# Can someone surface grind something for me?  4140 PH



## Cadillac STS (Feb 9, 2019)

I am going to make a base for my QCTP and take out the compound until needed. Looking for more rigidity. 

I have a piece of 4140 PH that is about 2X2X6. I just need it surface ground on 2 opposing sides so it sits straight on the lathe cross. It can end up less that 2 inches as I will adjust the tool heights as needed. 

Can anyone do this for me and what price?  Please PM me through this site. Anyone in West Michigan so I can drop it off. Mail is good too.


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## f350ca (Feb 9, 2019)

You may not want it ground. I made one from a chunk of cast iron and ground the top. Looks pretty but the hardened tool post likes to turn on it. A little roughness may help.

Greg


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## Dabbler (Feb 9, 2019)

Do you have a mill?  You are just fine if you lap the top for measurement purposes.  I agree with f350 about the bottom.  Looks like a great project!  -- What lathe are you mounting this on?


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## Cadillac STS (Feb 9, 2019)

I thought the ground surface would be better for holding the tool post and keep it from moving

It is a Wabeco D6000e  German made precision lathe.


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## mmcmdl (Feb 9, 2019)

More friction milled than ground . I should say a better grip .


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## ddickey (Feb 10, 2019)

Might not be a bad idea to relieve the bottom..??


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## Dabbler (Feb 10, 2019)

I've never tried relieving the bottom.  For minimum chatter you'd think that having as much metal-to-metal contact as possible is the way to eliminate minute movements due to flex in available gaps.

My 4-way and both my QCTP have never slipped.  Both of them are 'smooth', by which I mean they are coarse ground so grinding marks are seen.  I'd be just as happy with a face milled bottom.


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## ddickey (Feb 10, 2019)

Looks like you have a pair of T-slots to mount your block to.


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## Cadillac STS (Feb 10, 2019)

ddickey said:


> Looks like you have a pair of T-slots to mount your block to.



Yes two T slots. I am going to just try two holes to T nuts. Might mill two mating tracks on the bottom of the base but I don’t think that will be needed. The compound does not have mating tracks.


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## Dabbler (Feb 10, 2019)

Consider milling 2 long T nuts and using 4 cap head screws to hold it down.  Ground or not, it won't move at all.  No need for mating keyways, and a lot of work (and precision) that will probably be unnecessary. 

(Unless you'd like the challenge - then I bow to you!)


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## jbolt (Feb 11, 2019)

When I made the solid tool post riser on my PM-1440gt I turned the top and bottom using the 4-jaw chuck. With careful measuring and adjusting I was able to get the top/bottom within .0002" this way. 

I agree with Dabbler on using a single long T-nut on both sides with 2 screws each. If you feel the need to key it, I would slot the bottom of the riser block and then make the T-nuts taller to also act as a key. 

How wide is the QCTP? 2" seems kind of narrow for a riser block.


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## Cadillac STS (Feb 11, 2019)

jbolt said:


> When I made the solid tool post riser on my PM-1440gt I turned the top and bottom using the 4-jaw chuck. With careful measuring and adjusting I was able to get the top/bottom within .0002" this way.
> 
> I agree with Dabbler on using a single long T-nut on both sides with 2 screws each. If you feel the need to key it, I would slot the bottom of the riser block and then make the T-nuts taller to also act as a key.
> 
> How wide is the QCTP? 2" seems kind of narrow for a riser block.



It is an AXA post.  It does hang over a bit in the one direction but I think it will be ok.

It is a DTM tool post.  DTM was made up of Aloris guys that went and made their own post from what I read.  It is excellent, precise and solid.

I decided to try it as it is, it has one side that is very flat better than I could get it with my mill.  Then if it doesn't work that way I'll have it ground.  Someone over private message agreed to grind it if needed.


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## Dabbler (Feb 11, 2019)

Where does oe buy a DTM tool post?  A web search didn't turn up anything relevant...


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## ddickey (Feb 11, 2019)

They're not made anymore. For years now.


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## Dabbler (Feb 11, 2019)




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## Toolmaker51 (May 9, 2019)

Dabbler said:


> I've never tried relieving the bottom.  For minimum chatter you'd think that having as much metal-to-metal contact as possible is the way to eliminate minute movements due to flex in available gaps.
> 
> My 4-way and both my QCTP have never slipped.  Both of them are 'smooth', by which I mean they are coarse ground so grinding marks are seen.  I'd be just as happy with a face milled bottom.


Contact is one thing, flat is another. Such as trying to face off a 6" diameter, only to find as you approach the centerline, it's higher than the periphery. Simple mechanics, no matter what feed rate [feed per revolution] is selected, it remains constant across the face, creating lower feet per minute. Examine a cylinder square, they are relieved to insure perfection after grinding.


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## mikey (May 9, 2019)

We're necroposting but I have to agree with Toolmaker re relieving the bottom of something that sustains torque. Back when I bought a TS Engineering tool post for my Sherline lathe, I had a problem with the post turning with a big cut, a big cut on a Sherline being about 0.050" - 0.060" radial cut in mild steel. The post would turn no matter how tight you cranked on the center stud. The answer was to cut a circular relief into the inner surface of the base, leaving a 1/4" wide rim of material at the edges. After that, just normal snugging of the center stud locked the post solidly.

As for grinding, I use a fair amount of precision ground steel stock to make tools with. The reason for this choice is because it takes very little clamping force to lock two ground surfaces solidly. Quite often, I will use a single screw to lock two ground pieces together, while also allowing them to be quickly adjustable by loosening the screw. 

For a plinth, grinding it is not a bad idea if you also grind the base of the tool post; better yet, relieve the base and then grind the rim left behind. Bet that post will lock with very little effort.


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