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Quick Machinists Jacks

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Vic17/11/2019 14:43:50
2500 forum posts
14 photos

I have on several occasions needed a Machinists Jack or two but didn’t have one. I resorted to packing up the work with whatever came to hand and made a mental note to add making a couple of jacks on the “to do later” list.

For one reason or another they’ve been pushed back - for a couple of years! laugh

Then I came across this idea on a website and went on a hunt in the workshop to see what I had. I knew I had the long connecting nuts in M12 Stainless somewhere and I also found some M12 cap head socket screws. I just got a couple of bolts and some half nuts on eBay. It was then just a case of skimming the ends of the long nuts and the tops of the bolts which only took a few minutes.

Obviously not as fancy as some jacks out there but these will do me just fine.


old mart17/11/2019 16:13:48
1787 forum posts
138 photos

Its nice to have a small supply of these jacks, they don't get much use, but when they are required, they are worth their weight in gold. We have a selection from about 5/8" starting height to 4", I have only needed them once. The long threaded couplings included in the tee nut clamping sets have potential for dual applications.

Vic17/11/2019 18:47:57
2500 forum posts
14 photos

Forgot to add the site I saw them:


If required I’ll drill my two stainless bolts for additional fittings as suggested.

old mart17/11/2019 20:42:35
1787 forum posts
138 photos

I looked at the link, and one think caught my attention, the use of screwjacks on a lathe faceplate. You would have to be very careful in that application, to allow for centripetal forces, of risk getting a nasty surprise.

Clive Foster17/11/2019 21:33:58
2206 forum posts
73 photos

By the very nature of things machinists jacks made from joining nuts have a rather small footprint. Makes them less stable than the conventional kind but also means you can squeeze them in where a bigger one won't go.

Several years ago I ended up with a handful of joining nuts left over from a job and considered making some jacks like that. I planned to make larger feet to screw in the bottom if needed to make them more stable and / or bridge the mill table slots. Was going to make my feet round but, on reflection, suspect rectangular ones might be more successful. In reality I'd probably have made feet on demand by poking a countersunk head screw through lump of "whatever" roughly shaped to fit the space and eventually ended up with a collection of shapes and thicknesses that worked for me.

In the event I lucked into several properly made jacks and spacers for "£ very little" before I got round to making mine.

You will almost certainly need some "pointy cap" ended screws to help support less than flat or less than smooth items. Best to make some whilst you are at it. Odds are when you need some you won't have any suitable studding or set-screws to hand. I often cheat when that sort of "Will need it. But when?" thing arises and sequester some material stock. Been 20 years before it got used on occasion!

If using them on a lathe faceplate obviously bolt them through from the back so they stay put. I'm not brave enough to use a conventional machinists jack on a faceplate!

If you have 1-2-3 blocks consider making adapter studs so the jacks screw into the blocks. Sometimes you need a tall support.


Edited By Clive Foster on 17/11/2019 21:34:24

Edited By Clive Foster on 17/11/2019 21:35:45

old mart17/11/2019 21:46:29
1787 forum posts
138 photos

That's a good point, I had forgotten about the threads in 1-2-3 blocks.

IanT17/11/2019 22:27:33
1535 forum posts
144 photos
Posted by Clive Foster on 17/11/2019 21:33:58:

If you have 1-2-3 blocks consider making adapter studs so the jacks screw into the blocks. Sometimes you need a tall support.


That's an excellent idea Clive - I'll add it to my TUIT list and make some for my 1-2-3 blocks...thank you.



Chris Evans 618/11/2019 07:45:57
1666 forum posts

Over the years I have made many jacks, some fancy tapered turned affairs others just a rectangular block. Before then I pressed a tee nut into service with a suitable bolt.

Circlip18/11/2019 10:16:56
1106 forum posts

Can also be used as adjustable "Slip gauges" (use a mic to set the height) for a sine bar, unless you're working for NASA.

Regards Ian.

Vic18/11/2019 10:35:57
2500 forum posts
14 photos

Sadly I don’t have a faceplate for my lathe so not an issue for me. Hopefully I’m out in the shed today to make a V block with a spigot to fit the hole I’ll be drilling in the hex bolts. Good idea about the adapter for use on 1-2-3 blocks but they have Imperial threads. Luckily I have some Stevenson's Metric Blocks tapped M8 so I can use those. I need to make some M12 - M8 adapters now ... And there I was thinking it was a quick and easy solution! laugh

Edit: Yes thanks for the idea Clive. wink

Edited By Vic on 18/11/2019 10:37:28

Chris Evans 618/11/2019 12:28:38
1666 forum posts

M12/M8 adaptors available commercially for pennies. Not worth the effort to set up.

Vic18/11/2019 19:34:44
2500 forum posts
14 photos
Posted by Chris Evans 6 on 18/11/2019 12:28:38:

M12/M8 adaptors available commercially for pennies. Not worth the effort to set up.

I might normally agree with you but I’ve already got 5 metres of 12mm threaded rod sitting in the shed. It will only take me a few minutes to put an M8 thread on a couple of bits. I only want two.

not done it yet18/11/2019 19:45:55
4659 forum posts
16 photos

1-2-3 blocks will usually only need a set screw and a locking nut, for adjustable height, + something to secure the block to the faceplate.

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