Myford QC Gearbox Project.

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Pete W.:

--- Quote from: Stuart on February 25, 2014, 04:53:12 AM ---Pete

Now you have it sorted do you know that to cut metric threads all you need is a 33t and a 34 t gear to replace the output gear from the banjo if my brain cell is working its a 24 t

these are not to nasa standards but are very very close and cheaper that the metric kit ale you retain most of the fine feeds

Stuart

--- End quote ---

Hi there, Stuart,

Thank you for your post. Yes, I am aware of this and I already have the relevant two gears plus the chart that goes with them, courtesy of John Stevenson via 'the Bay'. Still, your post may draw the attention of other Modders to this facility for cutting threads that are not too long (i.e too many turns).

I have quite a bit of work still to do before I'm in a position to actually use my QC Gear-Box. The first thread that I anticipate cutting is 1/4" BSF. I shall probably rough cut with the QC Gearbox and a single point tool and then finish with a die in the tail-stock die holder.
If you examine my last batch of photos closely, it looks as though the Woodruff key fell out of the lead-screw gear while I was fitting it! :bang: :bang: :bang:
I didn't notice it until I was posting the photos on here! :Doh: :Doh: :Doh: So attending to that is going to be my first task when I get back into the workshop.

:offtopic: Back in the 1970s, I met a gentleman who was a director of the Barking Brass-ware Company (I hope I've remembered the company name correctly). He told me that they were still cutting threads on bathroom taps etc using hand chasers. He gave me to understand that the scrap-rate was negligible.

lordedmond:
I have seen thread chasing done .i think it's a confidence thing just dig it in and follow, they used a tool with a stout handle held under the armpit

It looked hairy but it worked and has been used for donkeys ages

No worries about the gears as you say others may not know, I use JS gear for quickies but break out the proper metric banjo for government jobs,

Btw next project for you would be the Graham Meek clutch, I have one for the big bore Gray did the drawing from dims from my lathe all done via Email , I do not leave it on the lathe all the time those two gears get a bit hard on the ears even though I have poor hearing as there is no way to completely disengage the unit but it does work great

Good work on the RDG effort at Myford bits the old works where only 5mile away

Stuart

krv3000:
hi it all cuming together well :thumbup:

Pete W.:
Hi there, all, and thank you, Bob, for your encouragement.

I've been stalled at a ridiculous stage of this project. Here's an extract of the Illustrated Parts List (aka 'exploded diagram') of the right-hand end of the lead-screw:

(I must apologise for the printing being positioned over some of the detail.)

Item #7 is the drive pin that engages with the lead-screw hand-wheel. (I couldn't find a usable picture of the hand-wheel - imagine that item #5 is its hub. As you can see from the diagram, the drive pin is supposed to be fitted into the cross-hole in the end of the lead-screw, it's a light press fit and has to go in after the collar (item #55) has been fitted and the lead-screw passed through the right-hand bearing (items #60 & #61).

I have two drive pins which have come out of two lead-screws. The problem was I couldn't persuade either of the drive-pins to go into the hole in the lead-screw I've fitted to the lathe. I was reluctant to get heavy with a hammer, either with or without a pin-punch, for fear of bending the lead-screw.

I tried spinning the drive pin in the lathe and gently stoning it but that didn't work. A big part of the difficulty was offering up the pin squarely to the hole. In desperation, part of my fevered brain started to design a screw-jacking device :bang: :bang: :bang: but calm returned.

Eventually, I ran a succession of twist drills through the hole, starting with one that was an easy fit and stopping when I reached one of a few thou less than the measured diameter of the pin. I still had to coax the pin into the hole with light taps of the hammer but it seems to be fitting OK now. (I recently visited a relative who has a Myford Super Seven with QC Gearbox and he said that the drive pin in his machine tends to drop out!) If I'd overshot the mark with the drills, my back-up plan would have been a drop of Loctite!

Having dealt with the drive pin, I fitted the lead-screw hand-wheel.
When I took it off the old lead-screw, there was a 7/16" washer under the nut - the shed gremlins seem to have run off with that!! :ddb: :ddb: :ddb:

The securing nut, item #6, is a 7/16" BSF Simmonds nut. The original had a locking ring of red fibre but age has taken its toll of that and I can tighten or loosen it by hand.
About twelve months ago, I had bought a couple of 7/16" BSF Nyloc nuts but the shed gremlins have run off with those too! :ddb: :ddb: :ddb:
So I adjourned to the 'Bay and ordered a few more, with washers. They're promised for Friday delivery - I bet the original ones will turn up tomorrow (Thursday)! :D :D :D

dsquire:
Pete

Lovely job your doing of presenting the Myford QC Gearbox Project. :thumbup:

I think you might want to have a sharp word with those work shop gremlins before they get totally out of control. :D :D

Cheers :beer:

Don

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