PM 4224 Tool Rest Lock Handle

Re: PM 4224 Tool Rest Lock Handle

John C Lucas

I ha e had that happen fairly often with my Robust tool rest. Eer with the Pwermatic rests. Dont know why that is. Perhaps the Robust tool.post is harder. What i do when i know im going to take bigger cuts is to lock both handles. I dont know if the 2442 has 2 lockig handles.

Re: PM 4224 Tool Rest Lock Handle

Dick Coers

I've never understood how the lathe engineers think it's a good idea on locking the tool rest by hand turning a small diameter bolt with a plastic handle into the stem. I know, you have to keep the cost down. But on a big lathe like this one. another hundred dollars shouldn't get a push back on that improvement. Back in the day, I think it was Ellsworth, who used to teach to let your lathe bed get rusty so the tailstock would have a better purchase. Maybe let the tool rest shaft get rusty? You could also upgrade to a Oneway tool rest, no slippage with them!

Re: PM 4224 Tool Rest Lock Handle

John C Lucas

When the 3520 came out it had a fabulous tool rest lock. A screw in knob pushed against a brass insert that locked the tool post very ridgedly ad would not marr it. Then they shifted production to Taiwan and some changed the design to a hollow screw with a brass insert. They had lots of broken s rews because the hollow screw just couldnt take the force. Then they put the solid screws in they have now. Those were on the A and B series. Now with the 3520C they have gone to a pinch style lock that should be much better

Re: PM 4224 Tool Rest Lock Handle

John K Jordan

A couple of things come to mind. One, switch to a hardened bolt and use a Dremel to grind a small concavity on the end. This would eventually mar up the tool post shaft. Two, mar up the tool post shaft on purpose to give the existing bolt something to grip. Not for everyone!

Or modify the existing bolt to accept a brass tip like Sir Lucas mentioned? That sounds best to me. Perhaps make a brass tip with a hole in one end and machine or hand grind a tenon on the end of the bolt to fit or jam into the tip. To prevent a loose tip from interfering when inserting a tool rest post I might try making the tenon tight or use a touch of sliver solder or epoxy.

JKJ

Re: PM 4224 Tool Rest Lock Handle

john lucas

John I would silver solder the brass tip in. Powermatic drilled along hole and put a spring loaded brass pin in. Don't remember how the kept in in there it's been too long but it was not a good design. I've had my Powermatic for 13 or 14 years and only seldom do I have the problem of the tool rest coming loose. Usually it's because I simply didn't apply enough pressure on the locking knob.

Forget about the brass tip because....

JamieDonaldson

.....with use it will just fall out among the shavings and be lost. I've seen banjo post hole assembles drilled and tapped for a second lock screw/handle, or a larger hole drilled and tapped in the rest holder, and substantial metal locking handle added. These can be ordered from MSC last time I searched.

Re: PM 4224 Tool Rest Lock Handle

Keith Newton

When I built my big lathe, I just used a 5/16 hardened bolt, that I bent to make the handle. It worked ok for a while, but needed to be larger, so I drilled it out and replaced with 3/8 and a longer handle. I ground the tip to length so it engaged where I wanted the handle pointing. When I want to make sure it won't slip, I flip my tool and give the bolt a quick tap with the tool handle.

Re: PM 4224 Tool Rest Lock Handle

John K Jordan

>>>When I want to make sure it won't slip, ...

Can't remember the last time I didn't care if the tool rest slipped.

Should? work better?

Brian Roberts

Of course the pinch style will work better!

If it's like the one used for YEARS on the PM45 it works like a dream!!

Should never have been changed.

Re: Should? work better?

John K Jordan

What does the pinch mechanism look like, how does it pinch? Could a tool post be retrofitted with a similar function with some machining?

JKJ

Re: Should? work better?

Brian Roberts

The first pic is of the banjo on my old PM45.

Second pic is of the split nut, screw, and handle I duplicated to use in the tool rest extension I made when I raised the head and tail stock on the PM45.

Third pic is said extention...which works like a charm.

To retrofit...

Brian Roberts

the banjo on the 3520b would involve machining a sizeable flat on the area that the tool post fits into to allow attaching enough extra material to fit the cross hole for the split nut.

You can see in the pic of the PM45 how the hole for the split nut is placed in relation to the tool post hole.

VERY simple system that worked VERY well...but of course was more expensive to produce than a single drilled and tapped hole....which works for crap....at best.

Re: Should? work better?

John K Jordan

Ah, thanks. That's exactly the type of column lock used on one of my milling machines.

That's some substantial machining on your extension, nice idea and nice job.

One way to retrofit for any lathe then might be to adapt what you did. Instead of an extending the banjo perhaps one could machine a similar block and split nut and fasten it to a shortened banjo. Offsetting the block like you did with a shorter post might limit the positioning and have other problems but I can think of a couple of ways to get around it, the simplest probably to just braze the block to the top of the shortened banjo leaving the tool post hole in the original post position.

JKJ

Thanks John....I have

Brian Roberts

been tossing a few different ideas around.....of course doing something

irreversible to the banjo gives me pause to keep thinking!

Any ideas are welcome.....

modifying banjo

John K Jordan

>>>doing something irreversible to the banjo gives me pause to keep thinking!

Any ideas are welcome.....

One idea: get a second banjo and modify one. Occasionally I really wish I had a second banjo, for example to make a very long tool rest for spindles.

JKJ