"Repair" a damaged mill table with a pallet???

challenger · Jun 12, 2018

My old Index mill has a severely damaged table. I've had this mill for many years but it's been unused by me. I recently got a hair to get it running so I disassembled and cleaned it and am about to paint it and reassemble. The table has a lot of damage from past users and much of the T-slot areas are unusable. Is it practical to put a a piece of aluminum on top of the table as a permanent pallet or is this an all around poor idea? I bought is slab of 1" Fortal plate Thats the size of the table way back when I bought the machine. It's Blanchard ground fwiw.
I'm not looking to get high precision results from the machine but don't really want reliable unreliability from the table twisting etc. I'm not a professional machinist by any means so please excuse my ignorance.
Thanks for the advice.

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HuFlungDung · Jun 12, 2018

That looks pretty nasty

Looks like someone else already had the notion to bolt a subplate on top, as that 8 hole pattern is not a normal feature I've ever seen on a mill table. Adding the subplate does rob you of some height (think of distance between drill in chuck and work sitting on table at lowest position).

I'm not sure if the material you have is flat and parallel sided enough to just slap on and use. What are you planning to do with the machine?

A subplate can add some extra utility if it is done thoughtfully. For example, it could be a bit wider than the table, and have holes in the edges to clamp a 'fence' on, or other clamping devices as required to hold onto some oversize parts.

challenger · Jun 12, 2018

Thanks. The Blanchard grind is supposed to be less than .001" from what I remember. Not precision but OK for my purposes. At a full 1" thick it completely covers the T-slot area of the table. I agree the table was already drilled in the eight spots you pointed out and this may be useful for mounting the aluminum. Still pondering the options.

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Mud · Jun 12, 2018

I would do it. I'd drill and tap 1/2-13 holes in a 2" grid pattern all over to use for hold down clamp studs. I put iron plates on my VMCs with that pattern because we can't reach the whole table from the T slots, and I've had AL plates on also. Putting a few 1/2" (or other size is OK) reamed holes in line with the table axis can be handy for aligning workpieces with dowel pins.
In theory you can get a conflict between the expansion rate of AL and iron with temperature change that causes distortion, I'd bet that you'd never be able to tell with that machine. Spray rust preventative or put grease between the table and plate to prevent corrosion..

NAST555 · Jun 12, 2018

Here is one of the reasons that I advocate having T-nuts that are not threaded all the way through. The pressure from the bottom of the stud pushing up can cause this crap but maybe I am thinking in the wrong way.

I say go for it. I have repaired a swivel vise by milling out the broken piece and surface grinding the top. Then putting a steel "sub plate" on top of it, bolting it down and grinding the whole assembly.

Pretty sure your fix will be waaaaay better than what you are currently sitting with.

projectnut · Jun 12, 2018

I think it's certainly doable, but at what cost? Before purchasing I would check with several aluminum suppliers. It might not be indicative of other retail suppliers, but Speedy Metals charges about $115.00 per square foot of cast aluminum tool and jig plate. That would put the cost of plate alone near $460.00.

A better option might be to search out used machine dealers to see if you can buy a used table. There are 2 Bridgeport tables currently posted on eBay. One for $450.00 OBO. The other for $650.00 OBO.

Before making any investment I would thoroughly inspect the rest of the machine. Quite honestly that's the worst table I've ever seen. If the rest of the mill is in similar condition it might not be worth rebuilding.

tnmgcarbide · Jun 12, 2018

projectnut said:
I think it's certainly doable, but at what cost? Before purchasing I would check with several aluminum suppliers. It might not be indicative of other retail suppliers, but Speedy Metals charges about $115.00 per square foot of cast aluminum tool and jig plate. That would put the cost of plate alone near $460.00.

A better option might be to search out used machine dealers to see if you can buy a used table. There are 2 Bridgeport tables currently posted on eBay. One for $450.00 OBO. The other for $650.00 OBO.

Before making any investment I would thoroughly inspect the rest of the machine. Quite honestly that's the worst table I've ever seen. If the rest of the mill is in similar condition it might not be worth rebuilding.

why in hell would he do that?

if you'd read his first,second posts, he already has the cast, ground plate to fit his
machine.

Garwood · Jun 12, 2018

projectnut said:
I think it's certainly doable, but at what cost? Before purchasing I would check with several aluminum suppliers. It might not be indicative of other retail suppliers, but Speedy Metals charges about $115.00 per square foot of cast aluminum tool and jig plate. That would put the cost of plate alone near $460.00.

A better option might be to search out used machine dealers to see if you can buy a used table. There are 2 Bridgeport tables currently posted on eBay. One for $450.00 OBO. The other for $650.00 OBO.

Before making any investment I would thoroughly inspect the rest of the machine. Quite honestly that's the worst table I've ever seen. If the rest of the mill is in similar condition it might not be worth rebuilding.

That's about 3 times what that aluminum plate costs in real life.

I would cover the table and use a hole pattern like stated by others.

M.B. Naegle · Jun 12, 2018

I'd think the easiest repair would be to mill off the lips of the slots so you can countersink replacement strips in. Iron would be preferred buy mild steel would work well too. If it became damaged again it would be replaceable. I've seen a few machines that came new from the factory built like this. I think it was so that all the milling could be done with standard cutters; no T-slotting needed.

