DIY Epoxy Frame based CNC MILL

[John McNamaraParticipant @johnmcnamara74883]

Hi all

I have cleaned up the casting, rounding edges and filling blemishes with body filler, there were more blemishes than I would have liked, the part has been given a quick undercoat, once the whole machine is complete it will be detailed and properly painted. The part is very massive too heavy for me to lift. Tapping it with a hammer yields a dull click, even on the metal parts. due to the damping properties of mineral cast epoxy.

The next step of this project is possibly the most important. the accuracy of the machine depends on this stage being a success. The accuracy depends on the rail mounting points being both straight to fine limits and co planar. As the XY and Z axis are completed they must also be correctly located in relationship to each other. At this point we are dealing with the X crossmember axis only.

As stated earlier in this forum thread a surface plate was used as used to align the steel rail supports. the surface plate partly formed the bottom of the mold. there were holes in the mold and the steel rail support bars projected trough these holes in direct contact with the surface plate.

To test the accuracy of the rail supports the part was placed on shop made jacks. They bear against a cast in steel face not seen, the columns will mate against that face.

The part was aligned to the surface plate to within .0001" using a dial indicator, one div = .0005", mounted on a very rigid Mercer base. Once set up measurements were repeatable to within .0001" or better. The one knob type indicator mag bases being sold widely are simply not up to it.

The rail support bars 70 x 16mm in cross section were ground and hand lap/ground on one side prior to casting, this was not a complete success, the bars were too flexible and I found it quite difficult to get repeatable markings from he bluing. as the results show below there was some error after casting. the upper rail in the picture with two rows of tape had a maximum error of .0008" bowing op in the middle the second row of tape shows the error reduced by lapping to .0004" not a huge job a bit over an hour so far, there was not a lot of metal to remove. More to do, I want it as close as I can get it within the limits of my tools.

The other rail has an error of .0018" almost two thou, mainly caused by a dip at one end
It will take a little longer to adjust.

Simple steel laps made from 25mm x 25mm mild steel. The abrasive is 40 micron mylar on the longer lap 120 grit aluminium oxide on the shorter lap for roughing. not glued on just held with fastenings at the ends. Every workshop should have these, mine never leave the bench

When lapping I sometimes make a small light scribe line to help me gauge progress between indicator checks that take time due to cleaning, not too heavy on the scriber ! see below.

The surface plate It must be kept perfectly clean and free of grinding particles, you cant just drag the indicator around.

The surface plate itself may not be perfect I purchased it from a toolmaker he said it was grade A. as a double check I am also checking the flatness with a precision straight edge, a recent find brand new still in the wax paper. note the date! Both edges give the same readings indicating it has not moved in 73 years.

I must admit I am excited by these results. It is clear that rethink of the rail mounting support design is in order, I would like to improve the preparation prior to molding. They will have to be stiffer and my lapping skills will have to get better.

On the other hand the existing method has worked very w

[John McNamaraParticipant @johnmcnamara74883]

Hi All I was asked these questions at another place.

In answer to your questions A and B.

A. “To get ground stock (can be bought ground, but suspect $$$), predrill (most) holes and cast against surface plate as you have done”

I considered precision ground stock and phoned around to locate a source, it was available at a cost, quite a lot actually; however the supplier would not guarantee flatness on longer lengths. They would provide a tolerance for constant thickness but not flatness, however for this project only one side has to be flat the other side is buried in the casting.

Laser cutting precision ground stock which is normally a water or oil hardening carbon steel is likely to make any hole or laser cut edge very hard. Also my laser cutter charges extra for precise positioning small pieces of material, they prefer to work with large plates. This hardening also occurs to a small extent with mild steel, making it hard going for high speed steel tools however I did not have a problem with HSS on the steel supplied by the laser cutter.

If I was able to locate precision ground stock with a guaranteed flatness it would have to be machined to size and the 16mm holes for the cam pins would have to be drilled. These holes do not have to be located to high accuracy so marking out and centre punching in the normal way would be fine. The cams will compensate for any small errors.

The 16mm thick standard mild steel plate supplied by the laser cutter has a reasonable surface finish free of the normal flaky scale you get on black bar stock, there is a black oxide coating and some mill marks. After cutting it is not flat there was heat distortion, bowing of the 16mm axis in particular. I mechanically straightened the pieces and then sent them to a firm with a surface grinder. This was not a success as they did not completely flatten then pieces. I suspect their operator was not up to the job. The big enemy is the magnetic chuck. Grinding long pieces requires packing the work so the chuck does not pull any bowing down before grinding a side then, then turning it over and repeating the process for the other side. This process may have to be repeated several times until any stresses are relieved and the piece will lay flat on the surface table. Even better would be to have the part stress relieved professionally another cost.

