# ER to D1-4 Backplate Fitting



## Ray C (Jul 27, 2014)

Hi Folks...

Someone in our group requested that I mount an ER40 chuck to a D1-4 lathe backplate.   No problem, we can do that...  Here's how.

First, the backplate was brand new and in almost all cases, the tapered hole is cut undersized.  I've seen this on every new backplate I've ever encountered.  To check, mount the backplate on the spindle, fasten it firmly and use a flashlight from behind to look for light at the spindle interface.  It shows quite clearly in the following photo.  The interface must fit flat and simultaneously, the nose taper must engage the hole taper for proper alignment.

There's about 1.5 thousandths inch of light leaking through that gap between the interfaces (look at the top between the spindle and plate).





Things need to be fixed.  It won't take much reduction on that taper to allow the interface to seat properly so, the plate was mounted on a chuck and coarse sandpaper was used to open-up the tapered hole.  There is trial and error here and you don't want to take too much off (although that can be fixed if you screw-up by taking off a small amount from the flat part of the interface).  

Note that I'm using a simple 3J chuck to hold the plate from the straight part of the hole.  No fancy alignment is needed here.  Take a very, very light skim pass over the flat interface.  This just makes sure it's flat.





WORD OF CAUTION: To do this, you and the rest of your body are very near a spinning chuck.  NO long sleeves.  ONE hand holding the sandpaper.  OTHER hand near the kill switch.  Get it?   The hole was marked with ink and sandpaper was used with the plate running at/about 300 RPM.  As soon as all of the ink is gone, I know from experience that removes about 0.0005" of material (because the ink soaks in a little bit).  It took about 4 tries of doing this before a very slight zero-tolerance fit was obtained.  This is tested by removing the working chuck, installing the lugs in the plate and snugging them tightly to attach the backplate. 

Remember, upon using firm pressure when tightening the camlocks, the flat interfaces must simultaneously meet as the tapered surfaces engage.  It's a very snug interference fit and when you release the camlocks, the backplate should pop off.





Once this is done, now we know the interface is flat and the taper is fitting perfectly.  This must be verified...  Put an indicator against the surface as shown, spin the plate by hand and mark the locations of any high spot (one will certainly exist).  Next, unlock the backplate and re-mount it by rotating the lug position one set of holes so it's offset 120 degrees.  Put the indicator back on the surface and verify that the high spot is in the same place as the previous markings.  Repeat this for one more 120 degree re-mounting.  The high spot should always show in the same place.  This verifies that the interface and taper are locking-up consistently.





We're ready to rock & roll...  Now go ahead and make everything "square" by truing-up the faces and cleaning-up the center hole as shown.  Also, in this case, a shoulder is needed to fit the boss in the back of the ER chuck.  In this particular case, the ER chuck must fit tightly on the shoulder.  This requires sneaking-up on the final size.  -Don't blow it!  Get close and use emery cloth wrapped around a tool blank until the chuck fits with a very slight friction fit.   For normal chucks, I don't do it this way but because of how the bolts attach in this case, it must be done this way.  -And you'll see later, it caused a problem (as it always does)...  

Here's the straight hole getting cleaned-up as well as an overall view of the nicely squared-up backplate.  Remember to break all the edges or you'll be bleeding every time you use your lathe...






The fun part is over now and we're down to drilling holes and counter sinking  (yawn!). 

Use ink to mark the locations of the intended holes.





Grab a trusty piece of scrap, turn it to the diameter of the threaded holes and put a point on it.  Carefully line-up the ER chuck to the desired location and mark where the holes will go.






Drill the holes (not shown) and countersink from the correct side (don't mess that up or you'll be crying).





And this is what it should look like now...
As you see, the countersunk bolt heads are on the backside of the plate -and this is why we need that tight fitting shoulder to align the chuck... because you can't tighten the bolts while the plate is attached to the spindle.  We have no way to align the ER chuck manually and must rely on the shoulder.





