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View Full Version : Saw drifting in the cut - what to do?



Scott M Perry
05-10-2014, 12:54 PM
Hi, all -

I've finished filing and setting my project back saw, and it's drifting:

https://farm3.staticflickr.com/2906/13966460029_6f00ebf9eb.jpg (https://flic.kr/p/nhaKYZ)P1020094 (https://flic.kr/p/nhaKYZ) by Scott -- (https://www.flickr.com/people/87126550@N00/), on Flickr

I've repeatedly stoned the left side of the teeth, and it's helped a little, but it's still drifting. Not sure what to do - keep stoning, refile?

Thanks,
Scott

Kees Heiden
05-10-2014, 3:24 PM
Is the plate straight from front to back and especially from top to bottom (Spine to teeth)? Not twisted?

It could be very uneven set right or left, but he is drifting a LOT. If the plate is straight, I don't see much else then resetting.

Jim Matthews
05-10-2014, 9:22 PM
Did you set the teeth?

Stoning will reduce some of the cutting area on one side,
and can lead to some ragged performance, as teeth with
less set that are still really sharp will catch in the kerf.

The idea is to have each tooth meet the wood at the same depth
and breadth in the kerf left by the last pass.

If you're bearing down on a backsaw, try to lighten the pass by either
taking an upward angle or subtly "lifting" the saw.

If you've got less than 12 teeth in an inch, slow and steady wins the race.

From what I can see of the test cuts,
you have a kerf that is rougher on the left than the right.

I recommend using a saw set, to get 4 thousandths of an inch clearance on each side.
That's enough for a properly sharp backsaw.

If you don't have a dedicated saw set, you can do the same thing with a hammer and punch (of screwdriver with a tip broad enough to cover each tooth).

Lay the saw down flat, on its right side.
Put a piece of hardboard beneath. The softer the board, the more you can move the teeth.
Tap each tooth on the left side, lightly with the hammer and punch.

No need to strike hard, you're just trying to ease them back closer to the center line of the plate.

Refile after this step, as you're likely to blunt the tips.

http://www.getwoodworking.com/news/article/sharpening-hand-saws/783

Roy Lindberry
05-10-2014, 9:53 PM
You may be gripping the saw too tightly.

Jim Koepke
05-11-2014, 12:10 AM
Did you file the teeth all from the same side?

Some people like that with a rip saw if there isn't to be any fleam.

For me it always seems to pull the saw to one side. YMMV.

I would give it a few more passes with a stone to see if it helps. I have had a few that needed a lot of stoning before they would cut straight.

jtk

Ron Bontz
05-11-2014, 1:36 AM
PM sent with a laundry list of things to check. :)

Jim Matthews
05-11-2014, 7:50 AM
Listen to Ron.

He made my best saws.
They cut straight, and true.

Jim Matthews
05-11-2014, 7:53 AM
I would give it a few more passes with a stone to see if it helps. I have had a few that needed a lot of stoning before they would cut straight.jtk

Does this induce an additional bevel to one side?
I managed to get a saw stoned to cut straight, but it took so much
off the teeth that it would bind easily.

Only recently was I advised to set the teeth prior to sharpening.
That made a remarkable difference in performance.

The first few test cuts were sufficient to take down particularly "proud" teeth.

Judson Green
05-11-2014, 10:02 AM
Only recently was I advised to set the teeth prior to sharpening.
That made a remarkable difference in performance.


Jim,

Is there reason/explanation for this? Seems counter intuitive.

Jim Koepke
05-11-2014, 10:56 AM
Does this induce an additional bevel to one side?

That is the only explanation that comes to mind.

I could be totally wrong. What works for me may not work for others.

jtk

Jim Matthews
05-11-2014, 2:29 PM
Jim,

Is there reason/explanation for this? Seems counter intuitive.

