Tool Post Nut

Hi,

I have just bought a quick change tool post for my myford ml7, to replace a cracked 4 way tool post.

However the old 4 way tool post had a locking handle instead of a nut, and this will not fit the new quick change tool post.

Do I just need a standard nut to hold the QCTP in place?

I noticed the myford site sells the nuts with a spherical washer (which I'm guessing isnt required?), but £5 for a nut seems a little excessive.

Cheers guys,

Kane

The standard nut is 7/16" BSF. I fitted a Dickson toolpost to my lathe, and made up a handle to suit.

Thank you Nigel!

One thing that confused me, the tool post came with a 'nut', it was like a cylindrical spacer with an internal thread, and a hexagon nut at the top.

This fits inside the central hole of the toolpost, but the thread was much too small to fit the stud in the top slide.

I thought it must just be a generic part that doesn't fit the myford (I emailed the manufacturer, but I don't think they will reply until next week).

Any ideas what it might be?

Thanks again for the quick reply.

Kane

Never bother to find out what the "generic part" was for, I just made up a spacer and continued to use the original handle

Hi Kane - here, as they say, is one I made earlier!

Thread the piece of rod to fit the tool post stud and insert a handle with a nice knob. Make up a thick washer to fit between the bottom of the rod and the body of the tool post. Adjust the thickness of this washer by trial and error until the new "nut" is tight when in the position shown. ( Quite a small amount removed will make quite a difference to the position of the handle) The advantage of this method is that it is quick to use and you will never need to search for that spanner amongst the swarf or in your pocket or.....

What's more it is aesthetically pleasing - well I think so anyway!

Regards

Norman

Edited By NJH on 24/03/2013 21:15:15

Thanks everyone, I think I have all the info I need!

That bit of kit looks ideal Norman. I'll definitely have a go at making one, but first I'll need to secure the toolpost with a nut before I can make anything.

I would never have thought about adjusting the thickness of the washer, but makes a lot of sense. Looks like I have plenty to learn!

Cheers

Kane

Kane,

You may also need a spacer/washer to fit down the 'ole in the toolpost to ensure it is a snug fit on the toolpost stud. It may already be so, these generic types do vary.

If you can't get a 7/16" BSF nut without paying a fiver, PM me and I'll send you one.

Phil

Hi Kane,

My S-7 came with a black painted triangular cast block with a height adjusting screw under one corner with a knurled disc fixed to middle of screw. The opposite side was a thicker, machined part which pressed the tool down upon the topslide. Centre of triangle had a hole where it fitted over the vertical stud mounted in the topslide. A light spring fitted on the stud under triangular tool clamp which was held down by special nut like you have described. Reason for curved underside of nut was so it fitted neatly in matching recess in top of tool clamp. This enabled varying angles of tool block to accomodate differing thicknesses of lathe tools and still provide secure clamping. Sorry this seems a bit long-winded but I wanted to describe whole attachment in detail. Hope this helps.

John

John,

That sounds like a description of the standard Myford toolpost clamp, like this

Phil

Kane,

On my S7 I use the 4-way toolpost locking lever with the QCTP. The toolpost is located on the topslide stud with a shouldered washer. Some pics below:

Shouldered washer

Toolpost over stud

Locating washer in place.

The position of the locking handle is determined by the thickness of an additional washer:

With additional spacing washer.

Finally, the locking lever is screwed on until it interferes with the locking pins for the tool holder and then the whole lot is rotated until the locking lever becomes tight - some trial and error is needed to get spacing washer (or washers) of the correct thickness thicknes so that the locking lever is in the right place.

I find it very useful to able to easily adjust the angle of the tool using by rotating the QCTP slightly.

HTH

Rod

Robbo.

You are quite correct, but my post actually started with "My S-7" etc.

John

I have been educated! Thank you guys, lots here for me to think about. Absolutely fed up of my knob (uh-hum) facing towars the chuck

Cheers David.

Hi Kane,
If you want to know how much to reduce the thickness of the washer this is how to work it out.
This is for 7/16 BSF thread.
7/16 BSF is 18 TPI 1/18 = 0.0555"
So 1 degree of rotation of the nut is 1/(18 x 360) = 1/6480 = 0.00015432"
So for every degree you want the handle to move clockwise (Direction to tighten) remove 0.00015432" from the thickness of the washer. So if you wanted the handle to move 90 degrees clockwise you would need to make the washer thiner by 0.00015432 x 90 = 0.0138888"
(About 14 thou)
If you want to make a washer from scratch then the thickness needs to be
N x 0.0555" + A x 0.00015432"
N is any integer. A is the number of degrees you want the handle to move ANTICLOCKWISE from its position without any washer.

