Yes, it can be legal to make a silencer. For everything Form-1, from silencer designs that are easily made, to filing forms with the BATF, to 3D modeling. Remember, you must have an approved BATF Form-1 to make a silencer. All NFA laws apply.
I've been browsing around the external right hand threading tools, and I'm more lost than before.
Seems the inserts are for a specific pitch only, why couldn't I use one for say 24tpi and 28tpi, I mean they are just 60 degree cuts right. What am I missing here?
I've been just using a chi-com universal 60 degree carbide bit, and it works ok, but it's shabby, and I had this thought while looking around.
Oh, if you have a link for something that works good, let me have it!
Dr.K wrote:I've been browsing around the external right hand threading tools, and I'm more lost than before.
Seems the inserts are for a specific pitch only, why couldn't I use one for say 24tpi and 28tpi, I mean they are just 60 degree cuts right. What am I missing here?
I've been just using a chi-com universal 60 degree carbide bit, and it works ok, but it's shabby, and I had this thought while looking around.
You are missing the depth and the root radius as well. On specific thread pitch inserts they are designed to match the specification for said thread pitch. There is more but those are the main ones.
Example.....A 28tpi won't cut 24 deep enough.
The following pictures are the same size inserts(tool size), just different tpi. Sorry didn't resize the pictures but you can see the difference easily.
Here is a picture of a 20tpi insert notice the tip, see how rounded it is? See how far the projection is?
Now look at a 28tpi, notice how much shorter the projection is and the different radius?
You can get both full profile or partial profile. Full profile means it cuts the entire thread profile including the top flats, it can therefore only cut a single pitch but has several advantages, first it doesn't produce the burr at the top that a partial will do, secondly you can accurately measure thread diameter by simply measuring the top diameter rather than pitch diameter.
A partial profile insert are simply sharp pointed 60° cutters that work as your basic HSS cutter, works for any pitch but without the rounded crest. The rounded crest are worth some consideration, it reduces stress concentration and also reduces depth of cut which can be vital in thin walled parts.
JohnK454 wrote:In the Carmex world, the generic insert to cut threads from 16-48 TPI would be something like 16 ER A60 - size 16, (E)xternal (R)ight, 60deg threads.
Dedicated inserts are better, for the reasons mentioned. However, the A60 will cut threads much nicer than most setups.
How do univeral threading inserts cut better than properly formed thread pitch specific inserts?
Can you justify that stament as we have seen the exact opposite with threading al, ss and ti.
JohnK454 wrote:In the Carmex world, the generic insert to cut threads from 16-48 TPI would be something like 16 ER A60 - size 16, (E)xternal (R)ight, 60deg threads.
Dedicated inserts are better, for the reasons mentioned. However, the A60 will cut threads much nicer than most setups.
How do univeral threading inserts cut better than properly formed thread pitch specific inserts?
Can you justify that stament as we have seen the exact opposite with threading al, ss and ti.
I gather he is saying the partial profile will cut better than my chi-com junk cutter. He did say dedicated inserts are better.
JohnK454 wrote:In the Carmex world, the generic insert to cut threads from 16-48 TPI would be something like 16 ER A60 - size 16, (E)xternal (R)ight, 60deg threads.
Dedicated inserts are better, for the reasons mentioned. However, the A60 will cut threads much nicer than most setups.
How do univeral threading inserts cut better than properly formed thread pitch specific inserts?
Can you justify that stament as we have seen the exact opposite with threading al, ss and ti.
I gather he is saying the partial profile will cut better than my chi-com junk cutter. He did say dedicated inserts are better.
Precisely. The generic 60deg A60 insert will beat the usual run of the mill threading cutter every time, but the inserts specifically made for a certain pitch are better yet.
JohnK454 wrote:In the Carmex world, the generic insert to cut threads from 16-48 TPI would be something like 16 ER A60 - size 16, (E)xternal (R)ight, 60deg threads.
Dedicated inserts are better, for the reasons mentioned. However, the A60 will cut threads much nicer than most setups.
hear hear.
I use iscar threading inserts . . . last forever. This one external threading insert has literally been in the toolholder 2 years. IC908 . . . works very well
Just to amend my post, there are actually three types of inserts: Full, partial and universal. Partial will have a nose radius that limits the range downwards and a height that limits it upwards, it will work for a range of pitches but only cut the correct radius for the smallest. Universals are virtually sharp and will cut any pitch within the height limitations but without the rounded crest.
Treated properly a single cutter can virtually cut miles of threads, and far more precise than HSS that needs to be sharpened regularly. And if you're as lucky as me they last forever since I have a machinist friend that can pick up another from work whenever they break
If you only do the occasional thread job a partial or universal will get the job done, but a few full profile cutters should cover 95% of the most common threads. I have 1, 1,25 and 1,5mm inserts, and if I need a custom thread I always pick 1mm if possible. You can also cheat a little by using metric cutters for imperial pitches that are close (or the other way around), my Vixen is threaded with 16TPI (1,59mm) 55° which was impossible to get so I used a 1.5mm 60° insert and those threads fit a helluva lot better than the other barrel that a qualified gunsmith fitted.
Fulmen wrote:Just to amend my post, there are actually three types of inserts: Full, partial and universal. Partial will have a nose radius that limits the range downwards and a height that limits it upwards, it will work for a range of pitches but only cut the correct radius for the smallest. Universals are virtually sharp and will cut any pitch within the height limitations but without the rounded crest.
Treated properly a single cutter can virtually cut miles of threads, and far more precise than HSS that needs to be sharpened regularly. And if you're as lucky as me they last forever since I have a machinist friend that can pick up another from work whenever they break
If you only do the occasional thread job a partial or universal will get the job done, but a few full profile cutters should cover 95% of the most common threads. I have 1, 1,25 and 1,5mm inserts, and if I need a custom thread I always pick 1mm if possible. You can also cheat a little by using metric cutters for imperial pitches that are close (or the other way around), my Vixen is threaded with 16TPI (1,59mm) 55° which was impossible to get so I used a 1.5mm 60° insert and those threads fit a helluva lot better than the other barrel that a qualified gunsmith fitted.
I love all this 'dirty' talking on this thread while being given new information.
New tools to buy!
And, Fulmen, I wish I had a friend who could give me the 'five-finger-discount' on
replacement tools.
Life IS good, I'm learning the tricks of the trade as well while helping him out. His favorite turning tool is a discarded holder with sharp inserts, whenever he breaks one he can just pick up another insert from work. If I need a tap or reamer I can just ask him to borrow one, if they don't have any it probably doesn't exist. They've even had a tool supplier borrow a tool since they didn't have one in stock at the moment.
The threading tool I'm using will only allow me to take 0.001" off each pass. If I try to go with 0.002" per pass it just breaks off the screw that holds my insert.
I was wondering what tool and insert would let me take off more material per pass? I'm looking for something I can use on my 12x36 lathe.
steve_dune wrote:The threading tool I'm using will only allow me to take 0.001" off each pass. If I try to go with 0.002" per pass it just breaks off the screw that holds my insert.
I was wondering what tool and insert would let me take off more material per pass? I'm looking for something I can use on my 12x36 lathe.
Thanks
What pitch are you cutting, and internal or external?
It's external threads. I'm looking for something for threading barrels and end caps for my 3 forms that should be back any day. I'm gearing up with my tooling. I don't want to take 0.001" per pass doing my barrels. Mostly I'll be doing 24 tpi and 28 tpi.
