Member postings for John McNamara

Hi Bruce

If you are looking for small this Australian site has down to 1mm pitch Timing Belts, **LINK**

I have no connection with them just noticed them a while back

Regards
John

Hi JA

Best wishes, A few mates have had it done, all good.

Regards
John

Hi

??
From previous post.
"Leave the 4 jaw in & then you only have to mount the 3 jaw in the 4 jaw without all the bolting up."

If the 3 jaw chuck has a hardened body (And most do) not a good idea at all.
There was an engineering works down the road where this was a work practice until.... Until the three jaw came loose at high speed The lathe was a large Dean Smith and Grace, and the three jaw was no lightweight. It put one person in hospital, he was seriously head injured, as it ran amok bouncing around the workshop before finally coming to rest.

Hardened jaws against a hardened body can easily slip.

Regards
John

Edited By John McNamara on 24/05/2016 15:22:42

I also have a set of Pens, and a couple of sets of beautiful set of cased instruments, also found secondhand shopping. nice to look at and handle. Trouble is CAD has changed the way I work. If the set you are looking at is in good condition buy it as a recognition of the way we used to work.

Rotring pens are great to use when they are working but they were always a fiddle particularly the fine ones, the fine wire cleaner built into them was very fragile and the tended to clog.

These days I prefer the throw away variety, they simply work.
Rotring pens offer much thicker precise lines... Not available as throw away. Felt tips are not precise. Line thickness is no problem with CAD

Regards
John

The saddle resting on the two outer V's is optimal, with any type of slide way "crabbing" is the enemy, the load on the saddle is applied asymmetrically, tending to try to dislodge one corner of the saddle sideways and therefore up the V incline, Having two V ways reduces the chance of this happening. Most tool room quality lathes use this method.

Moglice dislodging ?

Unfortunately for this conversation I did not actually use Moglice I made my own Epoxy based material. It has given no trouble in the past 5 years since I did the rebuild. This is my only lathe and I use it to this day. When I applied it I cleaned, cleaned and re cleaned the 2 V's under the saddle I also used a small 5" disk sander to break the glaze and remove embedded grime. final cleaning was with solvent thinner. The V's were bright and a new paper towel was not marked by rubbing along the V.

Maybe the Moglice that gave trouble was applied in a less than optimal way?

It is clear Turcite or an Epoxy based material are both suitable contenders to do this work. I chose the Epoxy based method because I was able to perform the work myself. I do not own a slide way grinder. I did make a 150 kg grinding Jig but that is another story and the time input was huge, it would not fit on a small lathe.

If I was contracting the work out my main interest would be will the contractor be able to do the work and return the machine brought back to factory spec or better. Being a one off it should be better.

Regards
John

Hi Russ

The cross slide will have to be done first because it generates a line at 90 Degrees to the spindle axis. When setting up the saddle to the bed the cross slide must work perfectly, that defined line is used to set the cross slide to face a work piece flat or a tenth or so dished over 300mm . The cross slide is almost certain to be worn at the point where most average tools hit the average bar turned. Somewhere towards the middle of its travel. Try to keep the original 90 degree geometry, take a little of each side. Remember the apron and lead screw must remain parallel to the bed.

By adjusting the gib's to a good fit in that so called normal average position you are almost certain to find it binds at the extreme in and out position. Any binding indicates wear. I would disassemble clean and reassemble before performing this test in case a bit of swarf is the culprit.

It is important the slide and dovetails are scraped so that the slide describes a perfectly straight line from end to end. Use a known straight edge and a dial indicator mounted on the slide to test for this.

The contractors you are in discussion with have indicated that they will use Turcite and grind it in. I guess the real question is how accurately will they align the saddle? setting it up against the spindle axis. Will they do it to the Lathes original specification?

As an aside the head on my lathe also sits on the v's however the fitter who assembled the lathe when new had done a little scraping to tweak the fit against the v's I found it when I disassembled it. The as ground set up was not quite to spec. One would hope your contractor would do the same.

Dr Schlesingers classic book I believe out of copyright he passed away over 50 years ago should be found here:

**LINK**

About Him and Myford!
http://www.practicalmachinist.com/vb/redirect-to/?redirect=http%3A%2F%2Fallanjbester.co.za%2Fpersonal%2Fmachining%2Fdoc%2FNo%2520Limits_Georg%2520Schlesinger.pdf

I hope you find it useful

Regards
John

Edited By John McNamara on 20/05/2016 13:16:05

Turcite? an alternative is Moglice **LINK**

The turcite I know of is glued on in strips, it then has to be scraped down to fit. Moglice is an Epoxy composite that is spread on then you use the bed as a pattern.

I used this method for my lathe. it has run on Epoxy bedding material since 2010 **LINK**

For one job it would probably be less expensive to buy Moglice.

The tailstock on my lathe was also worn, I was able to grind 2 exact shims to pack the front and rear back into line. the shim was placed under the top section where it meets the base (the joint used to set over the tailstock)

On my lathe the headstock is located by an extension of the actual ways, so there was no alignment problem there, it simply bolted back on..... Ok with a tiny bit of scraping.
That covers aligning the headstock, tailstock and bed.

The saddle is a more interesting project. It must be set in exactly the same position as it was when the lathe was new and not worn, otherwise the driving rack and pinion, leadscrew, and control bar if the lathe has one will be out of line.

The geometry of the cross slide must be set back to tool room specification.

