help using bandsaw

[agent511]

I am new, and am taking a woodworking class. I needed to re-saw a piece of ~3/4"wenge to 3/8" thickness. The wood is 5" wide.

In class at the evening high school, they have a huge commercial bandsaw. I am not sure how good the blade is. As I recall, it was about 1/2" wide. There is a high fence, like I see David Marks use on DIY. The blade cutting height has to be raised to about 10 or 12" to clear the fence.

I cut a piece of oak scrap that was about 5" Long, and it came out well. I then tried the wenge, and about 6" into the cut, the bandsaw blade started to wander and drift, and was cutting a crooked line, making my final piece less than the 3/8" i needed, even though I was starting out cutting it a little oversized.

The teacher didn't even know that they had a fence for the bandsaw (this is night school with part-time hired teachers).

He suggested I do the re-saw freehand, without the fence, so I can zig when the blade zags.

On TV, they cut veneers on the bandsaw with the high fence, and they cut them 3/16" thick, then sand them to 1/8". This requires precision, so I know that the bandsaw with fence is at least theoretically capable of doing this. .

Why is the blade drifting on me, and is there a technique I am missing, or should I just do it freehand as the instructor suggests?

[JTimmons]

Keep in mind that the bandsaw that they use on TV is probably a lot higher end than the one your using at home as well as the one that I got. I have a Rigid and a fence is useless on it in my experience when it comes to resawing. Freehanding is the best method. Draw a line down the center of the board and guide it in freehand leaving the line, I then use a planer to get it down to the size I need.

There's a free bandsaw resawing guide offered at Wood Mags site that I made and used that doesn't work bad. The article talks about the drifting problem you are having.

http://www.woodmagazine.com/wood/sto...ml&catref=wd24

Edit:
Make sure that your tension and blade guides are set correctly.

[don_hart]

All bandsaws are subject to some drift and normally the fence is adjusted to compensate for this drift. What you are describing is more than the normal drift and can be related to several factors. The tension on the blade, that sharpness and number of teeth of the blade, The quality and adjustment of the guides and thrust bearings and the feed rate. With a properly adjusted saw with a good blade you can make very precise cuts with a bandsaw including cutting veneer. The proper setup and adjustment of the saw is more important than the brand of the saw.

I would re-setup and adjust the saw and try again. Since the saw belongs to the school and you probably do not have access to a new blade I would adjust my feed rate to something slower. This should give you a better cut. The harder the wood the slower the feed rate needs to be to allow the saw to cut effectively. Also the less straight the grain the slower the feed rate needs to be.

All of these problems will be aggravated by the fact that the upper guide is so far above the piece.


Wenge is about 30% harder than red oak and that is why you had a harder time cutting it. Since it harder the blade cuts slower and if you try to feed to fast you will cause the blade to flex. Also when forcing the piece you will cause to to follow the grain and if it is not straight the cut will not be straight.

[LCHIEN]

As pointed out bandsaws are subject to drift because of blade factors and also the way the blade is supported.

Typically the drift has to be determined experimentally and the fence set to parallel the drift. IMHO the drift depends on the wood, the blade tension and the setup so it would have to be recalibrated on every cut.

Many people avoid using the fence for this very reason. They use a "resaw fence" which is not a straight fence at all. Three versions, all have the characteristic that the edge next to the blade is vertical and so placed next to the blade determines the thickness.
Version 1 is a broad curved fence, the wood touches only at the tangent nearest the blade.
Version 2 is a pointed apex, coming out perpendicular from the regular fence. The wood being resawed touches the apex.
Version three is a vertical dowel instead of the apex above.

In all three cases you mark a line where you want to resaw and guide the wood at the angle that follows the line, keeping it tight to the resaw fence which will set the thickness.

In all cases, you also want the fence to reasonably match the height of the resaw. e.g. a 12" resaw fence and a 5" workpiece is bad because the blade will be unsupported for 7" above the wood.
Better to have a 4" resaw fence and a 5" workpiece and set the upper blade guide just above the workpiece.

[MBG]

I'm a newbie to re-sawing also. I have the HF special and use a TW 3/4" band. I had to re-saw 3/4"tk x 8" wide x 4' long oak in half. I used a single point fence and had the cut line penciled in on the work piece. I had 3 pieces to cut. The first one was the best and the last was the worst. I found out through inspection that the lower blade guide became loose - it has a thumbscrew for tightening and it came loose - so check the equipment often.

I also have seen you can use a regular fence for re-sawing but it's a good idea to pass a scrap piece through first to align the fence to account for blade drift.


Good Luck

[agent511]

i am very thankful for all the excellent advise I have received. I will be looking forward to trying again next week in class.

Ill report back with results.

[LCHIEN]

MBG's description is a "single point fence"... That's a good description.
Here's the curved resaw fence from Fasttrak


Frm Jet, here's a pic of the resaw fence device (black item) attached to their regular fence.

[drumpriest]

The disadvantage to the single point fence is that it's not mindlessly repeatable. You have to adjust the board (by hand) as it goes through the blade to continually accomidate for the drift.

If you can set the fence to the drift angle, you can resaw the same board over and over with good results without having to adjust anything.

I agree with Loring though, it's an aweful lot of piddling around with it. At best every blade change, which is pretty often if you use your bandsaw for cutting curves as well.

[John Hunter]

quote:Originally posted by JTimmons

Keep in mind that the bandsaw that they use on TV is probably a lot higher end than the one your using at home as well as the one that I got. I have a Rigid and a fence is useless on it in my experience when it comes to resawing. Freehanding is the best method. Draw a line down the center of the board and guide it in freehand leaving the line, I then use a planer to get it down to the size I need.

I have a HF 14" bandsaw and when I used the blade that came with it I had the same problems. Once I switched to a 1/2" 3TPI Wolf blade it cuts using a Craftsman universal fence perfectly! I can cut perfect widths with no problems. I agree that blade tension is critical but making sure you have the right blade for the job is also needed.