What product to use

I need to attach a piece of 3mm steel plate onto an uneven cast iron surface to form a 'sliding' surface.

You will see from the photo that there is a raised machined circular surface in the centre of the area of interest. My plan is to lay the plate underside to this machined surface, with the surrounding (rough) area of plate bedded onto some kind of hard filler material for support. I had intended to use metal putty but the 5 minute hardening time and quite firm consistency has given me concerns; I don't think I could bed it to the flat 'reference' surface quickly enough, if at all.

Can anyone out there suggest an alternative 'bedding' substance? Would car body filler be hard enough? Before anyone suggests it, machining flat is NOT an option

TIA

Alan

It depends what the forces are going to be and also any hazards resulting from failure.

However, lacking that information I would say that cellulose putty isn't suitable, polyester resin putty such as Isopon might do but I would go for a stronger solution and use a liquid epoxy resin mixed with a high density filler. West System epoxy has a good reputation and is used in boat building to seat deck fittings. See here

If the lateral forces are too great for that (unlikely) you could drill and tap the casting and fit a numbet of countersunk screws.

Russell

Thanks Russell. The flat 'sliding' surface will carry a cluster of pulleys mounted on a rectangular plate, so the forces are fore-and-aft with the plate held near each end by studs/nuts (the photo shows the holes for these already drilled and tapped). The forces from each direction should more or less balance when belts are tensioned. I did consider at one time using epoxy resin with a filler of cast iron filings, pretty much a hard version of the resin + microballoons used for filling and contouring on model aircraft. Drilling and tapping would not achieve the support I am looking for in the gap between the plate and cast iron.

Alan

Hardening times for metal loaded fillers seem to be very variable between brands. My last lot of RS Components own brand was nicely workable for approaching half an hour at workshop temperatures and shiftable for maybe as long again but such late movement would pretty much destroy the bond. Held well enough in a rather similar fill the gaps under a plate application. However there were tapped holes into the parent material so the device sitting on the plate could be fixed down so it was primarily acting as filler rather than adhesive. Stuck well enough to cope with normal shop handing when mounting and demounting devices tho'.

JB Weld seems up to the job and takes rather longer to set. When I tried it maybe 10 hours to firm and 24 to hard. I found it much runnier than the metal loaded filler. Gets thinner during initial setting phase. First time I used it I had to quickly push back in place and improvise dams when it started flowing out after an hour or so. Got away with it. Similar fill the gaps to support a plate job.

Clive

Thanks Clive, that sounds more useable than the normal DIY shed products. The obsession for everything working 'rapid' is not always an advantage; can't seem to get 24 hour epoxy any more either, it is all five or thirty minute stuff.

Alan

Hi Alan,

In the offshore oil and gas industry, Belzona was used to repair corroded / eroded flange faces and large pitting in pressure vessel internal surfaces. It can to be machined using a flange re-facer to give the correct flange surface. Very hard once set. Belzona is a Lloyds and HSE approved for these type of repairs. You may find something here.**LINK**

Cheers the Noo

John

Hi Alan,

Suggest you try SCK resin.It is made for machine tool building.There is a low friction type and a levelling type.

This type is used to align milling machine columns onto the base. I have used both types.

It is a German product, the UK agent is:

M. Buttkertteit Ltd.

Unit 2. Britannia Road.

Sale. Cheshire. M33 2AD 0162 9695418

It`s available in small quantities from 0.5 litre upwards

Regards,

John Feeney

The phone number for M Buttkereit in Sale is 0161 969 5418

Or make your own bedding compound.

**LINK**

I still use the VDF lathe in the picture No problems at all.

Regards
John

John Slaven,

Belzona 1111 (Supermetal) sounds as though it would be perfect for what I am intending, judging from the video on Youtube. The down side is that it is intended for industrial use in industrial quantities (1kg minimum pack size) and horrendous prices. A pity because it looks perfect and easy to handle.

John Feeney

SCK resin may also be suitable but, again, aimed at industrial applications.

Thanks both for taking the trouble to respond.

Because JB Weld is apparently available in Halfords, I may have a look tomorrow. A pack of that to experiment with won't break the bank.

Thanks folks,

Alan

I've had good results with Chemical Metal, which can also be got from Halfords in a tin or a tube.

I DON'T suggest using it for repairing suspension parts, as show at the above link.

Martin.

John McNamara,

That is very interesting. A search on line shows that I can buy 250g of 2.8g/cc iron powder for £2.50. That should be ample for the small gap I want to fill. Thanks.

Alan

Martin,

I'll have a look but that sounds like standard body filler. Thanks for the suggestion.

All,

Having looked again, JB Weld is not off-the-shelf at Halfords but only available by on-line purchase. I think I'll try John McNamara's method but just using cast iron powder and standard (24 hour) Araldite, if I can find anywhere locally that still sells it.

