Are T-slot tables necessary and is it worth paying more for steel?

[Goemon]

The table is one of the last parts I need to buy or build for my CNC router project but I need a little advice (as usual...).

First: Why do most people use T-slot tables? Are people using T-slot clamps to hold work in place?

I couldn't find many "t-slot clamps" that look right for CNC work holding. Is there a different name for CNC t-slot clamps that I should be using as a search term instead?

Is anyone here using something other than a T-slot design for their table? My interest is specifically for desktop machines that are used for milling aluminum (or other metals)? I am trying to understand what my options are...

My base / frame is made from a mix of steel and epoxy granite with carbon fiber? I was going to use the same epoxy granite / carbon fiber mix for the table with threaded inserts so I could bolt work to it directly. I am wondering if I should be embedding some aluminum t-slot extrusions in the epoxy mix or bolting blanks directly to the table would provide a stronger grip.

Would an aluminum table be a point of weakness in a machine with a steel and carbon fiber frame? I.e. Would it be sacrificing some accuracy or is the stiffness of the table less important than the gantry and frame?

There doesn't seem to be many (or any) lower cost steel T-slot table options of a suitable size for my machine. Does the table need to be as long as the intended work piece? I.e. If I plan to mill aluminum molds from blanks that were 32" long, would my table need to be at least 32" or could I get away with a 24" table and have some overhang?

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[skrubol]

T-slots are a convenient way to clamp things down, but not the only way. Almost all metal working mills use T-slots, but those generally have long cast iron tables. Makes it a bit easier to drop a vise on, their mounting points aren't standardized, so with tapped holes the vise mounting points might not line up.
If you're doing your own fixturing it's a bit less critical. Tapped holes or threaded inserts may work perfectly well for you.
The table generally should be at least as large as the usable area of the machine. If your part needs to be cut in 2 setups, or if the ends of the part aren't cut, having some hanging over the end isn't terrible (but isn't desirable either, might get ringing on the unsupported end.) Generally you want to buy/design around what the biggest thing you plan on regularly cutting is.
iron/steel tables are usually cast specifically for a certain mill. Aluminum is not as rigid as steel or iron, has more resonance and thermal expansion issues, but it's very common on routers, especially if it's backed by a steel frame and is semi-consumable. Is your design going to have a moving gantry or moving table?

[NIC 77]

T-slots are a convenient way to clamp things down, but not the only way. Almost all metal working mills use T-slots, but those generally have long cast iron tables. Makes it a bit easier to drop a vise on, their mounting points aren't standardized, so with tapped holes the vise mounting points might not line up.
If you're doing your own fixturing it's a bit less critical. Tapped holes or threaded inserts may work perfectly well for you.
The table generally should be at least as large as the usable area of the machine. If your part needs to be cut in 2 setups, or if the ends of the part aren't cut, having some hanging over the end isn't terrible (but isn't desirable either, might get ringing on the unsupported end.) Generally you want to buy/design around what the biggest thing you plan on regularly cutting is.
iron/steel tables are usually cast specifically for a certain mill. Aluminum is not as rigid as steel or iron, has more resonance and thermal expansion issues, but it's very common on routers, especially if it's backed by a steel frame and is semi-consumable. Is your design going to have a moving gantry or moving table?

You took the words out of my mouth.

I'd consider an aluminum plate that you can drill holes in at regular intervals, tapped, or with threaded inserts, to match any vices you might use. Also, I'm guessing it will be easier to surface an aluminum plate than it would be to surface T Slot.

But that's just my opinion, I don't claim to be an expert on the subject.

Have you seen this thread?

http://www.cnczone.com/forums/uncate...uminium-4.html

Nice T slot table used there. Looks like it works well for him.

[pippin88]

MDF. Can drill holes wherever you want. Can cut into surface without worry. Then resurface when needed. Put in dog holes for dogs and clamps.

I had a T slot table on previous machine. Wasn't as good as I thought it would be. Worried about cutting through. Had to use scraps as spoil boards. Was slippery and therefore clamps needed to be tighter.

