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Forum topic by KevinBlair posted 12-02-2015 01:03 AM 818 views 0 times favorited 27 replies Add to Favorites Watch
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KevinBlair

56 posts in 1793 days


12-02-2015 01:03 AM

Topic tags/keywords: band saw dovetails jigs

I’ve been trying to cut dovetails. My plan has been to start with band saw and maybe table saw methods and then move onto a hand saw. I may post elsewhere on the Disston & Sons 8” saw I got from a flea market that turns out to be from the 1880s. I am going to send it to be sharpened soon.

My band saw dovetails are not turning out as hoped. The pins are fine, it is the tails that I cannot seem to get right. I rewatched the Alex Snodgrass video via youtube on tuning the band saw (which is a new Rikon branded as Craftsmen 10” saw) and feel confident that it is running correctly (see pic of 2” rip cut) and cutting straight.

I have been following the 4 videos in the link below, as well as using plans from American Woodworking and Fine Woodworking on how to cut dovetails with a band saw.

https://www.youtube.com/watch?v=JYBn7WSOQgA

See the pictures, but the blade seems to twist a bit and drift each time I cut the tails. As first I wasn’t sure what was happening, so I remade the jig. But watching closely as i cut, I see the blade twist rather than stay straight (the jig effectively angles the wood such that the cut is a straight cut—see pictures).

The pics should show: 1) rip cut, showing saw cuts straight, 2) how the jig aligns the wood for a straight/ tail cut, 3) that the angle of the jig is correct ( 1 6), and 4) the cut that I get:

I’m thinking maybe a different blade? This is the one that came with the saw. But, the cut should be straight and if it cuts straight with the fence, why can’t I get a straight cut with the jig—especially as I’ve remade the jig to make sure it is correct.

So, my next guess is human/operator error, but I can’t figure out what I’m doing wrong…especially as I can get a straight rip cut…

Any ideas??


27 replies so far

View ThomasChippendale's profile

ThomasChippendale

244 posts in 400 days


#1 posted 12-02-2015 02:04 AM

Do a test and tell us the results:

Cut partly in a piece of plywood along the fence and stop the blade, hold everything in place and see if the rear of the blade touches one side of the cut. Oh and check that the fence and slots in the table are perfectly parralel.

-- PJ

View bandit571's profile

bandit571

14655 posts in 2151 days


#2 posted 12-02-2015 02:39 AM

I USUALLY cut the pins first ( backsaw as I have trouble tilting the bandsaw’s table) use the pins to mark the tails. I then cut the tails on the bandsaw. I cut on the waste side of the lines, leaving the lines. If I need to pare a bit for fit, not a biggie..

Whatever the saw used, cut on the waste side, and leave the lines. Then you can pare away as needed for a decent fit.

-- A Planer? I'M the planer, this is what I use

View ChefHDAN's profile

ChefHDAN

809 posts in 2317 days


#3 posted 12-02-2015 02:46 AM

Kevin, take a peek at Matt Cremona's method I just used it to do an entertainment cabinet with my first “hand cut” DT’s and it went very well

-- I've decided 1 mistake is really 2 opportunities to learn.. learn how to fix it... and learn how to not repeat it

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exelectrician

2327 posts in 1895 days


#4 posted 12-02-2015 05:11 AM

Try a different blade.

-- Love thy neighbour as thyself

View rwe2156's profile

rwe2156

2200 posts in 948 days


#5 posted 12-02-2015 12:49 PM

Looks like blade drift to me. Could also be tension. Bad blade unlikely.

WADR to Snodgrass, he is a salesman and has a slick presentation. I’ve tried his “ride the gullet” technique with both my bandsaws and not been able to duplicate. IMO you’ll never totally get rid of drift and you have to adjust your fence accordingly. That being said, if you’re constantly having to readjust the tracking, you either have blade tension issues or a crummy saw.

I would start by making sure the blade tension is good that is the biggest factor in wiggly cuts.

