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Enlarging Bore of Short Tubing Sections - w/o a Lathe

HFS

Well Known Member
Here is a simple (and fairly accurate) way to enlarge the bore of short sections of tubing - maybe used as a bushing or something similar, without the benefit of the precision of a lathe.

This tip is only as good as the alignment of your drill press - if its off, the resultant hole will not be concentric with the o.d.

Make a wooden (ideally oak, maple or some other hard wood) holding fixture as shown in the photo.

Position the tubing section so that the bottom is flush with the bottom of the fixture, and tighten securely with the cross bolt.

Set the drill stop at slightly more than 1/2 the "thru" distance, bore to the stop, maintaining contact of the fixture with the press table.

Loosen cross bolt and push tubing thru fixture until drilled portion is flush with fixture face, re-tighten cross bolt, flip fixture over (un-enlarged end now up), and drill to "stop". This step is to minimize the built in "out of true" aspect of drill press.

The result isn't perfect, but may be good enough for the projected use.

If there is a need to have different bores at each end, maybe using the tubing as a connector for two different size diameters, bore each half slightly less than 1/2 the depth. This will generate a stop face between the two diameters.

YMMV

HFS
 

Attachments

  • Drill Jig - Enlarging Tubing Diameter .jpg
    Drill Jig - Enlarging Tubing Diameter .jpg
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David always has great ideas, and they work.

I've enlarged the bore of various short pieces of steel and aluminum tubes many times over the years. It usually goes like this:
  1. "That tube doesn't need much work."
  2. Grab a drill
  3. "OUCH. That burned my fingers!"
  4. Grab the pliers
  5. "Dang. That scored the exterior."
  6. Put it in a vise.
  7. "Shoot. That crushed the O.D."
  8. Go to the lathe, make a new piece, and do it right.

20/20 hindsight is always to do it right the first time. David's idea is a good way to do it right. Just make the tool, then make the part, and save time overall.

Thanks David
 
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