Drill press technique

[daccel]

Finished the wide pass by tapping the hole, filing down the opposite end to chuck it, then feeding the drill bit up from below through the bushings.

Not perfect alignment, but I think it will suffice. Accidentally drilled the wider hole too deep, so I will have to put in a bumper at the step to prevent the piston tip from stopping ammo feeding.

Slowly coming together .

[far_cry]

you did it. good job

so what for this valve ?
i think the o rings will get damaged from the holes ? maybe
and how you smoothed the hole that you drilled ?

[daberno123]

Looks very nice. Did you do that piston on the drill press also?

[daccel]

Thanks. It will be a hybrid that's just a bit different than usual. Not different enough to be contest worthy I don't think.

The o-rings should be fine, I filed the edges of the holes to round them slightly. Then wrapped fine sandpaper around the back of an undersized drill bit and polished it out. The smaller hole I drilled undersized so took a while to sand to the right size. The wider hole was drilled the right size for the o-ring so I was worried it would get sanded too wide, but it seems to seal.

Yes the piston was on the drill press as well. There is a thread on it a few down in this section.

[psycix]

Dude, that piston is made on a lathe... couldnt you also make this valve body on that lathe?

[inonickname]

Dude, that piston is made on a lathe... couldnt you also make this valve body on that lathe?

It's not, read his other thread.

Just for a bit of perspective, what will the bore size on this be?.. Just to help give an idea..

[daccel]

Dude, that piston is made on a lathe... couldnt you also make this valve body on that lathe?

It's not, read his other thread.

As he said. Or is this some humor from across the pond going over my head?

Edit: I realized yesterday that for the piston I could have just chucked the rod instead of drilling and tapping. Somehow had it in my head the chuck was 3/8 when it is 1/2 . Sometimes...

Well porting on the valve is 3/8". Originally I was going to use these 9mm fishing sinkers, but wasn't able to drill the back out for stability easily enough to be doing it on a large scale. So now I've switched to 1/4" bb's, with 5/16" brakeline for a barrel. Which makes attaching the barrel and breech stronger and better functioning. I will just have to push those bb's faster to make up for the lost mass 8).

It's cool how each problem seems to end up making it evolve for the better, I think it will be quite a bit different than my original concept sketch when complete.

[Technician1002]

I smell a challenge .

Wow lots to respond to, sorry if I leave something out.

I know I could use epoxy or separate parts, but I wanted to use a solid piece due to strength and size restrictions. I initially was going to sleeve tube and epoxy it in place, but needed a different size for the piston, and just wanted to do it right. I will probably still sleeve the thin walled portion with 1/2" copper couplers (it is 5/8 aluminum stock).

There was a lot of good suggestions here, but I thought I'd try the simplest with what I had at hand, and work up from there. I don't know what they are from, but my dad gave me these two short sections of thick metal tube from work a while back, and they happen to have a 5/8 inside diameter, so I was able to use them, with several diminishing sizes of tube inside for the drill bit, as bushings (correct term?). One will also form the outside of the valve eventually.

I left the bit (3/8") in the chuck, because it is only 1/2". The tube bushing kept riding out, and I didn't have any blocking under the stock, just held it by hand, but slowly managed to make it through. Shortened the bore hole to 3.5".

I think it may be as good as I will get without buying more stuff. It's off by .004" at the start and .014" at the cross hole. I suspect there may have been some luck involved . Still have to drill the wider pass, because it got too late (no I don't have a curfew, I just don't want to piss off my neighbours - joys of apartment living), so we'll see.

I'm still digesting all the suggestions and new stuff to plug into google, I saw some interesting sites earlier. I will post up some links later for future reference, or if this doesn't pan out on the second pass.

A picture is worth a 1,000 words. I hope this helps show how this will create a hole centered in the metal even if the bit is slightly crooked. If possible rotate the stock and clamp the bit. Try to re-create this lathe procedure.

Drilling the way you show, it will drill at an angle because it is impossible to get the stock in perfect alignment. It will drill at what ever error there is in starting.

Drilling the way shown below tends to be self centering.

1 Remove any point on the end of the stock to create a starter hole perfectly centered. A small bit wandered off center due to a bump in the center here. A big bit fixed it by making a perfectly centered depression.

2 Bore a pilot hole. Even with a slightly off align (angled or bent bit) the rotating stock will drill true if the center dimple is centered. If the bit wobbles going in, stop and re-do the dimple. This pilot hole has no measurable wobble when the stock was swapped end for end and the bit inserted in the other end. It is centered all the way through.

3 Drill to proper size. The larger bit will follow the pilot hole.

[daccel]

Thanks Tech, that was clear and helpful. I did as you suggested for the breech tube and it stayed perfectly centered over 3" after just eyeballing the bit alignment. Looks like you old guys may know a thing or two after all .

Tracked down some 1/4" bb's today.. definitely more heft than .177!

[Technician1002]

Thanks Tech, that was clear and helpful. I did as you suggested for the breech tube and it stayed perfectly centered over 3" after just eyeballing the bit alignment. Looks like you old guys may know a thing or two after all .

Tracked down some 1/4" bb's today.. definitely more heft than .177!

Works for making minature live steam engines.. Thought it would work for this.

[daccel]

How well do you think it would work on a much longer hole? Say a 24" barrel, for discussion's sake. It makes sense to me that the self centering effect wouldn't change, because the head of the bit doesn't know what depth it is at?

Yes, I know it would be easier to use tubing, but for the cool factor of wall thickness similar to a firearm 8). And I found my local Fastenal has lots of different stock at reasonable prices with specs, unlike that home depot crap.

My thought was to use an aircraft extension bit, with a rod attached somehow to give the necessary length. Or maybe a regular bit, with extension, because that would give more space for chips to build up before having to pull out. Could make a boring bit as you suggested earlier, but at first thought that sounds challenging when using a small diameter like 1/4".

Looked up D_hall's term 'gun drilling' and it looks like the same process of chucking the stock, not the bit. But the bit has a full length flute with oil or air pumped through the center to cool and remove chips. Not something I can construct on that small a scale.

[Technician1002]

How well do you think it would work on a much longer hole? Say a 24" barrel, for discussion's sake. It makes sense to me that the self centering effect wouldn't change, because the head of the bit doesn't know what depth it is at?

Yes, I know it would be easier to use tubing, but for the cool factor of wall thickness similar to a firearm 8). And I found my local Fastenal has lots of different stock at reasonable prices with specs, unlike that home depot crap.

My thought was to use an aircraft extension bit, with a rod attached somehow to give the necessary length. Or maybe a regular bit, with extension, because that would give more space for chips to build up before having to pull out. Could make a boring bit as you suggested earlier, but at first thought that sounds challenging when using a small diameter like 1/4".

Looked up D_hall's term 'gun drilling' and it looks like the same process of chucking the stock, not the bit. But the bit has a full length flute with oil or air pumped through the center to cool and remove chips. Not something I can construct on that small a scale.

The longer the unsupported bit length the less stiffness there is at the tip to guide the bit. Google search rifle barrel boring for more info. That length at smaller diameters is not an amateur project. Differences in temper, composition, etc can get a bit knocked off center where it won't self correct. Very thick wall tubing can be bored out larger. The original bore would guide the bit just fine.