hardened Stainless help

I need to drill two holes in digital caliper to mount it to a collar and rods I made for a cheap dro for my mill. I tried to drill a 4mm hole unsuccessfully. I guess caliper is about 5mm thick and all I managed was 2.5, wont go any deeper. I am going to get a couple more 4mm drill bits now but wondered if anyone had any tips for the operation before I butcher them lol. I was running about 600 rpm with the 4mm drill bit.

cheers,

Ady.

Ady,

Apologies: This doesn't answer your question; and I don't mean to hi-jack your thread

Has anyone tried these "carbon composite" calipers ?

... they might be easier to modify.

MichaelG.

Again apologies to Ady and just to answer MichaelG.

Yes I have got some of those, they only read to 0.1mm and accuracy is given as +/- 0.2mm. Also if you apply much pressure you can distort the jaws and get a false reading. The main shaft can also be flexed. So OK for a quick very rough check but not for anything requiring any degree of precision. They might just come in for using as a scale but again the relatively poor resolution and accuracy would go against them. Better units are available still for the right side of £10.

Keith

Yes - on some samples of stainless a high speed drill only has to skid one turn without cutting to create such work-hardening that further progress is all but impossible. Carbide works, but if you use your carbide drills for hammer-drilling concrete you will need to get yourself a green wheel for re-sharpening.

Thanks, Mike Keith

... Much as I feared ... I will save my £5.99

Strangely, the advert seems to quote resolution as both 0.1mm and 0.01mm

But also says: "Minimum Scale to read is 0.1mm/0.1"

So one of them "must be a typo"

MichaelG.

.

Edited to clarify the claimed resolution.

And again, to thank Keith !!

Edited By Michael Gilligan on 08/03/2014 13:50:19

Edited By Michael Gilligan on 08/03/2014 13:54:09

Ady,

I have used "glass drills", ie drills for drilling glass, which have a solid carbide spearpoint tip. They are also easy to sharpen up with a diamond slip. Start small, and change up to final size.

Don't let them rub, be positive.

Used them for the same job as you, drilling a digital caliper for a DRO on a drill.

Phil

MichaelG

PM sent

Keith

I have done this and seem to remember using a cobalt drill, probably with some Rocol RTD. You certainly could use a carbide drill; the Asbo brand, no longer advertised, worked well.

300 series stainless (austenitic) work hardens like crazy. Tends to gall easily so maybe not great for calipers.

400 series stainless (martensitic) may well be deliberately hardened from factory - I would guess this is more likely for calipers. Might drill, or grinding with a small point might work better.

Hi Ady,
I have drilled 2.5 mm holes in the back of the slider assembly on calipers using Arceuro's cobalt drills (I bought tapping size drills from this range.) and tapped them with a normal HSS tap. There may be a variation in the hardness of calipers from different manufacturers.

Hi Michael,
I have a set of the carbon composite calipers and I agree with Keith's comments. The only think I would add is that the data from the data port gives 0.01 mm resolution when connected to a remote display. (For example a DRO350 or my interface to "Yuriy's Android DRO.)
I have seen stainless calipers on sale recently in Aldi. These use the 1.5 volt button cells. I notice Lidl have the version that uses a 3 volt lithium cell on sale for £8.99 on the 13th of this month. I think the battery life is better on the lithium cell versions.
Les.

Edited By Les Jones 1 on 08/03/2014 14:54:01

The secret for drilling stainless is lube, speed, never back off on the feed and bit of luck.

I have an ancient and cheap pair of plastic digital calipers. They are ideal as a hack pair for keeping in a pocket to see if bootsale/scrap box bar is 10mm or 3/8", that sort of thing...

Neil

Hi,

saw this 40 years ago,

but slow is good ( less heat )

HSS drill sharpened correctly, mix some Bi Carbonate of soda to make a mulch ( like butter )

gently drill with bi carb, it does work BUT DO NOT RUSH, but make it cut !

Rich

Keith & Les,

Thanks for the updates.

MichaelG.

Ady,

I had a similar problem, but needed to drill 4 holes (for M3 screws), to make a depth DRO for my Super7 tailstock.

I managed to drill the holes in the "fixed" leg (i.e. the one which did not contain the electronics) but had the same trouble as you with the other two holes. My solution was to strip all the plastic parts off the caliper "carriage" , heat it bright red with my blowtorch and then anneal it, by quenching in water. I then had no trouble finishing off the part-drilled holes.

Hope this helps.

Regards Tom

It's called blue sky tolerancing which roughly means no matter what's posted no one gives a rats arse.

.

Thanks John ... very helpful

Not a problem, like to help with practical answers.

I am suprised that Tom's method of softening SS worked. Shouldn't it be a very slow cooling with any alloy containing iron. As already stated, keep the pressure on, plenty of coolant, sharp drills.

For drilling stainless or other hardish steel up to 65 Rc the drills at the link below work really well. I bought a 1/8" one and have used it to drill calipers for mounting (among other things). If the 1/8" hole size is used, a #4-40 UNC screw passes easily, and a 1/8" 'c' style roll pin fits with tension in the hole to locate the jaws to mounting brackets with zero backlash.

http://www.maford.com/products/index.aspx?series=200

Good luck, JD

PS you need PLENTY of drilling downforce to make these drills cut. Push them hard and they work great.