Tough bolster!

[rhrocker]

I'm engraving a knife bolster (was a kit, don't have a name, brand, or make). The metal is very hard to engrave. Instead of a nice, shiny curl, I'm getting an irrregular curl, very ragged. The metal being removed almost seems to be grainy or powdery. I'm guess it's a hard stainless of some sort. I'm using a square graver with a 50 face, and 20 heal. Any idea as to what the metal may be, and if I should change the graver angles?

[Jamey Saunders]

I don't engrave, but it sounds like a cast bolster. Cast metals can be flaky like that. When they are heated up to melting, sometimes some of the parts of the alloy can burn off, leaving the cast metal's makeup somewhat different from when it started.

I'm sure some honest-to-goodness engravers will step up here and give you the exact answer you need.

[rhrocker]

I just found out more info about the knife kit: It's a SG4 Precision Game Hunter by Classic Knife Kits. It's a great looking knife, and the ad says only that the bolsters are stainless. I'm hoping to do justice to this knife, but the bolsters are tough ol birds!

[Tim Adlam]

Hi Robert,

Had the same experience with bolsters from a folder kit. I used a 45 degree face angle on the graver, highly polished. I put a micro keel on the graver and took light cuts to deepen the pattern dipping the tip in graver-lube occasionally. I think I went over it 3 times. It's best not to try for too much detail with this type of metal....Oh yeah...keep the rolaids handy!...

Hope this helps you with this project.

Keep us posted.

Tim

[Jim Small]

Robert

I don't know if Tim will agree....but it sounds like the bolster you are talking about is the DREADED 300 series stainless or 304 stainless to be exact. I can speak for most of us who cut stainless on a regular basis......I WON'T WORK ON 304 STAINLESS.
You spend 90% of you time sharpening tools and as Tim said taking enormous amounts of Rolaids.
Supriseingly, the stainless that most of us like to work on is a heat treatable stainless call 416....normally all stainless in the 400 series is what we like to engrave. I believe most firearms are made or now, cast from this formula. 416 is very pleasing to engrave and takes good detail. All this blabber doesn't solve your problem. If it were me I would take the bolsters ( if you can) to the nearest farm pond and deposit them about dead center.....then make some new ones. If this won't work for you do as Tim says go slow....You might try increasing the face of your graver to 55 degrees and keep the heal the same, 20 degrees. I found out recently that by looking at the fracture on the very tip of the grave under the microscope.....that the fracture would sometimes, not always, indicate the angle you needed to sharpen. Sounds crazy but most of the time I would correct the angle of the face according to the degree of the fractured tip. Normally this takes care of the problem. One other idea.....polish the heal to a high mirror finish and as Tim said use copus amounts of lube.
Remember, if anyone comes at you with 304 stainless, anything ,to engrave......snatch it from their hand....spin them around and put it where the sun don't shine.
Robert, When you get this project finished....let us see it.

Thanks for joining us

Jim Small

[rhrocker]

Thanks Jim, Tim, and Jamey. You were all correct. I emailed the knifes designer, Darrel Ralph, and he just informed me that the bolsters are "sintered" (don't know what that is) 304 stainless.
I'm about 1/3rd of the way through the engraving project, so can't stop now. Only been engraving for about three months, so I'm getting more of an education than I bargined for ) I kept the design simple as per Tim's suggestion, not much detail on this one. Next SG4 I do I think I'll have the knifemaker (Larry Crider, a great craftsman) change to some other material for the bolsters, as per Jim's suggestion. My power hone is sure getting a workout! Insiders tip: buy stock in Rolaids, should rise sharpely in the next day or two

[John McPherson]

IIRC, sintering is heating metal particles, then fusing under immense pressure. Used to make armor piercing slugs, among other things. No wonder its a PITA to work with.

[Tim P. Watson]

Yeah 304 is about as bad as it comes even when machining. The sintering doesn't help either. You might want to try a different cutting fluid. One thing about this stuff it will not cut worth a flip dry. It is not hard but rather stringy and tough. Try and find some TapMattic or Tap Magic, both are clear and do a pretty good job. If you can find an old can of either before they quit using 111-triclorethelene you will be even better off. I work in the medical industry and 304 has a first cousin called 316. Both machine about the same but the 316 is an implant grade. There is nothing good about this steel except it resistance to rust and it takes a good shine . It does not thread, turn, mill, drill, file or engrave well at all. You might try a carbide graver it you have one. If you don't it might be worth a try but the cutting fluid is very important with these alloys. There are some specialty industrial fluids but they are hard to come by unless you know someone in a machine shop or manafacturing faclity. Hangsterfers Hard cut works the best for these alloys so if you have a buddy that works some place like that see if they have some.

[gravertom]

I would agree with the carbide recommendation too. you will find this trouble with cast silver, brass, and gold at times. You just learn to be aware of what types of things are made this way, and what brands cut well, and which don't. generally, with jewelry, the less expensive the item, the more trouble you MAY have. Not always true though.

Also, how are you holding the bolsters? The absolutely most secure holding method(no vibration) is critical in this type of work too. It may not make much difference, but often times quality engraving, esp. on difficult jobs, is just a sum of getting as many little factors as right as possible.

Hope this helps. Keep up the good efforts!

Tom

[rhrocker]

Thanks all for the input! I'm considering changing out the bolsters with 416, as this 303 is beyond my inexperienced skills to sucessufully work with.
Tom, I'm using the GRS knife holder in my positioning vise to secure the knife. I did look at some of the forums archives on this subject, and think that some of the ideas presented there may work better than the GRS knife holder. I noticed that I have to re-tighten all of the set screws often, but then again I was using almost full throttle on my gravermax.
This has been a great learning experience, however I feel that I'm at the point to take Jim Small's advise, and look for a lake

[lgrif]

My only addition to the great comments already mentioned is to increase the tip from the usual 90 degrees to 110-120. It is a stronger point. Unfortunately it is also more difficult to control. Just what every beginner wants to hear. Sorry I didn't get a chance to introduce myself to everyone and see the outstanding work at Reno. I got tied up in gun guild business. I heard it was a great show. Well done and congratulations. Lee R. Griffiths

[Tim Adlam]

Welcome aboard Lee!

Hope you make yourself at home here and we look forward to seeing photos of your exceptional work!...

Tim