# Building a Lathe face/drive plate



## Brent H (Nov 3, 2020)

@YYCHobbyMachinist has a thread about looking for a lathe face plate and drive plate so I thought I would build one that will do both.  @PeterT just made a fixture plate for his rotary table and that type of plate could also be used for the lathe face plate application.
The face plate on a lathe can be used to turn or face odd shaped items and has a bit more versatility than a 4 jaw chuck for some odd shapes - you just need to watch how you balance the weight so as to avoid as much vibration as possible.  Typically the face plate has a centre hole that allows you to insert a dead centre into the spindle of the lathe.  Mine is a #4 Morse taper.  This will allow you to turn between centres.  
Most lathes are sized by the diameter they can turn and the length.  Typically that length is greatly reduced when you add a chuck as the length is given between centres.  Turning between centres allows the project to come off the lathe for checking fits or even transferred to other lathes with out impacting the accuracy of the turning.  You can do it using your chuck, a centre inserted into the chuck, cleaned up on the lathe and then use the jaws of the chuck to drive the dog holding your work piece.  You can also do it by installing a drive plate and using a centre in your lathe spindle.  This can add several inches of extra length if your project requires it.
For my project I will be making a face plate (you can bolt work on) and also add a fixture for use as a drive plate for “L” shaped lathe dogs.  The straight dogs require a bolt to engage the drive pin on the dog.  This would also be easy on this type plate.  
The plate I am making is 9” OD (I have a 10” lathe) and 7/8” thick.  It is mounted to a D-3spindle adaptor plate.  




some Bluing to get a rough layout.  I stamped a deep centre punch approximately in the centre

I set things up on my mill on top of a large (12”) rotary table and drilled and tapped for the D-3 adaptor. Holes are threaded for 3/8-16




Once that was done I milled slots in at every 60° using a 3/8” carbide 4 flute end mill (additional 0.020” on either side of the slot for clearance) and then milled out the “T” using a special purpose T slot end mill for 3/8” bolts. 








More coming....


----------



## Brent H (Nov 3, 2020)

The build continues.....

For those who keep track of feeds and speeds : I was running the 3/8” end mill at about 850 RPM and my x-axis doesn’t give a feed rate but  I was probably 4 to 5 inches per minute.  The end mill was just chewing the stock with no issues and I could touch the (not running LOL) mill after taking the needed passes.  I took 0.050” each pass to a depth of 0.610”.  The T slot cutter was running 100 RPM with a feed of about 1/2 to 3/4 inch per minute. Clean cuts, no heat build up. 

Once slotted I needed a relief in the back for the D-3 adaptor plate.  I bolted the adaptor plate onto the front and then cut a 0.125” deep relief just shy of the D-3 required diameter.  I unbolted the face plate and then de-burred followed by taking light cuts off the D-3 flange until I had a good fit to the face plate.   Bolted everything together. 




for the D-3 adaptor the posts are all fit to the numbered holes in the lathe spindle.  I then stamp the flange so it always goes back in the correct orientation.
On the lathe I needed to bore the centre hole to 1-3/8 and also true up the outer surface and add some reference rings to the face. Trueing up the outside was a challenge as my lathe cannot back up enough to reach.  I spun the tool post and used a left hand boring bar - worked very well.




I then machined in some rings with a 45° Tool bit, broke the edges on everything and here is the face plate 




So now I need to make some T nuts and a fixture for the dog legs.  While I was  messing about I found I have a #4 Morse taper dead centre so that will work and I also have a #4 Morse taper to Jacobs 33 where the 33 taper is a bit chewed.  My thoughts are to machine it straight and then make up a “sacrificial” tip that can be turned true once you insert the dead centre.  I will post more on the other parts as they are made.

the plate is about 0.003 thou out of perfect “flat”.  I have not run a racing pass on it and may just leave it like that.


----------



## David_R8 (Nov 3, 2020)

Looks great Brent!


----------



## Brent H (Nov 3, 2020)

Thank you @David_R8 - it took about 7 hours to make - had to find the tools and set up the mill etc.  The D-3 adaptor plate is a $75 Amazon item.  I wished I could find just the hardened pins for a decent price but I am having no luck. At $25 each .... well .... might as well get the whole thing - LOL.


----------



## Hruul (Nov 3, 2020)

Looks Great!!


----------



## PeterT (Nov 3, 2020)

Nice job. well executed.

Have you come across a homebrew balancing fixture that allows you to counterweight the face plate assembly like when you machine non-symmetrical components or end up with more clamps on one side for example?


----------



## Brent H (Nov 3, 2020)

@PeterT : nothing yet regarding the balancing other than with the slots I should be able to slide a counter weight/weights down the slot to achieve better balance and bolt in place.   The drive dog will be of aluminum to lessen the mass of it. My stock pile looks to include a tasty piece.  

I am currently sizing steel for some T nuts.  
Here is mock up of lathe dog mounted:





And here is my “sacrificial” centre idea on the board - not to scale LOL 





Simple way for lathe dog is just a block I can move to catch the tail. - or I machine a pocket ?


