Harrison 9" and Harrison 140 change gears

Hi! I work in school's Design and Technology department and presently trying to sort out which parts fit with which particular machine. We have two Harrison lathes, one is a Harrison 9" L5 type and the other is a Harrison 140 which has an 11" swing and is a gapbed lathe, also an L5 type. I need to find out which of the loose gears match which machine, so that they can be stored with the relevant machine as neither machine is kept in the same room.

Below shows the gears with their number of teeth which are currently fitted to the machines and a list of the loose gears I have. Where there is a number in brackets following the quantity of teeth, this indicates how many gears there are of that size and teeth number.

Harrison 9" - fitted gears: 20/80/100 Harrison 140 - fitted gears: 25/100/80

Loose gears for Harrison lathes : 40(x2) / 50(x2) / 60(x3) / 63 / 65 /

70 / 80 / 120 / 127

Any help would be greatly appreciated!

Howard :=AC)

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Got the manuals?

In general the manuals will list the standard accesories for each lathe. If you don't have them, you could do well to track some down. They will also contain the screwcutting charts and trains.

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There is some info to start with. Manuals are available from this source, and may still be available from Harrison themselves. As noted in the text of the website, there are several versions, and the right manual may require a bit of sorting of details.

Given that there are not a large number of gears, this looks more like the gears that are used to allow cutting of different thread series than standard, such as metric, or diametric pitch thread pitches. You want to look for charts showing the different gear trains for these thread pitches, to see which are required for each lathe. This will aid in sorting them a bit. On some lathes the info for the geartrain between the head and the gearbox is right on the pitch chart on the gearbox, some have it inside the cover over the gears, others, it's in the manual.

Cheers Trevor Jones

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Trevor Jones


It may well be that the gears fit both lathes. The 127 tooth gear is certainly a metric/inch change gear.

If the lathes have the quick change boxes for cutting threads, then the gears will allow the cutting of "odd" pitches not on the gearbox info plates. Some of these "odd" pitches may be for the worm for worm gear sets using standard DP/Mod gears. With an 8 TPI leadscrew you will have a compound gear combination of 55/35 as this is the pi approximation needed. Most likely you should verify that that the correct pick-off gears are installed for the qc box to generate the threads specified.

If one or both lathes lack a qc box, then you will need to set down and calculate what theads you can produce with the gears you have, and perhaps order others. You also might contact the manufacturer and see if they have operating manuals available.

Harrison now appears to be part of the Clausing family. Their URL is

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While it won't be cheap, the manuals are also available from
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Harrison lathes appear to be very well built.

Unka' George (George McDuffee) .............................. Only in Britain could it be thought a defect to be "too clever by half." The probability is that too many people are too stupid by three-quarters.

John Major (b. 1943), British Conservative politician, prime minister. Quoted in: Observer (London, 7 July 1991).

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F. George McDuffee

On my L5 there is a plate riveted inside the gear cover door with the thread pitches/slidign/surfacing feed and which gear combinations to use. Ill look tommorow and let you know what it says.

think the 140 and the L5 use the same gears anyway.


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The standard set of changewheels supplied with the 9-inch lathe (20,

40, 50, 55, 60 x 2, 65, 70, 80 and 100) provided 26 threads from 2.5 to 40 tpi (with the option of a 120t wheel to give an additional 7 threads up to 80 tpi) whilst those with the standard 11-inch lathe enabled 33 threads from 2.5 to 80 tpi to be generated.

So they are an incomplete set and a half from the looks of it. not sure where the 63 fits in though...

the 127 is a metric thread cutting conversion gear (25.4*5) Dave

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63 is a common conversion gear for imperfect metric conversions. Very often these imperfect conversions are quite beyond anyones ability to measure, but they make great fodder for bored math whizzes to argue over.

Cheers Trevor Jones

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Trevor Jones

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A strong suggestion for when you identify which is which. Degrease them all, and then paint the area between the teeth and the hubs a unique bright color for each machine -- say yellow for one, and green for the other, so it will be easy to tell which machine they belong with. If the chart is not on the inside of the gear cover, also paint the inside of the cover the same color -- and perhaps the spider and any standard gears which are currently mounted.

Good Luck, DoN.

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DoN. Nichols

replying to doodibloo, bill wrote: according to the manual the 140 and L5 gearsets are same fitting however the manual states that L5 gears are all whole numbers apart from a 45 and 65... the full L5 set is dependent on which actual gear is fitted for threading and whether it's imperial or metric, if it's only 3 position imperial the gears are

20,40,50,55,60,65,70,80,100,120 with 2 of 60..... .adding the 127 gives metric threads... hope that helps
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