site
contact
newsMore on drilling and tapping stainless steel
Before getting onto the main topic, a digression. I bought 25x5 mm flat bar, 2m length, from Bunnings. But look at the cross-section:
I have bought other sizes of flat bar from Bunnings (here in Australia) and it has been OK, true roll-formed bar. However, this 25x5 is guillotined off sheet steel, getting a cross-section curve in the process.
I don't have a car anymore, so had it delivered, along with some other steel. I am using it, but grumbling every time I see it. Really pathetic that they are passing this off as flat bar. Anyway, moving on...
I posted about setting up two garden sheds as mini-workshops:
"Setting up a home metal workshop"
https://bkhome.org/news/202511/setting-up-a-home-metal-workshop.html
I have owned that Ozito drill press for awhile, and it is OK, but only just. Cheap; it is listed at AU$139, but when I bought it, it was AU$129. So, a mini-review; what is there to like about it, and not to like?
The price is good. Negative points:
- Vertical travel is only 50mm.
- The base plate flexes.
- The motor stalls easily
The 2 inch vertical travel is very awkward; have to adjust the base plate frequently. That base plate, looks like the mounting onto the vertical tube is plastic; whatever, it flexes. I can feel it flexing when press down when drilling.
I have set the pulleys onto the second-lowest speed, and will
probably never go back to a higher speed. reason; the motor stalls
very easily. Especially with larger drill bits.
Today, wanted to drill 14mm holes in 304 stainless steel. I know that my hobby drill press will struggle, so went to the local Men's Shed and used their large floor-mounted drill press. Very nice.
Yes, AU$129 is a low price, but if you are planning to setup a workshop, it would be better to invest in a better drill press. Here is one that is sold locally here in Perth, Australia; just one that I found, don't know anything about it apart from reading the reviews:
https://www.totaltools.com.au/145607-detroit-550w-325mm-swing-bench-drill-press-detbdr550
...you would need to shop around, and it looks like a good drill press is about AU$550 upwards.
This is the 25x15 stainless steel that I drilled:
Drilling stainless steel, normal HSS (High Speed Steel) drill bits are OK, but they need to be sharp. I learned a lot from watching YouTube videos. A fairly low drill speed, plenty of lubrication, progress carefully so as not to overheat the metal.
I used a new 14mm drill bit, type HSSCo, which has 5% cobalt. The Men's Shed has a lubricant which is something green, a solution with mostly water. Perhaps even pure water would be OK. Or oil, but unsure about that.
A digression; that 25x15 stainless steel. At the time of purchase, looking online, I could only find those dimensions in stainless steel, although mild or carbon steel would have been OK. Certainly the latter would have been much easier to drill and tap. Today I was discussing this with one of the guys at the Men's Shed, and he recommended a vendor named DeCon, based in Sydney. Yes, I see they have 25x12 mild steel, and they will cut to whatever length I want:
https://www.edconsteel.com.au/store/sp/bfms.25.12
...good to know. But, using what already have, there is the challenge of tapping a thread into stainless steel...
I posted about attempting to cut a thread into the wheel axle:
"Meanderer trike wheel knuckle, take 2"
https://bkhome.org/news/202512/meanderer-trike-wheel-knuckle-take-2.html
The purpose of putting a thread on the end is to prevent the wheel from falling off. But, I mentioned, the left wheel really should have a left-hand thread. Probably ok if use thread-locker.
But, how do commercially-manufactured trikes do it? That is, affix something on the outer end of the wheel axle to prevent the wheel from sliding off? I already know the answer to that, as my prototype #1 trike is based on a cheap trike that I bought and converted to have front suspension. I still have the axles:
...a bolt right through! Pretty obvious really.
For the wheel knuckles that I have built, I used tube that I had in stock. Had stainless steel 16mm OD, 3.9mm ID, and aluminium 20mm OD 16mm ID. Also, they slid together nicely, and also the 20mm tube slide nicely into the wheel axle. Like they were made for each other. So went with those tubes.
However, in retrospect, it would have been better to have purchased stainless steel tube 6mm or 7mm ID and 20MM OD. Only one tube required, and a m6 bolt could go through, like shown in above photo.
Anyway, getting onto what I really wanted to post about; the challenge of tapping a thread into stainless steel...
Doing it by hand is impossible. I did it by using the drill press at the Men's Shed. This YouTube video shows how:
"Easy Way To Tap Threads With a Drill Press"
https://www.youtube.com/watch?v=2fTD6yvMbVE
...he constructed a handle to make it easy to turn the chuck. I will also make one, but before, just turned the chuck by gripping it with a hand; not easy.
There is vital information that you must know. It is very easy to
snap a tap. Lubrication is essential. But also, extreme caution
with cutting. I cannot emphasize that enough; it is very easy to
snap a tap. Over the years, I have done it a couple of times, and
that was tapping into aluminium. If it happens, you can't get it
out and the workpiece is ruined.
You rotate the chuck only about 1/4 turn, maybe less, then go back. When rotate forward, some tiny slivers of steel are cut, but then a backwards turn is required to clear those slivers. if you don't clear them, they can jam in the tap, and it will snap.
This video is very informative:
"Never Break Another Tap: The Complete Guide to Tapping Holes in
Metal"
https://www.youtube.com/watch?v=mwKloqgkgyo
Progress is very slow, but you do get there.
In the photo above of the 25x15 bar, there are 5mm holes where I will tap threads for m6 bolts. m6 with pitch 1.0mm, the recommended hole size is 5.0mm. However, some guys on YouTube recommend for stainless steel, make the hole 0.1mm bigger than normal.
I have ordered 5.0 and 5.1mm cobalt drill bits and m6 cobalt tap, and will wait until they arrive before tapping the threads. The thread that I previously tapped, in the wheel knuckle axle, used m6 HSS tap, used, so probably not as sharp as when new. It took a long time, as I was very worried not to snap the tap. The new cobalt tap should make cutting a little bit easier.
An observation about the chuck; the drill bit will slip, even
when tighten as much as possible with the chuck-key. However, I
consider this to be a good thing, as it lessens the likelihood of
the alternative; snapping the tap.
Hmmm, could have avoided these stainless steel dramas if had bought mild steel. Anyway, it is a learning experience, and having these excellent cobalt drill bits and tap will make cutting through mild steel in the future so much easier.
EDIT 2025-12-09:
Appending extra information, because it is important. The
YouTube link above, explains the advantages of specialized taps,
compared with the normal ones. He refers to a "spiral pointed
tap", also known as just a "pointed tap", or a "gun tap", see
photo from his video:
The local hardware store, Bunnings, only has the normal type, and they were the only type I knew of, until now. I have ordered a m6 pointed-tap from AliExpress:
https://www.aliexpress.com/item/1005003504618126.html
...from the specs, these are high quality; HSS M35 (5%) cobalt, also with TiCN coating. I had to look that up; TiCN is Titanium Carbonitride, see here:
https://www.surftech.com.au/coating-types/ticn/
...I will post a review after using it!
EDIT 2025-12-10:
I found a few vendors in Australia sell spiral-point taps. Such
as Hare & Forbes:
https://www.machineryhouse.com.au/t8306
...price AU$15.40 for m6. There are stores
in the capital cities, but if purchased via post, the postal fee
is AU$9.00
EDIT 2025-12-14:
Mentioned above, may need to spend AU$550 for a good quality
drill press. But, found this one that looks good; 600W motor,
80mm vertical travel, price AU$387 (plus postage):
...don't know how much they will slug for
postage. A bit more research, other vendors are selling it
cheaper; on eBay it is AU$369 and free postage, here. So,
shop around.
Tags: light