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Thread: Pitch of Acme for Bandsaw Vise
05-27-2008, 09:13 PM #1
Pitch of Acme for Bandsaw Vise
Hello everyone. I have a HE&M bandsaw that was an automatic machine, but got flooded. All the controls were ruined, and it was also hydraulic tension and clamping of the workpiece vise, which was ruined too. However, the frame, gearbox, lifting cylinders (it's double column) are good.
I've changed the tensioning to manual, removed all the ruined auto controls, and am in the process of making this a manual saw. I'm still going to make it hydraulic lower/raise of the saw head though.
Now I'm to the point of putting an acme screw on the movable vise to do the clamping. I was wondering about what pitch to go with for with the screw. Would 4 tpi be too "fast" of a pitch? The reason I ask is that I can buy 1 1/2 4tpi acme all-thread, which I need to machine down to 1" and put a key on the end (long story, but that's the size it'll have to machine down to)
I may just go ahead and cut the acme threads myself and make my own screw. That way I can make the thing any way I feel like, and not be bound by what a piece of all-thread was. Not decided yet.
By the way, if anyone has a little hyd power unit I could use for the single-acting twin cylinders that raise the head, give me a yell.
Anything to say?
Thank you for any help.
05-27-2008, 09:36 PM #2
Big shaper vises are about that pitch - would just need a suitable long handle - and plenty of slippery stay on lube.
05-27-2008, 09:36 PM #3
Thinking you might be lower cost in using an air over oil setup...the saw-raise isn't super high loads (more or less same every time), the oil flow will make this nice and slow and steady.
05-27-2008, 09:55 PM #4
I could put a handwheel maybe 12" at the largest. Enough? Another long story, but that's about all I'd have the space for.
Enlighten a bit more. I'm interested. Some sort of setup that would let me bleed down slowly to set feed rate would be what I'd need to add, I'm sure. I have a flow control made by Prince for that, but I'm not sure it goes to zero (to stop feed). I got it swapping, and it's brand new model C-503. This is no little saw, but the 500 lbs or so the saw head weighs is not much load for two cylinders. (not sure their diameter, they're inside the columns, and I really don't see me pulling them just to peek)
05-27-2008, 09:59 PM #5I could put a handwheel maybe 12" at the largest. Enough?
Just use both hands.
Besides, you are sawing, not milling or shapering.
05-27-2008, 10:08 PM #6
Check out roton.com, they've got screws and nuts at a wide range of sizes and pitches at a great price, probably worth saving yourself time to purchase from them.
05-27-2008, 10:45 PM #7
I'd go with the air-over-hydraulic as well. There's no need to run a pump for that short of duration of use. You could even run the stock vise that way with a separate reservoir.
Converting it wouldn't be difficult or take much time.
05-27-2008, 11:14 PM #8
RR, you'd definitely need a directional valve.
The simplest "air over oil" involves a double acting traditional cylinder. There are large reservoirs plumbed into each port. Half (to start) of each reservoir is filled with oil, which by gravity should go and fill each side of the cylinder. Air pressure is applied to the top of each reservoir or vented, depending on which way you want to go.
The next step of complication involves intensification, the general principle is that a large dia air cylinder applies force to the rod of a small diameter hydraulic cylinder...the difference in areas causes the intensification.
While this seems like a complex way of operating a double-acting cylinder, the oil-fill has the advantage of being stiff (can't compress a fluid) and slower acting than air (a lot of damping, slow predictable movements).
Since it uses fairly simple components, which can be sourced or made, it is a big cost advantage over a dedicated hydraulic power unit....however should you be a savvy shopper and I think I know you are, you might stumble upon a small hyd power unit at even lower cost if you are willing to wait awhile and see what's out there.
05-28-2008, 12:22 AM #9
I see what you mean. I like the air setup, but an iddy little 3 gallon reservoir should prove to be enough, maybe 5 gallons to be safe (at the very most) In square size, that's a small reservoir. I'd rather run electricity to it once than have to start compressor, etc just to saw something. Compressor only runs here to do something like blast cabinet, etc.
Besides, the limit switches are still there, and can be wired into an electrically run unit to stop it when it hits the top of the stroke. Gravity will do the rest.
You're right, that should be enough leverage for sawing, but I had to ask!
I second your remark about Roton. I've used them before and also recommend.
Original hydraulic cylinder was ruined. I will be using the saw for jobs I'd like to retain some "feel" for when clamping them to be sawn anyway.
Here's a pic of it about halfway through. I wish I had a before pic. Imagine a rusty brown sunken submarine complete with driftwood twigs. That's where it began. Gonna make one fine saw.
05-28-2008, 12:25 AM #10
I think you need a left hand Acme thread to make the handwheel turn the "right" way to close the vise.
Disclaimer: from memory, I could be wrong
05-28-2008, 12:38 AM #11
"Gonna make one fine saw." Oh yeah!
05-28-2008, 12:41 AM #12
That's exactly right (er, I mean left)
I'll be turning this clamp screw with a 90 degree 1:1 gearbox that does not change its direction. Therefore, indeed, it'll need to be a lefty still. If the gearbox had some reduction, that'd also cut down on the need for a "slow" thread too, but this was on hand, and I'm sure I'll be satisfied.
Gearbox was necessary because there wasn't room left under the saw head when all the way down to put handwheel simply at the end of the screw. Enco is running a sale on, guess what, RIGHTY screws right now. ugh
A side benefit of that handwheel position will be that it makes for being able to watch and adjust workpiece more easily while clamping it.
05-28-2008, 05:32 PM #13
As for the nut, what would be an appropriate material?
05-28-2008, 05:39 PM #14
RR, the classic "wear" materials would be bronze or cast iron IMHO.
Depends what you have on-hand...of course there are aluminum bronzes with very high strengths, but I think I'd probably want to work with cast or ductile iron.
05-28-2008, 06:13 PM #15
I don't know what you're cutting, but if it's a horizontal saw your cutting forces are going into the fixed jaw. All you need is to close the vise enough to keep the stock from jumping up and down. Your 4 pitch should do that just fine.
The helix angle is the same as a 1"-5 ACME. I'm using a 1"-6 ACME in my vise. That should get me about 20% more locking force.
One important factor is the rolled thread is VERY smooth. It should last until your grandchilderen have grandcuildren.
I use the Keystone alloy screw.
05-28-2008, 10:52 PM #16
That's an interesting point about the helix angle.
Also, I have a brand new RDRS-1975-30 Prince flow control valve laying around. I'm thinking of using it for the "throttle" to set the speed of saw head descent to cut. To do so, the bypass port would be plugged and all flow would go through the controlled port. I know it's overkill, but if there's any other comment about using this, please share. It's here already with no investment, and brand new. Here's a spec link:
Thanks again, gents, for the helpful input.
06-26-2008, 05:48 PM #17
The bandsaw is now a lot further along. I've done some work to make it manual clamping, manual blade tensioning, and the drive is operative now. More pics of the two-input (either operable from the front or the back) vise later. Doing that is made possible by fitting a two-input gearbox shown. These are pics of fitting that gearbox into the place the hydraulic cylinder used to fit into and how it got achieved. Anyhow, here's the tool porn. Enjoy.