THREADER

Welcome to the "KNAELL-THREADER" Website.

As you can see we are hardware oriented.

As of this moment, August 17 2007, I have decided to quit
selling the Knaell Threader Kit. It was just too much work
for too little money. This website will stay up for awhile
and maybe someday this kit will appear back with me or
somebody else doing the hard work. Can't tell.
Keep carving metal - it's a great activity ! - Ken

| A Y Axis NC Mount |

The tilted base makes viewing generally much easier and particularly helps with reaching the motor pulley if you have a crank mounted there for slow speed threading. It also helps protect the gear rack used with the carriage handwheel from accumulating chips. The dumbbell shaped thing on the bed in the upper right pic is a pair of 1/2-20 left and right hand automobile wheel lugnuts run onto a piece of 1/2" rod that was threaded using the "Knaell Threader".

Welcome to the no frills "Knaell Threader" website. Hopefully these pictures will make clear what the Knaell threading attachment for the TAIG Micro Lathe is about. The Knaell Threader installed on the TAIG is shown above.

The design philosophy for the threader was that it maintain the properties of practicality and adaptability built into the TAIG Microlathe and add lasting value at the least possible cost. The governing consideration was to make the mechanism as valuable as possible within minimum reasonable cost considerations and not add any cute additions just because the layout of the mechanism might make these conveniently possible. For this reason the mechanism is just what is needed to cut accurate threads on the Taig lathe and nothing more nor nothing less. Consideration was given to make the mechanism as easy to live with as possible so that much can be repaired, replaced, modified, or added to by the user himself. The idea was to make a tool for the shop to solve the the situation that nearly always governs shop practice which is "do what needs to be done to move the job ahead and get on to the next step". It definately was not to make a "gadget" with the maximum number of moving parts for the owner to watch and be entertained for awhile.

The result of this approach is that the threader will appear to have a precise and tight feel to the operator with little backlash or noise and very good repeatability when resetting the threading tool into the thread groove when making controlled and repeated cuts into the deepening grooves no matter how fine they are.. As a result of the use of timing belts and a leadscrew that is given a slight preload between its end bearings, the only backlash in the system is that of the split nuts on the leadscrew which is itself quite small and easy to tell when its slack has been taken up - much like the "feel" of making a measurement with micrometers. Also as a result of the use of timing belts and a constant engagement of the leadscrew, the accuracy of resetting the cutting tool is maintained at a very high level because the drive train is much less effected by the errent metal chip that might find its way between the teeth of two gears or under the split nuts as they would be reclamped on a leadscrew that might have picked up a chip. The method of threading adapted here is that the split nuts are not reopened between successive cuts of a thread but that the carriage is repeatedly returned to the starting position of the next cut by reversing the entire drive train after backing out the threading tool. This is a simplification over the traditional method of using a "threading dial" but has many advantages. The accuracy with which the threading tool can be reset is one of the most important.

Indeed one of the significant advantages of the use of timing belts instead of metal gears is also that the errant metal chip which will eventually inevitably appear at the left end of the machine will much less effect the rotational accuracy of the timing belt train than it would if clamped between hard gear teeth. The fact that many teeth are engaged between the belt and the pulley and the imbedability of the chip in the elastomeric belt will reduce the effect of this chip to insignificance compared to its effect if caught between two hard gear teeth. These two accuracy enhancements: the wiping action of the split-nuts on the leadscrew which are not opened between threading passes and the immunity of the timing belt drive to chip entrapment are considerable advantages in maintaining repositioning accuracy of the lathe carriage between repeated cutting passes. These are important when cutting threads so fine that a magnifying glass is needed just to see them. The fact that the belts and pulleys are "dish washer safe" and do not need a heavy coating of grease means that these highly handled items can easily be kept very clean which is an additional advantage

There are standards for the "XL" series timing belts and pulleys used in the threader. However there are variations in dimensions due to materials (nylon, lexan, metal), size, and manufacturer. The pulley frame of the threader was designed to handle nearly all of the variations to be found in the "standard" "XL" timing pulleys. The 1/5 inch pitch by 3/8 inch wide belt/pulley size seems to fit the TAIG perfectly and the proper length double sided timing belt which is needed to cut left-hand threads was found available only in this series. These pulleys are very widely available and the design is flexible enough so that there are numerous ways to build variations for the users special needs.

