Member postings for old mart

When you lift up the Y axis part, press down on the nut in the hole at the same time, it should not be a tight fit.

No, you have lost me there. Perhaps it would have been better to read "a device for cutting very fine pitch screw threads".

Edited By old mart on 20/01/2023 21:37:18

I have replaced the 1/2 hp single phase motor with a 1 hp three phase and VFD on the Tom Senior light vertical which the museum inherited. One reason was that the spindle was converted from MT2 to R8 and a bit more power would be useful. The motor speed control is a bonus, with a 6 pole motor running between 25 and 75 Hz, it runs between 450 and 1350 rpm giving the mill, which also has 4 speeds by belt, a good range. VFD's can be programmed to reverse the motor if required and also the acceleration and deceleration can be programmed. Also, a lot of 3 phase ex industrial manual machinery has come into hobby use and it is often easier and cheaper to dispense with the complicated 3 phase switchgear and run from domestic mains which is usually single phase. Three phase motors run smoother than single phase.

Edited By old mart on 20/01/2023 21:32:14

Edited By old mart on 20/01/2023 21:33:01

To get 100tpi,you only need 20 and 25 tpi threads working against each other.

I think you remove any gibs from the Y axis and lift it up. the nut will remain with the Y leadscrew in the knee. The picture, 19-49-08, with the red ring shows the nut in the hole after the screw and washer have been removed, clean the muck off and you should see the bronze.

Did you notice the R8 head, much more complicated than my R8 mod to the light vertical head, I only have two taper roller bearings.

 As for the scale, the original drawings have been scanned, so they could be any size.

Edited By old mart on 20/01/2023 20:48:17

Difficult to understand, but it looks to me that differential threads are involved to get the super fine pitches.

The manual for several variaitions is on the Denford website, and here is the link to the pdf. The nut for the Y axis is shown on p13. These mills are very easy to strip down.**LINK**

I have pictures in my album of modifications done to the Y axis nut for antibacklash. The igp 2994 shows the hole that the nut sits in, and the nut and the nut and its modifications ars from igp2998, to igp 3013.

Edited By old mart on 20/01/2023 20:35:30

It might be a good time to think of a replacement chuck, small ones are not expensive and someone should be able to advise which would or could fit.

Edited By old mart on 17/01/2023 18:55:00

I pay about £1.50 for fast epoxy at Proper Job, try getting genuine Araldite that cheap.

I found that the standard Araldite, which is the 24 hour paste, is stronger than the fast curing types. Unfortunately it costs about 4 times as much.

I had heard of it being associated with custom made tools of this type, but would have expected it to have turned up in the OED by now, its not a new word.

 Reminds me of that Blackadder episode with Robbie Coltrane.

Edited By old mart on 16/01/2023 19:10:39

It would be best to practice on something soft like aluminium or plastic. Even a small thread like1mm pitch will need to be cut in at least 3 passes. The thread total depth will be 0.5mm from initial contact, and I would go 0.2, 0.15, 0.1 and 0.05 depths getting less as the tool has to cut more each pass. An aluminium thread of 8mm or longer engagement in the flywheel would be more than strong enough to make an extractor without resorting to using steel. And a 12mm thread with a decent bolt in it would finish the extractor, it won't be used very often.

Another thing, if you make the extractor body double ended, if the first end is too tight, remember the depth of the last cut and do the other end deeper by about 0.1mm.

Edited By old mart on 15/01/2023 19:07:31

What a clever design, obviously specially for constant use in turning tapers. Is there a locating pin for zero, as the scale markings would never be better than +- 1/10 degree?

I have some Rabone Chesterman stainless steel rulers which have scales down to 1/100" and the six and twelve inch slim ones could be cut down to make mini rulers. They also have mm, 1/2 mm and fractions down to 1/64". Smaller scales would be very hard to use manually.

Full size wheels often had a "tyre" shrunk on them as the old profile wore down. You could do the same with yours if you are very concerned. As already mentioned, it will not be particularly noticable if practice.

I was very lucky to be of the right age to go on a school outing to the Eastly Locomotive Works near the end of the steam era and saw tyres being shrunk on to locomotive wheels and later turned to the original profile. There was a pacific hanging about 30 feet up in the air when we visited.

My friend has restored an AJW which he dug out of a ditch in much worse condition than that Sunbeam. It was for the joy of the restoration not profit, and it gets ridden regularly every summer.

With a small lathe and difficult material, you should expect to have to hand finish the keys. You only make them once, and your normal work is very different and more suited to your machine.

Don't be afraid to remove the threaded part to offer up to the flywheel. To cut deeper, all you have to do is back off the threading tool, bring it into position halfway along the thread and shut the leadscrew nuts. Turn the chuck by hand to remove the backlash, and bring the tip close to the job. Use the compound to get the cutter aligned with the groove of the thread, using a piece of white paper and a torch to see better. Even a 1mm pitch can be matched closely, and it is just an extractor, not an aircraft part.

All I can think of is that it was made to special order by a tap making company and they used a tap blank which already had the square on the end. We have some strange taps at the museum, usually foundin boxes of tools and cutters donated to us. I keep them hidden out of harms way in case somebody uses one by mistake.