In the end I hand lapped the errors left by the surface grinder. As the post above shows there were some residual errors.
I have been working on them with the lap and now the maximum error is .001” over 800mm testing the part on the surface plate with an indicator. I am confident I can get that down to a tenth or so, however just turning the part 90 degrees would probably change that, gravity is a universal force. I guess I could set the part up on its airy point’s that would possibly reduce the measurement error however temperature is also a variable. My workshop has a skylight. We happened to have a hot day yesterday a high of 33 today the high was 20. As expected my error measurements changed with the sun shining on the part; the top face was heated and the face bowed up. Digging the depths of high accuracy is an interesting challenge.

Question B. “Use mild steel bar stock, cast in standard mold, not requiring surface plate, and pay someone with a big cnc mill to quickly machine the steel and drill the holes?”

That will work no problem, apart from finding a contractor that has a CNC machine and equipment that can handle large heavy parts and cost.

It was tempting me to take that option, were it not for the desire to to find out what is possible using a surface plate, small lathe and basic tools. The laser cut mould is optional it could be made of MDF for one time use. The machine does use laser cut parts, they could also be made by hand a large time cost. If I manage to make a workable machine and demonstrate a method that worked I hope others will maybe create their own designs and contribute improvements to the methods I have used for this machine.

Edited By John McNamara on 13/12/2018 14:32:21

[larry phelan 1Participant @larryphelan1]

As you said John, it is a long Post ! I,m afraid you lost me a long way back !

To put it mildly,this is WAY ABOVE my pay grade ! Never heard of machine bases being made like this,but then,I still have a lot to learn.

Funny that you mention about threaded rod being cheap over your way,I bought some here recently and I dont know how they can produce it for the price.. It,s one of the most useful things I buy,[I use it for everything ],and still dirt cheap.

[Marcus BowmanParticipant @marcusbowman28936]

All the same, this is fascinating stuff, and just shows what can be done with oodles of skill and good planning. I look forward to the next instalment.

As for threaded rod; yes; I agree about the price. However; although I buy the occasional length in B&Q, I have a friend who uses it in quantity for a commercial product. Think of the cheapest price you have ever seen, then divide by 3. That's what he pays. It beggars belief that at that price it can still be manufactured at a profit.

Marcus

[John McNamaraParticipant @johnmcnamara74883]

Hi Larry and Marcus

Thanks for the words of support. Glad to see the threaded rod is low cost for you too. I am not sure the galvanized type would stand up well in severe conditions it is very easy to remove the coating with a wire wheel. I suspect it is applied by a process other than hot dipping. for this project it does not matter, raw steel would have been fine, I just used what was in stock from the local Bunnings store All i want is "reo" with threaded ends for fittings.

Hi All

This weekend I continued the lapping of the rail mounts, its been slow going to get them down to about +- 0.0001" one division on the indicator is .0005" I Interpolated between the divisions, however this overstates the overall accuracy obtained. Temperature and measurement errors have an effect on the results as well. However I am very pleased with the results so far.

I ground the 25 x 25mm mild steel bar face flat for this stage it was not perfect and was affecting the results.
As shown below I used various grades of paper from very rough 60 grit for ripping down 120 grit aluminium oxide finishing off with 40 micron Mylar backed strip. I found the Aluminium oxide paper to be better than emery. As you can see by the number of used strips the paper looses its sharpness and looses cutting power on the large lap fresh paper cuts fast, it will be fine for other work

I will stop the lapping process lapping here until the linear rails arrive. it will be interesting to see how accurate they are when attached and aligned by the cams. Any further adjustments will be made then.

It is time to start the two column castings.

[John McNamaraParticipant @johnmcnamara74883]

Hi All

The workshop has been a little quiet over Christmas, cant wait to get back to working on the project.

I posted a note on limit switches here: **LINK**

I think I will stick to the plan at this stage however the ability to home the machine to within a few microns is a possible upgrade.

