Myford change gears

[dickdastardly40]

Hi Y'all

I'm just thinking about cutting some threads on my super 7 ad thought I'd better sort out the gears. On closer inspection I see that 2 of them do not have the keyway but a hole, (I hope the url comes out). They are a 55T and 20T. These will obviously not fit onto any of the keyed shafts so unless they go in place of the tumble sleeve gear which I haven't removed I'm clueless.

It's entirely possible they are nothing to do with a Myford, but if anyone can shed any light I'd appreciate it.

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The gears I do have are:

75T x 2
70T
65T
55T X 3
50T
45T
40T X 2
38T
34T X 3
30TX 2
20T X 4

If I have any glaring ommisions or too many of a certain flavour I'd also appreciate a nudge.

Best Regards

Al

[chris vine]

Hi Al,

The gears with holes were how a lot of lathe change gears used to be made. They were not so good because the drive pin tended to push them a bit scew squew (how to you spell that?).

Some of the earlier (before ml7) were of this type, maybe from an ml4? or Tyzack etc etc.

There have been lots of tables published before in ME for gear trains for screw cutting if the plate on the lathe does not help.

Chris.

[Myford Matt]

That'll be 'skew' Chris

[Phil Sutton]

Or even "askew" ;D

Phil

[steammadman]

Check the teeth are the same, if they are file a keyway in yourself, a bit of good fitting experience, at least that's what we were told as apprentices.

[alanstepney]

There is a chart showing the gears needed for most threads at:

www.alanstepney.info/thread_cut_8tpi.xls

[dickdastardly40]

Thanks for the assistance, the teeth certainly look similar,

Filing keyways or shaping them using the crossslide is certainly on the cards if I find I need the gears.

Best Regards

Al

[Tel]

steammadman said:

Check the teeth are the same, if they are file a keyway in yourself, a bit of good fitting experience, at least that's what we were told as apprentices.

Now here's a little tip for yers. Turn a close fitting disk and put it in the 'ole in the gear, now drill a key sized 'ole on the joint line, remove plug, file the 'arf circle into a 'arf square - matter o' minutes.

[Boadicea]

Beware of the material the cogs are made from. Some are cast iron and some are steel. If you mix the two, one of them wears. I leave you to guess which ones wear and which are the cheapie imports!!

Life is never simple and you get what you pay for (sometimes).

Regards, Bo.

[Tony K]

dickdastardly40 said:

It's entirely possible they are nothing to do with a Myford, but if anyone can shed any light I'd appreciate it.

The gears I do have are:

75T x 2,70T,65T,55T X 3,50T,45T,40T X 2,38T,34T X 3,30TX 2,20T X 4

If I have any glaring ommisions or too many of a certain flavour I'd also appreciate a nudge.

Best Regards

Al

Dear Dick, assuming you have an 8tpi imperial leadscrew, I reckon you need the following to cut imperial screws....

20 (2off) and one off of the following....
25,30,32,35,38,40,45,50,55,60,65,70,75.
I think that is a standard set of 15.

If you want to cut metric screws, then I think you need the following additionals, 1 off of each....
21,27,33,36,39,42,48,50,80 plus 2 off 63. I think this is the standard issue set of 11.

Emphasise, the above is for the imperial leadscrew, the metric 3mm leadscrew is different.

I hope this helps and I am sure when you cut your first thread it will give great pleasure. After all - you can't beat a good screw!! ;D

Regards, Tony.

[dickdastardly40]

Thanks for that Tony, Also just what I was after!

I have been fortunate in the amount of screwing I have done away from home in my complicated life, but in the past have also been fortunate to be using a gearbox on a Harrison or Colchester.

Screwing at home, which is all I can do now, is done on my Myford. The price of promotion is the desolation of a desk job.

Regards to everyone!

Al

[dickdastardly40]

Sorry to harp on about this, I just tidied up a bit and found an unregarded 127 tooth gear hiding under the faceplate.

