(Hobby) Threading taps for 1/8 inch  3.1mm  6061 aluminum. - Page 1
Forum section: electronics / general

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 26, 2022, 01:32:43 am
content: Thread sizes  : 2 * 0.4 , 3 * 0.5, 4 * 0.7So far I have been occasionally hand tapping with straight 3 and 4 flute taps with good results but the time is too long.Next project has many threads in emi shielded boxes, maybe over 100 .(While Hammond die cast could be used, I like making my own out of brazed 6061 angle)I need to replace all the old taps with machine taps.I can tap maybe half of the holes on the lathe milling attachment and then the others using a hand held battery drill.So far trials with battery drill resulted in tear-out on the entry side and good threads only in about 1/3 of thickness.I read that the "gun nose" and "spiral point" taps are good for thin materials, that push the cuttings forward. Some of these are expensive ( $25+ for a M3 tap !).Any comments about tap types for this will be appreciated, Thanks.

author: loki42
author_rank: Frequent Contributor
timestamp: August 26, 2022, 01:33:47 pm
content: Threads in aluminum are pretty weak usually. Is there a reason you're not keen on pem / press fit fasteners? I use pems, inserted with a pemserter but you can use hand tools or a basic press easily too. The inserted threads are then steel / stainless and take a second or two to put in. The fasteners are very cheap if you buy them from aliexpress etc.

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 26, 2022, 02:58:32 pm
content: Hi Locki,Thank you. I had not considered nut inserts. Initially enthusiastic, but need:M2, M3, M4 into Al of thickness 3.125 mm ( 1/8 inch)I have already purchased most of the 6061 in 1/8 inch thickness , about $60 so farSearch indicates M2 is available in "miniature self cliching" U-M2-1 series but max sheet thickness is 0.91 mmIt appears that with the longer collapsing rivet nut type, there is also a limitation with M3 and M4 not found for 3.12 mm sheet.I will continue searching.

author: jmelson
author_rank: Super Contributor
timestamp: August 26, 2022, 03:29:30 pm
content: Quote from: mag_therm on August 26, 2022, 01:32:43 amI do some hand-tapping in aluminum, but a LOT of machine tapping on my CNC mill. I use combination drill-taps mostly in the 4-40 size, that's between 3-4 mm diameter. I use Winbro AlumTap tapping fluid, it is AMAZING stuff, greatly reduces torque required. The tap portion of the drill-taps is essentially the same as a spiral FLUTE tap. That is a bit different from spiral point. Applying the right amount of pressure to start the tap into the work is important to get the first few threads to start with the right thread pitch. Of course, rigid tapping on a CNC machine always matches the advance to the thread pitch.Jon

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 26, 2022, 03:57:13 pm
content: Hi JM, OK,Travers does not have single qty AlumTap right now , but I can get a pint from Penn Tool.What brand of drill taps do you recommend?I am setting up lathe now with the metric compound gear, work held on milling attachment, to do some trials on scrap 1/8 6061 with the old hand taps I have.Should I just engage the leadscrew and run the tap in?Thanks

author: jpanhalt
author_rank: Super Contributor
timestamp: August 26, 2022, 04:16:13 pm
content: Try Tap Magic (https://www.amazon.com/Tap-Magic-10004E-EP-Xtra/dp/B07CMH961Z/ref=asc_df_B07CMH961Z/?tag=hyprod-20&linkCode=df0&hvadid=459707027954&hvpos=&hvnetw=g&hvrand=1251907393579981897&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9015391&hvtargid=pla-1040014408287&psc=1). I have used it for years. It lubricates well, which aluminum needs. I have known some machinists who use diesel fuel in a pinch.I suspect you have experience with 6061. It is quite easy to work, compared to softer alloys, and in my experience will hold a thread well. The trick is to get it started. With just hand tapping, it can be difficult to get a good first thread. I assume the holes will be through, not blind.EDIT: Just noticed that link is to the 4oz can. I always get a bigger can,

author: PartialDischarge
author_rank: Super Contributor
timestamp: August 26, 2022, 04:28:14 pm
content: This type of self clinching nut can be used in 3mm thick plates..https://catalog.pemnet.com/item/nuts-types-s-ss-cls-clss-cla-sp/self-clinching-nuts-types-s-ss-cls-clss-sp-metric/cls-m4-2

author: thm_w
author_rank: Super Contributor
timestamp: August 26, 2022, 09:00:14 pm
content: Here is a spiral flute jmelson is talking about:I don't know if a forming tap would work here, but it should give a stronger thread.PEMs are great although, to properly install them you need to drill a precise diameter hole, and use a press with a proper die.Careful with any sort of hand drill tapping that its perfectly perpendicular.