Adjust for drift: Draw a line on a board about 2 feet long and carefully make the cut stopping about half way through. Do not move the board! Adjust fence to parallel to board. You have adjusted for drift and should get straight cuts.

If you’ve done all this and still can’t get accurate cuts check all the guides. If it all checks out, I would try another blade. If that doesn’t work, you probably need another bandsaw…...

-- Everything is a prototype thats why its one of a kind!!

View bondogaposis's profile

bondogaposis

4037 posts in 1819 days


#6 posted 12-02-2015 01:36 PM

What size blade is that? Use a wider blade that is good condition, tension it properly.

-- Bondo Gaposis

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johnstoneb

2150 posts in 1640 days


#7 posted 12-02-2015 01:41 PM

You answered your own question. This is the blade that came with the saw. Get a new good quality blade. Tension it properly and go.

-- Bruce, Boise, ID

View ThomasChippendale's profile

ThomasChippendale

244 posts in 400 days


#8 posted 12-02-2015 04:35 PM

I have a completely different view on blade drift. I have used 5 different blades on my saw in one year and at first each had exactly the same amount of drift, the same way. Of course I could adjust the fence to match the drift but when I used the slots in the table, the blades wanted to follow a different path, the so called drift. So I adjusted the TABLE parralel to the blade and the fence square to the table. I have no more drift on any blade and everything is square.

Remember also that the blade needs centered on the tires since most tires will vave a concave shape, the blade also needs to be sharp and the kerf wider than the body of the blade on both sides.

I also had in one occurence the throat plate get misplaced and higher on one corner than the tabletop, this caused out of squareness and drift.

-- PJ

View KevinBlair's profile

KevinBlair

56 posts in 1793 days


#9 posted 12-02-2015 07:31 PM

Thanks everyone! I really appreciate all of the help. I think all of you can tell that I am not a band saw expert in any way :-)

As requested, here are 2 pictures of plywood cut straight, blade stopped and the picture is from the back. I hope they show up clearly. I did it quickly this morning before heading to work. It seems to me that the back of the blade is touching the kerf and that may be part of the problem.

I have done most all of the suggested ideas (greatly appreciated! They help confirm that I am not missing anything.) The table and miter slot are square to the blade and the table is level with the blade at 90 degrees. The fence is also square to the miter slot and the blade. When I do a rip cut, I get a very straight cut that I can clean up at the jointer.

This is why I am perplexed by the tail cuts with the jig. With the wood set in the jig, this is essentially a straight cut that is 3/4” long, but the blade does not follow the line (see picture in OP). Why can I get a straight rip cut using the fence that is 12” long, but cannot get a 3/4” cut using the jig??

Can a blade be over tightened? That is have too much tension? I felt like I had to tighten it a lot to get to the “tap with a finger and see less than 1/8” movement” per Snodgrass. I was reading about doing a flutter test for tension and may try that this evening.

I did follow Alex Snodgrass’s suggestions and set the blade so that the deepest part of the gullet is centered on the upper wheel. This did require adjusting the wheel as initially the blade “walked” forward…hopefully I didn’t take things out of alignment.

I tried free handing the cut, but I clearly need a jig/fence.

A different blade seems to be the best next step. I believe that 3/4” in the widest blade I can use with this saw, but I need to check the manual.

If you can give me some ideas, that would be great. Kevin

View rwe2156's profile

rwe2156

2200 posts in 948 days


#10 posted 12-02-2015 07:37 PM


I have a completely different view on blade drift. I have used 5 different blades on my saw in one year and at first each had exactly the same amount of drift, the same way. Of course I could adjust the fence to match the drift but when I used the slots in the table, the blades wanted to follow a different path, the so called drift. So I adjusted the TABLE parralel to the blade and the fence square to the table. I have no more drift on any blade and everything is square.

What are you using the slots for?

