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Myford 254 thread dial indicator

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Philip Slater08/09/2019 19:03:38
20 forum posts

Hi

Would anybody be able to tell me where I can obtain a thread dial indicator for the the Myford 254 please.

Philip Slater09/09/2019 09:47:34
20 forum posts

Hello again I'm guessing from the lack of response that thread dial indicators are not available anymore. Certainly all the Google searches that I've done don't show anything, plenty of Myford super 7 TDIs but nothing for the the 254.

Is it feasible to cut threads by closing the leadscrew half nuts and using forward and reverse motor directions for each cut. Obviously not disengaging the half nuts until the threads complete. I've got a DC brake fitted to the lathe which stops the chuck instantaneously.

Neil Wyatt09/09/2019 10:46:57
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Posted by Philip Slater on 09/09/2019 09:47:34:

Is it feasible to cut threads by closing the leadscrew half nuts and using forward and reverse motor directions for each cut. Obviously not disengaging the half nuts until the threads complete. I've got a DC brake fitted to the lathe which stops the chuck instantaneously.

That's the usual way; reversible lathes are often supplied without thread cutting indicators.

Neil

Philip Slater09/09/2019 11:14:56
20 forum posts

Thanks for that. Maybe not so good on the motor and all the switch gear but looks like the only way out.

Phil

not done it yet09/09/2019 11:27:57
3344 forum posts
11 photos

Nearly everyone with a metric lathe needing to cut imperial threads do it that way. Same for those with imperial lathes who wish to cut metric threads...

Clive Hartland09/09/2019 12:19:39
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2473 forum posts
40 photos

I have the sales brochure and available parts for the 254. the part. no. 95/136 for metric threads, in the listings priced at £100.81.

Note. it is only for use with metric threads. it goes on to say that if used with the imperial conversion set. 95/078 on a 254 lathe the leadscrew nut must remain engaged.the part no. for the imperial thread ind. iis 95/105 and cost £36.89.

Hope this is some help Clive

speelwerk09/09/2019 12:38:45
331 forum posts
1 photos

Is it not possible that the imperial TDI is the same as used on the 7 series? Niko.

Philip Slater09/09/2019 17:15:36
20 forum posts

Thanks Clive I'm assuming the sales brochure you have is from when the lathe was in production or are you suggesting that the parts are still available, in which case I'm all excited. My lathe is metric I had a similar thought that the 7 series TDI might be compatible but it's a 3mm pitch leadscrew.

lfoggy09/09/2019 17:34:47
72 forum posts
5 photos

I have a metric 254 with the 3mm pitch leadscrew and it has an indicator fitted for cutting metric threads. It is a simple device and it would be possible to make one. It is basically a metal body which holds a gear against the leadscrew. There are two gears to choose from (28 and 30 tooth) depending on what pitch you are cutting. There is a dial with divisions connected to the gears that then indicates when to re-engage the half nuts. The metal body would be basic machining and you would need to be able to cut the gears You would need to find an original to copy, particularly for the divisions on the dial.

If you are anywhere near Birmingham you are welcome to inspect and measure up mine....

Philip Slater09/09/2019 19:09:58
20 forum posts

Thanks for the offer Ifoggy I'm up in North Lincolnshire so a bit far to travel. I've never machined gears but I've got a milling machine so have the tools. Thinking aloud I wonder if I could machine the gears from Tufnel. Not sure what you mean by having 2 gears, are you saying you need to change gears on the Thread dial indicator?

DC31k09/09/2019 19:57:59
58 forum posts
Posted by Philip Slater on 09/09/2019 19:09:58:

I've never machined gears but I've got a milling machine so have the tools. Thinking aloud I wonder if I could machine the gears from Tufnel. Not sure what you mean by having 2 gears, are you saying you need to change gears on the Thread dial indicator?

Do not be alarmed: a thread dial indicator is in no way a precision mechanical device. Almost any kind of tooth shape will work; the important thing being the number of teeth (even so far as straight gashes around the perimeter of a thin gear.

You would do very well to buy Martin Cleeve's book on screwcutting as it probably the most concentrated source of information on leadscrew indicators out there. You can also search this site (using Google with site:model-engineer.co.uk as part of the query string - since the forum search is totally useless) as the subject has been done to death here as well.

Very briefly, thread dial indicators for an imperial leadscrew are very simple because of the way imperial threads are defined (teeth per inch) and one gear will do all pitches.

TDI for metric leadscrews are more complicated because metric threads are defined by pitch. One gear will not do all pitches. However, in some ways metric pitches are simpler because any pitch that is a factor of the leadscrew pitch does not need an indicator at all - you can drop the nuts in anywhere they will engage.

For your 3mm pitch leadscrew, this means 3.0, 1.5, 1.0, 0.75, 0.6, 0.5, 0.3, 0.25 and 0.2 pitch threads do not need a gear. The remaining common ones (especially 1.25 and 1.75) will need an indicator gear (1.25 needs a gear with teeth 'by fives' and 1.75 needs a gear with teeth 'by sevens'.

Philip Slater09/09/2019 20:04:30
20 forum posts

Very interesting. As your probably realising I still consider myself a novice when it come to machining. Looks like I need to be getting that book you mention. Thanks for the input.

Clive Hartland09/09/2019 21:48:02
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2473 forum posts
40 photos

Hi Phil, the brochures are 1999 vintage so not current and as you say the lathe is out of production.

I had just purchased an ML10 so wanted the brochures to get bits I wanted.

Clive

ian j09/09/2019 22:51:52
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271 forum posts
240 photos

Phil.

May be worth emailing David of "Quillstar" as he says on his web site

A few 254 bits including lathe beds, aprons, tailstocks, screws, nuts, dials etc. "

http://www.quillstar.co.uk/

Quillstar

not done it yet09/09/2019 23:50:13
3344 forum posts
11 photos

Using a plastic gear against the lead screw would reduce any risk of wearing the lead screw. A spur gear will wear in OK as there is no real load on it.

lfoggy09/09/2019 23:52:44
72 forum posts
5 photos

There are two gears on the indicator and you choose the one appropriate for the pitch you are cutting. The gear is selected by undoing a nut, removing and replacing the gear. As stated above, as long as the tooth count is correct it wont matter too much if the tooth profile on the gears is not perfect. If you are planning to do a lot of thread cutting I think making an indicator is definitely a realistic prospect.

Thor10/09/2019 05:14:41
1116 forum posts
31 photos
Posted by Philip Slater on 09/09/2019 19:09:58:

Thanks for the offer Ifoggy I'm up in North Lincolnshire so a bit far to travel. I've never machined gears but I've got a milling machine so have the tools. Thinking aloud I wonder if I could machine the gears from Tufnel. Not sure what you mean by having 2 gears, are you saying you need to change gears on the Thread dial indicator?

I used Delrin to make a 28T gear wheel for my metric lathe (3mm pitch leadscrew), it has worked well for many years so Tufnol (sheet) should work well. A 30T gear was supplied with my Thread Dial Indicator.

Thor

Edited By Thor on 10/09/2019 05:15:01

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