Question about cosmetic issue with pins in G-10

B

BlueBasiliskBlades

Joined
Feb 7, 2024
Messages
7
Hello all,

I’ve been a longtime reader of this forum and have learned a lot here but just recently joined myself. I was hoping to run a question by you folks. I tried to look it up first but didn’t see anything about it.

When I work with G-10 for handles, I often get a white ring or discoloration around some of the pins after grinding. I never really seem to have this problem with micarta, etc. I do use very slightly oversize bits (e.g., F size for 1/4”), but generally find this is the only way to have the pins fit properly. I use corby bolts on pretty much all of my knives, so the slight oversize doesn’t have any functionality issues.

Would you folks mind letting me know if you’ve experienced this and if you have any fixes? Thanks so much in advance, and my sincere apologies if I missed another thread about this!
 
The G10 is probably slightly cooked from the heat during drilling? Use sharp bits and low speed?
 
Thanks, Scaniaman. I actually thought this might be the problem before, but I’ve been using ice and water to cool during the drilling process and haven’t noticed a real difference. I use the lowest speed on my drill press, as well. In my experience, micarta burns more easily than G-10, but I’m not seeing the same issues issues with the micarta. My only current guess here is that it might be some form of minor chipping or abrasion in the minuscule gaps around the drill holes, since the g-10 holes alway drill out a little bit wider with the same bits as the micarta. If I’m off my rocker here, though, please let me know! Thanks again!
 
What pins are you using? Are you grinding them down with a fine belt? Pins heat up incredibly fast when ground, especially when a fine grit is used. I generally go course, like 60 grit almost to the handle. Then 180 to the handle trying not to be on the pin more than a second or two at a time. Once it's flush with the handle it's no problem. This is most important if you're using corby bolts. There's a lot of metal there and it'll get red hot. G10 fibers are fiberglass so they'll melt/burn and turn whitish brown when heated too much.

Eric
 
I agree with S Scaniaman . I am guessing this could be "blooming" from interactions with heat...likely from drilling the holes. G10 can scorch or discolor from heat and it's really difficult to see sometimes until finer grits are applied depending on the color of the product.
 
What ea42 said - If the pins are stainless steel, it is heat. Grinding down stainless pins can easily burn or damage the area around the hole.
Another cause could be grinding dust getting in the hole. A drilled hole may have a ragged entry-exit edge. The swarf could get pressed in this area or into the epoxy filling it.
Burned epoxy could also be an issue if the hole is too large.
 
Sometiimes the G10 will also break out around the hole. To prevent that, I drill a smaller hole from the back side of the scale and then drill the finished hole from the show side of the scale.
 
Here's a couple more things to consider. I can get that halo effect from peening. I believe it comes from fracturing the G10. Dunno if you do that, but something to consider.

Second, perhaps it's a dull drill bit or a little too much drill pressure when the bit comes thru. Those G10 fibers can come loose. I always drill into a sacrificial chunk of wood or aluminum under the slab with tight clamp pressure.

Just things to think about.

In the end I keep the slabs a little thick so I can grind it down a ways when this happens.
 
ea42 said:
What pins are you using? Are you grinding them down with a fine belt? Pins heat up incredibly fast when ground, especially when a fine grit is used. I generally go course, like 60 grit almost to the handle. Then 180 to the handle trying not to be on the pin more than a second or two at a time. Once it's flush with the handle it's no problem. This is most important if you're using corby bolts. There's a lot of metal there and it'll get red hot. G10 fibers are fiberglass so they'll melt/burn and turn whitish brown when heated too much.

Eric
Click to expand...

Thanks, Eric. I appreciate your thoughts. I’ve had this issue with pins of all kinds (stainless, brass, copper, but also even G-10 pins, which I would think are not as conductive and therefore susceptible to heating damage). I do use coarse belts and dunk in ice water, but I can try to be even better about this and see if it changes. Oddly, though, it’s almost never a full white ring… tends to be on one or two “sides” of where the pin is…

I’ve seen the heating issue directly only once with Micarta, when I wasn’t too careful with a bone colored handle and scorched a brown ring around a corby…

I guess the part that confuses me is why I don’t see this same thing happening with micarta and dymalux (I don’t use much natural wood), especially since those materials seem to tend to scorch faster on belts than the G-10.

