Threading A Used Face Plate

[John Buffum]

I bought a used face plate at Cabin Fever. Hardinge? LOTS of bored and tapped holes, and 4 T-Slots. It didn't have the 1-1/2 x 8 thread I needed, so I filled with weld, and tried to bore and tap. Part of the weld is cuttable, and the other part is tool steel hard. My South Bend 9x21 can't hold the boring bar still when it gets to the hard part.

Suggestions?

[Bented]

Carbide tooling?

[John Buffum]

Have used several inserts up, already. Thinking of grinding out and building up bronze.

[Richard P Wilson]

Its cast iron? And you welded it and are surprised its got hard bits in it?
Anyway, likely the welding warped it anyway, so you might as well dump it in the remains of a fire at the end of the evening (well it is winter ) cover it over and leave it overnight. Theres a good chance that will do some good.

[BCRider]

Any chance of putting it into a burn barrel get a good fire of scrap wood going and then let the whole thing cool overnight?

I understand that this sort of thing can happen when cast iron is welded. I'm no metallurgist but I'm going to guess that part of the excess carbon in the cast iron mixes with the usually milder grade of steel filler rod and you end up with just the right carbon content for making tool steel in the mixed areas of the weld?. And it "quenches" in the rapidly cooling body of the job itself?

With warpage issues I might have gone with making up an adapter to fit between the existing thread size and the 1 1/2-8 you need. Or if it was 1 1/2-10 or something then to bore out the whole thread and make up an insert that presses or gets bonded (Loctite 680 is AMAZING STUFF! ! ! ) and then drilled, bored and threaded to your needed size.

But it's done now so perhaps try the annealing idea if that is an option? Or maybe a local bigger shop that does heat treating can anneal it along with some other job for a fiver or two?

EDIT- Apparently Richard and I had the same thought at the same time...

Given that it needs to at least get up to a blue oxidation color temperature to get even soft enough to machine it I'm thinking it will need to be a pretty good fire. I'd suggest the electric oven on a cleaning cycle. But maybe not if you have any sense of self preservation The "blue spring" temper to be gotten from a casual fire or oven won't totally anneal the hard spots. But at least they will then be machinable.

[mickeyf]

I would also suggest a pressed in adapter, and at this point rather than annealing, or if that does not work, you could simply bore out larger than the welded area (annular cutter, or trepanning) and fit your adapter to that.

[The Metal Butcher]

Sounds kinda like false economy to me. Somewhere, someone is boring out a 1.5-8 faceplate for a bigger lathe...

[Paul Alciatore]

Yes, bore it out and make an adapter plug that is either a shrink fit or that has threads and a shoulder to hold it in place against the forces of the lathe use. And then bore and thread that adapter.

Why do people with torches always grab them so fast? Oh, I guess it is faster than making a plug.

I would also suggest a pressed in adapter, and at this point rather than annealing, or if that does not work, you could simply bore out larger than the welded area (annular cutter, or trepanning) and fit your adapter to that.

[John Buffum]

The material is some kind of tool steel. Unknown what. Yes. The plug sound like a great idea. Cheepa than brazing, for sure. There is a tapped hoe in the side, already. I could drill the plug, and make a pin to prevent spinning. Heat fit sounds good. Thanks.

[masheenest]

An 8" dia. x 1.750" long disc of cast iron will cost $50.00 from McMaster-Carr.
A 6" length of 8" dia. steel lists for $31.46.
Stop beating your dead horse.

[oxford]

A 6" length of 8" dia. steel lists for $31.46.
Stop beating your dead horse.

Maybe I missed something but I only see a 1/2” thick 8” round listed for that price.

[old mart]

I have bolted in centres on 2 faceplates, which avoids the drawback of welding. The first was a 9" plate threaded for the Myford 1 1/8" size. The Smart & Brown model A has a 1 3/4" spindle size, so I bored out the faceplate to fit a small 1 3/4" plate which otherwise was too small for a chuck. It fits from the faced off rear centre of the faceplate with 6 double diameter studs (6/8mm titanium used on Westland Lynx gearboxes, I have dozens here at the museum) and locknuts. They were fitted at the minimum usable PCD and the ends of the studs are just underflush to the surface of the plate.
The other plate was also a 9", the biggest that the S & B will hold and the centre is a backplate for the Atlas 12 x 24 that we will finish next year and sell. I can't remember what threads were originally in that one.
If you can hold your plate in the lathe, then a bolted in centre is an option and the number of bolts will be dependent on any slots or holes near the centre of the plate.
I will try to remember to post photo's of the plates that I adapted tomorrow.
The centre could be made from CI or mild steel, Here in the UK it is easy to buy 3" diameter by 2" long cut pieces of mild steel on ebay, for minimum machining.

[masheenest]

Maybe I missed something but I only see a 1/2” thick 8” round listed for that price.

Right you are. I read it as 1/2' (foot). I apologize.

[BCRider]

For fitting an adapter plug don't discount the "cold" option of using one of the industrial adhesives. I'd easily trust Loctite 680 (just for one example) for bonding an adapter into the bored out faceplate. I'd bore out the faceplate and fit the plug with the adhesive then drill bore and thread the ID. The adhesive is amazing for this sort of use. And with a gap tolerance of as little as .002 up to about .006 with excellent strength it's pretty easy to hit a suitable fit compared to a heat shrink fit.

[old mart]

Here are the 2 plates which I made up with different centrest the 6 tee slot one is used on the Smart & Brown, the other is for the Atlas.