Author Topic: Surface grinder....  (Read 9629 times)

Offline AdeV

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Surface grinder....
« on: May 28, 2015, 11:25:04 AM »
I'm seriously considering buying a surface grinder; but it's not your usual type. I want it do to cylinder heads. It looks like this (sorry for the oversize image):



Are there any particular disadvantages to this sort of machine, rather than an overhead wheel grinder? The main problem I have is, resurfacing a Jaguar V12 head requires over 2ft of horizontal travel under the wheel, and most inexpensive surface grinders just don't have that sort of travel. Plus, there's no way to stick the aluminium heads to the magnetic chuck most seem to be fitted with...

Using the type pictured above appears to fix all of those issues. I can grind anything I like so long as it's no wider than about a 10-12" (the ring dia is 14"); I don't need a fixture to hold the head down (again, presumably, one uses hand pressure & simply keeps it moving). Problems I can foresee include uneven grinding due to varying pressure on the work piece and/or inconsistent feed rates.

Of course.... I could just go and buy this thing:



Hmmm....  :scratch:
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline vtsteam

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Re: Surface grinder....
« Reply #1 on: May 28, 2015, 11:40:44 AM »
This is total inexperience speaking with either of the two. But the ring  in the base style machine reminds me of a wood joiner, which I have used a lot. The hand pressure is usually not a big factor in depth of cut --  that's determined by the step in table height. If there's no step (looks that way in this case with a circular ring inset) I dunno. Best practice with a joiner is to reduce hand pressure as you get to the end of the cut to avoid rocking or bending and increasing the cut depth.

One nice feature is starting the cut by lowering the workpiece onto the joiner head just back of the forward end of the workpiece. This leaves a step and cuts a taper (useful if you need to even the thickness of a wedge shaped piece, or conversely, want to make a tapered piece). You repeat until just shy of the desired end thickness, and then join the full length to remove the step on the last cut.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

lordedmond

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Re: Surface grinder....
« Reply #2 on: May 28, 2015, 12:37:28 PM »
Ade

They had one of those in the fitting shop at the iron works , now I was a sparks there but dad was the Forman in the fitting shop ( that's why I was not a fitter) anyway it was considered a quick and dirty rough grinder to knock the lumps off, non of the fitters considered it as a presision tool it always seemed to round over the start of the cutt and wobble the rest .

When any one had a big cylinder to do ( plenty of home work was done ) it was the old flat belt planner , cars were done on a grinder or vertical mill ( I mean the ones that used a Bridgeport for a toothpick )

Sorry to be negative but you asked

Stuart

(sorry, hit wrong button -- now restored -- vt )
« Last Edit: May 28, 2015, 12:58:55 PM by vtsteam »

Offline AdeV

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Re: Surface grinder....
« Reply #3 on: May 28, 2015, 12:42:58 PM »
Ade

They had one of those in the fitting shop at the iron works , now I was a sparks there but dad was the Forman in the fitting shop ( that's why I was not a fitter) anyway it was considered a quick and dirty rough grinder to knock the lumps off, non of the fitters considered it as a presision tool it always seemed to round over the start of the cutt and wobble the rest .

When any one had a big cylinder to do ( plenty of home work was done ) it was the old flat belt planner , cars were done on a grinder or vertical mill ( I mean the ones that used a Bridgeport for a toothpick )

Sorry to be negative but you asked

Stuart

Stuart,

No problem, I'm glad you told me. I want to do precision race car heads, not "knock the lumps off"...

So, I should buy the bigger grinder at the bottom of my post then? The price is right (£1500), shame I'd need another £3k/year unit to put it in...  :bugeye:
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline vtsteam

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Re: Surface grinder....
« Reply #4 on: May 28, 2015, 01:01:39 PM »
it always seemed to round over the start of the cutt and wobble the rest .

Makes sense to me since there is no step -- the ground part could rock forward when half the weight was forward of the cutter.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline Meldonmech

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Re: Surface grinder....
« Reply #5 on: May 28, 2015, 01:15:59 PM »
 
  Hi Ade
                 I think you have made the right decision. That is a good price you have been quoted, giving you a machine that will do a professional job. Owning this machine, would also enable you to offer this service to other enthusiasts, which could offset the cost of the additional unit.

                                               Good Luck
                                                                    Cheers David


Offline Manxmodder

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Re: Surface grinder....
« Reply #6 on: May 28, 2015, 02:11:52 PM »
Ade,I have had quite a lot of experience with both types of grinder in your photos.

As someone else has already mentioned the push across table type does tend to create bows at the start and finish of the cut. We only ever used it for cast iron heads as aluminium just clogs the wheel up. It is also very slow and tedious to use.

The overhead Pratt & Whitney is very similar to the Churchill I have used,and this type of machine with segmented wheels does a great job of leveling and produces a superb finish if left to spark out on a light cut.

For aluminium heads we used to skim with a single point fly cutter on a swing arm type grinder with automatic feed......OZ.

