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  • rcaffin
    replied
    re clamps and T-slots

    lifting and distorting the lips of the T slots with ATW's clamp design is much less of a risk due to how they pinch the ears between the T nuts and the bottom of the clamp bodies.
    Good point, thanks.
    I must look at modifying some more of my clamps to work this way.

    However, a lot of my clamps have to be very variable in height for tall jobs, so I use T-slot nuts with threaded rod sticking up and wing nuts for clamping at the top end. I have a range of threaded rods of different lengths - it's cheap. I do not lock the T-slot nut in place with the threaded rod driven downwards as that could upset the lip and could also leave marks inside the T-slot (not pretty and makes sliding difficult). If necessary, I also locate the bottom of the job with those low-profile clamps. In general, I find that wing nuts tightened by hand is enough when machining aluminium and plastic, but I won't rely on that for steel.

    As for the horizontal clamp at the top - I find the worn-out blades from a large ride-on mower to be very good source of steel for this. Machining and tapping that has to be done with some care of course.

    Cheers
    Roger

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  • BCRider
    replied
    Yeah, friction alone would be just fine for moving an indicator pointer. The downside being that it would try to just drop down when you loosen the knob.

    As shown if the plunger "crashes" and if the arm were only held by friction the rotating of the arm would tighten the knob. What might be better would be that the arm were floating on a sleeve or "shouldered" stud and had something like Belville washers to provide enough friction to positively move the plunger without risk of the arm moving but if we were to crash the plunger that the arm would just swing on the sleeve or shaft of the shoulder. It would be a nice bit of insurance all around.

    And back to the table clamps for another comment..... Roger, lifting and distorting the lips of the T slots with ATW's clamp design is much less of a risk due to how they pinch the ears between the T nuts and the bottom of the clamp bodies. I worry a lot more when tightening clamping setups with no direct upper support right above the T nuts. Setups such as regular strap clamps with studs and the lever fulcrum at the back of the straps where the area around the stud is open so the pressure of the T nut lifting has no support nearby in some cases. Or the style where the low profile clamps are their own T nut such as the small ones that Harold Hall showed on his web site and in his YT video.

    Now this does not mean I don't like the very low profile clamps that Harold came up with. They would work like a champ for very thin materials where we can't use a high amount of pressure anyway or the part would buckle. But we can't torque the snot out of the clamp screws on the "slot width" styles as the pressure is all purely upwards rather than a "grab" or "pinch" of the lips like ATW's clamps.

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  • mattthegamer463
    replied
    Originally posted by Tim Clarke View Post
    Tee slot extrusion from woodcraft? I do like this! I'm so inept at the grinding game. Still trying to sort it all out! Among my treasures, I have a Federal tenths indicator, I think I have found a home for it. Many thanks, Matt!
    I have the "pointer" thing keyed into the track, to keep it perpendicular to the indicator travel, but I think this may be more trouble than it's worth. It's pretty easy to "crash" the pointer on the indicator or on the oil fitting below, and it would be better if the pointer could just rotate out of the way when it crashes rather than breaking what it hits/breaking the T track.

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  • Tim Clarke
    replied
    Tee slot extrusion from woodcraft? I do like this! I'm so inept at the grinding game. Still trying to sort it all out! Among my treasures, I have a Federal tenths indicator, I think I have found a home for it. Many thanks, Matt!

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  • mattthegamer463
    replied
    This weekend, an indicator mount for my surface grinder.


    Sent from my SM-G960W using Tapatalk

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  • rcaffin
    replied
    [QUOTE]Mitee Bite "Pitbull", the "Heavy Duty T-Slot Clamp" variant looking fit for the job - I'm glad I was sat down when I saw the price!
    Whilst functionally ok, I wasn't that happy with pivot radii on the moving jaw[/quote
    Yeah, not at all cheap.
    I made my own, like yours. I tilted the top of the backstop forward a little, just enough to hold the corner of the movable bit. For the rounded corner ... I used my linisher.
    Yep: a free-hand curve, radius about 1.0 - 1.5 mm. Works just fine, and yes, grips well. Just a shade fiddly to set up, but otherwise fine.

    I also made some bigger ones - longer arms, but same principle. The one thing I think you have to watch out for is that you do not damage the T-slot, or distort the top surface.

    Cheers
    Roger

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  • ATW
    replied
    Thanks for the positive feedback, yes they are going to earn their keep.

    At first I was thinking a sharp or lightly deburred corner may be susceptible to round over so went with a large radii. TGT I wouldn't say I am annoyed with radii I obtained, its perfectly functional, its just that it wasn't what I was trying to obtain, ok maybe my expectations were too high, I was just wondering if there was an obvious trick I had missed.

    matt - yes the fixed jaws have a very slight angle to them to discourage the part from rising up.

    BCRider, yes 2cm high.

    Bob, thanks, hadn't seen those Car Lane ones, yes they look very useful and another catalogue of goodies to browse through.

