How to choose crankshaft regrind machine shop

[Pistom]

I'm looking to get a cranksahft reground from an old Triumph 6 cyl engine.

How do I go about finding one? What should I be looking for? I'm looking to get the work done around Preston, Bolton or Manchester.

I can measure the diameter of the finished journals but should I be looking for a particular finish? How do I measure this?

Is it worth getting it balanced - do they need the rest of the engine for this/

Many thanks.

[stevieturbo]

Pistom said:

I'm looking to get a cranksahft reground from an old Triumph 6 cyl engine.

How do I go about finding one? What should I be looking for? I'm looking to get the work done around Preston, Bolton or Manchester.

I can measure the diameter of the finished journals but should I be looking for a particular finish? How do I measure this?

Is it worth getting it balanced - do they need the rest of the engine for this/

Many thanks.

There is bound to be a few machine shops local to you.

How do you find one ? Yellow pages ?

Although I'd have thought that anyone able to strip and rebuild an engine, would already know of suitable machine shops in the area ?

If it is only a crank re-grind, there is no need to have the crank balanced.

[Pumaracing]

Eagerbeaver said:

Sorry, what I really meant is how to identify a good machine shop?

Short of taking your own micrometers along and checking out some cranks they've already ground for tolerance there really isn't one.

Eagerbeaver said:

I realise that a crank regrind doesn't need the crank balancing but I have had experience of a car that had the moving components balanced and the car revved so sweetly afterwards. It was very smooth.

So are we saying that I can trust the regrinding to any local engine machine shop and the finish is likely to be OK?

I was wondering if certain types of equipment would give a better finish.

It's probably not the finish you need to be worrying about, it's the size. I've had some pretty awful experiences with supposedly experienced crank grinders but never found one who couldn't at least produce an acceptable surface finish.

What you end up with as far as journal size and fillet radii are concerned is another story. One place did a crank that I'd only had ground because it was half a thou under limit (should have left it alone) and returned it nearly a thou under limit on the next size down. Turned out his micrometer was nearly a thou out of calibration - yes I do mean a whole thou not a tenth of a thou. I think he'd been using it as a G clamp not a measuring instrument. He was suitably embarrassed and got it right on the second try after I'd recalibrated his micrometer for him but by then he'd used up two undersizes on my crank.

Another place only set the machine datum on one of the main bearings and didn't bother to check that the crank was perfectly aligned in the machine or to even measure any of the other journals during or after grinding them. That resulted in each main bearing journal being a bit larger than the previous one because the crank was not properly aligned between centres. By the time I got to checking the fifth journal it was over half a thou larger than the first and I had to polish four journals down to the size of the first one in my own workshop. At least I had the equipment to do that but it's hardly fun.

Also what tolerance do they try and work to in the first place even if they could achieve it? A journal will have a listed size range of perhaps 3/4 of a thou specified in the bearing catalogue. Do they work to top limit, bottom limit or somewhere random in the middle? What are you going to ask them to do? Do you even know? Do you know what size in the tolerance range OE production cranks are usually ground to?

Whatever they tell you they do they'll say "well we never get no comebacks mate so it must be ok." Ignoring the seemingly compulsory double negative in such circles it's hardly a recommendation for expertise given that very few customers will have the equipment or knowledge to check what they've done and as long as the engine runs ok for long enough to get it out of the workshop the job's a good 'un and the crank grinder's shoddy workmanship will forever after go unnoticed. The engine might fail after 10,000 miles instead of 110,000 but that's unlikely to ever bounce back on the hapless crank grinder a year or more later.

My long and usually bitter experience of the reconditioning trade is most of them can't even spell enjinear properly never mind perform like one and you'll rarely find anything as good as OE production machining.

Edited by Pumaracing on Saturday 5th February 07:15

[westwood35]

Go to the Federation Of Engine Remanufacturers website, just put in your postcode and it will show the nearest member to you.

[The Black Flash]

I was recommended Lancaster Engines for some work, they actually specialise in triumphs and other classics.