[Goemon]

T-slots are a convenient way to clamp things down, but not the only way. Almost all metal working mills use T-slots, but those generally have long cast iron tables. Makes it a bit easier to drop a vise on, their mounting points aren't standardized, so with tapped holes the vise mounting points might not line up.
If you're doing your own fixturing it's a bit less critical. Tapped holes or threaded inserts may work perfectly well for you.
The table generally should be at least as large as the usable area of the machine. If your part needs to be cut in 2 setups, or if the ends of the part aren't cut, having some hanging over the end isn't terrible (but isn't desirable either, might get ringing on the unsupported end.) Generally you want to buy/design around what the biggest thing you plan on regularly cutting is.
iron/steel tables are usually cast specifically for a certain mill. Aluminum is not as rigid as steel or iron, has more resonance and thermal expansion issues, but it's very common on routers, especially if it's backed by a steel frame and is semi-consumable. Is your design going to have a moving gantry or moving table?

I have been designing and making all the parts for a moving gantry system but I have this nagging feeling that I'm doing it wrong and should be making a moving table system instead for what I plan to use it for.... it seems like a fixed gantry is best practice for milling aluminum.

The part that worried me about the moving table designs was how far apart to spread the bearing blocks and, as a result, possibly sacrificing cutting space for stability. I have 40" rails for the x-axis and need 30" of cutting space. I wasn't sure that spreading bearing blocks 10" apart would be sufficient on a 30" table.

Anyway... for now, I am making a moving gantry system. My design is based on this guy's design:

https://hackadaycom.files.wordpress....nner.jpg?w=800

I likened the idea of the x-axis rails being mounted high with minimal need for gantry risers. As you can see, the design has the table (or table base) cast with the rest of the frame as one solid piece. Mine differs from the one in the pic in that I use steel instead of aluminum for the frame support and my epoxy granite mix has 50% carbon fiber and fiberglass : 50% sand plus 1 kg of carbon nanotubes. My gantry beam is carbon fiber instead of aluminum too.

[Goemon]

What sort of clamping system or vise would be best for hold horizontal aluminum slabs that are approx 30" x 8" x 2" thick?

I am planning to use it to make aluminum molds. If the slabs are held in a traditional vise and the vise was mounted horizontally (as it would be for mold making), the aluminum work piece wouldn't be supported by the table (unless the vises were mounted lower than the table).

In this scenario, is there a better alternative to simply attaching the aluminum mold blank directly to the table with screws? I guess I could use T-slot nuts and screws to attach it directly to a t-slot table in the same way.

What is the deal with these vacuum tables? Are people using vacuum pumps to make diy vacuum vises?

[skrubol]

Moving table types can usually be made more rigid, but given your limitations (40" slides, 30" cutting space,) I think you'll be able to make a much better machine with a moving gantry. 10" of block spacing is really narrow for 30" of cutting area. I think you'd want at least 50% more rail length than cutting space (probably more like 75%.)

[skrubol]

If you were going to clamp a piece with those dimensions in a vise, you'd probably want to use at least 2 vises, I'd probably go with 3 or more. Maybe not the most practical.. Screwing the part directly to the table or T-nuts is definitely a good option if you don't mind drilling a bunch of holes in your part. There are also clamping kits (like this 58 pc. Clamping Kit for 1/2" T-Slots | Grizzly Industrial) if you don't want to make your part swiss cheese. They do have specific sizes, check that the studs match the inserts or tap, and just don't use the T-nuts, there's probably not much cheaper a way to get a set of strap clamps and studs even if you don't need the T-nuts.
If you aren't familiar with their usage, Tormach has a decent video on the subject:
If you need access to the whole top of the piece, like you would have in a vise, there are also toe clamps, Mitee bite has tons of options.

[NIC 77]

What sort of clamping system or vise would be best for hold horizontal aluminum slabs that are approx 30" x 8" x 2" thick?

I am planning to use it to make aluminum molds. If the slabs are held in a traditional vise and the vise was mounted horizontally (as it would be for mold making), the aluminum work piece wouldn't be supported by the table (unless the vises were mounted lower than the table).

In this scenario, is there a better alternative to simply attaching the aluminum mold blank directly to the table with screws? I guess I could use T-slot nuts and screws to attach it directly to a t-slot table in the same way.

What is the deal with these vacuum tables? Are people using vacuum pumps to make diy vacuum vises?

