Flattening Machine Tables

[Sawyer]

I have an Axminster WS1000TA spindle moulder on which the cast iron table is not flat: the middle around the spindle is about 2mm lower than the infeed and outfeed edges, making accuracy very difficult to achieve on many jobs. Front to back flatness seems alright; the problem is just along the length.

I've wondered about asking an engineering company about re-grinding, but imagine that even if I can find someone able to do it, the job would be expensive. Then it occurred to me that my hefty 4" belt sander may be able to tackle the job, at least well enough to make a worthwhile improvement. Apart from a few sanding belts and my time, I don't see that there is much to lose but at the same time realise that this may be a fanciful and impractical idea. :?:

Any thoughts? Has anybody else had to deal with the same problem? Would I be wasting my time trying?

 

[CHJ]

Removing metal particularly as much as 2mm from a casting may see it move again, not necessarily in the same direction.

How old is the casting?
How is it currently supported?

 

[bugbear]

I have an Axminster WS1000TA spindle moulder on which the cast iron table is not flat: the middle around the spindle is about 2mm lower than the infeed and outfeed edges, making accuracy very difficult to achieve on many jobs. Front to back flatness seems alright; the problem is just along the length.

I've wondered about asking an engineering company about re-grinding, but imagine that even if I can find someone able to do it, the job would be expensive. Then it occurred to me that my hefty 4" belt sander may be able to tackle the job, at least well enough to make a worthwhile improvement. Apart from a few sanding belts and my time, I don't see that there is much to lose but at the same time realise that this may be a fanciful and impractical idea. :?:

Any thoughts? Has anybody else had to deal with the same problem? Would I be wasting my time trying?

How would you control (accurately...) the sanding?

BugBear

 

[Peter Sefton]

Wow 2mm is a lot, not sure how old it is, have you contacted Axi?

Peter

 

[RobinBHM]

You are never going to remove that amount of material by sanding. I once flattened a multico surface planer bed with a belt sander, but that was half a mm and it took quire a few hours.

Sometimes how the cast iron top is bolted down can affect its flattness

Maybe you could make a false bed with a sheet of stainless steel on birch plywood, or a sheet of hard plastic like trespa. I realise its not that straightforward for setups that have the cutters only half above the bed.

 

[Sawyer]

The table is fixed by four bolts towards the corners. Around the centre/spindle hole is supported by fresh air, so maybe it's a consequence of design and the dead certainty that the Chinese factory will not have bothered letting the castings mature.

As an effective bodge, I have made a thin hardwood board, flat on top and scribed beneath to fill the concave profile of the table, which butts up to the fence. This works well, but is not suitable for all operations.

The machine was new in 2011, so I doubt if Axi will be too interested: all the same, there is nothing to be lost in contacting them about it. My next port of call, I think.

 

[shed9]

A good method in flattening cast iron is to use various grades of oil stone from very coarse down to very fine and lots of lubricant. You effectively load the stone and the table with lube and vigorously move the stone over the entire cast iron surface in a figure of eight (infinity) pattern. Move through the grits and check LOTS as you go.

This will be impractical to remove a 2mm difference but may work as a final solution after using more barbaric methods such as other sanding options. It's long, laborious and messy but it works.

A machine shop won't actually charge that much to skim the iron part of a WTS1000 table. I have that same machine so have some idea of the size. In reality it's probably about the same size as a large cylinder head and most shops are geared up to fly cut those for the petrol heads. Drop the dimensions to a shop and see what they say, however as others have pointed out this may take a few separate passes as the iron will relieve a tad more when taking that much material off. That said, it certainly won't move anywhere near another 2mm again.

 

[Cheshirechappie]

Assuming Axi can't do much beyond making sympathetic noises, and you don't want to scrap the machine, there is a possible home engineering solution.

Instead of using a power sander, use files. Not as hard as you might think, this - cast iron is relatively soft as metals go. It helps a lot to have files with a slight belly to their working face, so efforts can be concentrated on humps. Years ago, 'flat' files were so made, but no longer it seems, so use a large square or three-square file instead - the largest and coarsest you can find - something like 14" turnip cut. Check very carefully with a straightedge (as straight as you want the table to be flat) along, across and diagonally. Mark the high places. Attack with file, working slowly and methodically. Take your time, and check frequently with the straightedge. At first, the area filed will be quite small, but it will gradually become larger as you get nearer to flat. When it is flat to your satisfaction, turn to a smaller second cut, then smooth file and work over the whole surface, again checking all the time with the straightedge (and feeler gauges, now) again marking any high spots. (The professionals would be working to a surface plate, but decent straightedge should be fine for this job.) Then finish with abrasive papers to the surface smoothness you feel appropriate.

