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Bridgeport mill dual dial help needed please

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Colin Seggie17/10/2013 21:40:26
25 forum posts

Hi All,

I have a Bridgeport R2E3 CNC mill, I realise that this is the Manual machine topic please bare with me all will become clear.

I am having a devil of a time getting any information on how the Dual dial that is used on the Knee works. What I can't figure out is how the English 100 thou ring engages with the aluminium disc that is pinched and held in place by the locking nut.

They say that a Picture is worth a 1000 words. I don't know how many words a rambling video is worth but this might make what I am asking clearer

Now the reason for asking in the Manual machine section is I have recently seen these dials on a manual machine, it was on a steam train shed tour in Aviemore and they were covered in oil, grease and soot so I could not see how they worked and the machinist was not in that day for me to ask.....(so close but yet so far) Also someone on another forum said he had the same on his manual mill years ago but that that machine was long gone.

I am guessing that there will be more owners of manual machines so that starts to tip the odds in my favour. It seems that these were only on UK machines and not used in the US.

Any help any one can offer is appreciated


Edited By Colin Seggie on 17/10/2013 21:45:26

MadMike17/10/2013 23:32:33
233 forum posts
4 photos

Colin have you spoken to Hardinge in Leicester? Tel: 0116 201 3000.

They are Bridgeport manufacturers/suppliers including spares as I understand. HTH.

KWIL18/10/2013 10:44:32
3554 forum posts
70 photos

Not having used one of these types I would expect, that if the 0s are set together at the start, when 1 rev of the handle is completed the Imperial dial would read 100 thou and the Metric dial would read the metric equivalent. Set a dial guage on the Quill and check the table movement? In Imperial and Metric.

jonathan heppel18/10/2013 14:15:06
99 forum posts

Dual dials are used exactly like single ones. You release the lock, then rotate to zero. You never seperate them to set both zeros together because you're using one or the other. Yours should be eg circlipped together. The master rotates with the screw and the slave consists of dial, gear and stator. It looks like your stator shoud register on the protruding fixing screw as in your clip. If that knurled piece doesn't have a hole to register it is either not original or there are more pieces missing. It seems you are missing your fiiducial also, which is probably of the window type.

jonathan heppel18/10/2013 14:33:42
99 forum posts

Sorry I've seen the vid again and it looks like the knurled item should be a press/ glued fit to the dial, so forget some of my previous rubbish. Does that make sense? You still need a stator by the way, as a reference

jonathan heppel18/10/2013 15:10:10
99 forum posts

I wish you could delete posts on this site. I think I've been talking out of my backside again. Sorry, my machines don't have dual dials so I've been trying to visualise it. So here goes. I think the master and the gear are locked together, the gear drives the slave, so no stator. I think also that your misconception about zeroing the two together was making you think along the wrong lines, so the knurled thing and the dial being one piece wasn't evident. Hope this post's ok

Russ B18/10/2013 18:24:49
615 forum posts
26 photos

the inner ring, and outer imperial ring you removed at 3:53 should be 1 piece IMO which would transfer drive through the planetary gear and to the rear metric ring which is essentially what your doing by hand.

at 0:55 you say "pull that back" - you shouldn't be able to just pull that off - can you imagine how many would go missing over the years!

let us know how you get on, I have a very similar system on my 1970 A&S Bridgeport Series 1, but the gear between my 2 rings is about Ø10 diameter and nylon (rubbish) one is stripped of its threads - no surprise but I'm heading towards metric ball screws as a cheap fix to eliminate multiple issues.

Colin Seggie18/10/2013 19:41:44
25 forum posts

Mike I had not thought to as the part is not listed in the manuals

kwil- that is exactly how it works provided the thou ring is locked to the aluminuim disc but currently the disc just spins inside the thou ring. There needs to be some sort of friction fit between the aluminum disc and the thou ring this would then drive the smaller metric wheel. however, this cannot be a solid coupling as you would need to decouple the metric and English to set both to zero or for that matter to set the metric to zero. The only way I can see that happening is by siding the thou ring out away from the metric and disengage the planetry gears. Then to re engage you would slide the thou ring back in.


I understand where you are going with this but if the thou ring and aluminuim disc were fused then you would need to almost remove the locking nut just to get the thou ring teeth clear of the metric teeth. So that does not seem right. The missing fiducial was removed to gain a better view of the mechanism.

Thanks for your replies.




Edited By Colin Seggie on 18/10/2013 19:45:52

jonathan heppel18/10/2013 20:26:41
99 forum posts

I think you're still under the misapprehension that you need to decouple the imperial and metric dials. You don't.

Think of the two as an assembly, which rotates as one unit, setting the zero of either one as required. You never need to zero them both at the same time. As I said, just treat the two as a single dial.

Steamer191518/10/2013 21:33:49
168 forum posts
42 photos

Hello Colin, I have had a look at the dual dial on my Bridgeport and it is the same as the model described by Russell. So I don't think I can help you with any pictures. I have had another look at the video and agree with Jonathan that the disc should be pressed or glued to the dial. I also agree with him with regard to setting both dials to zero. There is simply no point in doing this - you either work in Imperial or Metric. The zeros will move away from each other as soon as the table is lifted or lowered and you will only need to concentrate on one. Therefore I'm thinking that if you fastened the dial to the disc with glue (or knurl it up further and press fit) then the two dials will be able to be driven at the same time. To set the zero point, one would then release the blacked knurled ring and turn the dials until the desired zero (be it Imperial or metric) is in line with the fiducial line and lock up the blacked knurled ring. I apologise if I have missed something obvious here, but this is how I see it.

Best regards,


Colin Seggie18/10/2013 21:49:22
25 forum posts

That does make complete sense now that I have had time to digest it I suppose where I went wrong was supposing you would use both and in truth you would only one or 'tother.

The knurling also makes sense as someone has knurled it exactly for the reason Steve describes.


Steamer191518/10/2013 22:02:28
168 forum posts
42 photos

Hello Colin, I sent you a PM earlier today. By the way, the video was an excellent idea. As you quite rightly point out, a picture is worth...

Regards, Steve.

Edited By Steamer1915 on 18/10/2013 22:10:10

Colin Seggie19/10/2013 00:28:12
25 forum posts

Steve just replied to your pm.


Colin Seggie19/10/2013 00:28:12
25 forum posts

Steve just replied to your pm.


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