Preferred slot for mounting a rear toolpost on the Myford S7 Cross slide

Hi - Using a rear mounted parting-off tool on my Myford S7 has recently got me wondering which should be the preferred slot for attaching the tool (base measurement 2”x2"  ) to the cross slide. I have always made the practice of mounting it in the rear most slot largely because it provides more room around the chuck which in turn allows it to remain in place whilst performing other operations. The down side is that I have sometimes noticed that on removing the tool, the cross slide leadscrew can sometimes show signs of stiffening-up which rapidly disappears on usage but might suggest that it could be a result of over tightening. As a result I have taken to mounting the tool in the second slot back from the rear when possible but of course things can get a little cramped in the process. Does anyone have any thoughts on the matter? I should add that I am always very careful in tightening up on the lathe in order to protect the potentially vulnerable ‘T’ slots.

Edited By JasonB on 27/11/2021 10:02:15

I wonder if what you are seeing is actually that the cross-slide is being lifted against its dovetails when parting and slightly jamming because the gibs are a bit loose?

Edited By JasonB on 27/11/2021 10:02:57

"Tee slot" in the singular, so i assume you are not using the GHT pattern which mounts to the *two* rear slots which is I think a better way of mounting the toolpost (I didn't understand your "rdqo" reference).

Gentlemen,

ALWAYS type a space before a right-hand bracket. This avoids waking up the smiley gremlin.

Best regards,

Swarf, Mostly!

Edited By Swarf, Mostly! on 27/11/2021 09:29:42

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The perils of trying to compose stuff in an HTML environment

This entry supports Rob’s analysis: **LINK** : https://www.toptal.com/designers/htmlarrows/punctuation/right-double-quotation-mark/

MichaelG.

Grindstone Cowboy:

Thanks. Jason's edit confirms.

2"x2" sounds like a generous section but I prefer the two slot design with a "toe" for the nearer slot.

I recall Martin Cleeve describing a jam which caused his toolpost to be torn from its location and hurled across the workshop; this led him to fit a steel cross slide to his ML7.

Greensands

I use a late Myford rear tool post for parting off. It is clamped to the slide using three bolts, two into one tee slot and a long bolt, that clamps the swivelling head of the post, into the adjacent slot. Like you I use the furthest slots to give space on the slide. I have never had any difficulties with this arrangement.

I know that the slide is not very stiff and have had problems clamping parts, for boring or facing with a fly cutting, to it. I found that the slide can get stiff if you don't think about what you are doing.

Perhaps you could post a photograph of the arrangement in you album.

Just an aside, I have not be able to understand G H Thomas's explanation of the rear tool post for parting off. The more I think about it, mounting the tool up side down allows the swarf to fall away and not get trapped in the slot being formed during parting off.

JA

Posted before seeing ega's reply,

Edited By JA on 27/11/2021 12:53:16

Mount it in the slot which does not require a lot of knob twiddling between turning and parting, having said that 2 slots are better than one and with the long crosslide you still have two choices of position.

A couple of pics showing the rear toolpost holder

I keep mine in the rear slot and do not have the problem that you having so maybe it is the cross slide

H

A 'long' T nut may help. Essentially a length of T profile bar to spread the load. There are modigied designs for that parting toolpost which has an extended 'thick lip' at the front to pick up on another T slot and to extend the footprint of the toolpost making the whole thing more stable.

regards Martin

I'm with Martin Kyte on the benifits of using 2 tee slots for greater stiffness. The rear toolpost I made for the Smart & Brown model A has to be bolted directly to the cross slide as there are no slots, but I made it as long as possible to lower the profile for stiffness.

I don't like the idea of a single bolt fixing. I think it would be done up quite tight to prevent the post turning during use. I am very aware of this on my set-up.

Is the base of your tool post and surface of the cross slide truely flat? If not the slide would distort when the tool post bolt is tightened. The fact that the problem occurs when mounted in the end slot, where the slide is less rigid, would suggest this is happening.

My set-up, shown, is left on the lathe unless I have to take it off.

JA

The old Myford pattern was held by a single stud but had a tenon which fitted into the tee slot and prevented the post from turning.