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Robert D.

Tapered full tangs and drilling holes.

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Ok, so I have two large blade designs on hand, they will be made out of .250 thick 80CRV2 steel, and I want to give a go at doing tapered full tangs on them, but I have questions on the process to drill out the holes. 

Do you taper first and then drill the holes ( seems like the hole would NOT be straight if you did this ) or do you drill first and then taper ( which logically to me would make the hole going into the scales not straight. ) As these are LARGE blades ( 16+ inch OAL ) from very thick steel, I would like to cut down the weight as much as possible and going with a tapered tang seems like the perfect push to challenge myself with, I just dont know how to go about getting the holes to line up to where I dont trash a few pairs of scales before I get it right. 

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This is how I do it.  The example is for drilling holes for bolsters, but it's the same problem.

 

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Drill the tang like you normally would.  When drilling the scales, you can place shims underneath the rear portion of the scale to ensure that you're drilling perpendicular to the centerline.  To determine the thickness of the shim needed, measure the thickness at the ricasso, then the thickness at the butt.  Subtract the latter from the former and divide by two.  If the scale material is not of uniform thickness, you'll need to measure the difference and take that into account.

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I worked in a machine shop afternoons for a few months, first and only time I had access to measuring equipment that accurate, just have to trust my eye and fix the occasional mistake.

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8 hours ago, Gerhard Gerber said:

I worked in a machine shop afternoons for a few months, first and only time I had access to measuring equipment that accurate, just have to trust my eye and fix the occasional mistake.

A decent set of dial calipers aren't that expensive. You don't have to spend $100 for Starrett and they're super handy.

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Posted (edited)

You can do it either way. I prefer drilling first and tapering second. Drill before HT taper afterwards.

It also depends on the size of the pins you plan on using. Small diameter pins (3/32" or less) will make the bend quite easily. You said these were "big" blades, so you are using larger pins, I assume?

There are ways of fitting scales on with oversized tang holes as well. You just need to line up the holes in the scales and create front edges that also line up.

Like most processes, there are multiple ways to do it and achieve the same goal.

Edited by Joshua States

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ok, so what I was thinking of doing, which may or may not be a combination of the suggestions given, but is probably the easiest for me with my tooling is to do this. 

Drill the holes at full thickness, Harden and temper prepped blade, then temp glue the scales on and use spacers on the scale to where I can use a level to ensure flat on the tang surface and drill, rinse and repeat for the other side scales? Do I have the right idea with that? 

Honestly this makes sense to me I just was not sure I was going to be going about it the right way, and at the moment I cant afford to hose up a pair of scales so my other thought was to drill the smeg out of the handles and skeletonize them, but that is a TON of drilling and filing and I really dont want to go that route. 

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I have a pinned thread called "A Pair of Commissions". Check it out. Both knives are tapered full tang handles with bolsters. You can skip the bolsters, but everything else is the same. You will need some sort of clamp on the blade to use as a stop for the front edges of the scales. I use a couple of small clamps to hold the scales on while I drill the holes, not a temporary glue. Drill a hole, put a pin in. Drill another hole, put another pin in. Rinse and repeat as necessary.

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I have a file guide that would probably work great for getting the scales lined up for clamping, I have used it that way a couple times, but never on something that had a taper to it. 

Thanks for the suggestions everyone, I appreciate the help.

 

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Posted (edited)

when i had to do this, i first epoxied my over sized scales to the tapered tang. I then trimmed the scales parallel to each other on the bandsaw and drilled the holes. obviously this was all done post heat treat with a tang soft enough to be drilled through.

Edited by Chad Scott

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On 8/14/2019 at 2:38 PM, Shawn Hatcher said:

Drill the tang like you normally would.  When drilling the scales, you can place shims underneath the rear portion of the scale to ensure that you're drilling perpendicular to the centerline.  To determine the thickness of the shim needed, measure the thickness at the ricasso, then the thickness at the butt.  Subtract the latter from the former and divide by two.  If the scale material is not of uniform thickness, you'll need to measure the difference and take that into account.

Shawn's advice is one of the simplest, most effective ways to this.  I drill, then taper, and then make shims exactly like Shawn says above.  I even have a drawing on my dry erase board that I just fill in the values, and blam, I know what I need to do.  I clamp one scale at a time to the tang, glue the shim the on the side of the scale that will be on the drill press table, and drill through.  I always make sure my scales are uniform in thickness.  Here is the drawing from my dry erase board:

IMG-2799.JPG

 

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