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  1. #61
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    Default Credit to Berlin

    Whilst I'm not above passing this off as my own initiative, I can't as Berlin has to take the credit for re-finding the humble wood holdfast. I was quite interested in the concept and made some up.

    Matt had mentioned when he saw my Gramercy steel holdfasts that he need not have made his model at so steep an angle. I think he was right, but I have gone to the other extreme so I would suggest somewhere in the middle would be ideal.

    Wood holdfast 004.jpg

    Making the 3/4" dowel was a bit of a headache as my lathe is undergoing repairs and I wanted to use my spotted gum. I had to drill another hole in my dowel plate. I sure you all know the technique of planing off a square batten to approximate size and then hammering it through the hole. Initially I hammered them through with a large mallet, then I used a club hammer with a dolly (1" pipe fitting cap) over the dowel and finally I worked out that I just had to plane the dowel closer to the final size before forcing it through the plate.

    This was the initial result. I did break two pieces.

    Wood holdfast 006.jpgWood holdfast 001.jpg

    Too much shaving. This is how it should be and the mallet on the floor was what I used:


    Wood holdfast 005.jpg

    These next pix show why my version is too shallow. If the clamped timber was any thinner I would run out of clamping room compared to Matt's original.

    Wood holdfast 010.jpgWood holdfast 008.jpg

    There is quite a bit of spring and the angles of the dowels are not an exaggeration of the camera.

    Wood holdfast 009.jpg

    Both types held fast ! Incidentally I think they work very well in thinner bench tops. The part of the bench these are in is less than 50mm thick.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

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  3. #62
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    Default

    Aha - thanks Paul - you've gone & done the development work after all, & saved me the trouble! Interestingly, I was going to reduce the angle that Matt used as well, and would have settled on something about halfway, so by sheer serendipity, I might have hit the sweet spot first time, which would have been very encouraging. However, it seems like there is a pretty wide range over which they will function ok, so the angle isn't super-critical.

    And good to hear they work in thinner tops, because the bench I want to use them on initially is only 45mm thick at the back.....

    Cheers,
    IW

  4. #63
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    Quote Originally Posted by IanW View Post
    Aha - thanks Paul - you've gone & done the development work after all, & saved me the trouble! Interestingly, I was going to reduce the angle that Matt used as well, and would have settled on something about halfway, so by sheer serendipity, I might have hit the sweet spot first time, which would have been very encouraging. However, it seems like there is a pretty wide range over which they will function ok, so the angle isn't super-critical.

    And good to hear they work in thinner tops, because the bench I want to use them on initially is only 45mm thick at the back.....

    Cheers,
    Ian

    I don't think I have done all the development work by any means .

    One aspect is the angle of the foot that clamps the timber. Whilst mine works and certainly spreads the load, I think Matt's holdfast clamps at a better angle. I can't quantify it, but it just seems better. You may be able to see that the foot is sitting quite precisely on the clamped timber.

    There may be another issue as the angle of the clamps is increased as there will be a tendency to have short grain. However there is no sign of breaking.

    Incidentally Matt's clamp is nicely handmade with carving marks still in place.

    I'm sure I have left ample splinters for you too .

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  5. #64
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    Default

    Looking good, Paul! They really look the part. I don't think there's any problem with their design, I think the bench and the dog holes may be the reason they aren't seating properly.

    Could you check two things for me? Firstly, because mine is just hacked out, could you check the diameter of the dowel on my version? I have a suspicion mine is a little over sized and it's definitely asymmetrical which may help it grip. Secondly, check the underside of your bench dog holes. I think they may be a little blown out exacerbating the marginal thickness of the bench. The angle your (very fine looking) holdfasts are sitting at makes me wonder if they just don't have quite enough purchase. I reckon they will lock in at a better angle in a deeper hole.

    On another note, if your appetite for hammering on a dowel plate hasn't been exhausted, I think a 15mm or even a 12mm dowel and dog hole would work just fine for most light bench top clamping and would work better in a thinner top.

    I am separated from my tools (such as they are) so it's good to have a project to watch from my armchair!