author: mag_therm
author_rank: Frequent Contributor
timestamp: August 26, 2022, 09:37:32 pm
content: Hi Thm_w,Jmelson mentioned combo drill-taps.Progress today:The Permserter Micromate has a price of about USD$500 on an Aussie site. A bit out of my range.I ordered 10 PEM nuts to see if a pair of dies can be made to press in the vice, based on the animation.Trial M3 by 0.5 and M2 by 0.4 threads were cut by headstock tap with the lathe leadscrew feeding , in and out. SAE 40 oil. The first thread on each was a bit butchered for half of a turn, not sure why. I expected a "tap snap" when the lathe went in to reverse (DOL start only) but it was OK.The remaining threads look good under the microscope, and the screw goes in nicely, less slop than my hand taps.If I can get a combo drill tap as JMelson uses, that will allow drill and tap without tool change, a big saving of time.Didn't find a M2 combo drill tap , TTC Travers have M3 & up, Titan start at M4.A photo of the lathe set-up for drilling tapping and milling of Al angles.https://app.box.com/s/a03l8ejw2yaqop8sl2lgpkl3ekaewvigThe idea is to drill the angles first then braze to form a box half, or a rack chassis (top level in the rack made of recycled wood)https://app.box.com/s/i0nz3v6iy9zd2nhqkac7qwlfbw3od9rvThanks for the advice.

author: thm_w
author_rank: Super Contributor
timestamp: August 26, 2022, 09:53:00 pm
content: If you are tapping on a lathe, usually you would have a floating element instead of using the leadscrew.Combo drill taps are convenient but seem to end up with a looser tolerance. Fine for most purposes though.They are commonly available on amazon/aliexpress for ~$1-2.https://www.aliexpress.com/item/3256804194200179.html

author: xavier60
author_rank: Super Contributor
timestamp: August 27, 2022, 01:22:16 am
content: I have used an m3x0.5 forming tap only on SS304 so far with good results. It causes the material to bulge slightly which might be a problem for some applications.Be aware that a larger drill size is specified for forming taps.

author: jmelson
author_rank: Super Contributor
timestamp: August 27, 2022, 02:02:00 am
content: Quote from: mag_therm on August 26, 2022, 03:57:13 pmI use whatever the macine tool supply outfits have. You have to feed the drill at a MUCH slower rate than the tapping rate. That is easy to program on a CNC mill or lathe, but would be just a bit tricky on a manual machine. In that case, I would feed the drill manually with the carriage feed handle, and then enage the threading feed. THEN, you have to stop and reverse the spindle before the tap gets all the way through.On my CNC mill, I do all this at 1000 RPM, but you would have to run it WAY slower to be able to react in time. Sounds like a nerve-wracking operation.Jon

author: jmelson
author_rank: Super Contributor
timestamp: August 27, 2022, 02:07:43 am
content: Quote from: mag_therm on August 26, 2022, 09:37:32 pmI have used generic press-in thread inserts with a bench vise to insert them, generally in 1.5mm (0.060") aluminum, but I have used them in 3mm (1/8") aluminum without issue. I always insert them such that the screw pressure tends to pull them in tighter. The diameter of the hole they are inserted into is fairly critical.Jon

author: langwadt
author_rank: Super Contributor
timestamp: August 27, 2022, 08:24:46 am
content: use a battery drill and dip the tap in ethanol, it stops the aluminum sticking

author: Kjelt
author_rank: Super Contributor
timestamp: August 27, 2022, 08:55:36 am
content: A few things you probably already know but might help.Your aluminium is very thin so should be clamped against flexing where you tap.Support block under or clamping in close vicinity is preferred.Aluminium pre tap drilled hole sizes should be a bit smaller than the standard for iron esp thin aluminium.So if guidelines for instance say for M4 tap pre drill with 3.2mm try 3 or 3.1mm might gove better results.After predrilling you are supposed to clear the drilling hole with a countersink, for aluminium you just have to shave slightly by hand, a machine might takeaway too much material. This helps the tap to set and prevents tear outI prefer blindhole taps from normal through hole taps because the cutted spiral comes out of the hole instead of down the hole. Makes cutting easier, not sure if this matters with this thin material though.You can indeed use ethanol, IPA or even lampoil for aluminium cutting but there are also special cutting fluids for non ferro materialslike aluminium. Not sure which onefor the usa that would be but for EU it is forinstance DORMER M200NR.2.If you have to do this for business like hunfreds a month it might be interesting to look at pneumatic or electric specialized tap arms.