Author Topic: Cast iron guide way grinding....  (Read 6778 times)

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2523
  • Country: fi
Cast iron guide way grinding....
« on: September 07, 2015, 09:51:48 AM »
I have a problem with my milling machine - it's worn out pretty badly.

My prefered solution would be to take the parts to be milled straight, but can't locate anybody nearby who could this any reasonable budget.

Plan B: Make an small contraption to grind 0,1 to 0,02 mm maximum. Before rushing into anything unfeasible I have made a roadmap and one big obstacle is how to grind cast iron.

Consensus seems to be: For grinding cast iron, non-ferrous metals and non-metallic materials, select a silicon carbide abrasive. Ant it needs to be dressed frequently.

I would very much like to use standard aprox. 1,1 kW 2800 rpm electric motor on direct drive (there is a problem on how to preload the bearing....).

All other ways are flat ways, but table has a dovetail ways and there is a real chance that they are about 50 degrees. Not that standard.

Anyways, problems aside:
1) Is silicon carbide wheel my only choice or are any of the "diamond" wheels a possibility.
2) Is it possible to use a cup wheel and successfully grind the flat ways on face surface of the wheel without oscillation?
3) Is it possible to dress the periphery to the dovetail angle and use it to grind the dovetail?

I realize that very little of material is going to removed per pass, many passes, dressing the wheel often and probably one way will take best part of the day.

My first idea is to build a fitting straight onto electric motor shaft, which should be easiest part of the whole thing, but I need to find out how much the bearings have end float and is there a simple "close enough" way of making it small enough. I don't want to to get sidetracked into building a grinding spindle - unless I really have to.

I never have done any cast iron grinding and some stuff I have read hints that it is different. Just is it doable?

Thanks,
Pekka

Offline Manxmodder

  • Hero Member
  • *****
  • Posts: 739
  • Country: gb
Re: Cast iron guide way grinding....
« Reply #1 on: September 07, 2015, 11:03:15 AM »
Pekka, your idea to create a rig to grind the ways sounds very reasonable to me. Onthe subject of grinding cast iron,I have ground many cast iron cylinder heads and brake discs over the years and all worked out fine with silicon carbide wheels. Coolant does improve the outcome.....OZ.

Helixes aren't always downward spirals,sometimes they're screwed up

Offline Swarfing

  • Sr. Member
  • ****
  • Posts: 417
  • Country: gb
Re: Cast iron guide way grinding....
« Reply #2 on: September 07, 2015, 11:09:45 AM »
If you can ensure the head is square to the table could you not just fly cut it?
Once in hole stop digging.

Offline Swarfing

  • Sr. Member
  • ****
  • Posts: 417
  • Country: gb
Re: Cast iron guide way grinding....
« Reply #3 on: September 07, 2015, 11:10:38 AM »
Ignore that just realised you were talking about the dovetail and ways...Doh!
Once in hole stop digging.

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2523
  • Country: fi
Re: Cast iron guide way grinding....
« Reply #4 on: September 07, 2015, 11:14:11 AM »
Pekka, your idea to create a rig to grind the ways sounds very reasonable to me. Onthe subject of grinding cast iron,I have ground many cast iron cylinder heads and brake discs over the years and all worked out fine with silicon carbide wheels. Coolant does improve the outcome.....OZ.

Nice. What kind of coolat did you used? I know only a swing type surfacer for cylinder heads. I read that the head has abrassive segments for cast iron and a fly cutter type insert for aluminium.

I was trying to find a cup wheel taper angle. Lots of reference to diameters and "type 11" but no agle was given.