Seemed a decent knowledgable chap and did a nice job honing my bores. They definately do cranks as he had some huge great straight 6 one on the grinder when I was in.

[taz turbo]

I and many others I know, have used Banister Engines in Bamber Bridge, quality work, but he can be very busy at times.

01772 338 970
Unit 1A
Hecla Works
Mounsey Road
Bamber Bridge
Preston
Lancashire
PR5 6LS.

Chris.

[porka911t]

This is the problem with all forums, you get some one ask a very sensible question and the answer should be:
google crankshaft regrind.

Good advice from some expert in that field. Not jack of all trades master of none.

6cylinder Triumph crankshafts are very basic to grind. Do your google search find your local Engine shop. They will probably have two types of grinder, Prince is very common. This machine has a grinding head that follows the big end journals. So if you have a reasonable crank it would be fine. But if any on your big end journals are very bad choose the off set grinder option. The off set grinder will guarantees the stroke is correct. Be sure to ask them to dress the radius on the grinding wheel after start up and balancing especially on the prince.
From memory the main journal sizes on most of the later Triumphs are 2.3110 to 2.3115 and they should be able to stay with in this easy.
If any journals are very bad change the con rod or the crank will certainly fail quickly.

Hope this is of help

Alan Page

[Pumaracing]

westwood35 said:

Go to the Federation Of Engine Remanufacturers website, just put in your postcode and it will show the nearest member to you.

The FER is something anyone who is prepared to pay the subscription for can join. They don't do quality checks. It means nothing.

[Eagerbeaver]

Thank you for all the answers. It's good of people to take the trouble to respond in a forum. Most of us are experts in something, very few in everything so it is good to share information.

I ended up going to Bannisters. As has been said, the old Triumph crank is a very basic crank but I was impressed with his knowledge of the known weak parts in this engine and his explanation over how he was going to do it.

Of the companies I called, he was the most expensive by far but we are still only talking £90 for the grinding and polishing which is over double the cheapest but I took a liking to the old chap (Bill) which added to the fact that he appeared to have good knowledge helped make the decision.

He made me laugh when I asked him why he was so expensive and he said "well, that's the price".

Many thanks to all who have contributed to this thread. I've learned something from this.

[philip2]

glad you found somewhere, but £90 is pretty much on the ball price wise, id be very suspect with the cheaper qoutes.

i pay £50-60 depending on what mood my machinist's in, but i know he charges £90 for a 4 pot crank but he grinds big ends and mains he never does just one or other.

[eliot]

Eagerbeaver said:

He made me laugh when I asked him why he was so expensive and he said "well, that's the price".

Sounds like my old man. People would call him up and ask "whats the ballancing factor for a Norton Crank?" his reply would be "fifty pounds", customer would say thats heavy - are you sure thats right? "Fifty Pounds cash.." would be the response.

[MrHooks]

Steve at Chase Engines had been grinding cranks for 30 years, starting out at Brunts Rolls Royce back in the day in Silverdale Stoke area. Re-chroming worn cranks and crack testing too

[stevieturbo]

MrHooks said:

Steve at Chase Engines had been grinding cranks for 30 years, starting out at Brunts Rolls Royce back in the day in Silverdale Stoke area. Re-chroming worn cranks and crack testing too

I'd hope that after asking 8 years ago, the OP got sorted....

[227bhp]

stevieturbo said:

MrHooks said:

Steve at Chase Engines had been grinding cranks for 30 years, starting out at Brunts Rolls Royce back in the day in Silverdale Stoke area. Re-chroming worn cranks and crack testing too

I'd hope that after asking 8 years ago, the OP got sorted....

I think he was just reminiscing, note the past tense.

[tapkaJohnD]

You have a grinder who you're happy with, great!

Bit further from you, but I've always used Lancaster Engines. I knew they were right the very first time I took a crank to them. Met the proprietor as I was carrying my crank, and the first thing he says is, "Oh, a Triumph crank! Not seen one of those for a while!" Never let me down.

John