My Lathe - 9x20

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Central Machinery Model 45861 9x20 Lathe

[Sept. 7, 2015]

[Sept. 30, 2015]

[Feb.4, 2021]

[Feb 10, 2021}

I'll be adding information and additional references to this page as I gain more experience with my "new" lathe.

[Sept. 20, 2015] I added an LED shoplight ($35 from CostCo) on a support immediately above the lathe - now I can see what I am doing! (In the above pictures, the light is off too eliminate camera glare.) With the vertical supports in place to support the LED light, I took the opportunity to also use them to add a pegboard behind the lathe for holding frequently used tools and accessories.

Purchased used in 2015 for $500, and included the following:

  • 4” 3-Jaw Chuck

  • Reverse Jaws For Chuck.

  • Chuck Wrench

  • Dead Center Mt#2

  • Dead Center Mt#3

  • Live Center

  • Threading Gear Set 28,30, 36,42,45 & 80T

  • Splash Guard and chip tray

  • Extra gears (metal except as noted):

    • 80 tooth

    • 80 tooth plastic gear

    • 60 tooth

    • 60 tooth (with a broken tooth)

    • 45 tooth

    • 42 tooth

    • 41 tooth

    • 40 tooth

    • 36 tooth

    • 28 tooth

[Update Feb. 4, 2021]

Since I originally wrote the above, I have acquired a 3D printer and was able to design and print the all of the above change gears, plus some additional gears. You can find more details and the required print files here:

https://www.prusaprinters.org/prints/30228-lathe-change-gears-9x20

The manual was missing, but I easily found one online (see references below). I built a wood stand to hold the lathe, with a shelf underneath; in the the future I made add a drawer to hold frequently used tools and parts and a "backboard" to hold wrenches, tool holders, etc.

For the near term, my priorities are to purchase an overhead light, a 4-jaw chuck, and a quick change toolpost.

Chucks and Backing Plates

[Sept. 28, 2015] I purchased a backing plate ($55) and 6" 4-jaw (independent) chuck ($80) from Shars; with the $19 shipping cost the total was about $155.

The backing plate is already threaded M39*4 and pre-drilled for mounting holes; it will still require a bit of machining to fit the chuck.

At the left is the plate as shipped - the package included a set of chuck mounting bolts and a catalog. There was a light layer of anti-rust oil on the plate - it cleaned up with a simple wipe with a shop rag.

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The 4-jaw chuck came packed in its own wooden box (see picture, left; rule included for scale).

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To the left are the contents of the wooden box: The chuck, chuck wrench, mounting bolts, and a "technical document" (includes specifications and other technical data on the chuck, and an inspection page); again, a rule is included in the picture for scale.

The chuck was also lightly coated with anti-rust oil, and wiped clean easily. The chuck wrench is a bit rough, but serviceable (I'll probably make a better one eventually).

Once I get the new chuck mounted, I will expand this section with the details.

Replacement Belts

Breaking belts seem to be a problem for some users of this model lathe. Possible causes of this may be:

  • Starting the motor with the belt under tension. Best practice is to start the motor with the tension released, and then slowly add tension once the motor is going.

  • Pulley mis-alingment: Even a small amount of mis-alignment can cause the belt to twist, resulting in accelerated wear.

  • Excessive belt tension: Adding an S-hook to the belt tension spring can reduce the tension somewhat (see References below for more on this).

In my case, worn bushings on the idler pulley may have contributed to this problem for me (see Replacing Bushings below).

See References below for more on belts.

Replacing Bushings - Idler Pulley

The bushings in my idler pulley wore out (one practically disintegrated), so I ordered replacement bushings from Grizzly (P4000207 - BUSHING $2.50 each, two required) and a new retaining ring (PR03M - EXT RETAINING RING 12MM $1.00 each) as the old ring was destroyed by the disintegrating bushing. These were cheap enough that I ordered two sets so I would have a spare for future use.

The picture to the left shows the replacement bushings and retaining ring. At the bottom left is an "insertion tool" I used to install the new bushings. The bushings are an interference fit in the idler pulley, and are also somewhat fragile, so I turned this little tool on the lathe to use to press them into place on my arbor press.

To remove the old bushings, I dis-assembled the idler pulley (CAUTION! It's a spring and ball type clutch, so make sure you don't lose any parts when you open it up). The old bushings were then pressed out on the arbor press, the new bushings were pressed in, and the pulley was re-assembled.

[Feb. 10, 2021]

I found it again necessary to replace the bushings. The outer bushing was so worn that the flange had separated; surprisingly the inner bushing was still in good condition. I ordered 8 replacement bushings, and when I received them I measured the ID and OD of all of them as follows (all measurements in inches):

  1. 0.47150, 0.55185

  2. 0.47170, 0.55195

  3. 0.47220, 0.55190

  4. 0.47165, 0.55190

  5. 0.47170, 0.55240

  6. 0.46760, 0.55190

  7. 0.46890, 0.55190

  8. 0.47150, 0.55200

The used bushing mentioned above had an O.D. of 0.55055"

I also measure the shaft the bushing ride on, and got the measurements, measuring from the inside out, and both vertically and horizontally (all measurements in inches) :

  • 0.47140, 0.47245

  • 0.47130, 0.47140

  • 0.47170, 0.46420

Finally, I measured the ID of the clutch (part 212), both vertical and horizontally, at both the inside and outside ends with these results :

  • outside : 0.55050, 0.55060

  • inside : 0.55155, 0.55120


bushings

The drawing below is a detail from the Grizzly manual (see references below) showing the idler pulley (#212), the bushings (#207), and the retaining ring (#215). The right hand picture below shows the 9x20 pulleys - the idler pulley is the pulley on the middle left.