Yes, that sounds like a better idea if that is what you plan on using your machine for exclusively. Two vise, one at each end. Use parallels to offset the work piece in the vices. I have been looking at making some custom screwless vices for what I'm building from aluminum. Or I may just buy some. But if you search around, you can find some vise step by step instructions from people who have made their own if you want to make some custom sizes.

Do you play chess? Or perhaps someone else uses the same user name. If you do, pretty sure I have beat you a few times .

[skrubol]

Forgot to comment on vacuum tables. If you aren't planning on poking a bunch of holes through your part, a vacuum table might not be a bad solution for you. Should be able to get somewhere in the neighborhood of 3000 lbs hold-down force, and if you're looking to go diy, vacuum tables can be made pretty inexpensively and without a ton of work.
I've never actually used one (never had a need, I'm just a hobbiest at this point,) but one thing I've heard is you still want to have alignment pins of some sort when using vacuum, as there isn't a lot to resist the part slipping a bit.

[awerby]

If those slabs are all 2" thick, you can hold them by the edges, using Miteebite clamps https://www.miteebite.com/products/m...itbull-clamps/. That way, you won't have hardware sticking up that you might hit while doing a rapid move.

[wizard]

Obviously wood is out of the question if you intend to mill aluminum

Steel isn't a bad idea, but sized for a machine this large will be extremely heavy and hard to handle. You would need a plate at least a half inch thick so using that and the projected table size you can calculate the weight. Also a steel plate might not be as flat as you would like and frankly you need to factor in blanched grinding the plate as a minimal amount of work required to implement. On the flip side you can drill and tap a steel plate and not have to worry about thread inserts as you would for an Aluminum plate.

Aluminum tooling plate is not cheap, that is a huge factor right there, plus you need to consider thread inserts for most of the threaded holes you want to use in the plate. On the other hand tooling plate if very flat (relatively) to begin with. Tooling plate is probably the best solution for a IDY project that wants good accuracy with a minimal of equipment or third party help, to pull off a precision table.

As far as aluminum extrusions go, there are extrusions made to implement machine tables with. One example: Techno Aluminum Extrusion Table Plates - perfect for work stations and automated applications requiring aluminum extrusions, t-slotted table plates. but note that these requires a substantial frame underneath. The heavy duty extrusions are only 20 mm thick over all, which frankly isn't much on a large table, especially when you consider most the extrusion is only about 8mm thick. If you did go the extrusion route you would want something fairly substantial as the common T-Slotted structural extrusions are just too thin in the webs, in my opinion.

Personally I'd go with a steel or aluminum plate mostly because you seem to know exactly what you will be using the machine for and have high expectations for performance. Just be aware that such a plate either has to be rather thick or well supported. On a moving gantry machine it is fairly easy to put support under a table so in your case you likely can get by with a thinner table. On the other hand you do have the composites experience many of use envy and thus might be able to produce a viable composite table. I would imagine thought that you would need a large flat table to begin with so that might be a problem.

If you did go the composites route that would allow you to design in all sorts of clamping options. Threaded inserts would be easy, you could also do steel T-Slots, though you may have to have the steel pieces custom made. You could also embed keyhole type slots. Plan ahead and you could have airlines embedded in the table itself. For coolant drainage you can mold in channels to guide the coolant ways from the table top. Obviously a composite lay up offers you plenty of possibilities that would likely require a cast table in the past or a lot of expensive machining time.

[wizard]

What sort of clamping system or vise would be best for hold horizontal aluminum slabs that are approx 30" x 8" x 2" thick?

This is extremely tough to answer because there are so many options. You could bolt the blank directly to the table top, use a vise, low profile clamps, toe clamps or a combination of these. In the end you may end up experimenting too find a process the works best for you. In the end you will likely need more than one method to cover all aspects of the part. Personally I like bolting things directly to a machine table if the part allows for it. If this is a production part you likely would want to bolt the stock to a custom sub table that registers the parts in place. This can be likened to how parts are bolted or clamped to a Tombstone on horizontal milling machines.

I am planning to use it to make aluminum molds. If the slabs are held in a traditional vise and the vise was mounted horizontally (as it would be for mold making), the aluminum work piece wouldn't be supported by the table (unless the vises were mounted lower than the table).

I'm not sure I follow that. However using multiple vises may not work out that well if you need to profile more that one edge.