    Andy

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  • Bob La Londe
    replied
    For another interesting edge clamp look at the Car Lane Tiny Vise. They make two versions (and multiple sizes). The regular one has a slot milled in the middle of a counter sink on both the top and bottom. There is a machined cone with a screw size hole that goes underneath. Then a countersunk head screw goes in through the top. Tightening the countersunk head machine screw moves the edge clamp towards the stock. The low profile version just has the slot and a single counter sink in the top for the counter sunk head machine screw. They would be very easy to make, but they can be purchased pretty inexpensively. I have used them on a variety of bases including to make an "infinity" vise so that I can mount nearly any size stock on my mill table. I think I have ten of the dual cone and ten of the single cone. I use them for odd applications all the time.

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  • BCRider
    replied
    ATW, TGT is right. You don't really need any radius at all other than to avoid actual crushing or failure of the edge. Even just a somewhat generous deburring would be fine. There's really no need or gain by having a generously rounded heel. On the other hand it does not hurt the function of the clamp either.

    I really like what you did there. Not exactly "low profile" due to what looks to be a 2cm or nearly 2cm height. But for many general items that won't fit in a regular vise easily low enough. Part of the "not exactly low profile" is due to the little shelf you did for the wedge block. But I like that since it saves the wedge block from possibly marking the mill's table. So very worthy of the slight extra height.

    I suspect you'll have many opportunities to use those fine mill table clamps.

    Leave a comment:


  • Bob La Londe
    replied
    Using tools I made in the past to make tools to use the tools to make the part to fix the tools to make your parts. LOL.

    Little tail stock die holder used to thread handles on larger die holder. Fitting threaded and test fit.

    Leave a comment:


  • mattthemuppet
    replied
    those are very nice clamps ATW, I'll have to keep that in mind. Do the fixed "jaws" on the other side have a face perpendicular to the table surface or do they have a slight angle?

    as for me, made a piloted reamer at the weekend to enlarge 3 bolt holes on my bike. Wanted to make sure the new hole was perfectly centered on the bolt axis.




    worked out really well and left a good finish with exactly the same ID for all 3 holes.

    Leave a comment:


  • TGTool
    replied
    What is it specifically about the radius discrepancy that annoys you? At first glance it seems to me not especially relevant.

    Thinking about different cases. If both pieces have sharp corners (inside and outside) I can see a couple liabilities though maybe not serious. The inside corner might crack and the outside corner get rolled over from the force against it. A crack is unlikely since the stress at that point is mostly compression and having the sharp outside corner round off changes nothing.

    A radius on the pull down block, while eliminating the previous problems will also raise the contact point and changing the geometry of the factors generating force. Again, I think this is a negligeable problem. Even if it's a full round against a flat wall on the fixed block, so long as there's an angle on the work contact face the clamping action should work.

    If you really want to get absolutely correct radii on the outside corner it will probably take a lot more work and analysis. If you have a corner rounding end mill, you'll need to establish whether the 2mm is exact. That is, could there be a tiny flat tangent to the runout of the curve. If you know it's exactly a 90 degree arc, then you can touch off vertically and horizontally and make the required moves with the machine dials, also assuming backlash and tool spring don't change anything.

    All of which is a longwinded way of saying I think you're worrying too much over it and you have a very fine looking set of clamps.

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  • Baz
    replied
    Don't you want just two points of contact along that vertex so filing some relief in the middle and leaving the corner 'as sawn' would do. Nice clamping action though.

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  • ATW
    replied
    Pull down style low(ish) profile clamps

    Needing to hold onto a lump of metal larger than the vice capacity got me looking for clamping solutions.

    Initially I was drawn to Harold Hall (Model Engineers Workshop Projects) type 4 low profile clamps, but didn't like the idea of fixing into location by grub screw down into the machine table.

    Further digging eventually led via eccentric clamps led me to Mitee Bite "Pitbull", the "Heavy Duty T-Slot Clamp" variant looking fit for the job - I'm glad I was sat down when I saw the price!

    A bit of bar stock and a couple of hours of generating chips:


    In action, with some stop blocks:



    I was impressed how much holding power was generated, very little torque was required to get a very good grip on that lump of cast iron.

    Whilst functionally ok, I wasn't that happy with pivot radii on the moving jaw:

    to the naked eye from the other end of the workshop it looks good, and does provide two points of contact into the fixed block, examination with a radii gauge reveals it wasn't the radii I was aiming for or a very good arc.

    I formed it using a corner cutting end mill using two passes to get the full circumference, with hindsight it was less than idea as it involved far too much eyeballing to get the setup.

    Any suggestions on better techniques for cutting such a radii (2mm), the edge is 30mm long and the faces are 75deg to each other?

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  • mattthegamer463
    replied
    Originally posted by Tim Clarke View Post
    Yup. A nice hunk of iron. What kind of lathe is this?
    A Busy Bee Craftex 10x18. Pretty low horsepower so it doesn't need a solid post but it seemed like something to try.

    Sent from my SM-G960W using Tapatalk

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