Les.

Hi Les

Well that's a comprehensive way of deciding just how much to remove! I confess to using the trial and error method but I got there in a couple of cuts! I should just point out that my original post may have been a little confusing in that I talked about a "washer". Now I guess a washer is usually thought of as being quite thin and, once parted off, will be a bit tricky to rechuck. It's much easier to make it thicker and, if you look carefully at my photo, you will see that I made mine about 1/2 inch thick - works just as well, and enables easy rechucking to get just the right thickness. Maybe I should call it a "spacer" rather than a washer!

Cheers

Norman

Hi Norman,
Like you I would have just have used the trial and error method. My main reason for this post was to get the OP to think about how things work (Threads in this case.) Threre was a comment earlier in this thread that someone had not thought about adding washers which made me think they did not even think about how a thread works. I thought showing the calculation would get them in the frame of mind to think about how things work when trying to solve a problem. I think that thinking this way is needed to work out the best way to do a job using the equipment available. A recent example of someone not thinking how something works was someone I know who had a problem with water leaking from a compression joint. He said he put PTFE tape around the thread. He had not thought that the olive makes the seal and the thread only holds the parts together.

Les.

Thank you everyone for your excellent advice.

I got hold of a 7/16" BSF nut and got the tool post mounted.

However I now have a problem with not being able to adjust the tool holder low enough to get the 3/8" HSS bit to centre height, as it bottoms out on the top slide.

I guess the best option would be to mill the bottom of the tool holder down, but without a mill this may be tricky? Are the holders usually hardened?

Is it possible to just grind the top of the lathe tool down further? It would need about 1-2mm taking off. Would this be ok?

I thought about buying some smaller (8mm) HSS blanks, but don't know if these will be too small for the holder.

Any advice appreciated.

Cheers.

Kane

Hi Kane,
I think I have the same QCTP as you have which I ftted to my Chester DB10G lathe. It looks the same and was sold by Chronos to fit a myford ML7 / S7 lathe. Next time I go down to my shed I will run a file over the bottom of one of the tool holders to see if it is hardened. If it is not you could file it down. If it is hardened you could face it off in you lathe using a carbide tool. Even if you do not have a 4 jaw chuck I think you could mount it using a 3 jaw chuck. Bare in mind that thinning the holder under the tool will weaken it to some extent nullifying your desire to use 3/8" tool bits to gain rigidity over 5/16"
I would have thought an your size of lathe 5/16" tooling would be rigid enough. There is no reason why you should not grind the top of an HSS tool to get the correct centre height. This would occure any way after sharpening the bit a number of times. It would not be a good idea to grind much off the top of a brazed tip carbide tool as it might leave the tip too thin. (You would not normaly take much off the top of a carbide tool when sharpenning.)

Les.

Great thanks Les.

If it's not a problem grinding the tool down further, I think this will be my first choice.

I do have a 4 jaw, but facing could be a problem without a toolholder haha. I was also concerned about how much it would weaken the holder.

Kane

I does seem daft to me to have a handle at all on the fixing nut which just gets in the way. It's not as if you are moving the block every five minutes like you would a 4-way which seems to be where the idea came from.
From the earlier picture of a toolpost the holder locking nut which you do want to use every five minutes has a removable handle and the other doesn't - it's the wrong way round. I suggest you stick with the nut and if you really need to release it that often make a special spanner from a tight fitting socket. that you can leave on.

Kane,

Had the same problem when I foolishly bought a replaceable tip holder which was too thick so couldn't drop the tool holder down far enough to get it on centre before it bottomed on the top slide.

I milled a few mm off the BOTTOM of the tool so it lowered the tip in relation to the holder, no problem milling, solved the problem.

My quick answer to the tool post spanner dilemma was to use a box spanner with a permanent tommy bar fixed in it, and the unused socket on the other end of the box was sawn off!

Imperial box spanners are like gold these days, but an 18mm will be a snug fit, especially as the tool post nut is extra long.

Phil

Edited By Robbo on 29/03/2013 12:08:01