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Thread: Leg vise experiences?

  1. #16
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    My only input on the design is to avoid having the protruding parts at the height of your pockets.

  2. #17
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    Quote Originally Posted by Prashun Patel View Post
    Michael, then I've had it wrong all this time. The screw should be as high as one can stomach in terms of sacrificing depth.
    Prashun,

    Not necessarily; by the time the screw is 3/4 of the way up the chop, you're already getting at least 3/4 of the screw's total force on your workpiece (more if you have the work low in the vise rather than at the toe). A few inches up or down on a typical leg vise height won't make much difference in clamping force (but will have some effect).

    Placement of the screw will have more effect on comfort and capacity than on clamping force.

    There are definitely diminishing returns as you raise it higher and higher. I'd say, rather, that one should place the screw as one judges based on the tradeoff between convenience/comfort, clamping force capability, and capacity. Where the "right" placement ends up seems to involve too many factors to make a recommendation without knowing about the person and their work.

    Then, there's the relationship between chop thickness, toe-in angle, and flex that can limit the maximum practical clamping force independent of the screw, say if toe-in becomes toe-out due to too much force applied for the chop design. Deflection is going to be based on the ratio of length to thickness (modified by width) and will also depend on screw placement. I can go into more detail if it's helpful.

  3. #18
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    I don’t recall seeing many 12/4 leg vise chops. Most seem to be 8/4 which in My experience is adequate. I did line the face with leather. I’m not too concerned with chop deflection. In terms of species, I think maple is easier to work than hickory and the closed grain helps in having a smoother finish. I have no regrets in going with maple.
    Last edited by Joe A Faulkner; 01-15-2021 at 8:23 PM.

  4. #19
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    Hi Scott,

    I would be happy to help with the calculations if you would like. I have a good deal of experience with mechanical analysis.

    Michael

  5. #20
    Nice. Thanks. I donít know bout your fancy math . I just know my old back donít like stopping. The leg vise is easily the most powerful of my vises and I suspect up or down it will be plenty strong.

  6. #21
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    It appears you already knew the most relevant information, then.

    Should you choose to adjust your setup, you now also know that you won't compromise on clamping force.

  7. #22
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    Mid coast Maine
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    Here are are some real world numbers on what one of my leg vises is capable off. If you canít see the dial it is 1600 PSI.

    5A9E2373-6DC3-4EDE-A17B-D18FEA91BE8B.jpeg

    In answer to your problem Scott of the top of the jaw opening up, there is an adjusting nut at the end of the chain that makes it easy to dial in just the right amount of toe in so at full pressure the jaw is possible.
    full disclosure I am the vender of the chain kit. Iím just here to answer questions, I hope that is ok.
    Jim
    Ancora Yacht Service

  8. #23
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    A couple items and then I will have to leave this be for a few days.

    I have written down on my Monday to do list the phone number for NELMA so I can order the grading guide for northeast and great lakes USA. Can't do beam calculations without knowing what grade lumber you are using. Local to me none of the hardwood from the NEMLA area has grade stamps on it. Hopefully the person I get on the phone can tell me how to find the grading rules that are supposedly free .pdfs on the website, I couldn't find them.

    I did do a beam calculation with a 5x5 inch hickory timber. For beams and stringers, hickory, (american) beech and birch all use the same table. So imagine a select structural grade hickory beam 5x5 inches and three feet long. Set two anvils on your driveway so the outside edges are three feet apart, set the beam across them. Set one of your hands on one of the anvils and under the beam. Have a friend lower a Toyota Corrola or similar 2800 pound item on the beam 12 inches down from the end of the beam over your hand, 24 inches from the other end, a point load. The beam will not fail, and will only deflect 0.029 inches.

    I don't know of anyone using a chop five inches thick. At some amount of force the threads on the screw and nut will fail.

    All: Please keep your data points coming. "My chop is 2.5 inch thick maple, four inches wide at the floor, 12 inches wide at the benchtop, no issues" is all I really need.