... And of course, as predicted...  when mounted perfectly on the should, the taper has 1.5 thou runout!





Uh-Oh, what now boss?  What do we do?

Well, as expected, every place I check on the backplate, it's perfect.  DI needle does not move except for background vibration.




Hmmm, boss man says something's wrong with the chuck...

YEP...  When checking the thickness as shown in 3 different places, it varies by 0.002".  That could certainly account for some error at the spindle because, it's not sitting flat.  Other things could be wrong too -such as overall concentricity between the chucks shoulder boss and the tapered hole...





OK, now what?   First, this ER chuck belongs to someone else.  -And there's no way in the world anyone is going to let me machine it.  Furthermore, I have a candle's chance in a windstorm of ever fixturing it up well enough to machine it properly...  Not only that, I can tell by looking at the piece that it's about Rockwell 40 C.  And light cuts don't come out well on moderately hard metal...

Answer?  Emery cloth... Get to know it and get to like it.  Instead of messing-up the customer's chuck, I manually tweaked the mating surface near the shoulder of the backplate.  Took a little elbow grease and 2 hours, 20 minutes (start to finish) but guess what?

Runout is +/-  0.0004".




BTW, the various OD's on the of the chuck itself show some runout... but who cares?  All that matters is the ER taper.  FWIW, when measuring a taper like this, you need to check at the inner and outer hole of the taper.  Mark the high spot and make sure they coincide.  If they don't the machined ER taper is bad.  In this case the RO was consistent.


... Anyhow, on that ER chuck, there are two places where I can verify out-of-concentric dimensions greater of about 0.002 to 0.003" inch.  No worries, it all came out in the wash anyhow...  This just shows you can't throw your arms up in the air and say it's junk...  We all aspire to be machinists -and figuring things out and fixing stuff like this is what machinists do for a living.

Ray


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## LEEQ (Jul 27, 2014)

Nice! Thanks. I have the same plate ( Thanks Jeff) to mount to a 7x12. I was considering making a set true back plate. I'm also considering machining the plate itself to fit the spindle without a separate backplate. Considering the hardened state of the plate and my unfamiliarity with turning hardened materials, I may steer away from trying to alter the er40 plate. Any thoughts are sure to be pondered deeply.) If you were to turn down the od once well fitted, what would you cut it with?


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## JPatMcConnel (Jul 27, 2014)

Very nice job Ray, I'm impressed, especially by all the factors that went into assuring all the parts played together and are accurate. The pictures really add a lot to the description for those of us who sometimes have trouble walking the words to action. I also appreciate the emphasis on safety.

Well done!

Pat McConnel


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## darkzero (Jul 27, 2014)

Very nice write up Ray as always. I chose to front mount mine to make adjustments much easier if ever needed. 

One suggestion for the owner..... I made a handle for holding mine when loosening/tightening the nut. That way I don't have to switch to a lower gear when doing so. Great time saver & I needed one for my super spacer anyway, my handle works for both so killed 2 in 1 shot.


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## Ray C (Jul 27, 2014)

LEEQ said:


> Nice! Thanks. I have the same plate ( Thanks Jeff) to mount to a 7x12. I was considering making a set true back plate. I'm also considering machining the plate itself to fit the spindle without a separate backplate. Considering the hardened state of the plate and my unfamiliarity with turning hardened materials, I may steer away from trying to alter the er40 plate. Any thoughts are sure to be pondered deeply.) If you were to turn down the od once well fitted, what would you cut it with?



LEEQ,

Do you mean the OD of the extra stick-out of the backplate?  If so, I'd grab whatever carbide insert happened to be closest and tear it down about 50 thou at a time... In this case, I can't do that.  There are pre-drilled holes in the backplate that bisect the OD of the chuck.  It would lead to a dangerous condition.  Someone snags the palm of their hand on that and the next thing I'll be doing is sending them the contact information for my liability insurance...


