# A Benchmaster mill non restoration.



## kop (Jun 9, 2022)

Let's see , where were we ...





						WTB Benchmaster/Duro mill
					

We all know what they are and how difficult they are to come by. Deep cosmetic repair and even complete rebuild is not beyond my skill set. As long as "most" of the mill is there I'm willing to sweat details like replacing with ball screws, scraping ways, even weld repair. I have no issue with a...




					www.homemodelenginemachinist.com


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## kop (Jun 9, 2022)

and...


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## kop (Jun 9, 2022)

I'll detail this journey with the most common answers .

Price, that's a tough one. As with older cars, 40 years is 40 years. You don't know what you have until you know what you've got.

There really aren't a lot of ways to completely disqualify a purchase. I'll cite some of the ones I ran into in my two year search.

Beautiful re-paint, except for one thing. They had painted over the vertical ways. Not being able to inspect the condition of the dovetail I passed on a $3K paint job.

Peckered to hell table. On top of the pecker tracks and marks in the table someone had actually been able to pull 3/8" hold down hardware out of the T- Slot with a sizeable chunk of the table. "It's an easy fix for any competent machinist" says the seller. Any competent machinist would not have abused the machine in the first place.

Zed screw, nut, bevel gears. Since the weight of the table sits on this screw it's difficult to access if the resistance is weight or crud. The weak link becomes the gears followed by the nut and screw. We are fortunate that the community has or at least had documented these parts in the past and since this is a much loved niche machine repairs are difficult but not impossible. Once acquired this is one of the first maintenance items.

Hold down hardware. 5/8" is common, 1/2" less common, 3/8" hardware is camouflaged cheese. You'll be making, sourcing, or modifying your own T-nuts. Other than a very few online retailers, all the hardware is Chinesium. Some may offer that creating a purpose point of failure at the T-nut is a safety feature. I disagree. Stay within sensible limits of the machine and all is well. If you really think that 3" diameter .080" surfacing cuts in steel are necessary you need a bigger mill.

You probably won't get the chance at most face to face inspections to tram the spindle and see if the ways are worn in the middle of travel. You can however get a notion of this by running all three axis to their limits. If you do get to seriously inspect the machine the price will usually be a bit higher because the seller already knows it's a good one. Don't be surprised if in any axis there is .001" - .0015"  or more table tilt in any direction. This is normal running clearance. More on this below.

Expect to do a full spindle service as well as Zed screw service. In order to easily access the Zed screw you will be removing the table anyway. This gives you access to all the screws and nuts. One common modification that has been done to these mills is the addition of a gib lock. This is simply and additional gib screw to lock an axis. Generally the Zed doesn't need a lock. So if you find an extra threaded hole and screw impinging in the gibs this is actually common practice. Lock all but the working axis. This not only reduces the locked axis clearance to near nil but improves the accuracy of the working axis. Not all of the Benchmaster mills had a gib lock . So if you see this extra screw the machine may or may not have been loved (other than purposely not wearing out a gib screw/threads) but the parts that came off it were.

Some helpful links for spindle bearing service. 

https://tinyurl.com/2cxhavrehttps://tinyurl.com/55d26knf
A word on shipping. I've used Fastenal Blue-Lane for years. Even though the Benchmaster was made in kalafornia they seem to be found more often in the rust belt. I was able to get a palleted box from U-line for $173 and shipped from San Diego to Seattle for $181. I was extremely fortunate to have family in San Diego and an unusual but outstanding member of Practical Machinist as a seller. Not three minutes into a phone conversation the price no longer mattered and this was the mill I wanted. $1,600 with Vertical and horizontal attachments, two motors, limited but useful tooling, and a conversation that has continued well past the sale. I do hope you are as fortunate.

I as of yet have no set opinion on this modification. It has been reported enough times to mention here. Boring out the MT2 taper to MT3. The reason is that standard MT2 collets are an advantage over a MT2 ER collet holder simply because of working height. Remember this is a pure knee mill without quill. Not only is anything hanging below the lower bearing unsupported and prone to deflection but full inches of Zed are lost. I'm leaning toward not doing this. I don't see me spinning the additional diameters available to MT3 collets. Again, it's a small mill, and there just doesn't seem to be the meat in the spindle to open it up the MT3. YMMV.

