4 Bolt Compound Clamp for 9x20 Lathe

[Big Shed]

One of the well known weak points of the 9x20 lathe, extensively documented on the internet, is the 2 bolt compound clamp. I was very well aware of this when I bought the lathe and it was going to be one of my first upgrades to the lathe after I bought it.

For various reasons I haven't got around to it until this week. I finally got a bit sick of the movement in the compound and decided to bite the bullet. I have looked at the various solutions that people have come up with and decided on the "donut" by John Pitkin from the Yahoo 9x20Lathe group.

Some time ago I picked up a 115x20 piece of "steel" at a garage sale and it has been staring me in the face ever since. Was I in for a surprise when I put this piece of "steel" on the lathe, talk about hard!

Don't really know what it is, it had some rust on it, but didn't seem to like to be cut with HSS.

First drilled a 10mm hole and mounted a 10mm bolt in the 3 jaw chuck, faced off one side, used my carbide tipped tools and achieved a beautiful finish off the tool but could only do about 0.3-0.4mm cuts, so the job took a while!



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After facing one side, which wasn't very straight to start off with, I then reduced the diameter to close to the required final OD, 3.9" or 89mm.


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Next, a step had to be cut for the hold down clamps, this design doesn't use bolts through the base plate like most 4 bolt clamp designs.




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Remounted and about to face the other side




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Next a recess had to be cut to take the base of the compound slide, again a very slow job with small cuts each time.



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Marking out the holes for the socket heads (M6x1x10mm) to hold the compound slide, replacing the original soft machine screws. The original base can be seen in the background, the new one is somewhat larger and more substantial!





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Compound slide fitted and shown on cross slide.


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Clamps made and the whole in place on the cross slide. I will probably do the clamps again as I think they could go further over the base.


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The difference in operation of the lathe is astounding, far easier to take the compound on and off the lathe, achieving a much better finish as all flex has now been eliminated from the compound slide

[snowyskiesau]

Looks good. :2tsup:
It's prompted me to look at doing the same to my (Sieg C6) lathe.
The problem with mine is that the compound does not mount in t-slots as yours does. Instead there are just two mounting holes into the cross slide .

[Dave J]

Hi Big Shed,
I have heard of the 4 bolt conversion many times and seen the topics on a lot of forums but never really new exactly what they were talking about, so thanks for explaining it.
You and that little lathe do some nice machining, that piece of steel came out great.:2tsup:even if it did take some time.
Do you have any plans to engrave it for the degree markings?

I wish the 12 x 36 lathes came with a cross slide like that, for some jobs I could do with moving the compound further in. When I try to do a 45 deg corner on something small with the compound to the right, the cross slide nearly winds off the thread.

Just a suggestion with your new clamps,
If you can move the outside leg away as for as possible it will give greater force on the new base. I drew up a quick picture of a design to show you what I was thinking would give more down force.


http://www.woodworkforums.com/attachment.php?attachmentid=152273&stc=1&d=1289048692

Dave

[Big Shed]

Looks good. :2tsup:
It's prompted me to look at doing the same to my (Sieg C6) lathe.
The problem with mine is that the compound does not mount in t-slots as yours does. Instead there are just two mounting holes into the cross slide .

Thanks Geoff.

The base of your compound looks very similar to the original on mine.

It should be possible to do something similar on your cross slide, couldn't you drill and tap 2 additional holes at 12 and 6 o'clock? The you could use the any of the 4 bolt clamp designs that are on the internet.

[Big Shed]

Hi Big Shed,
I have heard of the 4 bolt conversion many times and seen the topics on a lot of forums but never really new exactly what they were talking about, so thanks for explaining it.
You and that little lathe do some nice machining, that piece of steel came out great.:2tsup:even if it did take some time.
Do you have any plans to engrave it for the degree markings?

I wish the 12 x 36 lathes came with a cross slide like that, for some jobs I could do with moving the compound further in. When I try to do a 45 deg corner on something small with the compound to the right, the cross slide nearly winds off the thread.

Just a suggestion with your new clamps,
If you can move the outside leg away as for as possible it will give greater force on the new base. I drew up a quick picture of a design to show you what I was thinking would give more down force.


Dave

Thanks for that Dave. Yes, am thinking about engraving degree markings, two problems with that though. First is that the material is pretty hard and blunts HSS rapidly, secondly I don't have a decent indexing system on either my lathe or my little X2 mill.

