That shows commitment
I have been known to pinch the sunflower oil from the kitchen when stuck, it makes a hellish smell though somehow
Tap-Magic is the brand I have preferred and this afternoon received confirmation from a high end machine shop it is the best (in the opinion of the owner). I see Tapmatic mentioned above and it sounds similar but since he suggested McMaster as a source for a refill bottle and it comes up fast in their search I'm going to assume what was discussed is correct.
I also have Mega-cut and Brute brands but don't see anything truly outstanding about them. They are "all metal" cutting fluids.
The owner talked me into doing the tapping for 4 heatsinks myself suggesting first of all NOT USING ti-nitride coated taps for aluminum. He says it sticks (with Al). Second suggestion was using plug taper taps and just getting them from McMaster which I usually avoid because of costs but will choose for simplicity. I told him I wanted blind holes, so he said to start with the plug and finish with a bottoming tap. Also the suggestion of making a square block with a hole to start the threads. He has collets to use in the shop for the purpose.
I am unsure on which are the "plug" type and if I should spend over $17 each for ones made specifically for aluminum. The little M3 seem pricey. If anyone has other suggestions for a source of high quality taps please share or drop me a message.
There was a weekend a few months back where I broke three #6 taps. The first two were from Amazon, a Chinese brand with a name which sounds American. That was a bad choice on my part. The third was picked up from Home-Depot, again probably a Chinese import. The machine shop owner shook his head when I mentioned home depot. Snap-on does not have M3 taps in stock.
Being a high end machine shop which has all of the fancy toys I wasn't expecting the use of hand tapping but when I brought up a ratcheting tap handle he replied "I have a wrist", and the drill, nope, no feel. Only the most delicate for the best feel during cutting. If I follow those suggestions my joints will be hurting by the time I finish the chassis for 4 F4 boards and rework on a preamp.
I'll pay the machine shop to do the faceplates for everything once I have everything ready. A bit of a joke because I know there may never be a time when "everything" is how I want it and set in stone (or aluminum).
I also have Mega-cut and Brute brands but don't see anything truly outstanding about them. They are "all metal" cutting fluids.
The owner talked me into doing the tapping for 4 heatsinks myself suggesting first of all NOT USING ti-nitride coated taps for aluminum. He says it sticks (with Al). Second suggestion was using plug taper taps and just getting them from McMaster which I usually avoid because of costs but will choose for simplicity. I told him I wanted blind holes, so he said to start with the plug and finish with a bottoming tap. Also the suggestion of making a square block with a hole to start the threads. He has collets to use in the shop for the purpose.
I am unsure on which are the "plug" type and if I should spend over $17 each for ones made specifically for aluminum. The little M3 seem pricey. If anyone has other suggestions for a source of high quality taps please share or drop me a message.
There was a weekend a few months back where I broke three #6 taps. The first two were from Amazon, a Chinese brand with a name which sounds American. That was a bad choice on my part. The third was picked up from Home-Depot, again probably a Chinese import. The machine shop owner shook his head when I mentioned home depot. Snap-on does not have M3 taps in stock.
Being a high end machine shop which has all of the fancy toys I wasn't expecting the use of hand tapping but when I brought up a ratcheting tap handle he replied "I have a wrist", and the drill, nope, no feel. Only the most delicate for the best feel during cutting. If I follow those suggestions my joints will be hurting by the time I finish the chassis for 4 F4 boards and rework on a preamp.
I'll pay the machine shop to do the faceplates for everything once I have everything ready. A bit of a joke because I know there may never be a time when "everything" is how I want it and set in stone (or aluminum).
Jeffs,that man knows what he's talking about and I agree with everything he says. How do I know? About 30 years working in metal fabrication/machine shops,on the tools and in management. If you find quality tooling pricey, you'll find the effects of cheap tooling even pricier! Which is why I do not allow Chinese tooling in my shop. Buy good,buy once and no re-works. (and God help the guy I ever catch tapping with a hand drill
)
A "normal" tap has a tapered point and cuts approximately 6 - 8 partial-depth threads before reaching a full-depth thread. It obviously can not cut a full-depth thread to the bottom of a blind hole.
