How to make hole for taper pin ?

[MecGen]

Hello people

I want to drill a taper hole to use a taper alignment pin. The details are :

Taper pin, 6mm small end, 7.4mm big end, 60mm length. I have these in stock from my PM mill rebuild. I can only go about 20 to 25 mm deep - blind hole, but leaving 35mm above is not an issue. This seems to be a popular size as drill bits and a tapered hand reamer can be easily had at Amazon. If I was to go for the correct sized pin, 20mm long, I would have to order that from China with at least a month delay, which is not the end of the world if I had to, but to complicate things, finding specs on the reamer pitch for those pins is not evident (the 60mm reamer specs is very clear).

I guess my question is, am I doing this procedure correctly ? If I take a 6mm drill bit, drill to depth, then ream till I get the fit needed ? Should be good ?. If I was going the full 60mm depth, I would use a 6mm and a 6.5mm (halfway) drill bit to ease the strain on the reamer ?

Sorry for the question, I have never done this. I will post the links in Amazon if you need more info to guide me.
Thank you !

https://www.amazon.ca/gp/product/B0BCQHQ2FX/ref=ox_sc_act_title_2?smid=A2U2IW4XM8RL4X&psc=1

https://www.amazon.ca/gp/product/B0BD5DBPXW/ref=ox_sc_act_title_1?smid=A2U2IW4XM8RL4X&psc=1

https://www.amazon.ca/gp/product/B0CZ9NDD7H/ref=ox_sc_act_title_3?smid=A1H7SZ6E7GRTDF&th=1

 

[RobinHood]

The taper is 1:50 in the metric system.

You can cut your 6mm x 60mm tapered pin to size.

Your 6mm drill will probably drill a bit oversize.

If the application is critical, I would practice on a scrap piece with a through hole and a 5.8 or 5.9 mm drill. Use the 6mm tapered reamer and fit your tapered pin. This will show you how much you need to cut off the thin end of the pin to make it work before it bottoms out (and thus not hold).

 

[MecGen]

Good idea. I will look for a smaller drill bit. I had thought about cutting th pin to length but it it tapped for ease of removal in the future. I know I really needed that feature when I took apart my mill.
Thanks

 

[CWelkie]

It might be worth thinking about step drilling the hole if you have drill bits in small enough increments. (Perhaps 3 steps equally spread over the depth.) This will considerably lower the stress on the reamer as it cuts the larger end of the taper. It may not be an issue with a 6mm pin but is something I do with much smaller ones.

 

[PeterT]

That's a very good point. I 'think' 1:50 is referencing angle between center line & pin surface like in section view. So ArcTan(1/50) = 1.1457 deg = 2.2915 included angle.
An M6 tapered pin (6mm big end) x 15mm long would equate to 5.4mm dia at the small end. Maybe not worth the effort of stepping the drills. But M6 x 30mm, small end turns into 4.8mm so probably steps
If my math or assumption is wrong, please correct me. I was looking at this same issue for smaller pins. Some of the operations I saw in mild steel just reamed a single pilot hole size at about this same 5:1 length : diameter ratio. Ali carries these reamers and in carbide

 

[MecGen]

It might be worth thinking about step drilling the hole if you have drill bits in small enough increments. (Perhaps 3 steps equally spread over the depth.) This will considerably lower the stress on the reamer as it cuts the larger end of the taper. It may not be an issue with a 6mm pin but is something I do with much smaller ones.

That would be my plan. I would at least have 2 different size drill bits, 5.8mm and maybe a 6.something.mm. I have to take the pin and muck around with my depths and measure the pin at that same depth to get a better idea of the size of bit vrs the depth of cut. I am worried to break the reamer in the hole.

 

[MecGen]

That's a very good point. I 'think' 1:50 is referencing angle between center line & pin surface like in section view. So ArcTan(1/50) = 1.1457 deg = 2.2915 included angle.
An M6 tapered pin (6mm big end) x 15mm long would equate to 5.4mm dia at the small end. Maybe not worth the effort of stepping the drills. But M6 x 30mm, small end turns into 4.8mm.

If my math or assumption is wrong, please correct me. I was looking at this same issue for smaller pins. Some of the operations I saw in mild steel just reamed a single pilot hole size at about this same 5:1 length : diameter ratio. Ali carries these reamers and in carbide


View attachment 61642View attachment 61644

View attachment 61640

In my case I would be using a 6mm at the small end and 7.4mm at the big end. These were everywhere on my PM mill so I have them in stock. Fast Google search turned up this reamer which made me think it was more of a popular size. Thanks