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Member postings for old mart

Here is a list of all the postings old mart has made in our forums. Click on a thread name to jump to the thread.

Thread: Self extracting drawbar for mill
14/05/2022 18:20:45

The nut is made from bronze, and the lower end of the drawbar has whatever threads are appropriate for the tooling. These threads extend as far as the nut needs to be screwed onto the drawbar. After degreasing the threads on both parts, I used Loctite 620 as a thread locker, even though it is intended as a sleeve and bearing fit. This is because it is very slow curing and the length of the nut can cause slight friction which makes most other grades such as 270 threadlocker harden before the nut is in its final position.

If there was enough size of cavity to fit a long nut with sufficient wall thickness, then top and bottom parts of the drawbar could be loctited into the nut. You mentioned boring the spindle, but that would involve much more dismantling than just making room for inserting the drawbar from the bottom.

The nut has to rotate with the drawbar, it is not glued into the spindle.

13/05/2022 22:32:27

With the Tom Senior light vertical it is just possible to lower the knee far enough to fit the drawbar from the bottom without swinging the head. It would be a problem if the drawbar couldn't be fitted that end of the spindle as that nut inside has to be loctited so it cannot slip when it is used for breaking the taper. Removing the bed might give enough clearance, or even the Y axis part. Otherwise the head would have to come off. It can be done if you are determined enough and sure that the mill can be reassembled ok. Another way would be to remove the quill if there is one.

Thread: Looking for a Sharpening Service for End Mills & Slot Drills please
13/05/2022 17:12:44

Drill Services of Horley in Surrey, near Gatwick may sharpen small batches.

Edited By old mart on 13/05/2022 17:13:09

Thread: Self extracting drawbar for mill
13/05/2022 17:10:12

Having the Tom Senior R8 without the pins has had certain benifits, one is that you can clean the internal tapered portion with one of the BT30 taper cleaning wipers. The only disadvantage is if using an R8 collet, it can sometimes turn and there is nothing to hold onto. I make sure if using one, that the 7/16" thread is clean and lubricated with moly grease. The head end of the collets could be drilled with a small solid carbide drill axially in 3 places to use a ring tool with pins to stop the collet from turning while being tightened or loosened.

Thread: Researching Godalming's Old (Goods) Railway Station
13/05/2022 15:56:07

I may be imagining it, but I seem to remember seeing sets of buffers visible from the bus in the early 60's.

Thread: Barograph 'stiction'
13/05/2022 15:52:54

Little vibrators were clamped on some aircraft instruments such as ASI's and alitmeters if the instrument panels did not have enough engine produced vibrations. With a slow moving instrument like a barograph, something timed to give a little tap every few minutes would be more suitable.

Thread: Self extracting drawbar for mill
13/05/2022 15:44:36

If there is a shortage of space for an extraction nut, it might be possible to shorten the ends or the MT3 tooling, provided there is at least 2 diameters of internal thread left afterwards. This could be done by hand on a bench grinder. Depending on how hard the spindle is, a little bit of boring could well also work. If the pressure face is rough, a cone shaped thick washer to give a flat thrust face might work.

Thread: Minimum depth of cut possible with carbide tooling on S7
13/05/2022 15:31:28

We find that the aluminium grade polished sharp inserts are very good for finishing cuts on steel. You can get away with spring cuts where a common blunt edged insert would just rub and leave a poor finish. The only way to be sure of a good finish with the harder material grades is to make your last cut deep enough to work properly. Most people would not want to chance a final deep cut and would be happier creeping up on the size, this is where the polished "GT" types come into their own. Try a box of the Chinese ones, their quality has improved greatly in recent years. The aluminium grades will put up with some interrupted cutting, I often bore soft jaws with them. WNGT06 is a trigonic insert with 6 cutting edges and may be small enough to use in Myford size lathes in 12mm holders.

Thread: Researching Godalming's Old (Goods) Railway Station
12/05/2022 19:50:50

_igp2948.jpg_igp2947.jpgI have found evidence on Ordnance Survey maps. The modern Explorer 145 shows two roughly parallel unclassified roads running approximately N-S ending at a school near the roundabout on the A3100. The much older 1" to the mile OS 124 printed in 1920 actually shows a section of track in the same position.