A plug tap has a blunt, squared end and only 3 - 4 partial depth threads leading up to a full-depth thread. In easily tapped materials and/or machines where the tap can be precisely aligned with the pilot hole, a plug tap can be used to start a threaded hole but it's more commonly used after a normal tap has started to thread a blind hole. If the blind hole can be drilled deep enough that the 3 or 4 partial-depth threads are located beyond the end of the screw or bolt intended to thread into the hole, no further thread forming operation is needed.
A bottoming tap has a blunt end and only the first thread or so is tapered. It can cut a full-depth thread to within one thread-pitch of a blind hole's bottom. It's used to form the last 2 - 3 threads of a blind hole, AFTER a plug tap has cut threads as far as it can go.
On the (very) few occasions when I actually needed a plug- or bottoming tap, I created my own by grinding the point off a standard tap. Using the grinder to square up the jagged end of a broken tap will also make an effective bottoming tap.
My local hardware stores carry taps by "Hanson" and "Vermont American". I don't know where they are manufactured nowadays, but historically I have been pleased with their performance.
Your machinist friend is probably correct that a good wrist is the most reliable sensor for operating a tap, though any hand-held tap wrench can't maintain the axial alignment as well as a good machine spindle and properly clamped workpiece.
Hand tapping is an artistic skill that takes years or decades to fully develop. After more than half a century of tapping holes on an occasional basis I don't think I'm nearly as good as my dad - who apprenticed as a tool and die maker before WWII. (And in shops still powered by a single large motor driving an overhead lineshaft, with flat belts powering each machine.)
- Practice a few holes on scrap aluminum items to develop a "feel" for the process.
- A good cutting fluid definitely helps.
- Occasionally I have had aluminum that tapped so easily, I over-advanced the tap and found it difficult (or impossible) to reverse the tap for the quarter turn or so needed to break off the cut chip.
- Since you are merely securing components to a heatsink there is little mechanical demand on the fasteners - so you may be able to use a pilot hole one or two sizes larger than the recommended tap drill. The larger hole is, of course, easier to tap because you are removing less material, though it may actually be more difficult to get the tap started straight.
(Some tap drill charts will actually list a range of sizes, perhaps keyed to percentage of thread depth. I think 70% - 75% is the standard, but 80% or more may be specified when strength is absolutely critical, or values as low as 50% to increase manufacturing throughput and make it easier on the assemblers.)
It is good to have the reassurances and suggestions from the previous posts.
It seems many of the brand names which I would have trusted just 5-10 years ago have moved production to China to keep the shelf price from increasing. I guess that is their main concern, not the cost to the consumer of rework.
I'm pretty sure it was the "Vermont American" off Amazon that broke on me but don't wish to bad-mouth them without being certain. I think they were Ti-N coated type which had something to do with the breaks. Those I broke without using a jig of any type. I was over confident in thinking I had done enough 304 stainless in my life this buttery (but sticky) aluminum would have the chips magically melt away. The third tap I broke on that frustrating weekend was from Home-Depot and suspect it would have been Ti coated as well. I was being very careful with work piece in a vise and not being too caffeinated but it broke while trying to break a chip backing out. I knew I was in trouble and tried to work with it carefully but it was probably the aluminum sticking to the coating meant to extend tool life on steel. Again, back to companies lowering quality to keep the first appearance tool cost low. There was nothing wrong with my technique when the last one snapped.
I had a stock of old taps, some of which were carbide I picked up on eBay about 10 years ago but never anything smaller than 1/4" and up to 1.5". That might still be a good source for old stock taps. Wow, feels like shopping for 6SN7's
What I was trained on a very long time ago and the first thing I tapped were expensive steel bicycle frames, and a few aluminum brackets on the carbon fiber frames using Italian taps. I had always wondered what idiot broke the very expensive taps on what must have been an almost as expensive racing frame back then. Maybe it was either someone with no idea of what chip cutting and clearing was, now I wonder if it was someone who had always done steel and was doing their first aluminum frame. Maybe they were doing a Ti frame...?
