Using chisels for turning brass

[Ulises Victoria]

My other hobby is turning pens. I have turned aluminum and brass with the same HSS tools I use to turn wood. If you follow standard safety precautions, is perfectly safe.

[tkay11]

Thanks, David. That's reassuring to know. I've ordered some 4mm brass rod that I can experiment with, alongside the ebony and boxwood that I've ordered. I have some very nice needle files (Klein, Swiss style).

 

Tony

[Walter Biles]

Tony, 

 

Nobody has come out and explained the difference between wood turning with hand tools, and metal turning.  if you are transitioning from a mini lathe with wood and tools, you might not realize it.  On wood tools the angle of grind on the cutting edge of the hand tool is very acute.  It is designed for working wood.  Another factor is that wood has grain and if the wood grabs the tool, usually it is the wood that will break out in stead of the tool being buried into the wood and yanking the tool.  With metal the cutting edge on the cutter is very near to square by comparison.  The tool is usually held in a mechanical anchoring clamp for safety and for a more stable angle of attack on the metal.  If the metal tries to chunk off the work, the tool is so well locked down, that it can very nearly not move the tool.  In that situation, the work has to give in shear or else take the edge off the tool.  That is the kind of grab that you would not want to be holding on to if your lathe has much power.  Does this help in understanding why a metal cutting tool usually is held clamped into a holder?

 

Also any kind of lathe work is best done with a full face shield in case something flys toward you that you would not want buried in some part of your face or neck.  I generally would use a helmet attached face shield with a more powerful lathe. 

 

Walt Biles

Edited March 13, 2014 by Walter Biles

[dgbot]

This may be true for regular lathe work. But we are talking watchmaking turning. This is done by hand and with engravers and files. There are no clamps.

David B

[tkay11]

Thanks very much, Walt, Brian and David. I had understood that metal turning was quite different, but had been interested by the video of the guy turning brass by hand. So I wanted to find out more about that and the tools required.

 

As usual with this modelling business, the moment I start looking at a new question I find there's a whole new world of experience, expertise and tooling. So I now hear about gravers, length of gravers, lathe speeds, grinding, grinding tools, use of files, sharpening methods (by hand or with tools), heels, faces, dangers, and a variety of possibilities in addition to some fascinating stuff about the world of engravers. All wonderful.

 

What I can see is that there is plenty of room for experimentation with suitable cautions.

 

Just a couple more questions (for the moment!). Brian (or anyone), could you let me know what 'slow' speed you use that is suitable for turning brass with a graver (in rpm)? It sounds like 200-500rpm would be good. Is that right? And what kind of gravers do you use? I have seen some hand gravers on eBay (see http://www.ebay.co.uk/itm/291056537288?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT) but suspect that the handles are too short and are designed not for turning but for engraving sheet metal. Would that be right?

 

Thanks so much for all the help I have had so far in answering what must have seemed to you pros a daft question!

 

Tony

[Per]

Here is one of the gravers i use on my Unimat 3 and my Boley watchmakers lathe. I pressed a bushing into the handle to hold a 1/8” HSS square toolbit.

I use handles bushed for 1/8” and 1/4” round and square toolbits on the Unimat, on the Boley mostly 1/16”.

 

The handle is about 80 mm long, enough to hold comfortably in the hand. The long handles you see on turning chisels are to make it easier to apply leverage for a heavier cut, something you don’t want to do when turning with gravers on a small lathe, a dead sharp graver using fine cuts is the way to go.

 

Start using a speed of around 200rpm, you’ll soon get the feel for the best speed for what you are doing.

 

Oh, and never plunge the graver tip into a cut, that is a surefire way of losing both the graver tip and whatever you’re turning. Angle the graver up (or down) and cut with one of the front edges.

 

Per

[tkay11]

Thanks very much, Per. Very useful. Just out of interest, and sorry for what must seem endless questions, what do you use to keep the graver dead sharp?

 

Tony

[Walter Biles]

Tony

 

I have not worked with the mini sized tools, I just felt it is better to know all you can before trying something. 

 

Walt Biles

[tkay11]

Yes, thanks, Walt. I was in fact grateful for your explanation about the different needs in tooling and should have made that clear. Before, I had just known that they were different -- you provided the very helpful explanation. And you're right. I'm doing the best I can to know as many of the ins and outs as possible to any new skill before I try it out.

 

Tony

[Per]

what do you use to keep the graver dead sharp?

 

Tony

 

I use a diamond lap (Eze-Lap?) and finish off with a hard arkansas stone. If you use a bench grinder like Bill Smith suggests in the Sherline article, there is really very little steel to remove afterwards to get the right shape. You can also search for "Scary sharp", there are many MSW members here that recommend that method for getting a sharp edge.

 

A bit off topic, but a great many years ago I watched a jobbing brass turner in Clerkenwell turn up a large telescope lens mount from a brass casting, completely by hand. The handle on his turning tool must have been two foot long. He jammed it into the armpit and leaned on it to get the depth of cut he wanted and the brass chips were flying. Next thing, he turned the inside threads with a chasing tool, finishing off the job by heating the machined casting, still rotating, with a spirit lamp and wiped on shellac. The whole thing can't have taken more than two minutes. But please don't try that at home! 