    Michael B:

    There are many things timber framers are willing to do if an engineer trusted by both the builders and the building inspector signs off on the blueprint, but the timberframers would not attempt if an engineer hadn't signed off. I am not a timberframer. I did spend most of my free time last winter learning about it. And this beam is an unusual situation in the load comes and goes and comes and goes, much more rapidly then seasonal snow load.

    I have to get the grading book in, find reasonable design values for material I can get, and I have to leave the through hole for the vise screw out of the beam width. If the chop is two inches wide at the bottom stop block and the through hole for the vise screw is two inches on center there is no beam, from a timber framers perspective.

    In say 2-3 weeks I should be able to write up reasonable beam calcs, makes sense to start with hard maple. When I get to the end of all that you or anyone else who feels qualified is cordially invited to look it over and say because of x, y, and z this item is actually 30-50-200% stronger than calculated.

    Jim R:

    Your posts come up in my search results here often, glad you are still around. I have wanted a wood screw face vise since I used one in Junior High shop class, and can finally justify it as my current vise wracks too much to do the thing I am trying to do now. My suspicion is the AYS chain system on the parallel guide is going to meet 75-90% of my needs. I saw a new thing recently since I last watched all the leg vise videos on you tube. If you were to interent search "Jay Bates leg vise" and kick over to the "videos" tab of your search results you should find a 22 minute video near the top of your results. If you open that and pause it six seconds in you will see a wedge on the floor that will probably tell you all you need to know.

    I am planning to do both, just run the AYS chain system routinely (It is still, after eight years, good enough for Derek Cohen for heaven's sake), and have the system from Jay Bates video ready to go.

  9. #24
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    Hi Scott,

    When designing based on acceptable levels of deflection, strength becomes a non-issue unless youíre using very stiff and brittle materials (think ceramics). Far more important is the elastic modulus and the geometry. If, however, you want to order the grading guide and run the calculations for your own edification, I wonít try to dissuade you.

    For the screw, there will be a pull-out strength based on the effective shear area of the threads; that said, itís not as simple as the calculations might lead you to believe. Going by just the shear area formula, one would conclude that more threads engagement is always better. However, as long as the screw maker has done their job properly and in the case that the material of the screw and threaded hole are identical youíll generally get very close to maximum strength on a coarse thread with 4-5 threads engagement (more for fine threads). This is because the materials deform under load (the screw stretches, for example) and the first 4-5 threads end up taking most of the load (highest load on the first thread, less on the second, and so on).

    The screw is unlikely to be able to apply a large enough load to break any reasonable chop design, particularly if the chop has been designed for appropriate stiffness. This includes under cyclic loading as well as static loading. Put another way, Iíd recommend you design the chop for the stiffness you want and let the strength take care of itself.

    If I understand your goal correctly, youíre interested in whether you can get away with using locally available lumber for a high-performance chop rather than ordering something. I am confident that you can; I am willing to help.

    Michael

  10. #25
    Jim Ritter, You are allowed to answer technical questions and offer advise. You just can't tout your website or link to it unless it is a photo illustration of your comments. Thanks for asking.
    Dave Anderson
    Chester Toolworks LLC
    Chester, NH

  11. #26
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    Quote Originally Posted by Michael Bulatowicz View Post
    Hi Scott,

    When designing based on acceptable levels of deflection, strength becomes a non-issue unless youíre using very stiff and brittle materials (think ceramics). Far more important is the elastic modulus and the geometry. If, however, you want to order the grading guide and run the calculations for your own edification, I wonít try to dissuade you.
    I agree with you here. On all the models I tried Fiber stress in bending (FSB) and Modulus of Elasticity (MoE) were the key components to stiffness. Is MoE the same as elastic modulus? I am not knowledgeable enough to assume it is.

    Anyway, when I piled weight on my model beams they all eventually failed in horizontal shear, but it was high FSB and high MoE that limited deflection before shear failure.

    I need the grading guide so I can tell what I am looking at. I did all of my computer modeling based on select structural grade, but there may not be any select structural eastern hardwood in all of Alaska today, I won't know until I have the grading guide in my hand. If it turns out what I can get my hands on is grade I then I will go back to the models.