    Cheers
    Matt
    ...I'll just make the other bits smaller.

  6. #65
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    Default

    Was there another vices thread??
    My memory is going.

    A Close Look at H.O. Studley

    Cheers,
    Paul

  7. #66
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    Quote Originally Posted by Berlin View Post
    ...... I think a 15mm or even a 12mm dowel and dog hole would work just fine for most light bench top clamping and would work better in a thinner top.......
    Just a word of caution, Matt, there's probably a practical limit to how thin the dowels can go for everyday use. You might end up snapping too many if you try holding thicker material, which will tend to put a larger bend on the dowel section above the bench. I know from experience with hand-screws that it's easy to snap the centre screw if you tighten them off-parallel with the jaws wide-apart. This is particularly so with my 1/2" size screws - as far as I can recall, I've only busted one of the 1" size, & that was due to a fault in the wood rather than my clumsiness.

    However, I'm dead keen to use this idea, and as soon as I get finished with what I'm working on atm, I intend to make a few heads like Paul made & drill them at different angles for the dowels, then do a few test-runs. I will probably test a couple 'to destruction', just to get an idea of what they can cop.

    Quote Originally Posted by Berlin View Post
    ...... I am separated from my tools (such as they are) .......
    Oh dear, I do hope you & the tools can make it up & get back together....

    Cheers,
    IW

  8. #67
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    Default

    Quote Originally Posted by Bushmiller View Post
    ...

    These next pix show why my version is too shallow. If the clamped timber was any thinner I would run out of clamping room compared to Matt's original.

    Wood holdfast 010.jpg

    There is quite a bit of spring and the angles of the dowels are not an exaggeration of the camera.

    ...

    Regards
    Paul
    wouldn't it be a simple matter if drilling the dowel entry hole at a different angle to make the duck bill sit a bit more like Matt's original?

    Quote Originally Posted by IanW View Post
    ...

    Oh dear, I do hope you & the tools can make it up & get back together....

    Cheers,
    regards
    Nick
    veni, vidi,
    tornavi
    Without wood it's just ...

  9. #68
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    Quote Originally Posted by Berlin View Post
    Looking good, Paul! They really look the part. I don't think there's any problem with their design, I think the bench and the dog holes may be the reason they aren't seating properly.

    Could you check two things for me? Firstly, because mine is just hacked out, could you check the diameter of the dowel on my version? I have a suspicion mine is a little over sized and it's definitely asymmetrical which may help it grip. Secondly, check the underside of your bench dog holes. I think they may be a little blown out exacerbating the marginal thickness of the bench. The angle your (very fine looking) holdfasts are sitting at makes me wonder if they just don't have quite enough purchase. I reckon they will lock in at a better angle in a deeper hole.

    On another note, if your appetite for hammering on a dowel plate hasn't been exhausted, I think a 15mm or even a 12mm dowel and dog hole would work just fine for most light bench top clamping and would work better in a thinner top.

    I am separated from my tools (such as they are) so it's good to have a project to watch from my armchair!

    Cheers
    Matt
    Matt

    You are correct with the wear in the holes. In fact there is some wear top and bottom, but I don't think that causes a problem for the moment. Eventually it will and the timber in this bench is an unknown species and not particularly dense, although it is a hardwood.

    When I think back on my first encounters with holdfasts they came with a collar to be inserted in the bench. That was the record style of clamp.

    I also believe the dog holes in my bench have worn because the thickness of the material is only 38mm (when I took the time to measure it and I have used my steel Gramercy holdfasts. In a thicker benchtop I don't believe there would be the same level of wear.

    I measured all three shafts. The Gramercy was 17.39mm, the Berlin averaged 18mm and the Bushmiller averaged 18.25mm.

    I agree with Ian on the 15mm and 12mm shaft. I really don't think it would have the strength, but perhaps Ian will do some of the destructive testing at which he hinted.

    The armchair woodworker. Sounds almost clinical to me .
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  10. #69
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    Default

    Quote Originally Posted by IanW View Post

    However, I'm dead keen to use this idea, and as soon as I get finished with what I'm working on atm, I intend to make a few heads like Paul made & drill them at different angles for the dowels, then do a few test-runs. I will probably test a couple 'to destruction', just to get an idea of what they can cop.


