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myford ML7 21/56T Backgear dimensions

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Saeed Najafi11/08/2021 15:54:46
2 forum posts

Hi friends
I've bought an old 1957 ML7. the 21/56T backgear is not included and lost.
I want to know the diameter and thickness of each clustered gear.

Could anyone please help me with this problem?

Grizzly bear12/08/2021 21:07:08
300 forum posts
8 photos

Hi Saeed,

For starters: Myford Ltd Home Page (British Engineering at its best)

Good luck..........

DMR12/08/2021 23:43:31
124 forum posts
14 photos

I am not an ML7 man so cannot do the dimensions but as Grizzly says. you can buy the part from new myford for 65 quid all in. Much easier than trying to make the ganged assembly which would have to be in steel. Do you have the Back Gear Eccentric assembly that it fits onto plus the 2BA x 1/2" socket countersunk screw and washer that hold the gear in place?

www.myford.co.uk/acatalog/B50.-21-56T-BACKGEAR-CLUSTER--70-1218-40.html

Dennis

DiogenesII13/08/2021 07:44:31
520 forum posts
202 photos

The mesh with the changewheels looks 'right', so on that basis are of the same form, 20DP with a 14.5PA..

The small gear is 5/8" (16mm) thick, the larger one narrower (because it has to fit between the large pulley and bullgear) looks to be a nominal 7/16" - mine came out at 11.76mm with calipers..

I can't measure the diameters because the gears are in situ, but you should be able to calculate the OD for the blank from the toothcount and DP - er, 56+2, divided by 20 = 2.9"?.. ...21+2 divided by 20 = 1.15".. ..assuming DP is indeed 20.

I'm not sure what or whether any allowance need be made for running clearance?

..It would be useful if someone else would check and confirm or correct this post if necessary..

I'm fairly sure the original gears are in cast iron, as per the changewheels.

Saeed Najafi13/08/2021 10:08:11
2 forum posts

Thanks a lot

Brian Wood13/08/2021 10:19:06
2549 forum posts
39 photos

Hello Saeed,

If you are able to, it will pay you to machine a shallow oil groove along the eccentric pin that the backgear cluster runs on so oil can readily reach the extremities of the oilite bearing bush A single hole can get choked.

Regards

Brian

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