Manufacturing stepped bore pipe

jepa · Nov 30, 2016

Hello,

I'm looking for advice in manufacturing (several) stepped bore brass pipes as shown in picture. The problem is that I don't have access to CNC machines but I'm able to rent some time to work with lathe if needed.

I also have drill press at my garage so I was wondering if it would be possible to order custom made reamer that could produce the stepped design at once? I'm worried about if the tolerances would suffer greatly and if it's even possible to ream a pipe this long. Any recommendations?

Please be patient as I'm total beginner in machining. Thanks!

Cole2534 · Nov 30, 2016

That's a lot of steps. Gaging something?

atex57 · Nov 30, 2016

I would check with some of the outfits that grind rifle chambering reamers. A simple "D" reamer could be made cheap and easy.

Ed.

DDoug · Nov 30, 2016

Your drawing isn't complete without:
1. tolerance on each hole size.
2. concentricity of each hole to centerline/each other/outside dia.
3. length tolerance on each step.

Bill D · Nov 30, 2016

with a lathe it might be easier to make a mandrel and spin brass tube to fit.
Bil lD.

Limy Sami · Nov 30, 2016

atex57 said:
I would check with some of the outfits that grind rifle chambering reamers. A simple "D" reamer could be made cheap and easy.

Ed.

Possibly, but;-

1 A reamer over 6'' in length IS NOT be cheap, let alone having 11 diameters!

2 Cutting all those diameters in one hit is going to be a high torque operation, which will require great care to avoid breaking the tool, a nightmare to clear the swarf, and have every chance of the reamer veering off centre and / or chattering.

That said it's still a pig of a job and one I'd no quote!

But if I ''had'' to do the job ;-

FWIW 1 If it were me boring will be a nightmare, so I'd make a series of stepped reamers to do max of 2 diameters at once, with a series of guide bushes for alignment from the previously reamed hole.

FWIW 2 Unless for some unstated reason it HAS to be of that design? .....I'd find another way of achieving the required results.

JRIowa · Nov 30, 2016

OK, you want a brass tube with 11 different bores (all dimensioned in 10th) that's 6.8539" long. You would need a special boring bar that is stepped so you have sufficient strength to bore the 0.3349" bore on the far end.

You'd need a custom boring bar made for that. I would suggest Cline tool ClineTool
You'd need MBB inserts from Thin Bit MINI-BORE(R) Indexable Boring Tools | THINBIT(R) Kaiser Tool Company

Then you'd need to run on a fairly new (tight) CNC lathe with probably 6K RPM spindle. The bar would need to be indicated in. High pressure coolant would be very helpful.

I'd quote like this: 2 boring bars at $1,500 each. Box of inserts $200. Material $1,000 Gauging $2,000. First part $2,500. Following parts at $1,500 each. Engineering time $10,000

So, you send me a check for $20,200 and I can probably have 2 parts to you before the end of February.

It's going to take a lot of machine time getting the program perfect. It might take 10 parts before you have a good one. Each part would spend time on a CMM and then the program tinkered with.

I'm not as negative as some of these guys, I'm just expensive.
JR

art.h · Nov 30, 2016

It would be interesting to know the end use. If fluid or air flow there will be a lot of turbulence and if any great pressure (flow large to small) poor structural safety. If flow small to large then cavitation stresses and fatigue.. It would be better designed over a shorter length as venturi at one end of the item. Then a through drill small Dia. and a CNC or tracer lathe for large Dia. end

jepa · Nov 30, 2016

Thank you for all the replies so far. I'm sorry about inaccurate drawing. It is definitely missing a lot of needed information although I just made it to give people an idea what I am looking for.

It seems that making stepped pipe like this is way harder than I thought. I might have to think this twice before going into it.

The pipe is a part of the acoustic system and the chambers are determined by the nodal and anti nodal patterns in standing sound wave. To maximize resonance it would be optimal to build the pipe from one solid piece but due to it complexness I think I need to build it in 4 or 5 pieces and solder it all together.

Limy Sami · Nov 30, 2016

JRIowa said:
So, you send me a check for $20,200 and I can probably have 2 parts to you before the end of February.

It's going to take a lot of machine time getting the program perfect. It might take 10 parts before you have a good one. Each part would spend time on a CMM and then the program tinkered with.

