Member postings for John McNamara

Hi All

I Stumbled on this web site
An Australian engineer living in Vietnam.
An unusual way of holding an ER collet.

**LINK**

Video Link
**LINK**

Regards
John

Edited By John McNamara on 19/02/2019 15:02:11

Hi

That is a very interesting lathe, Unusual would be another appropriate word, In particular the way the bed is set up. I am guessing it is pretty accurate too.

I would just wash out the saddle and leave well alone.

Note that standard deep groove ball bearings have clearance They will visibly wiggle, a nice scientific description! don't mistake this for wear. They may still be within spec.

Regards
John

**LINK**

PS "If it aint broke dont fix it"

Hi Mark

Re 9" Hercus lathe.

When I was 18 as Humphrey Bogart said this was "the stuff that dreams were made of".

It has taken a while to find it but here is a link to a scan of the 9 inch Hercus brochure.
24 pages!

This link will take you to a cloud folder you can download the pages from there.

**LINK**

Regards
John

Hi All

Having read up on various epoxy specifications for my mill project i noticed that some mentioned a minimum cure temperature, in some cases quite high, the cross-linking process does not properly take place at too lower a temperature, resulting in less than optimal mechanical strength.

Making your own mix of iron powder and epoxy is feasible. 0.5 kg of iron powder will go a very long way.
I experimented with 24 hour Araldite and Iron powder and it was a success. The link below is In Australia, I do not know if they export? (No connection apart from being a customer)
**LINK**

Regards
John

Hi

A very handy site that covers Machine tapers is this one.

If you have an old taper you are trying to identify chances are it will be listed.

**LINK**

Regards
John

Hi All

Assembly of some of the laser cut parts, also a bit of machining.

The two rollers support the swarf curtain for the Y axis. Also note the 30 x 30 x 3 mm Aluminium angles bolted to the cast in place inserts in the base. These together with the top of the Linear ways form the support for this curtain. See the start of this thread for a 3D view.

The rollers are 40mm light steel tube with machined ends and 32 x 12 x 10 mm sealed ball bearings.

The laser cut 5mm mild steel brackets are bolted to cast in position inserts, no welding.

Laser cut control system 2.5mm mild steel box bolted to existing cast in position inserts.

Laser cut control system 2.5mm mild steel box bolted to existing cast in position inserts. (Not finished)
Note how it wraps around the cross-member casting.

More to come.........

Regards
John

H all

Re the jack screws. These are only used to position and align the cross-member while it is being set up.
Once this stage is complete the small gap left will be filled with metal filled epoxy bearing material bonding the components together.

I will use my own formula for the metal filled epoxy grout.
link to power point file: **LINK**

Stefan Gotteswinter did this in an excellent video on you tube showing the method he used on his milling machine to improve its accuracy.
**LINK**

This machine will be set up in the same way.

I have seen a number of posts on the method, it is used by many commercial machine builders to assemble components.

Regards
John

Hi All

The base casting has been quite a project it is heavy. over 200 KG

The underside of the casting carefully leveled before stripping the mold sides, note the inserts; 2 x 6 counter-bored holes for attaching the columns and the 4 M20 tapped holes for the adjustable feet. the rectangular hole in the center provides ventilation for the y axis drive motor.

Here it is finally undercoated and on the little engine crane I use to manhandle heavy objects.
I needed the crane to manipulate it while I ground all the sharp edges, apply filler where needed and finally give it a coat of dark grey undercoat. There is no shortage of M12 mounting points for the eye bolts.

And now comes the main event!

At last the 4 main castings have been test assembled. And I could not be more pleased, As you can see below the face of the cross-member casting that carries the X axis is square to the column mounting faces, without adjustment it was within about 1.5mm certainly less than 2mm. Using the alignment jacks it was simple to set it dead true against the Moore and Wright 600mm test square. This was only a rough test I will need a straight edge to extend the square. the columns are not bolted down they are just sitting there by their own weight. positioned by the 12x200mm threaded rods without nuts. There is no risk of falling the cross-member is bolted. Had I not used laser cut molds I don,t think I could have achieved the level of accuracy obtained.

The six alignment jacks are M10 x 30 Hex grub screws not seen but marked by zinc bolts inserted in the M10 threaded holes 2 above the columns one out of frame and 3 on the face and one marked by an Allen key.

Also I set up a linear rail on the right it is not bolted those holes have not yet been drilled and tapped, As you can see the cams securely hold it in position, once the machine is properly assembled and aligned the rails will be attached.


The Y Axis drive motor is fitted within the base. The motor plate is removable after removing the access panels. Both panels are 5mm mild steel.they also carry the Y axis limit switches and the Y axis ball screw bearing blocks. These panels were cast in position when the mold was poured with the CSK screws in position holding the to be cast in inserts. This guaranteed perfect alignment between the panel and the base, there is no movement possible when it is tightened down. This is important as the ball screw bearings have to be accurately located.

The X axis Drive is fitted behind the cross-member and through the column casting. Note the removable 5mm mild steel motor mounting plate. The M12 long nuts holding the cross-member are for convenience and will be replaced with nuts that fit within the counter-bore's.

