Machinist Jacks

mksj said:
I have a much heavier lathe (2400lbs) with carbide inserts for turning, so my DOC is anywhere from 0.02-0.1" with a feed rate in the 0.009-0.012"/R range for 4140. As Firemaker76 outlined, it is easy to hit your target by measuring the diameter change vs. the DRO/Dial reading change and compensating with each successive cut. When threading this diameter I make a female test mandrel in this case it was aluminum and the male was some scrap steel rod. This gives you an approximate DOC when threading and also as a fitment guide for multiple parts (i.e. a go/no go for threading) On a smaller lathe I would recommend sticking with 1144 which is easier to machine and is very durable. You can often find ends on eBay or scrap at very reasonably prices, shipping is less if 12" or under. Example below I would get two (1-5/8 or 1-7/8" Steel Rod 1144 High-Strength x 6" Long Stressproof), or a smaller diameter as I am not sure your lathe can handle heavy turning. The bluing solution is below, it kind off works, took a number of coats and I cleaned, then boiled the metal in distilled water and applied hot. This was my first time bluing, but it depends on the steel and it needs to be very clean. After a couple of coats, lightly go over it with fine steel wool and then apply a coat of oil.

Firemaker76, very nice work and attention to detail, wish I had more patience for the finer details you did. Much better to make your own machinist jacks to your own design, far better than what you can buy.

www.ebay.com

1-5/8" Steel Rod 1144 High-Strength x 6" Long Stressproof | eBay

A311 Class B Stressproof A311 Class B StressProof® is a steel produced using a proprietary process that draws the bar through a special die under heavy draft. StressProof® round bar,hex and standard cold finished or TG&P (Turned, Ground and Polished).
www.ebay.com
www.ebay.com

1-7/8" Steel Rod 1144 High-Strength x 6" Long Stressproof | eBay

A311 Class B Stressproof A311 Class B StressProof® is a steel produced using a proprietary process that draws the bar through a special die under heavy draft. StressProof® round bar,hex and standard cold finished or TG&P (Turned, Ground and Polished).
www.ebay.com
www.ebay.com

NU-BLU GUN METAL BLUING 8 oz | eBay

NU-BLU Gun Bluing is not your average Cold Bluing, it is designed as a reverse Hot Bluing, without the need for dipping tubs and the use of gallons of product. This eliminates blotchy, inconsistent results.
www.ebay.com
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Thanks very much Mark. I appreciate your support. My lathe has been an absolute dream to work with, and that is thanks to all your help, direction, and wiring schematics when I rewired it.

-Mitch Humborg
 
firemaker76 said:
So another tool crossed off the 'To Do' list. Made a pair of machinist jacks, and wanted to post a few pics.
I started by turning down some 1.250" diameter Heat Treated 4140 and made the screw/head pieces first. That way I could measure my thread pitch and make sure it was within proper 2A specs. Then I drilled the top of the heads to accept some .375" diameter bushings with a .0005" press fit.
After that, I turned the jack bodies down to 1.200". With the screw threads already done and within specs, I was able to bore and thread the bodies 3/4-20 and get a very smooth and precise fit with zero slop. Then I turned some grooves along the outside of the bodies for aesthetics and better grip. These were parted off and faced to an OAL of 1.750".
The extensions are made 1.000" long with an upper shoulder for the body to sit on and a lower inner shoulder in case another extension needs to be added. The shoulders mated up very well.
Finally I made some caps and drilled and reamed the bottoms to .375". This allowed them to engage the head bushings and spin freely. I also put several varying-sized diameter grooves around the top and milled a .075" deep V-groove through the center of the cap. This allows smaller diameter stock to engage the groove and sit dead center when supported by the jack. I did not realize how handy and necessary these little jacks were, but I use them all the time now.
One more quick note...I also attached a magnified pic of some chips from the 4140. I spent more time trying to remove these little monsters from my shop broom than I did actually building the jacks. Now I know why LOL. Take a look at the teeth on those chips!

Thanks for reading guys and Happy Machining!! Be safe.
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I know this is a little late, but that is some awesome work, sir!
Great looking jacks!
 
What’s the double ended tool you used to get the circles machined in to the cap?


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Also, why did your thread from behind? Purely for a better shot with the camera? Or is there another purpose?


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Ben17484 said:
What’s the double ended tool you used to get the circles machined in to the cap?


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I am pretty sure that is a grooving tool.
Ben17484 said:
Also, why did your thread from behind? Purely for a better shot with the camera? Or is there another purpose?


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He set it up that way because he threaded away from the shoulder of the piece by running the lathe in reverse, thus eliminating the risk of crashing.
 
7milesup said:
I am pretty sure that is a grooving tool.

He set it up that way because he threaded away from the shoulder of the piece by running the lathe in reverse, thus eliminating the risk of crashing.
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When I search for grooving tool, I can either find a parting tool or an Internal grooving tool. I can’t seem to find one like in the picture here.

I had wondered if it was for threading away from the chuck, but doesn’t that require the tool to also be upside down?


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Ben17484 said:
When I search for grooving tool, I can either find a parting tool or an Internal grooving tool. I can’t seem to find one like in the picture here.

I had wondered if it was for threading away from the chuck, but doesn’t that require the tool to also be upside down?


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I agree with being unsure about the grooving tool. It is common to utilize a grooving tool/parting tool interchangeably, but during my search, I too was unable to find one like the OP was using.

Threading away from chuck. No, if the lathe is run in reverse the tool needs to be upright. If the lathe is run forward and the tool is on the backside, then it would need to be flipped upside down.
 
7milesup said:
I agree with being unsure about the grooving tool. It is common to utilize a grooving tool/parting tool interchangeably, but during my search, I too was unable to find one like the OP was using.

Threading away from chuck. No, if the lathe is run in reverse the tool needs to be upright. If the lathe is run forward and the tool is on the backside, then it would need to be flipped upside down.
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Ah, threading away with the lathe running in reverse. That makes sense. I’ll try that.


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Ben17484 said:
What’s the double ended tool you used to get the circles machined in to the cap?


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Hi Ben sorry for the late reply. So that is a threading and grooving insert and bar that I bought from Jim over at Mesa Tool. They are still listed on his website if you're interested.
 
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