How to machine this?

[Steve355Participant @steve355]

[Steve355Participant @steve355]

Hi all

Feeling slightly guilty that I only show up here when I want something, but never mind.

Does anybody have any thoughts on machining the below part? It’s part of a template used for making sash windows. All of the curves are sections of a 1” diameter circle.

Machines available – small lathe, small mill, small horizontal mill and surface grinder. It looks to me mostly like a job for the horizontal mill, but I can’t find a quarter round cutter anywhere. Not sure if such a thing exists.

Thoughts welcome.

thanks

Steve

[JasonBModerator @jasonb]

As it is brass have a look at Ovolo router cutters meant for wood, the TCT ones will cut brass.

Failing that turn the profile on some silver steel, mill some teeth into it and then harden and use it like a milling cutter for the main sashbar shape.

The profile shown in the second photo could again be done with a home made silver steel milling type cutter or grind the profile onto an HSS toolblank and use the mill's quill as a slotting head to plane the profile, you could use a standard mill to remove most of teh material first

[Anonymous]

If you're only making one use standard cutters to remove the bulk of the material on the curves and finish the curves with files. One could always mark out and file a template in sheet steel if really worried about the profiles.

Andrew

[Gary YeadonParticipant @garyyeadon51936]

Good Evening Steve – What are you using the fully machined item for please?

Regards

Gary

[Steve355Participant @steve355]

Posted by Gary Yeadon on 20/07/2023 20:39:22:

Good Evening Steve – What are you using the fully machined item for please?

Regards

Gary

It’s a template for coping sash window bars, so a perfect mated joint can be achieved. The original I have is at least 100yrs old. probably more. I’ve been on a mission for a long time to make myself a set of traditional sash making tools that properly match. Finding a matching set is nigh on impossible, they’ve long ago been split/lost/discarded etc.

You put the sash bar in the groove and use a curved gouge for the coping – see pics below.

I’m thinking, probably, they may have been made by hand rather than machined. In the catalogue for the toolmaker there were numerous different sizes and profiles. But the finish and accuracy is very good, which is what made me think it may have been machined.

Perhaps I need to get practicing with a file!

[Anonymous]

Posted by Steve355 on 20/07/2023 21:08:30:

…finish and accuracy is very good, which is what made me think it may have been machined.

Much more likely to have been cast and then cleaned up, probably by hand.

Andrew

[noel shelleyParticipant @noelshelley55608]

Andrew has beat me to it ! I would cast them ! Noel.

[Steve355Participant @steve355]

Well, I have a little home made foundry. My casting skills are rudimentary at best but it would be fun to try. And it’s flat on one side, greatly simplifying things.

I imagine that making patterns for any profile would be dead easy for a shop making wooden sash tools.

[Gary YeadonParticipant @garyyeadon51936]

I must admit investment casting sprang into my mind that is one process to consider put forward earlier.

Another option would be 3d printing using a carbon fibre mix or use the file to fully machine from bar using a manual or CNC M/C you would need a file.

If you could send me scale drawing files I would draw up using my 3d software and send you the file foc

regards

Gary

[duncan webster 1Participant @duncanwebster1]

Big lump of brass, bore 2 holes at right angles using 4 jaw, then remove the excess with end mills. You could reduce the size of brass by bolting a sacrificial bit of something else to a smaller lump. The 2 bored holes are not in the same plane, so you need careful marking out.

[JasonBModerator @jasonb]

This is an example of the slotting option using the mill as you can see the two ovolo shapes of the sashbar are not far removed from an involute cutter so you could do it all like this.

Would also be possible to do it with a single point tool in a flycutter or similar holder, couple of moulding profiles including an ovolo being done here

[Martin ConnellyParticipant @martinconnelly55370]

As it is brass I think I would make it using a slitting saw and CNC on the mill. Finish with a small amount of filing and polishing if needed.

Martin C

[Michael GilliganParticipant @michaelgilligan61133]

I am not advocating purchase, but … this is interesting: **LINK**

https://www.scosarg.com/copenstick-glazing-bar-machine-sash-coping-station

MichaelG.

[JasonBModerator @jasonb]

For most people making at home the router (in a table) has become the weapon of choice with a range of cutters to do the profile of the moulding and also the cope cuts. Home made cutters similar to this would easily machine the brass Michael's link would be for small production runs, larger and the CNC has taken over many a moulding and cope machining operation.

Joiners shop where I used to work just cut the copes with a coping saw.

[SillyOldDufferModerator @sillyoldduffer]

Quite difficult, or at least time consuming, to make a one-off item like this with ordinary workshop tools. All change if enough of them are needed to justify making special tools, which could then knock them out at a gallop.

I agree with Andrew that the Victorian original would have started as a casting. Castings save time and metal, and these could been moulded a hundred at a time, or more.

I guess the cast blanks were squared off on a big grinding wheel and then sent to be hand-finished by drilling the fixing holes and cleaning up the edges by filing. The template's end profile requires a special file, which could be made from scratch or by grinding a standard half-round file in half. Perhaps a 'quarter round' file is a real thing?

