Member postings for old mart

It would be a great buy for somebody, it has the name Centec on it so probably not Senior.

At the bottom of the model A drawing is shown the head of a SHCS which is used to adjust the point of clamping, it screws into the L4 2063. Unfortunately, I would not want to take the museum's tailstock apart to measure the mechanism as there are a number of bits of shim steel inbetween the top and bottom castings to get the tailstock aligned with the headstock because of wear and it was not a job I want to repeat. We never change its alignment, with a taper turning attachment there is no need.

I have a parts drawing of the model A tailstock, no dimensions unfortunately but it probably is similar to yours.

Probably the same size as the Model A, the front one is 2" bore and 2 3/4" long and the rear is 1 9/16" bore and 2 1/4" long. The Mk 1 and 1.5 run to 1430rpm and the Mk 2 is 1800rpm. The bronze bearings are made like er collets, the bore is parallel and the od is tapered. The headstock bores are tapered to match and nuts both sides of each bearing adjust the clearance.

I couldn't resist a NOS tailstock on ebay some time back, it is of Chinese origin, MT2 with a 3" stroke and with a suitable base section made, could fit the Smart & Brown model A at the museum. Seeing this thread, I can imagine it modified for lever operation for those delicate small drilling jobs.

For anyone looking for a small lathe, but not lightweight by any means, there is a Model M on ebay with lots of tooling.

**LINK**

Stueee's link to Kingston engineering shows their data sheet 3, but unfortunately their easily available ACME 10 tpi is only 1/2" not the op's 3/4". The 3/4 x 8 ACME is available in rod and nuts, a possibility if the dial graduations could be changed. There are a great many more suppliers over in the USA, but unless you know somebody living there it can be difficult and expensive to ship things to the UK.

Some of the cheap collets leave a lot to be desired in the accuracy department. Collets from an industrial supplier such as APT are available in different grades. I have an er25 R8 collet holder that has a runout of 0.003" tir in the internal taper, there is no way I can easily fix that, so it is not used.

**LINK**

On Thursday, Rod finished the wiring for the Atlas 12 x 24 lathe. When it was switched on, there was vibration and the motor tended to jump up and down. We think that the pulley driven by the motor pulley is the cause of the rough running. It can be seen running as if it has been bent. What it is is the fit on the 3/4" shaft is not very good and when the grub screw which clamps onto the key is tightened the pulley cants slightly. When the pulley pair was removed, there was no sign of it being bent, but the hole was in need of bushing. At 9" diameter, it would just fit the Smart & Brown faceplate, and Rod lined it up with a lever indicator running at the bottom of the belt groove to about 0.002" tir. I bored the pulley from 3/4" to 1.210" to suit a piece of 31mm gunmetal that had a 14mm hole in it and turned the gunmetal to just thinking of going in fit. The gunmetal was parted off at 1.3" long to match the boss, and degreased before using the press and Loctite 620 to fit. It needed the press to fit which was done still on the faceplate which will be screwed back on the lathe for final boring to fit the 3/4" shaft. I may drill and tap the rear of the boss for a couple of 6mm screws to ensure the bush never moves in the pulley.

On Saturday, I will be thinking of a key slot together with a new locking grub screw hole in the pulley.

I fully agree with Jason regarding the flange mount in conjunction with a backplate having potential adjustability for radial runout, and have the through hole for longer work. We have one in er25 to utilise the collets used on the mills. For a lathe, however, the er32 would be a better choice as it can hold up to 20mm stock.

**LINK**

Edited By old mart on 29/04/2022 16:53:32

You need to state the mill you will be fitting it to.

Go for the larger, assuming it will fit in the space ok. Then you can run it at lower rpm and still have twice the power that a 1/2 hp motor would have. If you are concerned with the motor being too powerful for the lathe design, just slacken off the belts a bit so they will slip. The museums Smart & Brown model A has 1.5hp, but in deference to its age, I allow the final drive belt to slip if the torque gets very high, particularly when drilling holes about 1" diameter in steel.

I have heard that there is difficulty getting hold of any of the Arduino or Raspberry pi due to the computer chip shortage.

We have a collection at the museum, a 160mm Chinese 4 jaw independent, a 6" lightweight four jaw independent by Toolmex, 2 x 5" Pratt Burnerds 3 jaw scroll, a 125mm Chinese 3 jaw scroll, a 160mm Indian 3 jaw scroll, a Burnerd 6 3/4" three jaw scroll serrated jaws, a 4" Pratt Burnerd 3 jaw scroll. Also, an 80mm three jaw scroll (ex my mini lathe) on a revolving MT2 for the lathe tailstock. Three faceplates and the original Smart & Brown collets.

