Granville lathe leadscrew change wheel

[JACK SIDEBOTHAMParticipant @jacksidebotham67303]

can anyone produce a replacment change wheel for my Granville lathe???,l dont posses the tools to do it myself,l am currently trying to source the wheel l need but maybe there is a helpful soul out there that would be willing to cut one for me??,l would,of course,cover the costs incurred,l can provide a good colour picture of what l need together with the needed dimensions,thanks.

[cogdobblerParticipant @cogdobbler]

What DP are the Granville gears? You might be able to use gears off a more common lathe that used the same DP. Eg Myford 20 DP. Drummond 14 DP.  And I forget Boxford’s.

[BazyleParticipant @bazyle]

Granville are 20 DP according to Tony
https://www.lathes.co.uk/granville/index.html

So worth checking how close Myford centre hole and keyway are. You should be able to adapt.

For the record, Boxford are 18DP.

[John HinkleyParticipant @johnhinkley26699]

Bazyle beat me to it!  If you get completely stuck, pm me the details and I can print out a couple in either PLA – carbon fibre or glass fibre reinforced filament, with your choice of pressure angle, or both.

John

 

[Martin ConnellyParticipant @martinconnelly55370]

A look at HPC website HPCgears.com technical section will help you to identify what gear form you have. At this stage I would not worry about pressure angle or material, you will not be putting a lot of power through a change gear in a home workshop. You may find HPC have a suitable part as well.

Martin C

[cogdobblerParticipant @cogdobbler]

The Myford gears have a 5/8″ bore with a 1/8″ keyway. Should be adaptable. Plenty on that auction site, but they are not giving them away of course.

[cogdobbler]

On cogdobbler Said:

Plenty on that auction site…

It could be sensible to find out the required tooth count before running around all the cheese shops only to find they just sold the last one yesterday.

[DiogenesParticipant @diogenes]

Yes, let us know what dimensions you have – if something common can be made to fit you never know what people might have lying round under the bench.

..plus you might well find a couple of years down the line that it becomes desirable to have other/different tooth counts..

EDIT – just noticed you have placed an ad, in that case definitely post some more details, ‘cos you’ll be more likely to a receive a better response if you can describe what you need in terms of describing the gear, rather than the (rather niche) lathe brand, maybe?

[JACK SIDEBOTHAMParticipant @jacksidebotham67303]

Hello all,l am  amazed at the help and advice my humble request has generated!!!,l am grateful to you all,if l can work out how to do it l will attach a picture of what l am after to this reply,the pictures l have came from Tony@lathes.uk,l can turn up a suitable “blank” but l have no access to any form of dividing gear or tooth cutting equipment,again,very many thanks to everyone.ps….the wheel l need is the one on the leadscrew in this picture with a slot head grubscrew in it.

[DiogenesParticipant @diogenes]

What size is the hole in the middle?

Does it have a key slot, if so how wide?

How many teeth does it need to have?

[duncan webster 1Participant @duncanwebster1]

Myford gears are 14.5 degree pressure angle. Most gears nowadays are 20 degrees. No idea what Granville gears are, or the effect of running a mismatch. No doubt someone will know, also how to measure PA

[JACK SIDEBOTHAM]

On JACK SIDEBOTHAM Said:

Hello all,l am  amazed at the help and advice my humble request has generated!!!,l am grateful to you all,if l can work out how to do it l will attach a picture of what l am after to this reply,the pictures l have came from Tony@lathes.uk,l can turn up a suitable “blank” but l have no access to any form of dividing gear or tooth cutting equipment,again,very many thanks to everyone.ps….the wheel l need is the one on the leadscrew in this picture with a slot head grubscrew in it.

I think you will find that that gear is a plain flat gear like all the others and the collar with the grub screw in it is a separate piece.

The whole set up looks extremely Myfordesque, right down to the small screws on the ends of the studs to retain the gears.

If so, the gear you need will have the same hole and keyway in it as the other gears, which you presumably have? If they have copied Myford closely, that will be 5/8 hole and 1/8 keyway.

The gear train shown in your posted picture is set up for screwcutting. For normal turning fine feed you want the biggest gear possible being driven by the smallest possible, using compound gearing on both banjo studs.

Have a look at the many Myford change gear charts , diagrams and pics online to see how it’s done.

Typically, you want a 20T or less on the tumbler reverse output, driving a 60T paired on the same stud with a 20, driving a 65 paired with  25, driving a 70 on the leadscrew.

[cogdobblerParticipant @cogdobbler]

This might clarify my ramblings above.

[Martin of WickParticipant @martinofwick]

Slavishly copying the gear in the photograph of some random  lathe set up is not likely to help you.

To expand on cogdobbler’s post, you will need to review the change gears that you already have and then assuming only want to get one gear,  decide what feed rate per rpm you want. Typically for finishing work this will be in the range .002 to .005 thou for finish turning. Then use the charts or calculate the no. teeth required on the leadscrew gear to deliver that feed. It is likely to be a relatively large gear in the range 65 to 85 teeth.

You may also want to consider an additional gear to give you a roughing feed rate of .010 to .020 thou if you do not wish to purchase a full set of gears.

No need to be concerned particularly about pressure angles in this application, ideally best if the same on meshing gears but the world isn’t going stop if not.