Danny VanVoorn · Jun 12, 2018

At the shop I worked in many mills had a sub table two times wider than the original, believe it was jig plate. Reason was because a lot of the aircraft parts were large and needed some features that the NC machines couldn't finish so they were done on the conventional tilt head mills. They were drilled for King Serts and had rows of 1/2" drill bushings installed for use as a quick alignment to the X axis. I saw one being installed and they used T nuts and 1/2" bolts to hold them down and indicated for alignment to the table. I finished a lot of parts on those machines and never had a problem other than the unsupported part of the top did have a slight sag to it.
I say go for it, what's the worse thing that can happen other than you wind up with a useful mill that looks great.
Dan

gustafson · Jun 12, 2018

Sub plate absolutely

why waste time drilling a bunch of holes

drill the holes where you need them when you need them

Or as I have done, drill a pattern for guide bushings and pins and make everything a fixture.

Vise on one fixture

job 5 on another

changeover time 15 minutes including drinking coffee

HuFlungDung · Jun 12, 2018

gustafson said:
Sub plate absolutely

why waste time drilling a bunch of holes

drill the holes where you need them when you need them

Or as I have done, drill a pattern for guide bushings and pins and make everything a fixture.

Vise on one fixture

job 5 on another

changeover time 15 minutes including drinking coffee

~~And for the love of god, don't drill through the subplate into the table!~~

projectnut · Jun 12, 2018

tnmgcarbide said:
why in hell would he do that?

if you'd read his first,second posts, he already has the cast, ground plate to fit his
machine.

I guess I missed the sentence about the Fortal plate. In any case the table is still the nastiest one I've seen. If the rest of the machine is in similar condition it's going to be an expensive project.

Limy Sami · Jun 12, 2018

M.B. Naegle said:
I'd think the easiest repair would be to mill off the lips of the slots so you can countersink replacement strips in. Iron would be preferred buy mild steel would work well too. If it became damaged again it would be replaceable. I've seen a few machines that came new from the factory built like this. I think it was so that all the milling could be done with standard cutters; no T-slotting needed.

That's what I have seen done and it worked very well, …...so if I wanted tee slots, I would have no hesitation doing it on a machine of mine.

IIRC Gauge Plate (01 oil hardening ground flats) was used.

M.B. Naegle · Jun 12, 2018

M.B. Naegle said:
I'd think the easiest repair would be to mill off the lips of the slots so you can countersink replacement strips in. Iron would be preferred buy mild steel would work well too. If it became damaged again it would be replaceable. I've seen a few machines that came new from the factory built like this. I think it was so that all the milling could be done with standard cutters; no T-slotting needed.

For Inspiration: this is the table on our Brown & Sharpe #12 Production Horizontal Mill. Note that on these they milled one solid slot in the table and had a step milled into the 'rails' to create the t-slot. On yours you would only need to mill it out enough for a flat strip.

IMO I would hesitate to permanently modify the table to be some other work-holding system than it originally was. I would leave the table as is, or repair it to be as it was, and then do any thing else with a separate plate (as others have said) that bolts to the table via the original t-slots. That way if you make a mistake or deside the new system doesn't work they way you wanted it to, you can always go back to the OEM T-slots.

challenger · Jun 12, 2018

Thanks all. I realize this forum is geared toward those that make their living in the machining industry so I'm especially grateful for all these great ideas.
At this point I'm leaning toward replacing the T-slots with strips of steel. This is easily accomplished as the mill will obviously (and unfortunately?) reach all the damaged area. There is no lent of metal under the damaged table for securing new "caps".
This is a 76 year old Index model 40 and it shows its age but it is still fine for my purposes. It's got plenty of backlash and the ways aren't great looking but I can get by with it as is. There are no breaks or cracks in any of the castings so it will hold up in my home shop just fine I believe.
I got the mill a decade ago as an even trade for a barely used Asian POS that I made the mistake of buying. I have a thing for old USA machinery. My lathe, horizontal mill and this mill are older than I am and I'm 60. This mill would likely be scrap had I not taken it. Needless to say one wouldn't find a machine of this condition in an income producing shop but IMO it is still miles better than the garbage machine I traded for it. This is at least a real mill and not a glorified drill press that Asian "mill" was. This is just my opinion.

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henrya · Jun 12, 2018

Mud said:
I would do it. I'd drill and tap 1/2-13 holes in a 2" grid pattern all over to use for hold down clamp studs. I put iron plates on my VMCs with that pattern because we can't reach the whole table from the T slots, and I've had AL plates on also. Putting a few 1/2" (or other size is OK) reamed holes in line with the table axis can be handy for aligning workpieces with dowel pins.
In theory you can get a conflict between the expansion rate of AL and iron with temperature change that causes distortion, I'd bet that you'd never be able to tell with that machine. Spray rust preventative or put grease between the table and plate to prevent corrosion..

I’d do this and attach the plate with 4 through bolts to attach to the table and then epoxy the whole thing down with the 4 bolts just holding it in place - just snugged down so not to warp the plate. After the epoxy cures the plate will be mounted as flat as it is made and stress free.

crossthread · Jun 12, 2018

After you glue and screw your plate down you may be surprised at how much it has warped. Have you thought about running a fly cutter over the entire table after you add your plate?

Rob F. · Jun 12, 2018

crossthread said:
After you glue and screw your plate down you may be surprised at how much it has warped. Have you thought about running a fly cutter over the entire table after you add your plate?

He said the machine is very worn so maybe that would do more harm than good?

henrya · Jun 12, 2018

crossthread said:
After you glue and screw your plate down you may be surprised at how much it has warped. Have you thought about running a fly cutter over the entire table after you add your plate?

Let me elaborate on my suggestion:
The screws only locate the plate. The epoxy holds and supports the plate. Like mortar under a brick, a full bed of adhesion and support. No stress, screws finger tight. It’ll stay flat.

The problem now comes in how the table moves on its ways. We didn’t fix that part. It might not be too bad but that is a hard used machine.

"Repair" a damaged mill table with a pallet???

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