First machinist jack. Questions...

[Ryanjax]

Made my first machinist jack. My plan was to make a a set that worked kinda like a starrett where they stack. Went fairly well but I have a couple questions.

I also need to get some bottoming taps.

When plunging in the end of the part to make a relief, what is the correct procedure or tool? I had the best luck with a boring bar but I don't believe it's correct.

How much pressure should I put on the knurling tool?

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[Bob Korves]

A boring bar does a good job, and you can make the recess the size you wish. For quick and dirty, you can use an end mill for a recess like that. If the hole in the middle is drilled first, you can use a standard end mill, does not have to be center cutting. Be aware, however, that end mills do not cut horizontal surfaces at the bottom of the recess, they are deeper at the O.D., slightly cone shaped.

 

[Ryanjax]

That makes me sense, need some room for the tool to cut. Seemed like they were just rubbing for me.

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[mikey]

For me, a simple turning tool or knife tool would make that relief cut easily. These tools can be fed into the center and fed out; you don't really need to drill a center hole if you prefer not to drill one.

As for how much feed pressure you need on the knurl, it depends on how much of a pattern you determine to be acceptable. A 90% depth is considered a full pattern and you determine that by applying enough pressure to almost form a sharp point on each knurled tooth.

 

[benmychree]

I like less than a sharp knurl for most things, take it up almost sharp, then lightly file to remove the burrs. I would agree with Mikey on the recessing tool.

 

[Bob Korves]

For me, a simple turning tool or knife tool would make that relief cut easily.

For a project like the jack, the turning tool will probably be the best choice. I would not try for a 90 degree angle plunge to depth, rather something less, maybe 45 or 60 degrees. If the jacks need to stack with each other, then match the rebate diameter and the corner angles on the bottom and on the top of the jack screw for a good fit. A small amount of radial play where they fit together is not a problem, better than a too tight fit.

 

[mikey]

For what it's worth, my Starrett jacks have a 90 degree shoulder at the edges, as do the extensions that fit into the bottom of the jack. I presume this is so the jack doesn't slip off the extension easily but I'm guessing. In any case, a turning or knife tool will cut whatever angle you wish with no problem.

 

[MarkM]

Here ya go! Vise alone and with swivel base.