Very quickly you will find that although there is plenty of tooling available for the 7/8" and 1" horizontal arbors the one issue is involute gear cutter sets. You will spend a healthy premium for these in 1" and 7/8".
You will then find that these gear cutting sets are very common in 22mm. The 22mm arbors you will find online do not have the off end detail that fits into the overarm support bushing. Other than this they seem to be universally well made. If you or anyone else has an issue with MT2 driven arbors in any diameter Let me know. There is this guy in Michigan...

Sorry for the wall of text and seemingly useless information but it's what I've got.


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## kop (Jun 12, 2022)

So, a funny thing happened on the way to a "non rebuild" . 
Has anyone researched DRO for something like the Benchmaster? 
Precision Matthews, Grizzly, Jet, and the largely unpronounceables have approximately the same work areas available. Something has to be out there for my mill. 
Full disclosure. I have used DRO for years in various job descriptions. Before that I worked from dials. I'm an appliance user. 
A little help here, please .


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## Peter Twissell (Jun 13, 2022)

I recently fitted a cheap (£130) two axis DRO to my Sieg X3L mill.
The DRO came with glass scales, one at 250mm long which I fitted direct to the Y axis. The other was 1000mm long and I cut it down for the X axis.
Before that, I had three of the Igaging type magnetic readouts.
I have kept the one on the Z axis. I very rarely use it, as the mill had a built in DRO on the quill which I use for all depth setting.


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## Mike Henry (Jun 13, 2022)

DROPros sells pretty decent DROs in various flavors and some of their offerings can be cut to size by the user.  Their web site in California has lots of info.



			DRO PROS Digital Readout beats Heidenhain Newall Acurite Sargon Fagor


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## mole42 (Jun 14, 2022)

Peter Twissell said:


> I recently fitted a cheap (£130) two axis DRO to my Sieg X3L mill.
> The DRO came with glass scales, one at 250mm long which I fitted direct to the Y axis. The other was 1000mm long and I cut it down



Those Vevor units seem quite good, I fitted one on my Drummond Roundbed. I was a little wary of cutting the glass scale but it went perfectly well and has maintained the 0.0005" readout. I was disappointed with the iGaging ones, although they are small they only measure to 5 thou but I still have one that I may try and fit to my pillar drill for the Z axis.


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## Peter Twissell (Jun 14, 2022)

The Igaging readouts which were on my mill read to 0.05mm.
I am thinking of fitting them to my Roundbed.


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## kop (Jun 23, 2022)

I got the mill trammed in. (not much to do it was very close) and made the usual minor adjustments. I started it up and there were a few odd noises and ...

Just how warm are these bearings supposed to get? Just a few minutes and I couldn't leave my hand on the top of the spindle. I'm getting some heat off the bottom bearing but the top bearing gets positively hot. 

I'm no stranger to proper bearing preload. Am I missing something here? Is there a one lube to rule them all? 
I had dial indicators on the top and bottom of the spindle. I counted down from .002" , .001" , .000-something then barely 15 degrees on the preload collar. Heat, and lots of it. 

These are very common automotive bearings. 

Timken 09074 Tapered Roller Bearing
Timken 09194 Race

Timken 15118 Tapered Roller Bearing
Timken 15250 Race

Standard stuff from your local auto supply store.

Any bright ideas ?


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## Peter Twissell (Jun 23, 2022)

15 degrees on the nut might be a lot of preload on a stiff spindle.
Is the spindle easy to turn by hand and smooth?


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## kop (Jun 23, 2022)

An energetic spin of the pulley by hand (without the drive belt of course) will result in the spindle freewheeling between a turn and a half and two turns.


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## Peter Twissell (Jun 23, 2022)

That sounds about right.
You mentioned most of the heat is at the top. It's not just from the belt and pulley is it?


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## kop (Jun 23, 2022)

The belt has only the necessary tension. All the heat is right at the top of the spindle. The more I think about this The more I think wrong lube.


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