Author Topic: Building a milling machine  (Read 50328 times)

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #25 on: March 04, 2014, 12:23:21 PM »
It's been a good day today, the enforced delay due to the weather has given me time to plan the next stages which meant that I was working efficiently and got far more done that I had anticipated.
Firstly I cast the second of the top body sections and after fettling I got them bolted together.

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #26 on: March 04, 2014, 12:24:59 PM »
I then mounted the top section onto the bottom and bolted them together.

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #27 on: March 04, 2014, 12:29:16 PM »
I then fitted the top casting to the main frame and bolted that into place.
So far none of the assembly has been precision work, an angle grinder and a drill is all I've needed. The next part is to fit the front, this has to be done accurately to ensure that the front is at right angles to the top tube.

Offline mattinker

  • Hero Member
  • *****
  • Posts: 1028
  • Country: fr
Re: Building a milling machine
« Reply #28 on: March 04, 2014, 01:03:50 PM »
Thanks for posting, I'm looking forward to seeing where this is going!

Regards, Matthew

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 5532
  • Country: gb
  • East Sussex, UK
Re: Building a milling machine
« Reply #29 on: March 04, 2014, 02:53:55 PM »
 :thumbup: Looking good Norman  :thumbup:

You must be emptying the local scrap yard of gearbox cases and wheels  :lol:
Andrew Mawson
East Sussex

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #30 on: March 05, 2014, 11:38:08 AM »
One casting that I have been having trouble with is the spindle mount, it is basically just a 4" hollow cube. I tried twice to mould it in sand but both times the centre broke away. I then made a core box and tried to make a core using sodium silicate. Somehow the CO2 did not penetrate and it was unsuccessful. I then tried a baked sand core but that failed too.
Then I had a "eureka" moment, I had some ceramic fibre insulation board left over from making my furnace and I cut a piece to size to use as a core. I was concerned that as it is so light it would move as I poured the molten metal in so I anchored it in the sand with a couple of woodscrews in the back. It was a successful pour and the fibre board was very easy to remove from the casting.
I also needed a cover for this part to keep the oil in for the bearings, as a bit of fun I cut my initials from thin ply to decorate the front of the cover. I half expected the sand to break up but that cast well also.


Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #31 on: March 05, 2014, 11:44:36 AM »
I've also been working on the front casting. I had made it oversize to ensure that there would be no gaps and I had to reduce the width by 3mm to make it fit. I started with an angle grinder but soon discovered that a "Surform" plane removed the metal very quickly and I was able to keep the sides straighter than I could with the grinder. No pictures yet.
« Last Edit: March 05, 2014, 02:47:22 PM by NormanV »

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #32 on: March 07, 2014, 01:02:34 PM »
More progress on the front casting. I got it down to width and fitting between the sides nicely. Then came the first critical part of the build. The front surface has to be flat and the only means at my disposal was to scrape it. I have a large angle plate that could serve as a surface plate and I set to scraping. I spent the whole of yesterday on it and made some good progress. It went from touching on two diagonally opposite corners only to about 30% of the surface touching the surface plate. This morning I started afresh but soon realised that with the amount of metal that I still had to remove I had a good week of scraping ahead of me. I am not that patient! I phoned a local engineering company and the agreed to mill it flat for 30. I thought that that was a bargain and now the job is done.

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #33 on: March 08, 2014, 12:59:59 PM »
Had a frustrating morning, I drove 30 miles to my nearest fastening supplier and found that they were shut! However on my way back home I passed a farm supplies shop and they had all that I needed. I'll go there in future as they are only 15 miles down the road.
With the screws that I bought I was able to fit the front casting to the body complete with a piece of 4" x 1/2" CRS that is going to act as the vertical slide. This had to be at 90 degrees to the mounting for the top tube and this was achieved using a "rafter square". Not the most precise piece of equipment but near enough at this stage as I will put shims under the top tube to set it accurately on final assembly.
There was an awful lot of drilling and tapping today, there is a total of 56 fasteners on it so far.