At this point I am dropping the metric 3 size in favor of #4-40. Wish Americans would have dropped their measurement system and sucked it up back in the late 70's. I see why there is resistance in the retooling costs and existing hardware. After building a preamp which came with #4 standoffs I ended up with hundreds of #4 fittings, threaded rod... so have an investment in the size and the taps are less expensive than metric in the US so here I am being guilty of doing the same.
I believe this size actually falls in the "coarse thread" domain and will go over a little on the drill size. Haven't added those to my care yet, or decided on the exact size. I have the "recommended" sizes in front of me but still reading up and when helpful tips land on this thread it helps a great deal. Most machinist sites only discuss mechanical tapping of holes using machinery I don't own.
Going over in size makes me think of using BLUE Loc-Tite (242) to help keep the MOSFET's tight against their insulators / heatsinks. Never thought about the effect of relatively high temperatures at those sites and not sure what effect the temperature increase will have on the ability to hold tight with over bored holes and now probably overthinking it with the fastener material being stainless steel and differences in expansion... I'll stop thinking now. Will try to be more concise in the future.
Here is what I have in my cart so far:
Tap-Magic (I should get a quart instead)
4-40 through-hole tap for Al(plug)
4-40 bottoming / blind hole tap for Al
Drill sizes not chosen yet, have a couple of pages up to look at when I get a chance.
It seems many of the brand names which I would have trusted just 5-10 years ago have moved production to China to keep the shelf price from increasing. I guess that is their main concern, not the cost to the consumer of rework.
I'm pretty sure it was the "Vermont American" off Amazon that broke on me but don't wish to bad-mouth them without being certain. I think they were Ti-N coated type which had something to do with the breaks. Those I broke without using a jig of any type. I was over confident in thinking I had done enough 304 stainless in my life this buttery (but sticky) aluminum would have the chips magically melt away. The third tap I broke on that frustrating weekend was from Home-Depot and suspect it would have been Ti coated as well. I was being very careful with work piece in a vise and not being too caffeinated but it broke while trying to break a chip backing out. I knew I was in trouble and tried to work with it carefully but it was probably the aluminum sticking to the coating meant to extend tool life on steel. Again, back to companies lowering quality to keep the first appearance tool cost low. There was nothing wrong with my technique when the last one snapped.
I had a stock of old taps, some of which were carbide I picked up on eBay about 10 years ago but never anything smaller than 1/4" and up to 1.5". That might still be a good source for old stock taps. Wow, feels like shopping for 6SN7's
What I was trained on a very long time ago and the first thing I tapped were expensive steel bicycle frames, and a few aluminum brackets on the carbon fiber frames using Italian taps. I had always wondered what idiot broke the very expensive taps on what must have been an almost as expensive racing frame back then. Maybe it was either someone with no idea of what chip cutting and clearing was, now I wonder if it was someone who had always done steel and was doing their first aluminum frame. Maybe they were doing a Ti frame...?
At this point I am dropping the metric 3 size in favor of #4-40. Wish Americans would have dropped their measurement system and sucked it up back in the late 70's. I see why there is resistance in the retooling costs and existing hardware. After building a preamp which came with #4 standoffs I ended up with hundreds of #4 fittings, threaded rod... so have an investment in the size and the taps are less expensive than metric in the US so here I am being guilty of doing the same.
I believe this size actually falls in the "coarse thread" domain and will go over a little on the drill size. Haven't added those to my care yet, or decided on the exact size. I have the "recommended" sizes in front of me but still reading up and when helpful tips land on this thread it helps a great deal. Most machinist sites only discuss mechanical tapping of holes using machinery I don't own.