Pekka

Offline Manxmodder

  • Hero Member
  • *****
  • Posts: 739
  • Country: gb
Re: Cast iron guide way grinding....
« Reply #5 on: September 07, 2015, 11:19:07 AM »
I've used both the segmented cup type and ordinary peripheral wheels with success. The peripheral wheel will need much smaller feed rate than the segmented type. Coolant was just a standard grinding water based concoction/mix.....OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline chipenter

  • Hero Member
  • *****
  • Posts: 909
  • Country: gb
Re: Cast iron guide way grinding....
« Reply #6 on: September 07, 2015, 02:57:01 PM »
Have you thougt of using a bench grinder with a cup wheel , no problem with end float and the speed is right .
Jeff

Offline Jonny

  • Hero Member
  • *****
  • Posts: 780
Re: Cast iron guide way grinding....
« Reply #7 on: September 07, 2015, 04:58:32 PM »
If the jobs done right a cup type of wheel will be used for the dovetails.
Will need to change wheel any way to do the flats and sides.

Biggest problem will have is the constant dressing and setting up which may not be true. Pros use angled heads, once setup does the lot so all true.
Personally I wouldn't entertain the idea, though may look fine wont be true.

Offline Pete.

  • Hero Member
  • *****
  • Posts: 1075
  • Country: gb
Re: Cast iron guide way grinding....
« Reply #8 on: September 08, 2015, 01:54:51 AM »
You could scrape that much. It would be a lot of work but you'd be good at scraping when you were finished.

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2523
  • Country: fi
Re: Cast iron guide way grinding....
« Reply #9 on: September 08, 2015, 03:31:53 AM »
I have measured significant end float on my two bench grinders, also they become pretty big after 1 kW. I measured the end float of the motor and it was incredibly small (0,03 mm) with aprox. 100 N of force, at first I could not feel anything - must be good wave spring on rear bearing? That will not do as it is.

Pete, no way I can scrape that much. I would in a lot of pain and step over my beard before it would be finished...

Jonny, I realize that it is iffy....I need to most of metal out from the wrong places and leave enough on the right places. I'm pretty sure that if I have only 0,01 mm relatively geometrically true to go instead of 0,00 - 0,2 mm peaks and valleys - I might have a chance of getting it close enough with scraping.

You are right on tilting head....It probably would be a good idea to have some sort of small adjustment to get the head "trammed" or just a little off....and dressing needs to be addressed.

I have a small worn out lathe bed to practice :lol: before I'll destroy (or salvage) the mill. I'm still looking to have someone to mill ways closer to 0-0, but surpricingly very few hobbyist seem to have mill capable of cutting awkward objects about 1 metre long.

Pekka

Pekka

Offline trapper

  • Jr. Member
  • **
  • Posts: 52
Re: Cast iron guide way grinding....
« Reply #10 on: September 08, 2015, 04:10:08 AM »
Do you have a shaper,doubt if you would need to touch the dovetail be a question of getting right into the corner of where the dovetail starts.I think a mill would be your best bet use a dovetail cutter skim base lick the dovetail up scrape the finish-seen many milling machines  tables go on to a planer mill come off looking new-clean top table up skim all burrs out of slots,this done using shaper tooling

Offline MetalMagus

  • Jr. Member
  • **
  • Posts: 43
  • Country: gb
Re: Cast iron guide way grinding....
« Reply #11 on: September 08, 2015, 07:14:18 AM »
Pekka,
Instead of grinding the ways could they not be built back up.

See link for Moglice.. Might be an alternative.

http://www.moglice.com/moglice.html

Cheers

Sean

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2523
  • Country: fi
Re: Cast iron guide way grinding....
« Reply #12 on: September 08, 2015, 07:27:32 AM »
I don't think we have that size shapers here. Table is 1000*250*95 mm and while it is not that big, it's still bigger that normal hobby/light industrial machines can handle.

Moglice &al. Seems to be here for a big machine rebuilds, no-one does it small scale and it is expensive here, needs pocketting and all stuff. To fix this machine would exceed the price of newer (still old) one.

For DIY route I would need pristine "mould" to make nonstandard dovetails....project by itself.