Offline Arbalist

  • Hero Member
  • *****
  • Posts: 677
  • Country: gb
Re: Building a milling machine
« Reply #34 on: March 08, 2014, 01:38:20 PM »
This is progressing nicely!  :thumbup:

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #35 on: March 08, 2014, 04:32:12 PM »
I mentioned in an earlier post that I intend to fill the body of this machine to reduce vibration. I could use concrete which would be cheap or a mixture of epoxy and gravel. My concerns over using concrete are shrinkage and retention of moisture. Epoxy will be much more expensive, or how about polyester resin (as used for fibreglass).
Has anybody any experience of doing this who could offer advice?
Thanks, Norman

Offline chipenter

  • Hero Member
  • *****
  • Posts: 726
  • Country: gb
Re: Building a milling machine
« Reply #36 on: March 09, 2014, 03:46:33 AM »
If you used strong concrete and vibrated it to remove air bubbles , it will be waterproof and ridgid not to menshon heavy .
Jeff

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #37 on: March 09, 2014, 07:27:08 AM »
What do you mean by strong concrete?

Offline Arbalist

  • Hero Member
  • *****
  • Posts: 677
  • Country: gb
Re: Building a milling machine
« Reply #38 on: March 09, 2014, 01:00:33 PM »
Polyester Resin should be fine I would have thought, mixed with sand and gravel.

Offline awemawson

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 5532
  • Country: gb
  • East Sussex, UK
Re: Building a milling machine
« Reply #39 on: March 09, 2014, 02:45:31 PM »
If you can get some chilled iron shot, as used for sand blasting, it will be significantly more dense than aggregate. And I agree that polyester resin should be fine.
Andrew Mawson
East Sussex

Offline Arbalist

  • Hero Member
  • *****
  • Posts: 677
  • Country: gb
Re: Building a milling machine
« Reply #40 on: March 09, 2014, 05:28:37 PM »
Actually I did see a thread somewhere where someone used old steel fasteners as part of the mix for their mill.

Offline chipenter

  • Hero Member
  • *****
  • Posts: 726
  • Country: gb
Re: Building a milling machine
« Reply #41 on: March 10, 2014, 04:07:31 AM »
Strong concrete a mix of 5or 6 to 1 the smaller the agregate more cement is needed to cover the gaps , and should go a very light grey almost white .
Jeff

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #42 on: March 10, 2014, 10:08:16 AM »
Sorry Jeff but you are speaking to a thicko here regarding concrete. Could you explain more fully please.
Norman

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #43 on: March 10, 2014, 02:08:59 PM »
For the platform that supports the x and y axis I had originally planned to make an aluminium casting but I soon realised that would give me two large flat surfaces to level off and to get at 90 degrees to each other. It would also be too big to fit on my lathe to machine it. Instead I bought a large (18" x 12" x 8") angle plate that would give me the built in accuracy without any problems of machining it. All I had to do was to cut it in half. This I did with my rubbish angle grinder which burnt out under the strain (thank heavens for a two year guarantee) and a hacksaw for where I couldn't get the angle grinder to fit.
Here it is before I attacked it with the hacksaw.

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #44 on: March 11, 2014, 10:55:11 AM »
This machine is getting quite heavy now and when I fit the table I will not be able to lift it. It is time to build the bench upon which it will live. I had originally planned to make it from metal but that would first mean that I would have to buy a welding machine. The cost of that combined with the cost of the steel made me look at timber construction. I have built this bench using 3" x 2" timber for the frame with 1/2" particle board for the cladding. It seems very stable but time will tell. At least I have got somewhere semi-permanent to keep it for now. I will be giving it a coat of paint to make it look a little better and I'll get some handy storage in the sides.

Offline chipenter

  • Hero Member
  • *****
  • Posts: 726
  • Country: gb
Re: Building a milling machine
« Reply #45 on: March 11, 2014, 03:32:47 PM »
one part cement to 5 parts aggrigate by volume , I would recoment 10mm aggrigate flint or granite for waterproof , and vibrated with say a hammer drill on the outside of the shuttering will make the wet cement almost flow and fill all the corners .
Jeff

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #46 on: March 11, 2014, 04:08:52 PM »
So, no sand?

