Monarch Model C Lathe Bed Regrind

cash · Jan 26, 2016

I got an email from a guy last week looking to have his Model C reground. Since he was local I stopped over, he and his dad work out of their workshop on a farm and it was a great operation. He is does some gunsmithing on the side and his dad rebuilds steam engines. Prior to retirement his Dad work at a local machine tool rebuilder in town.

After some discussion and part of the deal is that I get to watch them moglice the saddle, I have never worked with moglice, only turcite. For this application moglice was the way to go and they were familiar working with it.

Upon inspection of the ways on my granite table there is a total of about .008" error in them. The tailstock end actually goes uphill on the vee and the flat. My assumption is this was like it since day one, about 11 months before Pearl Harbor............

Tomorrow we will begin grinding.

MCritchley · Jan 26, 2016

I wonder if the tailstock ways were ground like that on purpose?

That would make up for the front of the tailstock wearing out.

Spyderedge · Jan 26, 2016

Pardon the potentially dumb a$$ question. When working with heavy things like lathe beds, what's the best way to support the surface plate to avoid warping? Or do you just keep it on three points and rely on the plates thickness to prevent warping?

cash · Jan 26, 2016

MCritchley said:
I wonder if the tailstock ways were ground like that on purpose?

That would make up for the front of the tailstock wearing out.

No-both the vee and flat went up hill, from the middle about .005"!!!

Probably a WWI grinder running the lathe back then......

cash · Jan 26, 2016

Spyderedge said:
Pardon the potentially dumb a$$ question. When working with heavy things like lathe beds, what's the best way to support the surface plate to avoid warping? Or do you just keep it on three points and rely on the plates thickness to prevent warping?

Not sure what you mean? The lathe mounts to a frame or bed. so as I have it sitting on my table is how it would be mounted back in the shop. There are only points on the end. If there was a location pad in the middle we would probably then have to play with it.

Spyderedge · Jan 26, 2016

cash said:
Not sure what you mean? The lathe mounts to a frame or bed. so as I have it sitting on my table is how it would be mounted back in the shop. There are only points on the end. If there was a location pad in the middle we would probably then have to play with it.

That lathe bed is pretty heavy, how do you know the surface plate isn't warping under the weight of the bed? Probably won't matter in this case, and if it flexed it's a very small amount. Just curious.

cash · Jan 26, 2016

Oh-it is a 14" thick plate supported on the bottom via 5 points.

I guess I have never though about if a large plate will flex.

I think this lathe bed may way about a ton? I guess to me that is really not that much so I don't think about it.

This is a good question, maybe I could post a link in the inspection forum and see what people say over there?

Zahnrad Kopf · Jan 26, 2016

Man, oh man, oh man, oh man...!

I'm next! I'm next! Woo hoooooooooo! Hahahahahahaha!

Crap. How am I going to get this bed into the truck? See you soon.

I. Can. Not. Wait.

That thing makes mine look like a pee wee.

Matt_Maguire · Jan 26, 2016

The bed is supported as it sets on the legs, which seems to be very close to the end supports under the rock you got it setting on... It is what it is - nobody knows (still living anyway) how the bed got sagged so bad.

Toss it up & grind it, it'll be fine.

Matt

MCritchley · Jan 26, 2016

cash said:
No-both the vee and flat went up hill, from the middle about .005"!!!

Probably a WWI grinder running the lathe back then......

Guess I misunderstood the OP.
I'm having a hard time visualizing the slope.

Were the ways straight by the headstock than a slope up heading towards the tailstock?
Or are the ways not parallel to the base?

Somewhere I have read that a surface plate will stay in its tolerance under a 50 lb per square foot loading.

It would be an interesting experiment to check plate deflection before and after placing the bed on the plate.
The sensitive King Way vials or machinists level might tell an interesting story.

Street · Jan 26, 2016

looks like you have a nice big shop with some big equipment in it.

One thing it notice is the chips on the corners of your "boulder" aka surface plate corners, maybe they should mitre the corners just a little, little reduction in surface area but more chip resistant when or if you ever need another one made.