In this scenario, is there a better alternative to simply attaching the aluminum mold blank directly to the table with screws?

Actually that would be my first choice. It keeps the work pieces in full contact a rigid with the table and saves buying several vises. Depending upon how you do your table you would either have dedicated holes drilled and tapped in the table or you would have T-Nuts locked in place. Your blank molds would be predrilled for the hole standard that you came up with. You take the blank, drop it in place and bolt it down and go. If needed locators for two edges could also be used.

I guess I could use T-slot nuts and screws to attach it directly to a t-slot table in the same way.

You certainly can.

What is the deal with these vacuum tables? Are people using vacuum pumps to make diy vacuum vises?

Vacuum tables are great for certain types of work. For what you are describing though I wouldn't really recommend them. For one your raw stock would need to either be very flat or easily deformed to seal properly against the vacuum table. Second you are narrow in width and long in length this is less than optimal for holding unless you design a vacuum vise specific for that stock. It is worth noting that vacuum tables ideally will be supplied with locator pins to prevent stock slippage. In other words vacuum tables are great if they fit the task at hand, I'm just not convinced they are a good choice here. Beyond that a vacuum table requires a vacuum pump, in this case a thick slab of aluminum to implement the table and a bit of plumbing. The key to understanding vacuum tables is that at best you only get 14 PSI of downward pressure. Usually the ultimate clamping pressure is a bit less than that, the point is though that the forces become massive on a large plate.

[Goemon]

If you were going to clamp a piece with those dimensions in a vise, you'd probably want to use at least 2 vises, I'd probably go with 3 or more. Maybe not the most practical.. Screwing the part directly to the table or T-nuts is definitely a good option if you don't mind drilling a bunch of holes in your part. There are also clamping kits (like this 58 pc. Clamping Kit for 1/2" T-Slots | Grizzly Industrial) if you don't want to make your part swiss cheese. They do have specific sizes, check that the studs match the inserts or tap, and just don't use the T-nuts, there's probably not much cheaper a way to get a set of strap clamps and studs even if you don't need the T-nuts.
If you aren't familiar with their usage, Tormach has a decent video on the subject:
If you need access to the whole top of the piece, like you would have in a vise, there are also toe clamps, Mitee bite has tons of options.

Drilling holes in my parts is not really a problem. In fact it is necessary regardless of how it is clamped to the table. I'll be making two-part molds. I can use the threaded holes to index and hold the two mold halves together when in use. The flange (perimeter around the mold cavity) can hold a bunch of holes without affecting the strength of the mold if it it made from 2" thick slabs of aluminum.

I guess that leaves the question about what to do with other parts if I wanted to use it for something other than molds. Right now the only other thing I could see myself wanting to use it for is making wood or aluminum stocks using a 4th rotational axis. I am planning to use a double head stock / 2 chuck solution for that so I have a work holding solution for that. I still need to be able to attach the head and tail stock though.

On a practical note though, a T-slot table with t-nuts does sound like a convenient method of attaching both mold blanks and 4th axis components where perfect alignment is necessary. It also seems like it would be easy to change the size, shape and height of the table as needed by simply rearranging or switching out t-slot sections.

[Goemon]

Yes, that sounds like a better idea if that is what you plan on using your machine for exclusively. Two vise, one at each end. Use parallels to offset the work piece in the vices. I have been looking at making some custom screwless vices for what I'm building from aluminum. Or I may just buy some. But if you search around, you can find some vise step by step instructions from people who have made their own if you want to make some custom sizes.

Do you play chess? Or perhaps someone else uses the same user name. If you do, pretty sure I have beat you a few times .

I used to play a lot chess but never online. It must be a different Goemon (we all look the same!). I go by the name Zebra on most other sites. It was already taken on this site so I had to choose something else. Goemon is my go to user name on sites where every name I try is already taken. It saves me from having to use Zebra77625 or something else I would forget. It's an awesome but obscure Japanese ninja movie so the name is usually free.

I used to play a lot of chess with my family and when I moved to NYC I used to go and play against people in the park. I was never very good though. I am fairly sure you would beat me easily if you're a good player.

I used to play with the 2nd best under 16 chess champion in the U.K when I was a kid so I got to see a little of what a good player is really capable of. He was like a different species to me. a genuine genius.