Regards
John

Edited By John McNamara on 31/12/2018 01:16:30

[John McNamaraParticipant @johnmcnamara74883]

Hi All

The first Gantry column has been cast and preparation for undercoating started.
The other column is next. The same mold will be used, By turning the base plate upside down and rotating all the mold side plates 180 deg you get a mirror image of the first mold. A bit like making a pair of shoes. The left column does not have to provide for a motor so those parts will not be used.

The steel molds are amazing, every part just fits together, there is no draft. I did not use any mold release. The self adhesive plastic sheeting works really well, a light tap and the mold parts just fall apart. there is a bit of mess I did not protect every face. A quick clean on a wire wheel and the mess is gone.

I have been working on the Epoxy / crushed granite mix mixing about 5 litres of material at a time then placing it in layers, Due to the complexity of the molds and the many inserted steel components they contain I think I will have to increase the percentage of epoxy above 15% to get a wetter more flowing mix. More experimentation is needed. Less epoxy is better (stiffer).The next cast will be the left column.

Mold prepared inserts all attached.

Mold filled with epoxy/granite, the top layer is 5mm of epoxy/sand for a smoother finish.

Body filler applied and sanded in preparation for painting

Motor pocket metal form work partially removed. See removable cast in position motor plate at bottom of pocket.The form work was wrapped in duct tape prior to casting this provides clearance making it easy to remove.The M8 threaded rods attach the mold base and locate the motor plate and form work in exact position in the mold.

Removable motor plate cast in position. It is wrapped in adhesive plastic film, this provides clearance for removal and epoxy won't stick to it.

View showing the cast in position mild steel 10mm mild steel shoe and 2.5mm mounting faces for the gantry attached to the column

[Michael GilliganParticipant @michaelgilligan61133]

Great progress, John

… a really fascinating build.

MichaelG.

[Marcus BowmanParticipant @marcusbowman28936]

John,

Looking at the first photo in your post dated

06/01/2019 08:20:45

I would suggest that when you have removed the second side, you clean the mould carefully then pour clear resin into it; polish the finished article, and mount it for display in your workshop. 'Tis a thing of beauty.

Marcus

[SteveIParticipant @stevei]

John,

Thanks for the updates, a most interesting build.

I am looking forward to learning about your linear rails and how they mount with particular reference to your need to lap the steel to the tolerances you quote. Which brings up the question what are you going to machine on this tool and what kind of tolerances are you aiming for?

Thanks,

Steve

[Marcus BowmanParticipant @marcusbowman28936]

John,

Talking of tolerances, what type of leadscrews will you be fitting, and what type of belts to drive the axes (unless they will be driven directly)? I assume ballscrews, but wonder what class/tolerance and arrangements for controlling backlash. The same is true of belts, which vary in the extent to which they introduce errors in positioning.

I know on my own mill, belt design has advanced in the last 10 years, and modern profiles are much better at transferring motion with reduced error.

Marcus

[John McNamaraParticipant @johnmcnamara74883]

Thanks Fellas

Yes clear resin mold would be a great conversation piece.

I would be tempted to experiment with polymer concrete if the shrinkage and cracking can be controlled instead of epoxy but that will be after the Epoxy/aggregate mill is built.

Its pretty clear that the total accuracy of the machine will be a lot less than the accuracy I was able to apparently achieve with the steel rail mounts, I said apparently because do not really know if the surface plate is truly flat to inspection grade i suspect it is within about 3 tenths or for that matter if the indicators I used are in perfect order although I think they are.

Alexander J Slocomb at MIT mentions an "error budget" in his book "precision machine design". also in this paper,

"Understanding and modeling errors in machines"

W >**LINK**orth reading, it confirms common sense that overall the accuracy of a machine will be the sum of all the separate error generating parts. We must assume that each part will generate some error, nothing is perfect.

The mil I am building is not going to be a micron level super machine, hopefully it will be a lot stiffer and accurate than many of the small import mills being offered and it is designed for CNC at a budget. I wanted the design to be simple enough to allow a skilled person with a small lathe, a drill press, access to surface plate, hand and measuring tools and access to laser cutting for the mold and some of the machine parts. Optionally the mold could be made from MDF by hand.

So far the machine has rewarded me greatly, every day it explains very clearly what works and what can be improved. I the end it will reflect the sum of the parts.

What will I make with it? more machines!

[John McNamaraParticipant @johnmcnamara74883]

Hi Marcus

I allowed for double nut Asian rolled ball screws this should reduce the backlash somewhat while not breaking the budget. There will be more lead error than from precision ground ball screws. The same applies to the linear rails. however if higher spec rails are needed they should just bolt straight in as long as the hole spacing is 60mm and the overall height from the bottom of rail to to top of the slider block. Many manufacturers offer this as standard.

