To regrind or replace, thats the question?

[modeldozer]

Hi all modders,

Turns out my 7x12 lathes bed is bent in the horizontal plane.  Fixing it is outside my experties so, does anyone know if thes can be reground economicaly or is it a matter of repacing the bed.  My only concern is until the new bed is installed I have no way of testing to see if it is any better.

Have searched the web and could not find any regrinders in Spain so shipping it of is going to be anoter expence.

Any advice , ideas would be greatly apriciated.

Slightly depressed 

Abraham.

[joshagrady]

How are you trying to find a regrinder?  Shouldn't be too hard in just about any industrial park.  The word you're looking for is "rectificado" if that helps.  (And apologies for the presumption if you already knew that.)

Saludos,

Josh

[P.J]

This could be an option perhaps?
http://www.amadeal.co.uk/acatalog/7x14_Real_Bull_Mini_Lathe_Bed_Conversion_Modification.html
It's £125.00 including shipping to Spain.

I have no idea how much it would cost to regrind the existing bed, it might be cheaper.
The amadeal lathe is also longer than the standard 10 or 12 inches between centres.

Good luck with the project 

/PJ

[dickda1]

A relatively inexpensive grind can be done on a machine called a Blanchard.  It uses a rotating vertical head with a series of grinding stones attached.  That would work if the bed has a flat profile.  This is quick and dirty and will give you a surface that probably should be scraped.  Used to repair Bridgeports a long time ago and this is what I used.

If the bed is not flat, you could have it ground on a surface grinder.  They will charge a certain amount (probably around £10-15) every time they shape the wheel to grind a vee surface. They may also charge a setup fee.  I can't image you could get out the door for less than £200.

Once the bed is ground, the lead screw will be too close to the new bed surface and must be moved.  

Entirely doable, sort of a fun project.  The bed will be beautiful, but expensive.

You will spend less if you buy a new bed instead of grinding I believe.

Take a look at "Fixing Darren's Lathe" on this forum before you decide.

-Dick

[modeldozer]

Hi Josh,PJ,Dick,

Thanks for the responses.

Josh,  was looking for lathe regrinding in particular, there are a few general "rectficados" neer me but will have to speak to them and see if they will be able to do the lathe.

PJ, seen that one and the price is what makes me wonder if repaclement would be cheaper.

Dick, not a flat bed, has a V way on the front and this is what is not straight.

From what I saw on some of the american regrinding sites it takes some special equipment to grind the Vs.
Will need to some more research.

Abraham

[dickda1]

You might just look around for a place that has a surface grinder - advertising for machine repair, engine rebuild, etc. 

If you put the bed in your car, you can just show up and ask if they could grind it for you - has worked for me.

If you do have it done, it is important that you talk to the foreman or the person running the grinder.  They don't see these sort of small machines and need to be informed about what needs to be done.

1.  Measure the thickness of the bed with a micrometer before it is ground so that you will know how much to lower the attached lead screw.
2.  The operator needs to know that the bed should be supported on blocks just under the ways, not under the feet cast into the bottom of the bed.
3.  He should be informed to  take a skimming cut just until the bed is mostly clean.  If the bed has pits / dents, he may continue to grind until they are gone, substantially reducing the bed thickness.

-Dick

[modeldozer]

Hi Dick,

Thanks for the tips.  Will go arround to a few and see what can be done.

Silly question; how would one grind the V on a surface grinder, angled wheel or setup at angle?

Abraham

[BillTodd]

This could be an option perhaps?
http://www.amadeal.co.uk/acatalog/7x14_Real_Bull_Mini_Lathe_Bed_Conversion_Modification.html
It's £125.00 including shipping to Spain.

I have no idea how much it would cost to regrind the existing bed, it might be cheaper.
The amadeal lathe is also longer than the standard 10 or 12 inches between centres.

Good luck with the project 

/PJ

Looks like the way to go from here. I can't believe you'll get a good grinding job done anywhere for less than £125   

[dickda1]

"How would one grind the V on a surface grinder, angled wheel or setup at angle?"

Each face of a vee is ground separately by truing the wheel to the appropriate angle - wheel is not tilted.  Older lathes beds were generated on a planner - don't think they are around anywhere anymore.

-Dick

[snoopdog]

 I bet the lathe is just fine for a 7X14. DONT BOLT IT DOWN TIGHT. its a small machine and dont need it.

I bet the machine is fine and the problem is the owner, no dog on you but just telling the facts.

[modeldozer]

Dick, Thanks for the reply, was just curious.

Snoopdog, Using a well proven method for checking the headstock alignment it is fine for the first 80mm from the chuck, but then in the next 70mm moves in horizontaly by 0.1mm. In the vertical plane it is perfect at 0.005mm droop over 150mm witch I attribute to the bar droop. I have spent a lot of time to increase acuracy and fix a few flaws with the lathe and would like to get this as best as possible as well.  So yes it is the owner trying to make it better.

If all goes to plan will be visiting a few machine shops tomorrow.

Abraham

[MaceT]

Wouldn't it be a better idea to bolt the lathe to a large thick plate and pull it straight?
Seems like this method would give you the ability to bend it perfectly straight, plus the added rigidity.

[modeldozer]

Small update,

The lathe is at a major machine shop, they will see what can be done and quote on the job. Here´s hoping.

The lathe is actualy bolted to a lengthof 50 x 100mm rectangular tube that is part of the riser I made to get it at my height.  For a planned mod it will also get a 12mm plate added between the riser and the lathe.

I have tried to shim under different corners of the feet to get it straightened, but it affects both vertical and horizontal, so gave up on that idea.

Abraham

[modeldozer]

Hi all,

After a lot of searching finaly got a quote from a machine tool vendor repair shop 250€, now comes the decition part , will have to sleep on this one.

Abraham

[lordedmond]

well a point is that the lathe bed must be in a operating position ,

Myford take a lic over the feet then blot it down to a know good level plate there is a pic of them doing it down the article
http://www.myford.com/meu/MEU_Issue_02/article_02-013.html


yes i know its not a 7x12  but most of the fitting testing principles are the same

[modeldozer]

Thanks for the replies.  Have attached a file with my test data.

Have tested with the bed bolted down and free with no difference.  Also tried shimming under the feet, but this affects the vertical alignment as well.

The very helpfull people at Amadeal will look into testing a new bed before shipping it to me.

Waiting hopefully for the moment.

Abraham