Member postings for old mart

I broke a 1/4 bsf tap about three diameters deep in mild steel. The drill had been undersize so I only had myself to blame. The workpiece was in the mill vice, so I left it where it was and used a solid carbide drill of about the core diameter using the fine feed very slowly. The carbide cut through the hss beautifully and I could just tip the remaining bits out. I re drilled with the correct size and found a replacement tap.

I would not want that to happen very often.

Key steel is tougher than mild steel, Boxford must have had a reason to use an unhardened one. If you make a close fitting replacement, which can slide with the minimum of play, it should be fine. Make a couple of spares, and maybe use a little moly grease when re assembling.

I would expect a metric lathe to have a metric leadscrew. The guy I bought my 7 x 12 Chinese lathe from bought it from Warco and took it home in his car. He had pre-ordered a metric version, but by an oversight, Warco only had an imperial one. They gave him a metric leadscrew and nut. I have them, still greased and wrapped up.

FC3 cutters are throwaway cutters.

With small cutters, you use the best speed the machine is capable of. The mill I use only makes 2100 rpm, but it doesn't stop me using 3mm solid carbides occasionally.

Why don't you measure the length of 10 pitches of the thread? Then it will be obvious what leadscrew you have.

All of the Chinese and Indian sets of tools I have, come in pine boxes which are varnished. I have some Mitutoyo measuring instruments in cedar boxes.

Google "lathes UK" site, find Startrite in the drilling machines column and look in Mercury page 2.

The 5 speed drills with the 2 knurled collars above the chuck are probably what you have. Two C spanners are required, hold the top collar and screw down the lower one against the chuck. Look up inside the chuck, there might be a screw head visible. If there is a screw, it must be unscrewed, most likely a right hand thread. The chuck should eventually drop off, so have a soft pad to catch it.

To refit the chuck, make sure the male and female tapers are clean, and screw the lower knurled collar back up to the top one. Retract the chuck jaws below the body, hold in position and give it a sharp rap with a copper faced mallet. Or use something soft like aluminium to cushion the blow from an ordinary hammer (1lb hammer would do). Refit the screw if there is one.

There are several illustrations of a Morse taper adaptor which screws in place of the regular chuck. When you have more experience of producing threads and taper turning, it would be easy to adapt an er16 collet chuck to fit the drill. 10mm cutters would be the largest size I would contemplate using with your drill.

Edited By old mart on 25/06/2019 18:32:14

Which Model of Startrite Mercury do you have? Does it have more than 5 speeds?

If yours has a knurled collar above the chuck, then the chuck is quick change type, and using your lathe, you could make a secure milling head, say er16 collet type. If the bearings are in good condition (no detectable radial play), then the machine should be capable of managing up to 10mm cutters.

Edited By old mart on 25/06/2019 16:19:32

The preload on the bearings should be only slight and can be empirically tested easily. You run the machine at maximum speed for 20 minutes, the part of the casting nearest to the lower bearing should get luke warm. Cooler may require a tiny bit more preload and the opposite if it gets over luke warm.

Creep up to the point of contact using a dti to check for radial play.

Leave plenty of room for any excess grease to be displaced away from the bearings (don't overpack).

Would the name be connected with JCB?

If you do that, never clout the chuck key with a mallet to unscrew it. It shock loads the gears and can split the ends of the screws on four jaw chucks. Use a strap wrench and gently increase the torque. If the spindle can be locked properly, then get in the habit of using it correctly. Tightening a collet should not require as much effort as unscrewing the chuck.

I have on order from China a 25 X 25 toolholder for 22 size carbide threading inserts. The 20mm holders only go up to the 16 size. So I will have to reduce the height by 6.47mm to fit the lathe, I'm not looking forward to doing it.

Dave, your carbides must be made from HTC (high tensile cheese) bin them now.

The telescope is fixed to the far left end opposite that balance weight.

There is a site with some of the most common thread charts : www.motalia.com

Is there any way to drill a 10mm hole for a drawbar in the drill spindle? MT2 milling collets use a 10mm thread, unless they are old when a 3/8" W is the nom. Even in a mill with a drawbar, drill chucks have their own short taper which makes them unsuitable for holding milling cutters. I have occasionally held milling cutters in a drill chuck to plunge cut like a twist drill, but never to cut sideways.

We have a Seeley one at the museum, it folds up easily, but could also be easily dismantled with a couple of adjustable spanners into lots of much more manageable parts, just take some photos first.

1. My experiance of hard anodising is only with aircraft components which are produced to higher specifications than usual. My firm used to make uplocks for Airbus landing gear which had hydraulic actuator cylinders with a bore of about 3/8". The anodising was about 0.002" thick and was ground in house to a mirror finish, the unground ends of the cylinder were smooth, but not as good a finish as the bores. These pictures are of a hard anodised and ground tube which the swashplate spherical bearing slides up and down on for a helicopter. Possibly, a Bell Jet Ranger. The grinding may be visible in the photos. The diameter is about 4".

Edited By old mart on 23/06/2019 12:06:09

Hard anodising certainly does require grinding.

If I'm not mistaken, that lathe you have is a S & B model A.

Metric ones are commonly yellow.