Type of cast iron and weldability on Swiss machines

[Adam HarrisParticipant @adamharris13683]

My project is to fit an Aciera F4 slotting head to a Mikron WF2 mill. I have cut off the F4 dovetail support arm and need to mount in its place a cylindrical support arm. The F4 arm is of a lattice construction (ie it is cast with weight-saving pockets) so my plan is essentially to weld a plate (275 or 355 steel) onto the stub of the F4 arm and then weld a 355 steel cylinder onto the plate. My concern is the weldability of the F4 arm cast iron because the person doing the welding is an expert at welding 275 and 355 construction steels ( RSJ’s etc) but not so much cast iron. He has laid down a trial bead of weld on the scrap piece of the arm and it looks ok but of course no way to test how strong the weld really is. Can anyone tell me or speculate on the type of cast iron the Aciera F4 arm is and its weldability in order to match the appropriate welding technique/rod to make this a good weld? In particular, quality swiss machines all seem to have castings that are immune to rust which might point to a particular type of iron used. On cutting the arm off with an industrial power band saw it cut well with plenty of suds and produced a fine black powder typical of cast iron machining.

[Adam HarrisParticipant @adamharris13683]

[Adam HarrisParticipant @adamharris13683]

[Adam HarrisParticipant @adamharris13683]

FYI both the WF2 horizontal milling support arm and the slotting head have a 62mm diameter solid cylinder that slides into a socket on the face of the WF2. At the end of this socket is a drive dog that drives the vertical milling head (which has a hollow 62mm diameter cylinder within which is a shaft connecting to the vertical spindle via bevel gears)

[duncan webster 1Participant @duncanwebster1]

The only time I’ve had anything to do with cast iron welding we were advised to use nickel rods and preheat. The rods turned out to be so expensive it would have been cheaper to go to a specialist. We had to buy a full box and only used a few. It was entirely successful

[DC31kParticipant @dc31k]

I would be shaping some steel to fit reasonably into the lattice holes, gluing it in with the very best metallized epoxy I could buy (JB Weld plus) so the entire space is filled and attaching my steel plate to that. You could drill and tap sideways into the infill plugs if you were not confident of the epoxy joint. With countersunk fasteners, some filler over the heads would resore the original casting shape and make it look as if nothing had happened.

[Adam HarrisParticipant @adamharris13683]

Thanks Duncan. When he is welding RSJ’s all day long he is using some type of auto fed spool wire, I don’t think he is using the old fashioned rods or sticks. I’ll check. A new nickel wire spool sounds very expensive for a job that requires a total length of say 30 cm of bead. I have read that there are variety of cast iron types of which most can be welded with the exception of White Cast Iron – how do i know what type i have? Could it be White?

[Adam HarrisParticipant @adamharris13683]

Thanks DC but how to “attach” the steel plate to the filled stub? The weight of the slotting head is about 35 kgs and needs to be absolutely rigid – albeit there are going to be 3x M12 bolts assisting mounting to the face of the WF2 , the cylindrical arm is the main support. Also I need to machine the fixed plate perfectly flat before mounting the cylinder to the plate, and when welding the cylinder to the plate won’t the heat impact the epoxy underneath the plate?

 

[bernard towersParticipant @bernardtowers37738]

Most Mikron machines werte made from a special grade of cast iron that resists rust. Most of their hobbing machines were supplied with no paint!!!

[Adam Harris]

On Adam Harris Said:

Thanks DC but how to “attach” the steel plate to the filled stub?

Fabricate, stress relieve and machine true every piece of steel that is going to be attached to the cast iron (hole-filling stubs, flat plate, cylinder). Machine the back of the cast iron level and true. Squirt some glue into the holes. Plunge in the fabricated component and clamp together. You will need some kind of fixture/jig/scaffolding to assure left/right and up/down alignment.

Once the glue has set, the two lattice holes will be solidly filled (no air space). As above, drill though horizontally or from the front and put in some bolts or fitted pins with loctite to make sure nothing moves.

The difficulty with welding onto the cast iron piece that you have is that the heat may distort it and you have no excess material to true it back up again.

Edit: confidence bolts could go where the six red lines are.

[duncan webster 1Participant @duncanwebster1]

White cast iron is very hard, and looks white rather than grey

[Adam HarrisParticipant @adamharris13683]

Thanks Duncan that is good to know it is not the unweldable White type – so this grade of cast iron is definitely weldable just need to find the best composition of wire/stick…

[Adam HarrisParticipant @adamharris13683]

DC I can’t put screws or dowel pins into the plate through from the reverse (front) side as that is where the circular T slot lies and I don’t want to interfere with the nice sliding action of the beautifully profiled T nuts. Are you thinking the cylinder should be welded to the plate before assembly and fixing the plate to the filled stub with screws?

