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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: EN3 bowing after machining
16/11/2019 18:45:40

We used to stress relieve steel at 190C for a couple of hours and then cool naturally. This is in domestic oven territory. It might work on cold rolled mild steel. We just made 11 10mm threaded  tee nuts for 1/2" wide slots from a 300mm length of key steel and didn't notice any bowing.

Edited By old mart on 16/11/2019 18:46:35

Edited By old mart on 16/11/2019 18:48:05

Thread: Wobble and Morse taper
16/11/2019 17:49:20

_igp2487.jpg_igp2486.jpg_igp2485.jpgI have taken some pictures of the rotary broach I made. The bearings are a double row deep groove and a thrust bearing, the er25 collet works for different size cutters. The number etched on the side is the length the cutters must project to have their tips at the null point. I made cutters for square and hexagonal holes.

_igp2484.jpg

Thread: Grinding and cutoff discs for angle grinders
16/11/2019 17:35:24

At the museum today, I destroyed all the grinding and cutoff discs which were out of date, including my own which were the oldest. All that are left are about 8 Dewalt cutoff discs which have 2021 on them. My little 76mm discs for the 12V Parkside angle grinder have a date of 2022. I also have some Parkside 76mm general purpose carbide edged metal discs which also have the 2022 date on them, despite having an indefinite lifespan.

Diamond discs work for metal, but aluminium may clog them, and steel and cast iron will reduce their life as ferrous metals have an affinity for carbon, which means the diamonds dissolve in the iron when they get hot.

Edited By old mart on 16/11/2019 17:38:57

Thread: Hi guys just bought a Harrison m300 and looking for info etc
15/11/2019 20:58:33

Have you looked on the Lathes UK website? They also have manuals and parts lists.

Thread: Grinding and cutoff discs for angle grinders
15/11/2019 19:49:43

I looked at lots of adverts for angle grinder discs, and not one seller was admitting to the date of expiry.

Thread: To pin, or not to pin
15/11/2019 19:42:38

You must post photos as you go. It looks like it will be a nice machine when it is finished.

15/11/2019 16:38:26

That is a similar reasoning that I came up with when I decided to increase the spindle of the Tom Senior mill from MT2 to R8. The bottom bearing is increased from 1" bore to 35mm bore.

There are several ready made small mill lower parts which have the X and Y axes on the market which are potentially very useful when making a mill. I found this one, but there are larger ones about.

**LINK**

Here are some pictures of the two halves of the spindle which was bonded with Loctite 620. No pins were needed as the halves also screwed together._igp2435.jpg

Edited By old mart on 15/11/2019 16:43:44

Thread: How do I undo these leadscrew nuts?
15/11/2019 16:26:23

I replaced the thrust bearings with metric ones, they were slightly greater od, so the housing bores had to be enlarged. The new bearings are heavier duty.

Thread: Who invented the elastic band?
15/11/2019 16:22:26

I'm not at all sure, but isn't rubber a product originating in South America? And what we now call rubber bands could not have predated Goodyear's invention of vulcanising.

Thread: Grinding and cutoff discs for angle grinders
14/11/2019 21:42:32

That's why I asked, having never thought about that subject before. I can destroy the entire stock of out of date discs now to prevent an accident and the bad publicity that would ensue.

Thread: Metric micrometer what t buy?
14/11/2019 20:33:23

There are digital mics going for £40 upwards, I have no personal experience of one, they may be ok for home use.

Thread: Wobble and Morse taper
14/11/2019 19:44:53

I made one using a MT2 soft blank, and it works ok for small sizes up to 3/8". It does flex a bit but I never noticed any loosening when in use. If I remember, I will take some photos of it on Saturday. The MT does not use a drawbar, It had never crossed my mind that it might need one.

Edited By old mart on 14/11/2019 20:28:58

Thread: Grinding and cutoff discs for angle grinders
14/11/2019 19:38:53

One of the volunteers at the museum drew my attention to our stock of discs for angle grinders. There is a date on the metal centre of each disc. This is not a date of manufacture, as the newest ones which were bought only a year ago have 2022 on them. Most of the others have dates of 2017 of older. I had no idea that these items might have a limited life, some of my own were bought in about 2002, when I bought my angle grinder.

Are these dates relevant? Do we have to destroy them even if they are unused?

Thread: To pin, or not to pin
14/11/2019 19:03:14

I had to get a joint apart and it was still a tough job even at 300C, you should try it some time, the data sheet errs on the side of safety, with litigation in mind.

Grub screws are fine if there is a decent wall thickness for the threads.

Edited By old mart on 14/11/2019 19:05:06

Thread: Metric micrometer what t buy?
14/11/2019 18:55:58

I have more than enough measuring instruments from when I was working, I actually sold three digital Mitutoyos for an average of £60 each as they were not being used. I did buy a 25-50mm micrometer for only £14 new not so long ago, it was NOS made in the DDR, which means it predates the unification of Germany. It is top quality with instructions, a length bar and a nice box. Worth looking on ebay in case there are any left.

Thread: 1.75". Chuck backplate.
13/11/2019 19:33:09

Smart & Brown use a 1 3/4" X 8 W spindle thread, with a 1 3/4" diameter register.

Thread: To pin, or not to pin
13/11/2019 19:29:09

If you can keep the temperature below 300C the Loctite will be ok. Two smaller taper pins spaced evenly in the 50mm joint and at right angles to one another would retain most of the original strength of the joint. 2.5mm pins would be a good size.

Thread: I cannot disassemble the X axis lead screw
13/11/2019 19:21:39

Why dont you start at the handle end.

I removed that taper pin on the one I was working on simply because I was increasing the length of the leadscrew thread, otherwise I would have left it alone. The pinned part needs supporting while you punch the pin out, just hitting the small end of the pin risks bending the leadscrew.

Thread: Bantam - warped compound gib
12/11/2019 19:59:24

If you have pretty well straightened it, you might as well see if the twist can be reduced, by using a vise and an adjustable spanner. The only way to get it settled completely, assuming it is steel and not brittle, is to go a tiny bit past straight, and then push it back by hand.

Thread: To pin, or not to pin
12/11/2019 19:27:13

The racks pinion shaft on the museums Smart & Brown model A apron was very badly worn on the od particularly next to the gear where it ran through a bronze bush. The bush was easy to replace, but the shaft and gear was not. I turned up a new shaft with a reduced diameter where the gear went, and bored the old shaft to the same size deeper than the width of the gear. The gear was then parted off the old shaft and Loctited onto the new shaft with 638, after thoroughly degreasing the parts. The joint was about 5/8" diameter by 1/2" wide. After the rest of the wear in the apron was attended to and it was re assembled, there was a suspicious amount of slippage. The Loctite wasn't enough. Mike found some 1/16" diameter needle rollers, and he drilled the joint axially in three places 120 degrees apart and Loctited them in place after cutting them to length. Fortunately there was enough thickness of metal to do this and it has been ok ever since.

Your joint length is nearly 4 times as long as the one I had made which slipped, which is a good sign. If you do decide to use a pin, then fitting a properly reamed taper pin would be much better than a roll pin.                                The strength of the joint is increased if the surface finish of the components is not too smooth, a ground finish in one half of the joint would not be as good as if both were being turned.

Edited By old mart on 12/11/2019 19:33:56

Edited By old mart on 12/11/2019 19:45:55

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