The key to this is being careful with the coarse file in the early stages. It's easy to over-do it locally, and give yourself far more work to bring the rest of the surface down.

Alternatively, fill the hollow with epoxy, and clap a false table on top of it.

 

[shed9]

Just to add to this Sawyer, I checked my table on my WTS1000 earlier and it is dead flat. I only point this out to note that it may not be a design issue and as such may not be problematic when you fix the problem - if that makes sense?

Either way, good luck.

 

[blackrodd]

Here's a pic of the top and it shows its thinner in the middle than the ends.
If it's possible and you can support the centre mass it will probably stay stable.
Failing another top available, it would probably be more efficient and easier to thicken the top with liquid metal and scrape it to an acceptable flatness.
HTH Regards Rodders

http://www.manualslib.com/manual/537003 ... =33#manual

 

[Rorschach]

What about building it up with moglice?

 

[LancsRick]

Why not get it milled? Assuming you have a contact with a suitable machine, it would be a straightforward job.

 

[ED65]

Various somebodies beat me to it but I was going to suggest with that much of a discrepancy it makes much more sense to fill the low point rather than remove tons of metal from around it. Use a decent filled epoxy and there's no reason you'd need to cap the table afterwards either, the epoxy will have at least as good wear resistance as the surrounding cast iron and more than likely it'll actually be harder.

 

[woodpig]

I'm surprised that a machine with a 2mm hollow in the table even made it out of the factory unless as someone said its part of the design. If it really is that defective it should have been sent back to Axminster. Even if you had a mate with a surface grinder big enough, taking 2mm off the whole face is a lot of metal and fraught with danger. As said, filling it with chemical metal would be a better idea but could end up lifting at the edges if you're unlucky causing feed problems. I'd like to see a picture of the fault with a straight edge across it.

 

[MusicMan]

As others have said, machining that much cast iron off could well cause distortion (including warpage) in a different direction. I agree with building it up with epoxy, which tends to be harder than low-liquefying-point metals.

You may find an epoxy fluid enough to self-level, if you get the top very carefully level before you pour.

Moglice is formulated for this, though might be costly in this amount, and not sure how it would cope with the featuring at the edge of the depression.

I'd try Ax first, if not for warranty for a good deal on a replacement top.

Keith

 

[shed9]

I've seen many people deal with cast surface defects by building up the dips as opposed to taking down the highs and I've yet to see a job well done that didn't end in regret and an eventual trip to a machine shop to sort it out. You will not get self leveling properties in a 2mm dip over that surface area, trust me, I've seen people try to do it. The result of that will require further works and will never sit right.

Machining may likely cause some deflection when relieved by grinding / cutting down, however you can build this into the price when you first get it done, i.e. arrange for a final skim in the future to deal with any warp. The part in question is easily removed and connected by four leveling threads and the slider does not connect to it. Assuming the dip is in the middle where the aperture is, you are looking at 2 areas of around 14" square either side of it and the casting is around 5.5mm thick in that area. My machine is from the same era so I suspect they are similar in design and spec.

I appreciate it is questionable to go down to 3+mm but you could skim and then load the underside of the table with a generous pouring of epoxy between the webbing. This will increase mass and strength and doesn't have to be pretty as you won't see it.

I agree with MusicMan's comment of getting a cheap replacement in lieu of warranty expectations may be a conversation worth having with Axi.

 

[Monkey Mark]

How about having the dip built up with a tig welder then skimmed flat?
I'm not sure if there would be too much heat involved?

Had you been closer I'd have put it on the miller at work.

 

[Sawyer]

Thank you everyone, for the helpful replies. It sounds as though the belt sander idea would not be a good use of my time or abrasives - rather as I'd suspected. I think I shall be putting Axi's much-vaunted customer service to the test, with getting a replacement table seeming to be the best idea, depending on price of course.