bandsaw curves

[radicalwood]

Hi All,
Just a quick one, I have a small Delta bandsaw 5" depth of cut. What is the tightest curve I can get with a 1/4" blade in 3" Oak. I seem to get continental drift when going round anything less that 1.5" and it will not follow the line, gives a vertical cut which is good . Do I need a skip tooth blade or courser tpi, not sure on tpi of the blade I am using.

Cheers Neil

 

[SketchUp Guru]

You should be able to cut a much smaller radius with a 1/4" blade but you probably haven't got enough tension on the blade. It may be that with your small bandsaw, the frame isn't stiff enough to allow you to get the required tension for the thickness and hardness of the oak.

 

[Chris Knight]

It may also be worth remembering that you can only cut when pushing the work onto the blade. Many bandsaw beginners try to cut a curve with insufficient forward motion so the blade is not in fact cutting a path for itelf but just jams in the cut.

 

[CHJ]

This is one of many Bandsaw suppliers sites that will give you a guide: Harrison

You are getting pretty close to the limit with a 1/4" (6.25mm) if you are talking finished diameter.

 

[Taffy Turner]

Neil,

If you need to cut a tighter curve, then you will need to use a smaller blade (if one is available). I don't think the tooth configuration will make much difference.

The problem is caused by the back of the blade fouling on the timber if you try to cut too tight a radius. The tightest radius you can cut is a function of the depth of the blade and it's kerf.

If you need to cut a tighter radius than your blade can manage, then it is possible using a bit of a cheat. What you need to to is make a lot of cuts in the waste side of the wood up to and perpendicular to the line you are trying to cut. Basically you should have your curved line line with a load of cuts fanning out away from it. Then as you cut round the line, the waste bits break off before they have chance to bind the back of the blade.

I hope that you can understand what I mean - if not PM me your email address and I will send you a sketch which should make things a bit clearer.

Regards

Gary

 

[radicalwood]

Hi Guys.

Thanks for the info.

Dave R not thought about the tension too much will try giving it a bit more, at a guess it must stop it wandering.

CHJ I am a long way off the 16mm at a guess double that at R38 will give it another try in the next few days.

Gary I see what you mean, with the fanned cuts, trying to do a band sawn box so can not get the cuts in. Wood is about 2.5 square tying to get a good shape out of it. Maybe I should give a bigger bit of wood a go as a first try.

Cheers Neil

 

[CHJ]

OK then as long as your blade still has a reasonable set on the teeth resulting in a kerf about 1-1/2 the blade thickness you shoud be able to get much smaller.

This is 25mm radius on 6mm 6 tpi skip tooth blade that leaves a 2mm kerf.
___ click on image for larger view

A test just carried out,shows an ability to get down to 8-9mm radius with the same blade but a kerf this wide would be too much for a bandsaw box.

When checking your blade try running a flat slip stone against the back corners of the blade whilst it is running to take off the sharp corners.

NOTE: I said STONE not FINGERS