threading in reverse

While going through tool catalog the other night,i noticed that the aloris quick change adapter for threading says that you can use it to thread in reverse to cut a right hand thread. if i read that right is this system worth the purchase and how do i go about setting cutting tip up to thread with. i get good results the faster i can thread so i thought if i went from left to right i could step the rpms up to really get some good threads.

With the tool upside down and the spindle in reverse you can thread from the headstock towards the tailstock and produce a right handed thread. The tool is still set on center line using your favorite method; mine is a 6 inch piece of aluminum pinched between the work and the cutter, once it is vertical the tool is close enough.

Most toolposts will have enough height adjustment to let you mount a tool upside down; if they don't, just mill or turn up a packer to go under the toolpost.

Certainly does have the advantage you mentioned, also can give better results if your lathe is not particularly stiff, as the deflection vector is in a direction which relieves the depth of cut, rather than increasing it as in the normal tool position.

I find this to be a very good method for threading blind holes and such. I have even ground small round HSS bars into small threading tools to get into some very tight spots.

tim

I thread more in reverse with the tool upside down than in forward.

I have a nice carbide boring bar/insert holder with threading inserts for threading IDs, and I like to use that on the other side of the part with the spindle in reverse for threading ODs away from the head stock.

I occasionally thread 'upside down and in reverse' to cut left-hand threads from the tailstock to the headstock so I can avoid a relief for thread runout. I would rather use a relief and cut left-hand threads from the chuck toward the tailstock. I believe cutting without a radiused relief just allows a crack with a starting point to propagate from. Sometimes the print I am working from just doesn't allow it, for whatever reason. Quicky

Years ago - long time, we used to thread in reverse with the tool upside down. Reason: The lathe used to have bronze bearings and by threading with the tool upside down you pushed the spindle down thereby eliminating any play in the bearings and getting a better finish on the thread.

I thread right hand internal threads using a technique called the reverse helix method. With this method the spindle in run in reverse and the feed is from the headstock to tailstock. The tool is held in right side up in a lefthand toolholder. This allows me to thread right hand internal threads at very high speed on my manual lathe from a blind shoulder. See page 5 Thread Turning Methods http://www.kscjmy.com/product/VARGUS/pdf/VARDEX_TT_Tech_117-134.pdf BTW I get excellent finish and perfect thead form using Vardex full profile inserts and the correct anvil for a specific helix angle.

Honestly I'm surprised this isn't done more often, especially on manual machines without a kick out. Machining to a shoulder can be intimidating and exhausting for even the saltiest shop dog, all their bravado aside. Nothing like the sharp crack of a disintegrating insert to unleash a deluge of foul language at their misfortune. I don't care how good you are and how long you've been doing it, it takes a toll on a man to reverse the hand dial and disengage the feed lever at the same time repeatedly, day in, day out.

The first time I did the reverse-rotation, upside-down, threading-out trick in an oilfield shop, the foreman about shit himself. Then he watched and after 2 passes told me "Not a bad idea for an FNG". Of course this practice became more common as turnover increased and the new hires were slow to catch on to the "old-school" methods...or simply didn't understand to check the kick out and adjust as necessary PRIOR to taking that first pass...less stress on the foreman to have all the moving parts going away from eachother when overseeing a shop full of monkeys!

Winfield said:

I thread right hand internal threads using a technique called the reverse helix method. With this method the spindle in run in reverse and the feed is from the headstock to tailstock. The tool is held in right side up in a lefthand toolholder. This allows me to thread right hand internal threads at very high speed on my manual lathe from a blind shoulder. See page 5 Thread Turning Methods http://www.kscjmy.com/product/VARGUS/pdf/VARDEX_TT_Tech_117-134.pdf BTW I get excellent finish and perfect thead form using Vardex full profile inserts and the correct anvil for a specific helix angle.

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+1 million to this.

Exactly the way I do things. I'll do you one better though: I've added the "drop head" threading toolholder, and the full compliment of anvils for internal/external.LH/RH threading (at least in the 3/8" I.C. size.)

The drop head holders allow running in reverse without resorting to using boring bars. This means I can still use the tailstock.

I've still got a LONG way to go before I'll have all the different inserts I want to have on hand though.

PixMan said:

+1 million to this.

