Brazing after milling whilst preserving accuracy

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?

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

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.

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

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.

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.

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.

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.

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

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

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

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.

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

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.

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.

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

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.