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Brazing after milling whilst preserving accuracy

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Bill Phinn25/02/2019 22:37:59
161 forum posts
35 photos

The images show two typeholders, one made commercially many years ago and one still in the process of being made by me.

As you might expect, typeholders like this are used for holding moveable type, but specifically bookbinding type, which is typically brass.

I milled the brass channel (about 2.5" long) out of brass bar, and would have liked to do this after brazing the shank on to it, not before, but since, in order to get square not rounded inner corners, this milling needs to be done with the open side facing upwards, and the tiny Proxxon milling machine I have doesn't allow me to stand everything upright once the shank is in situ, I had to mill the channel on its own before brazing.

The reason I'm posting this is that I noticed after I had brazed on the shank that the formerly perfectly flat, long internal edge of the channel was no longer perfectly flat, but was ever so slightly convex. I'm fairly sure this is a result of brazing with the open end facing downwards and the weight of the channel and shank being supported by the "arms" at each end. Essentially, I think the channel sagged slightly once it got to a very high temperature and stayed that way after it cooled.

My question is, if I do this project again but this time lie the channel down for brazing rather than standing on its arms bearing the weight of the shank above it, will the perfectly flat, milled long edge stay as flat as it was before brazing, or is there still a chance movement will occur?

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Ian P25/02/2019 23:29:06
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2082 forum posts
89 photos

I see little chance of the part staying exactly the same shape before and after brazing. If at the moment the brazed joint 'sets' there is any difference in temperature in between the two lumps of metal, or the way the two masses cool down than there will be an element of differential contraction. I doubt the orientation whilst brazing will make the distortion you experienced.

Most extruded brass (and other materials) change shape during machining because if internal stresses.

Is brazing essential, why not fix the shank mechanically?

Ian P

Bill Phinn26/02/2019 00:45:14
161 forum posts
35 photos

Thanks for your reply, Ian.

On all of the many commercially made typeholders I own, some going back possibly 150 years, the shank and inner body (i.e. the brass channel) are either an integrated casting, or in a few cases possibly cut from a single piece of metal; I have never actually seen one where shank and body appear to be connected by brazing.

The few examples I've seen where a mechanical connection was employed were all recent and rather naff home-made affairs, and the connection used was only questionably up to the job of dealing with the constant heating and cooling and the considerable forces that are applied when the typeholder is in use.

I've resorted to brazing basically because I don't want to employ the services of a caster, and brazing is the next best thing after a casting (or possibly equal to it) in terms of its strength, permanence and, not least, trustworthiness in the eyes of the end user.

Which brings me to commercial considerations. I could try a mechanical connection, and I'm fairly sure I could make it a reasonably strong one, but I wouldn't expect the finished item to have the same appeal or trustworthiness as a casting or brazed connection in the eyes of other bookbinders if I came to sell it on. There simply are no precedents I'm aware of of a typeholder that was widely or even sporadically used in the bookbinding trade that employed a mechanical connection to join shank and body.

Bookbinders are a conservative breed, or at least used to be; the phrase "hide-bound" aptly sums them up.

Hopper26/02/2019 05:18:02
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3527 forum posts
68 photos

Could you silver solder it, which would take less heat and cause less distortion?

JasonB26/02/2019 07:01:34
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Moderator
15175 forum posts
1548 photos

Is there any reason you could not drill two small holes in the lower flat plate so that after soldering you can skim the 3 inner edges with a milling cutter and then pass a square file through the holes to clean up the corners.

not done it yet26/02/2019 08:35:28
2814 forum posts
11 photos

You might try rough machining your piece then heating to (near) brazing temp before finish milling? that may take out any stresses in the work due to the initial metal removal. Might work but, there again, it may only reduce the distortion.

Wout Moerman 126/02/2019 08:37:04
6 forum posts

You can use a mechanical connection followed by soft soldering the result can be quite unvisible is the connection is placed in the right place.

Ian Hewson26/02/2019 09:08:00
256 forum posts
19 photos

Could you use an epoxy adhesive, devcon etc , I believe some radiators are now glued together rather than soldered?

possibly adding some brass rivets for extra security, invisible if countersunk.

CuP Alloys 126/02/2019 09:39:02
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186 forum posts

Keep any distortion to a minimum by firstly keeping the brazing temperature to the minimum. Use the 55% silver alloy eg 455.

Secondly use a thinner rod that requires less heat from the joint for it to melt. Consider 1.0 or 0.7 or 0.5mm wire.

Heat the components slowly to bring the joint up to temperature evenly. Consider using a long life flux eg HT5. Re-examine your heating technique

Cool the joint slowly in dry sand or mica.

Regards

Keith

Martin W26/02/2019 10:20:41
785 forum posts
29 photos

Bill

You say that the type holder is subjected to repeated heating and pressure cycles. I take it that this happens when tools are used to fix the gold leaf or substitute on the book covers/spines, what is the typical temperature that the print holder is heated for this transfer process? I assume that for the smaller type holders the pressure is only applied by hand and not in some form of mechanical press. The reason I ask this is that Ian has suggested the use of adhesives and these could fail if the tool working temperature is high.

MartinW

Bill Phinn26/02/2019 18:42:34
161 forum posts
35 photos
Many thanks to everyone for the replies.
 
Jason, I should have mentioned (my post was already a bit long, as this one is!) that the steel back plate is only mechanically fixed to the brass channel (with five CSK M3 screws into blind holes), and of course regardless of how small my mill is I can do this mechanical fixing after brazing. So your suggestion to file out the rounded corners after milling is even more practicable - provided I have the skill to file perfectly flat and square. There's the rub - almost literally.
 