In any case, I thank you again for your time and help!
 
It's a mystery for sure. Might be the drilling as others have said. That phenolic might be blowing out around the edges as the drill passes through leaving the fiberglass threads behind. They tend to fray and not cut like paper, linen, etc.. I usually clamp a thickish piece of micarta down under the drill and drill a hole through it using whatever size bit I'm using for the handle material, then use that as backing when I drill the handle holes. You can use a piece of hardwood too as has been said. It helps to lessen the blowouts. Works well on splintery woods as well. Also don't forget the pecking method to clear out the hot chips and dust as you drill. I've had issues with it myself though regardless of what I do. You can see a hint around the pins of this red G10. Those holes were countersunk after drilling and the handles were shaped after pinning and still it appeared:

Red G10 Jack.jpg

Eric
 
Stacy E. Apelt - Bladesmith said:
What ea42 said - If the pins are stainless steel, it is heat. Grinding down stainless pins can easily burn or damage the area around the hole.
Another cause could be grinding dust getting in the hole. A drilled hole may have a ragged entry-exit edge. The swarf could get pressed in this area or into the epoxy filling it.
Burned epoxy could also be an issue if the hole is too large.
Click to expand...
Thanks, Stacy. I occasionally have the issue with pins of all types in G-10, not just stainless (even G-10 pins, which are not very conductive of heat), so I’m guessing it’s more likely to be the ragged hole issue you describe. In any case, I appreciate the advice!
 
Sando said:
Here's a couple more things to consider. I can get that halo effect from peening. I believe it comes from fracturing the G10. Dunno if you do that, but something to consider.

Second, perhaps it's a dull drill bit or a little too much drill pressure when the bit comes thru. Those G10 fibers can come loose. I always drill into a sacrificial chunk of wood or aluminum under the slab with tight clamp pressure.

Just things to think about.

In the end I keep the slabs a little thick so I can grind it down a ways when this happens.
Click to expand...
Thanks, Sando! This is very helpful info. I use at least two corby bolts on all of my knives these days, so I generally no longer peen pins (plus, I often use colored G-10 or stainless pins, and those are impossible and tough to peen, respectively, as far as I know).

It could be too much pressure on the bits - I will try to to ease up further on that. I like using thicker scales, too (I use 3/8”, either whole 3/8” scales or my own two-layer 3/8” (1/4”+1/8”), so I can also try grinding down further on those before I fully shape the handles.

I appreciate your time and advice!
 
ea42 said:
It's a mystery for sure. Might be the drilling as others have said. That phenolic might be blowing out around the edges as the drill passes through leaving the fiberglass threads behind. They tend to fray and not cut like paper, linen, etc.. I usually clamp a thickish piece of micarta down under the drill and drill a hole through it using whatever size bit I'm using for the handle material, then use that as backing when I drill the handle holes. You can use a piece of hardwood too as has been said. It helps to lessen the blowouts. Works well on splintery woods as well. Also don't forget the pecking method to clear out the hot chips and dust as you drill. I've had issues with it myself though regardless of what I do. You can see a hint around the pins of this red G10. Those holes were countersunk after drilling and the handles were shaped after pinning and still it appeared:

View attachment 2489967

Eric
Click to expand...
Thanks, Eric! This is very helpful, and I will certainly try out the tips you mention. The results I sometimes get look exactly like what you show in your photos. Those knives (and handles) are gorgeous, by the way - fine work!
 
Thanks, Stacey. That’s certainly a possibility, and I will be more careful, as I always use epoxy, but the marks extend beyond the hole itself (where the epoxy would stay) and it only happens with G-10, so I’m thinking it’s a bit more more likely to be a chipping/tearing issue. In any case, I will definitely try your suggestions, and thank you again for your continued help! I’m very grateful to all on this forum who contributed!
 
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