Edit to add a video of a swing type grinder grinding an iron head with segmented wheel and flycutting with a single point tool


« Last Edit: May 28, 2015, 02:48:10 PM by Manxmodder »
Helixes aren't always downward spirals,sometimes they're screwed up

Offline DavidA

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Re: Surface grinder....
« Reply #7 on: May 28, 2015, 02:59:53 PM »
Just add my bit to the pile.

I also have considerable experience of the top (Snow) grinder and confirm that it is a rough fettling machine.  What tends to happen is that the wheel becomes distorted with use and has to be dressed fairly frequently. I used it for removing the 'skin' off cast iron samples.

I have also used the grinder (Lumsden version) depicted at the bottom.  We used it for skimming cylinder blocks after fitting new liners.

Dave.

Offline millwright

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Re: Surface grinder....
« Reply #8 on: May 28, 2015, 03:48:46 PM »
Can only agree with the others Ade. we had several snow grinders in the factory where i worked they were used for cleaning up the faces of flamecut plate up to 6 inches thick.
 I remember when i was an apprentice and was given the job of overhauling the engine of a non running ex RAF fork truck called an aerolift, trying to skim the old ford side valve head it bounced all over the table i couldnt hold it, it look a right pigs ear and i had to have some nice words with the grinding dept to surface grind it for me, last i heard the engine and fork truck were still running 10 yrs ago, You need a proper suface grinder mate.

John

Offline AdeV

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Re: Surface grinder....
« Reply #9 on: May 28, 2015, 04:00:57 PM »
All,

Many thanks for your excellent advice - I'll pass on the Snow machine then, for all the reasons given (work jumping about, wheel clogging and the bowing at either end).

Unfortunately, the big machine - which I'd absolutely love to own - is WAAAY too big for the space I have available. If anyone else is interested, it's on eBay (http://www.ebay.co.uk/itm/331545105660), BIN for £1500 or make an offer. Sadly, I expect it'll end up being scrapped.

Oz - great video find, that looks like exactly the sort of machine I should be looking for - relatively small footprint, but big capacity. I'd be happy to run an insert tool in it to just do ali heads, I reckon it'd be in use all the time, there's only a few places around me that can skim heads; and once I relocate to Portugal, I reckon I'd be the only one for miles around.

Either that, or I just need to look for a decent CNC milling machine with a bigger traverse than my old Mk2 Interact; I keep seeing Mk4's go past for moderate money, maybe one of those would do the trick; either that or a proper VMC in a box.

Thanks all! You just saved me 350 quid + P&P... The Snow is also on eBay if anyone wants it - http://www.ebay.co.uk/itm/151690273977
Cheers!
Ade.
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Location: Wallasey, Merseyside. A long way from anywhere.
Occasionally: Zhengzhou, China. An even longer way from anywhere...

Offline rotorhead

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Re: Surface grinder....
« Reply #10 on: May 30, 2015, 08:43:08 AM »
Hi Ade,

If you haven't already got a bit bigger milling machine, why not try for one with at least a 4ft table, it'll come in handy for other jobs too.

I've machined no end of heads on my Elliot Rapidmil, like others have said Aluminium really is easier done with a cutter, a bit of WD40 helps aswell.

I can post pics if so desired, but don't want to appear to have taken over your posting.
Chris
Sunny Scunny,
North Lincolnshire.

Offline vtsteam

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Re: Surface grinder....
« Reply #11 on: May 30, 2015, 11:09:53 AM »
I made a big steel disk single insert fly cutter to do the Ford 850 tractor head, which allowed me to just catch the ends with one side of the cutter on my round column mill drill. Not suggesting the same if you can afford a bigger mill -- that would be much better.



But it just got me thinking -- I have a pretty big compound slide mill/drill table that I've never used -- purchased long ago when I had considered making my own mill. I was just wondering, now though, if I put that on top of my present mill table, could I do longer work? Well probably, assuming one had enough head adjustment height.

It's not much different than mounting a rotary table on the mill..Again, not sayin it's preferable to a larger machine of any sort. But seems like I might be able to extend capacity on occasion that way. Possibly for width as well.
I love it when a Plan B comes together!
Steve
https://www.youtube.com/watch?v=4sDubB0-REg

Offline Jonny

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Re: Surface grinder....
« Reply #12 on: May 30, 2015, 05:45:06 PM »
Personally I would go for a larger manual mill such as a 942 with suitable tooling and power feed.
When you go to rebuild places aluminium heads on the floor freshly done with nothing more than a fly cutter and rough. Spin it up with slower feed rate can see colours.

Surface grinders do take up masses of room and none better than Snow.
Been out of precision grinding for 20yrs family ex biz, all our machines were Snows and we did have some large ones you climbed three steps with remote pedestal controls, scared the crap out of me ground used to shake 20 yards outside when changing direction. Machine to handle length of V12, bed would be minimum 10foot long plus the swing with working area circa 3ft to 4ft.