Absolute flatness of the long internal edge is critical everywhere except, in practice, in the corner where the side screw comes in; here there is always at least some projection of this screw into the cavity, meaning that no type or spacer sits directly up against the vertical side at that end. However, at the other end, a finishing spacer is always placed after the last letter of the word right up to the stop to fill out the chamber, so things here need to be perfectly flat and square, no ifs or buts.
 
For brazing I used Easyflo flux and this solder.
Hence, using Keith's suggested "455" looks as if it would reduce the flow temperature slightly, so it might be worth a go.
 
Martin, your question is a crucial one. The temperature at which the type is worked on the book is probably no more than around 150-180 degrees C at any time. However, the tool has to be brought down to this temperature after it is taken off the stove by damping it on a moist pad, and in practice, in trade binderies particularly, so-called "finishing tools" such as typeholders are left on the gas or electric stove for long periods, even all day, so that they are ready for use almost instantly. This means that they can reach quite high temperatures. As a consequence, using a soft soldering process is fraught with risk, and using epoxies probably even more so.
 
This is one of the reasons why bookbinding type is brass not a lead/tin/antimony mix, which is what I believe most letterpress (i.e. printer's) type is. I do use letterpress type occasionally in a typeholder (it is much cheaper than brass type) but you do have to be careful not to leave it on the stove too long, or it will distort or worse. What tends to happen first of all is that the pieces that get too hot start to expand upwards (they can't expand sideways because they're trapped in), and they then become useless because they are permanently of a different height from the rest of the type. This brings us back to the reason why absolute flatness and squareness are necessary for the chamber of a typeholder.
 
I think this project has shown me the limitations of having such a small mill. Once I've got an idea where I can put it, a proper-sized machine beckons.
 
ETA: Martin, yes, these sorts of typeholders are always used by hand and usually across the spine of a book. If they are used on a flat board (i.e. on the cover of a book) you do have to exert considerable pressure to get a good impression - sometimes, for bigger font sizes, with all the strength you've got.

Edited By Bill Phinn on 26/02/2019 18:51:05

Bill Phinn07/03/2019 23:29:59
161 forum posts
35 photos

I've now completed this project. I ended up hand-filing the long edge flat. I'd have liked to be able to make knurled thumb screws, not use bought ones of the kind pictured, but I've no metal lathe to knurl with (or do anything else with) at present.

The tool handle is made from a Magnolia that I planted 22 years ago and lopped some branches off last year.

Perhaps the newest aspect of the project for me was hardening and tempering the spring steel (sold annealed). My technique seems to have worked in producing the desired elasticity, but I'm slightly unsure what the optimum tempering method is for spring steel, i.e. what colour to look for in the steel. Some say straw coloured; some say blue. I veered towards blue without managing to retain it exactly in the finished look.

Thanks again for everyone's advice.

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David George 108/03/2019 07:53:49
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755 forum posts
261 photos

Hi Bill nice looking holder. I wondered if anyone had thought of heating the holder with electric heating elements. In the past I would have to make embossing dies for plastic parts and one for a wooden part. They had small heater cartridges some as small as 3mm diamiter and a thermocouple to controle the temperature. A small heater controller set the temperature for foil marking etc.

David

JasonB08/03/2019 08:13:00
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Moderator
15175 forum posts
1548 photos

Looks good, straight knurls are not difficult on the mill if you have a means to do basic indexing. I've done it a few times before I got some straight wheels for my knurl.

Bill Phinn08/03/2019 17:54:50
161 forum posts
35 photos

Thanks, David and Jason, for your comments.

David, yes, electrically heated typeholders are not unknown, but have always experienced a poor uptake among the binding fraternity. Factors against them are:

  • Cost: the last new one I saw for commercial sale about ten years ago was around £400, as opposed to £100 (at today's prices) for a typeholder of the kind I've made. Typically you would want to have several typeholders on the go at one time to hold all the words you're lettering with on a particular day.
  • Convenience: athough having the typeholder at the correct working temperature all the time definitely is convenient, having an electrical flex trailing off the end of your typeholder isn't. Anything that might interfere with the smooth motion of a typeholder across the spine of a book could create big problems; if at the first hit you stamp hot brass into leather in the wrong place (a mistake it's easy to make when accurate alignment of lettering or other tooling comes down to fractions of millimetres) it's very difficult to undo your error without starting again with new leather; and at around £200 a skin for properly tanned bookbinding leather, such errors can prove expensive. This steep learning curve is one of the reasons so few people nowadays even attempt gold tooling on hand-bound books.
Nick Clarke 308/03/2019 18:16:19
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215 forum posts
3 photos

Late to the party I know but …..

Firstly a nice piece of work you have produced.

Secondly have you considered roughing out the type holder and brazing it together then bolting it flat, not vertically on the miller table and using something like a large woodruffe cutter to finish the slot?

Sort of like this, but with the holder clamped down to the table

Not my image but all rights acknowledged


 

Edited By Nick Clarke 3 on 08/03/2019 18:16:41

Bill Phinn09/03/2019 13:30:24
161 forum posts
35 photos

Many thanks for your contribution, Nick.

One detail I didn't explicitly mention is that my current milling machine, a Proxxon MF70, accepts cutters with a shank diameter up to a maximum of 1/8", so I don't know that any woodruff cutter properly speaking would actually fit in my spindle.

Also, I'm not absolutely sure I've understood what you've proposed, but wouldn't passing the woodruff cutter along the channel when laid flat on the table produce radiused inner corners? Avoiding these was the main reason I wanted to be able to stand the channel upright for milling.

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