Offline chipenter

  • Hero Member
  • *****
  • Posts: 726
  • Country: gb
Re: Building a milling machine
« Reply #47 on: March 11, 2014, 04:41:00 PM »
sand yes comes with the ten mm aggrigate or ballest sometimes called grano  for hard floors .
Jeff

Offline Pete W.

  • Hero Member
  • *****
  • Posts: 747
  • Country: gb
Re: Building a milling machine
« Reply #48 on: March 11, 2014, 05:50:25 PM »
Hi there, Norman,

If you have a branch of B&Q or Wickes near you, you should be able to find a 'How To' leaflet on concreting.  Otherwise, try Google.

The type of aggregate available will vary a bit according to your location.  For instance, up the Thames valley, it's usually pit ballast from gravel-pits on the flood-plain.  In South Devon, where my parents lived after they retired, it used to be gritty stuff rejected by the Cornish china clay industry while here in East Hampshire, some builders' merchants supply aggregate dredged from the sea bed.  It gets washed and graded (aka sieved) to separate different grain sizes.  In other parts of the country it might be crushed stone or even ex-demolition crushed concrete.  It all depends on the local geology.  If you ask your local supplier I'm sure they will explain what is common in your area.

When I lived in Essex, I used to use 'as dug' ballast which is everything from " down (except that it was washed to remove the clay) so that was coarse plus fine combined.  Some recipes will call for the coarse and fine constituents separately - you combine them during the mixing.

You need enough fine aggregate (sand and fine gravel) to almost fill the spaces between the coarse aggregate, otherwise you'll need to add more cement.  I agree with Jeff's advice about the aggregate to cement ratio but it isn't too critical, you don't need a laboratory balance to weigh the ingredients!  (Well, actually, I expect you'll find most recipes measure by volume, not weight.)  Actually, a builder's shovel is a recognised measure in some older tables of weights and measures.  I'd suggest that for your quantities, a domestic coal shovel will do fine.

If you're mixing by hand, you turn it over three times dry and then three times wet, adding the water little by little.  If you're using a mixer, you need to add at least some of the water first.

You shouldn't add too much water, else you'll get shrinkage.  If you're going to vibrate as Jeff suggested, it should almost seem too dry as you put the mix into the mould (shuttering) and the vibration will mobilise it.  (Have you seen that video of liquifaction of the soil beneath a building foundation during an earthquake?!?)  If it doesn't mobilise, you can always tip it out and add a little more water, mix and re-pour.  However, you mustn't let it dry out for at least three days.  The chemical reaction of the concrete setting requires available water until the concrete has cured, so visit it regularly with the watering can or keep it covered with wet sacking and in the shade.

Once it's cured and really dried out, there might be some slight shrinkage but you could maybe introduce some polyester or epoxy resin into the cracks between the concrete and the metal. 
Best regards,

Pete W.

If you can keep your head when all about you are losing theirs, you haven't seen the latest change-note!

Offline NormanV

  • Hero Member
  • *****
  • Posts: 517
  • Country: gb
  • United Kingdom
Re: Building a milling machine
« Reply #49 on: March 12, 2014, 07:07:25 AM »
I have now fitted the knee (I think that is the right name for it) and am pleasantly surprised how freely it slides up and down the column and lock without any shake. There is a block of wood under it to keep it in position, the next job is the screw that will raise and lower it. I am planning to use a 28mm acme threaded rod that is sold as a screw for a woodwork bench vice. After considering various geared methods of operating it I have settled on a ratchet mechanism to do it. It may be slow but it is within the cost restraints.

Thank you for the advice on concrete, I may do that soon but must be careful not to do it before I am finally certain that I won't need to dismantle anything.
Here's the screw and a pic of the machine as it now stands.