Looking for cast iron

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Looking for cast iron

This topic has 14 replies, 9 voices, and was last updated 28 October 2022 at 23:27 by Pete..

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22 October 2022 at 21:04 #618288
old mart
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@oldmart
I have long put off making a replacement cross slide for the museum's Smart & Brown model A because of its size. Recently, I realised that the limited throat depth of the mills would not prevent me from making a new copy of the cracked original. The radius of the cross slide from the compound to the rear end is about 14 inches, but there is no need to be able to rotate that more than about 200 degrees to be able to mill the dovetail. Now I am looking for a piece of cast iron about 18" by 6" and just over 1" thick. SG iron would be better for its ductility than grey iron. Everything depends on the cost, I might have to give up if it is very expensive. Does anyone know of a source?
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22 October 2022 at 21:04 #14679
old mart
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@oldmart
22 October 2022 at 21:23 #618291
HOWARDT
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@howardt
Fixture component suppliers are a source, such as WDS, not cheap but it is proof machined. Used to use a lot of their sections over the years.
22 October 2022 at 21:25 #618293
HOWARDT
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@howardt
Alternative would be to use steel and Turcite the way surfaces.
22 October 2022 at 21:28 #618294
peak4
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@peak4
You could try United Cast Bar in Chesterfield
https://www.unitedcastbar.com/

Bill
22 October 2022 at 21:58 #618296
Jelly
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@jelly
Best bet would be to ring commercial stockholders and ask them to process you the blank you need from a standard size product like 150*150 square; a big stockholder who carries lots of CI will hopefully carry rectangle sections in suitable size, saving you some hassle and cost.

But for what you pay in cutting fees, you offset not buying the additional 5" of thickness on that bar so it's always worth pursuing that. If they're regularly selling CI or Special Steels this kind of thing should be pretty normal for a stockholder…
- West Yorks Steel have always been great for me with small orders and special cuts (mostly die steel), and do carry cast iron in many grades.
- Colt Material Solutions carry significant quantities of CI in a range of grades with defined properties including ductility and vibration damping.
- M-Machine Metals Carry large section cast iron as both GR17 and SG, but oy as square or diameter, I don't know that they have the same processing facilities as the others, but are worth approaching.
Edited By Jelly on 22/10/2022 22:08:01
22 October 2022 at 22:09 #618298
Paul Lousick
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@paullousick59116
Have another cast at a foundry. Make a simple pattern out of wood that is slightly bigger than the 18" x 6" x 1" thick shape. Tell the foundry that it is for a museum and not needed immediately and they may make it for the cost of material when they are pouring something else.
23 October 2022 at 07:15 #618326
Pete.
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@pete-2
Have you thought about bronze tig or mig? I've had pretty good luck experimenting with it on cast iron, if it's just that little crack in your cross slide it wouldn't be a huge amount of work.
23 October 2022 at 08:03 #618329
DC31k
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@dc31k
Is the projecting part at the other end to the circular slot simply for attaching the taper turning attachment? If so, could it be made of a separate piece bolted on, thus reducing the overall size of the stock?

Perhaps mill away the entire outer dovetail, replace it with a steel ring, bolted in place and remake the dovetail. It is not a high speed sliding surface and steel is better able to resist the tensile force induced by the wedging action of a dovetail bolt.

A better repair than the underslung splint, and one that has the potential to apply force to close the crack might be to mill out a bow-tie shaped part in the top and glue in a spline piece (just as woodworkers do for repairing cracks). You make the spline slightly small and heat it up before inserting into its pocket. As it cools, it shrinks and pulls the crack together.
23 October 2022 at 10:10 #618333
Ady1
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@ady1
Agree with the welding option, tig best, mig possible

To my eye, it doesn't look like there is enough meat there to begin with, and that's why it cracked

Presumably it's a non-loading point
23 October 2022 at 11:19 #618341
ega
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@ega
old mart:

I enjoy your posts and wish you well with your search for CI.

My own wish is to know which museum you invariably refer to. Might you put it in your profile?
23 October 2022 at 18:26 #618386
Pete.
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@pete-2
Just out of curiosity could you tell us what's wrong with the bracing piece you've put on? Is it not working sufficiently? Or just not keen on the look of it?
23 October 2022 at 19:49 #618398
old mart
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@oldmart
The design is basically weak, but does allow the tailstock to be closer to the spindle than my bolt on repair. If I were to make a replacement, it would be stronger by design, even if made from the same type of cast iron. The outer curve could be at a larger radius, with its centre to the left of the original, leaving the width at the centre the same. This would add more material to the ends of the curved section. The thickness of the outboard curved section in a vertical plane could be greater, the extra underneath would not restrict the tailstock or the movement, which is about 7" total.

I have no idea when the damage was done, or whether it was caused by overtightening the two compound holding bolts, or crashing into the tailstock. The reinforcement was accompanied by doubling the bolts to 4 and not tightening them as much. The lathe was due for scrapping when it was donated to the museum.

Thanks for all the suggestions and links, I will be finding out

I agree about the length, I had originally contemplated making the rear end a separate add on part to reduce the radius, but below 11" rad would reduce the length of the dovetail length more than I would like.
23 October 2022 at 21:54 #618410
Pete.
Participant
@pete-2
It's hard to be completely sure from looking at those photos, but I get the impression the radius overhang is weak, what I'd do is use a die grinder to carve out the crack enough to fill with bronze, then make two little gussets with some scrap cast iron and braze those in place underneath to support the overhang.

Some experimenting with bronze cast Iron repairs.
28 October 2022 at 23:27 #618916
Pete.
Participant
@pete-2
Did you ever find a solution to this? If you can't find a cost effective solution I'll bronze braze it for you FOC, you'd need to cover the postage and send a couple of small bits of cast iron that could be used as gussets, I'd imagine some bits of scrap from anything would do .
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