thread maker tool

[akis]

I would like to drill a hole on a heatsink so as to screw in directly M3 size screws without needing a nut at the other side. These tools are called "machine taps" or something like that, but I have no experience with them. The screws I am using are pretty standard they are listed as "M3 x 0.5mm pitch". I typically use a nut on the opposite end, but in this case I will not have access to the back side so instead of drilling a 3mm hole I need to drill a threaded hole to screw into it directly. Can someone tell me how it is best done?

[rob77]

2.5mm hole and use the set of 3 thread cutters - set of 3 to gradually cut the thread - you need to make 1 pass witch each cutter. and don't forget the oil ! you have to lubricate the cutters in order to avoid excessive wear. (ok. aluminium is soft, but anyways...)
there are also single pass cutters , but i don't like them - they are introducing much more stress to the material being cut.

[rob77]

forgot to mention - the oil don't have to be cutting oil (the one used when machining steel), i'm using silicone oil when cutting threads to aluminium, but any oil would do the job for aluminium (except vegetable oils )

so basically this is all you need:

[akis]

Damn I just bought on ebay a single 3mm thread cutter, did not see anything in "three parts" ?? http://www.ebay.co.uk/itm/331013438009?_trksid=p2059210.m2749.l2649&var=540232986841&ssPageName=STRK%3AMEBIDX%3AIT

Can I use vaseline or engine oil (synthetic) instead ? I mean we are talking less than a drop of oil right?

[Stray Electron]

  If the heat sink is aluminium, then don't use oil for lubrication. Use kerosene (paraffin to Europeans) or a lubricant that made for especially threading in aluminium. WD-40 also works well in aluminium. DO NOT use a  chlorinated solvent! It can react with the aluminium chips and WELD the tap into the hole! Clearance hole is typically 70 to 75% of the major diameter of the thread. Larger percent of thread size will be easier to tap but will take away a portion of the thread and the thread will be slightly weaker so the exact size of the clearance hole is an engineering decision but 70 to 75% is common. But charts giving the exact size to drill for each thread size are PLENTIFUL and easy to find. Look for "tap drill chart". 'Machinery's Handbook' is a great source for information like this! It's updated and republished annually and has been in publication since at least the 1920s. But to continue, if the threaded hole is a thru hole and not a blind hole (a hole that doesn't go through but has a bottom) then you only need a standard "starter" tap to tap it with. OTOH if you're tapping a blind hole AND you need threads that go as close as possible to the bottom of the hole then thread with a starter tap and bottoming tap.  Starter taps have a long tapered section which makes it easier to start them in a drilled hole but the bottom of them won't cut the tread to the full depth.  A bottoming tap has very little taper so it will cut full depth threads but they're difficult to start in drilled hole, so you use them after tapping with a starter tap.  They also make a "plug" tap that is a compromise of the two and has short taper.  But as I said before if your hole is a thru hole you can just use a starter tap and go in far enough that it cuts full depth threads all the way thru the material.

   OH and if you've never used a tap before, the secret to using on is to "clear" them frequently by reversing them and letting them "clear" the chips out of the hole.  If you don't then the chips WILL jam the tap and you may not be able to remove it and it will LIKELY break off in the hole! How often they need to be cleared depends on a lot of factors including how deep the hole is, how narrow it is and the precentage of material that was removed with the clearance drill hole. Tapping narrow, deep holes is very difficult and a lot of people break taps off in holes and it's actually a big sideline business in machining to remove broken taps!  It's also a LOT easier to avoid jamming taps in the hole can be a thru hole since the chips can fall out of the bottom rather than being jammed between the tap and the worked material. If your work or your part is critical then practice on some scrap before you try to tap your good item.

[Stray Electron]

Damn I just bought on ebay a single 3mm thread cutter, did not see anything in "three parts" ?? http://www.ebay.co.uk/itm/331013438009?_trksid=p2059210.m2749.l2649&var=540232986841&ssPageName=STRK%3AMEBIDX%3AIT

Can I use vaseline or engine oil (synthetic) instead ? I mean we are talking less than a drop of oil right?