    Quote Originally Posted by Michael Bulatowicz View Post

    For the screw, there will be a pull-out strength based on the effective shear area of the threads; that said, itís not as simple as the calculations might lead you to believe. Going by just the shear area formula, one would conclude that more threads engagement is always better. However, as long as the screw maker has done their job properly and in the case that the material of the screw and threaded hole are identical youíll generally get very close to maximum strength on a coarse thread with 4-5 threads engagement (more for fine threads). This is because the materials deform under load (the screw stretches, for example) and the first 4-5 threads end up taking most of the load (highest load on the first thread, less on the second, and so on).

    The screw is unlikely to be able to apply a large enough load to break any reasonable chop design, particularly if the chop has been designed for appropriate stiffness. This includes under cyclic loading as well as static loading. Put another way, Iíd recommend you design the chop for the stiffness you want and let the strength take care of itself.
    I think the screw threads are the weak link in the system. They are probably strong enough. A big enough timber I will load directly onto sawhorses from my truck, cut whatever joints it needs, and put it on the ready to assemble stack while my leg vise is nice and warm and dry inside the house. I guess I am doing exactly that, designing the chop for minimal deflection and expecting the screw threads to be strong enough for any piece of wood I am likely to ever put in there.

    Quote Originally Posted by Michael Bulatowicz View Post
    If I understand your goal correctly, youíre interested in whether you can get away with using locally available lumber for a high-performance chop rather than ordering something. I am confident that you can; I am willing to help.

    Michael
    That's pretty close. My goal is to not have to do this twice. One and done, lifetime vise, won't have to replace it. I have identified five contenders for my vise chop. All the below values are for select structural grade.

    Red Maple, no suprise, 1300psi FSB, 1.7 million psi MOE
    Doug Fir, king of the west, (but not the DF-Southern grown in AZ, CO, NM, NV or UT) FSB 1300, MoE 1.7
    The Beech-birch-hickory group, FSB 1450, MoE 1.7
    Southern Yellow Pine FSB 2400, MoE 1.9
    Yellow Poplar FSB 1000, MoE 1.5

    Sitka Spruce I cannot afford, but it is probably otherwise a contender with good FSB and MoE in larger cross sections. I don't have design values for Sitka Spruce at 8/4 or 12/4, when I saw the price I stopped looking for the design values. I have never seen SYP for sale up here.

    Rabbit hole: Red and white oak are traditional chop materials with very high Shear strength, they can take more weight than any of the above before they too eventually fail in shear, but they deflect more. White oak FSB 1200, MoE 1.1. Northern Red Oak FSB 1200, MoE 1.1. Mixed oak FSB 1150, MoE 1.1

    Having run a bunch of stiffness calculations I am planning on a 12/4 chop, planed flat to assumed 2.75 inch thickness. It will be eight inches wide at the floor. It will widen as it rises 23.5" to the horizontal center of the screw and be 10 inches wide there, and then widen to 12" width at the bench top about 10" higher than that.

    In the beam modeling I did all five of those were showing 0.02 inches deflection at 12/4, when I dropped back to 1.75" thickness (8/4 planed flat) the deflections ranged from 0.07 to 0.11. So 8/4 is good enough, 12/4 should improve my stiffness dramatically. At least at the one loading point I tested for - 500# uniformly distributed.,

    If I did the math right and Lake Erie sends me a screw as long as the one they sold me (they have a great reputation, I just don't have my personal screw to measure against my bench), but I should have a max jaw opening of about 12.25" with a 12/4 chop, or 13.25" jaw opening with an 8/4 chop. I think 12.25 inches jaw opening is plenty.

    The 12" width at the top is not set in stone. Local birch just doesn't grow that big without also having notable center rot. If I find a beautiful beautiful piece of hickory that is only 8 inches wide I will probably not use it for a chop.

    For now I am looking for a 12/4 billet 12" wide and 36 inches long from one of my top five.