12/05/2022 18:20:55

It was just north of the river Wey, about 1/3 mile from the present Farncombe station, a housing estate now.

Thread: Milling Table Flatness - What is acceptable
12/05/2022 18:17:30

Since the measurement with the DTI agrees with the bed being thicker at one end, you can be fairly certain that having a machine shop skim the minimum to clean up will solve that problem. It would be worth doing simply for peace of mind, and a milled surface is fine for a hobby mill bed.

Thread: Self extracting drawbar for mill
12/05/2022 18:05:07

I did this with the R8 conversion of the Tom Senior light vertical. R8 tapers were designed for mills with drawbars and it is easy to break the taper. The MT3 taper requires more force and I wonder if a bronze taper breaking nut would be the answer, assuming yours is steel. The one I made (shown in black in the drawing) is bronze. Also I used some moly grease when fitting the spindle.

I am thinking of doing away with the R8 location pin in the drill mill, and making that a captive drawbar also, an excuse to fit some SKF taper roller bearings and mill some spanner flats near the bottom end of the spindle.

Thread: Milling Table Flatness - What is acceptable
11/05/2022 19:59:27

As already mentioned, you need to measure the thickness of the bed at both ends to see if the error is there. If the thickness is the cause of the problem it would be worth visiting some small local machine shops and seeing whether they could put it right and how much it would cost. Make a drawing to show them. I would be happy with a milled surface, we had to hand rub our bed because I had no choice but to mill in 4 stages because of the size relative between the two mills.

11/05/2022 17:23:11

Hi Peter, as long as you know the limitations of your machinery, and the errors, you will be able to produce very good results. Most work is a lot smaller than the bed, so knowing the sweet spot is the best war to proceed. The drill mill at the museum had an error in the bed slots, so using a pair of keyed vises would have had a Y axis error of 0.007" , 0.18mm over the length of the slot. I milled the entire length of the rear face of that slot in three stages, swinging the round column to the left and right taking zero off one end and the 0.007" off the other, and now the vises can be spaced anywhere as a pair with less than 0.001" error. I only checked the particular slot which suited the 100mm Bison vises best.

When the museum was left the Tom Senior light vertical mill in a legacy, it was not in working order and the top of the bed was not a pretty sight. I sat the bed on four 1-2-4 blocks on the drill mill and and milled off 1.5mm,  0.059", then we spent months rubbing it by hand upside down on the surface table. The surface table had sheets of wet and dry paper stuck on with double sided tape, we ended up using 120 grit paper. Over 90% of the damage has been removed and the table is flat within 0.001" 0.025mm. This could be done with your bed, but is a real challenge to do.

Knowing the error, you could simply shim up one end of a long workpiece if needed.


Edited By old mart on 11/05/2022 17:35:06

Edited By old mart on 11/05/2022 17:37:25

Thread: Easy power tailstock feed for your lathe
10/05/2022 15:18:42

When we were working on the museum's Smart & Brown model A apron there was no way to use the lathe to produce the bushes and spindles needed. I did the exact opposite, using the tailstock to push the saddle using an extra piece of metal bar in the four way toolpost. I backed off the tool and manually returned the saddle to the start position after each cut.

Thread: Colchester Triumph 2000 - Topslide Leadscrew Threadform
08/05/2022 16:45:57

I have just produced 4 leadscrew nuts for the museum's drill mill in 2.5 mm pitch. The threadform is trapezoidal for most metric pitches which has a 30 degree flank angle. The er/ir16 inserts that I used would not be suitable for a 5/8" or 16mm size, the leadscrews I made them for are around 22mm diameter, and 3/4" or 20 mm leadscrew diameter would be the minimum size that they can enter.

There are ready made nuts available from an ebay advertiser, the price varies accordingly to how sophisticated the nuts are, but are worth a look.

Edited By old mart on 08/05/2022 16:50:26

Thread: SENIOR Mill for someone?
06/05/2022 17:22:16

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

Thread: Smart &Brown L.tailstock lever
06/05/2022 17:16:19

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.

06/05/2022 14:22:13

_igp2924.jpg_igp2923.jpgI have a parts drawing of the model A tailstock, no dimensions unfortunately but it probably is similar to yours.


Thread: Smart & Brown model M bargain
05/05/2022 17:16:25

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.

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