Your clamp design looks good and I will keep it in mind for when I re-do mine:2tsup:

[snowyskiesau]

Thanks for that Dave. Yes, am thinking about engraving degree markings, two problems with that though. First is that the material is pretty hard and blunts HSS rapidly, secondly I don't have a decent indexing system on either my lathe or my little X2 mill.


Fred,
Obviously your next project needs to be to CNC your rotary table so you can do the engraving.
There's a thread over at MadModder (http://madmodder.net/index.php?topic=2242.0) where someone is doing just that. The electronics and software are all open source.
Of course if you don't have a rotary table, forget I mentioned it :)

[snowyskiesau]

It should be possible to do something similar on your cross slide, couldn't you drill and tap 2 additional holes at 12 and 6 o'clock? The you could use the any of the 4 bolt clamp designs that are on the internet.

I don't think the material is thick enough to have threaded holes at the 12 and 6 o'clock positions. It's a lot thinner there due to the lead screw that runs down the centre.
I could drill two holes at the same width a little further up the body of the cross slide. Then I could make the base of the new compound mount square and still have a 4 hole mounting.

[Big Shed]

Fred,
Obviously your next project needs to be to CNC your rotary table so you can do the engraving.
There's a thread over at MadModder (http://madmodder.net/index.php?topic=2242.0) where someone is doing just that. The electronics and software are all open source.
Of course if you don't have a rotary table, forget I mentioned it :)

Spot on, I don't have a rotary table!:D

The dollar may well be at parity, but my bank account is well below par:o

A rotary table has been on my wish list for as long as I have had the X2 mill. Basically I have not bought one because I'm still not sure whether to stick with the X2 or to upgrade to a larger mill. If I do the 4" rotary table that will only fit the X2 would have to be upgraded to a 6".

[Big Shed]

I don't think the material is thick enough to have threaded holes at the 12 and 6 o'clock positions. It's a lot thinner there due to the lead screw that runs down the centre.
I could drill two holes at the same width a little further up the body of the cross slide. Then I could make the base of the new compound mount square and still have a 4 hole mounting.

I reckon that would be a better idea Geoff, have a look at Steve Bedairs' site, he has the square 4 bolt clamp there.

I am looking at making another one with a square base that doesn't use the compound slide, just the QCTP, as per the design on page 8 of Tricking Out the 9x20 Lathe (http://www.akpilot.net/Lathe%20Links.html).

Also looking at adding a locking bolt to the compound slide.

[Big Shed]

Here (http://www.wcc.net/%7Ejkmccoy/shop/9x20.htm) is a design that might suit your cross slide better Geoff.

[Stustoys]

Nice Big Shed
Took me awhile to find out what was originally on your machine. (must be blind)
You've reminded me that I need machine the bottom face of my compound.
That guy sounds like me "I needed a lathe (and a milling machine (http://www.wcc.net/~jkmccoy/shop/millpage.htm)). I didn't just "want" them, I needed them. How could I possibly build a thingamajig or a doohicky, or any of those other really important projects, without these machines?" except I got a shaper as well lol

Stuart

[snowyskiesau]

Here (http://www.wcc.net/%7Ejkmccoy/shop/9x20.htm) is a design that might suit your cross slide better Geoff.

That one looks about right.
I'll add it to the list of 'things to do one day' - First, finish off the DRO for the mill.

[Big Shed]

Just a heads up. Have been using the lathe with the new 4 bolt compound clamp and it has made a big difference, especially with parting off.

Haven't had one "dig-in" since I installed this, much more robust now, well worth the time and effort.:2tsup:

[Dave J]

Good to hear that it's better.:2tsup:

Just thinking out loud.
I think it would be even more rigid if you made some new clamps up. The way those ones are sitting it maybe be bending the bolts a bit.

Dave

[Damo72]

I made the rectangular one from the plans off Steve Bedairs' site as about the job on my 9x20 - didn't have any really suitable material and ended up using an old towbar toungue. It had a couple of bolt holes so doesn't look real pretty but is much more ridgid than the original. Though I did find that a lot of teh flex I was seeing when parting was coming from the compound-slide gibs. I checked them when setting the lathe up on the bench but they came loose (wearing in maybe??) very quickly and i hadn't noticed and was blaming the flex on the compound clamp. Since I've re-adjusted them and started turning the compound to 90degrees when parting things are a lot smoother.