Bolster-to-scale perfect fit

[Messinger]

Getting the bolsters and scales butted up and alligned perfectly with no gaps has been a big challenge for me. Do any of you use a mill (mini or otherwise) to get that perfectly straight 90 or 45 degree angle? I was planning on getting a disk sander as my next equipment purchase, but then I thought "I have a mini-mill. Maybe I should be using that." I haven't had it long and am still learning the basics. Until now I've been fitting scales to bolsters using sandpaper on a surface plate (so-so results, but slow) , my grinder platten (bad results), and files (inconsistent results and slow). None of these have worked very efficiently. I'd love to hear your methods.

Best Regards,
Ben

[Ray Rogers]

It's not so much what method you use as it is the process you follow and how well lined up you can keep the parts as you proceed. I'm sure you will hear many good methods before this thread is done but here are a few points from the way I do it.

First, the two pieces of metal that will be your bolster have to be kept aligned. To do this, I built a few of these simple jigs as shown in my folder tutorial at http://www.rayrogers.com/ftutor3.htm There are many other ways to clamp the pieces together but once you are set up for it this way is extremely fast and automatically assures the holes you drill are perpendicular to the face of the bolsters assuming the metal of your bolsters is flat.

Anyway, clamp the pieces together and drill the required holes. These are probably the holes for the pivot and the holes for mounting the bolster to the liner. Depending on you mill set up you may be able to mill the angle onto the bolsters without releasing them from this clamp. Or, you can use the holes to screw the pieces together and grind the angle on your grinder. The important thing is to use the holes to insure alignment and grind both bolsters at the same time.

Next, mount the bolsters on the liners. If your scales will be Micarta or other synthetic material the next step is easy, natural materials may require more care but that's just practice. Take a big piece of scale material and grind the leading edge until it matches the bolster. Then, using that same clamping arrangment, clamp the liner/bolster/scale assembly together. Check both the top and bottom sides of the bolster to make sure it is still in contact with the scale. Now you can drill through the liner to put screw holes in the scale. Once you can screw the scale to the liner you can mark the shape of the scale and cut away the part you don't need....

[Messinger]

Ray,
Thank you for your reply. I can always count on you and Don for great advice every time.
I'm not having any trouble with my bolsters - it's always the scales that give me heartburn.

Take a big piece of scale material and grind the leading edge until it matches the bolster.

That right there is where I always have trouble. I just can't seem to get a perfect match with any consistency. Usually the problem is a gap at a corner - like the mating face of the scale has gone slightly convex and one of the corners shows a hairline gap (might as well be Hells Canyon). Maybe I'm being too stingy with matterials and need to work with larger pieces of scale matterial at this stage so rounding a corner is less of an issue since more of the corner matterial will be ground away later.

Thanks Ray, and anyone else who want's to comment.

-Ben

[Don Robinson]

Hi, Ben. Where you been, Ben?

I grind the angle on my bolsters after profiling and fitting them to the liners. I take them apart and screw the two bolsters together, then grind the surface flat and square that will mate with the scales. This is while the two bolsters are fastened together. No scales, no liners.

Next I take the bolsters apart and grind the dovetail angle on each one using a sanding disk machine with a tilting table until the flat I made is all ground away. Grind a little, eyeball, grind a little until the first flat is removed.

When the dovetail is ground on each bolster, I mount each bolster on its liner and grind the end of my scale material until it matches the bolster dovetail. The scale is ground upside down on the same machine without moving the tilting table.

The next step is to mount each bolster on its liner, tap the rough scale material against the dovetail, clamp the parts together, then drill the scale mounting holes thru the liner and scale at the same time from the liner side.

After that take the rough scale off, tap the liner threads, drill the screw clearance hole thru the scale, countersink or counterbore the scale for the screw head, then assemble each liner with its matching bolser and rough scale.

Next, rough out the scale profile to match the liner.

Matching the dovetail without a gap is sometimes a pain, but it can be done. When you tighten the scale screws, snug them up and tap or hold the dovetail joint closed while you finish tightening the bolster and scale screws. Screws always allow a little mis-alignment, so you have to hold the bolster/liner/scale assembly together while tightening all the screws.

Hope this helps.

I use 15 or 20 degree angles on my dovetails.

[Messinger]

Thanks Don. You and Ray are the best. I can always count on you guys.
One thing I'm worried about... Working with scale matterial with an irregular top surface. The method you describe sounds like it would work perfectly for scale matterial that is square, but what about something like bark ivory or stag that has a curved or irregular top surface - you can't lay it flat on it's back to grind the dovetail or to drill the screw holes. I have a crazy idea but I'll wait until you guys respond. I think my idea will require pictures, as I don't think my words will explain my idea clearly.

Where have I been? Good question. I could give you 20 excuses but I'll just say I'm trying to get going again.

-Ben

[Ray Rogers]

You mention having the face of the scale go slightly convex on you. That used to happen to me (still does but much less often now). Two things that helped me with that issue: one, use bigger pieces of scale material when possible. If it goes convex at the end of the grind, then at least the end of the grind is far enough away that it doesn't mate with the bolster. Two, a very, very light touch. Let the belt do the work.

The odd shaped natural materials are more problematic. For me, it's a matter of grinding the mating face of the scale by eye until it sits the way I want it to against the bolster. Then, the scale, bolster, and liner are clamped together in that same jig only this time the liner is against the base of the jig instead of the scale material. The clamps are adjustable and will conform to the odd scale shape enough to make a secure hold. Then drill through the scale and the liner at the same time much the same as Don said. It is very easy to see if the scale and the bolster are properly mated before you drill with this arrangement. The one caveat is that it helps is the scale is shaped fairly close to the shape of the liner before you get to this point as it helps you decide where to place the holes you're about to drill. This isn't necessary with synthetic materials as in the earlier example because the liner is on top of the scale material so the outline of the handle is easy to see...