----------



## YotaBota (Nov 3, 2020)

Nice, almost like you knew what you were doing  lol
Where is the D-3 adapter from?


----------



## Brent H (Nov 4, 2020)

@YotaBota - LOL thank you 

the adaptor is from Amazon:


----------



## Brent H (Nov 4, 2020)

Carrying on with the build I made some T - nuts that are threaded for 3/8-16 bolts - should help hold future jigs and items.  I also made a drive for the L shaped lathe dogs - it is a 1x1 x 2” piece of aluminum that fits the face plate slots to keep it from rotating and is held in place with a 3/8 socket head cap screw.

easiest way to make T nuts is in a batch out of a longer piece of stock.  These are made from a 6-7/8” long x 3/4 wide x 1/2” thick piece of steel.  The T part is about 0.400 wide to fit the slots in the face plate.  I chopped them off in the bandsaw and then faced them a bit for looks.  De-burred and blacked. 















the above pic is me counter boring the aluminium block for the socket head screw.  These counter bores are nice as they indicate the head size and clean out a nice bore.  




And the drive block installed with a piece of old shaft demonstrating its function:


----------



## PeterT (Nov 4, 2020)

Brent, I haven't done any T-slot milling yet. What is your procedure? Like plough down the center line & then separate finish pass on either side? I assume the physical slot width is a bit bigger than the cutter diameter itself? And what about vertically, clean up pass along the floor of the T?


----------



## YotaBota (Nov 4, 2020)

Don't forget to add your blackening secret to the above procedure.


----------



## Brent H (Nov 4, 2020)

Hi @PeterT 

So I measured the shank of the cutter and it was 0.400 so that is needed a bit more clearance (say 0.015”).  Since I was  cutting on the rotary table things were somewhat easy.  Once the table was square and centred I determined where I wanted to stop (some folks might want to plow right through - saves time).  
I cut in to what I wanted the depth to be, in my case was 0.610 for a 7/8” thick plate. Once the final pass was done with the 3/8 straight cutter, I simply made a pass 0.020 either side of centre leaving a 0.415 wide slot.

the floor of the T is set with the T slot cutter.  I brought it in to just be touching bottom (say a couple thou) and it did the rest.  Power fed it in and out and while feeding blew the chips out (comp air) to keep the cutter from jamming up on material.  Also a bit of oil for side lube of the cutter.  So no clean up pass just the feed out and keeping chips out of the way.
For blackening I used the gun blue stuff from Cabelas but - rinsed the parts in a bit of paint thinner to degrease and remove bluing, cleaned off and then soaked in an acid solution to remove any rust and mill scale - you can go harder with a diluted muriatic acid but outside and with huge ventilation.  - I just soaked in vinegar for a few hours.  Blew all clean and swished them in the bluing.  Sit for 10 minutes in the bluing - then dry all off and coat in light oil - like spindle oil.


----------



## YotaBota (Nov 4, 2020)

I'll have to stop at Cabelas next time I'm in that area for some bluing. Thanks for the guide.


----------



## PeterT (Nov 4, 2020)

Check the prices on blackening solution. Its all over the map $/volume basis & from what I've experienced, its always the same stuff, for steel at least. I bought some from KBC once upon a time & also a local jewelry supply place called Kens Gems who has other solutions more for the metal artist crowd.

From my experience I wouldn't bother with kits. For prep solution, use Brent's recipe or I've had the same results with water based grease/oil removal solutions, acetone, methanol & other degreasing prep solutions. You just have to watch some thinners if they have an oily residue component. Just because its meant to reduce or thin oil based paint for example, doesn't mean its degreasing the surface. The cleaner you make it the better chance of no blotches. The more you prep the surface so its uniform matte, the better it will look. I like those maroon scuff pads. Yes, use a new one.

We have discussed this elsewhere but like Brent I've found the best coating once blackened is oil. Just be sure you have dipped or applied the black solution enough times so you are happy because once its oiled, its not a great surface for re-blackening without essentially starting over.


----------



## Brent H (Nov 4, 2020)

Roger that @PeterT  - my paint thinner of choice is typically something like acetone or lacquer thinner - nothing that leaves residue.  The gun blue at Cabella’s is a common one - forget the name but it is pictured in my thread on refibbing that cinicinatti tool cutter/grinder


----------



## YotaBota (Nov 4, 2020)

PeterT said:


> I like those maroon scuff pads. Yes, use a new one.


And here I was hoping to use up the bag of old oily ones I have. Thanks for the reminder, I would expect that prepping the same as for paint should be sufficient. I forgot that bluing came out that dark.
Brent - I'll check your other post for the name of the bluing and lacquer thinner is in my paint cabinet.


----------



## Hruul (Nov 4, 2020)

I am going to guess it was Brownells - oxpho-blue. That is what I found at our Cabela's in town.


----------



## PeterT (Nov 4, 2020)

Here is KBC 1 qt (smallest size) for price reference


----------



## YYCHM (Nov 4, 2020)

Hruul said:


> I am going to guess it was Brownells - oxpho-blue. That is what I found at our Cabela's in town.