     Link showing three types of taps:    http://www.kmstools.com/blog/hand-taps-proper-tapping-techniques/

     Any oil lubricant is better than none! Just don't use anything that's chlorinated!!!

[rob77]

the single pass tools are working well for threads not being overstressed, and honestly any transistor/IC package have a recommended/maximum tightening torque in the range of 1-2Nm, so no worries.
and yes we're talking about such a tiny amount of oil any engine oil (including mineral oils) will work well for small threads like M3. (just avoid the oils used for cooking )

[rob77]

@ Free Electron :

ad WD40 - what is that if not a mixture of oils and other additives ?
using oil for small diameters is ok for aluminium (otherwise please explain to all of my heatsinks that they should spit off the power transistors and erode to dust in a instant, and also explain to my threading tools that they have to jump back to the heatsinks and get stuck there  )

[KJDS]

For metric screws the drill diameter for a cut tap, as opposed to a roll tap, is the M number minus the thread pitch.

Take a small block of wood and drill a clearance hole through it to keep the tap square as you're using it.

put

mrpete222 tap

into youtube search and you'll get more advice than you ever need on tapping.

[rob77]

For metric screws the drill diameter for a cut tap, as opposed to a roll tap, is the M number minus the thread pitch.

Take a small block of wood and drill a clearance hole through it to keep the tap square as you're using it.

put

mrpete222 tap

into youtube search and you'll get more advice than you ever need on tapping.

the wooden block is a great tip for keeping the tap square  but it's even more important to drill the hole perfectly square to the surface (drill press is preferable here).

[tjb1]

forgot to mention - the oil don't have to be cutting oil (the one used when machining steel), i'm using silicone oil when cutting threads to aluminium, but any oil would do the job for aluminium (except vegetable oils )

so basically this is all you need:

Those 3 taps are the same tap...the different taps are Taper, Plug and Bottoming.  In softer materials you could really start with the bottoming and use that only as long as you start it straight.  Taper taps just have a much longer lead in to help start the tap parallel to the hole, plug are common as they are a compromise of both.

[Stray Electron]

@ Free Electron :

ad WD40 - what is that if not a mixture of oils and other additives ?
using oil for small diameters is ok for aluminium (otherwise please explain to all of my heatsinks that they should spit off the power transistors and erode to dust in a instant, and also explain to my threading tools that they have to jump back to the heatsinks and get stuck there  )

  WD40 is mostly kerosene. (And kerosene is an oil but a light oil unlike most thread cutting oils) Along with additives such as drying agents. But I've already said that it can be used when drilling and taping aluminium. In fact, it works rather well for that!  Most oils, particurally threading oils, are too thick and heavy and won't flush aluminium chips out of the hole very well.  Also the sulfur in regular cutting oil can react with aluminium and discolor it. For aluminium, I use water soluable oil (fish oil) that's made for machine work. But I don't suppose that the OP wants to have to buy a 5 gallon container of that!

  OP be generous with the oil, one of it's main jobs is to wash the chips out of the hole and off of the tap. Besides lubrication, it also cools the tap and work piece.

    Rob:   If your transistors are jumping off of their heat sinks perhaps your threads aren't what they should be! 

[ion]

... just avoid the oils used for cooking

Would be interested to know why.  I've used it to drill aluminium and it works well enough in a pinch.

[rob77]

... just avoid the oils used for cooking

Would be interested to know why.  I've used it to drill aluminium and it works well enough in a pinch.

i have a bad experience with a vegetable cooking oil - once my taping tool got stuck (haven't had other oil handy) but i was able to release it without any damage by heating the aluminium .

[Lightages]

Almost any type of oil will work. Just make sure you practice on a piece of aluminum you don't care about first. You just can't drill a hole and start screwing the tap into the hole. There is some technique and feel required to get good threads and not break a tap. Be prepared to buy more than one set of taps as 3mm are easy to break.