[Goemon]

Forgot to comment on vacuum tables. If you aren't planning on poking a bunch of holes through your part, a vacuum table might not be a bad solution for you. Should be able to get somewhere in the neighborhood of 3000 lbs hold-down force, and if you're looking to go diy, vacuum tables can be made pretty inexpensively and without a ton of work.
I've never actually used one (never had a need, I'm just a hobbiest at this point,) but one thing I've heard is you still want to have alignment pins of some sort when using vacuum, as there isn't a lot to resist the part slipping a bit.

I have a few spare vacuum pumps from my composites business. Depending on how much horsepower is needed, I could donate one to my CNC project.

In general, I am not looking to extend the project length with additional projects on top of projects but.... I do still need to find a chip clearing solution and I was thinking of using one of my vacuum pumps for that. One of my spare pumps is an old 3/4hp Thomas oil free pump and compressor in one. I was toying with the idea of using the vacuum outlet to hold work and the compressor exhaust to blow chips away from the cutting bit and maybe being part of the cooling solution too.

I am just not sure I want to rely on my vacuum pump to hold work in place on it's own. It sounds like a dangerous accident waiting to happen. I once made the mistake of not clamping a piece of aluminum securely when cutting it with an angle grinder. It's a mistake I only needed to make once. As soon as the cutting wheel touched the metal, it launched the 15lb slab into my balls at high speed. To say it hurt a little would be like saying Hitler was a bit of a nazi.

I think I need to research more on how vacuum work holding works. I was imagining something like those vacuum forming tables with a bunch of holes to suck the work down. I am sure there must be more to it...

[Goemon]

Obviously wood is out of the question if you intend to mill aluminum

Steel isn't a bad idea, but sized for a machine this large will be extremely heavy and hard to handle. You would need a plate at least a half inch thick so using that and the projected table size you can calculate the weight. Also a steel plate might not be as flat as you would like and frankly you need to factor in blanched grinding the plate as a minimal amount of work required to implement. On the flip side you can drill and tap a steel plate and not have to worry about thread inserts as you would for an Aluminum plate.

Aluminum tooling plate is not cheap, that is a huge factor right there, plus you need to consider thread inserts for most of the threaded holes you want to use in the plate. On the other hand tooling plate if very flat (relatively) to begin with. Tooling plate is probably the best solution for a IDY project that wants good accuracy with a minimal of equipment or third party help, to pull off a precision table.

As far as aluminum extrusions go, there are extrusions made to implement machine tables with. One example: Techno Aluminum Extrusion Table Plates - perfect for work stations and automated applications requiring aluminum extrusions, t-slotted table plates. but note that these requires a substantial frame underneath. The heavy duty extrusions are only 20 mm thick over all, which frankly isn't much on a large table, especially when you consider most the extrusion is only about 8mm thick. If you did go the extrusion route you would want something fairly substantial as the common T-Slotted structural extrusions are just too thin in the webs, in my opinion.

Personally I'd go with a steel or aluminum plate mostly because you seem to know exactly what you will be using the machine for and have high expectations for performance. Just be aware that such a plate either has to be rather thick or well supported. On a moving gantry machine it is fairly easy to put support under a table so in your case you likely can get by with a thinner table. On the other hand you do have the composites experience many of use envy and thus might be able to produce a viable composite table. I would imagine thought that you would need a large flat table to begin with so that might be a problem.

If you did go the composites route that would allow you to design in all sorts of clamping options. Threaded inserts would be easy, you could also do steel T-Slots, though you may have to have the steel pieces custom made. You could also embed keyhole type slots. Plan ahead and you could have airlines embedded in the table itself. For coolant drainage you can mold in channels to guide the coolant ways from the table top. Obviously a composite lay up offers you plenty of possibilities that would likely require a cast table in the past or a lot of expensive machining time.

I have been having some of these thoughts along the way. It's good to be able to talk it through. I've been going round in circles in my approach...


I originally started by looking for a steel or iron table for all the reasons you stated and based on the good advice I got here. It was quickly apparent that the price and weight goes up considerably once you look for something with 30" or more of space. The other thing that came up was this point about steel not being a good option for vibration dampening. This got me looking at granite surface plates but I got backache just looking at the specs and it presented a problem of how you attach clamps and headstocks etc. I have no way of moving around a 450lb granite slab....