    Ian

    I'm not sure the angle of the shaft into the head will make any difference and if anything it may work against clamping pressure.

    I believe there are three aspects which govern the ability of this style of clamp to exert pressure.

    1. The diameter of the shaft
    2. The diameter of the dog hole
    3. The depth of timber.

    All three are closely linked and my theory is that a thin bench top needs a reasonably close ratio of hole to shaft diameter. Possibly a clearance of .5mm

    Conversely a thick benchtop needs a sloppy hole. I had better explain that (). In my bench the holes are at least 1mm larger than the thickest shaft of the three, but in part of the bench there is a bearer beneath and the hole there goes through 213mm of timber. None of the three holdfasts even remotely gripped. There was not enough room for the shaft to skew in the hole although all the holes were nominally the same size.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  11. #70
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    Quote Originally Posted by Sawdust Maker View Post
    wouldn't it be a simple matter if drilling the dowel entry hole at a different angle to make the duck bill sit a bit more like Matt's original?


    Nick

    I originally wrestled with that idea myself, but decided against it for the reasons outlined in my post to Ian.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  12. #71
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    I compared the three holdfasts. Gramercy, Bushmiller and Berlin .

    The primary difference is the clearance of the beam or arm above the work surface as you can see in these pix:

    More Wood holdfast 003.jpgMore Wood holdfast 001.jpgMore Wood holdfast 002.jpg

    In fact the clearance to the underside of the beam is 50mm, 0mm and 98mm. Another shot:

    More Wood holdfast 004.jpg

    Some shots of the three clamps on the same piece of wood:

    More Wood holdfast 007.jpgMore Wood holdfast 005.jpgMore Wood holdfast 006.jpg

    All three held the block firmly, although the Gramercy felt as though it was indestructable, probably because it is. None of the clamps were responsible for breaking the block. It was just a piece of rubbish lying around .

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  13. #72
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    Paul, you are doing all the hard work, here - thankyou!

    Your 3 pics of the holdfasts holding the same block are particularly useful & help to clarify a couple of things for me regarding the shaft and the contact point of the head. When you said the shaft holds better in shallow & sloppy holes, it seemed counter-intuitive, at first, but I think I've got it now. My working hypothesis is that the shaft grips in the bench hole by binding on opposite sides at the top & bottom, as it's pushed sideways by the head bearing down on the surface. If the hole is a bit sloppy or shallow, it actually increases the 'bite' at the top & bottom edge of the hole, and so gives a better grip. Of course there's a practical limit to both - if the hole is too large or the bench too shallow, the shaft will lie over at a crazy angle, with the head waving uselessly in the air. So in the deep hole you tried, the bend in the shaft must be occurring only at the top, & that doesn't seem to be sufficient to give it a bite??

    On Matt's version, you have a lot of shaft exposed, and I don't think I'm imagining it, but I can see a goodly bow in it. If you were to wallop that too enthusiastically, you could snap it where it exits the bench top (though I concede 3/4" of Spotted Gum would take some breaking). On your version, you have only a short length of shaft above the bench top, which means less leverage against the edge of the bench hole. This possibly translates to less holding power. So what I want to establish is an optimum angle that will give a sufficient amount of exposed shaft, with sufficient 'spring' to hold easily, but not too much that it's easily broken if some clown (like me!) tries to bang it down too hard. It also looks like it will be a good idea to round the leading edge of the head a bit, so that it slides easily along the top of the work piece as you tap it home....

    All good stuff - thanks to both of you for bringing these to my attention. I'm super keen to make a few & give them a test run....

    Cheers,
    IW

  14. #73
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    Quote Originally Posted by pmcgee View Post
    Was there another vices thread??
    My memory is going.
    Paul

    Memory wise you are not too far gone as it is still of concern to you. It's too far gone when it no longer troubles you .