The all get regular use except the 80mm, we haven't found a job for it yet. THE 6" 4 jaw and one of the PB 5" are also used on a rotary table. There is also an er25 collet plate that fits on the lathe.

The 125mm Chinese chuck and the 5" PB's would seem the same, but the larger jaws in the 125mm give a welcome overlap in the work they can hold, especially with the external jaws.

 As for your choices, make sure you keep the best ones and be sure that there is some overlap in the holding capacity. It sounds that the griptru might be the one to go, have you tried any of the other PB jaws in it?

Edited By old mart on 25/04/2022 21:14:12

Edited By old mart on 25/04/2022 21:17:25

When I was a kid, I was given a stereo camera with some glass plates of toboggons on the Cresta Run. The camera was made of bakelite with a detachable front which housed the shutters and sliding apertures which were just a set of paired holes. With the front off, the body could be used as a viewer, using the single element meniscus taking lenses. The glass plates were about 4" x 1 1/4" with a pair of 1 1/4" images. The images were monochrome reversal, not negatives. I think the camera was German, and often wonder if it would be valuble now if it had not been eventually destroyed by me.

The mill drill tee slot which was appropriate for the 100mm Bison vises had a 0.007" error from one end to the other. It has a 500mm stroke, so the length is more and because it has a round column I was able to mill the entire rear sheer if that slot in three stages by swinging the head. The error along the entire length of that sheer is about 0.0005" from end to end. It helps when both Bison vises are used together for a long workpiece. I haven't bothered to check the other three slots for runout.

I have some special sheet metal drills designed to drill unsupported sheet alloy such as aircraft skins. They drill a perfectly round hole because there is no relief on the outside like normal twist drills which tend to leave triangular lobed holes.

If possible for flat sheets, the sandwich method is best to reduce distortion.

Rotary bases are things that are rarely needed, spending most of their lives in a cupboard, but they can be well worth having occasionally. We have at the museum a large rotary and tilting device which originally held an 8 inch rotating top like the top of a rotary table. We have used it in the drill mill, but it is much too heavy for the Tom Senior, the top is modified to take one of those Bison 100mm vises or a 6" four jaw independent chuck. It has been used once this year, but I can barely lift it, and it takes up about 10" of Z height before the vise is fitted. That has a pin to set the tilt horizontal when not in use, that is where I got the inspiration for the rotary vise base.

We have 2 of the Bison 100mm vises at the museum, the original came with the drill mill and the one in the pictures was NOS with the base which I was very lucky to pick up on ebay for around £100. They are keyed for both mills to be used as a pair if needed. The only shortcomings of this style of vise is the limited opening, only about 80mm and the jaw lift which cannot be eliminated, even by devious means, I have tried with limited success.

Edited By old mart on 24/04/2022 15:56:32

Just to really wind up the haters of milling vise rotary bases, we have been modifying one of the Bison 100mm vise bases. The object was to set one of the 100mm's on its rotary base and make keys for it to fit the Tom Senior and the drill mill. Mike made the keys, four as they have to fit different width slots in the two mills. The base was lined up with the vise and clamped up and I tried the keys as made to find what the error was. It was only 0.004" across the entire width of the jaws. I had thoughts od pinning the zero position and found there was room to have a 1/4" pin. So I slackened off the bolts holding the halves together and adjusted for zero tir across the jaws and retightened. The alignment marks for the degrees had not noticably moved, so I drilled a 6mm hole and used a 0.2498" solid carbide machine reamer so that an aircraft bolt with a ground shank of 0.249" fitted. The pin holds the alignment within +0 -0.0005" across the 100mm jaw width. I then fitted the second set of keys and tried the alignment on the other mill and to my surprise it was exactly the same. No extra fettling needed.

 I also looked at the 5" ARC versatile vise and base with a view to pinning it, but there is not really enough thickness of metal. So I cut off the lip at the rear of the casting instead to allow an extra 1/2" of Y travel when it is fitted to either mill.

Edited By old mart on 23/04/2022 19:02:55

Edited By old mart on 23/04/2022 19:09:50

I was glad to have solid carbide drills when I snapped a 1/4" tap in steel, it was not very sharp and the hole was a bit small. The carbide stub drill made removing the tap look easy, although I was rather apprehensive of the outcome.

I agree with DMR, the remains of the tap do look strange.

Edited By old mart on 17/04/2022 23:00:52