Damaged Back Gear on Malcar 41/2″ Lathe

This topic has 10 replies, 9 voices, and was last updated 18 November 2017 at 00:03 by duncan webster 1.

Viewing 11 posts - 1 through 11 (of 11 total)

Author

Posts
16 November 2017 at 14:10 #327470
AndyC
Participant
@andyc74769
Good afternoon all,

I have a MALCAR 4 1/2" Lathe that I inherited from my Grandfather, it was built by the Wragg Brothers circa 1954. I have unfortunately damaged the driven backgear on the main spindle. Does anyone have knowledge of this lathe, an idea of where I may be able to get a replacement gear or possibly have a lathe for parts.

Many thanks in anticipation

Andy
Advert

16 November 2017 at 14:10 #33101
AndyC
Participant
@andyc74769
16 November 2017 at 14:54 #327475
Brian Wood
Participant
@brianwood45127
Hello Andy,

I can't be of direct help with spares but it is possible to braze in steel segments and form replacement teeth in them as a means of salvage. The gear has to be free of the lathe in that case of course.

An alternative method is to drill into the broken teeth and insert silver steel pegs to reshape afterwards as teeth. They don't need hardening in case you are wondering. That method can be used for a fix where stripping down is not convenient or best avoided

I have used both methods with success.

Regards Brian
16 November 2017 at 15:01 #327476
Ady1
Participant
@ady1
16 November 2017 at 15:17 #327479
not done it yet
Participant
@notdoneityet
I have a gear with a row of grubscrews shaped to the tooth profile. I would prefer to insert grub screws, shape to a bit less than the tooth profile, then fill with braze and recut the teeth.
17 November 2017 at 09:16 #327598
Brian Wood
Participant
@brianwood45127
Hello again Andy,

Thinking a little more about finding a gear for your lathe, be careful if you approach people like HPC in Chesterfield. to supply a new one

New gears these days by HPC and others will almost certainly be made to the modern 20 degree pressure angle whereas your damaged gear is almost certainly made to the earlier 14.5 degree angle and while they will mesh, it will not be a happy mix. Whoever you approach would need to be made aware of that and will charge accordingly if they are prepared to make a 'special'

There are some on this forum who could supply a custom made copy, myself included, if all else fails.

Regards Brian
17 November 2017 at 11:05 #327622
larry Phelan
Participant
@larryphelan54019
I broke the back gear on my Craftsman lathe some years ago,while trying to remove the chuck [never repeated !].

I had to buy a replacement,kept the damaged one with the intention of having it repaired sometime.

I would do so now if I could find it [It was put away "safe" ]

I thought it would have to be welded with cast iron rods,never thought about brazing.

Now,where did I put it???
17 November 2017 at 20:28 #327701
Neil Wyatt
Moderator
@neilwyatt
Some good advice on brazing CI in Keith Hales book on silver solderings. Without giving away everything he suggests burning off surface carbon before fluxing.
17 November 2017 at 22:37 #327726
Hopper
Participant
@hopper
It might be worth measuring up the gear and determining the DP and number of teeth. It may be possible to find a more readily available gear off a Myford etc etc that can be machined to fit by boring out the centre etc.
17 November 2017 at 23:17 #327734
peak4
Participant
@peak4
Posted by Brian Wood on 17/11/2017 09:16:46:

Hello again Andy,

Thinking a little more about finding a gear for your lathe, be careful if you approach people like HPC in Chesterfield. to supply a new one

New gears these days by HPC and others will almost certainly be made to the modern 20 degree pressure angle whereas your damaged gear is almost certainly made to the earlier 14.5 degree angle and while they will mesh, it will not be a happy mix.

Regards Brian

No experience of these myself, but Tony has a comment on his web site requesting any owners get in touch with him, presumably so he can add more machine details to his database.

Regarding the pressure angles etc. assuming the gears are say 20dp, they always run as a pair on a backgear, so if one were to replace both gears as a pair pair from HPC, then the pressure angle wouldn't be an issue.

If they have internal splines, then bore out the new gears to a larger ID, and turn the teeth off the old ones. Pin and Loctite the two parts together and re-fit.

Bill
18 November 2017 at 00:03 #327736
duncan webster 1
Participant
@duncanwebster1
I found that getting bespoke gears cut by a chap in Manchester was surprisingly cheap. Unfortunately I can't remember his name, but yellow pages might find one local to you. Make your own blank and tell them it's a banker job (ie no hurry) and no QA required

Edited By duncan webster on 18/11/2017 00:04:03
Author

Posts