    You may have been thinking of this one started by Fence Furniture, which was more a summary of all commercial vices available, rather than the home made and improvised devices of this thread.

    https://www.woodworkforums.com/f213/w...please-167909/

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  15. #74
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    Quote Originally Posted by IanW View Post
    Paul, you are doing all the hard work, here - thankyou!

    Your 3 pics of the holdfasts holding the same block are particularly useful & help to clarify a couple of things for me regarding the shaft and the contact point of the head. When you said the shaft holds better in shallow & sloppy holes, it seemed counter-intuitive, at first, but I think I've got it now. My working hypothesis is that the shaft grips in the bench hole by binding on opposite sides at the top & bottom, as it's pushed sideways by the head bearing down on the surface. If the hole is a bit sloppy or shallow, it actually increases the 'bite' at the top & bottom edge of the hole, and so gives a better grip. Of course there's a practical limit to both - if the hole is too large or the bench too shallow, the shaft will lie over at a crazy angle, with the head waving uselessly in the air. So in the deep hole you tried, the bend in the shaft must be occurring only at the top, & that doesn't seem to be sufficient to give it a bite??

    On Matt's version, you have a lot of shaft exposed, and I don't think I'm imagining it, but I can see a goodly bow in it. If you were to wallop that too enthusiastically, you could snap it where it exits the bench top (though I concede 3/4" of Spotted Gum would take some breaking). On your version, you have only a short length of shaft above the bench top, which means less leverage against the edge of the bench hole. This possibly translates to less holding power. So what I want to establish is an optimum angle that will give a sufficient amount of exposed shaft, with sufficient 'spring' to hold easily, but not too much that it's easily broken if some clown (like me!) tries to bang it down too hard. It also looks like it will be a good idea to round the leading edge of the head a bit, so that it slides easily along the top of the work piece as you tap it home....

    All good stuff - thanks to both of you for bringing these to my attention. I'm super keen to make a few & give them a test run....

    Cheers,
    Ian

    I think that's the crux of the matter. The hold fast grips at the top of the hole opposite the beam and the bottom of the hole on the same side. It is probably the angle that the shaft sits within the hole that gives the grip. Hence the need for a larger diameter in thicker benches.

    With the timber shaft there is clearly a bending aspect that contributes to the grip up until the point where we overdo it and something breaks. There may be something of the same going on with the steel shaft, but it is not noticeable to the naked eye.

    On the destructive testing it would be interesting to use a set of bathroom scales instead of the timber and use a strong F clamp (engineer's steel) to put pressure on the holdfast. You would get some interesting stats from that I think associated with some adverse comments from SWMBO . Probably best to use an old set or see what can be obtained from cash converters for next to nothing .

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

  16. #75
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    Default

    OK. I couldn't help myself. We have some old bathroom scales that live in the outside laundry. These are the results of bashing with a 728g wooden mallet (yes I weighed that on SWMBO's kitchen scales while she went up the street ). I also tried the F clamp on the Gramercy only. I was awkward to fit on and there was only a little difference in pressure which I could have achieved equally by using a heavier basher such as a club hammer:
    Holdfast Clamping Pressure
    Gramercy 102KG
    Gramercy (with F clamp) 113Kg
    Berlin 71Kg
    Bushmiller 47Kg


    I certainly could have increased the wallop on the Berlin, but there was already a significant bend in the shaft. On the plus side, I can see why spotted gum is a favourite timber for longbows. The Bushmiller had run out of travel.

    While I looked up how many "Ms" were in Gramercy I found this on their site:


    The holdfast is designed for 3/4" hole in a workbench top of a 1 3/4" thick or thicker. 6 1/2" reach. Maximum clamping 7 1/4" in a 2" thick benchtop. Patented. Made in USA.

    Note: we have discovered that while the holdfasts work great they will work even better and in more benches if you just rub a little 150 or 220 sandpaper around the stems (not up and down, round and round)

    Now it is definitely over to you Ian because I have spent too much time on this and I'm getting the evil eye . My projects await me.

    Regards
    Paul
    Bushmiller;

    "Power tends to corrupt. Absolute power corrupts, absolutely!"

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