Fobco 10/8 spindle

A company that I do some work for have a Fobco 10/8ths that has a damaged spindle. I have agreed to have a go at making a new one, so the question is what grade of steel to use. Ideally I would like to use something that would not require hardening / heat treating after I have finished machining. any suggestions would be greatly appreciated.

Regards.

David.

Edited By David Colwill on 16/06/2016 19:33:49

If you want tough and strong EN16T / 605M36T or EN19T / 790M40T are the obvious candidates. About as far as you can go up the tensile range and natural surface hardness in reasonably readily obtainable steels before they become unreasonably hard to machine with the level of equipment likely to be found in the home workshop. HSS tools will handle the cutting if kept sharp and speed not too ambitious. You will need something a bit huskier than a Myford or Boxford tho'. If you do go carbide and have the speed to hit the tooling sweet spot the finish can be awesome straight off the tool. If you are going carbide and the diameter is below 65 mm 790M40 can be found in U, the next higher tensile range.

Not sure how well quality is controlled for short length suppliers. I'm darn sure my last bit of EN16T was higher tensile range although there is considerable overlap, top of T is near middle of U. 20 mm going down to 16 mm Ø, not all at once, tooling chattered like mad even with a travelling steady.

Don't know if you need anything that strong. The No 3 Morse taper on my Fred'k Pollard 15AY drill was so abused that I had to ream it out. Reamer ended up going in around 1/8" to clear all the damage. Wasn't unreasonably difficult. I'd be unsurprised if the tensile range was in high R territory. Much, much, easier to machine than T. Mr Pollard made a good drill so I'd trust his material chices.

Clive.

Edited By Clive Foster on 16/06/2016 20:21:45

Hi thanks Clive. I have a Dean Smith and Grace 13 x 30 so huskiness shouldn't be a problem. The owners of the machine buy quite a high volume of steel from a local stockist so they shouldn't have too much problem getting what I ask for. The diameter of the spindle is about 50mm at its largest point but that is only the last 20mm or so after that it reduces to about 40mm for another 200mm and then down to a splined shaft about 20mm that is abour 200mm long. This is from memory as I haven't collected it yet.

I will upload a photo when I've got it.

Regards.

David.

hey there, I don't know what your local equivalent would be but 4140 would be ideal for the shaft.

cheers

Dean

Dean

SAE 1440 is for all practical purposes same composition as EN19 / 790M40. Not sure about the condition or tensile range its normally supplied in. My guess from what I see on US based forums is that its normally supplied a little bit lower tensile range than T for easier machining.

Clive.

Oops. Previous post should read SAE 4140 is for practical purposes same composition as EN19 / 790M40.

Apologies for transposing digits.

Clive.

Thanks Dean / Clive . It's useful to know that 4140 is EN19 as it gets mentioned a lot on various forums / youtube.

It seems that the steel stockholder doesn't keep it in but they will get a bar for us. I will keep you informed of price.

David.

David

According to my book the ruling section (diameter) for T condition in EN16 is 63 mm (metricated 2 1/2 inches) whilst that for EN19 is 100 mm. So for your job either will do just fine as the physical properties of the finished spindle will be the same.

Interestingly an internet search suggests that 4140 is specified as being a little softer than EN16T or EN19T. Brinell 200 as opposed to brinell 250-300 which may make it easier to machine.

If its a special order material I'd be inclined to look for inclusion modified EN16T / 605M36 as that is said to be easier to machine. Not that I've ever found any to compare! Apart from ruling section about the only thing against EN16 relative to EN19 is greater susceptibility to low temperature brittleness. Generally considered not safe below -20°C which is unlikely to concern you.

Whilst we are on the subject my book has a warning concerning EN24 / 817M40 which is quite commonly offered. Usually more expensive than EN16 / EN19 due to being a more sophisticated alloy and so often considered all round better. Big advantage with this steel is that it can go up to the higher tensile ranges W, X and Z in useful sizes, inch plus diameter, with fairly simple heat treatment. Big disadvantge is that its quite sensitive to proper technique when heat treating otherwise it becomes brittle and prone to fatigue failure whatever the tensile range. I wouldn't get it from anything other than a known reliable source with certificates. As a general rule it should be OK in ordinary range jobs that folk like us will see but fatigue is such a difficult thing to get a proper handle on I'd prefer to avoid any risk.

Anything needing more than T range needs a much better engineer than I on the design side!

Clive.

That is good because I know that they keep EN16T in stock, which should make it a lot cheaper. I am waiting for the spindle to come back from the "precision engineers" ( the ones who looked at it and tut tutted before saying no thank you ).

I should point out how this has failed, which is a guess as the culprit has vanished. It looks as if someone has been drilling something on the slowest speed with a big drill that has snagged and spun the work round until it has hit something and suddenly come to a dead stop. This has twisted the splined section into a bit of a mess.

My main worries are internal stresses causing bending and a repeat of the previous failure but under less load.

I'm hoping to have the spindle on Monday so I will upload a photo then.

Thanks again.

David.

Looks like you have it al well in hand.

I believe Tony Griffiths **LINK** holds the remaining stock of ex-factory Fobco spare parts. I presume he has been asked about a new spindle and is unable to supply.

Clive

Hi Clive,

I emailed him previously and he did not respond. He has a page with all the spares on but there are no spindles.

Regards.

David.

4140 machines quite well, used quite a bit on highly stressed parts of agricultural machinery, normal advise is, not suitable for welding without heat treatment, but we have welded with no adverse affect, other parts get bent before the 4140 shaft breaks. We buy in the axels for the wheels, they are also 4140, and welded to the main cross beam. This thing is for feeding out large hay bales Ian S C

I have rung him previously about the larger fobco's and he has no stock of anything

David

Did you ever get this made?

Yes I did and it is still going strong

Machining the EN16T was much easier than I thought.

All in all it took way longer than I thought but I was pleased with the end result.

David.

Being able to take time is the advantage of the home machinist, or what kills these jobs in a commercial shop where time is money.

Ian S C