Accurately find barrel centres

[FormelyKnownAsSmashyPants]

Hi all, as the title says, is there an accurate way of finding the centre of bolter barrels, rhino exhausts and other stuff that needs drilling? Yes, I do use a range of sharp objects to make a pilot that all work well ranging from push pins, exacto blades and the tip of a round file, but placing that pilot in the first place is proving rather troublesome. Everytime I try and centre the pilot I just can't seem to get it dead on, and just last nite, I ruined a razorback I was working on because I :cuss ed the exhaust trying to drill them out

[Bung]

If you do it alot you could ask a mechanic to make you a tool for it on a lathe.

[Grotsmasha]

It really is just practice, but another step to add after the pilot mark, is to use a smaller drill bit by at least half to pre-drill the hole, this will stop the correct size bit slipping and sliding at all. So if you're doing 1mm holes, pre-drill a 0.5mm hole first, it is a lot easier to be more precise with the smaller bit :tu:

[Arkaniss]

Well, you're only human and you won't get it perfect each time! Here's what I do if that helps:

1. I make a very small and shallow mark at first
2. Then I line up the drill piece and eyeball it's position perpendicular to the barrel. If it doesn't look concentric to the barrel I adjust until it does
3. Start to drill *very* slowly
4. As more material is drilled into I repeatedly stop and withdraw the drill to check how it looks
5. Make adjustments as needed before the drill bit is fully engaged into the hole

Even if you've committed to the hole and realise afterwards it's not particularly accurate I've found I can poke a sharp knife into the hole and manually trim the barrel hole to even it up a bit. Just use the side of the knife and go slowly.

 

I've messed up a few here and there like everyone does. If it's on a rank and file model no-one is gonna notice ;)

[Rik Lightstar]

You could always go old school for a solution here, a steel ruler and a super fine point pen will let you draw a  pair of lines across across the end of the barrel and then aim your pilot hole where they meet. It'll still need some practice but if it's bothering you then it'd be worth the time.

 

Rik

[NTaW]

Grotsmasha has it: pre-drill a smaller hole after marking your starting point with a knife tip. This is standard practice when drilling holes into just about anything where you want precision.

 

If it seems excessive remember how off it looks when you're half a millimeter to the side :lol:

 

Edit: Also be sure to use a pin vise. It will take longer than anything powered but you will have far superior control for the scale this hobby is at.

Edited July 2, 2021 by NTaW

[FormelyKnownAsSmashyPants]

Grotsmasha has it: pre-drill a smaller hole after marking your starting point with a knife tip. This is standard practice when drilling holes into just about anything where you want precision.

 

If it seems excessive remember how off it looks when you're half a millimeter to the side

 

Edit: Also be sure to use a pin vise. It will take longer than anything powered but you will have far superior control for the scale this hobby is at.

I always follow these steps when drilling. I know about making a pilot divot and working from smaller to larger sizes of drill piece incrementally. I own several pin vices I use for pinning minis, but you can be off a little for that though if you make the hole slightly larger, as you can fill the area surrounding the pin with glue. It’s placing that initial divot that I find to be the problem. I’ve worked as a metal worker, both as a machinist and as a fabricator/welder in the past. I needed to be very, very accurate at times, and used to use metal rules, squares and even a tool for finding the centre of round bar, before finally making the hole with a centre punch, but the techniques and tools I used to mark out workpieces on the job aren’t really applicable on such a small scale unfortunately. Even though it’ll probably be a pain in the kiester as my eyesight ain’t what it used to be, I’m going have to try what Rik Lightstar suggested. I was just hoping maybe someone had come across some magical technique to do the job. Thanks for your suggestions all.

Edited July 2, 2021 by Captain Smashy Pants

[Xenith]

Place exacto across widest point, make slight scratch. Rotate 90 degrees and do that again. Point where scratches cross is the centre. Make indentation with exacto point (sharp). Pilot hole with 0.8mm drill. Drill with ~1mm+

[StraightSilver]

Place exacto across widest point, make slight scratch. Rotate 90 degrees and do that again. Point where scratches cross is the centre. Make indentation with exacto point (sharp). Pilot hole with 0.8mm drill. Drill with ~1mm+

This is what i do. I get a sharp, flat,  scalpel blade and press it down across the widest point. I don't cut, as that won't necessarily be straight, I push down with the flat of the blade. I then do the same from another direction and where the 2 lines meet I make my pilot hole.

[Arkhanist]

I have struggled with this exact problem for years - sometimes it works, sometimes the drill moves off-centre a little and correcting just makes it worse or even splits the barrel. Now I just 3d print bolters with the barrel 'pre-drilled', and it is SO much easier.

[FormelyKnownAsSmashyPants]

 

Place exacto across widest point, make slight scratch. Rotate 90 degrees and do that again. Point where scratches cross is the centre. Make indentation with exacto point (sharp). Pilot hole with 0.8mm drill. Drill with ~1mm+

This is what i do. I get a sharp, flat,  scalpel blade and press it down across the widest point. I don't cut, as that won't necessarily be straight, I push down with the flat of the blade. I then do the same from another direction and where the 2 lines meet I make my pilot hole.

 

 

cheers guys, that was the sort of idea I was looking for I’ll give it a go tomorrow and see how it goes.

