Help Finding a Specific Tap...

[Old Hippie]

Here's one for those of you who know machine/metal work better than I do...

I am trying to revive my "Lock-A-FOCS" project. Basically this is a small modification to allow for a screw to be inserted up from the bottom of the handle to jam against the end of the threaded stud on the cap, once it's screwed into the handle. The intent is to allow for opening up the razor just a little in a safer and more secure way. We've lately seen @Clouds and @Tanuki displaying the fruits of their labours during the OCtober thread.

Last time I tried that with the FOCS the handle was too loose and things got a little frightening tout suite.

The FOCS seems like a good fit to the project, as the ferrule at the top of the handle is through-drilled and the handle is hollow. That ferrule is just a millimetre or so longer than 7/8" -- why they needed a ferrule that long I don't know; further I can't fathom why they didn't run their darn tap all the way through. But no matter. If I can source the tool I can do the work.

There's a lot about taps I never had to know. This allows me to be open-minded. The tap needs to be M4.5 x 0.75 thread pitch, and I'd want the "length of cut" to be at least an inch/2.5 cm to allow for getting good threads all the way down. I've got a standard length tap in that pitch and it "shoulders out" before it can cut all the way through.

I have figured out that a "deep hole" tap is likely not what I want, as they seem to be standard cutters on longer shafts.

So there it is. I would like a couple of things: what that specific style of tap is called, so I can sound knowledgeable ; and a source that is either in or ships to Canada. Thanks in advance for any insight or assistance!

O.H.

 

[borwish]

It's a brass handle right? Can you get a hardened bolt (like whatever the metric version of grade 8 is) and grind the leading threads and cut a couple of flutes to make your own tap? I've done this a few times in softer metals.

 

[StlEd]

It sounds like you might be looking for a bottoming tap.

eta...
Here's a link with information, and a short video

m4.5 x .75 HSS 4 Flute Bottoming Tap, Qualtech

m4.5 x .75 HSS 4 Flute Bottoming Tap, Qualtech. Find this item and other cutting tools on DrillsandCutters.com.

drillsandcutters.com

 

[Rosseforp]

There's a lot about taps I never had to know. This allows me to be open-minded. The tap needs to be M4.5 x 0.75 thread pitch, and I'd want the "length of cut" to be at least an inch/2.5 cm to allow for getting good threads all the way down. I've got a standard length tap in that pitch and it "shoulders out" before it can cut all the way through.

I believe you are looking for a Pulley Tap. McMaster Carr has them.


~doug~

 

[Tanuki]

Chuck,

The question isn't whether you can tap all the way thru the ferrule. Rather, you want to tap deep enough to add sufficient thread at the bottom of the ferrule so that the bolt coming up from the bottom can engage that thread and firmly lock to the cap post.

You can check the depth of effective threading that your standard tap gave you by inserting your lock bolt from the top. If you have a 5mm or more of threading below the cap post depth, that is plenty for locking. More is better, of course.

For my Merkur locking handle I used a standard length tap and got enough additional thread to do the lock up. BUT, I had to drill a little way up from the bottom so the lock bolt could get through to the threads. A slightly oversize drill bit is no big investment.

Care is required in limiting the depth of the drilled out bore, so you don't drill through and erase the threads you cut.

Sorry I didn't think this way about your project until now. Here's the 'mechanical drawing'.

 

[Tanuki]

I measured my Merkur extended threading. I have about 18-19mm of total thread depth, obtained with my standard M5 tap. The ferrule is about 22mm long, so I only had to drill out 3 or 4 mm to allow my lock bolt to reach the threads from the bottom.

I measure the FOCS ferrule at 23mm long. The FOCS cap bolt projects slightly less than 10mm thru the baseplate. That makes it a fairly long cap bolt. But there is plenty of ferrule length available for extra threading.

My FOCS cap bolt is also unusual among razor cap bolts in that it has a bullet tip. If the bullet tip has too small a contact point to lock effectively, I would be tempted to file it flatter.

 

[Old Hippie]

Thanks to all of you!

I'll admit I had focused on one way to accomplish my goal, at the expense of some good alternatives. Then complicated things by trying to sort it out on my own.

Seems like a graduated approach is in order. I like the idea @borwish put forward, and will keep it in mind but I happen to live in a place where M4.5x0.75 machine screws are usually a couple of weeks or more away. Not that I'm so impatient, but yeah, I struggle with impatience, too. Foreseeing that problem, I also have a die in that pitch so I can thread a piece of brass rod stock.

I'll have to go look at my tap again, but I may already have a bottoming tap. If that was an option, I would have chosen it on the theory that having full threads down closer to the end of the tap might be sufficient. Might not have been an option on offer while I was down at the local Fastenal warehouse.

