Harrison L5a Feed, gearbox and drop gears

[mark cordallParticipant @markcordall83541]

Hello,

Am looking for a little help on a Harrison L5a i've just aquired. I believe the machine to be an L5A, its the type with a 3 speed feed gearbox.

The handle for the 3 speed box is on the left hand end of the headstock, and labeled B C A. I suspect a detent or similar is broken as the lever can freely be swung about 180º and hence very hard to get any gear to engage. Does anybody have any experince pulling these apart? Or some sort of a diagram before i swear and end up with bloody knuckles!!

Also, what is the correct layout (actual physical positioning, not gear size) for the change gears? This machine has 3 gears fitted (50 top, 70 centre, 80 bottom) Both the centre and bottom shafts have a huge pile of washers acting as a spacer which looks wrong? And i seem to recall from looking at another machine that the centre shaft should have 2 gears stacked on it?

Any help greatly appreciated.

[mark cordallParticipant @markcordall83541]

[OldironParticipant @oldiron]

Sorry but have no knowledge of the L5A but this might help. Harrison . pdf  Its a free download, Hope it helps

regards

Edited By Oldiron on 11/03/2020 18:22:48

[mark cordallParticipant @markcordall83541]

Thanks, just what i needed. Looking at page 31 items 29 and 30 are spring and ball. Am thinking this is whats broken, lets hope i can acess them via the handle, so no need to strip down. As for change gears, it seems that for certain feeds it's a matter of 2 cogs stacked on the centre shaft. I'll just make some tidier spacers.

I can't seem to find any description of what actually changes between the 3 gears of A, B and C. Maybe A is the feed per rev as listed on the chart and B C are fater and slower? I'll just have to experiment.

[KettrinboyParticipant @kettrinboy]

The BCA gearbox gives 1:1 drive ratio on middle "C" position 1:2 on "A" position and 2:3 on "B" position , you only need two gears on the middle shaft for a compound train , most of of the time a simple 3 gear train is enough formost threads and feeds depending on what changewheels you have available of course.

[Nigel Graham 2Participant @nigelgraham2]

The "huge pile of washers" is not "wrong" functionally so much as untidy. Yes, some neat new spacers would be welcome there.

I am pretty sure you can service that detent without removing more than the handle.

That gearbox can trip you up. It drives both the feed-shaft and lead-screw and whilst it can help extend the possible thread range, the one you cut will agree with the change-wheels alone only if the gearbox is in the 1:1 ratio.

(What do you mean, how do I know?)

On the other hand, you can use it to co-operate with suitable change-wheels to set a super-fine self-acting feed for finishing cuts.

Verify the actual spindle pinion tooth-count agrees with that given on any screw-cutting tables you have for the machine. On my Harrison it seems fixed and not changeable, and is not the one quoted so I have to calculate the wheel-train each time.

;;

A tip to help you keep the lathe clean. Obtain an oddment of standard, round PVC rainwater down-pipe, cut two pieces; one the full length of the headstock, the other ditto the box part of the bed at the tail end. Cut them lengthwise to form two "gutters" slightly under their radius, in depth, to a gentle push-fit under the shears below the two stocks. They stop the huge voids in the bed from filling with oily swarf, and direct any oil leaking from the headstock into the chip-tray.

For sweeping out the chip-tray on both the Harrison and the Myford lathes, I use old paint-brushes, with a child's plastic toy beach-spade about 8" long as a "dustpan".

(Oh, and I tend to use the tail-end PVC "gutter" on the L5 as a handy little temporary tool-shelf, too!&nbsp

[mark cordallParticipant @markcordall83541]

Thanks for the replies. Good to now know what the B, C, and A actually give me.

The spring and detent ball had gone AWOL. It's accessed from the inside face of the lever, and the lever is just held in place by a grub screw, so an easy fix,,,, sort of.

The shaft that the handle goes onto has been badly mauled, so it's not possible to determine where the grub screw should locate. The shaft rotates so easily and it's so vague to determine when it drops in/out of gear it's going to take a bit of work to try and get the handle clocked back at the correct position.

[Nigel Graham 2Participant @nigelgraham2]

I've found that gear selection on mine can be a bit vague too…

Your thread has made me think I ought examine the machine and see if in fact the detent is a) there and b) working!

[mark cordallParticipant @markcordall83541]

If you undo the grub screw and then pull the handle off i'm presuming there is some sort of recess that the grub screw locates into. On mine this recess is now a "slot" it appears the handle has been forced to rotate on the shaft a few times. Hence i have no obvious way of re-aligning the handle in the correct position.

[Nigel Graham 2Participant @nigelgraham2]

Oh dear! Has someone in the past has abused that machine, possibly by trying to change gear with its drive running? Thinking about it, there should be very little load on that selector though the gear-box may need help by rotating the spindle by hand to align everything..

However, I am a bit puzzled now, and will need to examine my Harrison closely to understand what is damaged on yours.

On my example at least, the selector handle is retained by a nut on a fixed fulcrum pin, has the detent at the top end, and a rigidly-mounted pin at the bottom end that passes through a slot in the casing to engage the selector itself. No grub-screw anywhere.

[mark cordallParticipant @markcordall83541]

Yours sounds different to mine (and page 31 of the pdf linked above) I’ll take a picture next time I’m in the workshop.

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