Enco, Gamet, Interstate Automatic / Universal Boring Head (222-1200)


Included in Set:

  • 5- Hex Wrenches (3/16”, 5mm, 4mm, 3mm, 2.5mm)
  • Pin wrench for carriage set screws
  • 3- Boring Extensions (2 ⅝”, 3 ½”, 4 ½”)
  • 1- Reaction Bar



  • 3 Automatic Feed Rates (.0005, .001, .1005)
  • Maximum Dovetail Travel 1.2”
  • Diameter of Body 3.54”
  • Tool Height (without Arbor) 3.74”
  • Weight- 12.09 Lbs.


I did a lot of research on this product and it appears that the Enco, Interstate and Gamet are the same tool; they come in two sizes 2.36” and 3.54” diameter. Some internet posters claim that this tool is made in France, my tool is clearly marked made in Taiwan. 


When I received the head, I could only advance the Tool Carriage CCW outward by hand; the result was a fully-extended tool that would not retract. I tried every adjustment and could not get the carriage to screw inward. My only option was to take it apart and figure out how it works!


Taking it apart:

Use a 5mm Hex Wrench, remove the Arbor Set Screw and the Brass Follower. 



With the Boring Head (BH) chucked in the Milling Machine and locked to prevent the Arbor from rotating, grip the BH with a Strap Wrench and loosen only the body, ‘do not  remove it’. The threads are right hand and should loosen CCW without extreme effort.


Remove the BH and Arbor from the Mill. Set it knurled cap-side up on the bench and unscrew the Arbor from the BH. The Arbor holds the Knurled Cap in place, so take care not to let it drop.


Holding the two parts of the BH together (Knurled Cap and Body), turn the tool over, tool carriage up.


Back off the three Gib tension screws (see 003) to allow the tool carriage to slide freely; the two outside Gib screws require the 3mm Hex Wrench and a special Pin Spanner included for this purpose. The center Hex Wrench is 5 mm. It is expected that the Gib’s outer Hex Screws tension are pre-set while the center Hex is to lock the carriage for standard boring operations. When the tool is used for automatic boring the center hex should be loose.   


A 3mm Hex Wrench will remove the Adjustable Carriage Stop Dogs.


With a 5mm Hex Wrench, remove the Hex Head Dovetail Travel Limit Screw and Washer.



Remove the Tool Carriage from the Body.


The micrometer Zero Set Dial is divided into .0001” increments and should move freely with mild resistance, (without moving the micrometer screw). My Dial was stuck so the Screw Assembly had to be removed by tapping out the Dowel Pin in the Ratchet Gear.



With the Dowel Pin removed, gently tap out the Screw with a soft hammer. Take care not to damage the precision threads.


I spent a lot of time working these parts to make them turn freely, but not loose. 


The last step was to lap in the parts with a Grinding Compound. I added a .012” Brass Shim behind the Ratchet Gear, to take out the play between the Gear and the Body; the screw now turns smoothly with no lost motion.


Holding the body parts together, turn the head over so that the Knurled Ring Cap is up. Removing the Knurled Cap will reveal 3 Ramp Levers, (2 on the smaller version 222-1100). These levers are spring loaded.


The ramps are easily removed by tapping out the Dowel Pins that serve as axles. Mine were so loose that I knurled the end to prevent them from falling out. 


Clean out the old grease and you will see that two of the Ramps will move up and down by turning the Hex Screws on the side. (#13 Lifter Ramp)

The third Ramp is fixed and will activate the Ratchet Gear once every complete rotation. Raising one of the other Ramps will move the Ratchet two clicks, and raising the third will advance three clicks every revolution “I added a yellow detent mark (#15) on the Hex Screw heads to indicate the up position of the Ramps”.


This illustration (#16) shows how the Lifter Ramps work.


The body has the center hole for the Arbor, a 16mm round hole for the Spool and a square hole for the Ratchet Cam. 

The Spool rotates to apply a brake  to the Cam when the Tool Carriage engages the adjustable Stop Dogs (see #6); this stops the Carriage from advancing outward to a predetermined point. Make sure the internal Push Rod has a proper purchase on the Spool “I had to machine out a small amount in the corner of mine”. 


Here is how it works: 


If you follow the motion starting with the top of the Spool, you will see that as the Carriage moves in the direction of the arrow, the Spool will be rotated and pushes the Rod and Nylon Brake into the Cam. This action will prevent the spring-loaded Cam from retracting and stop the advancement of the Carriage. The Carriage Stop Dogs can be set to any point within the range of the tool.


When I reassembled the tool, I was surprised how accurate the out-feed of the Tool Carriage was. Using only the one fixed Ramp, one revolution will move the tool .0005”. Adding another Ramp advanced the tool .001” and two Ramps .0015”. Any advancement of the Carriage removes that amount on each side of the hole. If the tool advances .0005”, the hole will be .001” larger.