I thought the same, until I saw Matt Cianci demonstrate.
He joints most saws twice with the set applied after defining the tooth shape.

http://www.wkfinetools.com/tRestore/saw/howIfile-Cianci/howIfile-01.asp

I was advised that if the saw had a straight tooth line and well formed teeth
to apply the set before sharpening. My saws now cut straighter, with less binding.

I have no idea why it works better, but it seems to help.

My guess is that the set lightly deforms the tooth, but I can't see anything smaller than 5 tpi.

Ron Bontz
05-11-2014, 4:58 PM
I don't think this is a set problem. But a nickels worth without getting too involved. Setting the teeth after you have filed them will alter the geometry of the teeth you just filed defeating the purpose, to some extent, of filing the teeth correctly in the first place. On my saws, I joint, set, sharpen. It's better to have a little extra set than not enough. We make too much, I think, over having minimal set. So who cares if a saw has 0.0025" of set per side instead of 0.002"? Other than bragging rights. Nanny nanny boo boo. :) But on vintage saws in rough shape, I sometimes will joint, shape, set, initially to get it close. Then come back and joint, set, sharpen. It is just a little quicker sometimes. An aluminum oxide pad, those maroon things, will often remove most of the burrs without dulling the teeth. Not to mention fine scratches in the plate. Rub the plate a few strokes from heel to toe. Stoning the teeth, especially cross cut can dull the tips of the teeth. Lastly, if you suspect you have a filing/ set problem, seek counseling, :) Or run your fingers down the sides of the teeth, heel to toe. Sometimes you can pick up on a few teeth here and there that stick out further than the rest, which may be just enough to cause a little bit of drift. In which case, look up the Wenzloff trick. I will often check several places along the tooth line for consistency after setting the teeth. So ok. More than a nickels worth.

Kim Malmberg
05-12-2014, 3:13 PM
The curve in the cuts in Scott's picture remind me of a Tyzack & Turner tenon saw which hangs unused on my shop wall. This particular saw refused to cut straight whatever I did. The culprit was a bend in the plate but a bend in the direction from spine to toothline. So whatever I did to that saw it would always go left on me. As others have said I think this would be worth checking.

Mike Allen1010
05-12-2014, 5:50 PM
Scott, lots of excellent advice here from people that really know.

Jim K asks an excellent question, the kerfs look suspiciously like a saw that has all the teeth filed from one side, rather than only filing the teeth set away from you and then reversing the saw in the vice to file the others.

I also really agree with both Ron and Jim M. that stoning the outside of the teeth on the side the saw is drifting towards is really more of an "final tuning" step, and won't correct the amount of drift you are experiencing and additionally can dull your cutting edges and otherwise change some of the geometry you worked hard to achieve.

Perhaps most relevant is Ron's suggestion that with a toothline that's in rough shape, IMHO it's helpful to go through two iterations of jointing and setting, before final sharpening of the teeth. In my experience this yields more consistent result.

If you have the opportunity to spend some time with someone in your area who can coach you a little, they could likely quickly see the cause of your issue and help you fix it.

Scott, Lastly don't give up, you've done the hard work of building the saw and this is definitely fixable.

All the best, Mike

Mike Siemsen
05-13-2014, 1:24 PM
The curve in the cuts in Scott's picture remind me of a Tyzack & Turner tenon saw which hangs unused on my shop wall. This particular saw refused to cut straight whatever I did. The culprit was a bend in the plate but a bend in the direction from spine to toothline. So whatever I did to that saw it would always go left on me. As others have said I think this would be worth checking.

The plate on your Tyzak saw could be cupped but if the handle is flat sawn rather than quartersawn the cupping of the handle can introduce a cup into the plate.
A saw that is jointed lower on one side will drift as well. My gess is you need to refile, it sounds like you are new to sharpening and there is probably a variation in the teeth introduced by your technique when turning the saw around to file from the other side. Filing or stoning the teeth from the side is something that is usually done very sparingly. A close up photo of the teeth from the side and end might help.