As already  explained, your best option is to source a Myford change gear from the usual online markets in the cost range £20 to £30 for larger gears.

[cogdobblerParticipant @cogdobbler]

A Myford collar with grubscrew might fit the end of that leadscew too. From memory there is also a blank spacer that fits on there next to it too. Should be shown on the exploded parts drawings on the Myford website.

Bit tricky to make at home as they have an internal keyway. You can cut the keyway in the lathe by racking the carriage back and forth with a boring bar with toolbit turned sideways but it soon wears out your wrist! I think aluminium alloy would make the job easier, and be strong enough for this application.

[John HinkleyParticipant @johnhinkley26699]

Or, like I said, I’ll print one out for you and it won’t cost you anything!

John

 

[Howard LewisParticipant @howardlewis46836]

With an old British lathe, the gears are likely to be 14.5 degree pressure angle, so not suitable to mesh with a modern gear which will be 20 degree.

If the gears are 20 DP, they are the same as Myford, which are 5/8″ bore.

So you might need to make your own studs to mount them on the banjo.

You might need a spacer to go on the Leadscrew, to bring the different meshes into line, especially when using compound gear trains

Myford gears increment in 5s from 20T upwards to 75 or 80.(Always worth having two or three 20T gears to enable compounding, for fine threads or very low feed rates)

If you might ever want to cut Metric threads, if it will fit in, a 127T (6.45″ diameter!) will do the conversion perfectly. Failing that, as long as you are prepared to accept errors (Which may not cause problems over short distances) you could use a 63T, in the train.

Howard

 

[Graham FlavellParticipant @grahamflavell13482]

Jack

As a Granville Senior owner i can confirm that standard readily available Myford changewheels are identical to the Granville ones. The Granville is essentially a slightly beefed up ML7. Chucks and faceplates are also interchangeable. Attached is a picture of the Gear Chart for the Granville although any gear chart for a 8 TPI leadscrew will work.

Regards

Graham

[JACK SIDEBOTHAMParticipant @jacksidebotham67303]

thanks graham,good to hear from a fellow granville owner,l have the gear data plate for my lathe,but it is almost unreadable-someone has been very heavy handed with the brasso in the past,l plan on finding someone to produce a copy if possible as l dont think my original can be saved….l had a feeling that the change wheels might be the same as myford,my plan is to purchase a suitable myford gear and make a carrier for it to mate to the leadscrew,all the best,jack.

[JACK SIDEBOTHAMParticipant @jacksidebotham67303]

To everyone that has taken the time and trouble to respond to my original post–thank you one and all!!!–your advice and support is nothing less than salutory and l appreciate it greatly,l will post pictures of my final solution in due course,now,does anyone know how to restore brass data plates??,thanks again,jack.

[Graham FlavellParticipant @grahamflavell13482]

Jack

I don’t understand the bit about the carrier for the leadscrew. The changewheel just slides on the leadscrew and is held on by a simple collar.

Regards

Graham

[Howard Lewis]

On Howard Lewis Said:

With an old British lathe, the gears are likely to be 14.5 degree pressure angle, so not suitable to mesh with a modern gear which will be 20 degree.

If the gears are 20 DP, they are the same as Myford, which are 5/8″ bore.

So you might need to make your own studs to mount them on the banjo.

You might need a spacer to go on the Leadscrew, to bring the different meshes into line, especially when using compound gear trains

Myford gears increment in 5s from 20T upwards to 75 or 80.(Always worth having two or three 20T gears to enable compounding, for fine threads or very low feed rates)

If you might ever want to cut Metric threads, if it will fit in, a 127T (6.45″ diameter!) will do the conversion perfectly. Failing that, as long as you are prepared to accept errors (Which may not cause problems over short distances) you could use a 63T, in the train.

Howard

 

63t is used as a driver, not an approximate half size driven.

[cogdobblerParticipant @cogdobbler]

63/80 gives a ratio of 1:1.269. More than close enough to 127 for practical purposes in the hobby workshop.

Even better, you can use the standard gear set “by fives” to cut metric threads within 1 in 3000 to 8000 accuracy if you use compound gearing.

[cogdobbler]

On cogdobbler Said:

63/80 gives a ratio of 1:1.269. More than close enough to 127 for practical purposes in the hobby workshop.

Other candidates:

33:26
47:37
52:44
61:48
66:52
75:59
80:63
94:74
99:78

Even better, you can use the standard gear set “by fives” to cut metric threads within 1 in 3000 to 8000 accuracy if you use compound gearing.

True, but can anyone explain how the necessary compounds are calculated?   My book is clear as mud!  Continued Fractions blow my tiny mind.

Worth checking before buying a 127 toothed gear because it may be too big to fit the lathe.     63 toothed gears and other alternatives will definitely go.

Dave

 

[BazyleParticipant @bazyle]

Many early Myford lathes had a printed plate that started with 21 ie 63/3 to make for smaller (cheaper) gears. Other versions provided 46 & 73 as the special extras to the normal 11 gear set for everything imperial. The Groups.io forum for Drummond has these tables. https://groups.io/g/drummondlathe
For the calculations, as you obviously have internet, search for threading calculators. You just give the program a list of the gears you have and are thinking of buying and it works out the best combination. Amazing how little guys in workshops worked it all out on their abacus back in our youth.

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