I like your shop since it looks nice and clean which is a big thumbs up from me,

keep up the posts your very knowledgeable and i may learn something.
Cheers.

cash · Jan 26, 2016

MCritchley said:
Guess I misunderstood the OP.
I'm having a hard time visualizing the slope.

Were the ways straight by the headstock than a slope up heading towards the tailstock?
Or are the ways not parallel to the base?

Somewhere I have read that a surface plate will stay in its tolerance under a 50 lb per square foot loading.

It would be an interesting experiment to check plate deflection before and after placing the bed on the plate.
The sensitive King Way vials or machinists level might tell an interesting story.

Ways not par alley to the base. I had the kingway on the bas but basically wing the round base part to take measurements of the fee way from the base, then I did the same with the flat way.

In the inspection forum they as well say 50 PSI the plate will deflect no more than 1/2 the tolerance.

Picture if the lathe bed was a flat plate. 24" x 96" long, as it site now 3/4 of it would be flat on the granite and the last 1/4 would be up about .005". Hopefully this makes more sense?

Street · Jan 26, 2016

Well your mentioning forces and pressures....be careful with this.
For a plate to bend there has to be a moment, this is a Force X Distance = moment as a definition.
Bending moments are resisted by the material strength in tension and compression as either top or bottom surface is in tension or compression, depends on how it bends.
Now if there is no distance there is no moment and is purely a crushing force on a set area and force on area = a pressure. so no deflection due to moment.
So if you have the legs under the applied crushing action you can ignore that action of moment, just use crushing.

So if applied = or exceeds material allowable it will crush.

Big thick high strength materials have lots of capacity to resist moments.
If a moment exists it will be a strain related property that will get you a deflection / displacement at a point.

Now in this also there is a effect called poisons ratio where the material squashes a little yet will recover back to original position as it has not yielded.
I don't know enough about surface plates yet but granite for sure will have different properties to steel.
Mostly applied to ferrous items but i would think logic could be applied to just about all materials..

Think of squashing bubble gum in between your fingers it moves out sideways, there is a ratio to applied force to resultant side expansion in steel called poisons ratio.

Surface plate people i would think know the properties of various grades i would hope, Staybridge , truestone etc.

At limit of my knowledge on granite..

Richard King · Jan 26, 2016

A couple of thoughts. Take a .001" or .0015" feeler gage and see if the bed is down flat on the plate. Hard to believe the bed was ground out of parallel .008" . You could double check under the ways where the rack goes too to verify the top. That plate looks fine to me and would not bend .008. You could take a precision level on the plate and if you have the plate level before you set the bed on it before hand, that would be great. If it isn't level then take the screw cover off the level cover and adjust the level out of level so the bubble is level to the earth.

Then lay a long straight-edge or scale so you can slide the level along the same line. If the plate is bending you can see that with the level bubble. Write done what it says. Then if it is bent, lift the bed off the plate and re-check the plate with no weight on it.

I would think setting it up on your grinder would show the same thing.

Another tip when using the King-Way. Have the cross bar as low as possible and in the newer ones i drill a hole thru the clamps screws so I can tighten them a bit tighter. Remember the bubbles are .0003 or some of the Sheer Tumico vials were .0005" per 12". It looks as if the V and flat are about 15" apart, so the cross vial is reading more then what the bubble says. The other bubble is less as it is checking the length of the 8" Chanel Slide. Rich

MCritchley · Jan 26, 2016

cash said:
Ways not par alley to the base. I had the kingway on the bas but basically wing the round base part to take measurements of the fee way from the base, then I did the same with the flat way.

In the inspection forum they as well say 50 PSI the plate will deflect no more than 1/2 the tolerance.

Picture if the lathe bed was a flat plate. 24" x 96" long, as it site now 3/4 of it would be flat on the granite and the last 1/4 would be up about .005". Hopefully this makes more sense?

Thanks, that paints a clear picture.

50 psi makes more sense.

Mebfab · Jan 26, 2016

If someone stopped by with a similar bed, how much would it cost to get it touched up?

Milland · Jan 26, 2016

MCritchley said:
Thanks, that paints a clear picture.

50 psi makes more sense.