 

Per

[tkay11]

Thanks, Per. The Clerkenwell story reminds me of some local car mechanics I once knew at Lake Manyara in Tanzania. The road by them was often flooded (if you know the area the river was Mto wa Mbu, or Mosquito River), and cars regularly died as a result of foolish attempts at getting through -- sucking water into the engine. They could dismantle a car and knock a crankshaft back to straight using hammers and iron blocks, checking alignment by eye.

 

I use the Scary Sharp method for my wood chisels, but I have been a bit hesitant after reading about the variety of angles needed for graver bits. I'd probably need to practise quite a lot.

 

At the moment I've been turning some boxwood and have been very impressed with the result (not with my technique or the appearance, more the beauty of the wood and the way a sharp blade can be used so accurately for fine detail with this wood). So once I've learnt the skills with the wood lathe, I'll definitely consider moving to brass, using proper gravers and sharpening by hand.

 

Thanks again for the input. By the way, I didn't understand your commment "there is really very little steel to remove afterwards to get the right shape". Is that a good or a bad thing? What is the implication?

 

Tony

[Per]

I didn't understand your commment "there is really very little steel to remove afterwards to get the right shape". Is that a good or a bad thing? What is the implication?

 

Tony

 

Forming the end of the graver (about 60 degrees) with a bench grinder gives it a sort of hollow shape. All you have to do is hone it so the tip and edges are flat, leaving the hollow in the middle. Bill Smith:

Because of the curved surface caused by the bench grinder, the graver will rest on its point and its heel and neither the right and left corners of the square will be touching the stone. So, tilt the top of the graver slightly to the right until the point, heel and right corner of the square touch the stone. Now, make long strokes with pressure. (This is quite important. Two short strokes which total the length of one long stroke will roll the graver twice as much as the single long stroke.) Eight or fewer such strokes (usually five) should bring up the two right hand edges of the diamond face. Now, with the face flat against the stone, tilt the top of the graver slightly to the left until the left corner of the graver touches the stone. Make long strokes with pressure. Again, eight or fewer strokes should bring up the other two edges of the diamond face.

 

I like your Tanzania story. Amazing what a skilled workman can do with just hand tools.

In the early seventies, my Nikon camera died on me one time in Laos. The town watchmaker spent the night filing up a new gearwheel from brass sheet and fitted it to the camera motor drive. 

 

Per

Edited March 13, 2014 by Per

[tkay11]

We probably need to start another thread to document such lovely stories. Thanks for the info about grinding, Per. I'm just writing up my log to document my experience with rebuilding the cannon carriages and making the barrels.

 

Tony

[mtaylor]

Tony,

 

Just an FYI.... all the cannon on my Constellation (except the two deck Parrott rifles were made using a Dremel and files.  The Parrotts were done in lathe.  The only reason I used the lathe for them was because I didn't have one when I started making the cannons. 

[tkay11]

Very impressive, Mark! That makes me feel very lazy indeed.

 

Tony

[mtaylor]

Tony, I wasn't trying to do that...   I was pointing out that files will work.    

[dgbot]

Tony, I think what Mark is is saying is that brass turning is very easy to do and learn and that many tools to do the job.

David B

Edited March 14, 2014 by dgbot

[JPZ66]

One other thought about grainy wood..... I have often used basswood or balsa when making a pattern for casting, as they are easily and quickly shaped. After I have them shaped right, I soak them down with CA glue and the sand and polish them. Sometimes it takes a few applications of the glue to get the fill and a solid surface. At that point they are almost hard as rocks, but they polish well. A coat of primer to inspect for flaws and a final buff and they are ready for mold making work. To avoid getting glue everywhere, I mount the parts on pins or rods so I don't actually have to hold or touch the part itself. I have also used this process to make masters for vacuum forming masters for things like aircraft canopies. I find it cheap and easy to make masters this way.

 

Joe

[tkay11]

Thanks, Mark, David and Joe.

 

Mark and David: It's ok, I did understand. I just also thought it useful to reflect, as always, that there are often simpler ways to approach a problem, and that having a lovely toy such as a wood lathe can lead me to lose that search for simple solutions. I have much appreciated this thread of discussion as it really has shown lots of ways to approach the problem.

 

In order to practise working with this kind of detail on the lathe, though, I've already started with the cannon barrels by turning boxwood from an old ruler that I have. You can see the efforts if you want on my log at http://modelshipworld.com/index.php?/topic/335-hmc-sherbourne-by-tkay11-–-caldercraft-–-scale-164-1763-a-novice’s-caldercraft-sherbourne/?p=173630. It's headed 'Wheels/Trucks', but the barrels come at the bottom of the post.

 

I will also be trying with files when the 4mm brass rod arrives.

 

Joe: Your thoughts about balsa and basswood are really ingenious and useful. So now I have heard of perspex, balsa, basswood, ebony, brass and boxwood as substrate for the barrels, and I might well try each one of them just to learn. My next stage is to learn to make molds and replicate.

 

This is all enormous fun.

 

Thanks again, guys!

 

Tony