Chiped tap on 316 ss

[vaeevictiss]

How the hell do you tap SS with a 6 flute hss tap?

I drilled the hole to 37/64 (this is for a 5/8-24 tap) according to a thread guide i found online. The hole was drilled using a flood system so i know it didnt get hot enough to work harden.

I used the tailstock to line the tap up straight and turned the chuck by hand to get it in a thread or two.

I then put a handle on the tap and tried to turn it by hand and the tips of all 6 flutes chipped off.

Few questions...

1. Can i still use the tap even once to just thread this damn thing.

2. Is 37/64 too small? The guide stated it should be a 75% thread. I saw i could use an 19/32 to get a 50%

3. Should i be doing it by hand or use the lathe?

First time in trying to thread ss and it is a real PITA.

[ranb]

2. Is 37/64 too small? The guide stated it should be a 75% thread. I saw i could use an 19/32 to get a 50%

3. Should i be doing it by hand or use the lathe?

When I make a hole I start with a drill bit then open it up to the right size with a tool bit. This makes it exactly the right size and ensures the hole is actually in the center. I am rarely able to drill a hole in material that is within .005" of center with just a drill bit; it always wanders a bit.

According to my calculations a 37/64 hole (.578") is 87% thread engagement. For 75% I think you need .584". For holes too small for my threading tool I start with the piece in the chuck and the tap in a tailpiece chuck. After I get a few turns in I replace the tailpiece chuck with a live center to hold the tap straight and turn it with a wrench.

Ranb

[Dr.K]

All my taps have 4 flutes. Maybe they are more substantial than the sixers.

[vaeevictiss]

For holes too small for my threading tool I start with the piece in the chuck and the tap in a tailpiece chuck. After I get a few turns in I replace the tailpiece chuck with a live center to hold the tap straight and turn it with a wrench.

Ranb

thanks this helped a ton! i was also able to still use the tap and the threads came out fine...

however....

The lathe we have at work is not the best, and some how when i turned the toolholder in either i goofed a bit or the carriage flexed a bit and i ended up making my hole .600. Oddly, after threading it is right at the .584 -.585 that you suggested, but threading on it has a tiny tiny tiny bit of wobble. Once it is tightened down all the way it is solid as a rock. Should I be concerned about this?

[ranb]

A small amount of wobble with 75% engagement is normal in my experience. But if you can do better, then try it again.

[al redneck]

I have used 4 flute taps extensively at work on 316 ss without problems . I center drill and then drill with a 37/64" drill for a 5/8-24 thread. Without a pilot hole it generally cuts .579- .580 . A good tight fit but since the barrel has to be threaded anyway it won't make any difference . My parts have threaded onto barrels that were threaded for muzzle brakes ( from 2 different gunsmiths ) with no problems . ALWAYS use taps with the fewest number of flutes possible to avoid breaking taps - trust me on this ! I hate sloppy fits . a 600 hole didn't ruin the part but isn't what I'd feel comfortable with .

david

[SRM]

just gotta know how to run a tap .
it will work over time.
most people i meet break them the first go around!

[saigatechusa]

There are taps ground just for Stainless steels with proper angles and relieves

Pick the right tap also, starting tap vs bottoming tap

I inspect the tap, align with tail stock, and what I have not heard that is very important use a good cutting oil. I use an oil with molly lube.

Many people also try the cheap imports even if they say HSS or cobalt they generally are junk.

After all this I remember what I should have done first...........ask for a little help from above

[Homer]

G'Day Fella's,

Vaeevictiss, what cutting oil/fluid are you using?
In my experience, you can get most threads cut OK (in any metal), as long as you use a good cutting Oil/Fluid and take it slow and steady!

Hope that helps

Doh!
Homer

[ranb]

What is recommended for steel? I have been using automatic transmission fluid and it seems to do the job.

Ranb

[Capt. Link.]

I will never recommend the use of any tap for a suppressor as a lathe should be used for accuracy.
Proper tap selection and this product has helped me:

[saigatechusa]

I will never recommend the use of any tap for a suppressor as a lathe should be used for accuracy.
Proper tap selection and this product has helped me:

You never use a tap but you use a tap

[kc0myg]

Cut barrels and suppressor threads with lathe, taps for everything else, like scope mount screws, trigger guards and the like.
Just my opinion, but works for me...
And use good lube for both, but not necessarily the same lube.

[Homer]

[quote="saigatechusa"][quote="Capt. Link."]I will never recommend the use of any tap for a suppressor as a lathe should be used for accuracy.
Proper tap selection and this product has helped me:

[img]http://cdn.mscdirect.com/global/images/ ... 059-21.jpg[/img][/quote]


You never use a tap but you use a tap [/quote]

G'Day Fella's,

Saigatechusa, that one got me scratching my head as well!....???

Double Doh!!
Homer

[kc0myg]

I can't answer for Capt. Link, but I believe that he's saying (like I say), lathes for barrels (both ends, muzzle for suppressor
or flash hider/comp, breach for re-barreling, etc.) and for said barrel attachments(suppressor, flash hider, recoil comp., golf
ball launcher, etc.) and taps and dies for most everything else.

[vaeevictiss]

Ya i just made another part. Didn't want to risk it with loose threads. Got a 4 flute tap and redid it and the threads are very tight.

This is just a break im making. Trying to practice machining Stainless before i do anything else.

[Fulmen]

Actually you can use a tap for a silencer without too much risk, but I wouldn't do it unless I had no other choice or remaking the part wasn't a big hassle. You do need to do it in a lathe, and if possible turn a small entrance at full diameter to guide the tap. You won't loose any threads since this part ends up over the relief cut on the barrel, and generally aids alignment when mounting the can.
I'm not saying it's perfect, but if you don't have any other choice, what are your alternatives?

One solution would be to tap the hole first, and then mount it on a threaded rod before turning the rest down to the final dimensions. It's not perfect as you don't have any guarantee that the shoulder is perpendicular to the threads, but at least you've made the rest of the part as straight and concentric as possible.

Another common problem is the lack of proper tools for single pointing. Hand grinding cutters isn't easy, so if you're afraid of mucking up the thread profile you can single point to 80-90% and finish with a tap. This will almost always produce threads that are just as straight as with SP.