View Full Version : Hydraulic Downfeed on Bandsaw

John Stevenson
10-20-2002, 09:00 PM
Though I'd share this.
I have a large bandsaw where the arm lifts clear of the work but doesn't go to the vertical. This means after every cut I have to either hold the arm up whilst trying to drag a large bar thru and lock the vise, or lift it up, shut the damper valve off, slide the work through and reset the valve. As I often have to cut multiple parts this can be a pain.
So I decided to modify this. First off I took the damper cylinder off alltogether and replaced it with an air cylinder of roughly the same size. This bolts on in the same way as the old damper with the rod uppermost. I have left the top port open to the air. The bottom port is connected to a small oil tank just above and to the rear of the air cylinder. I have then fitted a flow regulator between the two. A flow regularor is an adjustable valve that restricts flow in one direction but allows full flow in reverse. This is fitted so that the restriction is back to the tank. Many people make these and they are not expensive. To see what one looks like go to http://rswww.com and enter the part number 197-5163 in the search box.
What we now have is exactly the same as we took off, just a damped downfeed.
Now for the clever bit. When the cut has finished the arm hits a stop button. I have took a feed from this stop button to energise a solinoid operated air valve. This then supplies air to the top of the oil tank.
So as soon as the blade stops air presses onto the top surface of the oil and forces the oil thru into the cylinder and raise the arm. The operating rod of the cylinder is threaded so you can adjust how high it lifts. There is no point lfting this 6" if you are only cutting 2" material.
Once you have moved the material thru you press start which starts the blade and exhausts the air from the tank allowing to arm to fall at the preset flow regulator rate.
End of cut and repeat http://bbs.homeshopmachinist.net//wink.gif
So all I have to do now is release the vise, pull the work thru and press start. No more lifting the arm up and messing with the flow valve.

John S.

[This message has been edited by John Stevenson (edited 10-20-2002).]

[This message has been edited by John Stevenson (edited 10-20-2002).]

10-20-2002, 09:07 PM
Pretty slick, John. Thanks for sharing the tip. That's what I love about this forum!

charlie coghill
10-20-2002, 11:01 PM
What air pressure are you using on the cylinder?

For some time I have been going to change my saw to a hydralic down feed,but have not done it yet.

Never thought about using air over oil to raise the saw.

10-20-2002, 11:35 PM
Mytee smart John!!

John Stevenson
10-21-2002, 04:38 AM
I just use shop air thru a reg at about 40 to 50 pounds. You have to experiment a bit as it depends on the size of the oil tank. Too much surface area and you have to reduce the pressure or it zooms up.
My oil tank is just a piece of 3" box section about 5" high with ends welded on.

John S.

10-21-2002, 02:38 PM
Clever thinking John. Thanks for taking the time to share it with us.


Paul Gauthier
10-21-2002, 04:37 PM

Perhaps some pictures of your set up and an elec, diagram. for those of us who are not elec. savvy.
I like this idea and wonder why can't you use the oil cylinder already on the machine????

Paul G.

John Stevenson
10-21-2002, 05:53 PM
Paul, yes I can do this. I'll have to do them this comming weekend as I'm away on site tomorrow for 4 days and I won't have internet access.
The reason I didn't use the original oil cylinder was twofold. One it's not easily converted as it has a valve in the piston to allow oil to pass from one side to the other. I would have had to make a new piston and rod plus alter some of the ports. This was one reason I decided to go for a standard air cyliner as I had one spare from a scrapped machine and if all else failed I could put the original back on in a matter of minutes.
Another reason was I could built all the new stuff up over a period whist the saw was still in production.

John S.

10-21-2002, 07:08 PM
another great idea/ btw I an still working on the cnc project.
One day when I get to the UK I am going to look you up
take care

charlie coghill
10-21-2002, 11:31 PM
Thanks John for the reply. Maybe I will take some time and get after the modification.

Right now I want to finish the project I am working on befor the weather sets in. Painting in the rain or snow is not my cup of tea nor does it do anything for the paint job.