Granite Lathe Platform

A thought struck me, so I thought I'd ask the wiser machinists than I (and that would be all other machinists). I recently replaced my Grizzly G0516 bench lathe with a larger Busy Bee B2227L bench lathe.

I will be mounting the lathe to a workbench that I built using a section of warehouse pallet racking, 8 feet long by 3ft wide. The deck of the workbench is two layers of 2"x6" tongue & groove planks fastened together with wood screws every 6" or so. The bench weighs about 700 pounds and is very, very solid.

The Grizzly G0516 lathe has two pedestals for the lathe bed, with a gap underneath. (http://www.grizzly.com/products/G0516/images/1)

I mounted the G0516 lathe to two sections of 4"x6"x3/8" rectangular steel tubing which was in turn bolted to the work bench.

The new Busy bee B2227L lathe (http://www.busybeetools.com/products/LATHE-METAL-10IN.-X-18IN.-3%7B47%7D4-HP-CRAFTEX.html) has a flat base. I'm concerned about installing the new lathe directly to the workbench. The bench is massive and solid, but it's not perfectly flat. The 2"x6" planks vary slightly in thickness.

I'm thinking of getting a 1" or 2" thick slab of granite cut to the overall dimensions of the new lathe, with bolt holes drilled to match the mounting holes on the lathe. I can get a local stone supply to cut and polish the granite on one side and end up with a pretty solid and flat surface. I'm assuming I'd probably have to shim the lathe to get it true, but once shimmed the granite is unlikely to ever change dimensions.

Is this a good idea? Is there a down side to mounting the lathe onto a granite slab? Other than cost, is there any reason not to do this? Is this overkill for a small lathe like the B2227L?

Thanks

Sheldon Jaffe

Vancouver, B.C., Canada

Hi Sheldon Jaffe,

When I mounted my bench lathe I used a steel-frame stand and made a couple of steel plates to put under headstock and tailstock. These steel plates have adjusting screws at front and rear that rests on the steel frame, the lathe can be adjusted with these screws, see here. Your bench seems heavy enough so why add the granite? If the granite rests on wood planks wouldn't the granite move when the wood get dry in winter? If the screws used level the lathe rests on the steel frame you ought to get much less movement.

Thor

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Sheldon,

I envy you having a stone supplier whose prices allow you to consider this.

Granite has been used very successfully for both Surface Plates, and Optical Tables ... so it certainly seems like a good idea. ... My only reservation is your chosen thickness; both of these applications tend to use 4" to 6" thick slabs.

MichaelG.

I have a small lathe (Myford speed 10 ) and mounted it on a concrete slab 3" thick and this makes a very good rigid setup. The granite slab is a super idea but needs to be a decent thickness, 1" would be too thin, I would go for 3" at least if possible, but it would be very heavy . The good thing about a concrete slab is that it can be cast directly where it is required and does not need lifting.

I have always thought a granite tombstone would make an ideal base and then when the time comes to shuffle off this mortal coil you could be laid to rest alongside your beloved lathe.

Doug

That at least gives a new dimension to turning in your grave.

Alan

Gross overkill in my opinion, for a hobby lathe. Kinematically it would be better to use two steel washers spaced apart front to back under the headstock and one tooling ball or small washer at the tailstock end. This would allow the bed to stay as flat as supplied with minimal interference from the bench.

If you use bolts to fasten it down to the bench, use rubber washers both sides, and tighten only hand tight with locknuts, so the bench doesn't pull the lathe out of alignment by using ridiculously high bolt torque. Seen this mistake more than once.

Just my two cents. JD

Who said Granite doesn't bend?

Neil

Nice example Neil but I doubt if 170 kg can do that and suspect it might have been warm at the time?

Regarding the stone mod, the idea you will not improve things is rubbish - there is a chap on the Yahoo Boxford group who has bolted his machine to a head stone and reports significant improvements - the Boxford also only has the two feet at the end and a central boss unlike this machine. You will get improvements from a new machine as you will alter the harmonics in the system (resonant frequency etc.) and if you make other alterations as Neils has you will find it is possible to improve things significantly. Kinematics is the wrong word here, we are talking about vibration and physical movement - bolting it to a well aged lump of granite and getting it nice and straight (I think all granite could be classed as well aged for this application?) will alter the resonant frequency of the system and hence the machine performance - this is an instance of common sense being bang on the money. Kinematics from an engineering point is the understanding (study) of mechanical systems such as links and levers and rotating masses in an unconfined 3 dimensional space. Bolting a lathe to half a tonne of stone probably moves us out of the unconfined area by most standards of understanding!

Mark

Alan: Turning in your grave? Obviously that is PUNishment for asking the questions.

Thor - What is this drying in winter you speak of? I live in Vancouver, 160+ days of rain per year, and my house is about 300 yards from the Pacific Ocean. I'm actually about 3 feet above sea level at high tide. To compete with Alan, there's a common saying in Vancouver - people who live in Vancouver don't tan, we rust.

The ideas are great - I think I'm going to use most of them. Metal frame with levelling adjustments holding the granite slab, with 1/8" thick neoprene sheet between the lathe and the granite. I can get all this stuff easily and cheaply so why not go overboard and combine all the suggestions?

Sheldon, you can see what Neils did in this picture and you cod always join the group to get information from him - he is always keen to chat. If you use compliant washers don't be tempted to leave them slack - they need to maintain the settings when you shim the bed and the granite will help restrain the bed from moving as it ages.

**LINK**

When I installed my machines I wanted the option of coolant so I grouted the Boxford base to a reinforced floor (it was done specifically as a workshop) and then used silicone and shims to get the bed straight and sealed. I check it occasionally to see if it has moved and it has stayed set for the last 4 years. The silicone was chosen as an effort to isolate vibration transmission in the cabinet and to make bed adjustment easier (Boxfords do not have head to bed alignment screws) I allowed the silicone to part set and finished the torque settings on the bolts to fine tune the bed alignment.

Mark

Mark

Hi Sheldon

A one or two inch thick slab of granite will flex. If supported on a timber base that is subject to movement due to changes in humidity or temperature.

I have a granite surface plate that is one metre by 800mm by 150mm thick the kind of thickness required for stability under a minimal load being only used for measurement.

Have you thought about casting the bench top in reinforced concrete. There are many videos on the net showing how to do it, it is popular for upmarket kitchen design. **LINK**

As you want to mount a lathe on it you could make it say 6 inches thick and delete the wood planks.
As is well known concrete shrinks on curing and continues to do so for around 30 years, but you will end up re levelling your lathe at least once a year anyway due to ground movement under your buildings foundations.

After the initial cure which is nominally 28 days concrete has achieved full strength. At this point shrinkage slows down to a very small annual amount.

Concrete can be steel trowel floated to a good polish, Or you can buy a few litres of epoxy paint, that will also stop oil or water being absorbed.

DIY concrete is very inexpensive.

BTW most Granite is not completely oil or waterproof.

Regards
John

Edited By John McNamara on 12/06/2014 16:11:48