Fantasy Swivel Breech update

[pushboater]

Just thought I'd take a moment and post a photo or two of my project.  It's going pretty slow right now.  I am making a little progress on the Swivel Blocks.  I still have to cut the second Chambers Early Ketland lockplate in two and dovetail it into the front swivel block.  Ran into several setbacks.  It seems that 6-40 taps have a disturbing tendency to break in two quite often!  After the first one broke off in the hole I drilled I didn't know what I was going to do to get the broken portion out.  I finally managed to make a small three pronged tool that fit down into the chip grooves inside the hole and was able to back the broken off section out.  Drilled a second hole and broke off a second 6-40 tap in it also.  I'm going extremely slow and using oil.  I got my taps from TOTW.  Is there any where else to get 6-40 taps? Any one have any suggestions so that maybe I can avoid breaking another one?  I have 4 more 6-40 holes to drill and tap and I really don't want to keep breaking the taps in two.  Getting that broken portion out is a real pain in the !@#%. Two holes and two broken taps so far!  I'm on a roll!



The lock really turned out to be quite compact compared to a lot of the Swivel actions I've seen.  It's only about an inch longer that the stock Early Ketland Lockplate that I'm using for the front frizzen sections of the lock.  I would have liked to have had the back of the pan fence a little closer to the Front Swivel Block, but several factors combined and I was forced to make a decision that placed it in its current position.  I'll try and fix that on the next one!  Naturally, any observations and/or comments are always appreciated.  Thanks for looking.



Capt. David

[coutios]

  If you have access to a machine tool supply house look for a two flute plug tap. (sprial Point.) Greenfield is a brand I like to use. Hold up well for me, of course use a good tapping fluid..

Best of luck
Dave

[E.vonAschwege]

Are you using high carbon steel or highspeed steel taps?  I recently learned that HS Steel taps are the way to go - they stay sharper and stronger, and aren't as brittle as HC steel.  The downside is that they won't anneal and will be tough to drill if you break one.   I've made several locks with 6-40 taps and have only broken them on occasion (when it was clearly my fault and I thought I could give it ONE more twist - nope!).  Your project looks great by the way - it's going to make for some beautiful lines.  Thank you for sharing. 
-Eric

PS - metallurgists and machinists please correct me if I'm wrong about HS vs HC steel tools.

[Randall Steffy]

I suggest you use HSS taps if your intent is to not break the tap and use high carbon if your intent is to remove broken taps. Be sure your tap drill gives 75% or less thread, ie; use a slightly larger drill(number drills required.) Also be sure to use a tapping lube and lastly, apply less pressure than will break a tap (the toughest aspect of tapping for the novice.)
All of that said, buy a more expensive tap as you usually get what you pay for. I have been known to whisper a prayer prior to some tapping jobs, faith being requisite in both the prayer and the tapping.

[Paul Griffith]

You can access Travers Tool  on line. Like Dave t k pointed out, use 2 flute spiral point.  Tap Magic is also good for an oil.

Paul

[Bob Roller]

Evon,
You're right about HS taps as opposed to HC. Using a slighly larger drill than recommended is a good way to get a substandard thread and I certainly don't want it for a breech plug,nipple or drum installation. I go the opposite direction and go one size UNDER drill charts.
I always countersink the holes the depth of one full thread for either blind holes or thru holes. My internal lock screws are either 4x40 or 4x48 and the link is normally a 1x72 and the hammer screws are 65x40 and I use tap magic on everything including slab cuts with a milling machine.

Bob Roller

[pushboater]

Thanks everyone.  The taps I'm using are HC as opposed to HSS.  I'll try and order a couple of the 2 flute spiral point taps and see if that doesn't help with the broken tap issues.

Capt. David

[Bob Roller]

A correction. My hammer screws are 6x40 NOT 65x40.
I must either do spell check or proof read closer.

Bob Roller

[pushboater]

One of the problems is that I'm tapping blind holes.  I am using the recommended #33 drill bit.  Would you still recommend a plug tap as opposed to a bottoming tap?  I really need the threads to go down as far as possible.   Do they make bottoming taps with two flutes and a spiral point?

Capt. David

[David Rase]

If you are not getting at least a full diameter of threads you should consider a bottom tap.  Most of th ebottom taps I have are 2 flute.  A good place to go to is Enco.  Their on-line catalog is fairly easy to navagate, has pictures, full discriptions and you can buy American or import tools.  I use them a lot.  MSC is also a good place to shop for tools.
David

[Bob Roller]

Do what I do. I drill the tumbler shanks of my locks with a #33,start the threads with a plug tap AFTER countersinking
the the hole the dpeth of one thread and then finish with a bottoming tap. I also use Tap Matic fluid.
Bob Roller

[44-henry]

I use a lot of 4-40 and 5-40 taps and my students use these quite regularly in building small steam engines that we use as a project in our introductory machining class. One trick that I have found (other than using a milling machine to help keep the trap straight) that helps is to have the student grind a ring around the tap, just above the threads. The idea is to make the tap weakest at this point so that if it breaks, it will be well above the hole. About 98% of the time this seems to do the trick.

It also helps to use a small wrench, or even better, a small knurled disk. If you can't put a lot of leverage on the tap you are less likely to break it.

 

[pushboater]

That's a great idea to ring the tap above the threads Alex.  I never thought of that.  After I broke the second tap I squared off the end of the broken tap on my grinding wheel, ground a short relief on the end and then used it to finish tapping the hole I'd started, but this time I simply wrapped my fingers around the center portion of the tap wrench so I couldn't get as much leverage.  I did manage to finish tapping the hole without further incident.  I've ordered a couple of 2 flute H2 HSS spiral taps.  I hope that solves the problem.  Thanks for the tip.

Capt. David

[Dphariss]

That's a great idea to ring the tap above the threads Alex.  I never thought of that.  After I broke the second tap I squared off the end of the broken tap on my grinding wheel, ground a short relief on the end and then used it to finish tapping the hole I'd started, but this time I simply wrapped my fingers around the center portion of the tap wrench so I couldn't get as much leverage.  I did manage to finish tapping the hole without further incident.  I've ordered a couple of 2 flute H2 HSS spiral taps.  I hope that solves the problem.  Thanks for the tip.

Capt. David

Carbide tools, drills and end mills will cut HS steel taps like butter.
BUT you must have everything fixed in place. Carbide is brittle and if the parts can move the drill will shatter. So a good drill press and a drill press vice is needed.

Dan

[pushboater]

Thanks Dan, I don't have any carbide drills but I did see some cobalt taps when I was looking.  I know cobalt is some pretty tough stuff.  Have you had any experience with cobalt taps?  Are they brittle like carbide?

Capt. David

[Dphariss]

Thanks Dan, I don't have any carbide drills but I did see some cobalt taps when I was looking.  I know cobalt is some pretty tough stuff.  Have you had any experience with cobalt taps?  Are they brittle like carbide?

Capt. David

Cobalt is a form of HSS. It has better wear characteristics from what I have read.  Dunno about brittle.
Carbide I get from MSC or other suppliers.

Dan