**LINK**

For the timing belts GT2 belts appear to offer the best accuracy, more expensive than AT style belts.

Edited By John McNamara on 06/01/2019 12:56:48

[John McNamaraParticipant @johnmcnamara74883]

Hi all

And then there were two….

The columns that support the gantry cross member are now prepared and undercoated.

I increased the amount of epoxy to 18% by volume on the first and last layer (I placed and tamped the epoxy/aggregate in 5 layers) This gave a better finish.

The epoxy was allowed to cure then the side was covered in automotive body filler while still in the mold. This was allowed to cure then sanded flat using the mold as an edge guide. The other sides were also prepared after removing the casting after a 24 hour cure. As you can see from the painted images below the result is very crisp lines. I used a vibrating half sheet power sander and a half sheet plasterers joint sander by hand. All the non steel edges were rounded carefully by hand to about a 1.5mm radius. Finishing as usual took a fair amount of time, Finally a coat of etch primer was applied, There are still a few blemishes they will be fixed before the top coat which will be done after the final assembly of the frame is completed.

Comparing the two columns visually the steel mating surfaces are in perfect alignment. I will measure the actual error later when the next mold is removed from the surface plate. The design allows for a maximum misalignment of 2mm. I am guessing the error is under 0.25mm. The column on the left has masking tape over the metal face.

Next is the base, when this is poured I will be able to test assemble the machine and check for alignment, there should not be any problems so far all the parts are within spec. The columns are going to be screwed straight down on the base without any adjustment, hence the importance of their accuracy. When the gantry cross member is placed on the step and bolted in position and the built in jacks used to align the linear bearings it carries to the base ways there will be a small gap left that will be filled with epoxy before final assembly.

The following paper is worth reading. it covers building a precision machine, it uses the same method to assemble the components.

**LINK**

Regards
John

[SteveIParticipant @stevei]

Hi John,

Wonderful job. Very interesting and I am working my way through the paper you linked to.

Thanks,

Steve

[Neil WyattModerator @neilwyatt]

More remarkable stuff, John.

Neil

[David George 1Participant @davidgeorge1]

John it looks a decent bit of kit that you are making can't wait to see the complete chasis.

David

[John McNamaraParticipant @johnmcnamara74883]

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

[VicParticipant @vic]

You are making excellent progress John and I’m very impressed with the finished results. I’m quite surprised at how yellow your “Epoxycrete” looks in some pictures but then appears a nice shade of grey when set. Can you explain this, what type of sand are you using?

[John McNamaraParticipant @johnmcnamara74883]

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

[Marcus BowmanParticipant @marcusbowman28936]

John,

You said:

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.

I'm off to mix some cement for a small foundation for a wall, this morning, and I wonder

(a) whether you needed to exclude moisture by using kiln dried sand?

(b) why exclude dust? I have used 'granolithic' as a screed, and that is mostly aggregate, with some cement. The aggregate is described as '6mm to dust' and the dust contributes to the strength, possibly because, like a larger mixed aggregate, the different grain sizes of the sand and aggregate lock well together, and provide strength. Would that not work in the same way with the epoxy mix?

(c) Experience tells me that if I lay a screed on a floor, then work it to a fine flat finish using a float, I need to take care not to over-work the screed, because the more I press it, the greater the tendency for the larger particles to work their way to the top as the smaller particles are forced downwards into the spaces between the larger particles. That can spoil the finish, as well as (I suspect) producing a kind of layering effect, with smaller particles tending to be more concentrated further down the mix. I note that you tamped in layers. Did that help the produce a more uniform distribution of particles? Might be rather difficult to tell, of course, but I shall spend the rest of the day pondering… Perhaps someone has done tests and reported results in one of the many papers on the subject?

Great progress, though. And I agree with your thinking re: concrete reinforcement bars ('rebar' in the UK) and 'inexactly placed' reinforcement.

Marcus

[John McNamaraParticipant @johnmcnamara74883]

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

[John McNamaraParticipant @johnmcnamara74883]

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

[John McNamaraParticipant @johnmcnamara74883]

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

[VicParticipant @vic]

You’re making very good progress John and the results are impressive. I can’t wait to see it all in action when it’s finished. Thanks for your marvellous documentation of the project and sharing of materials and links etc.

[Author]

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