By continuing to use this site, you agree to our use of cookies. Find out more
Forum sponsored by:
Forum sponsored by Allendale Nov 29

Colchester Student 2500 (Harrison M300)

Thread dial Pick gears

All Topics | Latest Posts

Search for:  in Thread Title in  
damian noble05/06/2018 17:36:04
avatar
144 forum posts
73 photos

Hi all,

Having recently acquired a modern type Colchester student (1997 vintage) I have noticed I'm missing the thread dial pick gears except the 16 tooth one that's mounted on it.

The other gears are 14T, 18T, 20T, and 22T.

Other than the 600 group (probably a fortune) does anyone have any or know where to get any?

Cheers

Damian

David Standing 105/06/2018 19:08:22
1176 forum posts
43 photos

eBay?

 

 

Edited By David Standing 1 on 05/06/2018 19:08:52

Andrew Johnston05/06/2018 19:57:41
avatar
4449 forum posts
516 photos

Presumably the lathe is metric, rather than imperial where you only need one gear? Assuming metric I'd agree with David that Ebay is your best bet, albeit not a very good one. Thread indicators for the M300 seem to come up every now and again, but I've never seen just the gears. Alternatively you could make them. Technically I think they need to be helical gears, but I expect you could get away with straight cuts at the helix angle of the leadscrew.

Andrew

mgnbuk05/06/2018 20:06:59
487 forum posts
10 photos

Technically I think they need to be helical gears, but I expect you could get away with straight cuts at the helix angle of the leadscrew.

I don't think they are that sophisticated, from memory of stripping the TDI down to un-sieze it on the Harrison M330 at work - I think they are straight cut from thin plate. I can drop them off tomorrow to measure up / photograph if that would help ?

Nigel B

damian noble06/06/2018 05:58:33
avatar
144 forum posts
73 photos
Thanks for the replies guys
I've had a look on ebay and the only thing I can get is the whole m300 thread dial indicator but seems expensive for just four small gears.
They are helical albeit very slight.
I might try Colchester just for a laugh see how much they charge for each.I can get the part numbers from the manual.
Cheers
Damian
Hopper06/06/2018 08:30:05
avatar
3289 forum posts
58 photos

Doesn't the Student have a motor reversing switch? So no need for thread chaser dial. Just leave halfnuts engaged, withdraw tool and hit the reverse switch until tool is returned to starting point. It's generally quicker and easier than using the chaser dial.

Failing that, you  coiuld make your own gears out of something like 1.5 or 2mm thick brass plate. Tooth profile does not have to be true form involute etc as no power is being transmitted. Each tooth in effect is a place saver just to hold the dial in the right place. Teeth on the gears could be cut with a simple fly cutter ground to about 30 degrees included angle, or slightly rounded to give a small degree of "involuteness".

Edited By Hopper on 06/06/2018 08:35:04

mgnbuk06/06/2018 08:56:44
487 forum posts
10 photos

They are helical albeit very slight.

06062018929.jpg

Somewhat blurry picture of the M330TDI - pretty certain these are straight cut. The bottom (engaged) gear shows wear due to the thread helix angle. The M330 is close to the M300 - vari-speed headstock rather than step gears - the apron appears to be the same as the M300 at my last employment. The gears are 3.2mm thick.

Nigel B

Alan Johnson 706/06/2018 10:56:14
61 forum posts
13 photos

Buy Ivan Law's book, and cut them yourself. If you have a shaper, well, even a lot more fun!

Thor06/06/2018 13:07:38
1023 forum posts
23 photos

Hi Damian,

As several others have suggested, make your own gears, it isn't that difficult. On my 290 lathe I made an extra gear to cover thread pitches not covered by the original Thread Dial gear. I used Delrin and it has worked well for several years, the width of the Delrin gear wheel is the same as the original supplied with the lathe Thread Dial, the diameter is different of course.

Thor

Bazyle06/06/2018 15:29:07
avatar
4393 forum posts
184 photos

Indicator gears are zero stress and zero precision. You can almost cut them from a piece of plastic food container with pinking shears. Just make a simple flycutter to a suitable shape and cut them from thin brass sheet that way it will never wear the leadscrew so it doesn't matter that it is rough and ready profile.
You will never see them on ebay alone as why would anyone want to strip a whole unit they could get serious money for.
You can also try 3D printing a whole unit. Think there is something the web about doing one for some lathe.

damian noble06/06/2018 15:52:29
avatar
144 forum posts
73 photos
Posted by mgnbuk on 06/06/2018 08:56:44:

They are helical albeit very slight.

06062018929.jpg

Somewhat blurry picture of the M330TDI - pretty certain these are straight cut. The bottom (engaged) gear shows wear due to the thread helix angle. The M330 is close to the M300 - vari-speed headstock rather than step gears - the apron appears to be the same as the M300 at my last employment. The gears are 3.2mm thick.

Nigel B

Thanks all for the replies

Great picture Nigel

I have some 4mm brass sheet so will go with making some. At least the dividing head will get some use on the little mill.

The originals will have been lost due to a careless previous user of the lathe. I'm in the process of a strip down and clean so the lathe is in bits.

I did know it would be a long shot finding them on their own. There are some on ebay but they are odd numbered ones.

Damian.

Jon06/06/2018 20:47:04
953 forum posts
46 photos

This is the Thread Dial Indicator off mine.
1 off 16 tooth slightly helical.
Works for Metric and imperial i change nothing.

damian noble07/06/2018 00:19:47
avatar
144 forum posts
73 photos
Cheers Jon. The imperial dial only has one change gear as far as I'm aware.
Jon07/06/2018 18:54:24
953 forum posts
46 photos

Thats what i have just figured out.

Mines an ex GKN painted horrible green, dont care its a tool. Its an early one 70's lead screw may be imperial never bothered to check since it good for metric and imperial with no faffing about with change wheels, literally dial any pitch in via 4 knobs nothing more to it.
I do have to power out on metric to retain the meshing unlike my old 60's Harrison 140 could disconnect feed and wind back then engage for metric only.

I'll have another check tomorrow got to do a 19TPI my mate cant on a Harrison 11" and asian Colchester copy.

All Topics | Latest Posts

Please login to post a reply.

Magazine Locator

Want the latest issue of Model Engineer or Model Engineers' Workshop? Use our magazine locator links to find your nearest stockist!

Find Model Engineer & Model Engineers' Workshop

Latest Forum Posts
Support Our Partners
Warco
Eccentric July 5 2018
Ausee.com.au
Eccentric Engineering
ChesterUK
TRANSWAVE Converters
Allendale Electronics
Sarik
emcomachinetools
Subscription Offer

Latest "For Sale" Ads
Latest "Wanted" Ads
Get In Touch!

Do you want to contact the Model Engineer and Model Engineers' Workshop team?

You can contact us by phone, mail or email about the magazines including becoming a contributor, submitting reader's letters or making queries about articles. You can also get in touch about this website, advertising or other general issues.

Click THIS LINK for full contact details.

For subscription issues please see THIS LINK.

Digital Back Issues

Social Media online

'Like' us on Facebook
Follow us on Facebook

Follow us on Twitter
 Twitter Logo

Pin us on Pinterest