The next step is to bolt the columns in position and prepare to attach the rails. Also there are many already made laser cut accessories paint and attach.

Regards
John

An easy way to resize pictures is to use screen grabbing software, Just open your digital camera image on the screen, select the area you want to post and press capture. then save and rename the captured part of the image as a JPG. It will be a fraction of the size of the original. It only takes a few seconds to do.

**LINK**

Regards
John

All my good quality old screwdrivers are intact. The ones that twist up like #8 fencing wire "Asianeasium" (my word) can go to the scrappy. Together with the fasteners with their smeared heads and other plasticine hardened steel gismos that infest society.

BTW I am enjoying the grumpy stage of life!

Regards
John

Hmm

Windows 7, Chrome, I7 PC. The spelling checker stopped working a while back.
Not that flash really for MTM. They really should do something.

Regards
John

Car headlinings are another victim of the foam gremlin, the foam backing fails and the lining falls down, two have done to me.... not easy to fix and expensive, you have to take the windscreen out for some in order to get the headliner out.

Hi Marcus

Drying
I should of mentioned I spread the sand out thinly about 20mm thick on a sheet of thick black building plastic in the sun to dry it out. I raked it with a plastic leaf rack a few times over a couple of hours to dry it. I did the same for the aggregate. once it was dry it is easy to lift the corners of the plastic towards the center creating an easy pile to scoop up. Maybe not kiln dry but dry enough.

Screeding epoxy is not fun it sticks to everything and you have to remove every drip before the epoxy sets
The mix is rather dry compared to concrete, I have not been able to get a good finish unless i make the last thin coat wetter and sand only. I know a couple of contractors that do pebble mix over concrete, they get a good flat finish using carefully graded pebble sand and a wet mix. Body filler is my best solution so far. An extra step but a nice result.

Regards
John

Hi Vic

Straight from the mold there are there are dead sharp edges and some small holes, the mix is stiff, also other blemishes caused by the self adhesive mold covering "Contact" I use as release. These are dealt with with car body filler, "Bog" in Australia , "Bondo" in the US I am not sure in the UK. A quick coat and then sanding with a half sheet sander for the flat work. I also sand all edges to a small radius. The grey colour is just an etch primer coat.

If you study the images you will also see that the mating edges of all the castings are 2.5mm mild steel sheet placed within the mold before casting. Also the motor mounts and mounting points for ball screws are all cast in 5mm steel plate. Removable 5mm steel panels are also cast in position for a good fit, I wrap them in self adhesive plastic, fit the mounting screws with inserts and screw them into the mold. when the casting is set they can be unscrewed (the inserts are now cast in) and the protective plastic removed. The motor mounting point on the column is done this way as is the motor covering plate and ball screw bearing mounting plate that forms the U channel in the centre of the base casting. This will be more obvious when the casting is turned over. remember it is currently upside down.

The sand used was washed silica as used by the building trade. one part sand to 3 parts granite aggregate with a maximum screen of 8mm. and a minimum of dust. These materials are both easy to obtain.

As can be seen there is a lot of 12mm, 8mm, and 6mm threaded rod used easy to obtain and low cost. It would be possible to simply throw in concrete reinforcement bar. This I did not think was a good idea at all. Firstly it would not allow precision placement within the mold. I wanted to balance all the forces, any temperature effects will be balanced across the section. Secondly the mold itself is partly supported while pouring by the reinforcement.

When I did research on Mineral casting I found hundreds of academic papers on the subject and hundreds of thousands (yes) of forum postings on the subject. Some say no reinforcement! others use it. Some argue about the mix and pouring method with great passion. Not many of them actually build anything.....

No doubt this machine could be improved by using a high tech approach, by how much? probably not as much as you would think (The ultimate strength is governed by the epoxy itself), that's why we make thick sections. Even at this early stage it has taught me a lot and I know it will continue to do so.

I have tried to avoid any hard to obtain materials, and really hope a few people try this methodology for their own projects.

Regards
John

Hi All

The base casting is poured!

The components.... Mold, turned parts and laser cut parts to be cast in.
Note the bearing support rails and column support pads on the main base plate. these sit directly on the surface plate and are aligned by holes in plate.

Mold ready for casting.

Electric and control supply ducts fitted.
Also note M20 long nuts with 30mm collar from the local hardware (Bunnings) V grooved in the lathe for extra grip. (attached to the bottom bracingf plates)
The 2.5mm laser cut steel box will contain the Y axis drive motor. Rough ground with an angle grinder for good adhesion.

Foot mount (ignore small hole in collar) the washer was bored and fitted to a step in the collar.

Jacks that press motor void box down made from scrap fastenings, the nuts were grooved 12mm for location. limited travel was needed, they worked well. Small long nuts are M6 from The hardware store, gooved in the lathe The white material is painters gap filler to stop epoxy entering the hole, easy to remove after.

