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

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Greensands26/11/2021 20:29:25
375 forum posts
49 photos

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

John Haine26/11/2021 21:58:26
4716 forum posts
273 photos
 

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

ega26/11/2021 22:34:40
2565 forum posts
203 photos

"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).

Swarf, Mostly!27/11/2021 09:28:49
682 forum posts
78 photos
Posted by Greensands on 27/11/2021 09:16:00:

SNIP. Text hould have read 2"x2" as suggested. Smiley unintended. SNIP.

SNIP.

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

Michael Gilligan27/11/2021 09:31:42
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20289 forum posts
1064 photos
Posted by Grindstone Cowboy on 26/11/2021 23:50:33:
Posted by ega on 26/11/2021 22:34:40:

...(I didn't understand your "rdqo" reference).

Pretty sure that was unintended and resulted from trying to write 2 inch by 2 inch followed by a closing bracket (hence the smiley as well).

Rob

.

The perils of trying to compose stuff in an HTML environment crying 2

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

MichaelG.

ega27/11/2021 12:33:10
2565 forum posts
203 photos

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.

JA27/11/2021 12:50:40
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1403 forum posts
81 photos

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

bernard towers27/11/2021 13:11:31
689 forum posts
141 photos

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.

Greensands27/11/2021 13:29:52
375 forum posts
49 photos

A couple of pics showing the rear toolpost holder

Harry Wilkes27/11/2021 18:43:54
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1371 forum posts
66 photos

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

H

Martin Kyte27/11/2021 18:55:17
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2790 forum posts
53 photos

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

old mart27/11/2021 21:24:45
3901 forum posts
268 photos

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.

_igp2498.jpg

JA28/11/2021 11:37:49
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1403 forum posts
81 photos

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.Rear tool post.jpg

JA

ega28/11/2021 11:46:38
2565 forum posts
203 photos

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.

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