side fit of the joints. Some might be OK while others are too wide depending on how you held the bushing against the sides of the template when making the cut. They seem to be uniform suggesting that there was little or no play in the fit.

As others have suggested, you need to do trial runs on “scrap” to dial in the proper settings. I put “scrap” in parentheses, because the pieces you use for this are critical to the eventual outcome. Use test pieces that are exactly the same thickness as your good workpieces. That takes a lot of potential concerns out of the equation. Once you have the settings adjusted to give a well fitting joint keep the last set of test pieces and label them (thickness, specific cutter used, etc.). You can use them to get you very close the next time you need to set up the jig and router for the same joint.

View bilyo's profile

bilyo

910 posts in 1665 days


#12 posted 10-29-2018 10:42 PM



I guess I wasn t thinking it was a depth issue. The depth appears really close to me. But the side to side space doesn t look like it would be fixed by changing the depth. I ll play around with it though.

Thanks

- rut


Assuming your guide bearing is correct, I agree that depth is probably the culprit. Because you are cutting both pins and tails simultaneously, the depth will always appear to be close if not right on. However, because the sides are tapered, you will find as you make adjustments the sides will come closer together if your adjustments are in the correct direction. Read your instructions carefully.

View rut's profile

rut

73 posts in 2944 days


#13 posted 10-30-2018 01:25 AM

I do want to clarify that when the router (and bushing) was inbetween the fingers of the template that there was movement from one finger edge to the opposite. The bushing width did not match the width between the fingers. Does that seem normal or should it be the same width?

View Redoak49's profile

Redoak49

4275 posts in 2551 days


#14 posted 10-30-2018 11:14 AM

Please look in the manual to find out the correct bushing size. I just looked at the manual and it clearly states which bushing and router bit are used for each type of joint.

I have a little play between the fingers and bushing on my Leigh jig.

Have you tried changing the height of the router bit to see if that helps?

View Jeff's profile

Jeff

512 posts in 3757 days


#15 posted 10-30-2018 12:30 PM

Porter Cable also uses their own router bits. Make sure you use the ones that came with or are specified in the manual. Not all dovetail bits work, as I’ve experienced.

View bilyo's profile

bilyo

910 posts in 1665 days


#16 posted 10-30-2018 02:58 PM


Porter Cable also uses their own router bits. Make sure you use the ones that came with or are specified in the manual. Not all dovetail bits work, as I ve experienced.

- Jeff


I could be mistaken, but I think any dovetail bit with the same diameter and degree of taper should work. Please correct me if I’m wrong.

rut, The correct size guide bushing is important for a proper cut. There should be only the slightest of play between the fingers; just enough to allow easy movement in and out. I checked my Porter Cable jiig and it has two template sizes, 3/8” and 3/4”. The guide bushings are sized accordingly with 3/8 and 3/4” outside diameters. If your original bushings are missing, you can buy a set that will include those sizes from most any source that sells woodworking tools.

View GPS's profile

GPS

3 posts in 403 days


#17 posted 11-02-2018 07:37 PM

It may also depend on which PC Dovetail jig that you are using.
I’ve had a PC 24” Omnijig for years. It’s a bit tricky to get a proper setup but once it is set I can cut dovetails all day long.
The jig came with a specific bit. When I needed to replace the bit I had trouble finding one. So I tried different brands and different angles.
The bit that I now use is a Frued 22-112 with a 14 degree angle and 1/2” base.
The model of my jig is 7116.

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