I still had the problem of retracting the tool inward. I discovered that by rotating the Knurled Cap and finding a “sweet spot”, I could screw the Carriage inward back to its starting position.


I was not satisfied with this so after considering several fixes, I decided to grind as much as possible off the Ramps without disturbing the Landings. The Landings determines how far the Cam is pushed. Any alteration of the Landing Surfaces will change the travel of the Cam and may cause misalignment and damage to the Ratchet Gear.


I used the Surface Grinder to grind the Ramps but there is no reason that they could not be ground by hand, perhaps even grind a slight curve in the Ramps to extend the “sweet spot”. This made the "sweet spot" much easier to locate.



If you only want one Boring Head for your shop, this could be a good choice. The Micrometer Dial is graduated in .0001” allowing a very close tolerance cut; its downside is they are large, however, it is this mass that enables it to be a very stable cutting tool. The Receiver holes are ¾”, but you can make Bushings for any size Boring Bar that you have (see #20).




Warning- never run this Boring Head under power in reverse, using the automatic Carriage feed. It is only designed to rotate clockwise to feed the cutter outward!!!



  • Facing / Hole Facing
  • Internal Recessing /Grooving
  • Back Facing
  • Machining of External Surfaces
  • Radius Cutting
  • Boring of Tapered Hole



Facing can be used to clean up or create a flat top surface of a hole. Often a hole is drilled for a thread but a flat landing surface is needed around the hole for a bolt or screw to land.


Reaction bar:

The Reaction Bar is used to prevent the Knurled Cap from rotating in an operation like facing. In this operation we want to achieve a steady, constant outfeed of the cutter.


The Reaction Bar can be held by hand or braced against a fixed point. In this fixed position, the Bar can easily be snached out at any time. The bar is made of aluminium so if you have one of those “train wreck” crashes the bar will bend and hopefully save the part. “The end of my bar was .195” and the receiving hole is .240”. This is far too much play so I cut off the end of the Reaction Bar and turned a new end to .238”.


Internal boring:

Boring Heads are not normally used for starting holes from scratch. Most jobs use an existing hole that can be dialed-in or drilled and then bored. When a hole is centered, set up the Boring Head so the cutter just touches the side of the hole. If possible make a light cut, and measure the hole to assure everything is cutting how you want it. In the case where a hole needs to be only slightly enlarged, or cleaned up, place the cutter inside the hole undersized, start the machine and hold the Knurl Cap until the tool just touches the inside bore. (I found that I could run the cutter to the bottom with the Mill Downfeed, grab the Knurl Cap and run the tool out a couple thousands then Power Feed the Mill up. Never stopping the machine, I could go up and down and each time run the cutter out more). 


Internal recessing:

Internal recessing or putting a groove inside a hole is where the Automatic Boring Head really pays for itself. Sharpen the cutter to the shape needed, lineup where the groove goes and machine to the desired depth by holding the Knurled Cap. Stop the machine and back off the carriage. (Remember, do not try and auto feed it in reverse)!!!


External machining:

Machining of external surfaces requires the normal boring bar to be turned inward with the Mill running in reverse.

Any time the head is running in reverse, never engage the automatic carriage feed, It is only made to run in the normal direction to move the Carriage outward.

*Running the Mill in reverse can cause also the Arbor to unscrew.


Cutting a precision arc:

For a setup where you must know the arc the Boring Head will cut, this tip is from my HSM “Best Bud” Bernie Wasinger:

Chuck up a piece of aluminium or soft material in the Mill Vice. The side of the material should be square and stick out of the Vice, it does not matter how far. 

Zero in the Mill to an edge of the material.


With the Mill set on the zero edge, advance the table away from center, over half the amount of the desired diameter. Example: we want to cut a 6” diameter curve, move the table over 3”.

Install the boring head and adjust the cutter to just touch the zero edge. You can now chuck up your part and machine the 6” diameter. 



Boring Extensions:

Three Extensions are included with the Head (2 ⅝”, 3 ½”, 4 ½”). They have 5mm-0.8 set screws, 5mm long.. These should be replaced with quality set screws that are longer, “at least” 8mm long. Always use the shortest boring bar possible, however, there are those jobs that require a long reach and you have no choice and need these extensions. I do not think that any explanation is needed for the use of these extensions; I am showing  the extensions, one with a cutter made from a ⅜” broken center drill.


Not shown in the article:

Using the automatic feed, nine different tapers can be machined in a Bridgeport style machine. There are three down feed speeds on the mill and three outfeed increments on the Boring Head.


For questions or comments please contact me, James Long This email address is being protected from spambots. You need JavaScript enabled to view it..">This email address is being protected from spambots. You need JavaScript enabled to view it..

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