[ajb]

It's also helpful to use a countersink bit to put a slight chamfer on the entry hole before tapping.  Makes it easier to get the tap started, and reduces or prevents a bur from forming on the edge of the hole.

[SeanB]

With soft materials like aluminium you can also use a non cutting tap, called a roll or polygon tap, which makes the thread by deforming the material into the thread form without cutting chips. Makes for a stronger thread in the hole, but generally requires a larger drill size, and definitely needs a thread lubricant. If you are going to buy taps buy spiral taps, as they are stronger in smaller sizes, and cut better.

[kripton2035]

with aluminium, I directly screw the 3 mm screw into a 2.5mm hole
no need for one or even 3 taps or oil !!!
not the same in steel thought...

[rob77]

with aluminium, I directly screw the 3 mm screw into a 2.5mm hole
no need for one or even 3 taps or oil !!!
not the same in steel thought...

are you the Superman or Chuck Norris in person ? 

[kripton2035]

with aluminium, I directly screw the 3 mm screw into a 2.5mm hole
no need for one or even 3 taps or oil !!!
not the same in steel thought...

are you the Superman or Chuck Norris in person ? 

not at all. but just try it. if there is a hole of 2.5mm the screw itself is enought to make the path inside
really no need for a tap. in aluminium (or wood also) but not in steel

[SeanB]

If you are reusing PC mounting screws those are often trilobular self forming screws, which will form a thread into soft materials like aluminium and thin steel plate. No thread forming needed, just a nut driver to prevent stripping the head.

[robrenz]

I thought this was about a tool to start forum threads so I didn't even look until now

[rob77]

with aluminium, I directly screw the 3 mm screw into a 2.5mm hole
no need for one or even 3 taps or oil !!!
not the same in steel thought...

are you the Superman or Chuck Norris in person ? 

not at all. but just try it. if there is a hole of 2.5mm the screw itself is enought to make the path inside
really no need for a tap. in aluminium (or wood also) but not in steel

wood works for sure, i'm doing that myself as well but the aluminium... i'll give it a try ..... but a regular M3 screw is definitely not hard enough to do that sort of thing... are you sure you are not using self taping M3 screws ?

[rob77]

forgot to mention - the oil don't have to be cutting oil (the one used when machining steel), i'm using silicone oil when cutting threads to aluminium, but any oil would do the job for aluminium (except vegetable oils )

so basically this is all you need:

Those 3 taps are the same tap...the different taps are Taper, Plug and Bottoming.  In softer materials you could really start with the bottoming and use that only as long as you start it straight.  Taper taps just have a much longer lead in to help start the tap parallel to the hole, plug are common as they are a compromise of both.

those 3 taps are definitely NOT THE SAME TAP ! those are for progressive taping - you go with the "single strip first", then "double strip" and then the "no strip" each one is cutting he groove deeper and deeper. - to cut precise thread you have to do it progressively.

[KJDS]

I used to design big combline filters, typically held together with 100+ M3 screws, and we'd make 25000 a year of a design. I know a few things about screwing

You can force a standard A4 grade stainless screw into aluminium, but unless you drill the hole at 2.75 instead of the 2.7mm that you'd use for a roll tap then there's a significant risk it will snap the screw. By significant I mean more than 1%, which doesn't sound much, but when you're putting in 2.5million screws a year us a lot of rework. And with the hole drilled at 2.75mm you lose a lot of strength, risking stripping the thread when you tighten it.

You can use trilobal threadforming screws, These are more expensive then normal screws but the snap rate is about 0.2%. That is low enough to not worry the hobbyist, but would still have left 5000 items of rework a year on a single product.

Unless you need the thread going to the bottom of the hole, then a single tap is fine. There only needs to be 3mm of good thread to hold an M3 screw, if you can drill deep enough so that the lead of the tap is beyond the depth of the screw then it's pointless faffing about with three separate taps.

The other useful trick we used was to counterbore each hole, just about 2.5mm diameter for 1mm depth, so that any burr raised when tapping or extracting the screw would sit in the counterbore and not hold the lid off the mating surface. We'd use custom form drills for this.