I'd be really surprised if you found a Brownells product at Cabelas's.  It was probably this....

https://www.cabelas.ca/product/370/birchwood-casey-super-blue


----------



## Brent H (Nov 5, 2020)

@YYCHobbyMachinist wins!  Yep, that is the stuff.  I have used the stuff from KBC tools in the big bottle at work.  Works well if your prep is good.


----------



## historicalarms (Nov 5, 2020)

In one of your post's you state "the plate is out from perfect flat by about .003".

    In one of his books, Tubal Caine states that "every faceplate should have a very faint/small taper from outside to the center". 
   I have never figured that out...cant come up with a reason that a taper is preferable to a "super flat" mounting surface. The face plate that came with my lathe wasn't "true" to the lathes axis so I did take his advise & make a slight taper cut to the face to true it up....but still cant figure out why...

  In an oddball shaped workpieces & clamping fixtures that do cause an off-balance situation that causes vibration...that vibration can be minimized by speed reduction rather than messing with a bunch of counter balancers to be clamped on.


----------



## Hruul (Nov 5, 2020)

@YYCHobbyMachinist You are correct.  I have both, the Brownell's was the one that came to mind first.


----------



## RobinHood (Nov 5, 2020)

All three lathes I have state a maximum speed when running a face plate. E.g. for the SM 1340 it is 500 rpm max with a 12” plate. Colchester says you can go to 1400 rpm max.

The taper towards the center is the same idea as the cross slide: it should either cut perfectly at 90* to the axis, but since that is very difficult to maintain over the life of the lathe (because of wear), they are usually set to do facing cuts of a few tenths concave. Keith Rucker mentions that Monarch recommends about 0.0005” for his 16” machine.
This way, faced part will butt snuggly against each other when stacked. If the ends were convex, they would rock.


----------



## Brent H (Nov 5, 2020)

Well HOT DAMN!! A perfect Mr Pete Plate!   LOL!!
That was great luck - LOL - my plate at 9” would never be going faster than 500 RPM - the surface feet per minute at the outer edge would be 1177.5.  That would be pretty quick.  300 worked well for its test. 

I tried it out with the lathe dog on the plate and there is no perceptible vibration so that is good.  
I am currently making a centre for the rotary table so I can get more gears cut.  I will be posting that on another topic thingy.  I am using a piece of the ship’s hull for one of the parts.


----------



## YYCHM (Jan 7, 2021)

Brent H said:


> Hi @PeterT
> 
> So I measured the shank of the cutter and it was 0.400 so that is needed a bit more clearance (say 0.015”).  Since I was  cutting on the rotary table things were somewhat easy.  Once the table was square and centred I determined where I wanted to stop (some folks might want to plow right through - saves time).
> I cut in to what I wanted the depth to be, in my case was 0.610 for a 7/8” thick plate. Once the final pass was done with the 3/8 straight cutter, I simply made a pass 0.020 either side of centre leaving a 0.415 wide slot.
> ...



Once again you have lost me  What are the overall dims of your T-NUTs?  

I'm trying to decide what dims to slot my faceplate to.  I'm thinking 8 slots relieved on the backside to accept 3/8-16 T-NUTS with a 7/16 slot which means I need 7/16 and 11/16 end mills.  

Also, what is the preferred order of milling two overlaid slots?  Narrow followed by wide or wide followed by narrow?

Thoughts?

Craig


----------



## Brent H (Jan 7, 2021)

Hey Craig,  if you are milling a slot within a slot , so to speak, I would mill the larger slot (larger cutter, stronger) and then switch to the smaller one and mill out the centre.  

for mine I actually cut in T - slots (thicker plate) with a dedicated T slot cutter specific for 3/8” bolts (basically you can slide a 3/8” bolt into the slot)


----------



## YYCHM (Jan 7, 2021)

Brent H said:


> Hey Craig,  if you are milling a slot within a slot , so to speak, I would mill the larger slot (larger cutter, stronger) and then switch to the smaller one and mill out the centre.
> 
> for mine I actually cut in T - slots (thicker plate) with a dedicated T slot cutter specific for 3/8” bolts (basically you can slide a 3/8” bolt into the slot)



Your T-SLOTs accommodate 3/8" hex head bolts?  What were the T-NUTs for?


----------



## YotaBota (Jan 7, 2021)

Brent H said:


> I am using a piece of the ship’s hull for one of the parts.


I hope the piece was taken AWL!


----------



## Brent H (Jan 7, 2021)

@yota - it would be a terrible sinking feeling if the ship was in the water when we cut out the bow thruster- LOL 

@YYCHobbyMachinist :

















The T - nuts give me the option to bolt from the front and the bolt head allows for using bolts and nuts, washers etc.  The slot, however, mills wider than the bolt head so the head will spin - not a deal breaker - the 3/8 slot cutter takes some big cut as it does both sides of the slot at the same time.  

you can recess the slot to fit a bolt head nicely and then it will hold from turning. Then use a nut on the back or front what ever you require.


----------

