Myford dividing head problem.

Advert

New Replies

Report Bug

Help/FAQs

Myford dividing head problem.

This topic has 7 replies, 4 voices, and was last updated 6 November 2017 at 09:42 by Clive Washington.

Viewing 8 posts - 1 through 8 (of 8 total)

Author

Posts
2 November 2017 at 12:15 #18727
Clive Washington
Participant
@clivewashington54052
Advert

2 November 2017 at 12:15 #324974
Clive Washington
Participant
@clivewashington54052
I've been doing a few jobs with my Myford dividing head and it seems to me that the plunger spring is far too strong for easy repetitive use, so I wanted to replace it with a weaker one. However, on inspection, there doesn't seem to be a simple way of dismantling it – it looks as though the plunger shaft has been riveted over the knob and would need to be filed off or drilled out in order to dismantle the mechanism. Is this correct or have I missed something? Has anyone else tackled this problem? If I do file it off, how much metal will I have to remove before it comes apart? I'd rather not have to make new parts.
2 November 2017 at 14:20 #325004
John Haine
Participant
@johnhaine32865
I remember that! Getting sore hands from manipulating the knurling all the time. A thing of the past now I have converted the DH to electronic, together with having to keep count and decide which plate to use…
2 November 2017 at 19:30 #325037
Robbo
Participant
@robbo
Clive,

Anyone who has dismantled a Boxford gearbox lever will recognise this fixing!

The plunger is a single piece, and has a thin body over which the spring fits, and it is the end of this which you can see on top of the knob. It is threaded in, and the end of the thread is then peened over on the top of the knob. You need to file off enough to get rid of the peening before the plunger will unscrew. You may find that it is possible to screw the plunger a bit further in so that it protrudes a little, then the peening can be filed off without filing the knob

A problem is holding the business end of the plunger, and this can be done in an ER collet chuck, which is what I have used in the past.

Pull the knob up as far as it will go, and it will then rotate a full circle,it is possible to then get a grip on the thicker part of the plunger just above the bit that goes into the holes on the plate, it has to be really tight as the collet is only holding a few mm of the plunger. Then holding the arm and knob the collet chuck can be turned gently to screw/unscrew the plunger.

There is only about 5mm of thread on the end of the plunger.

As usual, once you know the concept this is easier to do than it is to describe.

PS You don't need to file much off, but it is better to get the thread sticking out of the knob and file round it than file the top of the knob.

Edited By Robbo on 02/11/2017 19:35:48
2 November 2017 at 20:04 #325043
Clive Washington
Participant
@clivewashington54052
Thanks for that, I was prepared to file off the peening, but if I didn't know about the screw thread, I think I would have kept on filing! The tip of the plunger is slightly tapered so I suspect it will be a bit tricky to get a good grip on it.

As the plunger doesn't really experience much load, maybe the best way to reassemble would be simply to screw it back with a drop of Loctite?
2 November 2017 at 21:00 #325054
Robbo
Participant
@robbo
I see on re-reading this I have been a bit misleading. If you pull the knob right out then it will rotate completely, but you won't see much of the plunger. For that the knob needs to be in the deep slot.

Loctite seemed OK to me, the only load on the thread is the twisting of the knob to lock it in the high position and then drop it down into a hole when you have finished winding.

Memory let me down there, but not to worry. I went to the Doctor's and he said "Tests are back, no problem, you haven't got dementia, you're just a stupid old sod".

I was able to get a grip on a few mm above the tapered part of the plunger, but a collet chuck was the only thing that I had that would work without marking the plunger, and as I said it had to be done up really tight, a 2 spanner job.

Edited By Robbo on 02/11/2017 21:02:57
3 November 2017 at 11:32 #325184
Howard Lewis
Participant
@howardlewis46836
A friend, who had a HV6 Rotary Table, like mine, made me a sleeve (C section, by turning and then milling a slot) to fit over the handle to hold it back if a lot of handle rotations are required.

Obviously, not if you are counting holes on a Dividing Plate, for small increments, such as gear cutting.

Howard
6 November 2017 at 09:42 #325691
Clive Washington
Participant
@clivewashington54052
OK, job complete, many thanks. It was hard to get the thread to unscrew! My ER collets are still on their way from distant lands and the only thing that would grip the plunger tip was my bench vice, so there was a little bit of cosmetic damage to it. I'll probably make a replacement when I get a spare moment. Much easier to work now with a lighter spring.
Author

Posts