Going over in size makes me think of using BLUE Loc-Tite (242) to help keep the MOSFET's tight against their insulators / heatsinks. Never thought about the effect of relatively high temperatures at those sites and not sure what effect the temperature increase will have on the ability to hold tight with over bored holes and now probably overthinking it with the fastener material being stainless steel and differences in expansion... I'll stop thinking now. Will try to be more concise in the future.
Here is what I have in my cart so far:
Tap-Magic (I should get a quart instead)
4-40 through-hole tap for Al(plug)
4-40 bottoming / blind hole tap for Al
Drill sizes not chosen yet, have a couple of pages up to look at when I get a chance.
I learned over the years to reverse the tap in that way as the tap would bind. I never thought about why so never knew...Your statement makes absolute sense to me...
in other words...
""Oh, thaaaats how it works...""
Thank you.
John
fine pitch suits very hard materials.
For aluminium, coarse would be my preferred pitch.
And to get the Thread strength make the engaged threads much longer than the thickness of the equivalent steel nut.
Try at least two thicknesses and three if the aluminium is thick enough.
i.e. aim for engagement length >> 2*bolt diameter.
As you advance the tap it sheers off a a small amount of metal from the workpiece, to form the thread being cut. The sheered chip, or shaving, builds up at the point where the tap is engaging the workpiece material. Eventually the chip will jam against the cutting edge of the tap that's forming the chip. Backing off the tap allows the chip to break off and fall into the flutes of the tap.
Dale
With respect to tapping fluid: I was using (and still do on occasion) Tapmagic ProTap. Unfortunately I suffer from an intermittent skin condition in my hands (Dr. thinks its psoriasis) which seemed to be aggravated by the Tapmagic cutting fluid. I switched over to coconut oil but that turns into a rock in my unheated basement during the winters and becomes difficult to use. So I mixed in just enough Avocado oil to make it more of a paste (I chose avocado oil because it has a very high burning point).
The combination seems to work as well as the Tapmagic fluid (at least in aluminum), it smells a lot nicer than the Tapmagic and doesn't seem to irritate my skin. YMMV
As to keeping the the tap vertical, I modified an old Dremel drill press stand to hold the taps. You can buy such things already madehttp://www.use-enco.com/CGI/INSRIT?PMAKA=318-0007&PMPXNO=953101&PARTPG=INLMK3 that are much better than mine but mine does the job. I was unwilling to spend the $150 for the better tool.
During my college days I worked in machine shops for three summers and tapped many thousands of holes holes on drill presses using a tapping head attachment on the drill press. (it was called Tapmatic). We were building very expensive, very high end surgical microscopes so quality and precision was kind of important. I never broke a tap using the Tapmatic. (sometimes they would wear out). Even at age 20 I think I would have destroyed my wrists if I had done them all by hand without the help of the drill press. Unfortunately the Tapmatic attachments seem to be in the vicinity of $600 so I am not buying one, but they worked great.
The combination seems to work as well as the Tapmagic fluid (at least in aluminum), it smells a lot nicer than the Tapmagic and doesn't seem to irritate my skin. YMMV
As to keeping the the tap vertical, I modified an old Dremel drill press stand to hold the taps. You can buy such things already madehttp://www.use-enco.com/CGI/INSRIT?PMAKA=318-0007&PMPXNO=953101&PARTPG=INLMK3 that are much better than mine but mine does the job. I was unwilling to spend the $150 for the better tool.
During my college days I worked in machine shops for three summers and tapped many thousands of holes holes on drill presses using a tapping head attachment on the drill press. (it was called Tapmatic). We were building very expensive, very high end surgical microscopes so quality and precision was kind of important. I never broke a tap using the Tapmatic. (sometimes they would wear out). Even at age 20 I think I would have destroyed my wrists if I had done them all by hand without the help of the drill press. Unfortunately the Tapmatic attachments seem to be in the vicinity of $600 so I am not buying one, but they worked great.
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