Exactly the way I do things. I'll do you one better though: I've added the "drop head" threading toolholders, and the full compliment of anvils for internal/external.LH/RH threading (at least in the 3/8" I.C. size.)

The drop head holders allow running in reverse without resorting to using boring bars. This means I can still use the tailstock.

I've still got a LONG way to go before I'll have all the different inserts I want to have on hand though.

Click to expand...

Pixman:
Could you please show a picture of a "drop head" threading tool holder.

BTW I also have invested in a full complement of anvils and all the internal/external full profile inserts for all the different thread types metric/imperial internal/external that I require. (at least in the 3/8" I.C. size.)

This is the one I snagged off of Ebay. I got it cheap probably because no one knew what it was.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=380252633714

There are left hand and right hand versions. I have only the left hand because when you flip it upside down in the Dorian CA QCTP holder block, it's the right one for threading from a shoulder to a point toward the tailstock. If I see a right handed one pop up for that kind of price, I might grab it just in case I ever need it. Hard to imagine where/when I might need to opposite to that one though.

I use a Vardex AVRC075 L.H. toolholder in a KDK156 bar with my KDK100 QCTP to hold 3/8” I.L. full profile inserts for internal threading right hand threads using the reverse helix method:
http://i72.photobucket.com/albums/i163/miltons_stuff/VardexTTKDK156bar.jpg

This setup allows max rigidity by making the unsupported overhang length of the toolholder as short as necessary in the KDK156 bar.

Also note that the insert is NOT used upside down for the reverse helix method. Here is a picture of the above setup for cutting an internal right hand thread using the reverse helix method: http://i72.photobucket.com/albums/i163/miltons_stuff/ReverseHelix.jpg The spindle is going in reverse and feed is towards the tailstock so very high speed threading can be done from a blind shoulder. In fact one can see the carriage stop on the headstock side lower left for quick repositioning up to the blind shoulder.
I like to use the compound set at 29.5*and advance the tool using the compound slide so cutting is on one side of the threading insert then return the cross-slide to zero for each threading run. This way cutting is only done on one side of the insert and one has a way of knowing from the compound dial how far has been advanced into the thread. For the final cleanup threading run I use the cross-slide to advance the tool so the final cleanup cut is cutting on both sides of the insert.

That's a good, rigid setup. At some point I'll probably add a couple of LH bars to the array of RH ones I have for just that same purpose.



There have been a few more additions to the "threading drawer" since this photo, particularly to that box of anvils. I buy just 2 or 3 Vardex full-form inserts at a time from KBC Tools. I do go to MSC if there's no Vardex I need in stock. On a rare occasion I might find something on Ebay. I don't think I could ever afford (or justify) buying a full box of ten threading inserts.

I also have the A60 and AG60 partial profile inserts for the oddball threads that I feel I'll only see once and form isn't critical.

We can run the reverse threading easily because I see your machine also uses the cam-lock style chuck mount. This luxury isn't available to many home-shop'rs who have lathes with screw-on chuck mounts.

Pixman:

If KBC or RL Stephens doesn't have the needed particular Vardex insert then I have KBC or RL Stephens order from the Vardex distributer then drop ship directly to me.

BTW the same L.H. Vardex AVRC075 bar used for cutting internal R.H threads also can be used for threading R.H. external threads using an E.R. insert with the spindle spinning CCW and the feed towards the headstock. Here is a picture of the same L.H. Vardex AVRC075 bar (used for threading R.H. internal threads with a I.L. insert using the reverse helix meathod) with an E.R. insert set up to turn a right hand thread with spindle turnning CCW and feed towards the headstock: http://i72.photobucket.com/albums/i163/miltons_stuff/LHBar.jpg

PixMan said:

We can run the reverse threading easily because I see your machine also uses the cam-lock style chuck mount. This luxury isn't available to many home-shop'rs who have lathes with screw-on chuck mounts.

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I bought my12x36 lathe specifically with a D1-4 camlock spindle. There are more reasons than just being able to reverse the spindle for a cam lock spindle though. I will never buy a lathe again with a screw-on spindle nor buy a lathe without 5C collet capability.

