Author Topic: Bench Drill to Tapping Machine.  (Read 9141 times)

Offline Arnak

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Bench Drill to Tapping Machine.
« on: October 07, 2013, 06:07:04 PM »
Hi Folks,

Just in case anyone is interested in my pillar drill mod.
It is one of the cheap drills for fixing to a bench.

What I needed was a drill capable of using my tapping head but the depth was too short and the lowest speed, about 350rpm was too fast.

The first thing to do was to increase the length of the pillar by adding a suitable diameter of steel rod with the lower end reduced to fit into the existing hollow pillar.

I was going to pin it in place but the fit was so tight I was able to press it in.

Having increased the throat size I then needed to reduce the speed.

I managed that by adding some support steel strips to move the motor out far enough to add another shop made 2” pulley onto the motor shaft.

I used one of the stepped pulleys in its original place by adding a cross plate to hold a bearing holder with a bearing at the top and the bottom of the steel holder.

That holder is in slotted holes to allow for adjustment.

The position of the motor was set by the length of the belt I could obtain, just 1” below the original belt length.

I think that the pictures are self explanatory but if anyone needs more detail please ask.

Arnak


Offline Stilldrillin

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Re: Bench Drill to Tapping Machine.
« Reply #1 on: October 08, 2013, 02:17:46 AM »
Nicely Modded, Arnac!  :clap: :clap:

I need a similar belt mod  to my mini mill. The revs are much too high for my purpose.  :scratch:

Well done!  :thumbup:

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Arnak

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Re: Bench Drill to Tapping Machine.
« Reply #2 on: October 09, 2013, 09:47:20 AM »
Hi David,

I'm glad the info was of some use.

At least it is a cheap and cheerful way of lowering the speed.

You could of course make a new stepped pulley for the motor shaft to give more speed variation. :thumbup:

Arnak

Offline Steam Geek

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Re: Bench Drill to Tapping Machine.
« Reply #3 on: November 25, 2013, 08:11:30 AM »
How did you calculate the rpm to get the correct pulley sizing ?
Turning good metal into swarf

Offline Arnak

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Re: Bench Drill to Tapping Machine.
« Reply #4 on: November 25, 2013, 01:39:10 PM »
Hi,  Steam Geek,

Actually I didn't as all I wanted was toi get the drill to go as slow as possible from it's lowest speed which I think was about 500rpm.

Given that the smallest pulley on the compound original pulleys was about 2.25" I had to settle for that, any smaller and the belt may not have gripped properly.

You could try a bit smaller and see if it works, the ratio calculation is I believe driver dia divided by the  driven dia.

So the ratio of 2" to a 1" pulleys is 2 to 1, if the 1" is rotating at 1000rpm the 2" will be rotating at 500rpm.

That is the first step in the chain of drives, so once you have the speed of the intermediate pulley you make the same calculation with the intermediate pulley and the next one in the chain.

I hope that makes sense?

Come back if you need more help.

Arnak


Offline Meldonmech

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Re: Bench Drill to Tapping Machine.
« Reply #5 on: November 26, 2013, 03:57:15 AM »

 I have a tapping head which I want use, but have no room behind the drill to use your idea.  I have bought speed controller and am now looking out for a 220/ 440 dual voltage motor.

                                                                                                               Cheers  David

Offline mechman48

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Re: Bench Drill to Tapping Machine.
« Reply #6 on: November 27, 2013, 09:23:59 AM »
Hi all
For further info on pulley calc's I have att. pdf for ref. for everyone.
Cheers
George

George.


Always look on the bright side of life, & remember.. KISS..' Keep It Simple Stupid'

Offline mattinker

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Re: Bench Drill to Tapping Machine.
« Reply #7 on: November 27, 2013, 01:22:32 PM »

 I have a tapping head which I want use, but have no room behind the drill to use your idea.  I have bought speed controller and am now looking out for a 220/ 440 dual voltage motor.

                                                                                                               Cheers  David

A thought, you don't have to put the motor behind the drill, it could be next to it or above! Mount it the other way up, motor up instead of down.