Does anyone make their own files? From Silver Steel rod, shape and harden a sharp pointed chisel to raise a tooth. Then grind a length of Gauge Plate to the required profile, and raise teeth in it by dinging it with the chisel. Ding it many times, many many times… Then harden and temper.

The modern process would probably grind the template with a few profiled wheels. As grinding wheels are made from abrasive particles in a matrix, they can be moulded to any reasonable shape, so well suited to this kind of job.

Knifes such as these steak knives, often have often have complex profiles – these have curvy sharp teeth cut into a curved blade, and look bad on the table unless the set all match.

Knives used to be hand-made by master-craftsmen, and specials still are. Today, most knifes are ground in an automatic machine containing a high-speed profiled grinding wheel. When the profile wears below specification, a sharp diamond wheel engages and automatically re-profiles it. Items like Steve's sash window template could easily be produced by a grinding machine, but only if mass sales justifiy the high set-up cost.

Maybe a metal 3D-print service like this example. An additive process would have no trouble producing a sash template. Probably not cheap compared with DIY though – by definition our time is free! I'd mill from a brass block to approximate shape and file the profile. I think it's worth grinding a half-round file down to get into that corner with a safe-edge.

Dave

[Steve355Participant @steve355]

Thanks for all the thoughts and suggestions.

I know that there are modern ways to make window sashes, but 1) the original Victorian methods are fascinating, it’s a huge, lost industry and skill set, and part of our heritage and 2) go down to your local historic town centre and look at the quality of the original joinery on shop fronts, lawyers offices, pubs etc and it has a quality and beauty that far surpasses anything made these days on a router table or spindle moulder.

I’m pretty sure now that it was done like this. First, the shop obviously has the capability to sink the sash bar profile in a lump of beech. That’s no mean feat but perfectly doable by a plane workshop using a specialised “mother plane”:

to create the brass template coping end, a slice of this profile is cut, and the coping profile is simply planed onto the end using a “round” plane. And immediately you have a pattern for casting. Easy. The hard part is actually sinking the sash bar profile in the wood in the first place.

So I think I will have a go this, maybe in a couple of weeks because I have to make the tools to make the sash bar template. I’ve been looking for an excuse to melt some more brass for a while.

[Michael GilliganParticipant @michaelgilligan61133]

More power to your elbow, Steve

Do please keep us informed.

MichaelG.

[JasonBModerator @jasonb]

Not convinced they were cast but a shaper would have made quick work of it and would also have been quite capable of doing the longer beech stock too as wood a spindle moulder which were in use at the time

Edited By JasonB on 21/07/2023 12:22:10

[Anonymous]

Posted by JasonB on 21/07/2023 12:19:54:

Not convinced they were cast…

Look at the finish, pretty rough for machined surfaces.

Andrew

[JasonBModerator @jasonb]

Think I'd be a bit rough after knocking about in a joiners shop for 150yrs too

[John HinkleyParticipant @johnhinkley26699]

With nothing better to do while waiting for some material to arrive, I cobbled together this sequence of drilling/milling procedures to make something approaching what appears in the OP's photos.

Drill the holes then turn the piece on end to mill the large slot and "keyway".

With a milling cutter of suitable diameter, remove the area shown (left) and make a couple of blocks, using bolts to align, solder them to the main body.

That's how I would approach it, anyway, but sorry, that's taken up quite a bit of real estate in the thread. Mods feel free to delete it if you consider it wasteful of space.

John

Edited to try to get the photos side-by-side

Edited By John Hinkley on 21/07/2023 15:15:19

[JasonBModerator @jasonb]

As someone who earns a living from making sawdust it is worth pointing out that your typical Ovolo form as found on sash window glazing bars is not actually a 1/4 circle as it is longer than it is wide. Sometimes as shown below other times a 1/4 of an ellipse

Hence why I suggested making form cutters. John's and possibly Howards method assum it is an exact 1/4 circle.

 

Edited By JasonB on 21/07/2023 16:19:31

[Steve355Participant @steve355]

Posted by JasonB on 21/07/2023 16:16:20:

As someone who earns a living from making sawdust it is worth pointing out that your typical Ovolo form as found on sash window glazing bars is not actually a 1/4 circle as it is longer than it is wide. Sometimes as shown below other times a 1/4 of an ellipse

Hence why I suggested making form cutters. John's and possibly Howards method assum it is an exact 1/4 circle.

Edited By JasonB on 21/07/2023 16:19:31

That’s basically correct. The one I’ve chosen to be standard for my home-made tools is based on this sash ovolo plane:

Which has dimensions:

and the circle is 1” OD :

Which I’ve made #8 hollows and rounds to cut (amongst many others)

problem is, the Ovolo dimensions above don’t match the sash template I have, or various other related tools. Hence the need to make lots of tools.

When you consider that as Jason says, it’s an arc of a circle and not 1/4 of a circle, machining it all get more tricky.

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