[pjelect]

Ben, could excessive heat build up on the scales be the problem? I use a small mill with a 5X7 tilting table that I set to 30 degrees. I lay my bolster and scale material on the table with the edges sitting off the top of the table a little then just run them past a mill. I haven't yet set up anything for scales that are not flat (stag) but I'm working on it. Anyway, this process gives me (to my magnified eye) a very good dovetailed fit. But on one knife in paticular the finished knife had visible gaps where none had been before. It took me four consectutive sets of scales on this knife to figure out that I was overheating the wood and causing the gaps.(What a revelation, eh?) The fourth set of scales were micarta and less suseptable to the heat and they came out very good.(that's when it hit me.) Anyway this might be something else to consider. Pat

[Jonathan]

This is what works for me.
Take your grinder platen and adjust it to a 30 degree angle. I use a degree angle indicator, bought for less than $6.00 at Harbor Freight. Using your grinder rest lay the bolsters and handle material one at a time flat on the rest and grind slightly until each are ground to the set 30 degree angle. I spray blue layout fluid on the ends, before grinding and when it is no longer visable, you have ground the ends to the desired 30 angle.
Be careful to match left bolster to left handle(mark with pen if desired) matierial, vice versa, etc. Bolster should (but not absolutely necessary) have holes drilled to fit liners before grinding, and may be oversized at this time. Leave your handle material oversized when grinding the dovetail. At this time, it is only important to match the two end together.
Attach bolster to liner with fresh ground dovetail, then slip ground dovetailed oversized handle snug into bolster, clamp, drill holes, counterbore holes, etc. attach with screws, grind handle profile.
Presto, a perfect fit every time!
You will find out in the near future that this is one of the easier things to do. Just think, once, twice, three times before grinding to make sure right bolster, goes to right handle, and which side is top and which is bottom before grinding the 30 degree angle. If you screw up, just redo it and don't let it worry you, after all they are just the unfinished profile. I started knife making less than a year ago, so I know how confusing it can be!
I started out by writing all my steps on paper and then reading and following the steps as I worked. I still made mistakes sometimes, but would make written notes of these mistakes to prevent in the future. It is like cooking, have a recipe for each procedure!
Just my .02 cents worth!
Good Luck!
Jon

[Messinger]

Thanks guys! Great suggestions and I'm going to try-out all of them. I'll report back.

Thanks!
-Ben

[titaniumdoctor]

The best way I've found to make a seamless bolster - handle joint, weather they're curved or straight is to spot the two togeather. Even if I cut both my handle and bolster dovetails in a sine vise, I still do a final spot to see if I have any gaps. What I mean by spot is, I finish my bolsters right up to final contour. The joint side of the bolster being the most impotant. That is your master. You will spot your handle material to that. You take what we call spotting blue, you can use pencil graphite if your worried about blue staining your handle material. Cover your joint line on the bolster with blue, and start pushing your handle material against the bolster. Whatever is blue, you grind........by HAND. No belt sanders here kids. When you get a perfect blue line running the length of your bolster on your handle material, you're good to go. Clean up, check, and drill your handle holes. Hope this is clear. It takes a while, but makes a seamless joint. Good luck yo.

[Messinger]

Jeremy,
Thanks! That sounds like a great technique for checking the joint fit. I'm all over it!

-Ben

[Don Robinson]

Good on you, Jeremy. I didn't figure there was anybody left in the U.S. who knows how to use spotting blue.

[Frank Niro]

Greatt fitting up there Jeremy! I do it much the same . You can make an excellent spotting material if you get yourself a charcoal sketching pencil - all charcoal that is - and scrap it with a knife and add a few drops of oil to make a mix that is paintable. Do not crush the charcoal, it will be too inconsistant and use an oil other than WD-40. Frank

[titaniumdoctor]

Frank, I've heard of guys using the pencil method, but have never tried it myself. I may have to, as I'm sure Don and any other tool maker (although few and far between it seems these days) knows, spotting blue can be pretty messy, and if you're using non stabilized wood it can stain it. One more little thing that works well when spotting dark colored scales, such as black pearl, the blue or charcoal won't show so well on the dark surface of the pearl. So if you go get yourself a bottle of white shoe polish and put a thin coat on the surface to be matched, you can pick up the transfer a little better. Make sure it dries before you take a hit on it, or your blue will smear. This is a great thread for the simple fact that in my opinion, having a good match between your bolsters and scales makes the knife. And sometimes it can be very tedious and frustrating to get that perfect match. So getting all you guys feedback for this issue is good. Rock on kids.

[Frank J Warner]

Originally Posted by Messinger

One thing I'm worried about... Working with scale matterial with an irregular top surface. The method you describe sounds like it would work perfectly for scale matterial that is square, but what about something like bark ivory or stag that has a curved or irregular top surface - you can't lay it flat on it's back to grind the dovetail or to drill the screw holes.

I solved this problem by building a simple jig and screwing, gluing or taping the scale to it.

The jig consists of two aluminum rails and a titanium "roof." The aluminum rails are maybe 1" high, 1/2" thick and 4" long. A 2x4" piece of 0.050" titanium is screwed to the top of these rails. Looks like an inverted "U" from the end. Everything is parallel.

Mount the flat side of your scale material to the underside of the titanium roof (the "ceiling?") using screws, double-sided tape or spots of superglue, so the scale is "upside down" but the flat is perfectly horizontal. Then rest the two aluminum rails on your tool rest or disk grinder table and grind the joint end.

-Frank