Hole cutting by hand
For home tinkerers like me, precise hole cutting in stainless steel and titanium foil and thin sheet metal is not easy and it is particularly harsh on drills, ‘hole-saws’ and other rotary cutting tools. “My good drills never get used on stainless steel or titanium and I will instead use a punch.
If I need to use a drill, I use an ‘old-buggered-one’ that will almost burn its way through and be sharpened many times.
Such metals meet their match when they are shaped with high-speed abrasives and even slow speed aluminium oxide ‘sand paper’ or other abrasives.
This post is about a hole cutting method that can be done by hand with rudimentary and cheap equipment.
Simple hole cutting tools
A simple craft knife can be used to effectively on sheet metal for hole cutting without detrimental distortion of the metal sheet. Then the jagged edge can be precisely finished with a suitable abrasive.
The method is somewhat tedious and it may seem unlikely that a craft knife would be a match for hard alloys of stainless steel and titanium.”Believe me, it is just wonderful steel in these blades.”
In my experience, a single blade will perform several meters of ‘cutting’ and still remain serviceable. It will no longer be sharp enough for microsurgery or cutting anything much.
It becomes quite blunt but it makes a very effective metal piercing punch if kept exclusively for this purpose.
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Hole cutting method
Note: During my posts, I will refer to the easy grinding of cutting tools with abrasives disks etc. These are fast and convenient, but avoid the temptation of rushing the shaping. They should be used slowly with plenty of cooling by dipping in water, to avoid overheating that could spoil the ‘temper’ of the blade metal.
A craft knife with a sturdy un-segmented blade such as is shown in this link makes a good tool for the cutting or punching. It can be easily ‘sculptured’ with an angle grinder or Dremel Tool or similar to make it have a narrower profile in the cutting zone. This is useful when cutting tight curves.
There are also craft knives with segmented blades that are designed to ‘snap-off’ to expose a ‘fresh’ cutting tip as shown in this link.
They are somewhat slimmer and can have a narrower profile which makes a nicer/easier cut on a curve. However, their propensity for the segments to break off unexpectedly is not so nice. Consequently, I made a special handle/tool to hold a single blade segment to avoid this issue.
The tool can be used with gentle percussion or with simple hand force. It has lasted so well that I have never needed to replace the blade as planed. “Prepare for the worst and it will most likely not happen.”
The bottom line is that a simple blade will do the job.
I mark out the shape of the proposed hole cutting with a sharp scribe made from a concrete nail. Then with the blade, I punch a series of little linked slots just inside the scribe mark. Some slots do not connect to the adjoining one, but this does not matter as the uncut portion can be cut through later or just be broken by wiggling the cutout piece. “Avoid a ripping action as this can spoil all your good work.”
I do the punching against a soft piece end grain wood, for example, a portion of dry ‘clean cut’ willow branch, so that the punch blade and the bur or swarth can easily press into the wood. After a little punching, it will probably become locked in place by the protruding burs. This makes the precise punching very easy.
Please see the video below that demonstrates how the hole punching can be done.
Hole cutting finishing method
A DIY sanding cone as described in DIY hand tools makes an unlikely but effective tool to dress the ragged edges of the hole and to precisely and cautiously finish the cutting to the scribbled mark.
The above cones also work in a drill and can finish a variety of radii. However, a simple portion of pipe or wooden curtain rod etc that is partially coated with quality abrasive cloth by glueing will do in most cases. Damaged and discarded sanding belts are a great free resource for such quality abrasive cloth and the grits are much better than sand.
For this tool to be most effective, it must be used with the metal sheet supported on a suitable anvil. I place the ragged hole over the inside edge of the end of a piece of suitable solid ‘clean-cut’ pipe for support.
The metal edge can be systematically ground away by repeatedly rubbing the cone downwards with gentle force against the trapped edge. The cutting action although gentle is quite quick and satisfying and can allow a finish that can precisely follow a curved line that has been scribed on a metal sheet. A tight roll of stiff cloth-backed sandpaper or lighter paper that is wrapped around a dowel will suffice.
Tim
Hey Tim,
Thank you once again for an inspiring post. I am thinking to cut 40mm holes into a stainless steel oven dish and see how it goes.
As I’m living offgrid with very little electricity the handtool approach is most relevant to me.
Is there any chance to ask for a video which shows how to do this?
Best of wishes,
Huck
Hi Huck, Thanks for your comments. I will add a video of the cutting when I get time. Please note that I have tested two different sized biscuit tins now. The new big one does not work as effectively as the smaller original one. I have added this to the post. Be careful not to make it too big!
Tim