You certainly can adjust the table instead instead the fence maybe if using a miter gauge to cross cut (did mine even come with one?) but IMHO, adjusting the table just to keep the fence parallel to the slots, is really an unnecessary effort.

Thinking about it, I never do Xcuts or use a miter gauge, I’m always either ripping or resawing maybe that’s why.

-- Everything is a prototype thats why its one of a kind!!

View ThomasChippendale's profile

ThomasChippendale

244 posts in 400 days


#11 posted 12-02-2015 08:14 PM

I use the slot, like Kevin, to run some jigs so it has to be parralel to the blade also, if you never use the slots, then only the guide has to be parralel. In my case, I have a resaw sled to cut timber on the band saw into planks, cannot afford any drift.

Kevin, if the rear of the blade touches the kerf, you will have drift, its acting like a rudder and twisting the the blade, forcing it away from the guide or drifting. You can either adjust the guide but if using the slots for your jig, you have to loosen the bolts and adjust the table until the rear of the blade is not touching either side.

-- PJ

View KevinBlair's profile

KevinBlair

56 posts in 1793 days


#12 posted 12-02-2015 08:43 PM

I’ll look more carefully when I get home, but it seemed to me that the rear of the blade was touching the right side of the kerf (right side when facing the blade as it cuts); see pic in last post. If I move the table, it looks like it would be a millimeter or two to get the kerf centered on the cut. I would then have to recheck the miter slot for square in relation to the blade and fence; hopefully the millimeter of change won’t take everything out of square.

If that doesn’t help, I bought a set of 3 blades from Sears when I got the saw. Could be of dubious quality, but I’m thinking I’ll try one of these blades and see what happens.

The slot holds a runner that is attached to a small sled like jig. A pin cutting jig and a tail cutting jig can be used with the sled. The sled and the jig are 90 degrees to the blade (I’ll check again when I get home, maybe I missed something here). The youtube video link in the OP show them in action.

View rwe2156's profile

rwe2156

2200 posts in 948 days


#13 posted 12-02-2015 10:44 PM

Kevin,

That seem like it would be a rather tough and/or tedious adjustment.

No way to run the jig along the fence? I’ve seen people cut dt’s on the bandsaw using the fence and spacers.
Set the fence to the widest dimension and add for each cut.

You could also make sled runners adjustable. Like a slot for runner screw to give you some wiggle room.?

Thomas,

I haven’t ever used a resaw sled I’m guessing you are sawing logs in the rough, right? Even so, you can still use a drift-adjusted fence to guide the sled, no?

Not meaning to be argumentive, just a suggestion to simplify the process for you guys.

-- Everything is a prototype thats why its one of a kind!!

View daddywoofdawg's profile

daddywoofdawg

1010 posts in 1042 days


#14 posted 12-02-2015 11:30 PM

I have the craftsman version of that saw,and have the same issue,what is happening is the blade is twisting causing the cut to go off straight.
The fix I don’t know yet,If you figure it out please post.
I do know If you keep the guides almost touching the wood it helps some.

View ThomasChippendale's profile

ThomasChippendale

244 posts in 400 days


#15 posted 12-03-2015 01:16 AM

The sled has two runners and works fine, adjusting the table is a matter of loosening some bolts between the frame and table and re-tightening, say one hour. I do advocate spending extra time adjusting machinery square in every way and saving time later adjusting other parameters to make it work. Obviously there are difference in opinion on this matter, even Laguna sells the driftmaster fence so you can adjust the fence to the blade drift, glad I didn’t spend that $300 since once the table is square with the blade, there is no more drift on any blade. The bandsaw came with the table so much out of square that I suspect they really want to sell the driftmaster and want you to believe in blade drift!

However, on such a short cut as is a dovetail, blade drift should not affect, could it be Kevin that the piece is not clamped down to the jig and that it moves forward while the jig is not following, then it would push the blade sideways some and cause a curved cut?

-- PJ

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