[Adam HarrisParticipant @adamharris13683]

DC it could be a possibility if I used some 10mm angle steel I have as the plate, with the perpendicular side lying against the underside of the stub, thereby directly assisting support of the weight of the slotting head, and then I could also screw through that underside part of the angle plate into the (under)side of the filled stub…

[Ian PParticipant @ianp]

Not sure if the following is relevant because I have no idea of the sizes and proportions of the parts involved. AIUI you want to weld a plate to the sawn off mounting/revolving end of the overarm and then weld to that a ‘cylinder’ which I presume is a thick walled tube (which is then the new overarm).

Given the difficulty of welding dissimilar metals and risk of distortion of the cast iron end plate would it not be easier to make a new steel endplate with an integral stub (or socket) that the tube can be shrunk or press fitted?

Practicality depends on what resources you have.

Ian P

 

 

 

 

 

[Adam HarrisParticipant @adamharris13683]

Thanks Ian, yes well I think I am coming around to avoiding welding anything directly to the cast iron because I really cannot risk any distortion or fractures to the casting. I have been reading that JB Weld is impressive for resisting pull out when tapped and screwed. I might get the cylinder welded to the plate if I can be sure both are the same grade. A potential issue with press fitting the cylinder into a bored out plate would be how thick the plate needs to be to hold the cylinder rigid…For a 62mm diameter cylinder 150mm long , do you think 10mm plate is appropriate?

[Adam HarrisParticipant @adamharris13683]

At least welding the cylinder to the plate with a jig can ensure perpendicularity, but press fitting while easier for me  possibly gives a less reliable outcome

[Adam HarrisParticipant @adamharris13683]

I’ve press fitted gears onto shafts and bearings onto shafts, but actually have never checked for perpendicularity afterwards…

[noel shelleyParticipant @noelshelley55608]

If welding then Murex Cinex would be the rod to look for ! BUT VERY expensive. Noel.

[Adam HarrisParticipant @adamharris13683]

Thanks Noel. I am now moving down the non-welding route and I think I will indeed press fit the cylinder into some steel angle plate and screw the plate onto the F4 arm stub. Just wondering if my 10mm angle plate is thick enough or I need to buy some thicker if  I can…..

[JasonBModerator @jasonb]

Why not get your mate to weld the cylinder and angle after pressing, adding a couple of webs if needed then mill the face of the angle true to the cylinder and bolt it to casting.

[Adam Harris]

On Adam Harris Said:

DC I can’t put screws or dowel pins into the plate through from the reverse (front) side as that is where the circular T slot lies

I edited my post to add a photo, possibly after you read it, but this morning the photo has disappeared.

You can avoid bolting from the front. The only place you would drill for bolts (or pins) would be in a part of the cast item that is currently painted grey. For each half, one bolt in the underside; one bolt on the sloping side and one bolt on the (less sloping) top.

For the steel stubs that go into the casting lattice holes, I would aim for a nominal 2mm clearance on all five sides and maybe look for a fluid epoxy that I could inject once the two parts are assembled and aligned.

As above, drilled and reamed holes with mild steel pins loctited in and then the surface filed flush with the casting  would look tidy. Using pins would also expand your positioning options – with bolts coming in from three directions, you have to make sure they do not clash and that ther eis a minimum distance between the female threads.

Perhaps as a modification to the angle you suggest, mill a small flat on the underside that is perpendicular to the sawn face. Then make a step on the welded fabrication. The casting would sit on that step. That would also greatly assist alignment (reduce your fixturing requirements) as it stops the assembly trying to rotate.

[Michael GilliganParticipant @michaelgilligan61133]

Not trying to be funny … this is serious: The scheme suggested by DC31k looks practical, and reminds me of good Carpentry technique.

Careful choice of the pin locations and angles could make for a very effective fixing.

MichaelG.

.

Rabbit hole for exploration:

https://www.medieval-carpentry.org.uk/S_to_Z.html

 

 

[FulmenParticipant @fulmen]

I would not do this unless your welder has significant experience welding cast iron. It’s a complete pita to weld, brazing would be a lot safer.

[Adam HarrisParticipant @adamharris13683]

That rabbit hole is very interesting Michael. I am now wondering where I might squeeze in an under-squinted abutment!

[Author]

Posts