Thanks all for your very welcome input.

Alan

If it's any help 24hr Araldite is shown on the Halfords website at £5.50 and my local branch still has it in stock. Well it did no more than 2 weeks ago when I last bought some.

Phil

No, not body filler. Much tougher.

As I understand it loctite chemical metal is in the same group of products as metalised epoxy body fillers like Dinitrol 6030. These metalised fillers are sold as being tougher than the common versions, like Isopon P38, and essentially impervious to moisture absorption. Bit naughty to call them epoxy fillers tho' as they are still polyester type products and not fundamentally dissimilar. Epoxy as in real 24 hour Araldite being something different.

Going by price alone it looks as if Chemical Metal is a step up in performance and hardness from the metalised fillers but not as hard or as strong as the true industrial strength metal loaded fillers. Hardness is probably similar to or a bit below JB Weld but its only around half the tensile strength. JB Weld will also stand approaching double the heat soak temperature, 260°C compared to about 160°C. Frankly the heat soak capability is pretty much mostly what you are paying for with JB Weld so its arguable whether its worth it for normal temperature jobs. I bought it for the last couple of jobs primarily for the small quantity. Getting fed up with having half or three quarters of a pot hanging around for years and wondering if its still good when finally coming to use it.

When looking for this sort of mix-it-up miracle product it's well worth hunting around for official data sheet information. Easy to end up paying for performance you don't need. More expensive isn't always more better for your job. Wide variation in performance and, once beyond the economy range, most of the variation tends to be loose on the swings, gain on the roundabouts type. Better in one area usually being compensated by worse in another. Tedious but better than a do-over if you got the wrong breed. Even if the wrong stuff failed its still a total pain to get off for are try. Been there!

Clive.

Edited By Clive Foster on 13/08/2017 17:52:03

Edited By Clive Foster on 13/08/2017 17:53:00

Edited By Clive Foster on 13/08/2017 17:53:41

Hi AlanW,

I do recall you mentioned you could not machine the top flat. OK, but just food for thought - could you add three drilled and tapped holes in the top surface? If so, you could add three threaded bronze studs with a spherical or rounded end. They could be adjusted for height and nutted on top or maybe underneath to secure them at their correct heights. Your 3 mm plate would run nicely on the bronze pieces. Good luck, JD

Clive,

I just ned a gap filler/adhesive that will resist compression and posess a reasonable degree of oil resistance. It also needs to be fairly cheap and readily available in small quantities, something that I didn't specify in my OP. I've had the metaphorical tears in my eyes as I drop 90% of an expensive but out-of-date product into the bin.

Jeff,

An interesting idea but the 3mm plate is purely to provide a flat surface on which a pulley bracket will slide.There is no need for it to be low friction.

Thanks both.

I've ordered some iron powder and bought 'standard' araldite 24 hour (from Halfords. Supermarkets and DIY sheds only sell 'rapid'. I'll do a couple of trial mixes to see how it handles before committing to the job. In my experience, the slow setting Araldite is more fluid than rapid so I hope to be able to use more filler material without the mix being too stiff to squeeze down.

Alan

Hi Alan

When you mix it may take a fair amount of mixing for the Araldite to wet the iron powder, at the start the mix may appear dry, I did not use iron powder alone so maybe your results will be different. As a starting point I would suggest 10% by volume of adhesive. You can adjust it from there.

You will find the mix will run. you may need to build up a dam around the area you are working on, Plasticine will do or whatever you have to hand.

The commercial machine builders that use Epoxy and aggregate try to use less than 10% to reduce the flexibility of the castings, castings that can weigh several thousand holograms. **LINK** There is a lot of work being done in this area, both commercially and by individual experimenters.

Regards
John

Edited By John McNamara on 15/08/2017 13:52:54

Hello John,

The supplier I ordered the iron powder from has excelled, as has the postal system (for once). The powder arrived this morning and I couldn't wait long before experimenting. After thoroughly mixing the epoxy, I added powder and continued to 'mix' until it became shiny again. The mixture seemed quite workable, so I spread some onto scrap steel and pressed a piece of 2.5mm plate onto it leaving approximately 3mm in the sandwich. It slumped fairly quickly, so I scraped it all off back into the pot and added more powder; too much this time because I couldn't achieve 'shiny'. Anyway, I remade the sandwich and have left it to cure. I was quite surprised how easily the quite stiff mix with too much powder squashed down. I'll see what it is like tomorrow but there was no sign of slumping after 10 minutes. I suppose I should add powder in smaller quantities at a time, given that I have plenty of working time.

Thanks for reminding me of the value of Plasticine as a dam. I was wondering what I could use that wouldn't become permanently attached!

I'll report back on the first test and the final job, if successful.

Alan