  12. #27
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    I guess I have enough of a plan for Michael or anyone else with a background in higher mathematics to take a shot at it. From a timberframe perspective, for a building, this simply doesn't work. The big hole in the middle of the chop to pass through screw divides the chop into two spindly little beams that will struggle to hold up a case of beer without unacceptable deflection. But face vises work, I don't dispute that.

    I ordered the 2X system from Lake Erie, so I have to drill a 3.0 inch hole through the chop and the through the vise leg for the screw. Smaller holes should take less strength away from the chop (and the vise leg), so I don't see any point in analyzing what larger holes would do to the system, though an engineer might, and I will not dissuade them from doing that.

    The undercarriage of my bench is all 4x6 nominal Doug Fir. For my next (bigger) bench I will be using an 8x8 timber for the vise leg. Drilling a 3" hole in the 5.5" wide face of the vise leg feels kinda creepy. My expectation is my current 4' bench will be my sharpening station once I have a bigger shop space and a 6-8 foot workbench. The new/expensive vise I am installing now will migrate to the new bench. The craptastic vise is fine for saw sharpening. When I build the longer bench I can use a 3" through tenon for the side stretcher centered under the vice screw hole and also drill vertically for the AYS chain without doing much in the way of damage to the side stretcher or the vise leg.

    I will put pics of my vise leg here, and then discuss:



    The side view of the vise leg is the first picture. Relevant you can see my craptastic home center vise at the top, and then double pinned the 5.5" face of my side stretcher. The side stretcher is shoudlered on the visible face down to the perfect 3x5 leg within the nominal 4x6 Doug Fir leg I started with. Below that is a vertical 2x6 with grade stamp showing and a through hole, that is part of the bottom shelf so parts don't fall off the shelf, and then a bit below that is the end grain of the through mortise for the front stretcher.

    If I could pull the side stretcher out in a vacuum you might think I was using half lapped joints, or recognise it as a bare faced tenon in situ. My plan is to cut nominal half inch deep shoulders for the vise nut, same as for the side stretchers, so I don't weaken the back face anymore than it already is.

    Second pic is the face surface of the vise leg with probably a pretty good approximation of layout. I don't have any of the parts here to actually do the final layout but I am probably within a quarter inch or so.

    From the top my crappy current vise, the horizontal 2x4 DF stud with the grade mark on it is the front surface of my top. Headed down from there a 3" circle to pass the vise screw, below that a hole I think at 5/8 or 6/8 to pass the AYS chain, my best guess at clearance for the AYS sprocket above the side stretcher, then the end grain of the side stretcher visible on the face. The chain hole is also spaced to not require any drilling of the vise nut from Lake Erie, I hope. The drawn mortise for the parallel guide starts 1.25" below the side stretcher (hopefully enough room for the second AYS sprocket), passes through the through knot and then bites a notch in the front stretcher tenon about 1" deep. Below that I have about 8" of exposed leg surface unadulterated. I started this bench in Dec 2018 and finished in Jan 2019, the through knot I can move maybe 1/8 or so with my thumb, I plan to hammer it out and then get a saw in there to cut the parallel guide mortise.

    AYS chain is to pass through the chop just below the screw, through the front leg without messing up the Lake Erie nut, bend over a sprocket to a vertical hole to be drilled in the side stretcher, hit another sprocket, and then run along the top of the parallel guide to the end of the guide. I will likely attach some sort of dust ruffle out of cheap plywood to keep dust and crud off the screw and chain.

    Jaw depth, from bench top surface to top of screw is going to be about 8.5 inches. Bench height is 34 inches.

    I am fine with this, 8.5" jaw depth, 12.25 max jaw width, for heavens sake. If I am working even a 24" piece of 8x12 I'll fasten it to the bench top with holdfasts, longer pieces of 8x12 won't even be coming in the house.

    For the chop my current plan is 12/4 stock planed flat to 2.75" in any of Red Maple, Southern Yellow Pine, Yellow Poplar, the beech, birch, hickory group or Doug Fir (not Southern - D Fir S). Continuing with the chop, I plan to start half inch off the floor at 8" width and taper evenly to 10 inch width at the center point of the vise screw, 24" off the floor, 23.5" up the chop. Above the centerpoint of the vise screw I envision more taper with the top increasing in width to 12" at the bench top about ten inches above the screw center.