Metric threading is available but needs the metric leadscrew and a few extra pulleys to be able to set up all the common Metric screw pitches. There are three pulley sets to be chosen from depending on what ones needs or interests will be. These are the (Original)BASIC-8, the INCH-8, and the METRIC-8. The choice to make may seem rather confusing but look at it this way. If you know you will only want to be cutting US or English threads then get the BASIC-8 set. Otherwise go with the INCH set. The original BASIC-8 set uses a 14 tooth pulley in the N1 drive position on the lathe spindle while the other two choices, the METRIC-8 and INCH-8, use an 11 tooth pulley on the spindle. The pulleys used in the BASIC-8 setups are therefore slightly larger than those used in the INCH-8 setups for equivalent feeds. The larger pulleys may be a little better for the heavier feeds of the coarser threads. The smaller 11 tooth driver allows some very fine threads to be cut if you may be interested in very, very small screw threads. The advantage of the INCH-8 set is that it uses the same 11 tooth spindle pulley as the METRIC-8 set. There are two leadscrews, an Inch based and a Metric. They are so similar that they cannot be told apart except by careful measurement or by the identifying "M" used to mark the Metric one. The pitch of the INCH leadscrew is 1/20 of an inch(.0500") or 20 (Threads Per Inch). The pitch of the METRIC leadscrew is .0501".

The simple choice is to get either the INCH-8 or the METRIC-8 set since either is most economically expandable to the other set. This PULLEYS TABLE shows the pulley sets.

Negatives - well there have to be a few. One has to learn how to tension the belts, position the pulleys, and tighten the setscrews that hold the pulleys to the shafts. Actually this is not so bad since the only shaft that must be handled runs in nylon/graphite bearings so these parts remain free of oil. There exists a possibility of the pulleys rocking on their shafts if the setscrews are not tight enough. This problem has not been observed yet but it is good to keep this in mind and ones judgement quickly determines what works well. For very heavy use, timing pulleys with aluminum hubs and others with multiple setscrews are available. Measurements showed that the fiberglass reinforced Lexan pulleys supplied are well locked in position with 5-10 pound-inches of torque on the setscrews. In this regard it is also recommended that some feeling for the forces involved in cutting threads be obtained by hand turning the spindle to cut a few test threads. This can be done by directly grasping the stepped pulley or with a spindle crank which can be made and for which a picture is shown on the "Cranks" page. A spindle crank is a handy addition to even full size lathe tooling for finely controlled work. A crank on the motor pulley as shown in the first picture group is handy when smaller stock is fed through the lathe spindle. It can be statically balanced to cause no vibration at high motor speed. Go to the "Cranks" page for more on this.

Finally it was found in the first prototype that there exists the distinct possibility that the rack-and-pinion which is normally used to move the carriage by means of the handwheel can jam when the carriage is moved by other means. In other words - normally the handwheel is used to move the carriage and this works very well. However when the carriage is driven by the leadscrew causing the handwheel to spin freely, there exists the possibility that the rack-and-pinion may jam. This is unacceptable. For this reason parts are supplied in order to make the required modification to the handwheel mechanism as easy as possible. This modification is the second and last step in the installation and allows the handwheel to be snapped free of the rack when the carriage is driven by the leadscrew in screw cutting mode. It works very well but one has to remember to use it. Making this modification can be done after a breather in the first step of the installation process however in order to maintain the convenience of having the handwheel available for fast carriage taverses, it is recommended to get the handwheel modification installed as soon as possible to complete the installation. In order to prevent disasterous carriage bindups however it is recommended to remove the handwheel/pinion completely from the lathe carriage before this last step is accomplished. This modification is an interesting lathe project in itself and uses the newly installed leadscrew to get an accurate position of the carriage in the first serious use of the newly installled equipment.

The handwheel modification described later is unquestionably more of a challange than drilling and tapping the single hole that is required for installation of the main part of the threader. A number of pictures of various stages in this modification are shown along with other subjects later.

These hints and cautions were spelled out in some detail here due to the somewhat innovative nature of the timing belt drive system. These are however the same types of things that are already of second nature in the use of other machines and will become second nature for this machine also. This thread cutting mechanism works well, and effectively and permanently increases the utility of the lathe for those who need specially cut, small, accurate, concentric screw threads. Cutting threads with shallower depth than the standard 60 degree profile allows thin walled tubing to be threaded for minature steam fitting purposes.

The BASIC-8 Threader kit comes with pulleys that allow all American Standard (Unified National) threads in the NC and NF series for screw sizes from a #0-80TPI to 1/4-20TPI to be cut. With this same set the 96TPI can be cut as well as many other "oddball" pitches. With additional timing pulleys cheaply available from numerous sources, many other pitches can be cut. Clearances on the pulley carrier frame accept pulleys up to sizes that allow threads of up to and including 264TPI to be cut.

With the addition of metric threading capability the choices are somewhat larger. Please look at the "Inch/Metric Kit Choices" page to see how I have tried to explain this. Basically the INCH-8 allows the same standard threads as the BASIC-8 plus a 90TPI to be cut and the METRIC-8 allows pitches from 0.2mm to 1.5mm to be cut. Realistically about 20TPI and 1.25mm are the coarsest threads that can be cut although the tables list some pitches coarser than these for any special uses one can find. Since the spindle pulley is somewhat smaller on the INCH-8 and METRIC-8 pulley sets, the change gears used with them are somewhat smaller than those that would be used with the original BASIC-8 to cut identical threads. This makes the BASIC-8 setups perhaps a little more robust than the INCH-8 but on the other hand, the INCH-8 can cut the 90 TPI which is the UNF of the "00" thread size. Both will cut the 96TPI which is the UNEF thread of the "00" size. Both will cut all the standard inch based pitches from there down to the 20TPI coarse end.