Wooden strip: A 10mm sq timber strip was glued to the back of the bearing support rails. This is to allow through drilling for the tapped holes that will later be required to mount the rails. See previous discussion of this process.
I also mounted a jack at the end of each bearing support rail to assure it did not lift during the pour, It will be cast in and lost.

The casting was done in layers, about 25mm at a time. tamping between each layer, the process took about 3.5 hours, my wife assisted throughout tamping I mixed in batches of half a bucket and tamped at the end, without assistance I would not have been able to place the epoxy in time, after a short pause to allow the casting to partly set the brace plates were removed, in case a side panel decided to come away they were tightened against the inner rails and the last layer was placed, this layer was done with a wet mix, 20% epoxy. After placing the mix was carefully screeded level. as can be seen the surface is flat but not without imperfections, this will be attended to when the casting is removed from the mold.

Mixing was slow, a cement mixer would have sped this up but the clean up would be heavy going, and you would need more tampers! unlike portland cement when hitting hardened epoxy with a hammer the surface is marked but it hangs on.

For mixing I used super cheap buckets, doubled up, 4 were cracked by the stress, also an electric drill on the slow setting and a hardware store cement mixing screw. The drill struggled. I mixed 5 litres at a time by volume about half a bucket.

I am still amazed how accurate the finished molds are they fit together perfectly.
The next step is to remove from the mold, clean up and undercoat the casting.

I cant wait to assemble the base, columns and cross member, then take some measurements.

Regards
John

Edited By John McNamara on 28/01/2019 12:25:14

Hi John Pace.

GMTA I made the same toolbit using the carbide shank from a PCB drill, PCB drills are so tiny to hold up they are made from very fine grain carbide. Tough too.

I milled a piece of key steel of the correct size and silver soldered in place.

Been using it for a couple of years. The ten degree angle you normally use for the Diamond tool can be reduced to around 5 deg by angling the template. More robust for heavier work. However it will work fine as standard.

Regards
John

A backstop in the spindle is very useful to turn parts to dead length, easy to make at minimal cost. Mine is just a piece of threaded rod with its end bored and carefully faced, the bored hole means that any pip or slight bulge in the part face will not change the length. Just remember its there if you are working with a small diameter part that would fall into the hole.

On bigger lathes you may need a version for long and a version for short parts to avoid too much stick out of the threaded rod from the headstock, not safe and it can vibrate.

You will need to make some sort of split expanding collet to hold the stop securely in the spindle bore not hard to make it does not have to be super accurate. keep it short so that you have more capacity to hold longer parts.

Depending on the length of the spindle bore you may need to support the free end of the threaded rod in the bore, On my setup I did and made one from a piece of nylon cutting board a running not tight fit in the bore mounted between nuts and washers on the threaded rod, it does not rattle and keeps the rod centered.

Regards
John

Edited By John McNamara on 23/01/2019 01:20:48

Hi
I have a precision box level bought second hand nice quality Wyler Swiss. an Asian 300mm precision 10 second level purchased new and a Starrett "Machinists level" also purchased second hand.

If you went shopping and paid full price a fair amount of cash would be needed, but that's not how I shop, like most of the tools in the workshop the items turned up unexpectedly. Its like fishing, The main thing is to not let them get away. Maybe you won't use the item straight away but sooner or later you will.

Other uses are setting your milling machine table perfectly flat, makes setting and checking angles easier.
Checking a flat surface for deviation from a true plane, the method is shown in most metrology books.

If your lathe or other machine machine is in good condition it should be set up with a precision level. that is what its manufacturer did when it was tested, Setting a good lathe up out of square will encourage out of square wear.

Rowleys method is for older worn machines, you are trying to correct errors by twisting the bed of your lathe by trial and error. Before I did this I would want to know how the machine performs when correctly leveled. On nearly all lathes the top of the shears or the top of the V's are used by the manufacturer as a datum. You can normally find unworn sections at each end of the bed. use these points to check that there is no twist in your bed.

I find the box level is my least used tool the short base length often requires a precision ground bar to extend the length. Its big advantage is that you can align vertically I don't often need that and you can always use a precision square with a plain level.

The Starrett USA with its black crackle finish and elegant chrome bubble housing is really nice to handle, It is less sensitive and is very useful for quickly rough leveling 1 division on the vial = .005" over 12" Still far better than any carpenters level.

Starrett also make beautiful precision levels with 10 second accuracy or even less! So far one of these fish has not come my way.

The Asian "Measuremax" brand level is 300mm long is very sensitive 1 division on the vial = .02mm per metre,

There is not much point using a level like this on a wooden floor they are flexible even if you can't feel or see it, the bubble can go off scale if you take a step. However if you have a concrete floor this is the preferred tool for setting up a machine.

Enjoy your fishing

Regards
John

Edited By John McNamara on 23/01/2019 00:51:01

I also have two of them

Great tool easy to sharpen

Regards
John

Dressmakers pins come on two forms hard steel and soft plated brass, Newey hard steel "Dorcas" pins are good quality, used by the sewing trade. I guess these are what you want if you use pins. They look almost the same.