Toolpost clamp bolt for a QC Toolholder ML7

[spike47Participant @spike47]

Hi

I have just received  a quick change tool holder for my Myford ML7,but it will not fit my lathe, the centre clamp bolt on my lathe is 7/16″ ( arounf 11.2mm).

The Quick change I have got has a tapered hole for the clamp bolt to fit, it goes from 10mm at the bottome to 8mm at the top.

Question can you get a clamp bolt to fit this tool holder for my ML7 ?.

Cheers

Spike

[bernard towersParticipant @bernardtowers37738]

Machine it out to fit

[FulmenParticipant @fulmen]

Yup, that’s it.

[spike47Participant @spike47]

Yes I could do that, but I was trying to find a taper bolt to fit  to keep the quick change has it is !

[Clive FosterParticipant @clivefoster55965]

$64,000 question is whether or not the post is hardened. If it isn’t drilling out should be straightforward. If it is you may have no option other than making an M8 bolt / stud to suit. As the hole is tapered from 10 to 8 mm If you decide to use a stud it might be worth making it stepped to exploit the larger part at the bottom of the hole for a stronger stud.

If you do decide to work on the tool post best practice is generally considered to counter bore a suitable diameter both ends to a depth of around 1/4″. Bottom counterbore ensures that the post isn’t seating only at the centre due to the slide surface not being perfectly flat. The cast iron does tend to rise around any tapped holes under the influence of many stud/bolt tightenings over the years leaving slightly conical distortion. Ideally the tool post contact area should be well out towards the edge giving the most leverage against turning. On a Myford I imagine a circular contact area approaching 3/4 inch wide should be ample. The counterbore at the bottom allows the stud to be made with a reasonably wide rim at the end both the thread giving a more positive bolt down than simply running to the end of the thread. Allegedly this also reduces the cast iron rising around the thread tendencies. I’m unconvinced.

At the top end best practice is considered to be using a thick top hat shaped spacer/washer a nice but free fit in both counterbore and on the stud. The washer / spacer actually locates the tool post the hole in the middle having significant clearance around the stud. The idea being to ensure clean clamping off the surfaces of the tool post with no possibility of the stud binding in the middle.

It’s all bait inspector meticulous really. Having had to sort out ill behaved tool post in the past for other folk. A frustrating exercise. I follow the rules for my own machines to make sure I don’t have trouble. But I’ve little doubt that careful workmanship with a simpler approach will, almost always, work just fine.

Clive

[Paul LousickParticipant @paullousick59116]

How does the tapered bolt design for holding the toolpost work ?

I understand that a tapered pin will provide good location sideways but how do you clamp the toolpost to the top slide?  I have a Southbend lathe which uses a straight stud with a nut on top to hold the toolpost. It came with a 4-way toolpost and I have just fitted an Aloris quick change type. Both have a straight hole thru them, allowing the toolpost to slide up and down and for the clamp nut to work.

 

 

[JasonBModerator @jasonb]

To me the quick change is provided by the cap head screw in the side which opens and closes the dovetail allowing the tool holder to be changed. The hole in the middle simply clamps th emain block to the topslide.

 

As said bore it out which will probably need a carbide insert boring bar and post in the 4-jaw as the hardening which is not usually that hard may defeat an HSS drill. That will be easier than making a smaller replacement stud for the Myford.

Chester sell this style for the Minilathe which is similar height to a myford.

Small Quick Change Tool Post

[BazyleParticipant @bazyle]

Are you sure it is tapered and not stepped. May have been more than one supplier but mine is 10mm straight bore with one side opened out to 20mm about 8mm deep by the previous owner. As suggested by someone above I was able to just make a locating washer for this larger recess (small lathe so post fitted loosely). The body was not hardened but a quick file check will tell you.

[Paul LousickParticipant @paullousick59116]

Hi Jason, I was referring to the middle hole that clamps the block to the topslide, not the dovetail clamp screw. The lathe has a 7/16″ bolt.

“The OP said that the Quick change I have got has a tapered hole for the clamp bolt to fit, it goes from 10mm at the bottom to 8mm at the top.”  How do you clamp down on a taper pin ?

[BazyleParticipant @bazyle]

Another thing – check which way round you want it if you do a recess on one side only. In fact I really must make a matching one on the other face so I can turn it upside down. Looking at the Chester advert it is actually upside down so the clamp screw is away from you when set up for normal turning and will hit the workpiece. However when boring you do want it that side so it is at the tailstock end when operating. This is the one downside of this style. (in my configuration)

It is a little bit small for the Myford if you are one of those people who think you have to use half inch toolbits on a lathe designed for 1/4″.

[Paul Lousick]

On Paul Lousick Said:

Hi Jason, I was referring to the middle hole that clamps the block to the topslide, not the dovetail clamp screw. The lathe has a 7/16″ bolt.

“The OP said that the Quick change I have got has a tapered hole for the clamp bolt to fit, it goes from 10mm at the bottom to 8mm at the top.”  How do you clamp down on a taper pin ?

That hole has nothing to do with the quick release. Even if it were intende dto clamp down onto a tapered pin how would you get it back up and off the taper to alter the posts position?

As has been said you can either bore it out to just clear the Myford stud or make a new stud with a reduced diameter to clear the 8mm hole and put an M8 or 5/16″ thread on the end. Similar to this one sold to fit other types of QCTP to old imperial Myfords

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