I think the first step is to relieve the bottom of the ferrule a couple millimetres. I have already run the available tap down the hole as far as it will go, so I'll take another look at that and see if I can go a slightly different direction. That may be the simple elegant solution.

I'll also look up the pulley taps @Rosseforp suggested. Learning new stuff is good, and that may be the direction I go.

Cool. Suddenly this is looking possible again. My sincere thanks.

O.H.

 

[Tanuki]

After looking at my M5 tap, if I do another Merkur locking handle I'll be tempted to try and reduce the tap's shoulders in order to get the last few millimeters and tap all the way through. Last time, tapping the ferrule was the easiest step in the whole process.

Brass is soft, so I am not worried about the strength of a reduced tap shaft. How I would reduce the tap's shoulders is the question. Chuck it in the drill press or the wood lathe and try files, cheap diamond files, and maybe SiC sandpaper I suppose.

M4.5 x .75 is just annoying! Has Amazon even heard of it? I don't know anywhere in this city where I can buy M4.5 long bolts, coupling nuts, taps, or dies. We need to have a word with Fatip.

After dinner update: I chucked the tap in my drill press and worked a little on reducing the 5.0mm shaft diameter. I used a cheap triangular Harbor Freight diamond needle file and a narrow strip of 120 grit SiC wet/dry. No Doug, no Sherline, no cutting tools

I got about 0.2mm off the diameter without too much effort. I need a total of about 0.88mm off to avoid damaging the female M5 threads. The spec is 4.132mm. That means that a smooth shaft less than 4.132mm (0.1627") diameter will pass through the threaded M5 ferrule without scraping on the female threads.

That sounds like more futzing around than I will bother with for the moment. The word "grinder" is echoing around in the void inside my skull. Also the words "lathe" and "outside".

Bedtime update: The tap for through holes is called a plug tap. Amazon has a M4.5x.75 tap set: one each taper, plug, and bottom taps for less than $20. Here is the title:

Drill America - DWTS4.5X.75 m4.5 x .75 High Speed Steel 4 Flute Hand Tap Set, DWT Series​

The listing specs are inadequate, but if the picture is correct, the tap is about 3cm long. I counted threads and did math! That should be long enough to tap all the way through the Fatip ferrule. Starter threads supplied by Fatip, through hole already drilled by Fatip, piece of cake, with a decent tap wrench and some oil.

I probably should have put the time into writing a couple more chapters of my great American novel, but an absurdly nerdly deep dive into razo-mech-tech is top fun. I should have taken more shop.

 

[Rosseforp]

That sounds like more futzing around than I will bother with for the moment. The word "grinder" is echoing around in the void inside my skull. Also the words "lathe" and "outside".

Dremel is another word echoing around. I'm lucky having some really good local hardware stores that do carry M4.5 x .75 taps.
When the local hardware store doesn't have what I need, McMaster Carr carries almost everything needed for fabrication.
I bought our Heat Treating oven at work from McMaster Carr. They even carry stainless steel razor blades.

~doug~

 

[Old Hippie]

I got schooled up a few years ago by McMaster Carr. They didn't then and still may not ship to Canada. So I "hired" a friend of mine as "Production Manager" for my "company" and had what I wanted shipped to him. It worked but was a hassle. I then thought that Acklands-Grainger would work, but as it happens it's "Acklands" for Canada and "Grainger" for the U.S. and many of the products available in one are not available in the other. I can occasionally get stuff from KBC Tools but it's spotty. There's a company called Fastenal that seems to like doing business in Canada; never have what I want in the local but at least I can get it with a minimum of folderol and a bit of waiting.

One thing I miss from the Old Country is hardware stores with aisles full of those drawer cabinets with nuts, bolts and other sundries.

O.H.

 

[borwish]

One thing I miss from the Old Country is hardware stores with aisles full of those drawer cabinets with nuts, bolts and other sundries.

I'm lucky in that I have one less than a mile from me. Years ago I needed an odd metric die to fix my car. None of the auto parts places had it. As an after thought I stopped in there and they had two---for a third of the price that the parts places wanted to order it. They're also cheaper than the big box stores on small items like hardware, plumbing, and electrical fittings. Support small businesses!

 

[Rosseforp]

I'm lucky in that I have one less than a mile from me. Years ago I needed an odd metric die to fix my car. None of the auto parts places had it. As an after thought I stopped in there and they had two---for a third of the price that the parts places wanted to order it. They're also cheaper than the big box stores on small items like hardware, plumbing, and electrical fittings. Support small businesses!

Same thing here, we have an industrial hardware store a few miles away that carries everything the box stores wont. And an Ace Hardware store a mile away.
Then there is my machinists tool box if I feel like rummaging around.

~doug~