    About. Since the vise leg on my next bench is going to be 8x8 (probably white spruce or Doug Fir) I don't see a good reason to make the bottom the chop less than 8" wide. If an engineer of some kind can say making the width at the bottom 10 inches will make the the chop 16.58% stiffer because Orion gnu theta omicron I will make it ten inches at the bottom. I am not married to having a twelve inch wide face at the bench surface either. Realistically, 12/4 stock greater than 10" width end to end and select structural grade is going to be hard to find, and it is going to be rift sawn in my budget.

    Have at it fellas. We have three MDs here that I know of here, and I don't know how many engineers. I am just a trogdolyte who knows if I build it stout it will last. I failed Calc I twice; calc II, Ochem and calc based physics once each. All of my degrees are in the social sciences.
    Attached Images Attached Images
    Last edited by Scott Winners; 01-17-2021 at 3:32 AM.

  13. #28
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    Hi Scott,

    Thatís plenty of information for some analysis.

    With regards to the question of having the chop tapered from 10 inches at the screw to 8 inches at the floor compared to leaving it at 10 inch width the whole way, there wonít be much differenceómaybe a couple percent at most. This is because the parallel guide is applying a load near the centerline of the chop rather than distributed all across the width, so the extra material on the sides of the hypothetical 10 inch base width is almost completely uninvolved in load bearing. Iíd say go for the taper.

    The wooden nut will help distribute the load on the leg, but Iíd suggest some lateral reinforcement of the leg: it looks to me like you have a crack running up and down the leg from the mortise. I canít say how deep it goes, but itís a weak point that will be exacerbated by the 3 inch hole. There are a number of ways to go about it, but the basic idea would be to reinforce as if youíre trying to clamp the crack shut.

    Regarding leg stiffness and strength, as long as the crack doesnít cause a problem youíre not likely to notice the difference before/after boring the hole: for a vertical load, for example, itís still going to be about 95% of the present stiffness after you install the vise screw, the chain assembly, and the parallel guide. If the wooden nut is attached well, you should actually have a slight increase in bending stiffness.

  14. #29
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    The two pictures I posted of the vise leg yesterday were taken yesterday.

    I looked at a few pics from Jan 2019 in my phone, edited them to upload and now I can't find them in my phone while it is connected to my PC. The crack around the knot was not there when the joinery was freshly cut.

    During the build I did split open two or three of the offcuts from my 4x6 legs and stretchers and found pretty consistent 20% Moisture Content, occasionally a 19% would show up, using a homeowner 2 pin meter for firewood. The 4x6 is homecenter Doug Fir with the S-GRN icon included in the grade stamp - Surfaced Green.

    Extreme humidity swings in my shop, I see 25% RH at 64dF this minute (I have a sensor out there), 6-9% RH at 55dF is common when it is colder out. Summer time highs for say Jun and July will be 70-80% RH and 70-80 dF.

    I do think this is a potentially serious stress fracture, exacerbated by both the front and side stretchers having been drawbored about 1/8 inch, at a weak point in the grain. I had to put those knots somewhere, I picked through a lot of 4x6 to get the ones I did buy. Plus the clear wood probably moved more than the knot wood as the leg dried down.

    I do not -have- to put the parallel guide there, nor am I married to a particular size or shape. The more I lower the guide, the more of the through tenon for the front stretcher will be cut away.

    I guess the next thing to do is hammer out the knot and try to see how deep the surface crack reaches. I'll try the big fat one centered in the side stretcher too, one of these pics is of the vise leg from the back side of the bench with part of the shelving out.

    20210117_131006[1].jpg20210117_131032[1].jpg20210117_131052[1].jpg

  15. #30
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    And a closer view of the back side of the vise leg with the side stretcher coming in from above. I don't like it.
    Attached Images Attached Images

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