Diamond M20 horizontal mill

[Aaron_W]

This little mill just moved in, I didn't even know I needed one but now that I have it I'm pretty excited to see what I can do with it. A thanks to C-bag for posting the CL ad that helped this one find me.


It is a Diamond M20 5x20 horizontal mill, and appears to be mostly unmodified and in very good condition for a 75 year old machine. I think it still has the original paint. It came out of a shop not far from the ocean, and there is almost no rust on it, so the prior owner must have given it a lot of attention.
It was unfortunately part of an estate sale, so I have no information on the history of this machine. It was sitting on a newspaper dated 1984, so assume it had been in the shop that long.

From what I've been able to find the Diamond Tool Co started building small mills in 1943. This one is numbered 326 with a date of December 28, 1944 so it is an early one. The history nerd in me imagines the workers building this one glued to their radios as 12/28 was the day after Patton reached Bastogne ending the siege of the 101st airborne during the Battle of the Bulge.

It has a 3 speed belt driven power feed on the X axis. There is a removable sheet steel drip pan which looks different from others I've seen online, not sure if an early variant of the optional factory pan or something fabricated by a prior owner. Either way it is well made, not a hack job.

It came with a nice Palmgren vise and large amount of tooling.

This little mill is heavier than it looks, specs I found put it at around 800lbs with the base, and it felt every bit of that.

It seems a nice size to complement my Clausing 8520. The prior owner must have felt the same way as it sat next to an 8530 in his shop so should be feeling right at home in mine.

 

[markba633csi]

Nice collection you have there. My M-20 is even earlier: serial #212. Unfortunately, someone removed the nameplate so thanks for posting yours, now I know what lubricants to use
Mark
ps your Y axis crank handle looks like an owner modification

 

[brino]

Great looking mill.
Congratulations!
-brino

 

[Aaron_W]

Nice collection you have there. My M-20 is even earlier: serial #212. Unfortunately, someone removed the nameplate so thanks for posting yours, now I know what lubricants to use
Mark
ps your Y axis crank handle looks like an owner modification

I need to find one of these signs to go with it.




I've found a few differences, the crank being one, the drip pan another that differ but work well, so not sure if replacements or maybe some flux in production as they tried different things or dealt with supplier issues. The drip pan is different than that shown in drawings, but is heavy steel and looks pressed, not hammered so if custom fabricated it was done by someone with some skill and a big press.

That long handle makes cranking the knee up and down much easier. The cranks will fit on either side, so I can see how much less effort the long handle takes, although the smaller is better for small, more precise movements. Vintage Machinery has a 1946 ad for the B-12 which shows a similar style crank handle and there is a photo at Lathes uk showing an M20 with a long handle very similar to mine so maybe it was an optional item.

 

[markba633csi]

I've been wondering what the differences are between the B-12 and the M-20. I see the table on the B-12 has one slot, the M-20 has 3.
Otherwise they look very similar
Socony has an interesting history- reminds me of "there will be blood" movie

 

[Aaron_W]

Vintage Machinery has several ads and brochures for several of the machines, although not the M20.

This is what I've been able to put together on the different models (VM, Lathes UK and various online discussion forums, there are quite a few threads on these machines at Practical Machinist.)

All have a B&S #9 spindle, with 7/8", 1" and 1-1/4" arbors available.
All available with an optional 3 speed power feed on X axis.
All available with an optional coolant tank and pump.
Chain drive was an option on the B-12, M20 and 22-M (dual belts standard). M24 and M30 were chain drive.
It appears the motors specified were recommended, but the motor was an additional cost, so presumably there can be some variation of "original" motors.
All appear to be capable of using a vertical milling head (many of those found have one), but only the 22-M brochure shows that as an option.

lathes uk suggests that there may have been B models smaller than B-12, but no info on them.



B-12 (info from undated Diamond brochure)
9" vertical travel (Z), 12" side to side (X), and 6" in and out (Y)
5-1/8x20" table. It seems to have been available with either a single 5/16" T slot or three 5/16" T slots
6 speeds 98-1200RPM, 3/4hp motor
Can be bench mounted or ordered with a stand, 450lbs / 750lbs with stand
$698 with stand

M20 (info from lathes uk and my mill )
15" vertical travel (Z), 14" side to side (X), 5-1/2" in and out (Y)
5-18x20" table with three 7/16" T slots
9 speeds 85-1500 RPM (assuming same speeds as 22-M), 3/4hp motor

22-M (info from undated Diamond Brochure)
Appears to be identical to the M20 except for the larger table and motor
15" vertical (Z), 14" side to side (X), 5-1/2" in and out (Y)
5-3/4x24" table with three 7/16" T slots
9 speeds 85-1500 RPM, 1 hp motor
1000lbs
Optional vertical milling head B&S #7 spindle, 170-3000 RPM. Power from pulley on rear of horizontal spindle.

M24 and M30 have a 3 speed "silent chain drive" with a variable speed Reeves drive. The motor is mounted inside the base instead of hanging on the right side of the machine.

M24 - No specs found only photos, but similar to M30

M30 (info from undated Diamond ad)
10" vertical (Z), 18" side to side (X), 6" in and out (Y)
7x30" table with three 7/16" T slots
Variable speed drive 60-1400, 1-1/2hp motor
1225lbs
$1460