Drawing detail

Pulleys - idler pulley middle left.

bushing diagram
9x20 pulleys

Sacrificial "White Plastic Gear" for 9x20 Drive Train

There is a white plastic 80 tooth gear in the gear train that drives the lead screw; it's called a "sacrificial gear" because the idea behind using plastic for this gear is that if there is a jam or similar problem the plastic gear will strip out and save the rest of the gear train from worse damage. If you bought your lathe new, you probably got one or two spares for this gear; if you bought your lathe used, you may or may not have a spare. If you don't have a spare, it;s probably a good idea to have one or two on hand, but they seem to be very hard to find.

In searching the web, I have found some possible sources:

  1. Jet lists what I think is the same part as GEAR 80T BD-920N, but it's a whopping $40.69 (2015 price).

  2. Grizzly no longer provides the plastic part, but lists a metal replacement as P4000119A - GEAR 80T METAL for a more reasonable $18.50. The downside here is that being a metal gear, you lose the protection provided by the plastic version, and risk serious damage to your lathe in the event of a jam.

In a related note, this page provides code for 3D printing 9x20 change gears, and states that the gear parameters are as follows:

  • Thickness: 8mm

  • Bore Diameter: 14mm

  • Keyway Width: 5mm

  • Keyway Depth: 2.5mm

  • Pressure Angle: 20

  • Diametral Pitch: 1 (MOD1 Gears have a DP of 1) [Note: Not sure here whether the original author simply means that these are Mod 1 gears, and has confused this with DP. I'm pretty sure he means Mod 1, but I'm still learning about gears so don't take my word for it.]

Note: As of this date (Sep. 10, 2015) I have not purchased any of the above, so I cannot say for certain if they are the required replacement. When I eventually make a purchase, I will update this note.

[Update Feb. 4, 2021]

Since I originally wrote the above, I have acquired a 3D printer and was able to design and print the sacrificial gear. You can find more details and the required print files here:

https://www.prusaprinters.org/prints/30043-9x20-lathe-sacrifical-80-tooth-gear

References

This model of 9x20 lathe is sold in a number of variations by a variety of vendors and is very popular, so many people have written about its pros and cons, and have offered numerous modifications and improvements. The links below attempt to collect some of the best references for the 9x20 lathe.

A note of caution: Not all 9x20 lathes of this type have identical components; in some cases there are even significant differences between different model years from the same manufacturer. In addition, the manuals are not always accurate. Check and measure the components on your own lathe before ordering replacements or additional accessories.

  • Belts, replacement :

    • According to this link, the the HF45861 takes a p/n: 5M710 v-belt - 710mm (note that the Grizzly G4000 takes a 5M730); the belt is available from MRO Supply and other sources. An alternative suggested in the link cited is the Gates K040275 Multi V-Groove Belt, a wider belt with three grooves which can be sliced into four usable belts.

    • Additional information on replacement belts can be found on Steve Bedair's website.

    • It has been suggested that reducing belt tension can reduce belt wear; done by inserting an S-hook into the tension spring (see photo here).

  • Gears

    • Gear Ratio Chart : Downloadable PDF - feed rates and setting for SAE and metric threads.

  • Manuals

    • Manual for 45681 : Central Machinery 45861 9 x 20 manual from Harbor Freight Tools.

    • Manual for Grizzly G4000 : A much better written manual. The Grizzly G4000 is essentially the same lathe as the Central Machinery 45681 (but be aware there are some differences); this manual is better written and is worth reading.

  • Modifications

    • Chucks and Backing Plates

    • Crossfeed modification : "This modification changes the lead screw to a thick 7/16-20 thread, a larger mount, adds a deep grove ball bearing and a thrust bearing. Plus the hand wheel diameter has been increased from 2" to 3"."

    • Mods and Repair docs : A good collection of documents relevant to the 9x20, including rebuilding, modifications, and installing a DC variable speed replacement motor.

    • Quick Change Tool Post (QCTP)

    • Tumble reverse gear : "A tumble-reverse gear changes the direction of the 9x20 lathe's lead screw so the carriage can feed left to right with the part still turning CCW. This allows selection of automatic feed right to left, neutral, & left to right as well as enabling left-hand single-point thread cutting, if so desired."

    • Variable Speed DC Spindle Motor : "Baldor Model CDP3440 DC motor (USA): ¾ HP, armature 90VDC, 7.6A full load, 1750RPM, Permanent Magnet (PM), & Totally Enclosed Fan Cooled (TEFC)."

  • Websites related to 9x20

    • BedairMachine Works : Steve Bedair's website has lots of information on 9x20 mods and projects.

    • 9x20 Discussion Forum : https://groups.io/g/9x20lathe

    • Home CNC Technologies : Jeff Davis's website is not just CNC; follow the Enco 9x20 Lathe link as well as the More Modifications link for a DC motor install.

    • Introduction to 9x20 Lathe Operations : [PDF] An overview of basic operations for the beginning lathe user.

    • Jerry's Metalworking Links : Discussion and downloads related to the 9x20 lathe.

    • Stellar International : The original site no longer exists, but fortunately the site was archived at the link given. Various 9x20 mods and improvements discussed include: Gear Clutch, Chipguard. Dog Clutch, Saddle Lock Lever, Power Cross-Slide, Digital Read-Out, Reverse Tumbler, Phase II QCTP Mount & Rear Toolpost, DC Motor, Hand Crank, Tap Holder, Phase II Flange Nut Lever, Revolving Tailstock Drive, Coolant Pump, Hand Wheels, Tailstock Lock.

    • Smitty's 9x20 Lathe Homepage : Includes modifications, projects, and a useful links page. (Update Feb. 2021 :link is now to archived site)