PDA

View Full Version : Wilton Bandsaw question



Fasttrack
07-05-2007, 12:15 PM
Hi guys - i've been on my brother-in-law's farm so i haven't had much chance to check out whats been going on. I did run into a problem today though...

I've been working on fixing up thier Wilton bandsaw, model number 7000. Its a pretty old saw from what i can tell, they bought it used 12 or so years ago. The hydraulic downfeed was completely dry of oil. The hose had been leaking so we got new hoses and re-assembled. Apparently, when it was new, the valve could be completely closed and the saw raised easily at which point the flow regulator/valve would prevent the saw head from descending until you opened the valve again. Right now, i've done my best to get all the air out and it works about 90% of the time. Sometimes when its raised up the valve doesnt catch and the saw head descends. I'm inclined to believe the valve is just sticking or completely shot. Before i jump to conclusions, i was wondering if anyone had run into this problem or if anyone had suggestions as the correct procedure to bleed air from the system. There is a small set screw above the cylinder that i assume is the air bleed and it seems to have worked well but... well i'm all ears if you guys have something to say.

Mike Burdick
07-05-2007, 01:51 PM
Without seeing the assembly any suggestion I can give may or may not apply. So...

Some of the cylinders used for lowering the saw use a piston which has a rubber or leather washer This washer, when put in compression, will expand and seal; on the backstroke it will allow fluid to pass. A bicycle pump works this way, at least the older ones did. This method uses the cylinder itself for a reservoir and allows for huge flows of fluid from one side to the other on the opposite stroke. This ensures no resistance - a good thing when lifting the saw to the top.

If your cylinder is designed this way then sitting for a long time without oil will naturally cause this "washer" to dry up and not work as expected. You might have to "improvise" that washer since it may not be available anymore.

pcarpenter
07-05-2007, 02:44 PM
My first hand experience with these is limited to what I have seen on other folks saws and the research I did on making one for use on my Tiwanese 4x6. They typically use a control valve that has the check valve (so you can lift quickly) built in. You may have to replace that valve if its failed. They are supposedly a common item and I have found them at McMaster-Carr. The trouble may be finding one that takes the same fittings and with the in and out pointing in the appropriate directions. You may be better off calling Wilton.

The other possibility is that you are not done bleeding air. Bubbles have a knack of finding their way to the top of the reservoir over a period of time. Trapped air does not always find its way out right off the bat. I'd keep bleeding. Air is much more compressible than hydraulic fluid and could explain why it would drop suddenly. However, that ought to be a limited drop and not all the way. A longer drop suggests the check valve is stuck in the "lift" position.

Paul

Fasttrack
07-05-2007, 09:20 PM
Thanks guys...

I got her finished today, the total deviation from side to side on my test piece was .018 ... the manufacturer allowed gross deviation is .006 so we're doing good there!

I bled all of the air out several times but i noticed if i fill with oil at the top of the stroke the cylinder doesn't compress all the way... i reckon i had been adding oil at the wrong place. Got it worked out now though. It stays up as long as you lift it easy. If you throw it open and let it bounce a bit you can here the valve leaking fluid past in a hiss as the head descends. Thats no big deal though - just got to take it a bit easy with it is all.

Thanks for the tips and suggestions. I haven't torn into the valve or the cylinder so i'm not to sure what variety they are (whether they have the washer deal or a check ball kinda deal in the valve). The fittings wouldnt be a problem if we needed a new one though - the old valve kinda sucks the way it is. It puts the lines at a really sharp 90* bend, its almost a kink. That was where the old ones began leaking at so we need to find some elboes to go on there.

ProGunOne
07-06-2007, 01:57 AM
If you can post pictures of your set-up, I may have the elbows you need and possibly a valve? I'm on vacation this week though, won't be able to check until next week.

Mike Burdick
07-06-2007, 02:12 AM
Some manufacturers may make small fitting but I like to make my own. I just use brass bar and drill holes in it a couple of thousands larger than the copper or brass tube and solder them in. This makes for a nice compact installation and one gets the exact fittings needed. One can even make really cleaver valves, check valves, and flow controls - all that limits oneself is their imagination. Brass is not required either - steel works just fine too.

If someone enjoys this sort of thing, make a "one-shot" lube system for his or her lathe’s carriage. If planned right it can be added such that the lathe's carriage won't be modified. That way the lathe will still be original if it is sold it to someone else.

RetiredFAE
07-06-2007, 01:36 PM
I needed to bleed a similar cylinder recently, and it seemed all I was getting were very small bubbles of air, one at a time out of the bleed screw. Not being noted for being patient with such things, I wire tied a vibrating electric engraving pen to the side of the cylinder at the low end, turned it on, and walked off to do something else. Came back in about 10 minutes, turned the bleeder screw and got one big air bubble out of it, no more air in it. Seems the vibration helped the little air bubbles merge into one big one in a hurry. Saw a fellow who was bleeding mercury filled manometers do this years ago, figured if it worked on a fluid as dense as mercury, should work on hydraulic oil too.

Fasttrack
07-06-2007, 04:20 PM
I needed to bleed a similar cylinder recently, and it seemed all I was getting were very small bubbles of air, one at a time out of the bleed screw. Not being noted for being patient with such things, I wire tied a vibrating electric engraving pen to the side of the cylinder at the low end, turned it on, and walked off to do something else. Came back in about 10 minutes, turned the bleeder screw and got one big air bubble out of it, no more air in it. Seems the vibration helped the little air bubbles merge into one big one in a hurry. Saw a fellow who was bleeding mercury filled manometers do this years ago, figured if it worked on a fluid as dense as mercury, should work on hydraulic oil too.


:D I didn't have an engraving pen but i did have a screw driver. The cylinder did recieve several whacks during the bleeding proccess!

Don't worry about the elboes - there may even be some hiding somwhere on the farm. It used to be a huge hog operation but the parternships were disolved awhile ago. The founder (my brother-in-law's father) got most of the land, the mill, the shop and all the other buildings but theres alot of stuff that got bought or packed in by employees that they don't know about. The old shop is packed with fittings and odds and ends ... ... its a great place!!!