I'm not as negative as some of these guys, I'm just expensive.
JR

That's all we need, some cheap skate hole in the wall shop underbidding the job :rolleyes5:

DDoug · Nov 30, 2016

jepa said:
I think I need to build it in 4 or 5 pieces and solder it all together.

Don't even bother with that.

Take the largest bore, add about 1/8" for the o.d. and make a "master tube"
in which you drop these bushings down into.

Take each bore size you want, bore the i.d., then machine the o.d. to that
master tube i.d.

You'll have a series of bushings, all stacked inside the master tube, retain with
solder or a circlip etc.

jepa · Nov 30, 2016

digger doug said:
Don't even bother with that.

Take the largest bore, add about 1/8" for the o.d. and make a "master tube"
in which you drop these bushings down into.

Take each bore size you want, bore the i.d., then machine the o.d. to that
master tube i.d.

You'll have a series of bushings, all stacked inside the master tube, retain with
solder or a circlip etc.

Actually that IS a brilliant idea! Thank you for this. This is something that I'd be able to make on a lathe myself and the end result might just work well enough for the purpose.

JRIowa · Nov 30, 2016

Limy Sami said:
That's all we need, some cheap skate hole in the wall shop underbidding the job

Cheap oil isn't good for everybody, that's why I got a buy-out. They have cut about 100 from the BU through attrition. Not much work. Besides, we used to make parts very similar to this in alloy 6.

I developed the process to take them from multiple parts to a single billet. The big ones were over 500mm long with 8, 20mm bores and 7, 30mm chambers. The small ones were 10mm bores and about 100mm long. Just loads of fun. The part that went inside was centerless ground and had 0.01mm clearance. The inside part was just 17-4 condition HH900.

It was all gravy, not much different than retirement. Just like yesterday, have to build a roller base for the neighbors table saw. That took a lot of engineering fluid.
JR

Oldwrench · Nov 30, 2016

You never did mention the size tolerances. Using four-place decimals everywhere implies a very high accuracy not practical to achieve. If the steps just need to be within .005 diameter and length it's not all that difficult, but still, you're not going to do it on a drill press.

Limy Sami · Nov 30, 2016

digger doug said:
Don't even bother with that.

Take the largest bore, add about 1/8" for the o.d. and make a "master tube"
in which you drop these bushings down into.

Take each bore size you want, bore the i.d., then machine the o.d. to that
master tube i.d.

You'll have a series of bushings, all stacked inside the master tube, retain with
solder or a circlip etc.

Damn, you ain't half clever uncle Doug

Cole2534 · Nov 30, 2016

digger doug said:
Don't even bother with that.

Take the largest bore, add about 1/8" for the o.d. and make a "master tube"
in which you drop these bushings down into.

Take each bore size you want, bore the i.d., then machine the o.d. to that
master tube i.d.

You'll have a series of bushings, all stacked inside the master tube, retain with
solder or a circlip etc.

Cut the bushings into a k shape and you've built a silencer.

jepa · Nov 30, 2016

Oldwrench said:
You never did mention the size tolerances. Using four-place decimals everywhere implies a very high accuracy not practical to achieve. If the steps just need to be within .005 diameter and length it's not all that difficult, but still, you're not going to do it on a drill press.

Yes you are right, probably not practical at all. The dimensions are only calculations but I think that chambers would need to be within .0005 to make it worth the effort. It should be very doable with constant measuring and "master tube" method that digger doug suggested.

magneticanomaly · Nov 30, 2016

The stack of bushings could be clamped from the end with a threaded plug, press-fitted, Loctited, soldered or brazed to make a structural unit.

Peter from Holland · Nov 30, 2016

magneticanomaly said:
The stack of bushings could be clamped from the end with a threaded plug, press-fitted, Loctited, soldered or brazed to make a structural unit.

Or just loctite them in a honed tube But I doubt he can hold 0.0005 on those bores Probabbly many of you can but OP has no experience in machining

Peter

jepa · Nov 30, 2016

I understand. I do have basic knowledge of working with lathes but holding within .0005 won't be easy. The good thing is that making bushings is pretty straight forward compared to one piece design I was first going to use.

I'm not sure if the lathe/enviroment that I could use is actually fine tuned to precision working and what's the quality of toolings available so I might as well ask a pro for a help. I have to pay money to get the job done anyway.

I think I have clear vision how to proceed from now on so thank you for all the help!

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