mattmcl, Hi. I don't know why nobody else has simply told you what the correct tapping drill sizes are for M3 and M4 bolts. For the record, a 2.5mm drill is used for M3 and a 3.3mm drill for M4.
They'll do OK, but really, what you want to use for best tool life and prevention of metal deterioration down the road is a dilutable water-based system from a reputable manufacturer with a pH appropriate for the metal you're cutting. They're not terribly expensive and they are formulated specifically to give high reliability results. The dilutable machining fluids can be sprayed continuously during drilling, milling, tapping, and lathing operations. Since I formulate these for a living, I'll pass on recommending brands.😀
Vegetable oils are an incredibly bad choice. For one-offs, mineral based oils like the ones you mentioned will work OK, but are somewhat hazardous.
Sorry I forgot to mention the drill bit sizes. What I used for the M3 was the same as in your post, a 2.5mm but I think for the M4 I used a 3.2mm which was available to me at the time.
Hi Andrew. There's no need I think to confuse our American cousins who probably find it hard enough to deal with metric measurements anyway. As far as I am aware there is only one ISO standard for the pitch of metric "coarse" M3 and M4 threads and it is 0.5mm and 0.70 respectively. Metric "fine" ISO threads, as far as I am aware, start at M8 and get bigger and so need not concern us. If there are other non-standard thread pitches available in M3 and M4, I doubt that they are freely available in the USA.
You are of course correct about deducting the pitch from the OA dia but that only helps if the pitch figure is actually known by mattmcl.
You are of course correct about deducting the pitch from the OA dia but that only helps if the pitch figure is actually known by mattmcl.
"no such thing a fine or course threads in the metric screws right?"
Yes there is. As stated in my previous post. I have in front of me my copy of the "Zeus Precision" data chart booklet which widely used in the UK for thread data.
Yes there is. As stated in my previous post. I have in front of me my copy of the "Zeus Precision" data chart booklet which widely used in the UK for thread data.
any links?
at least the 3, 4. 5, and 6 mm bolts and nuts i use all come in their own pitches...
these are the sizes i use on my diy projects...
at least the 3, 4. 5, and 6 mm bolts and nuts i use all come in their own pitches...
these are the sizes i use on my diy projects...
Be sure to take your time and don't force the tap, they will break off easily. I recommend using some cutting oil like wd40 to ease the process. The HB needs a lot of holes tapped.
See this site Threads - Metric ISO 724
I was wrong initially as it seems that Metric "fine" threads do exist in the small diameters that we use in our projects. However it is the range of "course" threads that are freely available without having to resort to special order.
I was wrong initially as it seems that Metric "fine" threads do exist in the small diameters that we use in our projects. However it is the range of "course" threads that are freely available without having to resort to special order.
Seems my link was broken earlier. If you haven't tried wax you are missing out. Almost everyone I know who deals with cutting, drilling and/or tapping aluminum in the industry uses it. For a DIYer,, one tube will last a lifetime. The wax stays put and doesn't run all over the place, is very easy to store and cleans up easily. Here's a better link.
Rakuten.com - CRL Tube Wax Lubricant
Rakuten.com - CRL Tube Wax Lubricant
I think there is a mistake in that page.
It states that thread depth = 0.614 x pitch.
That ignores the radius on the threads.
Can anyone link to the standard that defines the different radii at the top and bottom of the male and female threads?
From memory, the male thread has a bigger radius on it's tip than the matching female thread has in the root.
Conversely the male root radius is smaller than the female tip radius.
I can't recall if that is 2, or 3, or 4, different radii.
This is to prevent the threads locking together at their tips and roots.
Feel the tap. It is not sharp at the tips. Each tip is radiused.
http://www.tribology-abc.com/calculators/metric-iso.htm
Shows 2 radii and one flat (at the tip of the nut)
The 3rd radii seems to be lost somewhere up around the H/8 dimension where the tip of the male thread does not foul on the nut root.
UN (Unified)
http://www.truthread.com/product-details/unified-thread-gauges
And a link to the pdf towards the bottom.
Shows 2 radii and one flat (at the tip of the nut)
The 3rd radii seems to be lost somewhere up around the H/8 dimension where the tip of the male thread does not foul on the nut root.
UN (Unified)
http://www.truthread.com/product-details/unified-thread-gauges
And a link to the pdf towards the bottom.
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I'm old enough to have learned metric in school- during a brief period of logic in the 1970's it was taught here. I also maintain two vintage Vespa scooters so I have the sockets and other tools. It's absolutely maddening over here because so many products are made overseas and thus are metric- you're forced to have two sets of sockets, wrenches, etc. Capitalism at it's best.
I can easily get M3/.5mm and M4/.7mm bolts and nuts, there is one remaining hardware store in the area that stocks them. Even stand offs!
To ensure tap perpendicularity while threading.
Make yourself up a guide block. by drilling a hole
through some flat faced material, a little less in thickness
than the tap length. Hole dia should be the same as the tap o/d.
Engauge the hole to be tapped by placing the tap through the guide block
into the hole and clamping the block in place. Squareness in now guaranteed
while you concentrate getting the threads started.
Make yourself up a guide block. by drilling a hole
through some flat faced material, a little less in thickness
than the tap length. Hole dia should be the same as the tap o/d.
Engauge the hole to be tapped by placing the tap through the guide block
into the hole and clamping the block in place. Squareness in now guaranteed
while you concentrate getting the threads started.