Anyway... I started (and am now far down the road of) making an epoxy granite frame. This solved the issues of cost and weight. Epoxy granite is super heavy but I am casting my frame in the area I plan on using it. I also used carbon fiber so the weight is reduced enough that I could move it (slowly) if I ever need to. The epoxy granite frame provides the solid base and a perfectly flat mounting surface. The top layer is made with self leveling resin so it is mirror flat and smooth without any additional work.

This still leaves the need for a solid table surface with the ability to mount work and head stocks etc. I could easily embed some flat tooling steel bars below the surface of an epoxy granite table. I could also do the same with aluminum extrusions or even a few smaller steel t-slot sections.

The point you made about the stability of screw threads in aluminum is part of what prompted this thread. I am worried that after all the work that I put into making the epoxy granite base and carbon fiber gantry, a weak screw thread connection for holding the work might negate all the accuracy gains. I am assuming that inadequate work clamping when cutting metal is as bad as flexing in the frame or gantry.

I have bought aluminum extrusions from a few different vendors and there is a world of difference between the best and worse as you said. The ones from OpenBuilds are complete garbage and I decided to use them to build a new curing oven instead of anything CNC related. I have some others from different vendors that are pretty solid but still not like quality steel.

I have also had some T6 aluminum that was noticeably stronger and stiffer than some of the worst steels I have bought. It's hard to know what is best. Is 1/4" or 1/2" of steel really better than 1" thick bars of T6 7075 aluminum?

Instead of choosing one of the options you laid out, maybe I could use all of them together. I have seen people embed steel t-slot tracks in epoxy granite tables. I could embed steel plates, T-slot tracks and some aluminum extrusions in an epoxy granite base with a carbon fiber surface plate / table (as it is easier for me to achieve a perfectly flat surface with resin or carbon fiber). This would give me a few different mounting options.

Carbon fiber is great for making strong and stiff structures but it is still not the right material for holding screw threads. Even if I made some carbon fiber clamps (which would be easy enough), I would still need to add some metal to hold screw threads. It occurred to me that if I manually add a bunch of threaded inserts then I will likely have alignment issues. The obvious benefit of t-slot extrusions is that they provide ready made perfect alignment if mounted on a level surface. They are also the perfect shape for creating a mechanical lock in the resin.

It's easy to find decent and low cost 36" aluminum T-slot extrusion that are 1" x 3" or 1.5" x 3.5" etc. I haven't found any steel t-slot extrusions. Just complete steel t-slot tables but nothing less than $800 with 36" of space. Then I am back to weight and vibration issues...

You mentioned some vendors i should check out for high quality aluminum t-slot table components. Do you know of any quality steel t-slot tracks that are relatively affordable?

Also, if I use steel or aluminum tables components, do I lose the vibration dampening properties of the epoxy granite frame?

[wizard]

A couple of things too consider:

Screw holding in Aluminum varies widely with the alloy, its temper and any anodizing that may have taken place. Also if the bolt is properly sized (length or thread engagement) you usually do not strip it out on the first installation. Aluminum is far more likely to strip out where the bolting is frequently used. So you can get away with bolted up structural parts that are seldom disassembled. It is an entirely different story where parts will be constantly bolted in place.

In aluminum this is where thread inserts come into play. There are many types including Heli-Coils and Time-Serts but even these give up the ghost after a bit as they are still screwed into aluminum. To be fair i need to point out that threads don't last forever in mild steel or cast iron either and one can end up using thread inserts there. The point is Aluminum is notorious for having the threads pull out in short order.

So considering the above it is pretty hard to OK the use of Aluminum for thread inserts in a cast or molded structure. In fact i strongly suggest that you don't use Aluminum. Most of the steels out there will hold threads much better. The only problem with steel is that it usually requires some processing to flatten if used in long sections. Cast in place round inserts of course require less effort.

[wizard]

I forgot about the steel T-slot material for insertion into a casting. I don't know of anything that would replace an aluminum extrusion and give you machine tool like T-Slots. That doesn't mean the don't exist though.

In any event i thought i might mention some other ideas that are worth considering.