Pekka

Offline Jonny

  • Hero Member
  • *****
  • Posts: 780
Re: Cast iron guide way grinding....
« Reply #13 on: September 08, 2015, 07:40:12 AM »
I would be very very weiry of scraping having seen and heard the shear amount of horror stories of an ex family run precision grinding co.
Never used to fail "Ive only took a couple of thou off" To put right almost certainly 12 thou of every face had to come off.

Unless one of a few highly skilled scrapers in the whole world, leave well alone or treat it as a last resort before scrapping.
Used to be able to scrape pretty well but lost the knack over 35 years ago.

Way out may be to source someone with a big accurate robust mill with power feed and pay them a premium to do it yourself.

Offline Fergus OMore

  • Hero Member
  • *****
  • Posts: 1012
  • Country: england
Re: Cast iron guide way grinding....
« Reply #14 on: September 08, 2015, 03:04:51 PM »
I'm hardly in the position to even talk(Thank you). Standing off a bit, might I mention that wear on machine tools is rarely as bad as first imagined. A wear of a scant thous wear will multiply to two thous in machining or worse.  A scrape of a thous might restore something that is a rattling old fit.

I once restored a bit of a mangle of a Myford lathe for a friend that was so worn that it was good for bananas but not much else. I t went onto one of these Lumsden grinders( yea, my wife's family were shareholder until they went bust) but a Blancharding  might only remove a few thous but you have a sort of decent basis on which to work.
You need references and that solves a lot of hard graft, If yu have something reasonably true, you can scrape to the newly Blanharding surface( a modest few coins) Again, if you go the Devcon or whatever plastic filler route, you do no damage. If you make a mistake, you put on more putty. Whatever you do, you are not doing ANY more damage than where you were.

My lathe bed is slideways ground - but only the bed. This was £200 and the saddle wich was Turcited cost another £50. These were from a small North East firm which restored larger machine tools to as good or better than original.

The above is worth thinking about. Filled plastic is   not bodging Try it, please

Regards

Norman

Offline PekkaNF

  • Hero Member
  • *****
  • Posts: 2523
  • Country: fi
Re: Cast iron guide way grinding....
« Reply #15 on: September 09, 2015, 03:27:41 AM »
Thanks Jonny and Norman,

Could not sleep last night and I watched some videos and googled some views about scraping vs. moglice/turcite.

Bottom line is that I need to have ways trued (milling, grinding, and/or scraping) and then I have an option of using same method or "plastic" for the mating surface. Each method has it's merits and this I need to weight against availability and price of the method.

I'll give plastics/composites an consideration and check availability.

Dogs are still out to see if I can have most parts clamped on the mill and have somebody to do much of the milling/gringing but no answers yet. I'm working slowly on plan "B" which is that I need to do it myself.

Thanks,
Pekka

Offline hanermo

  • Full Member
  • ***
  • Posts: 103
Re: Cast iron guide way grinding....
« Reply #16 on: September 16, 2015, 10:39:03 AM »
An easy practical solution is to call the local haas dealer, they are nice guys, I knew them.
Ask them who has a VF4 or bigger and will do a favour for a low cost, when they are not busy.

They can mill it flat and straight on the flats in 5 minutes run and 0.5 hours setup.
With  V-blocks or a 4th axis they can also do the V-parts.

No-way it will be off by 0.01 mm or more.
Cast iron is very easy to machine.

Ive seen at least 3 guys vids use homemade sleds and even routers ! to hold the stones, and they all went well.

Richard King agrees that even flap /grinding wheels ! on air-powered grinders are a decent solution, to remove a bit at a time.
King of like ghetto power-scraping.
And he has used it, on big (6m long iirc ?) machines, by his own admission.
There is a youtube video I think (small divots are made with a flexible-type wheel).

It sounds a bit scary, but controlled material removal is not that hard, with power tools.
Wont look flash, but would probably be fairly flat and true, on a global basis.

I suggest that the haas route will cost around 100€ and the self-effort will cost 100+ hours of work.