Ray


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## LEEQ (Jul 27, 2014)

I'm thinking I can get down smaller than that pattern, which leaves me needing to drill a new one. I'm not sure what I would use to drill with. I don't have carbide end mills of any sort. I have boring bars, a face mill, and some brazed lathe bits as far as carbide goes. It's probably going to be a lot easier to not make it as small as I would like, but what would you use to poke bolt holes in it?


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## darkzero (Jul 27, 2014)

LEEQ said:


> I'm thinking I can get down smaller than that pattern, which leaves me needing to drill a new one. I'm not sure what I would use to drill with. I don't have carbide end mills of any sort. I have boring bars, a face mill, and some brazed lathe bits as far as carbide goes. It's probably going to be a lot easier to not make it as small as I would like, but what would you use to poke bolt holes in it?



If your intention of doing this is to avoid existing holes on the backplate, you could always start out with an unmachined backplate. That's what I did, no unnecessary existing holes to worry about & you won't have modify the er plate.


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## Ray C (Jul 27, 2014)

LEEQ said:


> I'm thinking I can get down smaller than that pattern, which leaves me needing to drill a new one. I'm not sure what I would use to drill with. I don't have carbide end mills of any sort. I have boring bars, a face mill, and some brazed lathe bits as far as carbide goes. It's probably going to be a lot easier to not make it as small as I would like, but what would you use to poke bolt holes in it?



Drilling CI... Easy.  Any standard drill bit.  CI is not hard to cut at all.  For lathe purposes, it dulls HSS bits a little bit faster but not terribly so.  

If you need to drill the hardened chuck itself, you can do that too with HSS but, may need to sharpen as you go.  Rockwell 40 is still workable.  Things get challenging at 45 or higher.  Just make sure the bit is sharpened properly and use the correct feeds/speeds -do all that and the piece won't work-harden on you.

So sorry... I didn't mean to throw you off track with my comment about grabbing carbide to do the job.  I use carbide for most of my work.  I personally find it more consistent, edges last longer, faster for me to use etc...  The only normal metal that comes close to beating it up is stainless steel or similar metals.

Anyhow, the problem you may face is getting the 120 degree hole pattern just right.  Believe it or not, getting six holes to line up isn't easy to do some times.  Mark things out very carefully, punch a clean divot with a sharp punch and always use a starting-bit to start the hole.  Also, drill the holes really straight -straight as you can.  If you get a few degrees of angle in the hole, the bolts will interfere sideways as the get screwed in.

Show some pictures of the pieces you're working with and maybe I can help you through it...


Ray

- - - Updated - - -



darkzero said:


> If your intention of doing this is to avoid existing holes on the backplate, you could always start out with an unmachined backplate. That's what I did, no unnecessary existing holes to worry about.



Will,

Where did you get an unmachined plate?  Haven't see one of those around (but I haven't exactly been looking either).  Always comes in waves where someone wants me to tune-up a chuck and I really think a naked plate would be less hassle than re-doing a manufactured one.


Ray


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## darkzero (Jul 27, 2014)

Ray C said:


> Will,
> 
> Where did you get an unmachined plate?  Haven't see one of those around (but I haven't exactly been looking either).  Always comes in waves where someone wants me to tune-up a chuck and I really think a naked plate would be less hassle than re-doing a manufactured one.
> 
> ...



I get them from Grizzly, well not actually directly from Grizzly....

This is the one I used for my ER plate. SB1393

 It's Grizzly's South Bend branded backplate. They claim they are fine grain cast iron as opposed to their regular ones that are a bit cheaper. This is their regular one. T10102

Their photos aren't accurate as they don't always show the correct picture for the product, both pics for those 2 listing are identical. The fine grain casting, not sure what that actually is but the SB branded backplate I received is much shinier than the common import backplates that are a dull grey color. And when I was machining it I could tell that it was finer. Like the backplates that I have purchased in the past that are dull grey, they have lots of pits. I don't know much about CI grades & casting types.