Just my 2 €cents, regards, Matthew

Offline Joe in Oz

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Re: Bench Drill to Tapping Machine.
« Reply #8 on: June 01, 2014, 08:30:55 AM »
For future reference of others:
One of the better ways of getting a MUCH bigger ratio that with V-belts is to use a pair of tooth belt pulleys and belt. Something like 10mm wide XL belt is likely to be strong enough and will allow a ratio of something like 10:1 quite eaily in the space of the original belt cover.
So a 1440rpm motor will give you a spindle speed of 144rpm. Bigger ratios are achievable with intermediate pulleys and short belts, so even inside the original space you could envisage 2 lots of 10:1 for just 14.4rpm spindel speed - woth probably large tap breaking torque!
Cheers,
Joe

Offline hanermo

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Re: Bench Drill to Tapping Machine.
« Reply #9 on: June 01, 2014, 01:44:48 PM »
Toothed belt == timing belts.
The normally accepted max transmission with belts is about 1:3 or 1:4.

Ie You need 14 teeth in HTD to get good belt wrap.
(12 teeth) is not good, although they are sold.
A 50 teeth pulley at 1:3.57 is already about 10 cm in diameter, and 30€ each.

You need good belt wrap (so small size cannot be too small) and as good a rigidity as practically possible (shorter belt is better).
E.g.
If your big pulley is say 140 teeth (for 1:10) the belt becomes very long, as you wont get good wrap near the small pulley.
And thus you have a lot of space between the pulleys, which reduces rigidity.

So for 1:10. you would get 238 mm between centers, a very long distance.
Here is a calculator.
http://www.sdp-si.com/cd/default.htm

A 72 teeth pulley is 40$.
https://sdp-si.com/eStore/Catalog/Group/346#
140 will be about 100$++. (Very little production).

Offline Manxmodder

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Re: Bench Drill to Tapping Machine.
« Reply #10 on: June 02, 2014, 06:31:27 AM »
For future reference of others:
One of the better ways of getting a MUCH bigger ratio that with V-belts is to use a pair of tooth belt pulleys and belt. Something like 10mm wide XL belt is likely to be strong enough and will allow a ratio of something like 10:1 quite eaily in the space of the original belt cover.
So a 1440rpm motor will give you a spindle speed of 144rpm. Bigger ratios are achievable with intermediate pulleys and short belts, so even inside the original space you could envisage 2 lots of 10:1 for just 14.4rpm spindel speed - woth probably large tap breaking torque!
Cheers,
Joe

Hi Joe, I agree with your suggestion as a space saver but in a situation like this I would use a poly V belt and machine my own pulleys to suit the speed requirements....OZ.
Helixes aren't always downward spirals,sometimes they're screwed up

Offline Joe in Oz

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Re: Bench Drill to Tapping Machine.
« Reply #11 on: June 02, 2014, 06:53:49 AM »
Hi hanermo and Manxmodder,
thanks for the responses! All useful information!
My suggestion was based on my own use of toother (timing) belts and the commercial use of themin MUCH greater ratios than obviously recommended. In one application I have here the ratio is 10:1 using only 8 teet on the driving pulley with a much larger belt (can't recall the pitch but its size if that of a small car engine's timing belt. The little electric scooters you see around with 200W 24V motors also use toothed belts for their drive at very high ratios with a finer pitch. I've used those pulleys and belts - and motors - quite  bit (Having to machine much of the integral rear wheel off to use them for my purpose....).
XL pulleys and belts are available at much lower costs than your reference hanermo (e.g. http://www.ebay.co.uk/itm/190920642741 and http://www.ebay.co.uk/itm/331210061601).
Poly-V belts are an option that makes a lot of sense! I have not sued these myslef, but I have a very high speed drill press that currently runs on its last legs with a tiny flat belt which is no longer available easily. I might consider that when the time come comes. THe current pulleys ar thick enough in their periphery to trun them into poly-V pulleys. Thanks for that input!
Cheers,
Joe

Offline velocette

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Re: Bench Drill to Tapping Machine.
« Reply #12 on: June 02, 2014, 05:32:18 PM »
Hi
I will recommend "Poly Vee" belts instead of 'Vee Belts" on any workshop machines.
Having a Lathe, Mill Drill, Vertical Bandsaw, and Two Drill Presses on "Poly Vee" drives makes me more than a bit biased.
They are a lot less likely to slip even at low speed on the bandsaw drive from the 18 to 1 gearbox.
Eric