The method I used was to make 4 jacks..... a piece of 12mm plate with a 45 deg V in it and jack screws with lock nuts facing into the V. Each plate was bolted to the saddle using the wiper screw holes. You may have to drill your own if they are not in the right position on your lathe.

Using the jacks I was able to suspend the saddle above the bed adjusting and measuring until it was perfectly positioned in every plane. it was then lifted off and the bearing material was applied to the underside of the saddle.

Before doing this the bed was very carefully masked off exposing only the V ways the ways were given a coat of release applied very carefully..... Epoxy sticks very well.

It was than a simple matter to replace the saddle this forces the epoxy to conform to the bed and once set overnight you are almost done. There will be excess Epoxy to carefully remove. and the top of the V groves filed out carefully so the the saddle only rides on the V's

There is a minimum thickness requirement for epoxy you may have to grind or mill a little off the saddle V's

The process worked really well for me the tired old lathe was transformed.

This is not a process to be undertaken by anyone that does not have the skills to do it. it requires (very) accurate measurement and an understanding of the underlying principals that define a lathe.

Regards
​John

Wood.... Wood!

Not ideal. Easy to do but a lot of cleaning up after"woods".

Newspaper spread out helps keep it off the ways, Never ever cloth, there is too high a risk of it being picked up by the spinning chuck or work. possibly dragging a limb in or whipping you in the face. Newspaper will tear away.

Regards
John

One of the most used tools in my workshop is the 200mm fine wire brush I have fitted to a grinder.
Even a badly rusted cap screw will soon be cleaned, I guess in about 30 seconds to a minute. If you use it lightly it will not remove all the blacking on the screws, if there is any left. Naturally you clean the threads in the correct direction, you do not want to round the crests.

For safety always wear eye protection when using a wire wheel, and use it with care it works quite well on skin... Ouch. I do not use the rest that was fitted to the grinder, it is too easy for a part to get jammed between the rest and the wheel, Or your finger! Not a safe procedure.

Getting the right wheel is important. they are available in steel, brass and plastics of different bristle diameters. The wheels available at the hardware store may be too rough and tend to have a rather open density of wire. Industrial suppliers are the place to go, there are many grades. Mine is fine hardened steel wire, I cant tell you the type as it was purchased many years ago. You supplier should be able to advise you.

Abrasive cleaning is not selective, I would reserve it for non precision parts. using it will round all edges.

Regards
John

Edited By John McNamara on 20/05/2016 01:10:26

Old pre second world war Singer sewing machine heads had v drive pulleys, they were usually driven by round leather belting, this allowed the metal staple used to join them to pass through the V if set correctly. The round belt would slowly form into a rounded top and bottom V. If you can find it the best belting has a little hair on the top surface. It was left there to prove that the belt was cut from the top layer of the hide. A good belt would last for years of daily industrial use.

Regards
John

Hi All

I Found the following search useful.

**LINK**

Gee several oils per movement !

Regards
John

MisTakEs

I am an expert at PHD level.

Hopefully one day I will make less of them.

Regards
John

Is there any possibility of dust Russell?

It is my understanding from reading. I am not a clock maker that escapements can be left dry, this avoids dust getting mixed with the oil. there is also no viscous drag running dry. The loads are so small that the parts polish themselves rather than wear apparently?

Regards
John

Edited By John McNamara on 18/05/2016 07:48:52

Edited By John McNamara on 18/05/2016 07:50:03

Maybe I was a bit brief when I said "Like measuring dovetails", cylinders are often used in measurement. this was just one example,

in a word they are handy.

Regards
John

Like measuring dovetails

**LINK**

Regards
John

Hi Mark

Not sure what sort of plastic it is ? Could you heat a turned blunt spike then press it into the plastic, Maybe the plastic would flow into the tube forming a thicker section that might hold the screw firmer?

This process is used to reinforce holes in steel tube see link below.

**LINK**

Regards
John

Edited By John McNamara on 09/05/2016 12:31:16

Hmm...

The object being measured has an end otherwise the ejector would not work

I think it is for checking wigwams for a gooses bridle.
Or maybe a thingamajiggera

Cheers
John

Edit
The Mercer Indicator is very nice.

Edited By John McNamara on 09/05/2016 12:21:35

Hi Robert

This is how I would do it.

Pre face the workpieces if they are hacksaw cut.

As it is aluminium and fairly easy to turn I would glue the disk to another 10mm smaller diameter disk fitted in the chuck.

There are lots of adhesives Loctite for example, that will release if you heat them.
Jewellers often use shellac

Then:

Drill a 2.5mm hole in the center.
Bore the hole to 3 mm (You will need to make a tiny boring bar from high speed steel).
Face the disk.
If the flywheel is recessed, recess one side.
Turn the edge of the disk to 95mm diameter.
Turn the back 5mm of the edge of the disk, this will assist setting it up to machine the other side later.
If the edges need chamfering do them now.

Then:

Unglue the disk from the mounting disk
Using a 4 jaw chuck remount the disk (protect the turned edge with thick paper)
You can use the two turned edges to set up the piece accurately with a dial indicator.
Face and cut the second recess if needed.

Cheers
John

Hi Rainbows

100000 Newtons to pounds force = 22480 pounds radial

I guess that will do!

**LINK**

Regards
John

Hi Capn

There is mention of how to use the button here....

**LINK**

Regrds
John