All the backplates I have been buying recently are the SB branded ones. Not sure if I was just lucky but the SB D1-4 fit my spindle taper very nicely. This one & my Bison backplates are the only ones that I got that did not need fitting. I just picked a SB branded 8" blank (no spindle mount) for my RT, it was cheaper than what I got quoted at my local metal supplier for a similar size. They also sell thick unmachined backplates for making Set-Tru/Adjust Tru backplates in both regular & "SB". 

I've been pretty happy with them so far so I'll continue to buy them when needed. Oh, and I buy them from Amazon. Cheaper & free 2 day shipping with Prime (just have to watch prices as Amazon prices fluctuate often).


Here you can see how "bright" the backplate is.


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## LEEQ (Jul 28, 2014)

Ray C said:


> Drilling CI... Easy.  Any standard drill bit.  CI is not hard to cut at all.  For lathe purposes, it dulls HSS bits a little bit faster but not terribly so.
> 
> If you need to drill the hardened chuck itself, you can do that too with HSS but, may need to sharpen as you go.  Rockwell 40 is still workable.  Things get challenging at 45 or higher.  Just make sure the bit is sharpened properly and use the correct feeds/speeds -do all that and the piece won't work-harden on you.
> 
> ...


I am working with that same er40 plate and a 7x12 lathe spindle. My thoughts are to buy a blank back plate or piece of round cast iron. One method in mind would mount the spindle in the back plate in a deep enough recess to allow set screws to bear on the outside of the spindle. Cutting the recess in the back plate that receives the spindle spigot oversize so you can set it true.  The er plate would mount to the back plate and you would adjust the back plate set screws as you tighten the back plate to the spindle. The spindle od is something like 3-3&1/2". Regardless as to how it mounts up, I would like to turn off as much of the excess od as possible to make it appear more to scale, a fit pleasing to the eye.  My mill with dro makes quick work of bolt circles, so I'm lucky there.


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## British Steel (Jul 28, 2014)

Those import ER32 chucks can vary wildly in quality and concentricity, it's worth a little.extra trouble to ensure they're up to.the job: Chuck a piece of ground rod in a 4-jaw and indicate it in as accurately as you can, then attach the ER Chuck back-to-front using the right size collet (try a few different orientations of the collet in the chuck, to ensure the collet isn't eccentric}:??, now you can put a DTI on the mating surfaces and if necessary take a.skim cut to true them up before machining the backplate to fit. If the collet Chuck is too hard / you have a less than rigid lathe and chatter sets in, it's time for.the toolpost grinder!


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## chips&more (Jul 28, 2014)

British Steel said:


> Those import ER32 chucks can vary wildly in quality and concentricity, it's worth a little.extra trouble to ensure they're up to.the job: Chuck a piece of ground rod in a 4-jaw and indicate it in as accurately as you can, then attach the ER Chuck back-to-front using the right size collet (try a few different orientations of the collet in the chuck, to ensure the collet isn't eccentric}:??, now you can put a DTI on the mating surfaces and if necessary take a.skim cut to true them up before machining the backplate to fit. If the collet Chuck is too hard / you have a less than rigid lathe and chatter sets in, it's time for.the toolpost grinder!



Now that sounds like a plan!


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## darkzero (Jul 28, 2014)

British Steel said:


> Those import ER32 chucks can vary wildly in quality and concentricity, it's worth a little.extra trouble to ensure they're up to.the job: Chuck a piece of ground rod in a 4-jaw and indicate it in as accurately as you can, then attach the ER Chuck back-to-front using the right size collet (try a few different orientations of the collet in the chuck, to ensure the collet isn't eccentric}:??, now you can put a DTI on the mating surfaces and if necessary take a.skim cut to true them up before machining the backplate to fit. If the collet Chuck is too hard / you have a less than rigid lathe and chatter sets in, it's time for.the toolpost grinder!



Yep, that's exactly what I did with my ER40 plate using a 1" Thomson linear shaft (that's what I use to dial in my chucks) except I just used my Set-Tru chuck.


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