I would guess this is something to do with metric conversion as being half of 25.4:1 inch but it is not mentioned in any of the charts I have seen.

Any steers on how to fit it would be appreciated.

Regards

Al

[chameleonrob]

thats exactly what its used for, I think that the myford is too small to put it on (never owned a myford so I'm sticking my neck out here) but a larger lathe like a boxford would need one for cutting metric theads. I would guess most of the charts were drawn up with the myford (or a similar) in mind.

rob

[Tony K]

dickdastardly40 said:

Sorry to harp on about this, I just tidied up a bit and found an unregarded 127 tooth gear hiding under the faceplate.
I would guess this is something to do with metric conversion as being half of 25.4:1 inch but it is not mentioned in any of the charts I have seen.
Any steers on how to fit it would be appreciated.
Regards
Al

Mr. Dick, the ratio of 127 is the first whole number multiple of 25.4 and you are correct in working out that it could be used for some sort of metric/imperial conversion.

However, there is no mention of a 127 wheel in the handbook when using metric or imperial leadscrews for turning either metric or imperial screwthreads (either way).

The 127 wheel is sold by RDG tools for the Myford and, hopefully, should fit on it, probably on the leadscrew.

It could be used for a gynormously fine thread which is way off the scale, but I suspect it is used, not for cutting threads, but simply to get a very fine feed. It seems an odd number to use, but it may be simply the maximum size of wheel the Myford can accommodate.

I have asked Myford the question and what wheels you might use with a 127. If they answer I will let you know.

Anyway, what a lucky boy you are - cos I aint got one!

Kind Regards, Tony.

[Tony K]

I have asked Myford the question and what wheels you might use with a 127. If they answer I will let you know.

Myford have answered that they can supply a 127 wheel for £33.74 plus p&P, Vat etc., but have avoided the question of what it might be used for.
Regards, Tony.

[jackrae]

The 127 wheel is the only wheel size that will fit onto a myford that creates an EXACT metric thread when used with an imperial lead screw. All other fancy gear combinations do not give an exact metric thread but for all normal purposes there is no need for such perfection.

The 127 fits onto the lead screw but the gear door has to be left open since its internal dimension is smaller than the wheel diameter - at least my one is.

Yes, I have a 127 but have never used it - but it's there just in case !!

jack

[SteveW]

Guys,

If you are after cutting metric threads on an 8 tpi lead screw you can to within a few thousandths of a millimetre using the standard gear set and a program I outlined here a year or so back.

The required URL is: metal.duncanamps.com/software.php

You need to bracket the require thread pitch and let it rip. The you choose the gear set nearest to the target thread.

The only other thing you need is a fag packet to write the numbers on 'cus there ain't a print option.

[Tony K]

Thanks for that - it looks like we have completed the circle, as they say.

Just to add to Bo's point about gear wheel materials - Myfords are made of machine tool cast iron but most of the Hong Kong ones are made from steel. Sure enough they will be strange bedmates if you do much screw cutting with a mixture.

Who will volunteer to form the "127 Club". Only those elite with one can join ;D

Regards, Tony. (now minister without full portfolio of gear wheels!)

[Deleted]

Hi
Just checked and i've got a 127 for my smart & brown, its also got a gearbox. There's a table on the inside of the cabinet door that tells you which combination of changegears and gearbox setting to use for metric and BA pitches, also for diametric threads ( whatever they are? if anyone knows please tell!)
If you don't have a 127, as someone else has said a close approximation is probably good enough.
For instance a 1mm pitch is 25.4 TPI, so if you cut a 25 TPI thread it is only 16 thou out over a full inch, thats less than 1 thou per thread which is probably good enough, how accurate is the pitch produced by a tap or die, also how accurate are commercial nuts and bolts?
Regards
Trevor

[Tel]

stevew said:

Guys,

The only other thing you need is a fag packet to write the numbers on 'cus there ain't a print option.

'Screenhunter' or similar will give you a practical way of printing the results out, thusly;