Thread: Lathe Gib lock on the cross slide covered by DRO scale

Lathe Gib lock on the cross slide

My lathe DRO scale covers the cross slide gib lock screw. There are times I want to lock the cross slide. I thought maybe place some grub screws on the opposite side made out of brass or something which will not damage the cross slide v.


On my previous lathe the saddle lock bolt was removed by the manufacturer to allow the fitting of the DRO scale. Not good.

Here are some pictures.

Is the idea of adding soft grub screws reasonable? Is there another method to lock the cross slide?

Sincerely,
Tom

Even a soft grub screw might damage the dovetail, the lock screw pushes on the back of the gib and wont damage a sliding surface.
Mine is the same, so far only once I needed the lock but I got away with firming up the gib and holding the cross feed dial while cutting,

Schaublin clamp the whole cross slide with a simple clamp that pushes the whole cross slide onto it's ways. Might be worth looking at copying that. I think the 135 is the easiest to see it on.

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Originally Posted by caskwarrior

Schaublin clamp the whole cross slide with a simple clamp that pushes the whole cross slide onto it's ways. Might be worth looking at copying that. I think the 135 is the easiest to see it on.

Sent from my SM-G973F using Tapatalk

Good idea Ralph, a bracket could be made to do that and bolt it to where the traveling steady bolts on.

I took these pictures for another member recently fitting a DRO.

What I did probably 15 years ago was to machine a wide V out of the backing plate leaving about 1mm from my 6mm home made backing plate.

I then made a cover with a finger groove ( made witha end mill) to get it out. The cover stops crap getting down there.

While your there add a ball bearing between you wedge peice and the bolt with a drilled divot in the end of the bolt to seat the bearing, I've done this to everyone of my gib locks and makes the locking so smooth.

This mod allows you to use a M6 bolt with a slimmed down head thickness.
A cheap $2 spanner is fine and if it's to wide grind it down in thickness.

If you want better pictures etc let me know.

2nd picture

3rd picture as Tapatalk doesn't allow more than one picture unless you pay

Last one

I'm the other member that Dave mentioned.
Just fitted a DRO to my little McMillan. I ended up drilling and tapping a new hole on the head stock side of the cross slide for the lock. Instead of using a soft grub screw I just used a bit of brass (tobin bronze brazing rod actually) with the end filed to the same angle as the dovetail. It goes in the hole and the grub screw pushes on it. For the amount of use I will give it, I don't think it will cause any noticeable wear or damage in my lifetime.

lock pin.jpg

Peter

We often hear from the political class about the education revolution, but these forums are the real education revolution. Wonderful responses which have given me much to consider. Thank you, regards, Tom

Originally Posted by bollie7

I'm the other member that Dave mentioned.
Just fitted a DRO to my little McMillan. I ended up drilling and tapping a new hole on the head stock side of the cross slide for the lock. Instead of using a soft grub screw I just used a bit of brass (tobin bronze brazing rod actually) with the end filed to the same angle as the dovetail. It goes in the hole and the grub screw pushes on it. For the amount of use I will give it, I don't think it will cause any noticeable wear or damage in my lifetime.

lock pin.jpg

Peter

G/day bollie, I reckon that is a good job and will work fine on the McMillan but what Tom didn't tell you is that his lathe weighs about 1700 kgs and has a 7 1/2 hp motor, I dont think a little pin like that will cut the mustard when he is giving the lathe
a hammering.

Originally Posted by shedhappens

G/day bollie, I reckon that is a good job and will work fine on the McMillan but what Tom didn't tell you is that his lathe weighs about 1700 kgs and has a 7 1/2 hp motor, I dont think a little pin like that will cut the mustard when he is giving the lathe
a hammering.

You are probably right there too. I doubt if a machine that size would have a cross slide lock that small though. However, a suitably sized one (or even two) would still work if there was no alternative.
peter.

Originally Posted by shedhappens

G/day bollie, I reckon that is a good job and will work fine on the McMillan but what Tom didn't tell you is that his lathe weighs about 1700 kgs and has a 7 1/2 hp motor, I dont think a little pin like that will cut the mustard when he is giving the lathe
a hammering.

It would have a larger locking grub screw/bolt to lock it up I presume than mine and also have a tailstock that overhangs the crosslide unlike mine.

In that case you could use a wider backing plate 10-12mm thickness to accommodate the larger bolt to go with my idea.

Or use a aluminum block on each end of the scale to space a 6mm backing plate off the crosslide if you don't mind loosing the extra 10mm tailstock to crosslide distance, leaving a gap between the crosslide and backing plate to access the bolt head.
The backing plate only needed to keep coolant and swarf away from the back of the scale.

Originally Posted by bollie7

You are probably right there too. I doubt if a machine that size would have a cross slide lock that small though. However, a suitably sized one (or even two) would still work if there was no alternative.
peter.

I have just been thinking about this, the cross slide lock needs to press the front dovetails firmly together and that is why the lock presses on the gib that is at the rear, to press the front dovetails together as this is the direction of the load.
With the pin (or pins) at the front it would press the front cross slide dovetail away from the front saddle dovetail and as the saddle is feeding forwards the load from the saddle pushing the cross slide forward is being transferred by mostly only the surface area of that pin as it is forcing the dovetails apart.
Just thinking......

Originally Posted by Dave J

It would have a larger locking grub screw/bolt to lock it up I presume than mine and also have a tailstock that overhangs the crosslide unlike mine.

Dave my thick head hasn't caught on exactly how you have done this, at the mo it looks to me that your gizmo is locking the saddle????

Hi John, Guys,

I completely follow your logic, applying a locking screw to the non gibb side of the cross slide would have the effect of loosening the gibb strip and lifting the slide or pressing it down depending on which way the dovetail is.

The locking grub screws on my Myford bear on the middle of the two gibbs on the tailstock side of the cross slide. The one that is under the top slide is really awkward to get to.