 

 

UPDATE: Wow, I tried what Xenith and StraightSilver suggested on a Heavy Bolter, and I’m a VERY, VERY happy with the results I got. I still needed to correct a couple of times with a push pin after having made the initial divot and then with my smallest drill piece and my exacto knife once I started drilling my initial, shallow hole, but once I’d done that I was golden and was able to move up in drill size incrementally until I got the desired bore diameter. Like I said, I still needed to correct a couple of times, but actually starting from pretty much dead centre instead of just eyeing up where to put the initial pilot meant I could get results I was happy with. Before when I was guessing the centre, it didn’t matter how much I tried to correct because I was too far out from the beginning. Thank you all for your help, especially Xenith and StraightSilver.

Edited July 3, 2021 by Captain Smashy Pants

[Firedrake Cordova]

Now I just 3d print bolters with the barrel 'pre-drilled', and it is SO much easier.

That sounds a lot like cheating! :P :lol:

 

I ruined a razorback I was working on because I ed the exhaust trying to drill them out

Just thinking about saving the model ... are you able to fill the hole with epoxy putty and try again once that's dry..?

[FormelyKnownAsSmashyPants]

I made a real mess of it. I kept trying to use my file to even it up. A little bit on this side, but a little too much, and then a little on the other side but too much, and back and forth until I actually punctured the side of the exhaust from the inside out. But when life gives you lemons you make lemonade, I’ll practice my dry brushing on the hull, and use it for testing out colour schemes by painting it, stripping it and painting it over again for every time I start a new army and want to do a test.

[Firedrake Cordova]

Ouch, that sounds painful :(  If you've got access to a 3D printer, it looks like there's replacement exhausts on Thingiverse :) (or the Kromlech extra armour kit will hide it and is cheaper than a new Razorback :))

 

Otherwise, using it as a "learning tank" sounds like a good idea. :) The other obvious option is to turn it into scenery as a damaged vehicle.

[Cerberus1775]

I made a real mess of it. I kept trying to use my file to even it up. A little bit on this side, but a little too much, and then a little on the other side but too much, and back and forth until I actually punctured the side of the exhaust from the inside out. But when life gives you lemons you make lemonade, I’ll practice my dry brushing on the hull, and use it for testing out colour schemes by painting it, stripping it and painting it over again for every time I start a new army and want to do a test.

 

I wonder if you dont have a chance here to make up a bit of Lore for your Army.  " Today my young trainee you will be allowed to proceed through your training simulations on the weapon systems on a Razorback.   You are even more honored by being able to do that training in a Razorback that is held in great adoration by the Chapter.   See that exhaust that is battle damaged but old?   That was caused by one of the creatures of the warp who tried to swing their great claws at the Chapter Master as one of the foul traitors pulled it from the warp.  The Chapter Master using his relic, master crafted, power sword, gifted to him on the founding of the chapter cleaved the foul creature in two sending it back to the warp while it dragged the vile traitor  with them.   With their venomous foul leader dragged away, the enemy fled the battle like they did at the Emperors Palace all those years ago.  The Chapter Master decreed that to commemorate that victory the damage should not be repaired."

 

"Now lad get in there as I have talked enough and you have much training yet to do today."

[MegaVolt87]

I stuff it up most of the time so don't bother as well. Bit of black paint to do it instead.

[Grimoire]

Never ever use a straight pin or even a knife to make the mark. Why you ask ? Take a magnifying glass and look at the object and you'll find that they are not very uniform and can complicate the process. I use a pair of precision "Dividers". The points on these are high quality steel and extremely uniform in shape. Interestingly enough the old human eyeball is pretty darn good at seeing if your mark is concentric. Before drilling give it a good look and then start with a much smaller drill bit than you desire. Then reinspect afterwards before drilling the hole to size. Stepping up in drill sizes helps a lot too. If you doubt this try drilling a 1/4" hole using a pin vise without doing this and the bit can certainly wander.

 

Regarding the "X" method of finding the center. I'd never even try that. It requires far more precision in marking the lines than you'd think.

Edited July 3, 2021 by Grimoire

[jokaero weaponsmith]

Hey captain, 

 

you could try getting a  short k&s brass tube that fits snuggly over the end of the barrel putting a couple of other k&s brass pipes that fit snuggly inside each other inside that and then drilling down the centre of these, they should centre the bit.

As a fix for the exhaust you could  try https://www.zinge.co.uk/collections/vehicles/products/modular-military-buggy-vehicle-bits-forest-sprue

 

hope this helps.

Edited July 4, 2021 by jokaero weaponsmith

[NTaW]

^ that's a good one. You could also use styrene tubes if you've got them on hand.

[battle captain corpus]

To be honest it does end up just coming down to practise and practise.

 

If it helps you my find on some older sprues there is a small nub that’s on the side of the sprue, it looks similar in size to a Bolter muzzle. Practise on those maybe?

 

BCC

[Interrogator Stobz]

I'm with Grot,

 

Even after a Battle Company and a tonne more dudes I still do all this:

 

1. Stab center with thumb tack type pin.

2. 0.5mm drill pilot hole.

3. Stab Hobby Knife in to scrape to correct off center errors.

4. Drill multiple times increasing bit 0.5mm each time.