From an older PM post:

"Accuracy Under Load
Starrett Crystal Pink and Charcoal Black Granite plates have a thickness capable of supporting a total normal load equal to 50 lb. for each square foot (24kg for each 1,000 sq. cm) of surface area loaded in the center of the plate - without deflecting the plate along a diagonal of more than one-half the flatness tolerance. This is the accepted rating in the U.S. Federal Specification GGG-P-463c."

It's pounds per square foot, not inch. It's easy to get those units mixed up.

Edit: And here's that thread, may be of use: http://www.practicalmachinist.com/vb/general/4x8x12-thick-surface-plate-load-limit-165264/

Heavey Metal · Jan 27, 2016

Needs to be on 3 points that are swiveled to learn anything.

cash · Jan 27, 2016

Richard King said:
A couple of thoughts. Take a .001" or .0015" feeler gage and see if the bed is down flat on the plate. Hard to believe the bed was ground out of parallel .008" . You could double check under the ways where the rack goes too to verify the top. That plate looks fine to me and would not bend .008. You could take a precision level on the plate and if you have the plate level before you set the bed on it before hand, that would be great. If it isn't level then take the screw cover off the level cover and adjust the level out of level so the bubble is level to the earth.

Then lay a long straight-edge or scale so you can slide the level along the same line. If the plate is bending you can see that with the level bubble. Write done what it says. Then if it is bent, lift the bed off the plate and re-check the plate with no weight on it.

I would think setting it up on your grinder would show the same thing.

Another tip when using the King-Way. Have the cross bar as low as possible and in the newer ones i drill a hole thru the clamps screws so I can tighten them a bit tighter. Remember the bubbles are .0003 or some of the Sheer Tumico vials were .0005" per 12". It looks as if the V and flat are about 15" apart, so the cross vial is reading more then what the bubble says. The other bubble is less as it is checking the length of the 8" Chanel Slide. Rich

We did check the feet or pads of the lathe bed on our surface plate. Since there are only 2 pads, one at each end the are down, but I do believe the very ends our outsides were maybe a .001" or .002" open. when we put it up on the way grinder even though thesis a very solid area we will still shim where it is open.

I did measure about .003" wear in the area about 24" out from where the chuck would be, and with normal wear over a 75 year period this seems normal to me. So the tailstock end runs up hill about .005". yes, I know this is odd but we double checked our measurements, re-zeroed the indicator and checked again. We did this on both the saddle fee and the flat.

Once I get up on the machine we will re-verify with an indicator and then we will sees where it hits, but tailstock end should be first. This is why we check on the plate first-so we know where it will hit first.

Richard-thanks for the tip on keeping the crossbar lower. Yes, this devise you sold me I really have to crank on the knobs to keep tight. I have a channel lock and carefully tweak them to make sure tight. When you say drill a hole thru the camp screws do you mean drill thru say where the knurling is? Then I could put a small dia pin thru the hole to get some more leverage?

I just noticed yesterday one of the vials had USN and a s/n after it. I will check this sometime with a feeler gauge to see what graduation they are.

I will take some pics of the vials to show the level.

Richard King · Jan 27, 2016

Now taht I think about it that King-Way was a King built unit. Or my dad assembled it. He licensed Sheer Tumico and Do-All to build and sell them too. He used .0003" bubbles and they used .0005" bubbles. Yours is .0003" if they are still original. I wrote another one talking about 3 points as Heavy mentioned, but some how I lost it. dang computers...anyway, he is correct if you don't have a good plate and all your checking is twist. But to be a detective to discover what you have sitting on a qualified plate first is the way to go. If the plate is on 3 main points and 2 stabilizers and lapped too grade A or better, that is the way to do it. You did it the exact way I would do it, check the tailstock ways first.

As far as the holes in the knobs, I meant in the round part nearest the threaded side. on some of the early models that was pretty small so if you have room drill the knurled area in 4 places about a 1/2 deep to insert a pin punch. In the newer models we also put a needle bearing under it so we could improve on the steel knob resting on the bronze clamp. thanks for the thread. Rich

Monarch Model C Lathe Bed Regrind

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