compond bolt down mod?

[mike rolly]

Fellers,

How do people do the bolt down compound mod on a lathe if the cross slide has no T slots?

Every site I have looked at uses the T slots in the cross slide for clamping down the compound slide.

Any suggestions?

I have a mill, would it be possible to machine two T slots in the cross slide?

Cheers.

Mike

[pipeclay]

Are you trying to bolt down the Compound or Cross Slide.

If its the Compound it is normally attached to the Cross Slide by dovetails and a Gib,there is sometimes provision to lock the dovetail slide.

[Michael G]

Mike, I'm a bit confused about what you are trying to do. Can you post a photo or two? It sounds like you have a vertical slide that you want to attach to the cross slide for milling purposes.
I wouldn't advise milling T slots in a lathe cross slide if it does not have them as you run the risk of significantly weakening it. The previous lathe that I had did not have T slots but the former owner got around that by making up a dummy T slot table that bolted onto the slide. I never used it, preferring to transfer things to a mill if I needed to machine.

Michael

[mike rolly]

This is what I am trying to do: Steve Bedair's 9x20 Lathe Site

However, my cross slide does not have the T slots for the mounting of the four bolts.

Trying to improve the rigidity of my top slide, I have seen and measured flex under cuts.


Mike

[Greg Q]

Well then yes, if your cross slide has enough meat to machine the slots why not? Mill a groove first then use your tee slot cutter to clean up the under cut.

Greg

[snowyskiesau]

What model lathe do you have?

I have a similar problem with my lathe (H&F AL60, Sieg C6) in that there are no T-slots.

[Dave J]

Fred (Big Shed) from here did some mods to his compound, it should come up under a search.

Dave

[Michael G]

I'm still concerned that if you machine the cross slide to put in T slots you will end up weakening the thing. I don't know whether your cross slide is steel or cast iron, but either way I'd want a bare minimum of at least 8mm of thickness in there.
Good surface finish and accuracy on machine tools depends a lot on rigidity (particularly when using inserts). A full length slot will be a weak point that will allow flex. I can imagine that if you get a dig with the tool the forces are enough that it would flex a bit on the T/S side. CI in particular is not as good with tension and so could also (eventually) crack through.
Looking at Steve Bedair's page, I couldn't see any explanation of why he felt this mod was needed or what is gained from it. Is it to get extra clamping to hold the compound to the cross slide, or is it to get more adjustment for the tool post position? My current lathe is the only one I've ever owned with a tool post T slot and although I can't say it's never been moved, it rarely is. If you are wanting improved clamping 4 tapped holes may be a better option.
If you really wanted to do this mod, my thoughts would be to buy a slab of steel and make up a new cross slide, allowing extra thickness for T slots. The penalty will be a reduced swing over the cross slide though. These machines are made to a price - as it is, the cross slide is probably contains the minimum amount of material (that is, has been made as thin as possible) consistent with accuracy & rigidity expectations.
Michael

[mike rolly]

Thanks for the replies fellers.

I appreciate Michael G's comments on the downside of milling T slots, I will not go this route now.

Options now are to either drill and tap 4 holes and use a clamping system to hold the compound to the cross slide. The degree wheel is part of my compound slide.

The other option is to remove the compound and top slide and install the QCTP to the cross slide. I have seen a mod like this called the 'plinth'.

Have a Happy New Year too fellers

Mike