Pulley setups for Righthand and Lefthand threading. I think these were set up for 48TPI pitchs. The left hand threading attachment is swung up out of the way for the picts but can be removed for convenience when not needed. These pics were made with the original BASIC-8 kit which has a 14 tooth pulley on the spindle. The INCH-8 and METRIC-8 setups would have the smaller 11-tooth pulley on the spindle and the other pulleys would be proportionally smaller.

One important aspect of the timing belts and pulleys is that fiber-glass is used to ridgidize the significant dimensions of these non metallic components. This insures that the only loss in angular registration between the lathe spindle and the leadscrew will be caused perhaps by changing slack in the timing belts as load on the carriage changes. With reasonable tension on the belts however, this error has not been detected and apparently is also not a problem in the belted drives on tables of numerical controlled mills where both tension and direction of rotation change. One test was made in which left and right handed 1/2-20 threads were cut in free machining steel. Cuts were deep enough that a hand crank had to be fitted to the lathe spindle to supply the required torque and the lathe had to be held down with the other hand. The resulting stud is shown sitting on the bed in the first picture group with RH and LH automobile lug nuts threaded onto each end. If one beefs up the drive to the lathe spindle, it can probably cut threads like this all day. However in its basic form, the TAIG Microlathe with the Knaell Threader is not recommended for making automobile lugbolts and is more suited to cutting threads a little finer.

Another advantage of use of timing belt technology for the lead screw drive is that metal chips that may get caught between the belt and pulley cause less damage and have less effect on accuracy than chips caught between metallic gears. Furthermore, as opposed to gears, the belts and pulleys can be thoroughly washed with ordinary soap and water and then do not need oiled after they are cleaned.

Threading on the TAIG with the Knaell Threader utilizes the technique of cutting threads while maintaining engagement of the split nut to the leadscrew throughout the total thread cutting operation. Experienced operators know that this is an accepted technique for cutting unusual threads where a threading dial may not function properly. A user may fabricate for himself such a threading dial based on a gear with a multiple of 5 teeth if this is desired however. An inexperienced user of this lathe will find that skill gained in cutting threads here will carry directly to larger machines.

The split-nut mechanism is the other half of the Knaell thread cutting attachment. An important feature of this mechanism is that it disengages from the leadscrew with a flip of the clamping lever allowing the handwheel to be used in the original factory intended manner. When engaged with the leadscrew, the split nuts are clamped down tightly to the lathe carriage allowing for no slopiness in this area except for the slight backlash between the split nut and the leadscrew itself. This along with the freedom from backlash and quietness of the timing belt mechanism make for a very precise feel when the machine is set up for screw cutting.

The splitnuts in the "disengaged" and "engaged" positions.

Another option made possible by the flexible design is convenient easy addition of a small secondary motor to provide a fine feed through the leadscrew or to implement numerical control. This is shown in the picture with pulleys set up for a 48TPI lead.

Auxiliary motor for fine feed or numerical control. Convenient belt change switches over to threading.

The RH & LH 1/2-20 cut thread with lugnuts is shown on the first set of pictures and, Yes, the tailstock still works as usual on the bed. The "V"-belt has to slope up and away to allow room for positioning of the pulley carrier frame for all the angles it gets set to. The lathe is raised up one step on the 2x4 risers for the same reason. Fringe benefit is this allows area to lay tools down and makes cleanup easier. The base is a one foot square of 3/4" plywood and the 2x4's are 6" long except the bottem one which is 12" long. Some sanding and three coats of urethane floor varnish helps. Notes on how to make a motor mount will be somewhere in here if I remember. You really need a reversable motor to "back up" the carriage when threading with continuously engaged halfnuts. The wrench comes with the kit.

This is the original BASIC-6 kit which has been replaced by the BASIC-8 pulley set which has two more pulleys than are shown here. The original kit only had 6 pulleys. Also the left end bearing block now has "KNAELL" stamped into it. The COMBINED-12 kit has alot more pulleys than this and an additional leadscrew. I need to update this pic.

For now I am asking US$140.00 + Postage for any of the 8-Pulley kits and US$160.00 + Postage for the COMBINED-12 kit. The air mail postage runs around 10.00 in the U.S. and somewhat over $15.00 for overseas, so if I get a money order for $150.00 (to U.S.) or $155.00 (overseas), I will ship one of the "Eight-Pulley" kits immediately. The COMBINED-12 kit takes another $20.00.

You can contact me at:
knaell@erols.com

or:
Phone: (301)-754-1597

or:
KENNETH    KNAELL
10,000    REDDICK    DRIVE
SILVER SPRING,   MD    20901
U.S.A.