Winfield said:

BTW the same L.H. Vardex AVRC075 bar used for cutting internal R.H threads also can be used for threading R.H. external threads using an E.R. insert with the spindle spinning CCW and the feed towards the headstock. Here is a picture of the same L.H. Vardex AVRC075 bar (used for threading R.H. internal threads with a I.L. insert using the reverse helix method) with an E.R. insert set up to turn a right hand thread with spindle turnning CCW and feed towards the headstock: http://i72.photobucket.com/albums/i163/miltons_stuff/LHBar.jpg

Click to expand...

That arrangement seems versatile, but I've already got 3 different RH threading bars for internal threads, plus the LH drop head, and standard 1" shank SEL 1000 M16 (LH) and SER 1000 M16 (RH) holders. I don't have enough CA-1 or CA-2 QC blocks to dedicate to the insert holders all the time, but that's no big deal because all the square shank holders are the same 1" height. Take one out, throw the other in, same center height.

Internal threading bars fit into sleeves for the CA-4 or CA-41 boring bar holders. They end-up right on center too. The main reason I've taken to tooling up an old 16x40 manual lathe this way is that I one day expect to progress to having a CNC lathe big enough to take the 1" shanks. Plus, the machine came to us for the cost of shipping and was equipped with the CA-size QCTP. The 1" shanks just fit right, and make sense for future use too.

Pixman: The point was that the L.H. Vardex AVRC075 insert tool was not solely used for R.H. internal threading by the reverse helix method by can also be used for other threading methods by just changing the anvil and insert.

My KDK 100 Tool post accepts both the 105 and 155 bars. The dovetail dimensions are the same on the 0, 100, 150 and 200 KDK Tool Posts which allows bars from these series to be interchangeable. The 105 bar holds 1" diameter boring bar http://i72.photobucket.com/albums/i163/miltons_stuff/BoringBar.jpg The 155 bar accepts 1.25" diameter boring bars. http://i72.photobucket.com/albums/i163/miltons_stuff/125inBBKDK155.jpg

Also I have several KDK 119 5C collet bars which hold tools that fit up to 1.125” with appropriate 5C collet. For example here is a picture of the 119 bar with a ¾” 5C collet holding an annular cutter: http://i72.photobucket.com/albums/i163/miltons_stuff/AnnularCutter2.jpg

Also I make use of boring and threading bars with flats machined in that are held in KDK bars such as the ¾” boring bar in a KDK 154 bar as shown here: 3/4"BB mounted in KDK154 Bar picture by miltons_stuff - Photobucket
A 5/8” boring bar is held in a KDK101 bar as shown here: http://i72.photobucket.com/albums/i163/miltons_stuff/0625boringbarKDK101.jpg
The advantage of holding the boring or threading bars with machined flats on these KDK bars is that the unsupported length of the boring or threading bar can be changed without changing the angle or height of the cutting or threading insert.

All of these tools fit on my 12x36 lathe in my KDK 100 QCTP. KDK Tools - Standard Sets - Master Bar for Boring Bars

Hmmm...
I just don't get half of the small, plan view diagrams on p122 of the excellent Vardex catalogue, with particular reference to what they convey about the sign of the helix angle.

Here's my problem: if I look at the topmost case (RH thread, RH tooling) and imagine I swap the workpiece and tooling into an identical lathe, except with the headstock on my right and tailstock on my left, obviously the tooling and directions won't need to change. With the exact workpiece shown I'll have to start the thread further up the workpiece to miss the chuck, but that's surely immaterial to the tooling's handing and helix angle?

If I now walk around to the back side of the lathe, it seems to me I'm seeing the seventh case down. The rotation is as shown, as is the direction of tool travel. And the thread is still RH, as per the diagram.

So why do they tell me I now need a LH tool, with the opposite helix angle? (remembering that case seven is still a RH thread)

I have the same problem understanding three other cases. I would have thought the helix angle was purely a function of whether the thread was RH or LH.

Can anyone pinpoint what's wrong with my argument? Clearly they must be correct, I just can't see my error.

(Please don't anybody feel they should go to any great trouble devising a different explanation if mine doesn't do it for you - by all means do so if you want to, but it's unlikely to help me with my problem, which is that I seem to have an apparently sound argument which gives the wrong answer.

This is something which should strike deep feeligns of unease in a thinking, technical mind. It's not a sound basis for confidence in one's reasoning. What I'm hoping for help with is discovering the mis-step in my joining of the dots.)