doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com CNC and Stockmaking

Found something similar to the video I was trying to find. The machine is a Bacci, Italian made. Jump forward to 1:30 for the side-lock carving.

https://www.youtube.com/watch?v=qRQQko2PU3Y

Dave, it�s not the ability of the machine tool to carve the wood.

The problem is the spring back when you remove material on the blank.

Highly figured wood is under all sorts of tensions, twists, and compressions, and therefore as you start to remove material things start to move around.

It�s not unlike trying to zero rifle with all the scope bolts being loose. Or only some of them loose.

CZ, I hear what you say and agree. But I'm not sure it matters whether a CNC machine or a chisel removes the wood. And the wood in this video isn't very highly figured.

Production wood blanks (if you see them anymore)
Are straight grained as string,and are cooked in a kiln until hard as concrete.

Not the same as cutting into a burl that's been in a hillside for 700 years. Drying in a shed for 10 years.

Everyone wishes it were.

The Sako stockwood supplier bared all about this on Woodnet some years ago. Quite a large volume consumer and military stock operation. Their operation requires kiln drying due to volume.
X % are scrapped out.
X% blow out after shaping.
X% break in use
X% warp and twist when forces are unleashed
It's built into the delivered cost.

Heated arguments ensued.
Machinists and hand stockers all chimed in.

Ultimately?

Figured wood is gonna move.
Don't go all the way in one shot.

Could you please respond to the above comment about how CNC carving results in movement in seasoned wood, but hand chisels are different. I've also always understood that there is a difference between kiln dried wood and seasoned air dry wood when it comes to stability. That is, that dryness is not the only reason to use seasoned wood. There are certainly lots of fancy grained stocks being hand carved without the necessity of additional inlettings and without apparent "springback".

Thanks for asking that question. I have the same thought immediately.



Exactly.

I am all but certain that Shiloh uses CNC with very little if any hand fitting. Their guns are easily the best factory made guns in the nation and their fitting has no flies on it.

It has a look like the cnc stock machining process could have gone quicker without as many tooling changes at least to rough out. I wonder if they're milling the wood in steps, though relatively quickly, with the thought to incrementally remove warping with the intention that less warping will remain as they approach machine finish dimensions.

I really can't see that it's too far down the road that a stock is milled off of the scan of an action. I'd think a smith could email a file to a knowledgable shop to machine a blank rather than needing to have the machinery in house. Maybe.

I can tell you for a fact that after duplication of fancy wood some rather amazing thing happens. I once had a buttstock that drifted down 1/4" after turning and inletting over a 3 month period of time. That wood was air dried and well over 10 years old. Lots of stress is relieved during the turning process. That said, I was in Japan in the 1980's and went to the Weatherby Factory and even then they had CNC machines for the frames and stock carving machines that could do 4 Athena stocks in a matter of minutes. Saw the same thing in the Merkel factory in Germany in 1997 when I toured the factory there. Final fitting was done by hand, but there wasn't much left to do by the stockmakers at the end. Interesting, in the case of both Germany and Japan, all checkering was done by ladies.

Just too many variables to be viable - i think the gunsmithing industry ( as in the traditional side of it ) does not employ many CNC experts in house who can make this process easy.. if you were buying a purdey would you rather buy one from someone who spends 5 hours calibrating their program to make your stock, or the bench hours of someone who is on a life time journey from apprentice through to a master craftsman.

Even if it did hugely cut production costs would that saving be reflected in their prices?
does purdey want or need to become more accessible? probably not, we see it often when big names produce a more budget friendly option, everyone just says its a sell out, its not true to the brand, its not a real purdey if the cnc machine is in italy...

would it be any better if the machine was in the uk workshop? probably not i suspect.

When it comes to restocking there are too many variations. the pantograph is only as good as your pattern, ive produced stocks for AYA boxlocks on my pantograph and they have come out fine my pattern is reinforced with a metal bar through it and turned on that shaft which gets rid of some flex, but my pantographs only capable of doing simple stuff and on such jobs i'd get there nearly as quick and with much more confidence with a sharp chisel

- i also wouldnt have to spend hours finding and building a scrap stock up into a viable pattern and risk ruing a blank when the duplicator decides it time to spit its bearings.

Last time when i priced up a hoenig its about 20,000 GBP or there abouts, one of the issues with a pantograph is that the pattern you are copying is flexible wood and it doesnt need to bend much to ruin the job, so you run the inletting out undersize and finish the job by hand; well by the time you have done that you may as well have just taken the worst out with a sharp chisel.

I had the same trouble with running a lathe duplicator where my wood handle pattern would flex and ruin the copy, so i turned a handle to copy from solid mild steel, if you combined a solid steel pattern with a rock solid duplicator you could get pretty close i feel, but then how many solid steel stocks would you need to mill and file out as patterns. If i were going to semi mass produce anything i'd make a pattern section of the inletting needed, and marry that up with a somewhat over sized try gun type deal, that could be mounted in the duplicator - you could probably run out pretty acceptable stocks in a couple of hours which would probably need very little to finish up.

When it comes to kiln dried wood some is better than others but most of it is awful, the modern over under guns all have horns that hold the head of the stock tight together on a slight draw, if you have ever hand carved any over under guns from solid it will amaze you how you can have solid bearings one day only to come back into the workshop to find its all twisted out on you and bearing unevenly. Kiln wood is a total pain in the arse, the best work will be achieved with a good air dried blank, it cuts and carves nicer for one, and is much more stable.

Just my ramblings worth.

People often ask me how accurate my pantograph is. It is not the machine but the guy running it. How you remove the material, the offsets you use for inletting and the amount of finish material to leave are all part of the learning curve. I always leave depth to finish by hand on the inletting and some extra on the outer dimensions. It takes a fair bit of time to run a pattern through my machine, I do quite a few roughing passes and sneak up on my final dimensions. I feel this technique works best to get a good semi-inlet. I also adjust my stylus diameter as I go using a smaller stylus the closer I am to final dimensions. How much I leave is dependent upon how confident I am in my pattern and who will fit and finish the stock. On stocks I plan on finishing myself I usually leave .015" in depth for the inletting and .060" on the exterior. Some stock makers use a steady rest on the pantograph to minimize deflection. I may build a steady rest and see if I like it but with very careful work I am happy with my results. They call stock making an art form for a reason. All of this takes time to develop skills. You can remove material by CNC or a pantograph the trick with both being leaving enough material to get the finished product you desire in a timely fashion.