I had seen the suggestion about Moly D - I think I have some Moly D
grease for the car. Not sure if that is the same thing or not.
The larger hole is a good idea - I don't need any strength to speak of
for this so I could go with 50% thread (0.096 vs. 0.089 drilled hole).
I found a bar of 316 in my scrap bin so I'll test it out. The HSS taps
I was planning on using are brand new so maybe I can get away with it.
-Bob
On 08/04/2015 07:14 PM, Michael Clive wrote:
Titianium taps, Moly D lube. (Molybdenum disulfide)
On Tue, Aug 4, 2015 at 5:06 PM, Troy Prideaux <GEORDI@xxxxxxxxxxxxxxxx <mailto:GEORDI@xxxxxxxxxxxxxxxx>> wrote:
316 isn't necessarily harder than 304 - I've often seen 304 grades
that are harder than 316 grades and vise versa so if you can tap
into 304, the chances are you can tap into 316.
If the valve body is a casting, the chances are it's actually
not 316 but a close variant with similar properties that can be
identified as 316, but could be a harder material than your true
316 stock material.
Tapping stainless in general: I generally drill the initial bore
out wider than normal to avoid tool breakage. When hand tapping,
I'll rotate the tap a revolution or so and then reverse half a rev
or so to remove some of the frictional stress on the tap and
follow that process all the way to completion. Use a good grade of
tapping grease if possible or at least cutting grease. Make sure
your tap is aligned straight with the hole - preferably start the
tapping process in the same drill press position as the drilling
process if you used a drill press or fixed machine to drill the hole.
If machine tapping - tool life can be increased significantly by
following the suggested speeds and feeds that are practically
difficult to achieve by hand tapping.
Tapping small fine threads in hard stainless materials is hard
especially by hand.
Troy
>-----Original Message-----
>From: arocket-bounce@xxxxxxxxxxxxx
<mailto:arocket-bounce@xxxxxxxxxxxxx>
[mailto:arocket-bounce@xxxxxxxxxxxxx
<mailto:arocket-bounce@xxxxxxxxxxxxx>] On
>Behalf Of Robert Watzlavick
>Sent: Wednesday, 5 August 2015 9:48 AM
>To: arocket@xxxxxxxxxxxxx <mailto:arocket@xxxxxxxxxxxxx>
>Subject: [AR] Tapping holes in SS 316
>
>I need to tap some #4-40 holes in an SS 316 valve body (Swagelok
>SS-4P4T) for a bracket. I'd really like to avoid breaking the tap so
>any tips? I usually use SS 304 and aluminum so I haven't worked much
>with the harder stainless steels. The tap is HSS and I was just
going
>to use Tap Magic for the cutting fluid. If I have to, I can
drill all
>the way through the body and put a nut on the other side but I'd
rather
>use a threaded hole.
>
>-Bob