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I have a job where I need to solder a brass tube at a precision 90 degree perpendicular angle to a piece of round stock. My current idea was to use a spring loaded center to hold the tube upright at a precision angle for solder application in my mill.

It seems that the vice jaws and the base of the vice are enormous heat sinks which is obvious and I just can't get the brass components up to temperature with my small butane torch (all I have). I've considered using ceramic fiber insulation between the vice jaws and the base of the work, but I'm concerned that the fabric-like material will cause the work to not be held straight in the vice.

What are some options to overcome these challenges? Are there better ways to hold a tube at the 90 degree angle? Better insulating materials I can use?

I wanted to add a soldering tag to this question but one doesn't seem to exist and I don't have the rep to create one so I put it under welding at risk of being crucified.

Basic diagram of what I am trying to do

Actual parts

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  • $\begingroup$ You could also consider brazing instead of soldering. You get to use a gas torch in brazing. You could maybe use stainless steel liners. Those are quite a bit less thermally conductive. $\endgroup$
    – DKNguyen
    Commented Aug 22, 2022 at 18:25
  • $\begingroup$ I don't have experience with brazing sadly. I wanted to use solder because the joint needs to be relatively neat after it flows. I'm not sure if braze flows like that or not. $\endgroup$
    – Jake Henry
    Commented Aug 22, 2022 at 18:29

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Arranging pre-heat is almost a must.

I have done similar, where I have even used two torches to achieve the result needed.

So, either a second torch (my preference) or a bigger torch (easy to overheat), make sure both parts are clean and use flux.

I also made use of the kitchen oven (asked first though) but, one has to work quick as the heat goes out the open door, also working conditions can be cramped...

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  • $\begingroup$ Can you clarify what you mean by "arranging pre-heat" a bit more? A second torch might work in this situation because part of the challenge is I have to constantly keep moving my torch around to both parts and the heat instantly sinks away when I move it from one part to another. $\endgroup$
    – Jake Henry
    Commented Aug 22, 2022 at 18:33
  • $\begingroup$ @JakeHenry Presoak/Increase the ambient temperature around the piece somehow. Like with a heatgun running while you solder. Yes, of the entire piece somewhat. Your vise can handle being at 100 or 150C, right? Or even more? Maybe easier to preheat the piece before sticking it into the vise? $\endgroup$
    – DKNguyen
    Commented Aug 22, 2022 at 18:42
  • $\begingroup$ @JakeHenry I clearly mentioned a second torch and even suggested two compared to one large, so that is the arranging preheat. $\endgroup$
    – Solar Mike
    Commented Aug 22, 2022 at 18:45
  • $\begingroup$ @SolarMike Okay I didn't know if you meant something else in addition. Just wanted to make sure. Thanks. $\endgroup$
    – Jake Henry
    Commented Aug 22, 2022 at 19:02
  • $\begingroup$ @DKNguyen I do have a heat gun so I could try that as well. I can't pre-heat the piece before insertion to the vice because I need to precision aline the mill head over it to get the precise angle. $\endgroup$
    – Jake Henry
    Commented Aug 22, 2022 at 19:03
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I'll throw this in there because there are already a few answers. If you don't need extreme precision you could use some nice hardwood pieces as insulators. Wood has good insulating properties, and probably better dimensional properties than ceramic fiber.

If you need more precision you could perhaps buy some precision ceramic pieces from ebay or mcmaster?

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  • $\begingroup$ I considered buying ceramic plates from McMaster, but the pricing is way to high for the level of precision I'm after. The precision I need isn't worth $150 for a sheet of ceramic plate. I did see that they have ceramic washers for a few bucks a piece though so that something I will definitely look into if a dual torch arrangement doesn't work out for me. Thanks for the feedback. $\endgroup$
    – Jake Henry
    Commented Aug 24, 2022 at 14:03
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This looks like the easiest method.

  • mate tubing to surface and file to fit.
  • sand with coarse grit to accept solder
  • use plumbing solder and acid flux
  • lay the pieces over work surface to raise tube to exact height and loose heavy supports to hold in place, yet not clamped to transfer much heat.
  • heat joint in 5 seconds with micro-torch
  • remove flame and add solder, then reflow solder with heat for 1 second

https://www.youtube.com/watch?v=i4bUd8tl7-Y

I have use similar processes with liquid tin-plated brass foil hybrid shields with lids on PCB's.

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    $\begingroup$ I've done all these things except I don't think this addresses the requirement I have to solder at a precision 90 degree perpendicular angle. $\endgroup$
    – Jake Henry
    Commented Aug 22, 2022 at 19:12
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    $\begingroup$ did you notice in the video how it was supported by weak thermal restraints; nails. You would need a cutout in a 2x4 spruce piece supported to do the same thing so that it is square and aligned properly. A groove for the tube and properly spaced hole for the body. . For high volume use metal mold that is not clamped so it sits it position with weak thermal transfer. Essentially a simple jig. $\endgroup$
    – Tony Stewart EE75
    Commented Aug 22, 2022 at 19:40
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    $\begingroup$ Capillary action ought to reach around the tube with acid flux and the right amount of solder with an air gap around the joint. $\endgroup$
    – Tony Stewart EE75
    Commented Aug 22, 2022 at 19:50
  • $\begingroup$ Yeah a jig is definitely something I'll go for if I can't get it to solder with the multiple torch method while inside my vice. $\endgroup$
    – Jake Henry
    Commented Aug 23, 2022 at 12:55
  • $\begingroup$ It's an easy task without the heatsink and nearly impossible with it. $\endgroup$
    – Tony Stewart EE75
    Commented Aug 23, 2022 at 16:28

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