Replacement table for cnc machine - help required - Apply within!

alan2525 · 05-01-2008

I always seem to be asking questions on this forum - so time for another one!

I'm making a replacement table for my cnc machine as the table supplied just has a few T-Slots, it'd be much more practical to make a tool plate with holes drilled at regular spacing to which I can attach workpieces, jigs etc. I wanted to use a sheet of 8mm aluminium for the toolplate.

The only problem is that the table height is already quite high, I'd like to make a new table (lower to allow for the additional 8mm toolplate) from something rigid and dimensionaly stable which isn't affected by oils and water! I use WD40, water and soluble oil as coolant. Can anyone recommend a suitable material for these purposes? Ideally it would need to be approx 305 x 230 x 20mm. I'd want something free machining as I'd use the machine to skim it in situ. I'd also want something cheap and (Reasonably) readily available!

Any ideas would be appreciated!

**Bunkerbarge** · 06-01-2008

I think cheaper bed plates are made of cast iron but more expensive ones are made of cast steel. The better the quality the higher grade the cast steel i.e. more carbon and chrome added. Either will require oiling on a regular basis just as any bed plate so resistance to water will be a similar issue.

Have you thought of looking at a cheap chinese surface plate that you can machine to your own requirements such as these?

http://cgi.ebay.co.uk/SURFACE-PLATE-...QQcmdZViewItem

http://cgi.ebay.co.uk/TILTING-ANGLE-...sid=p1638.m118

kevingambrell · 06-01-2008

HI Alan

Tables are always cast iron due to the stability of the material. My Bridgeport has a cast iron table and thats only about three years old. Cast iron is fine with soluble cutting oil and WD40.
What size is the table you are looking to replace? and what machine is it on? I can point you to places that sell castings for tables but bare in mind you will have to machine your own T slots and line bore for teh lead screw.

Let me have the size and make and il ask around.

Cheers Kevin

alan2525 · 06-01-2008

Sorry - I didn't make it very clear what kind of machine it is!

Here's a picture of the machine, it's a desktop engraving / modelling machine:

The table supplied with the machine is fabricated from steel and has a few sparsely placed Tee slots for holding down items. I wanted to make a tool plate similar to one of these, so I can fit stops, hold downs, etc:

The problem was that I didn't want to lose any of the travel on the Z-axis as it only has 30mm travel. I use the machine for cutting Brass, Plywood and Plastics. The sub-table could be Acrylic of even MDF if I was using it without coolant, but as I cut some brass on the machine I'd need something impermeable to cutting fluids. I could use Aluminium however I'd like to use something cheaper if possible!

kevingambrell · 06-01-2008

Hi Alan
With only 30mm on the X your looking at loosing atleast 1/3rd of that fitting a sub table. What about a lump of hot cold rolled mild steel? or better yet a lump of Gauge plate maybe 1/4 inch thick. Would be a sod to drill and tap but its ground flat from the get go.

Im at the machinery sales Tuesday il ask around see what there is to be had.

Cheers Kevin

alan2525 · 11-01-2008

How does £20 sound for a piece of offcut 8mm aluminium plate dimensions:

ALUM ALLOY PLATE 6082T6
1 Off 8mm x 0.325 x 0.235 Metres 20.00 Each

sounds like an ungodly act of RIP-OFF to me! Alternatively a 500mm x 500mm sheet (8mm) for £41.75 - which seems a little better bet still close to daylight burglary.

Anyone know any decent scrappies for offcut bits in small quantities? - I've always been scared of going near the places and have to shout at some guy called RON who looks like the back of a giant tattooed rottweiler as he throws cars around whilst piloting a vehicular device from MAD MAX.

kevingambrell · 11-01-2008

Hi Alan
I would have to agree the prices are a joke. I buy a lot of stock, Aluminum, bronze, copper and mild steel. Every time i put in an order the prices have gone up. I hate the feeling that im being asked to bend over for this stuff and more so as the metal men dont offer vasaline.

Il have a look see whats laying about in the shop and get back to you later today.

Cheers kevin

alan2525 · 11-01-2008

Ouch - I did say the prices were daylight robbery and not daylight bu**ery didn't I?

I'd appreciate if you could have a look in your shop for any offcuts aluminium! Atleast I hope you were looking for the aluminium and not the vaseline!

**rjwood_uk** · 11-01-2008

lol, not that i know about any of these things your on about...just wanted to let you know where the phrase "daylight robbery" comes from.

back in the "some time" (before vitorian i think) the govournment decided that richer people should pay more taxes, richer people had bigger houses, bigger houses had more windows. so they decided to tax windows. a certain amount per window. hence "daylight robbery"

and also you will notice lots of smaller old building have bricked up windows. this was to save money (people will always find a way around the tax man lol)

just a bit of useless information there.

alan2525 · 11-01-2008

I once visited a stately home where they had bricked up the windows originally when London was infected by the ghastly black death! The windows faced towards London, I imagine to reduce the chances of infection, the view probably wasn't too pleasant either though! They never actually knocked the brickwork out afterwards, I imagine with the taxation on windows - they saved a few quid too!