Sliding Fit

[Downwindtracker2]

I have a imported 4x6 horizontal bandsaw, that I picked off CL for $50. Every time I've used it, it seems I ended up fixing some thing on it. I guess it serves me right for buying one, used to boot. The last time I tried to use it, was to cut some 3" 3/8" angle iron, the clamp just lifted, dashing any hope of squarish sort of cut. So this time, it's repair the clamp.

With the head of the movable clamp jaw, the designers hoped to have one that pivoted and slid side to side. How they expected this to happen with rough casting is beyond me. Here is the question, how many thou clearance would I need for the brass bushing in the slot and the hold down plate ? The bushing's length and diameter will govern the fit.

[Harold_V]

I'm not sure I fully understand what you're trying to accomplish. Squareness of a cut would be determined by the fixed jaw of the vise, not the moveable jaw. It should be free to move as required, so it clamps parallel to the fixed jaw.

Vises on saws face a rather undesirable problem, that of dealing with chips. If you make the fit of the moveable jaw too tight, it will be seriously limited in movement, thanks to chips accumulating in the slide area. If you make the fit too tight, it won't be able to move at all, defeating your intended purpose.

Might not hurt to post a picture of the setup you have now, so readers have the opportunity to see something that is amiss. Your problem may not be real obvious to you.

Do keep in mind, blades tend to wander. Squareness of cut can be influenced in more than one way. Small saws (those that use ½" blades, regardless of length) are notorious for not providing square cuts, and are often influenced by feed rate, or slight damage to one side of the teeth. They're particularly bad when sawing large sizes, where the blade guides are separated by larger distances. I've owned a small Wells (A7) saw for more than 50 years and have always struggled with keeping the cuts square.

H

[Downwindtracker2]

Thanks for the reply Harold . I'm probably trying to accomplish the impossible, chuckle, square in the vertical. I've worked on two or three industrial sized bandsaws over the years in maintenance shops. New guide bearing, guide adjustment and a new blade will usually get you good'nuff. And a lighter touch with the down feed hydraulics. But they require a firm clamp so the work remains flat on the table. A fish flopping on the bottom of a boat is more ridged than that worn out excuse of a clamp. I know I'm only going to be as good as the hinge to table alignment.

So far I've done the standard bandsaw cures as well as better spring adjustment and a more powerful 3/4hp Baldor motor.

[John Hasler]

Harold writes:
> I'm not sure I fully understand what you're trying to accomplish. Squareness of a cut would be determined by the fixed jaw of the vise, not the
> moveable jaw. It should be free to move as required, so it clamps parallel to the fixed jaw.

I've got a 4x6 that I think has that same vise design (though it's 30 years old and so better made). This is not a pivoting jaw the way you are thinking. The movable jaw is *slotted* with a bolt through the slot into the nut. The idea seems to be that you can slide the jaw back and forth as well as pivot it to accomodate the workpiece and then tighten the bolt to prevent the jaw from shifting as you tighten the vise. This doesn't work very well even when the slot has been machined as on mine. You can imagine how well it works with a rough casting.

Downwindtracker2: It's not clear to me where you are installing this bushing and plate. Am I correct about the design of the vise?

[Cary Stewart]

Another problem I have been shown on one of these saws was the fact that the pivot hinge for the whole saw & motor assembly was bored not parallel to the rail and fixed jaw. No matter what was done with the vice no cut was square. With some machining and a new larger hinge shaft all of which were aligned correctly the saw did a great deal better and was acceptable.
Cary

[John Hasler]

I built a table to convert my 4x6 to a vertical. The table comes off so that the saw can still be used as a horizontal but it's such a hassle to do so and then reassemble and realign the table that I rarely do it. So now I'm building a power hacksaw.

[Downwindtracker2]

John ,yes, that's likely same type of saw. I have milled the slot to 1/2" and flattened the top. The bushing will fit the slot less clearance and the plate will tighten against the bushing. The bushing length will give clearance. On my chop saw, the moveable jaw pivots, so if it works on there, it might work on the bandsaw .

The brand is TWS (Trans World Steel), a local company . I visited their headquarters in the late '80s, basically a one man show in an empty warehouse . It was likely a short lived company, so the bandsaw would date from then. And it's been abused by a few owners since.

[mcostello]

One other thing that helps longevity on almost any tool,is to replace a bolt that is tightened often with a nut and stud, preserving the threads in the clamping member. Put the wear on the replaceable stud.

[Harold_V]

Thanks for the description, John. I am not familiar with that design. The Wells A7 has a single bolt that clamps the moveable jaw such that it will still move, but can't pivot. I assumed that was typical.

H

[John Hasler]

To answer the question, I'd allow about .010" on both diameter and length. You don't want the plate to bear on the bushing and I don't see that the slot-bushing clearance is critical.

I like mcostello's idea of replacing the bolt with a stud. You could then thread or press the bushing onto the stud.

[earlgo]

All this sounds like the cra.. uh, OEM vise on the Duramatic saw from Taiwan that I bought many years ago. The vise is so bad that I have given up trying to do anything but cut parts long and then 2nd op them to size.
It has a pivoting fixed jaw that can be adjusted and clamped and a sliding pivoting moveable jaw that lifts the stock when tightened. Lovely design.

Duramatic saw vise

Oh and the sheet metal legs are/were so flimsy that a set of cross braces was added so it would sit still long enough to cut. Wasted money that I didn't have, but it worked better than a hack saw.
--earlgo

[Downwindtracker2]

It's truly an engineering marvel isn't it. I don't know the technical name for it, but the underside T-nut on mine was worn beyond redemption. Before I looked at it, I thought at first I would just braze it up a little and add something to anchor the rod end, it floats freely. I would also machine both the table slot and the underside so it would move smoothly, rough castings don't make for a smooth acting machine. Instead, as well as machining the bottom and slot ,I'll make a new nut and use a longer rod so I can anchor the end of it. Luckily I have a 5/8" acme rod and a tap left over from working on a ' 91 Taiwanese wood shaper fence. Note the country of origin. They had the rod bearing against the rough casting. The casting is angled for draft. Sweet,eh? I'll have to make a wedge for a thrust washer that I will add to bear against. I'll pin a nut on the rod instead of using the threads like they did. Outside it'll be just an angled piece of UHMW.

I'll aim for 10 thou .

Bandsaws at best are only good'nuff, but the feed rate has a big effect on the cut. I moved my piece of angle iron back so as to increase the strength of the spring.