Geoffrey Crabb Posted February 25, 2007 Posted February 25, 2007 The attached notes on levers may be of interest. Geoff
Geoffrey Crabb Posted February 25, 2007 Posted February 25, 2007 (edited) Whoops - Pushed the wrong button too early. See following attempt. Edited February 25, 2007 by Geoffrey Crabb
Geoffrey Crabb Posted February 25, 2007 Posted February 25, 2007 But am I the only one on the planet who is curious about the bevel, the raised ends? With softer metals I can imagine some sort of side-after-side repeated process, until the bevel is right. But with stainless steel? I can only envision tool & die and large presses. But then again - a bigger-than-normal instrument - what dark secret lurks here? /Henrik Hi Henrik, No secrets. The bevel or 'crimp' (as we call it) is formed a side at a time using suitable forming tools in a press. Whilst it is possible to form the crimp in one go to each edge of a top in brass or nickel silver it is best with stainless steel, to work around an end plate several times gradually forming the crimp until fully formed. Here are some pictures. Crimp Upper tool - common to all shapes. Crimp Lower tool - one of these is required for each shape/size of instrument. Tools set up in press. Overall view of press. The lower tool shown is suitable for 6 - 8 inch hexagonal instruments and is an original from 1860 and still in use. The working surface of the upper tool is polished but with stainless it is advisable to place a piece of bushing felt between the endplate and upper tool to avoid marking the surface. Geoff
Geoffrey Crabb Posted February 25, 2007 Posted February 25, 2007 Robin, Paul or Geoff, What is the price range for a modern Crabb Anglo (I usually prefer 40 button ones)? What is the current waiting time for a Crabb concertina? Ben I have replied directly to you. Geoff
mike averill Posted February 25, 2007 Posted February 25, 2007 Making ends fasinates me at the moment; Im disolving my Jeffries ends at an such an alarming rate that the back corner is razor sharp. Ive been thinking of getting a pair scanned and laser cut but the edges have concerned me. How many tons of press force is required for crimping the edges?
Henrik Müller Posted February 26, 2007 Posted February 26, 2007 But am I the only one on the planet who is curious about the bevel, the raised ends? ..etc, etc ... /Henrik Hi Henrik, No secrets. The bevel or 'crimp' (as we call it) is formed a side at a time using suitable forming tools in a press. Whilst it is possible to form the crimp in one go to each edge of a top in brass or nickel silver it is best with stainless steel, to work around an end plate several times gradually forming the crimp until fully formed. Here are some pictures (I have removed the pictures) /Henrik Crimp Upper tool - common to all shapes. Crimp Lower tool - one of these is required for each shape/size of instrument. Tools set up in press. Overall view of press. The lower tool shown is suitable for 6 - 8 inch hexagonal instruments and is an original from 1860 and still in use. The working surface of the upper tool is polished but with stainless it is advisable to place a piece of bushing felt between the endplate and upper tool to avoid marking the surface. Geoff Thanks, Geoff - that's it! Lovely to see it live - basically as I had envisioned. I'll sleep well tonight... ... ... Hmm - now wait - Roy, the toolmaker up to road from here, he could probably... Right, So I won't sleep tonight... /Henrik
Geoffrey Crabb Posted February 28, 2007 Posted February 28, 2007 Ive been thinking of getting a pair scanned and laser cut but the edges have concerned me. How many tons of press force is required for crimping the edges? Hi Mike I apologise for delay in response to your query. I have no idea as to the tonnage required to form the crimp, not a lot I would have thought. I use the pictured press, which is really only regarded as a ‘light’ version, as this is how we always did it finding it to be the quickest way. Over the years I have seen others attempts which have been successful. Always using some sort of forming tools the pressure being applied by various methods including the use of a large vice and various design of screwed clamps. I have often been asked why the crimp is not formed in one go to all the edges, using appropriately shaped lower and upper tools. Apart from the need for a much more substantial press, with hand made carcass components, there is no guarantee that the parts will be identical i.e. size or perfect shape*. I cut and fit the tops to match the actual shape /size of each instrument and therefore the individual crimping of each edge ensures that overall, each crimp is of equal width from each edge of the top. * The shape may not be a perfect hexagon, octagon etc. but that imperfection is usually slight and not apparent to the eye. If you manage to get replacement tops laser cut, I would be interested to see/hear about the results. Geoff
Chris Ghent Posted March 1, 2007 Posted March 1, 2007 (edited) Laser cut is not likely to be offered if you want to use German Silver. The copper content is very high and copper ducts heat slightly too well, making it harder for the laser to burn its way through. The good news is waterjet cutting is just as effective, maybe more so because there is no puddling. The only drawback to either method is the radius of the cutting force, around .4mm in the experience I had with waterjet cutting. This means any shapes with sharp internal corners (such as a crescent) will end in a .4mm radius round. The overall effect is perfectly utilitarian, but shows a loss of definition in the pattern. I had two sets cut a few years ago and apart from the above they were fine. As regards the instrument with the edges becoming thin, does it have to be a complete replacement? Perfect restorations are fine, but they remove the history of the instrument. A good honest repair can fix the problem and add to the history. GS can be silver soldered, what about a patch? A simple pressing jig can be made for crimping using 16gauge galv steel. Geoff's method is much better, but for a one off, this works (this one has actually crimped around 16 ends). It consists of an internal male hexagon and an external female hexagon around 2mm larger. The underside edge of the external hex is shaped a little. The layers of hex and material sandwich is lined up (this is the hardest part of the process), clamped together, and then crimped one side at a time in a vise. The force needed is around the maximum that could be gained in a vise, so you need to use a big one. The following is a pic of the crimping jig... Chris Edited March 1, 2007 by Chris Ghent 1
Henrik Müller Posted March 2, 2007 Posted March 2, 2007 ...The following is a pic of the crimping jig... Chris Great stuff, Chris - shows how far you can take it with simple means! /Henrik
mike averill Posted March 3, 2007 Posted March 3, 2007 If you manage to get replacement tops laser cut, I would be interested to see/hear about the results. Geoff I will keep you posted. Thanks for all the useful info. Mike A
Clive Thorne Posted March 9, 2007 Posted March 9, 2007 The only drawback to either method is the radius of the cutting force, around .4mm in the experience I had with waterjet cutting. If you find someone with a YAG laser you should be able to get that beam/corner radius down to about 30 microns. However YAG can have problems with pure copper as it reflects the beam. Not sure about German Silver. Stainless Steel is perfect for YAG. Clive.
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