Instead of trying to build your own machine base consider the possibility of a commercial machine base. Here I'm thinking manufactures like InterLakes and American Precision Grinding. A machine base can solve lots of problem for a person building without access to a well equipped machine shop. They are ready to go being welded and ground flat. In other words a good portion of your fabrication is done for you. Find a used one and you might be very cost effective.

Another possibility is to find a cast iron machine tool pallet or table to use in a moving table design. These can be had with T-slots, hole arrays or both. Again used might save you money.

The major problem with the above items is the weight which can be difficult to handle in a small shop. However weight is generally an advantage in a machine tool. In any event if you expect to grow your business handling heavy stuff will have to be tackled sometime.

In any event if you want to look for ideas, search for machine tool fixturing items, tombstones, pallets and metrology hardware. There is likely something out there off the shelf that might work for you. And probably work for you with less grief than a DIY base.

[Goemon]

I forgot about the steel T-slot material for insertion into a casting. I don't know of anything that would replace an aluminum extrusion and give you machine tool like T-Slots. That doesn't mean the don't exist though.

In any event i thought i might mention some other ideas that are worth considering.

Instead of trying to build your own machine base consider the possibility of a commercial machine base. Here I'm thinking manufactures like InterLakes and American Precision Grinding. A machine base can solve lots of problem for a person building without access to a well equipped machine shop. They are ready to go being welded and ground flat. In other words a good portion of your fabrication is done for you. Find a used one and you might be very cost effective.

Another possibility is to find a cast iron machine tool pallet or table to use in a moving table design. These can be had with T-slots, hole arrays or both. Again used might save you money.

The major problem with the above items is the weight which can be difficult to handle in a small shop. However weight is generally an advantage in a machine tool. In any event if you expect to grow your business handling heavy stuff will have to be tackled sometime.

In any event if you want to look for ideas, search for machine tool fixturing items, tombstones, pallets and metrology hardware. There is likely something out there off the shelf that might work for you. And probably work for you with less grief than a DIY base.

I am already too far down the road of building my own machine base to switch now. I have already cast the two risers for the x-axis and two of the six layers for the base plate (which connects the two risers). I looked into buying instead of building the base but I didn't have the budget for something that was better or even comparable to what I can make myself. I would have bought everything if I had the budget.

The biggest issue with buying a base is (as you said) the weight. I actually found some sweet deals on some awesome granite surface plates with T-slots already built in but, by the time I added in the freight costs, it became apparent why the price was so low. Plus, even with a lift gate, I have no realistic way of moving it to my work shop and lifting it onto a stand etc. just the plates were 450 - 600lb. I have already had back surgery. I don't want to go through that again....

I also found companies that make and sell ready made epoxy granite machine bases. None of there were affordable (for me) and, judging by the stated materials they used, none would have been as strong as what I am building for myself. I.e. I am adding premium materials to make it fit my needs better. Also, weight became the problem again because, just like the real granite surface plates, there is still a 500lb block of something to move from a truck to my work shop.

I added alumina trihydrate (flame retardant), carbon fiber's, fiberglass, carbon nanotubes, titanium powder and synthetic diamond powder (surface hardness) to my epoxy granite mix (which was epoxy and sand). The epoxy granite mix is cast around a steel rectangle tubes frame. The net result is that I will get the same strength from approx half the weight. It will still be heavy, just a little more manageable for me. Based on the weight of what I have made so far, I estimate that my base will end up around 250lb without the table, gantry or electronics. It will all be one solid piece when it's finished.

None of this solves my table issue. Even if I use my machine base as a table, I still need to add metal of some kind to be able to clamp work to.

The smaller steel t-slot tables which are available used off eBay could be an option but the more I think about it, the more I think it will cause alignment issue. I would need to use two of them and rely on them being suitably identical and my ability to mount them perfectly.

I think this is one area where I might have to accept a compromise at least in the short term. If I use 3 aluminum extrusions, each 1" x 3" x 36" and embed them in the machine base, it will hopefully meet most of my needs. if I fortify the epoxy granite mix around it with extra carbon fiber then that would negate any loss of strength and stiffness over steel for the tables integrity.

There would still be a weakness where the work is screwed to the table with t-bolts. I don't have the experience yet to know if there is a risk of the work being ripped out by the cutting bit if the extrusions isn't strong enough and gets torn by the screw being pulled out.