Help, please: Engraving Bronze

[grumpyphil]

Hi All-
I did some searches on this and didn't find much so I thought I'd ask. I've been practicing on steel and Stainless for the most part up till now. The other day, I turned a small container on the lathe out of 952 Bronze. I thought it would be fun to do a little practice cutting on it and found it to be a nightmare to cut. The graver just wanted to dive into the stuff or skip across the surface. Is there some trick to cutting it? Special geometry on the graver?
Thanks,
Phil

 

[Ray Cover]

I assume we are talking about rolled bronze and not cast bronze?
There shouldn't be anything inherently in the bronze itself that is giving you trouble. That stuff machines beautifully and should cut just as well.

I am making an educated guess here:

A couple things I would try is using a 45 degree face 15 degree heels on a point graver in the 90 -110 range on the belly. With softer metals you don't need the higher face angles and the lower face angle should give you a little more control (at least is seems to for me).

Another thought I had was this. If you are used to cutting hard metals (I am too) you tend to develop a habit of pushing just a hair harder than you should in both a forward or downward direction. When you go to a softer metals this can cause control problems. You have to consciously make yourself ease up on the pushing an truly let the tool do the work.

Like I said those are educated guesses but worth trying out. Without actually watching you cut it can be kind of hard to actually pinpoint where the problem is.

Ray

 

[grumpyphil]

Ray-
My guess is you are right on the money! I've been cutting hard stuff so much that it shocked me that Bronze could be difficult. I am sure it's a combination of what you've pointed out. I just jumped into it after 6 hrs of cutting stainless with the idea that it was going to be a piece of cake. I'll give it another shot in the morning.
Thanks for the reply!
Best,
Phil

 

[Andrew Biggs]

I just jumped into it after 6 hrs of cutting stainless with the idea that it was going to be a piece of cake

Try doing that with gold and see what happens

Cheers
Andrew

 

[jerrywh]

Go to a smaller handpiece. That is my advise. Keep a high face angle like 55°

 

[GertGraveur]

If it is the sticky stuff try using some oil.

 

[RoycroftRon]

I would guess that Ray is correct with the pressing issue of working steel vs the working the non-ferrous. I am constantly working on then the other and have to set it up in my mind that "this is soft stuff and this is not".

I find the steep angles are good for the harder (ferrous), but a 45/15 works great on silver, brass, bronze and the like.

 

[SamW]

I have been working on some cast bronze and it is not easy to cut into. It is not hard but has a brittle factor and the tool, whatever geometry I use, seems to have a hard time staying on track. Machine ability in a firm lathe set up is not the same as cutting free hand. If you need to cut the bronze then a stiff upper lip and forging ahead has worked for me. With the addition of some upright posts that are in the way of every cut I want to make it has been a tough excersize but the results are worth the extra time and expanded vocabulary.

 

[Ray Cover]

Anything cast is not fun to cut. I assumed it was rolled stock since he mentioned that he originally turned the piece on his lathe. Castings can have all kinds of unpleasantries waiting for you.

 

[grumpyphil]

OK guys, here's an update. I tried cutting this stuff again this morning with a 45/15 graver and a "soft material" mentality and it was the same horror show. The cutter either skipped across the surface or, when I got it to start taking a cut, it just dived deep and there was no stopping it. So I put it aside and went digging through my pile of scrap. I came up with up piece of Bronze from an architectural job I did a few years ago, stuck it in the vise and lo and behold, it cut beautifully no matter what graver I used! Note to self: stay away from 952 Bronze.
Thanks for your help and comments!

 

[Mike Fennell]

I had similar experience on a brass-framed 1851 colt replica. Mike Dubber recommended switching from a 120 to at 116 with 45 face, dubbing the tip and putting more downward pressure on the tip with my forefinger while keeping the wrist locked, as the graver wanted to skate or dive, and lubricating the tip often.

It was a learning experience. I needed an enhanced vocabulary course from Sam Welch.

Mike Fennell

 

[KCSteve]

I found I did better on soft brass with my GRS setting it for a slow stroke. The 'thunk thunk thunk' strokes cut through nicely while keeping it under control. If you set it right the GRS gets down to almost a hammer & chisel type cut.

 

[John P. Anderson]

Bronze is much different than brass to carve. I was confusing the two. Besides the traditional bronze there is also aluminum bronze. I mostly push grave and in my experience it's very difficult to control the tool compared to brass, copper, nickel silver, steel or silver. You either dive or skate. It's brittle yet soft. Annealing maybe helped but my stuff seemed to age harden quickly.

I equated it to trying to drive a Ferrari in an ice rink. Not that I've ever driven a Ferrari.

Bronze is used as a bearing because of it's low coefficient of friction. It does sculpt nicely but lettering almost made me hang up my tools. It was nice looking stuff that came out of a locomotive piston pin assembly. I said never again after the last plate. I do suspect if you carved it everyday it would go better.

Try a shallow cut with a sharp tool. I'm going to avoid it in the future now that I'm clear on bronze versus brass.

John Anderson
Havre, Montana

 

[tim halloran]

Grumpyphil: I think you may have gotten into some nickle silicon bronze, which is used for valve guides, bushings, and bearing inserts. it would probably be better to cut it with c-max or equivalent micro grain carbide. I Have machined a lot of it in lathes and it is not easy to cut even with carbide. Definitely use a good lubricant and dub the tip of your graver.

 

[monk]

if it was "free machining", as some call it, in your lathe-- should engrave ok. there is a species of bronze with a high silicon content that may pose a problem, but i've never cut the stuff. also, phosphorated bronze may pose a similar problem.

 

[tim halloran]

Monk: I didn't say it was free machining. Metals are rated by their machinability, excellent,very good, good,poor, very poor, etc. I would give nickel silicon bronze a poor to very poor rating. Most of the time i had to use, titanium nitride coated, carbide tooling. Index able inserts, with a fairly large radius on them.Even then it was no fun, and it could dull a high speed steel reamer.

 

[Mick]

Cast bronze can be a nightmare going from hard to soft and turning to sponge in the span of a few millimeters. Have had sucsess with Nu-Bronze, also called Jewelers Gold sheet available from most jeweler supply. Cuts a bit stiff, polishes great, made to mimic gold, reasonably priced.